Astronomy Cast

What time is it? OK, fine, what time is it on the Moon? The Moon orbits the Earth, so it doesn’t fall into a specific time zone. Also, there’s lower gravity on the surface of the Moon, which changes the rate that clocks tick. Well… It’s time to introduce Lunar Time. 

Show Notes

• The Necessity for Lunar Timekeeping
• Challenges in Defining Lunar Time
  • Absence of Natural Time Zones
  • Gravitational Time Dilation
• Proposed Solutions:
  • Lunar Coordinated Time (LCT)
  • Synchronization with Earth Time
• Implications for Future Missions:
  • Navigation and Operations
  • Interoperability

Transcript

AstroCast-20250217

 Transcribed by TurboScribe.ai. Go Unlimited to remove this message.

[Fraser Cain]

AstronomyCast, Episode 744, Lunar Time. Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today.

With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey Pamela, how are you doing?

[Dr. Pamela Gay]

I am doing mostly well. I rebooted my computer and it lost its brain, which caused me to lose my brain, but I think all brains have now been gathered up.

[Fraser Cain]

I think the fact that we have been wrestling with audio, software, hardware, codecs, gain, normalization, leveling for the entire length of time of AstronomyCast is hilarious. And I don’t mean that it’s been funny, I mean it’s been enraging. We have, like, why is this a problem?

Why is this happening? Why, after 18 years, can you not have a microphone connected to a computer that the sound goes into the microphone and is recorded by the computer and it’s fine? Like, is that too much to ask?

It is. It is. So this is what we get.

And this is what you get, which is us having hardware, software, audio devices betray us. And you, the listener, together.

[Dr. Pamela Gay]

The thing that gets me at the most stupid level is they have now added rainbow LEDs to every single piece of technology, and they can get all those rainbow LEDs to sync with this, that, and the other thing to display brand colors, to display whatever the heck you want. Light, in terms of making things look rainbow of your choice, they got it. Lighting of green screens, hard.

Audio. Audio is impossible.

[Fraser Cain]

Impossible. Can’t be done. Anyone who’s going to try to do audio, you’re out of your mind.

It’s, it is just, there’s no way that anyone can record audio from a microphone onto a computer and have that be saved. Like that’s, that’s rocket science. Alright.

What time is it? Okay, fine. What time is it on the Moon?

The Moon orbits the Earth, so it doesn’t fall into a specific time zone. Also, there’s lower gravity on the surface of the Moon, which changes the rate the clocks tick. Well, it’s time to introduce Lunar Time.

And we will talk about it in a second, but it’s time for a break. And we’re back. Alright, so when did the, I guess, the international space exploration community realize that there is a problem with thinking about time on the Moon?

[Dr. Pamela Gay]

So there’s always been this, yeah, we need to worry about this. This concern going on, like even during the Apollo missions, they had insane amounts of updating of the clocks to make sure they could figure out how fast they were going in feet per second, to figure out where they were, to figure out all sorts of different things that you don’t realize require you to know when you are. And since we didn’t stay on the Moon, it didn’t stay a problem and it kind of fell by the wayside because there are a lot of problems in space science that need solutions and that one could just wait.

But in the early 2020s, as it became clear that a new Moon race was on, as it became clear we were and are going back, some of us, someday, some combination. It started with ESA being like, okay, we need to start defining this. We need to start figuring this out.

And so ESA started putting together working groups in 2023 and not to be outdone. In April of 2024, the White House put out a memo that is no longer available on the Internet. Gripe of the day.

[Fraser Cain]

That’s really helpful for doing research, background research on this. It’s fine, we’ll just go with what the Europeans say.

[Dr. Pamela Gay]

There are so many points of information that no longer can be found. But anyways, moving on to discuss the reality of the situation. So it was realized we need to define this.

And the White House in April of 2024 said, NASA, you do you, coordinate with whomever you need to coordinate with. And by 2026, we want a Lunar Coordinated Time. This is because everything gets gets abbreviated stupid.

It’s called Coordinated Lunar Time and it is abbreviated LTC, which is consistent with Coordinated Universal Time, which is UTC.

[Fraser Cain]

Okay, so we’ve got Lunar Coordinated Time. And what is the proposal for Lunar Coordinated Time? What what will it be?

[Dr. Pamela Gay]

Well, and this is where it gets, what is the problem that we have to solve is the starting point. So for instance, why is it that when astronauts go to the moon, they can’t just use Houston time, which is pretty much what the Apollo astronauts did. Why can’t we in general just sync our clocks with the clocks on Earth and move on with life?

And the problem’s relativity. So in the initial, what does this need to entail? They identified it has to have traceability back to UTC.

It has to have accuracy for navigation and science, and it has to be scalable beyond the Earth moon. And all of this means we need to define all the parts of the equations that cause time to speed up and slow down based on the size of the gravity well you’re in and how fast you’re moving.

[Fraser Cain]

Right.

[Dr. Pamela Gay]

And luckily, the moon’s motion is not the dominant factor. We can figure it out. It is getting thrown into the calculations.

It’s actually the difference in the mass between the moon and the Earth that creates the biggest problems that we have to be able to correct for. The Earth has a much bigger mass, which means that our aging is slower compared to people who are in orbit around us who are aging faster. Always think of the, um, I just forgot the name of the movie.

Oh, Interstellar. Yeah. Always, always think of Interstellar when you’re trying to remember who ages this.

[Fraser Cain]

Yeah, that’s true. That’s for me. That’s first principles is Interstellar.

Yes. Think back Interstellar. He spent a day near a supermassive black hole, and when he came away from the supermassive black hole, his daughter had experienced 40 years.

[Dr. Pamela Gay]

Yeah.

[Fraser Cain]

And so, um, and yeah, that clocks run more slowly near to higher gravity, gravitational wells.

[Dr. Pamela Gay]

And slower clocks means you age less. Faster clocks mean you age more just for people who need to get all of that straight in their head, which includes people like me.

[Fraser Cain]

Right. But the balance that you’re mentioning though, is it’s not just the fact that you are near a gravitational well, if you are farther away from the gravitational well, then the clocks are going to run more quickly for you. But then also there is the speed of your spacecraft relative to the person who is not.

And so you’ve got a spacecraft that it’s going and then it’s flipped in reverse.

[Dr. Pamela Gay]

Which the ISS has. So with the International Space Station, they’re going round and round at a zippy pace. And because they’re going at a zippy pace, they are aging slower than the people on the surface of the planet.

Here’s where you think of Ender’s Game.

[Fraser Cain]

Um, right.

[Dr. Pamela Gay]

I apparently do everything by movie reference.

[Fraser Cain]

No, I think that’s perfectly appropriate. And then in fact, there is a perfect balance point where the people who are in space, and I forget the altitude, but there’s a place where you will be the compared to a person on Earth, you’re experiencing less gravity. So your clock is clicking more quickly, but also you are moving faster.

And so your clock is clicking more slowly. And there is this perfect spot that you could be orbiting around the Earth and you wouldn’t experience any time drift with those two factors. But the point that I think, you know, back to what you’re saying, right?

That, that when you’re on the moon, the moon is going around the Earth. That when you’re orbiting around the moon, you were going at a certain velocity relative to the Earth. When you’re at a lunar halo orbit, you’re going a certain speed.

When you’re down on the surface of the planet, you’re experiencing different amounts of gravity and that the clocks are going to tick at a different time compared to a person on the surface of the Earth for every single one of those conditions.

[Dr. Pamela Gay]

Yeah. And, and this is where, uh, the white house in April of 2024 gave NASA until 2026 to figure this out.

[Fraser Cain]

Um, and you know what, I want to take a break before we figure out, like this is a cliffhanger. They were tasked to figure this out and what they discovered was, and we’ll be back in a second and we’re back. What did they figure out?

[Dr. Pamela Gay]

They figured out they being NIST, the national institutes for standards and technology figured out that it is when you do all the equations and you consider the orbital motion of the earth, the orbital motion of the moon. Um, it is the mass difference between the moon and the earth that dominates the difference in the equations of time between the two and not the speed, not the speed. It is not the speed that is the dominant factor.

And because of this, uh, there is, um, and here, I’m just going to read from a paper that came out in August of 2024, uh, from NIST, uh, the citations authors are Neil Ashby and Bunjanath Patla. Um, we estimate the rate of clocks on the moon using a locally freely falling reference frame, coincident with the center of mass of the earth moon system. A clock near the moon’s solenoid ticks faster than one near the earth’s geoid accumulating an extra 56.02 microseconds a day, which is a very, very, uh, fancy way of saying that at the surface of the moon compared to the surface of the earth, um, that, that clock is ticking faster. You are aging faster on the moon and it’s a small amount, but it’s amount that’s going to add up. And it’s an amount that if you don’t take it into account, once we start trying to develop a global positioning system for the moon, we won’t be able to do it. And the other thing is that as we start doing things like building telescopes on the moon and trying to coordinate data between lunar observations and earth based observations, if we don’t take into account this difference of 56.02 microseconds a day, our, our ability to align those, those data sets won’t be there. Um, so, so things that are affected, if you don’t take this into account, um, I mean, obviously pulsar timing, that’s super simple, uh, where things are is going to drift over time. If you don’t take it into account and you try using the exact same global positioning system, uh, equations that we use for our, not the equations are the same. If you start using the same values, uh, that we use for our earth system, um, it’s not going to work.

You’re going to have to update the chips that go in your phone and run the calculations to have the right constants. Um, one of the most amazing things that’s going to be totally different if you don’t take this into account is our ability to do interferometry at radio wavelengths. Cause right now we can have different radio observatories all over the world tied to their, their atomic clocks, taking observations with those timestamps inside the observations and using amazing computer systems.

We can shift the data around to align the incoming radio waves to create a radio dish. That’s the size of the earth. Now, when the radio waves are coming into the moon, we have to account for the difference in distance to the lunar dish and the earth dish.

That’s one thing that has to do in the process of aligning the data, but then we also have to either stretch or compress. And in this case, it turns out if, if time is, is going faster, you have to stretch the data out to get the time that’s passing to be the same for the data collected on the moon and the data collected on the earth. And that’s just wild to me to think about.

Time is going to affect things at that level.

[Fraser Cain]

Your hair again.

[Dr. Pamela Gay]

Okay. I’m looking for, I’m apparently going to use a booklet to hold back my hair. Perfect.

Rich, feel free to leave this in. So our audience knows what chaos is occurring when they get the audio file. I am very sorry, everyone.

I am going to have some housework done next week to seal the walls of my studio. And so I haven’t set my good mic back up after getting a computer, because I’m just going to have to move everything anyway. This is a high quality mic.

It’s just subject to long hair.

[Fraser Cain]

All right. We’re going to continue this conversation, but it is time for another break. And we’re back.

Um, right. So it’s, it’s kind of fascinating to think like the nitty gritty details. People are like, Oh, I want us to be living on Mars.

We want to be a, have a future solar system spanning civilization. But you can imagine somebody, you know, now detail has to show up and sort of join the conversation. And can you imagine taking that concept to the next level where you’re like, Oh, okay, what does it mean to be out at the L2 Lagrange point?

What does it mean to be on Mars on the surface of Mars in orbit around Mars on Phobos, uh, what time does Parker solar probe experience compared to the time that is experienced by us here on, on earth and that, that a future solar system spanning civilization, especially one that’s attempting to conduct science operations, trying to synchronize global positioning systems and communication systems to manage the time delays is going to just have a headache of the nth degree.

It’s mind bending. And, and yet you can see, yeah, if you don’t account for that, that time dilation, then you are not going to be able to align the measurements made by a interferometer that’s operating between the earth and the moon. You are not going to have an accurate timekeeping of when events happened so that you can make sure that the packets are arranged in the right way to put together a communication system.

Like all of these are actually going to be a big enough problem that the European space agency is assigning a group. NASA is assigning a group and they’re going to come together with some future global standards that then everybody, including the Chinese probably will have to work with. It’s, it’s a, it’s crazy.

It’s kind of humbling.

[Dr. Pamela Gay]

It’s not linear. I mean, this is the crazy thing because things are, are on elliptical orbits. The, the offset in time varies with time.

So you have to basically define, this is the moment at which clocks are synced. And now to figure out when this place is compared to when this place is, you have to take into account the overall offset due to mass, which is a standard. You have to, we assume the mass of the moon will remain constant.

It’s a good idea. But then you also have to take into account that yes, there is a subtle difference due to orbital speed that can mostly be ignored, but not completely be ignored. And the orbit’s an ellipse.

So the difference in the rate of time passage varies as a function of where you are in your orbit and the rate you’re going in your orbit. And, and this is something that you have to take into account for every world, for every different mass object. And you have to layer on the, I’m on Phobos, which means I’m in motion due to going around Mars, but I’m also in motion due to overall motion going around the sun.

And then you have to take into account the fact that when you’re looking at the signals, the time that it takes each successive wave getting to you is going to be different. So there’s a Doppler shifting of the signal. Now that doesn’t affect the rate of time that affects the rate of incoming information, but all of these things have to be taken into account as we send and receive information about the universe around us and about our world and the worlds we’re trying to communicate with.

In trying to define time, poor Aspie and Patla in their paper from NIST, they set out to look at not just how time passes on the moon, but they also considered the various Earth-moon Lagrange points as places we also need to take into consideration because this is where we’re looking to put things like the Lunar Gateway. This is where we’re looking to put communication satellites to communicate with the far side of the moon. All of these different places have different passages of time.

[Fraser Cain]

And it’s interesting, if you go back to that definition that you provided, it’s that you were assuming a soliton that is in orbit around the moon or a soliton. And that’s interesting because that’s very similar to the way the astronomical unit is described. Like the astronomical unit, the rough version is it’s the average distance from the sun to the earth.

But in fact, that isn’t accurate because the earth is pulling on the sun and that’s causing a wobble on the sun’s position. And so actually the distance from the sun to the earth changes, not only because the earth is following an elliptical path around the sun, but also the fact that the earth, the sun is wobbling at tens of centimeters per second, forward and backward, thanks to the gravitational pull of the earth. It is, you know, they’re both orbiting around the barycenter.

[Dr. Pamela Gay]

And Jupiter, Jupiter’s the dominant factor.

[Fraser Cain]

Yeah, no, for sure, for sure. But, and so when you measure an astronomical unit, you are imagining a soliton. If you’re measuring, you know, according, if you’re going to follow NIST or whatever, it’s a soliton orbiting the sun because that has no mass.

And that is, that is theoretically not pulling back and forth. On the sun. And, and so the reality is, is inaccurate by a certain wide margin, not just because of the movement of the earth, but also the, the movement the earth causes to the sun.

And so when you’re considering this, you know, they very specifically said, we’re going to consider a soliton because if we consider something that has mass, then that is going to affect the, the, you know, the positions of things and just make things even more complicated. And so, um, it’s, you know, a lot of the times we have these conversations on astronomy cast about things that are theoretically possible, but practically not relevant. Like, could we look backwards in time by looking at the light that was going around a black hole to see a time in the past?

Yeah. Theoretically photons are making the journey from the earth out to a black hole. They’re coming around the backside of the black hole and they’re making their way back to us theoretically, but practically no.

But in this case, time slices of time that are so small, um, are actually practical. Yeah. Having a practical implication to the way we will conduct our exploration to the point that like people could die if you get this time wrong.

[Dr. Pamela Gay]

Yeah.

[Fraser Cain]

And so we have to take into account, and yet it is mind bendingly complicated. Like, I don’t think anybody will ever go, Oh yeah, we lost 60 microseconds today. Like you do.

[Dr. Pamela Gay]

Well, and then you have to like consider the fact that we have stuff like leap seconds here on the surface of the earth.

[Fraser Cain]

Yeah.

[Dr. Pamela Gay]

And so when earth leap seconds, what do you do with the rest of the solar systems time? Because that leap second is aligning us with our world’s orbit and rotation relative to the sun and stars. Other worlds aren’t going to have those exact same needs for realignment.

And there’s stupid stuff that changes on the surface of our planet. Like when China put together their, what is it? Five gorges dam?

[Fraser Cain]

Three, three gorges dam.

[Dr. Pamela Gay]

Three gorges dam. Uh, that changed the rotation rate of our planet because the moment of inertia changed and we have to periodically upgrade.

[Fraser Cain]

The rotation of the earth is slowing down because the moon is moving away from us. And, and so, and I forget the exact number. I’m like, I’ve just noticed this and I’m sort of incorporating it, but it’s like on the order of tens of micro seconds per day per century is being caused by, by this slow, you know, the earth’s rate of turning is slowing down in a, in a rate that is measurable.

And I think you’re exactly right. You know, when you, when we deal with leap seconds or it’s this, you know, it was, it was fine and now it’s, now it’s not fine. Now we have to go back a whole second.

Does everybody across the solar system or do we switch to, there is no such thing as leap seconds. There’s no such thing as years anymore. You just accurately measure.

Yeah. Star dates. Yeah, exactly.

Is this star dates?

[Dr. Pamela Gay]

I think, I think it starts to become that.

[Fraser Cain]

Yeah.

[Dr. Pamela Gay]

We have Julian dates that we use in astronomy that go back to a set time and get calculated forward and it gets messy.

[Fraser Cain]

Um, so yeah, I mean, so what is the, I don’t know the, the way it works in Star Trek when, where does the star date originate?

[Dr. Pamela Gay]

I don’t, I don’t know. And, and I wonder, do you know this? I, I’m realizing.

So with earth, we have one moon that creates enough havoc for us and because it is moving away from us because it’s orbital rate around the earth is longer than the length of our day, it moves out. Now, Mars has two moons, one that has an orbital period shorter than its day and one that has an orbital period longer than its day, which one dominates. What’s its rotation doing?

[Fraser Cain]

I think it’s, I think Phobos is dominating. So it’s speeding up its rotation until Phobos is destroyed. Okay.

And then it’ll be Deimos that dominates and slows it back down again.

[Dr. Pamela Gay]

Yeah. So not our problem, at least.

[Fraser Cain]

No, no future Mars problem.

[Dr. Pamela Gay]

Yeah.

[Fraser Cain]

But yeah, yeah. It, it still just kind of blows my mind that, that our technology is so accurate. We deal with these wavelengths that are nanometers across.

Our technology is, is depending on this kind of stuff and we’re getting to this place in our, in our sort of world, our advancement, that these are issues that we have to take into consideration or things break, right? Ships go off course if you don’t take into account relativistic issues, you don’t take it, just time dilation into account for the GPS satellite systems. And now ships will go off or off track when they’re trying to go to the moon because we’re not getting the time right or we will.

Yeah. Yeah. And so you’re going to have a clock on board that is adjusting based on that.

And then you think about, say, um, uh, like the, the, you know, I am Legion, we are, we are Legion, I am Bob series where he has communications between different versions of Bob and they are moving at different rates of relative to the speed of light and they have to experience different amounts of time dilation as they try to talk to each other. And then they have ways of accounting for that, where, where one version will just wait around or do other things, waiting for the frames to come in for another version of himself. And, uh, you know, I guess it’s like, you know, nice problems to have that we’re so advanced that we now have to take into account relativistic effects when we attempt to communicate.

I think it’s great.

[Dr. Pamela Gay]

And this is where ultimately pulsars will form one of our most important coordinate systems. Uh, we’re going to rely on how time passes relative to those objects. And this is one of those things that the foundation series, which I need to go back and rewatch because I haven’t watched the second season yet.

Um, the foundation series really hits on this, looking at how time passes as you travel and how you measure your place.

[Fraser Cain]

Well, I think we should cover the, for Pulsar Timing as a feature episode and talk both about that, the Pulsar Timing Network as a, you know, as a gravitational, we talked about gravitational waves, but also as a potential way of timing, some interesting work on that. So that’s a future show.

[Dr. Pamela Gay]

Could be next week.

[Fraser Cain]

Maybe, sure. Thanks Pamela.

[Dr. Pamela Gay]

Thank you, Fraser. And thank you so much to our patrons who allow us to have a team that usually cleans up what we can do. Although I don’t think Rich is going to be able to correct what my hair did to this episode’s audio.

I am so sorry, everyone. Uh, this week in particular, we would like to thank Ellen Gross, Alex Cohen, Andrew Stevenson, Bebop Apocalypse, Brett Moorman, uh, Cammy Rassian, Daniel Loosley, Danny McGlitchie, David Gates, Disastrina, Dr. Woe, Dr. Jeff Collins, Ed, Elliott Walker, Father Prax, Frank Stewart, G. Caleb Sexton, Gerard Schweitzer, Gordon Dewis, uh, Gregory Singleton, Jarvis Earl, Jeff Huna Mortar, uh, Jeff Wilson, John Drake, Keith Murray, Kellyanne and David Parker, Kimberly Reich, uh, Christian Golding, Laura Kettleson, Lee Harbourn, Mark Phillips, Matthew Horstman, Matthias Hayden, Michael Perchata, Mike Dog, Nyla, Noah Albertson, Red Bar is watching, Share some Simeon Torfason, Ziggy Keemler, Stephen Veit, The big squish squash, The lonely sad person, Travis Sea Porco, Adam Anise Brown, Adam Moore, Arctic fox, Benjamin Mueller, Bob Zetski, Buz Parsec. I went into next week’s names. Some of you will get thanked twice. Thank you all so much for joining us and making what we do possible. 

[Fraser Cain]

Thanks everyone and we will see you next week. Goodbye. 

[Dr. Pamela Gay]

Astronomy Cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy Cast is released under a Creative Commons attribution license. So love it, share it and remix it.

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The post #744: Lunar Time appeared first on Astronomy Cast.

Just a few years ago LIGO detected the first direct evidence of gravitational waves coming from colliding black holes. And there you have it. Boom! Black holes collide! But that wasn’t all we learned from gravitational waves, nor will we learn. Sure, the masses of merging black holes are nice to know, but what else can we learn from gravitational black holes?

Show Notes

• Initial Discoveries and revisit to the groundbreaking detection of gravitational waves by LIGO
• Beyond black hole mergers including Neutron Star Mergers
• How gravitational wave detectors can observe other cosmic phenomena
• Multi-Messenger Astronomy
• Future Prospects including advanced detectors and space-based observatories
• Technical challenges in gravitational wave detection

Transcript

Frasier Cain [00:00:50] Astronomycast episode 743, what else can we learn from gravitational waves? Welcome to Astronomycast, a weekly facts -based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Sciences Institute and the director of CosmoQuest. Hey, Pamela, how are you doing? 

Pamela Gay [00:01:11] I’m in the United States, so it’s probably a question that you don’t want me to answer. I’m also a soft money funded scientist, so that is definitely a question you don’t want me to answer. 

Speaker 4 [00:01:21] Okay. 

Frasier Cain [00:01:21] Well, as a Canadian, now about to go into a trade war with you, my Canadian, sorry, my US friend, yeah, things are likewise bad. 

Pamela Gay [00:01:34] Yeah, yeah. The thing that has me most concerned is the rule of law apparently no longer has any meaning in this country. There are unvetted people without security clearances that now have access to the Social Security numbers and payment history of every US taxpayer. Yeah, yeah, these are kids that are going in and installing these servers and getting access and it’s just like, yeah. 

Frasier Cain [00:02:15] Anyway, just a few years ago, LIGO detected the first direct evidence of gravitational waves coming from colliding black holes. 

Speaker 3 [00:02:22] And there you have it. 

Frasier Cain [00:02:23] Boom, black holes collide. But that wasn’t all we learned from gravitational waves, nor will we learn. We’ll get to it in a second, but it is time for a break. 

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Frasier Cain [00:03:35] And we’re back. So before we get into what else can we learn about gravitational waves, can you give us like the short version of what we did learn about gravitational waves from colliding black holes? 

Pamela Gay [00:03:48] So what we learned was they politely do exactly what they were supposed to do. And it’s really, really good when observation and theory match, especially when they match pretty much perfectly. So what we were eventually able to figure out, thanks to a suite of really long tunnels on the planet Earth that had mirrors and detectors and lasers that allowed us to consistently measure within a wavelength, the length of that tunnel, within a wavelength of optical light, the length of that tunnel, what we learned is as predicted when large gravitational waves pass over and through our planet, our planet will expand and squish, expand and squish and squish in a way that has a decaying frequency and amplitude that matches theory for what should happen as two masses come together and then collide. 

Unidentified [00:04:55] Right. 

Frasier Cain [00:04:57] So, you know, this was the prediction. I mean, it goes all the way back to Einstein when he did his theories of general relativity and said that masses moving through space time that experience, what is it, a quadrupole moment should generate gravitational waves and that, you know, you had the whole LIGO group come together to try to see whether they could actually demonstrate this. Now we knew that gravitational waves, like they had already been proven thanks to binary pulsars. 

Speaker 4 [00:05:32] Right. 

Pamela Gay [00:05:33] So, so what had earlier been figured out by Holst and Taylor was when you have pulsars orbiting around each other, these are two high mass objects that are not symmetric and as they go around, they are radiating energy. And because the radiating energy in the form of gravitational waves, their orbits are coming closer and closer together. The period of the orbit is changing. We can measure that extremely precisely thanks to changes in the pulsar timing as the objects move to and fro and the distances, those pulses have to travel change over the course of the orbit. 

Speaker 3 [00:06:15] Right, right. 

Frasier Cain [00:06:16] And they were actually able to measure that, that the pulsars as they’re going around each other, they are bleeding off that rotational, the kinetic energy into gravitational waves, that’s slowing down their, how quickly they’re going around each other and you’re actually measuring those pulsar timings and it all syncs up. 

Pamela Gay [00:06:40] And they got a Nobel prize. 

Frasier Cain [00:06:41] And they got a, yeah, Nobel prizes all around. But, but then, you know, when they were directly observed as opposed to indirectly just by the way that the orbits are changing, again, Nobel prizes all around. And so I guess what did we learn apart from, yes, gravitational waves are a thing, what did we learn from that original LIGO detection of, of gravitational waves? 

Pamela Gay [00:07:07] Well, the one original detection was like, yay, merger. We did it. What we found from their, their population statistics is that group of intermediate mass black holes that we knew had to exist out there. And we hadn’t been able to, until recently to directly detect was finally detectable through the gravitational waves that were produced when they merged with other objects. We have also been able to see a neutron star mergers. And back in 2017, we had that, we’ve, I think, dedicated an entire episode to it, that, that event that we detected through the neutrinos, through the gravitational waves and through the light. And now we know the majority of gold comes from neutron star mergers. 

Frasier Cain [00:08:00] So, so I get, you know, I was going to take that to the, as the next part in this journey, but no problem. You’re just going to speed run today’s episode, which is perfectly fine by me. I can keep up. And that is that, yeah, we got this, this confirmation that the, that the black holes mergers are actually happening. And then that taught us that, that yes, indeed as predicted black holes get closer and closer to each other as they bleed off this kinetic energy through the gravitational waves. And that in fact, neutron stars can do the same. And this is detectable by LIGO when you’ve got these gravitational waves and then you’ve got, you know, we got a confirmation that a certain class of gamma ray bursts correspond to that merger of neutron stars that we see the wreckage of this collision. We see gold, we see other heavier elements that tells us that this is the way they probably formed and not necessarily with, with core collapse supernova. So then we get another finding just a couple of years ago with the nanograv facility about through pulsar timing arrays, we get another detection of gravitational waves. 

Pamela Gay [00:09:12] And here I want to separate very carefully two separate ideas. Individual pulsars should be sources of continuous gravitational waves. We do not have the technological ability to detect those right now. 

Frasier Cain [00:09:28] Only if they’re unbalanced though. 

Pamela Gay [00:09:31] Only if they’re asymmetric at some, some level. And we believe that they are asymmetric at some level. It doesn’t take a lot of asymmetry. 

Frasier Cain [00:09:39] So it is wobble. 

Speaker 4 [00:09:41] Yeah. 

Pamela Gay [00:09:41] So pulsars are theorized to be a source of continuous gravitational waves. That’s not what we’re talking about right now. What you’re talking about right now is we can measure the distance to pulsars through a variety of different means, and as long as that distance stays constant, the arrival of those pulses will stay constant. And this is more precise in timing than your standard atomic clock. What the nanograv facility has been doing is monitoring the pulsations of myriad different pulsars, looking for changes in arrival time that corresponds to a gravitational wave sweeping through our galaxy and changing the distance to these pulsars. And as you look out across space, we can see three -dimensionally all these different pulsars. We understand from all of the data we have so far that gravity appears to propagate at the speed of light. Gravitational waves appear to propagate at the speed of light. And we can, if we estimate the distance to this pulsar, we estimate to one back there, we look long enough and we haven’t been able to do this yet. We’ll be able to see pulsar delay here, pulsar delay there. That’s a wave moving through space. What we’re instead seeing is over here, there seems to be differences. We’re seeing a myriad of different delays that statistically appear to There are gravitational waves regularly sweeping through our galaxy. 

Frasier Cain [00:11:32] And a class of gravitational waves that we’re not able to detect directly, which are the results of the merges of supermassive black holes. 

Pamela Gay [00:11:40] And this is where it gets so cool to imagine all the different things we’re going to be able to detect someday. And I don’t know if you want to get to that right now, but nanograv is probing massive objects merging, LIGO is, is observing intermediate mass down to neutron star mass objects merging each different mass of black hole as it merges a neutron star as it merges produces a different frequency and amplitude of gravitational waves. And we can get at the distance of these events through the amplitude we observe and, and the frequency tells us what was happening. 

Speaker 4 [00:12:29] Right. 

Frasier Cain [00:12:31] So what’s interesting as well is, is Meerkat, which is this incredible South African radio telescope array recently confirmed the existence of this background gravitational wave to the universe in a fraction of the time that the original nanograph was able to do. And so you’ve got this independent confirmation, you know, more telescopes better, more, they looked at more pulsars for a shorter period of time and got the confirmation. So, so I think that’s where we stand today in, in what we have learned from gravitational waves so far. And so now we’re going to move on in a second and talk about what we can learn, but it is time for another break. 

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Frasier Cain [00:14:15] And we’re back. 

Speaker 3 [00:14:17] All right. 

Frasier Cain [00:14:17] So I think we’ve got a good sense of what we’ve learned so far about gravitational waves. And so now let’s look into the future, which is, I guess, what are the kinds of questions that we think that gravitational waves can give us some kind of answer and then how can we detect them? 

Pamela Gay [00:14:37] It’s not always what kind of questions can be answered so much as what parts of the universe can be probed. And one of the things you and I have talked about since day zero of, of doing astronomy cast is we cannot observe with light earlier than the release of the cosmic microwave background, but gravity doesn’t have that same issue. And in general, it’s not like we can go out and probe the gravity field of before the cosmic microwave background, the way we can probe the gravity field of a world and map out its sides. There’s no fly by of the big bang that any NASA probe’s ever going to do. But what we can do instead is look for the gravitational waves that are radiating from all directions from that early universe. And this could be part of this background of stochastic gravitational waves that we believe is out there. Now, the problem is there are a whole lot of different things that can produce gravitational waves. All it takes is an asymmetric object rotating and you’re going to start to get gravitational waves. A planet like Mars with a big old volcano on it is going to have gravitational waves, just not ones we can detect. 

Frasier Cain [00:16:06] When you drive down the road, you are generating gravitational waves. 

Speaker 4 [00:16:10] Yeah. 

Pamela Gay [00:16:10] And, and so all these different things add up. And, and so we talk about there being the individual gravitational waves that we get from merger events that we get from supernovae explosions, unless there is somehow this miraculously, perfectly symmetric supernovae. And, okay, I don’t know how that happens, but we’ll go with that. Anything rotating that isn’t perfectly symmetric is going to radiate gravitational waves continuously. So you have things that explode and merge do a burst of gravitational waves that we see. You have things that are rotating and are asymmetric that are giving off continuous gravitational waves. And there’s this random distribution we believe of gravitational waves that we may not ever be able to figure out what is. This is the stochastic gravitational waves in the background. And some of those are probably going to come from pre CMB, pre cosmic microwave background formation physics. Now, well, there’s going to be stuff we can never figure out. There’s going to also be stuff we do figure out. And this may be the one and only way we can ever get information from before the cosmic microwave background, other than by happening to see things that are fossilized in the cosmic microwave background. And we’re only going to get so far with that as well. So it’s, it’s cool to think we still have this one pathway to understanding the early universe. 

Frasier Cain [00:17:56] And what will be the sources of that gravitational wave? I mean, the term is primordial gravitational waves and, and as opposed to the background gravitational waves, they’re coming from the colliding supermassive black holes and us driving our cars down the road and so on, but there’s going to be this class of gravitational waves that will be visible, that would have been generated within that first 380 ,000 years after the big bang and in theory, right from the very beginning, right from, you know, if inflation happened, hopefully there’ll be evidence of, of that, those gravitational waves in, in, you know, coming from that inflation event, but even if there are, I mean, would there be like large masses merging and colliding early on in the universe? Like what would be that source of those first gravitational waves? 

Pamela Gay [00:18:43] So there were the very own acoustic waves traveling through the early material that made up our universe, that was creating a variety of overdensities and under densities in this essentially fluid that was the early universe. And so you didn’t so much have discrete objects that were merging in, in the early universe, but you did have changes in the mass distribution over time. And there’s other things that people worry about as well. Echoes essentially from colliding black holes and neutron stars that, that are out there today could be hiding stuff that I have to admit, I don’t fully understand a lot of the papers. I do know that we both chased the, the, uh, there was, what was it? 

Speaker 4 [00:19:44] 2014. 

Pamela Gay [00:19:45] Oh, the bicep two, the bicep two, where they thought they were able to detect the, the effects of gravitational waves in the data they were looking at, and they didn’t. And so we should be able to see in the cosmic microwave background, depending on what’s going on, a, a essentially bunching up of material changes and how the light is being radiated. And so far we haven’t been able to find that. So that leaves the next question of, can we find these ripples from how the material was clumped up and not clumped up in the early universe? Can we find the gravitational waves from that directly? And, and that’s the next thing that we’re hoping for. 

Frasier Cain [00:20:38] And I think that, you know, people are aware of the upcoming European space agencies, Lisa mission, the laser interferometer space antenna, and that’s going to be three spacecraft flying in formation, firing lasers back 

Speaker 3 [00:20:50] and forth. 

Frasier Cain [00:20:50] And then as gravitational waves sweep past, they will change the length of the arms and they’re like tens of thousands of kilometers long. And so it will change those and they will get direct evidence of those supermassive black holes merging. That’s the hope, but people have proposed versions of Lisa that have like maybe 12 spacecraft that maybe have longer arms and this is called the big bang explorer. And in theory, that that’s what gets you to those, those first gravitational waves, the ones, the echoes of the big bang itself. And hopefully that is, you know, is something that we will eventually see maybe in our, in our lifetimes. All right, we’re going to continue on this conversation, but it’s time for another break. 

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Frasier Cain [00:22:39] All right. So we’ve talked about the, the potential for primordial gravitational waves to give us a look into the time before the microwave background radiation. What else can we learn from gravitational waves? 

Pamela Gay [00:22:55] Oh man. So this is a conversation that Paul Matt Sutter is really the one. I’m just going to say any of you have the chance to ever talk to Paul Matt Sutter. He is the expert on this. 

Frasier Cain [00:23:06] This is watch his videos. 

Speaker 3 [00:23:07] Yeah. 

Speaker 4 [00:23:07] Or watch his podcast. 

Pamela Gay [00:23:08] Yeah. The dance videos, maybe not so much, but the podcasts for sure. Um, one of the things he talks about is how the early universe could have actually in essence fractured and, and these changes in the mass that look like fractures, if you were to try and draw them out, artistically could generate gravitational waves. He talks about how as the different forces split off from one another where first there was gravity and then there was the strong and the electromagnetic and weak. So strong went off and then the electroweak and the electromagnetic split apart. And as each of these things happened, the reality of our universe, and this is all happening in fractions of the first second, all of this could have potentially left a pattern through gravitational waves on the early universe. I don’t know how we detect that. 

Speaker 4 [00:24:12] I, I, 

Frasier Cain [00:24:13] but in theory it’s going to be giving off gravitational waves. 

Pamela Gay [00:24:15] Yeah, yeah. And so we’re at this point where things that I was always like, cool theory, dude, love it. We’ll teach it. Can’t observe it. I’m good with it though. We might actually be able to observe because there are people smarter than I am and more creative than I am. And I’m very grateful. Those people exist. 

Speaker 3 [00:24:37] Yeah. 

Frasier Cain [00:24:39] Um, okay. 

Speaker 3 [00:24:41] What else? 

Frasier Cain [00:24:42] I’ll give you, this was your title. So what else can we learn from gravitational waves? 

Pamela Gay [00:24:47] I, I got this idea from you. 

Speaker 3 [00:24:50] Um, okay. Wait, what? 

Frasier Cain [00:24:52] That was the title that couldn’t have been the title. 

Speaker 3 [00:24:54] I keep you. All right. 

Frasier Cain [00:24:55] Well, I’ll give you a couple more then. 

Speaker 3 [00:24:56] Fine. 

Frasier Cain [00:24:56] Uh, so one of the other ideas is that you had, um, cosmic strings that, that, you know, if they’re, you know, one of the theories about the sort of underlying nature of matter is that, that it’s made of these wiggly, jiggly strings. 

Pamela Gay [00:25:11] And that theory, I’m so much of a proponent. 

Frasier Cain [00:25:15] But if, and, and you can’t direct them directly, but if, uh, that theory is correct, then, then those, what would have been tiny strings at the beginning of the universe would have sort of accreted more material, grown larger and could be potentially light years across and these giant cosmic strings moving through the universe, colliding, um, and causing gravitational waves. And so one of the possible things that you could detect with gravitational wave observatories is, is colliding. 

Pamela Gay [00:25:48] Um, and over time we’re getting more and more evidence that those suckers don’t exist. 

Frasier Cain [00:25:52] Just, just to be clear, because you would see them with gravitational lensing as well. And these large scale surveys haven’t turned that up. So, uh, the other thing that I like is that we could use them to find aliens flying through space in their warp drives. That’s right. And so in theory, a spacecraft as it is, you know, as when the, when the enterprise goes from star to star, it’s going to be using the warp drive. And that’s going to be going to be shifting space time. It’s going to be bending space time to its will to be able to make this spacecraft go. And then in theory, that’s going to cause a wake, a gravitational wave wake, um, which is pretty cool. And so, but the sort of the coolest idea about this, and this was like a paper that just came out fairly recently was people were saying, Oh, we won’t necessarily be able to detect the wakes. That’s like, there’s not enough going on there. Um, but what we will be able to detect is the detonation, the catastrophic failure of the warp drives in these, uh, spacecraft. And so you’ll have the spacecraft is going, the warp drive collapses, destroys the spacecraft, sends out ripples of gravitational waves. And that might be just within reach of what we could do with, with gravitational waves, which I think is, uh, is fantastic. So, uh, you know, you’re wondering, and then the sort of last thing that’s on my sort of mental list right now is that we could potentially use gravitational waves as a communications tool. So, you know, this is beyond our capability today, obviously, but gravitational waves pass nicely through almost anything. They’ll pass through through planets. They’ll pass through stars. 

Pamela Gay [00:27:40] What don’t they pass through nicely? 

Speaker 3 [00:27:42] Uh, black holes. Yeah. 

Pamela Gay [00:27:44] I mean, they pass through them. 

Speaker 3 [00:27:47] So they’ll pass, they’ll pass. Yeah. 

Frasier Cain [00:27:49] They’ll pass around them. 

Pamela Gay [00:27:50] Yeah. 

Frasier Cain [00:27:51] Um, right. That a, that like when a gravitational wave passes a black hole, it will, any part of the gravitational wave that directly falls within the event horizon of the black hole gets added to the black hole. You convert the mass energy of the gravitational wave and you end up with, uh, additional mass in the black hole, but, but anything that, you know, but otherwise they get distorted. They get twisted as they go near the black hole. But in theory, if you could move a mass in a certain way, you could generate gravitational waves. You could modulate the gravitational waves. And if you have a detection system that is good enough, you could theoretically detect it. And it might very well be that, that some future advanced civilization could use these gravitational waves as a way to communicate. And in fact, that might be the best way to communicate. And so the reason we don’t see any evidence of aliens out there is because they’re all using gravitational waves to communicate with each other in some way that we haven’t figured out yet. So, um, so there’s a lot of like cool science fiction ideas on what you could use gravitational ways for. 

Pamela Gay [00:28:55] What I love about doing the show is I don’t generally keep up to date on all of the theoretical technology research going on, which is not my thing. Totally your thing. And, and so over the years, the show has totally become a collaboration because of all the interviews you’ve done with folks with NIAC funding, folks who are thinking out of the box with the technology for communications and thrust and everything else. Cause I would never have come up with those in any of the research that I was doing. I sort of hit the, uh, here are some papers. I don’t fully understand on primordial, uh, primordial gravitational waves. 

Frasier Cain [00:29:39] So that’s the other thing is searching, potentially finding primordial gravitational waves, sorry, primordial black holes. So that there is a minimum size of black hole that should be created naturally through the collapse of a massive star and that then if we detect the mergers of any black holes that are not mergers between neutron stars that are lower than the mass of that minimum mass level, then that immediately confirms the existence of these primordial black holes. Uh, one of the things that we haven’t seen so far is mergers between white dwarfs and neutron stars or white dwarfs. 

Pamela Gay [00:30:20] And the frequency is wrong. 

Frasier Cain [00:30:21] Well, but Lisa isn’t your tool. Lisa is the one that gets us the colliding supermass of black holes. There’s an extension to LIGO call. So there’s a couple of extensions to LIGO and a new thing called the Einstein telescope. And that will have, so right now LIGO has arms that are a few 10 kilometers, 15, I forget the length of the arms on like that. 

Speaker 3 [00:30:46] Yeah. 

Frasier Cain [00:30:46] But, but the Einstein telescope will be 40. And so it’ll be like the largest feasible gravitational wave observatory that you can put on earth. And what’s nice is that it just blends in with the rest of the existing, uh, community. So, um, 

Pamela Gay [00:31:01] did they change Lisa? Cause Lisa was originally billed as the white dwarf merger detector. 

Frasier Cain [00:31:08] I, I don’t, I don’t think so. I mean, maybe Lisa will also be able to do white dwarfs, but it’s the, it’s the longer, slower mergers that they’re going to go after. It’s these longer baseline ground observatories, but like, like the gravitational wave observatories are kind of like telescopes. You tune them to specific frequencies and then that’s what you’re 

Speaker 3 [00:31:28] looking for. 

Frasier Cain [00:31:29] But, but yeah. So in theory, we will get these confirmations that white dwarfs collide with, with black holes, that white dwarfs collide with 

Pamela Gay [00:31:35] neutral. 

Frasier Cain [00:31:35] Like obviously this is happening, but that’ll tell us which of the kinds of explosions that we see in the universe are matched with these kinds of mergers. So, uh, so it’s a lot of things, but as soon as you move mass, then you get to observe the gravitational ways of that 

Speaker 3 [00:31:51] thing. 

Frasier Cain [00:31:51] So, all right. We’ve reached the end of our show. Thank you, Pamela. 

Pamela Gay [00:31:55] Thank you, Fraser. And thank you everyone who is watching this video and apologies. I do not know why my camera decided it needed to, uh, completely lose its mind for a moment, but that is what it did. I mean, I understand. I think I’ve completely lost my mind for a moment, a few times over the weekend. Um, this week we would really like to thank, uh, some of our $10 or not patrons, uh, this week we would like to thank Alex Rayne, Andrew, Palestra, uh, Antasor, Astro Bob, Astro Sets, Benjamin Carrier, Benjamin Davies, Bill Smith, Bob Krell, Boogie Net, Brenda, Brian Kilby, Bruce Amazines, Manski, Claudia Mastriani, Cody Rose, David, David Rosetta, uh, Diane Philippon, Don Mundus, Frodo Tanenbe, I think I said that time, uh, Jeff, uh, McDonald Gold, Hal McKinney, Janelle, Jeremy Kerwin, Jim McGeehan, Jimmy Drake, Jordan Turner, Justin Proctor, Katie and Ulyssa, uh, Christian Magersholt, uh, Mark Schneider, Michael Purcell, Michael Regan, Nate Detweiler, Papa Hotdog, Rando, Robert Hundle, Robert Palasma, Ryan Amory, the Air Major, Thomas Gazetta, Timelord Irowe, Will Hamilton, William Andrews. Thank you all so very much. You make this show possible. 

Frasier Cain [00:33:29] Thanks everyone. And we will see you next week. 

Speaker 4 [00:33:31] Bye bye. 

Pamela Gay [00:33:38] Astronomycast is a joint product of Universe Today and the Planetary Science Institute. Astronomycast is released under a Creative Commons Attribution License. So love it, share it, and remix it. But please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, astronomycast .com. This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon .com slash astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomycast. 

Speaker 4 [00:34:36] Breastfeeding is natural, but that doesn’t mean it’s easy. That’s where the Lactation Network comes in, a network of highly credentialed lactation consultants who provide support at every step of your breastfeeding journey. With their expert guidance, you can prepare for your baby’s arrival, resolve breastfeeding issues, create a plan to wean or anything in between. The Lactation Network offers in person visits in all 50 states and is now in network with most major health plans. To see if you’re covered, visit tln .care today. 

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Frasier Cain [00:35:17] today. Restrictions apply. 

Live Recording

The post #743: What Else Can We Learn From Gravitational Waves? appeared first on Astronomy Cast.

Gravity Waves … not gravitational waves … move atmospheres and make pretty clouds.

Show Notes

• Introduction to Atmospheric Gravity Waves:
  • Definition and differentiation from gravitational waves.
  • Their occurrence due to a balance of buoyancy and gravity.
• Observations of Gravity Waves on Earth:
  • Descriptions of how these waves manifest in cloud formations.
  • Observation of gravity wave clouds in Florida and Illinois.
• Implications of Political Turbulence:
  • Brief discussion on how political changes in the U.S. could affect science communication and research collaborations.
• Gravity Waves Across the Solar System:
  • Mars: Observations from both ground and orbit, and their role in Martian atmospheric dynamics.
  • Pluto: Gravity waves observed in Pluto’s atmosphere, visualized in images from the New Horizons mission.
  • Venus: The massive waves driven by the planet’s fast-moving atmosphere as seen by Japan’s Akatsuki spacecraft.
• Mechanics Behind Gravity Waves:
  • Factors influencing gravity waves, such as smooth air layers and displacement triggers like mountains or temperature changes.
  • The role of these waves in the vertical and horizontal transport of atmospheric material.
• Unique Triggers for Gravity Waves:
  • Discussion on rare triggers like total solar eclipses causing gravity waves.
• Gravity Waves Beyond Earth:
  • Examples of gravity waves in the atmospheres of other planets like Jupiter, Titan, and Neptune.
• Spiral Arms of Galaxies:
  • An analogy to how spiral arms in galaxies are a form of gravity wave.
• Interesting Tidbits:
  • Gravity waves have been detected in a variety of contexts, extending our understanding of dynamic processes in planetary atmospheres.
  • Despite the complicated nature of these phenomena, they share common principles across different celestial environments.

Transcript

Fraser Cain [00:00:48] Astronomy Cast Episode 742, Atmospheric Gravity Waves. Welcome to Astronomy Cast, our weekly facts -based journey through the cosmos where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of the universe today. With me as always is Dr. Pamela Gay, Senior Scientist for the Planetary Science Institute and the Director of CosmoQuest. Hey, Pamela, how are you doing? 

Pamela Gay [00:01:10] I am doing well. I went from being very cold in Florida to not being very cold in Illinois. I think at some point, maybe I’ll be warm again, but wow, the winter this year is very determined to get its presence known. How are you up there in Canada? 

Fraser Cain [00:01:32] Great. We had been unseasonably warm. I could have grown citrus here warm. We didn’t dip below freezing for more than a couple of days, barely. Then a cold snap just came in, but still, it’s just barely below freezing. Apparently, next week we should get the polar mass is going to move our way and then we should get a little more seriously cold. Although Vancouver Island seriously cold is negative 6 Celsius. I don’t know what that is in the 20s, I guess. It’s not too bad. Nothing is cold as Florida or Louisiana where you see snow and stuff. I think it’s important for us to just warn people that both you as a running CosmoQuest and such and me as a Canadian are about to go through an enormous amount of turbulence with all of the stuff that’s going on politically in the US. 

Pamela Gay [00:02:38] We’re sorry. 

Fraser Cain [00:02:39] Yeah. For you, you’re having to deal with the repercussions for the people you can hire, the programs that you can apply for, all of the grants you’ve applied for are all getting reevaluated, shut down, closed off. I’m about to go into a trade war with you. We are now enemies, which is going to suck. I don’t know what the repercussions are going to be and what the implications are going to be for our ability to hire Americans, which I hire a bunch of Americans, so that may have to change our coverage. I don’t really know what the ramifications are. We’re going to see how this goes. I just want to warn everybody listening to this in advance that you could see disruptions in our programs, in what we do. It’s just going to be us attempting to navigate what is now a much more complicated and uncertain time in what we do. I’m sure what I’m explaining to you is a conversation that you’re having across all of your organizations and companies and nations and all of that as we chart this path forward. For all of us, I hope we’re able to make this uncomplicated and undisruptive as humanly possible so that people can just watch the shows they like and enjoy the science. They do their science and get work done as friends. 

Pamela Gay [00:04:15] All we want to do is communicate science. This shouldn’t be controversial. 

Fraser Cain [00:04:20] Yeah, exactly. Have you ever looked up into the sky and seen bizarre cloud formations that look like waves on the ocean? These are gravity waves, and not to be confused with gravitational waves. They’re caused by a balance of buoyancy and gravity. Of course, these have been seen across the solar system. We will talk about it in a second, but it is time for a break. I think I just won my taxes. 

Pamela Gay [00:04:46] Yeah. I just switched to H &R Block in about one minute. All I had to do was drag and drop last year’s return into H &R Block and bam, my information is automatically there. I don’t have to go digging around for all my old papers to switch? Nope. Sounds like we just leveled up our tax game. 

Fraser Cain [00:05:03] Switching to H &R Block is easy. Just drag and drop your last return. It’s better with Block. And we’re back. Do you have your classic favorite? Do you have times when you’ve seen 

Pamela Gay [00:05:19] gravity waves? I sure have. Yeah. We live in a very flat part of the United States, a very, disturbingly flat part of the United States. And because of that, we get these nice, stable air patterns that when something disrupts them, it will cause clouds to form in this set of stripes across the sky. And those stripey clouds are driven by gravity waves. And this entire episode is actually inspired by the fact that last Friday, it was finally sunny in Orlando, go figure. And I drove out to Cape Canaveral because I wanted to get some pictures of the new Blue Origin facilities. And there was this amazing set of contrails radiating away from a point on the horizon. And one of these contrails was perpendicularly by a bunch of gravity wave clouds. And it was just the wildest thing. And so I’m like, okay, let’s talk about this because clouds can get formed by so many different things. And gravity wave clouds are found throughout the solar system and probably throughout the universe. We just don’t have evidence of that. And they’re cool. 

Fraser Cain [00:06:43] Yeah. Yeah. And so like where I live, it’s the opposite of you. I live on the eastern side of Vancouver Island and we have a mountain range to the west of us. And so you’ll get these low cloud formations that will be passing over the mountains. And it’ll almost be like waves on the sea that you can see where the air mass is oscillating as it’s going up and down. And as it goes down lower, you get this condensation and then it goes up a little higher and then you don’t get any condensation and you get these just these weird clouds that roll. We see them all the time in certain times of the year when the conditions are right. In the springtime and in the fall, we get these big fluffy, what you would think are cumulonimbus clouds. They look like giant storm clouds, but they’re not. They don’t harken rain. But at other times of the year, yeah, we get these really weird cloud formations and it’s pretty cool. 

Pamela Gay [00:07:48] That is excellent. And that’s the thing about gravity wave clouds is they’re driven to expand on what you said with buoyancy versus gravity by having nice, smooth layers in the atmosphere. And then something comes along and displaces one of those layers and it sets up a harmonic oscillation. And that harmonic oscillation of something rising and falling, falling too far and rising back up, that harmonic oscillation is what can drive these clouds. And when you have a nice, calm set of layers that then hit the top of a mountain, in your case, are disrupted by a temperature variation or something like that in my area, whatever it is that drives that localized instability, it then expands out and causes all these amazing clouds that we then see. 

Fraser Cain [00:08:56] So what are the factors that will tell you whether or not you’re going to get this kind of an atmospheric effect? 

Pamela Gay [00:09:04] So you can’t generally find them directly under the jet stream. There is just way too much turbulence going on. You need to have smooth, stable layers. You’re not going to find them at where a front has just gone through where everything is turbulent. You’re not going to find it over an area with a lot of thermal instabilities. You need to start out from the position of nice, smooth air, the kind of conditions that you want if you’re out flying an airplane, something without turbulence. And then in these nice, smooth conditions, you need something that is going to cause a displacement in the atmosphere. So the air hitting a mountain will do it. 

Fraser Cain [00:09:52] Like a trigger mechanism. 

Pamela Gay [00:09:53] You need a trigger mechanism. My favorite trigger mechanism is something that was theorized for decades and wasn’t seen actually until just a few years ago. And this is total solar eclipse driven gravity waves. 

Fraser Cain [00:10:09] What? 

Pamela Gay [00:10:09] Yeah. Yeah. This is one of those things that you have to be able to just launch weather balloon after weather balloon after weather balloon starting a few hours before the solar eclipse, ending a few hours after preferably like 12 hours before 12 hours after. And gravity waves will already be forming off and on if the conditions are right. But when the conditions are right, having the shadow, which is a sudden change in temperature sweep through is going to cause a rapid density change in the atmosphere. And that density change is a triggering mechanism. So you have air that was nice and warm in sunlight, suddenly in shade, in getting lower density. That displacement will drive horizontally moving gravity waves that propagate in the direction that the solar eclipse is moving across the planet. 

Fraser Cain [00:11:12] It’s really cool. So, you know, you talked about how these can be seen on other worlds in the solar system. So where do we see these kinds of events across the solar system? 

Pamela Gay [00:11:29] The best picture I’ve seen captured of them is actually Pluto’s super, super thin atmosphere. So do you remember when we got those images that had the atmosphere not quite backlit, but kind of backlit? We could still see a crescent Pluto and there were these haze layers in the atmosphere. Those haze layers were caused by the propagation of gravity waves vertically through the atmosphere. 

Fraser Cain [00:12:05] I thought I had given you a softball and I thought you were going to talk about a different planet, but some images that I’ve seen, but absolutely. That’s great. I hadn’t even thought about those. 

Pamela Gay [00:12:18] That was a softball. I mean, it’s an amazing, stunning image. Pluto, yes, it has amazing topography, extremely high highs, extremely low lows, but its atmosphere doesn’t have a whole lot to displace it. And so it’s able to get these waves setting themselves up in the atmosphere. 

Fraser Cain [00:12:43] All right. We’re going to talk about this some more, but it’s time for another break. And we’re back. So the image that I was thinking of was some of the stuff we’ve seen on Mars. 

Pamela Gay [00:12:57] Okay. So Mars has all sorts of different gravity waves going on. They have spotted them in a variety of the different levels of the atmosphere. They have started to figure out that it’s gravity waves that are allowing effects from the lower atmosphere to propagate up to the upper atmosphere. There have been pictures from Curiosity of clouds with that distinctive set of troughs and peaks that are running parallel to each other for basically from everywhere you look out to the horizon. Gravity waves are just like another day in the Mars atmosphere. And it’s amazing that we know that the science here works on other worlds, but then Mars has just such a thin atmosphere that it’s amazing that we can see these effects in its clouds and we can. 

Fraser Cain [00:13:55] Sometimes I, you know, I mean, we are a video podcast because we record on YouTube, but it would be great to show people like images. So if you’re like in front of a computer, do a Google search for gravity waves Mars, and you’ll see just these incredible images of what really looked like ocean waves in the cloud structures on Mars. And as you said, you know, these have been observed from the ground from Curiosity, but they have absolutely been observed from above with varying orbital spacecraft. And so what role do we think that these gravity waves have in the sort of evolution of the Martian atmosphere? We know they can go from clear skies all around to global dust storms. 

Pamela Gay [00:14:46] So during the Martian winter, they’ve been able to catch these clouds forming directly above Curiosity. Very first winter, it was one of the things that Curiosity caught. We are now realizing this is how lower atmosphere material is able to get pushed up into the upper atmosphere. So one of the things we’ve been really struggling with is how is it that you can have dirt devils, dust devils, whatever you want to call them, and all these low level ground effects, then normal dust storms, and then shoot, there’s dust all the way to the top of the atmosphere. And we’re going to do a separate episode on just everything we now understand about dust storms because it is mighty. I think you actually know more about this than I do right now. So if you can give a summary, that would be amazing. We both read different things. 

Fraser Cain [00:15:52] Well, the paper that came out fairly recently was just them starting to understand what are the factors that come together to cause these global dust storms on Mars, because you’ll get regional dust storms, but there’s very weird conditions that end up with you getting this entire global dust storm. And this was the kind of event that killed opportunity. You know, although the wind doesn’t blow very hard, because it’s 1 % the density of the atmosphere, you get this decrease in the sunlight available to the solar panels. The rover was already almost out of electricity anyway, barely able to survive through the cold winter nights on Mars. And so this delivered the death blow as one of these global dust storms. And now it looks like people have done enough modeling of the dust storms on Mars that they’ve been able to realize that it is unseasonably warm conditions that lead to the, it gives you a higher likelihood of the global dust storm forming and going to the entire planet. And so now you can sort of see if you’ve got unseasonably warm temperatures, that’s more likely to lead to these regional dust storms linking up and eventually creating this planet wine storm. So it’s like, the way we described it in the universe today story was if the weather’s nice on Mars, panic, because it’s going to, you know, because the dust storm comes next. So there’s this situation on Mars where we have these diurnal tides. You get this change in the atmosphere between day and night. And then these tides interact with the atmospheric waves. And at different altitudes. 

Pamela Gay [00:17:43] And gravity waves in general are most common near the Martian poles. They can occur absolutely everywhere. Curiosity saw them straight above it. But in general, the conditions that are right, the nice stable atmosphere, something causing a trigger, those circumstances are most common along the poles. There’s an article in science about this. I’m going to do something I don’t think I’ve done before on astronomy cast and just read you guys a quote that I love about this. The Martian environment is the exotic wrapped in the familiar. The sunsets are blue, the dust doubles enormous, the snowfall more like diamond dust, and the clouds are thinner than what we see on the earth. And that is from a March 23rd updated article talking about gravity waves. It appears in the journal science. And these conditions are essentially allowing these super thin, all but transparent wispy clouds to have this undulating structure. And that is both you have the horizontal propagation, which is what we’re seeing in the clouds. There’s also vertical propagating gravity waves, which is how things are able to get through the different layers in the atmosphere. And so there’s a lot of complexity going on. And one of the unfortunate things is we don’t exactly have a fleet of weather balloons that we can release from the surface of Mars to study these things in the same kinds of details that we’re just starting to be able to do here on earth. But at least we can image them, even if we can’t directly measure the temperature pressure and humidity variations that are involved in them. 

Fraser Cain [00:19:47] All right, we’re going to talk about this some more, but it’s time for another break. 

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Fraser Cain [00:20:23] And we’re back. So we talked about Mars, we’ve talked about Pluto, we’ve talked about Earth, but there are more worlds with atmospheres in the solar system. So where do you want to go next? Venus, Jupiter, Titan? 

Pamela Gay [00:20:35] I was going to say Venus. So Venus has the biggest waves. The clouds are moving at 100 meters per second. 

Fraser Cain [00:20:54] Right. Like it’s important for people to understand it takes four days for the air on Venus, the atmosphere on Venus to rotate once while it takes for the sun to come back to the same spot in the sky. It’s 225 days. It’s like 247 days for Venus to turn once on its axis. But the air turns, the weather turns every four days. 

Pamela Gay [00:21:17] 100 meters per second is a kilometer every 10 seconds. That is just like mind -boggling to me. And we can see in images from Japan’s… You’re going to correct my pronunciation. Thank you. Thank you. I didn’t have to say it badly. You just said it. Japan’s Akatsuki spacecraft. Planet C. I’m going to go with Planet C. I can say that. Has been able to pick up these sets of waves that are taking up roughly a third of the planet’s hemisphere that we can see at any given moment or the spacecraft can see at any given moment. And these waves that are taking place in the clouds where you have these winds at tremendous speeds, the waves are stationary. And this is the kind of thing that causes me to think I chose the easier field going into astronomy as compared to meteorology. 

Fraser Cain [00:22:30] Right. Was that, sorry, was that like a direction you were thinking of going? 

Pamela Gay [00:22:36] No, never. But usually you’re like, I’m an astronomer. I went the hard path. No, compared to meteorology. And no one ever says, this is not rocket science. This is not brain surgery. This is not meteorology. Meteorology is the hardest of all of these folks. So in trying to figure out what’s going on as near as they can tell, the weather patterns going over mountains or as probably it was big old volcano on the surface of Venus was able to trigger an upward propagating gravity wave that created standing waves in the atmosphere. So we are seeing a super complex situation. 

Fraser Cain [00:23:32] Yeah, you’ve got these winds whipping around Venus every four days, 100 meters per second. You’ve got what looks like a mountain range in the Ishtar -Terra region of Venus. Yeah. And so as the winds are whipping around, you’re getting this oscillation that gets kicked in and it is a permanent standing wave. And so you think about places, there’s this amazing river in Germany that we saw where the water was sort of going down this sluice gate and it was the standing wave. This was in Munich, yeah? In Munich, yeah. People surf it. Yeah, exactly. I was going to mention the 

Pamela Gay [00:24:11] exact same thing. What city was it? Yeah, it was in Munich. That’s right. 

Fraser Cain [00:24:15] Right by the Science and Technology Museum. Yes. So people were surfing in this. It’s a standing wave. And so you’ve got this standing wave, this standing gravity wave in the atmosphere of Venus. And it really, again, I wish we could show you pictures, but it looks like someone has kind of wrinkled up a side of Venus to create this standing wave. 

Pamela Gay [00:24:39] And it’s that exact same scenario of you have an extremely fast moving fluid. We model atmospheres as fluids. It hits a disrupting surface, the mountain on Venus, the sluice gate under the bridge in Munich. And that disruption creates a wave form that appears stationary, although the molecules that are in it, the fluid is constantly moving. The shape of the fluid is unchanging. And it’s this fabulous combination that on Earth is caused by all the features of the geometry of the water. But on Venus, it’s a gravity wave. It’s a buoyancy versus gravity versus landscape issue. And it’s just amazing. 

Fraser Cain [00:25:38] We can rattle off other examples of ones that are seen on Jupiter, on Titan, Saturn, Neptune. Neptune has the fastest winds in the solar system. So these exist across the solar system. But I want to kind of blow people’s minds. And that is something that doesn’t have anything to do with atmospheres, but also has something to do with gravity waves. And that is the spiral arms of galaxies. 

Pamela Gay [00:26:01] Oh, I wasn’t planning to go there. But yes, that’s exactly what they are. 

Fraser Cain [00:26:06] Right. Yeah. Yeah. So when you look at galaxies and you see the spiral arms, you are looking at gravity waves, standing waves. They are not that the stars themselves are turning around in the galaxy in the shape of that wave. It is this wave of material that is propagating through the galaxy. 

Pamela Gay [00:26:28] And it’s disrupting the motions. So the way to think about it, I’m, as always, looking for things to use to talk with my hands. Okay, we’re going to pretend that this pencil case is a fragment of the arm. Sorry, all of you who are listening, a fragment of the arm of the Milky Way. As a star is orbiting along, it has a nice, smooth, stable motion. But as it gets closer and closer to that arm, the gravity of the excess material within the arm will accelerate that star toward the arm. And as the star is trying to come out the other side of the arm on its continual flow, on its continual orbital motion about the Milky Way, the excess mass inside that arm slows it down. So essentially its motion is disrupted by the gravity of the arm. So it gets accelerated in. It lingers in the arm because gravity is not letting it escape. And then it gets out and it continues its smooth motion. And so this kind of disruptive behavior of gravity waves is something we see over and over and over again. 

Fraser Cain [00:27:52] All right. Thanks, Pamela. 

Pamela Gay [00:27:54] Thank you, Fraser. And thank you, everyone out there. Hugh, right now, your patronage means more than ever before because we’re able to communicate science in this difficult world without having to worry about it because of you. This week, I would like to thank Abraham Cottrell, Alexis, Bore Enthro Lovesvall, Bart Flaherty, Bresnik, Brian Kegel, Bury Gowan, Daniel Donaldson, Dwight Ilk, Felix Gutt, Galactic President, Superstar McScoopsalot, Georgie Ivanov, Greg Davis, Greg Vield, J. Alex Anderson, Jean -Baptiste Le Matenet, Joanne Mulvey, Jonathan Poe, JP Sullivan, Just Me and the Cat, Kim Barron, Larry Dotz, Les Howard, Lou Zealand, Marco Iorossi, Matt Rueker, MHW 1961, Super Symmetrical, Mike Heisey, Paul D. Disney, Paul Esposito, Pauline Medelink, Peter, Philip Walker, Planetar, Rando, RJ Basque, Robert Cordova, Ruben McCarthy, Scone, Sergey Manilov, Simon Parton, Steven Miller, Tim Garrish, and Zero Chill. Thank you all so much for being here, for letting me mispronounce your names, and we will see you next week. Thanks, everyone. See you next week. Astronomycast is a joint product of Universe Today and the Planetary Science Institute. Astronomycast is released under a Creative Commons Attribution license. So love it, share it, and remix it. But please, credit it to our hosts, Fraser Cain and Dr. Pamela on our website, astronomycast .com. This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon .com slash astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomycast. 

Live Recording

The post #742: Atmospheric Gravity Waves appeared first on Astronomy Cast.

Pollution will ultimately give away a society. And this episodes will shows us the potential indicators of advanced extraterrestrial civilizations. Also the various ways such civilizations might unintentionally or intentionally reveal their presence through technological changes in their environment. This episode delves into concepts like Dyson spheres, infrared excess, and unique transit signatures.

Show Notes

• Introduction to Technosignatures
• Dr. Pamela Gay shares her recent experiences in Orlando
• Technosignature Conferences
• Detecting Technosignatures
• Extraterrestrial Communication and Detection
• Technological Impact on Detection:
• Science Fiction Possibilities:

Transcript

Human transcription provided by GMR Transcription

Fraser Cain [00:00:50] Astronomycast, episode 741, Technosignatures. Welcome to Astronomycast, our weekly facts -based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how are you doing and where are you? 

Pamela Gay [00:01:11] I am in a hotel room in Orlando, Florida. I got to see the Firefly aerospace and ice face landers, hopeful landers, take off on a Falcon 9 last week. I had planned to go see the new Glenn launch, but I had a moment of fail. They sent out an email saying that they weren’t going to have a media site set up and it was cold and it was gross and I was like, oh, it’s not going to actually launch tonight. I decided to stay warm, wrapped up in a blanket, and it did actually launch. 

Fraser Cain [00:01:51] At some point, you’re hearing the building shaking, you’re like, oh no, there it goes. 

Pamela Gay [00:01:57] I have to say that as a single female traveling alone, I would not have been comfortable trying to find someplace to watch a 1 a .m. launch in an area I’m not familiar with. So I made the right choice, but yeah, it’s been amazing and I’m going to go meet with a bunch of collaborators and folks out on the Space Coast this week. And Blue Origin has a huge facility that was not here at all when you and I were out here for the Osiris -Rex launch a gazillion years ago. I just want to take photos of how big and branded with feathers their facility is. 

Fraser Cain [00:02:50] Yeah, and hopefully you can get more. They did have a facility, but we just drove past it in the bus and we couldn’t see what was going on. But hopefully you can actually get in behind the scenes and do some tours. That would be amazing. Yeah, I’m hoping as humanity develops more advanced technology, we’re having a larger effect on our environment. The more we do, the more we could be detectable. And this gives us ideas on how we could detect other civilizations, even if they don’t realize we’re watching and we will talk about it in a second. 

Pamela Gay [00:03:20] But it’s time for a break and we’re back. 

Fraser Cain [00:03:27] So there’s a document that is rolling around out there that I’ve really been wanting to try and get my hands on about this idea of technosignatures. So NASA now does this like a conference once a year, every couple of years, where all of the top SETI technosignature researchers come together and brainstorm ideas. And it’s Jason Wright, David Kipping, and Seth Shostak, and all Grinspoon. All of these luminaries in the SETI, METI, WETI space, as well as more traditional exoplanetary researchers. And apparently there’s a list of 39 technosignatures, 39 brainstormed ideas so far of different ways that an advanced civilization could be giving off some signal of its existence. And we’ve tackled the sort of, they’re sending a message at us with radio waves or in invisible light or something, but that’s just like one or two of those potential technosignatures. When you consider the sort of broader idea of all of the different ways that a civilization could leak its existence, it’s kind of mind blowing. And some of the ideas are extremely, extremely cool and sort of very creative and out of the box ways of thinking about this. So, so like, what is a technosignature? 

Pamela Gay [00:04:55] It is a signature to lame definition is lame, that says there is a technology here that is influencing the light being emitted, the spectrum of absorption lines in light that is being reflected or absorbed or otherwise a phenomenon that can only be explained through leaked or influenced signatures created by technology, which is basically a fancy way of saying that if you have a Dyson sphere, you’re going to have excess IR radiation. If you have a whole lot of pollution from chemistry, industry processes, you’re going to have absorption lines that can only be explained by technology. And these are all unintended consequences of a civilization that can 

Fraser Cain [00:06:01] be detected at distance. And like, and the list goes on and from, you know, warp drive signatures as they’re moving us being caught in the stray beam of a powerful radio pulse. If, while, while a civilization is trying to communicate with another gravitational waves being used to communicate through space, as you said, you know, some of the unintended ones, like they’re in the midst of having a nuclear war and we’re detecting the gamma radiation happening on the surface of their planet as they’re bombing one another industrial pollution. Um, uh, like the list goes on. And what I love about this is that many of these are unambiguous. Yes. So while biosignatures are very ambiguous, you know, we, we still argue about whether or not there’s, there’s phosphine in the atmosphere of Venus and whether or not even phosphine is a biosignature or methane or carbon monoxide or dimethyl sulfate and all these ideas, you see, uh, a Dyson, a partially completed Dyson sphere or a, uh, a transit transiting exoplanet that is in the shape of a triangle, you know, there’s something weird going on here. That is not what the universe would naturally cook up. So can you give me some examples of indirect techno signatures? 

Pamela Gay [00:07:26] Indirect techno signatures. 

Fraser Cain [00:07:28] So, so the director, the ones where they’re intending on communicating with intending is letting know that the indirect are the ones where, where we’re just being, you know, we’re just being curious and we’re just snooping on their, on their existence. 

Pamela Gay [00:07:40] So my, my favorite and I already hinted at it is the infrared excess from systems that have massive structures in them. These are the Dyson spheres, the rings like Larry Niven imagined with his ring world books. And there are a number of catalogs out there of, uh, all the detailed, uh, photometry of stars across many different wavelengths. And people are actively looking to see, can we find worlds with infrared access and then following up to rule out things like dust and all the normal stuff that might be able to cause infrared signatures like that. And there’s a whole list of them being followed up so far. And of course, none of them have yet proven themselves to be beyond a shadow of it out, be a Dyson sphere, but Tabby’s star gave us one heck of a wild ride. Uh, more than a decade ago, uh, the planet hunters project, a citizen science project to go through the Kepler data and look at the light curves of stars to see if there were planets that had otherwise just not been noticed by the software. And one of the stars that got flagged and was, uh, then sent to Tabitha. And I’m going to say her last name wrong. I am so sorry. She said it to me multiple times and it never sticks. 

Fraser Cain [00:09:18] Tabitha Boyudjian, thank you. 

Pamela Gay [00:09:21] He knows how to say it. Um, Tabitha Boyudjian, I, she is a graduate student took on this star and was trying to figure it out and ended up doing a crowd funding campaign to afford her telescope time. And ultimately it turned out to be like your normal swarm of naturally occurring objects in that solar system, but it really looked like it could be something under construction. It was amazing and showed us that we can get super excited about the possibility of life around another star and the world does not get excited with us, so I have a feeling that when we do finally find life, no one’s going to pay attention to us. 

Fraser Cain [00:10:07] And, you know, we know that there are, you know, this can work at various scales at the, at the smallest scale, you know, we are, as human beings, we are producing excess waste heat. We’ve, we’ve started to increase the temperature on the planet through global warming, you know, emissions, but, but just direct, even we make them, if we make the most efficient, energy neutral, sort of technological civilization, we will still produce waste heat and that waste heap will increase over time. And people have done calculations that within a thousand years or something, we will start cooking the planet purely by the waste heat from us having an economy, like it’s all green energy, but yet it’s still producing so much waste. And you can imagine at a planetary level, you’re going to see the waste heat coming from the planet, but you can also imagine at a, like at a stellar level, as you said, you know, if you’ve, you’re starting to enclose your star in this, in this, you know, collection of satellites, you’re starting to shift the, from visible light into the infrared in a way that’s very weird and bizarre, but you can take that even to the where you have enclosed every single star in your entire galaxy and you’re creating a galaxy that it’s an infrared signature. And in fact, have been, yeah. And astronomers have done surveys for these strange point like objects that are putting out too much in the infrared and not in other wavelengths of radiation and identified like, I think six 

Pamela Gay [00:11:41] candidates later last year, there was a, yeah, there were six new the total list is around 30 objects. And what’s cool is they’re using machine learning algorithms and machine learning is where you train something to identify and annotate sources. It’s not generative. It’s not large language models. Machine learning is annotating things so that human beings don’t have to go through these catalogs. And with every new, uh, listing coming out of Gaia, it’s going through and having more sources get identified by these algorithms and eventually it’s either going to hit the point of awkward that we aren’t finding any, or we’re going to find something to follow up on. I hadn’t known about the galaxy idea though. And now I’m like, Oh, so when we find these dark matter dominated galaxies, we need to give them a triple look to make sure that it isn’t just like an overly zealous Dyson sphere creating civilization. And that’s not something I’d thought of before. 

Fraser Cain [00:12:51] Well, and the other thing is kind of interesting is there’s all these amazing ideas about moving stars as I do scat off thrusters where you could, you know, you, you have this giant mirror that you build that was on one side of the star and then the radiation from the star pushes the mirror away from the star, but then the gravity from the mirror pulls at the star and the star actually then pulls itself around in whatever direction you orient the mirror. And you can move incredibly quickly. You can end up moving, uh, like to 25 % the speed of light. You can be moving your star at 25 % the speed of light after a million years of using this thruster. And so you can over reasonable amounts of time, definitely less than a billion years, you can completely rearrange all of the stars in your galaxy to a more pleasing shape. And so you, again, you can look out into the universe and you can look for galaxies, you know, spiral, spiral, spiral, dodecahedron. Wait, what, you know, where someone has gone, what is the best structure for a galaxy? And they can have moved that entire galaxy. And, you know, I’ve seen some really cool simulations where you end up with like a super massive black hole with like a billion times the mass of the sun that’s surrounded by a collection of supermassive black holes, each of which has, uh, 10 million times the mass of the sun. And then each of those is surrounded by black holes. And then those are surrounded by stars and then those, and you could have a million terrestrial planets in one system where you could communicate within a couple of light days to every single planet within your entire million planet system. And it’s like, obviously boggles the imagination, but we just look for weird things that people have constructed out in the universe. All right, we’re going to continue having this conversation, but it’s time for another break. 

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Speaker 3 [00:16:47] And we’re back. 

Fraser Cain [00:16:48] So that’s one example where we’re sort of seeing them at a really incredible level, but I think another thing that’s really important to talk about is just like we could see transits of things that give off a strange signature. 

Pamela Gay [00:17:06] Yes, and this can take many different forms and we’re getting to the point that we’re starting to be able, we think, to detect moons within transits where what’s happening is when you round object pass in front of a, we’re going to pretend my iPad is round and looking to see what I’m advertising. Okay. Um, as that round object passes in front, it’s, it’s roundness causes the light to go down a little bit down, down, down, down flat. And then as it comes out the other side, it has a characteristic, the way it goes down flat and the way it goes up that can, I mean, it can be caused in different ways, but the simplest way to cause it is by having a round object pass in front of the star. Now, if instead you have that triangle that you had mentioned earlier as, as it goes in, especially if you have something, I have nothing triangle shaped in my area. I’m going to grab apparently my track pad. So if you imagine, uh, we’re going to call this a triangle as it passes in front, that’s not going to cause a different shape of dip. And if it has the flat edge going in front first, that is a wildly different shape. So by how the shape passes in front of the star, you’re going to end up with different kinds of shapes to how it gets down to that flat point at the bottom of the eclipse. And we only know how to explain round things and things that would be like two round things next to each other. We can explain that and nothing else. And where you can’t explain it, that’s where you start blaming civilizations that built really big stuff. 

Speaker 3 [00:19:15] Yeah. 

Fraser Cain [00:19:16] And someone did the math and found that, that that’s the most efficient way to communicate your existence to the universe that attempting to broadcast with radio waves or attempting to, um, you know, send a tight beam radio or a blazer at some other star system on a regular basis uses up a lot of energy on an ongoing basis, but if you could build a giant Mylar sheet, uh, or cloud of satellites and organize them into a specific shape, and then you just let orbital momentum, keep them going around your star system for literally ever, um, and then you are now broadcasting to the entire universe. You know, it’s just civilization here, right? Whether that’s a good idea or a bad idea, who knows, but, but you can imagine some civilization making that investment and saying, you know, let’s put out our for sale sign or put out our, our, uh, open to chat sign, um, to the universe and then you just put up this thing and it just goes around. And every time someone looks at the star system, the, where they’re lined up, they see this triangle. They’re like, okay, there are people there. 

Pamela Gay [00:20:23] And there’s subtleties in this that, that are the things that I really am fascinated about. So we know we’re eventually going to need to have communication satellites that allow us to talk to anyone, anything that we want to communicate with on Mars when Mars is on the far side of the sun with us. And so the way to do this is to start putting equally spaced spacecraft around the orbit so that they can beam information to each other, to get it to us. Now, imagine having massive space stations, evenly spaced in their orbits where they’re all in the same orbit and you keep seeing dip in light and you can see how fast something’s moving in its orbit by how long it takes it to pass in front of the disk of that star. But then it keeps happening such that you can’t explain the dips and the crossing time by a single object. Once you start figuring out, Oh, that’s five exactly evenly spaced objects, that’s, that’s not something that the universe put there on its own. And that’s where it starts to get Isaac Asimov futures written in eclipses. 

Fraser Cain [00:21:46] And kind of related to that, people have proposed that you, like when planets are transiting and especially when you have multiple planets transiting at the same time, it’s the perfect opportunity to watch that star system, you know, think about the TRAPPIST -1 system too. You know, the planets are all lined up from our perspective. And so we see them as they pass in front of the star. But if we watch and see two of the planets passing in front of the star at the same time, then one planet might be attempting to communicate with the other planet and they’re going to send a radio pulse or a laser pulse at the other planet. And we could get caught in the crossfire. So we would detect the leaked signals when one planet was communicating with the other planet in this direct way. And so astronomers have proposed that we direct our radio telescopes at TRAPPIST in those moments where you’ve got those alignments in front of the star. All right, we’re going to talk about some more ideas, but it’s time for another break. 

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Fraser Cain [00:24:17] So I want to talk about some of the stuff that like we’re doing to our atmosphere that perhaps other civilizations would be able to detect and how they might be able to do it. 

Pamela Gay [00:24:28] Well, there there’s things that don’t belong in our atmosphere that luckily are decreasing an amount like 

Fraser Cain [00:24:34] chlorofluorocarbons. 

Pamela Gay [00:24:36] Those are complex molecules. Those of you who grew up in the eighties remember a hair spray suddenly went from being the stuff that you could use to create flame throwers. If you were an appropriately minded middle schooler to being like these very boring squirt bottles. And the reason that all of our Aquanet suddenly changed was the decision to try and prevent more chlorofluorocarbons from getting into our atmosphere unless we absolutely had to 

Fraser Cain [00:25:11] have them. 

Pamela Gay [00:25:11] There was similar attempts to change out air conditioning, cooling fluids, and that’s an ongoing process as houses get their systems changed as old cars get their systems 

Fraser Cain [00:25:26] changed. 

Pamela Gay [00:25:27] But there’s going to be a large swath of time in Earth’s history where our atmosphere had all these chlorofluorocarbons that can be with high enough resolution spectroscopy detected in how the sun’s light gets changed as it passes through the Earth’s atmosphere and then detected by whoever is out on just the correct line through the 

Speaker 3 [00:25:52] sky. 

Fraser Cain [00:25:53] And there are papers out there right now that where people have done the calculations based on how much time it would take for James Webb to be able to detect chlorofluorocarbons in the atmosphere of an exoplanet, say at the TRAPPIST -1 system. 

Speaker 3 [00:26:06] And it’s not a lot. 

Fraser Cain [00:26:08] Like it is within the capability of James Webb and it’s absolutely within the capability of the next generation telescopes like the Hubble World Observatory and so on to be able to make those kinds of detections out to hundreds of light years away. It’s such a strong chemical in the atmosphere, gives off a very unique signal and there is no natural way that you could produce that chemical. It has to be a technosignature. 

Pamela Gay [00:26:36] And there’s a whole suite of different molecules that as far as we know can’t be produced another way. Now, as you pointed out, people periodically try and come up with ways to explain molecules that we believe are related to life in one way or another and blame geology, but things like chlorofluorocarbons, we just can’t get there from here. 

Fraser Cain [00:27:01] And so we are, over time as we develop new chemicals and we put them into our atmosphere for good or for evil, those will be detectable by other civilizations. We’re like, oh, I remember the time when we thought it was a good idea to pump that chemical into the atmosphere to try and prevent climate change, right? We can watch them doing it. But then the other thing is that we are putting out electromagnetic radiation and there’s this classic, was it 

Speaker 3 [00:27:34] contact? Yes. 

Fraser Cain [00:27:36] Cause, contact where the movie starts with this sort of increasing bubble of radio waves that are moving away from the earth where, where you get, you know, different television shows at different times, because we’ve been broadcasting radio waves out into the universe for a hundred years. 

Pamela Gay [00:27:53] And it’s not coherent enough that, unless they know exactly what they’re looking for as they try and deconvolve all the signals from all the different stations, they’re not going to be watching I Love Lucy. They might be watching the first Olympic broadcast cause there really wasn’t anything it was competing with, but we’re sending out radio signals that can’t be explained naturally. And it’s just a mass of, of changes across all these different wavelengths that basically screams something here is using this technology. And over time we’re going to probably see the system change where we’re already starting to realize that if we want to get much higher bandwidth transit transmissions between earth and Mars, I’m just going to keep using Mars as an example. We’re going to want to start using laser transmissions and that is much more point to point. But to use your Trappist example, when those two worlds are lined up just right, that beam broadens and what isn’t eclipsed by the planet you’re transmitting to is going to go out to potentially be observed by other places in our galaxy, probably not beyond just because resolution is a thing, but we’re polluters in all sorts of different ways. And that’s how we’re going to get found. 

Speaker 3 [00:29:31] Yes. 

Fraser Cain [00:29:32] And like right now we couldn’t detect ourselves. We don’t have the telescopes to be able to detect our brightest radio emissions, the ones that are being sent out in all directions, but we have a telescope that’s coming, the Square Kilometer Array, which will be operational in the early 2030s. And that someone had told me that it would be capable of detecting the air traffic control system from earth from a hundred light years away. 

Pamela Gay [00:29:59] Which is just amazing to imagine. 

Speaker 3 [00:30:02] Yeah. Yeah. 

Fraser Cain [00:30:03] So, you know, it will, it could be your cell phone provider on Mars, right? Could, you know, could pick up your cell signal while you’re, you’re talking to 

Speaker 3 [00:30:16] someone from Mars. 

Fraser Cain [00:30:17] Uh, it’s going to be kind of amazing. And, and, you know, we are not by any stretch of the imagination, advanced civilization, you know, you can imagine what the, the, the one that the civilization has been around for 10 million years and has built a radio telescope, the size of their entire star system, what they would be capable of, of detecting through these radio emissions. So, um, uh, so that’s all great. And then, you know, there’s some really interesting science fiction ideas where, you know, we can imagine like warp drives. 

Pamela Gay [00:30:56] And high energy particles that get created in all of these different kinds of reactors, we’re forever trying to figure out the origins of this or that cosmic ray and a lot of them we can’t, we never will, but you can imagine that you start to detect basically a line of, of places where these particles are emanating from. And that could be essentially your signature of some sort of a nuclear or matter, anti -matter or otherwise generating wild high energy particles spaceship going by emitting these particles as it goes. And as we get more and more into multi -messenger astronomy, where we’re combining our ability to look at things, uh, in all the colors of light, looking at things through particles and ultimately looking at things also in your gravitational signatures, we’re not going to be detecting the gravitational signatures of a normal spacecraft, but the particles and the light are things that you can imagine string of gamma rays, infrared excess. Oh, that is a matter anti -matter drive 

Fraser Cain [00:32:14] over there. Did you see the paper where they were talking about how we could use LIGO to detect a warp drive failure? 

Pamela Gay [00:32:23] No, that one I missed. 

Fraser Cain [00:32:25] Tell me more. 

Speaker 3 [00:32:26] Yeah, yeah. 

Fraser Cain [00:32:27] So, so just that, that, you know, when a warp drive is operating, it’s going to be essentially moving space time and that’s going to be creating gravitational wave ripples as this thing goes past. But the thing that would be the largest broadcast of gravitational waves would be when the warp drive bubble fails and collapses, and that you would then get this shock wave of, of gravitational waves would emanate from wherever the, the warp drive failed. And that would be the clearest, strongest signal that we could receive that, that someone is out there using a warp drive is when 

Speaker 3 [00:33:00] they all died. 

Pamela Gay [00:33:02] And that’s at a resolution LIGO can see? 

Fraser Cain [00:33:05] I mean, it depends on the distance. Okay. So yeah, it just depends on how far away it is. Like LIGO is amazing. Like you can detect colliding black holes hundreds of millions of light years away. I’m not sure how far away it could detect a warp drive moving through the Milky Way. 

Pamela Gay [00:33:19] And it’s the frequency issues. So as, as we start looking for smaller compact objects that are crashing into each other, we’re going to start meeting the resolutions that Lisa’s going to give us. And as we figure out, oh, this, this is the signature of an exploding warp coil. 

Fraser Cain [00:33:37] That’s sad. 

Pamela Gay [00:33:40] I, it, what frequency band is it going to be in? Is this the next wow signature that we’re going to find? It actually does turn out to be something cool. 

Speaker 3 [00:33:50] Yeah, that’d be cool. 

Pamela Gay [00:33:50] Yeah, this, the pollution that causes astronomers to curse and blame whatever the next generation version of pigeon poop in their detector is could very well end up being civilization. And that’s just amazing to think about. 

Speaker 3 [00:34:08] Yeah, yeah. Awesome. 

Fraser Cain [00:34:09] So, I mean, this is just like we’re literally just scratching the surface of some of the amazing ideas that people have proposed. 

Pamela Gay [00:34:17] Yeah. 

Fraser Cain [00:34:18] And, you know, I keep I mentioned in the beginning of this episode that there’s this list. 

Speaker 3 [00:34:23] I really want to give my hands 

Fraser Cain [00:34:24] on this list, because then I can provide this kind of comprehensive breakdown of all of the ideas. But I hope that gives people. So any time you do anything, ask yourself, could we find aliens doing that thing? What what signals are we giving off as we just run about our daily lives? Yeah, it’s very cool. 

Speaker 3 [00:34:42] Awesome. 

Fraser Cain [00:34:43] Well, thanks, Pamela. Thank you, Fraser. 

Pamela Gay [00:34:44] And thank you to all the people out there who support us via Patreon. We would not be here without you. And we’re in the process of cleaning up our website. And you’re allowing Aviva and Allie and Rich to really allow us to get things cleaned up into a new age. This week, I would like to thank Alan Gross, Alex Cohen, Andrew Stevenson, Andy Moore, 

Fraser Cain [00:35:13] Bebop Apocalypse, 

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