Astronomy Cast

There is an ongoing debate on where NASA should go next with humans: to the Moon or Mars. (Or maybe an asteroid or one of Mars’ moons). We are on the verge of sending humans back to the Moon. At the same time others would prefer we focus our exploration on Mars. It’s a tough choice because there are costs and benefits to both. Let’s try to give this conversation some nuance. Let’s discuss the reasons for each of these worlds.

Show Notes

• Meteor Shower Visibility & Observation
• Meteor Shower Observation
• Reason for Human Spaceflight
• Ethical Considerations of Spaceflight
• Robots vs. Humans in Space Exploration
• Space vs Extraterrestrial Exploration
• Moon Launch Frequency
• Moon Mission Duration & Advantages
• Challenges of Martian Environment
• Energy Requirements for Space Exploration
• Power Challenges on Mars & Alternative Power Sources
• Lunar & Mars Advantages
• Human Adaptation to Martian Gravity
• Communication Challenges
• Exploration Priority
• Book Recommendation

Transcript

Fraser Cain: Astronomy Cast Episode 752 Should we go to the Moon or Mars next? 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 Kean, 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?

Dr. Pamela Gay: I am doing well, and happy is that a meteor, a satellite, or a lightning bug season for all those who celebrate.

Fraser Cain: Wow, I wish we had lightning bugs. We have non-lightning lightning bugs.

Dr. Pamela Gay: Oh.

Fraser Cain: Yeah. They are genetically lightning bugs, but they don’t light up, which is really disappointing.

Dr. Pamela Gay: Those are failed lightning bugs.

Fraser Cain: Yeah, they have one job. But man, spring is just exploding all around us. It’s amazing how much of just the swallows are back, all of my tulips are up, the daffodils are up, and we are laughing.

Dr. Pamela Gay: And it’s the lyrids and the eta aquarids. So if for some reason you feel the need to get up before dawn, it’s wild out there. Because it’s often easiest to see meteor showers in the couple of hours before astronomical twilight and sunrise.

You are seeing them at the same time that sunrise has already occurred at orbit. So I know that the meteor showers are about to tick up at the same time that I start seeing more and more satellites. And so I swear, it is always this, is that, no, is that, no.

Fraser Cain: That meteor is moving too slowly.

Dr. Pamela Gay: Or it’s a lightning bug in switched directions, it’s one or the other.

Fraser Cain: And so one other piece of news, I just bought a Seastar S50. We’ve been touting them, but we’ve never actually owned them or used them. And so I just got one.

And I’m already sort of climbing the difficult mountain of new knowledge. But please, I’m sure some of you out there have these things, and you’ve already gone through all of the things that you had to learn early on. And so if you’ve got recommendations, let me know, please.

All right. We are on the verge of sending humans back to the Moon. At the same time, others would prefer we focus our exploration on Mars.

It’s a tough choice because there are costs and benefits to both. Let’s try to give this conversation some nuance. So before we have this conversation, I want to have a larger fundamental conversation about the value of human space exploration.

Because I think there’s going to be a bunch of people who are listening to this are going to say, why are you talking about the Moon or Mars? The answer is neither. Duh.

We send the robots. So let’s just take a second and explain why we think that there is a place for human space exploration.

Dr. Pamela Gay: So there’s two different groups of humans that go to space now. One of them is the folks that are going up on government-funded missions, typically. And these humans are doing this for a trio of reasons.

One is just general peacekeeping, being able to keep the International Space Station functioning as a multinational endeavor is perhaps one of the things that keeps the U.S. and Russia talking on good grounds. And our two nations have been, and the USSR prior to that, have been trying to enable peace through science for decades. So peacekeeping is one reason that you put humans in space.

Then there is also the fact that we have thumbs and creativity. And having humans in space allows us to tinker and to fix and to figure things out in ways that would require purpose-built robots at this point. So having humans allows creative activities that otherwise just can’t quite happen yet.

We’re really good construction workers and mechanics. And so putting humans in space to do those things that are spur of the moment and to fix those things that suddenly go boink in the night is something that we’re also good at. And then the third reason to put us up there is we’re studying the biology of it.

We are our own test subjects. And we need to fund the humans as test subjects because then there is that second population of humans, the extremely wealthy, who are going to go no matter what.

Fraser Cain: Who will think about them?

Dr. Pamela Gay: And it’s probably for the best that we’re able to go, look, look, you need to know before you go, this is how you stay alive. Because we have already learned that capitalism causes people to do unsafe things. And unfortunately, an entire crew of submariners thought it was or very wealthy would-be submariners thought it was a good idea to get in a tank controlled by a video game controller to attempt to go to the Titanic.

And while going to the bottom of the ocean is actually way harder than going to low Earth orbit, that mission demonstrated people will do stupid things.

Fraser Cain: So I want to completely disagree with your first two premises and partially disagree with your third premise. All right. Go for it.

So I think that there is no reason, no justifiable reason to send humans instead of robots to anywhere ever.

Dr. Pamela Gay: You think the robots are good enough now?

Fraser Cain: The robots are good now and they’re going to get better and they do it for a fraction of the price. And so, and they are safe and nobody gets hurt. And so you always send it like, if you need an outcome, then you send a robot.

If you want to explore Mars, you send a robot. If you want to explore the moon, you send a robot. If you want to explore space, you send a robot.

You always send robots, robots, robots, robots, but, um, but, but space is what’s next. And so once you have stripped away all of your reasons and rationales and justifications, all you’re left with is because that’s the next place for human beings to go because we’re curious and we want to do it and we want to prove it. And I think the most powerful words that have ever been spoken about space exploration that came from, from Kennedy when he said, you know, we choose to go to the moon, um, not because it’s easy, but because it’s hard that, that it brings out the best of us, that, that accomplishing that feat demonstrates to ourselves that that’s the thing that we’re able to do.

And, and so, you know, when people say we should just send robots to the moon and Mars, you know, the, I always counter with, well, why don’t you just send your iPhone on a European vacation? Right.

Dr. Pamela Gay: So I do want to point out, you asked the question to space and space versus another world are slightly different questions.

Fraser Cain: Well, I think you’re, I mean, I think if you were going to use those same reasons, you know, you could still send a robot to Mars. Like it doesn’t matter that you send a robot with thumbs.

Dr. Pamela Gay: Yeah.

Fraser Cain: So, and I just think that because, because as soon as you make this argument that we need, you know, that makes it more sense to send a human for, for all of these different reasons, then someone will go, look, I made a robot, it’s got thumbs and now your argument falls apart. And then human space exploration is, is locked away forever. Right?

And old thumbs bought 2.0 goes to Mars, gives us the thumbs up and we never send people. And I think we don’t want to close off that Avenue of exploration that, that there’s just something special about a human climbing a mountain, about a human getting into a better built submarine and going down to the deep ocean, about a human going to the surface of the moon and a human going to Mars. And that once you can, once you strip away all of those reasons, you’re left with one that is pure and there really is no argument against it.

We go because that’s what’s next. We go because that is X, that is the heart of exploration.

Dr. Pamela Gay: And humans can be disobedient, which sounds like a really stupid justification, but there, there’s a story of a NASA astronaut basically being like, we’re going to get that rock. And it was a rock they weren’t supposed to get. It was a rock they were told to ignore, head back and they got the rock and the rock turned out, if I’m remembering the story correctly, to have probably been a meteorite from another world that hit the moon that we brought back to earth.

Fraser Cain: Yeah. Again, I think we can send rebellion bot with thumbs to the moon and Mars. So again, you know, if you’re looking for this kind of control rebellion, I think you can still program it into a bot.

But okay. So, so I just wanted to get that, that first thing. And so the people who are like, never send humans, only send robots.

Like we, we hear you and we did, we disagree and we disagree for faith based reasons. So, so it’s really hard to have an argument with us now about this because we feel in our bones that it would be cool that humans could go to the moon or Mars. All right.

Now we’re going to make the case for those two worlds. All right. All right.

So, um, make the case for sending humans to the moon first.

Dr. Pamela Gay: Launch windows. It turns out that because the moon is going round and round the earth and the biggest concern at a certain level about when to land is what is the phase of the moon when you get there? We can pretty much go once a month, no big deal.

Yeah. Yeah. Yeah.

And, and with Mars, we’re looking at a launch window, November, December, 2026. Another one, December, 2028, January, 2029.

Fraser Cain: Yeah. Every two years.

Dr. Pamela Gay: Yeah. And it turns out iterative design to a point is really the way to figure these things out. So, so just like with the Apollo program, you go, you orbit, you make sure your spacecraft is good to come home.

You go, you almost land or land. You come home and, and this constant iterative design to make sure your spacecraft and everything else works, this get all of your goods there before you get there. You can do all of that so much faster when you have the potential for a monthly cadence of launches.

Yeah.

Fraser Cain: And the flight time to the moon is days, just a couple of days. And so the amount of radiation you’re going to experience is very low. The ability to send resupply, you know, you don’t even have to necessarily follow that launch cadence.

If you need to send emergency supplies, you could send it off cycle and still have it get there. Like you’re not going to time it perfectly for the, for the day, but it doesn’t matter if they really need more toilet paper, you can send that instantaneously and it’ll get there. The amount of time they spend in, in direct radiation is lower because in theory, once you’re on the moon, you can hide from the, from the radiation.

And then when you’re done and you want to come home, you can come home anytime you want. And so, and so I, I a hundred percent agree with you that it, that what you’re getting is this launch cadence, this mission cadence that you are, you are quickly cycling through your ideas. You’re learning your mistakes and you’re fixing them as rapidly as possible.

You’re getting 24 times as many chances to learn lessons by going to the moon as you are by going to Mars.

Dr. Pamela Gay: Yeah. It’s, it’s more like 26, 28, but yeah, it’s wildly more chances and you can even, if you feel like it, land and take off when it’s dark. So come and go as you please.

Some of the orbits are slightly more energy efficient than others, but come and go as you please. And while we very rarely take advantage of that with the international space station, astronauts who are up there have stayed up there when parents have passed away, when other terrible things have happened down on earth and their job kept them in place. But if a medical emergency did arise, we could deal with it in some cases easier than we can deal with medical emergencies in Antarctica.

So if someone gets cancer on the moon or the international space station, we don’t have to worry about the fact that it’s winter, so you can’t take off. Or you’re on Mars, so you can’t come home. Right, exactly.

So that increased launch window gives us the chance to recover from mistakes. It gives us the chance to iteratively design rapidly. It gives us the chance to just try things and know if this doesn’t work, we’re just a couple of days away from home.

Fraser Cain: And is that 95% of the reason to go to the moon first?

Dr. Pamela Gay: No.

Fraser Cain: Okay. You think there’s some other good reasons that have nothing to do with cadence, okay, and distance?

Dr. Pamela Gay: Yeah. So beyond that, the moon has some nice places for dealing with thermodynamics, for lack of a better way to put it. The rise and fall of temperatures that you have to deal with on these worlds that don’t have as much light are killer.

Now Mars does have something of an atmosphere, it doesn’t have the extreme swings in temperature that you find in the moon. But what the moon has is permanently shadowed craters.

Fraser Cain: There are permanently shadowed craters, but there aren’t any permanently illuminated peaks on the moon. But there are places that are illuminated 97%, like you’re going to get a couple of hours of darkness and the rest of the time you’re in sunlight.

Dr. Pamela Gay: For all intents and purposes of battery packs, they’re good. On Mars, places near the pole have polar ice caps that come and go. And I don’t know about you, but I am perfectly comfortable with burrowing into a crater to build a home in its rocky goodness.

And I am uncomfortable on Earth’s glaciers and definitely do not want to be trying to build a home on Mars glaciers.

Fraser Cain: Yeah, that’s pretty scary. And then I think you’re getting four times as much sunlight at Earth and the moon as you are on Mars. And so you need dramatically bigger solar panels to be able to accumulate that energy.

Once you’re out to Jupiter, I think it’s 125th the solar energy that you would have to collect. So if you want to live on Europa. And power is going to be a pretty big, like power is everything.

Whether or not you survive, it comes down to can you generate enough energy? You’re going to need to have more energy if you’re going to go to Mars. So that’s another really big one.

Dr. Pamela Gay: And then as you start thinking about needing solar panels, we all have memories of those poor rovers. We were actually together in Huntsville when we learned about Spirit’s demise. If you get too much dust piled up on a solar panel, it’s no longer going to be able to do its job.

And if you get a dust storm that is too thick for too long, it doesn’t matter if you are capable of going outside with your squeegee and squeegeeing off that solar panel. If the clouds aren’t letting the sunlight through, you’re still going to run out of power. And these storms can last tremendous amounts of time.

And while things like radiothermal generators are an option, do you want to be living with those? They’re great for robots. They’re not as dangerous as a lot of news stories make them out to be, but they still don’t seem like the solution for keeping your base going during a dust storm.

Fraser Cain: Yeah. You’re going to need some kind of portable fission reactor is probably going to be what it’s going to be. You’re going to be huddled up to.

And you know, those have challenges all on their own. All right. So like, are there any other reasons why you think the moon makes sense?

Dr. Pamela Gay: There’s as far as we know, less deadly stuff in the regolith.

Fraser Cain: Wait a minute. Now I’m going to question that because it doesn’t have perchlorates, but it is like asbestos compared to the Mars dust.

Dr. Pamela Gay: Yeah. So you’re going to bring dust inside in a lot of the different spacesuit scenarios. There are a few that I actually really, really like where you essentially dock the back of your spacesuit to your habitat and you wiggle your arms out and reach up and pull yourself out, which is going to be easier on the moon than on Mars.

Um, and these kinds of scenarios are designed to help keep that sharp as glass, dangerous as asbestos sand out of the confines of the capsule or habitat on the moon.

Fraser Cain: But it’s going to get everywhere. Like it’s going to get into every piece of equipment and machinery and every joint and every everything. And this stuff is like, is, is going to grind and cause wear and tear on equipment.

Dr. Pamela Gay: Yeah. It’s gross and terrible. And on Mars, the dust and dirt has been thoroughly weathered, not as weathered as here on earth, just because the atmosphere isn’t as thick and there hasn’t been water for a good long time, but it does have more wear.

So we aren’t fully like, we don’t have a dust sample from Mars to understand exactly how does the sharpness compare between the two worlds? But I don’t think anyone’s planning to try and start a garden with unprocessed regolith that they’ve just mixed poop in and planted potatoes.

Fraser Cain: All of the Martian, I mean, those experiments have been run. I mean, not the poop part, but people have attempted to grow plants in, in lunar regolith on the, the Chinese did this on the moon. So, all right.

So we have, like, it feels like the moon is an overwhelmingly good choice. If you’re going to go somewhere, why not go to the moon? But there are some things that Mars has going for it as well.

Dr. Pamela Gay: So where to start? I mean, the best place to start is it’s at humane temperatures ish, ish, ish. So I, yeah, it can get on freaking believably cold on Mars.

But I still remember the day that little opportunity landed. I was in my office in Harvard. They were talking about the temperatures on Mars.

And I looked at the thermostat, not the thermostat, the temperature readout for our weather station up on the roof. And it was warmer on Mars that day.

Fraser Cain: Yeah. I mean, like near the equator, Mars can get up to 20 Celsius.

Dr. Pamela Gay: Yeah. Yeah. You can get reasonable temperatures ish.

The air pressure is still such that if you attempted to go outside with just an oxygen mask, you would have massive amounts of bruising. The capillaries on your skin would be like, and we explode now.

Fraser Cain: Yeah. It’s like a hundred times less air pressure than earth. So but it’s still better than the moon.

Like I think, you know, if you want some atmosphere, then Mars is better than the moon. And that atmosphere gives you protection from radiation. It gives you like a certain tiny, tiny little level of, of atmospheric pressure.

So it’s still like Mars is in the, like you’re already like, oh, they are, their pressure is so low. Well, yeah. But beats the moon.

Dr. Pamela Gay: Right. And, and this also adds a certain dimension of safety. So on the moon, uh, if you put yourself in a permanently shadowed region, which honestly I recommend, uh, your heating goes out, you die because you freeze to death and everything you have with you freezes to non functionality.

You just freeze. If you put yourself in a sunlit area, you’re dealing with this constant temperature cycling, hot to cold, hot to cold. And that is not good for any structure because things thermally expand and contract.

On Mars, you don’t have the same amount of thermal cycling. You have a yearly thermal cycling and you have more, uh, earth-like day, night, like I said, not identical, uh, temperature cycling. Right.

And if your systems go out, this is going to give you a lot more time to try and recover. We know how she dressed for the cold. We can send stuff so that these astronauts can literally bundle themselves up and probably not freeze to death while they’re trying to fix all of their systems.

It also means because there’s more pressure outside that if you get a leak in your system, um, don’t do like the Russians did and attack the leak, trying to figure out what happened. The video, if you have never seen it, there was a very upset cosmonaut that literally attacked one of the components of the international space station trying to figure out a leak. It is hilarious and terrifying.

Do not do that. But while you’re repairing the leak, air is going to escape slower through the same size holes. So all of these slight improvements by you time to try and figure out how to fix things that you don’t have.

Fraser Cain: If you’re on the moon, you’ve got more gravity.

Dr. Pamela Gay: Yes. So with more gravity, we are still trying to figure out, we do not have enough data on um, how much gravity is necessary to keep human systems happy. Um, there, we don’t know at what point does calcium loss stop, uh, being as big a factor.

We don’t know at what pressure does ocular damage stop being as big an issue, but with higher gravity, if you’re trying to compensate through exercise, you’re probably not going to have to spend quite so many hours banded up trying to exercise against elastic.

Fraser Cain: Yeah. Yeah.

Dr. Pamela Gay: Um, yeah.

Fraser Cain: And so that day length, you know, on the moon, it’s 14 days of day and 14 days of night. Yeah. On Mars, it’s pretty much almost the same as earth, like 20, you get 45 more minutes.

Yeah. Yeah. So just shy of 25 hours.

And that’s, that feels like the, almost the nicest thing. And it’s interesting, um, people have done experiments, like people have gone into caves and let their circadian rhythms just become detached from the actual day night cycle. And it turns out human beings can shift to longer rhythms.

So it should be easy to adapt to a Mars day.

Dr. Pamela Gay: There was one insane researcher. Um, if he was sane, when he went in, he was not entirely sane when he came out.

[Speaker 3]Yeah.

Dr. Pamela Gay: Who put himself in a completely dark scenario for, I want to say it was 75 days. Um, and his day night cycle shifted to about 30 hours.

Fraser Cain: Yes. So there’s room there to breathe for sure.

Dr. Pamela Gay: Yeah. So the longer day, uh, especially if you put it all into your sleep, Lord knows most of us don’t get enough sleep. Um, it’s going to be a good thing.

Fraser Cain: And then, you know, we talked about, and I think this one is the wash, which is that on the moon, the regolith is glass and will cause long-term health damage. And it’s your bloodstream. It is less jagged on Mars, but still not totally safe.

Like there’s some, there’s some research we’ve been reporting on this. Well, not even just the Prochlorates. We’ll get to that in a second.

But, but that even the shape of the stuff on Mars is potentially dangerous that it can be, you know, very small, very, you know, the dust can go into your lungs and can cause potentially damage emphysema, bronchitis, things like that. So, um, but on Mars it is filled with Prochlorates or not filled, but has like 1% of its weight is Prochlorate, which is poison. So you have to wash this stuff.

If you want any chance of, of interacting with it and not causing damage, you know, your poop potatoes will need to be in washed regolith, not just straight up.

Dr. Pamela Gay: Yeah.

Fraser Cain: Um, are there any other advantages to being on Mars?

Dr. Pamela Gay: So.

Fraser Cain: Moons?

Dr. Pamela Gay: I mean, there, there is option C and any of you who remember the early days of the constellation program back under the Obama administration, it feels like every president has their own goals for space exploration. Um, there, the idea was moon asteroid Mars. And the reason that you want to go to something like a distant moon, so Phobos Deimos, go to an asteroid that is not in the main asteroid belt, but is closer, is these are that intermediate experiment where we don’t know if we can successfully land on Mars and then take back off.

It could very easily be a one-way journey. We know that we know how to take back off of lower gravity things like the moon.

And asteroids come in sizes that are very moon-like and smaller down to as small as you want basically. And so these lower gravity environments allow us to go someplace that has all the challenges of Mars in terms of distance, in terms of light travel time, lag. That’s something that didn’t come up is you can have an awkward real-time conversation with someone on Earth if you’re on the moon.

You’re looking at times when there’s absolutely no communications allowed because the Sun is annoyingly located with Mars. There’s blackout windows, there’s 20-minute delays even in some of the most optimum conditions.

Fraser Cain: And then I think there’s a bunch of stuff that’s awash. There’s lava tubes on both worlds, so you can use those. There are local resources that you can use, various kinds of metals and silicon and oxygen and all this kind of stuff on both.

There is access to water in both places, you know, in different spots. So I think a lot of that stuff is awash. So I think we’ve reached the end of our episode now.

So I guess we’ll both vote, but I suspect we’re gonna say the same thing, which is that if you then had to come, you know, someone said choose, you’ve got to decide. It’s one or the other. We’re going to the moon, we’re going to Mars, or to an asteroid first.

What is your answer?

Dr. Pamela Gay: The moon.

Fraser Cain: Yeah, me too. Yeah, it’s the moon. It’s so clearly the moon.

But okay, like I want to throw a bone to the Mars people.

Dr. Pamela Gay: Yeah.

Fraser Cain: If we, in all of humanity’s future space exploration, were only able to go back or go to one of those worlds, and we did it and we were very successful, which is the one that you would have preferred that we would have gone to?

Dr. Pamela Gay: Mars, because I want to go fossil.

Fraser Cain: Mars would be, yeah, like the one that we want to go to is is Mars.

Dr. Pamela Gay: Yeah.

Fraser Cain: But the one that we think practically makes sense is the moon first, then go to Mars. So I think we have no disagreement with the Mars people. Right.

It’s just baby steps.

Dr. Pamela Gay: Can we practice first?

Fraser Cain: Can we practice first? Yeah. Yeah.

Before we put it all on the line and go to the world that is so much farther and so much more dangerous.

Dr. Pamela Gay: Yeah. And like I said, fossil hunting. You can do fossil hunting on Mars.

Fraser Cain: Yeah. Mars is just so cool.

Dr. Pamela Gay: Yeah.

Fraser Cain: And yeah, all of these places, someone’s mentioning in the in the chat, right? Valles Marineris, Olympus Mons, these incredible terrain that Mars is just going to feel like to be in that one third gravity, Mars is going to feel like another place. It is the one that I emotionally would rather us explore.

Someone’s saying we’ve already been to the moon. That’s exactly true. We’ve already been to the moon.

So Mars is the one that emotionally we want to go to. But practically, if we want to do this right, if we want to be careful and rational, we go to the moon first, we learn all our skills, and then we go to Mars.

Dr. Pamela Gay: And I want to recommend the book Red Mars by Kim Stanley Robinson. It’s older, but it still stands up as one of the few to look at all the sociological issues of going to Mars. And don’t buy into terraforming.

That’s not going to happen anytime soon.

Fraser Cain: Anytime soon.

Dr. Pamela Gay: But yeah.

Fraser Cain: Yeah. And then I think the one that will talk you out of all of the reasons that people give for going and living on Mars is… I know what book you’re going to say.

Yeah, is A City on Mars by Zach and Kelly Wienersmith.

Dr. Pamela Gay: Exactly.

Fraser Cain: So good. You know, you’re going into it going, I think we should build a giant city on Mars. You’ll come out the other side of it going, there is no point to build a giant city on Mars.

So all right. Well, that was awesome. Thanks, Pamela.

Dr. Pamela Gay: Thank you, Fraser. And thank you to all of our patrons out there. We would not be here without you.

This week. I want to thank Sergey Manilov, Conrad Hailing, Tasha Nikini, the mysterious Mark, Hale McKinney, John Herman, Joanne Mulvey, Katie and Alyssa, Papa Hot Dog, Michael Hartford, Will Hamilton, Fairchild, Just as it Sounds, J.P. Sullivan, Galactic President Scooper Star McScoopsalot, Boogie Nets, Zeggy Kemmler, David Troge, Nick Boyd, William Andrews, Alexis, Adam Annis Brown, Astro Sets, Gold, Simon Parton, Claudia Mastroianni, Abraham Cottrell, Arctic Fox, Andrew Stevenson, Jim McGeehan, Gregory Singleton, David Gates, Georgie Ivanov, Irene Zegrev, Father Prax, Nate Detweiler, Dwight Ilk, Disastrina, Lou Zealand, Paul D.

Disney, Peter, Alex Rain, Ruben McCarthy, Astro Bob, Alan Gross, Elliot Walker, Jeff McDonald, David Rossetta, Travis Siporko, Mike Haizu. Thank you all so very much.

Fraser Cain: Thanks, everyone. And we’ll see you next week.

Dr. Pamela Gay: Bye bye, everyone.

Live Shows

The post #752: Should We Go to the Moon or Mars Next? appeared first on Astronomy Cast.

Even empty space isn’t empty. It’s filled with the quantum fluctuations of spacetime itself. Which can be measured with famous experiments like the Casimir Effect. There is a surprising amount of energy in space itself, which has led to some interesting theories about how the future of the Universe might evolve. You can’t get something from nothing but sometimes that nothing is something you can get something from.

Show Notes

• Universe as Wave Functions
• Quantum Uncertainty
• Heisenberg Uncertainty Principle
• Zero-Point Energy
• Casimir Effect Experiment
• Vacuum Energy
• Zero-Point Energy
• Vacuum Energy Discrepancy
• Potential Consequences of Vacuum Energy
• Vacuum Energy and Space Expansion
• Hawking Radiation & Unruh Effect
• Inflation and Energy Levels
• Vacuum Decay and Its Potential Consequences
• Unknown Physics
• Multiverse Collision
• Speed of Collision Impact
• Understanding the Universe
• Potential Risks
• Black Hole Evaporation
• Cosmic Ray Energy
• Future Particle Accelerators

Transcript

Fraser Cain: It’s the 365 Days of Astronomy podcast, coming in three, two, one. ♪♪ ♪♪ AstronomyCast, Episode 751, Vacuum Energy. 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?

Dr. Pamela Gay: I am doing well. We have hit one of the key points in Spring. I know that once the apple tree is done blooming, it is safe to plant things into the ground.

And this weekend, the apple tree decided it would bloom.

Fraser Cain: I have completely unrelated news that has nothing to do with Spring, and that is, thank you everybody who responded so incredibly to my desperate plea for a new business model a couple of weeks ago. People were amazing, and generous, and kind, and we did it. That we completely filled the Universe Today gap in the business model.

That removing ads from the website was exactly the right move. And I now live in this post-algorithm, SEO, AI slop, business model, ad network vision of the future, where I just think about the stories that we want to cover, and then we just do it, and then that’s that. It’s amazing.

Dr. Pamela Gay: That’s amazing. I am so happy for you.

Fraser Cain: Yeah, yeah. It’s absolutely incredible. Just to, and you don’t realize, I know I’m going to take another, I don’t know, year to decompress, because so much, the last 26 years of my life has been, well, what will the search engines think?

What does the algorithm want? What am I supposed to do? What do I do now?

And now, I don’t even look at my website traffic. I don’t even think about anything. I’m curious about a story, one of the writers works on that story, and then I am curious about a different story, and that’s it.

And so, we’ve been producing a ton of content, my brain is free and clear, and I’m really grateful to everybody who helped out. So if you are one of those people, thank you so much. You saved my business.

Even an empty space isn’t empty. It’s filled with the quantum fluctuations of space-time itself, which can be measured with famous experiments like the Casimir effect. There is a surprising amount of energy in space itself, which has led to some interesting theories about how the future of the Universe might evolve.

All right, Pamela, so I think we all imagine the Universe as a bunch of little particles flying around or clustered together. We imagine photons zipping through the Universe, but that’s not how a particle physicist truly thinks about the nature of the Universe.

Dr. Pamela Gay: Now, the wave-particle duality of nature is one of the weirder things that we learn about in physics, and it turns out that when you want to think about the Universe, you want to think about it as a number of wave functions that are all interacting with each other. And when we have particles, when we have atoms, what we have is something that has a wavelength, that has a frequency, and it has an energy, and there is a zero-point energy to everything that defines the lowest quantized energy that is possible. And even the Universe, we think, is quantized in its very nature.

Fraser Cain: Whoa. So, again, I’m imagining this proton of hydrogen flying along in the Universe, and it’s not actually a proton of hydrogen. It is a combined wave function across the entire Universe, with a probability of it being the proton that I’m imagining, but also a probability of it being somewhere else as well.

Dr. Pamela Gay: Yeah. Yeah. That’s the messed-up thing.

In general, when you run the equations, things have a kind of mostly known position. Even the Heisenberg Uncertainty Principle, which we did an entire show on ages and ages ago, basically says you can either know mostly where something is or mostly how fast it is. You can’t know both at the same time.

Pick what you want to be accurate about. And so we can get roughly at something’s location. We can get roughly at something’s velocity.

And we can totally get at its energy, we think. And it’s this compilation of energies that builds up to describe our Universe.

Fraser Cain: Right. Okay. And so when you’re talking about that idea of zero-point energy, are you saying that there is this theoretical bottom point, and then you could take your photon and then you could measure its probability across the entire Universe and you’re going to get probability numbers and they can never go down to that zero, which means that although the photon is most likely here in the room with us today, it could be anywhere.

Dr. Pamela Gay: Is that right? It even gets more specific than that. So one of the coolest things is you can take a container and you can imagine that you have attempted to remove all of the mass from it, but because it’s in our Universe, it’s going to have energy in it.

And the zero-point energy of that cavity is defined by the sum of all particles that are capable of existing within that size of a cavity. And so…

Fraser Cain: Nobody ordered this.

Dr. Pamela Gay: This starts to get us to craziness where if you take… and there is an out for what I’m about to say. There is an out.

If you take all the known particles and the size of the Universe, you get to an infinite background energy, which is not something… infinities don’t exist, we don’t believe. They’re just math.

So we have to start looking at things purely in terms of the differences in energy. So you can start to calculate what is the difference in energy between two different containers, one with inside of another one. And this kind of a thought experiment led to actual experiments looking at things like the Casimir effect.

Fraser Cain: Yeah. And this is one of the most mind-bending experiments that’s ever been done, which is like proof positive that this thing that sounds too weird to be true is really true. So can you just explain this?

Dr. Pamela Gay: All right. So imagine that you have two sets of parallel plates. We’re just going to make it as easy as possible.

Energy is inversely proportional to wavelength. So things that have little tiny wavelengths have really big energies. X-ray light, short wavelength, infrared light, long wavelength.

X-ray is going to blast your DNA, IR is just going to warm you up. So you have these two different sets of plates. And you look at what are the wavelengths that fit between the large ones, what are the wavelengths that fit between the small ones.

And you have tiny wavelengths between the small ones. Now, if you decrease the distance between the two closest plates, you have now increased the energy between these two plates. And this ends up causing a bulk force that affects the separation of the plates.

Now, exactly what happens depends on the geometry of a system. You have to be able to get things super close together in order for you to be able to start to see things like this. But folks working with thin films have been able to measure within 5% of what was theoretically predicted the value of the Casimir effect between thin films.

Fraser Cain: And so you get these, only the smallest wavelength fluctuations can fit within the plates. And so you’ve got the small wavelengths, high energy in between the plates, you’ve got the large wavelength. And what you get is a force pushing the plates together.

And literally you just, if you put two plates close together, they’re going to want to push together closer with more force because of this detectable phenomenon. It is, it is bonkers. And it is this like one of the best pieces of evidence that shows that this is real.

So is this vacuum energy, quantum energy, like help me understand what is the distinction between those different concepts?

Dr. Pamela Gay: So vacuum energy is the energy that’s just kind of everywhere. And it can vary. So the amount of vacuum energy you have between those two thin plates and the amount of vacuum energy you have in a room like the one we’re sitting in are two different values.

But overall, the universe has a zero point energy that nothing can get below.

Fraser Cain: Right.

Dr. Pamela Gay: And this can be gotten at, again, the math doesn’t match what we see, can get, you can get at it by adding up what are all the possible particle combinations that could exist, looking at all the different non particles. And then we have to remember, we don’t actually understand how to quantify gravity. And so a whole lot of work has been done to try and say, okay, so this background energy that is absolutely everywhere that we see fluctuations, like you stick mass somewhere, that’s a bunch of energy.

Clearly, you don’t have zero point energy on a planet. But when you start to figure out could this zero point energy, could this background energy be what’s powering dark energy? And this was like the first place people went when they were trying to understand what dark energy is.

You end up with a difference of a factor of 10 to the 140 last time I looked up the numbers. And that’s kind of an obscene difference. And the only way we have to justify this extreme difference is, well, we haven’t included gravity yet, which is kind of uncomfortable, but that’s where we are, folks.

But at the same time, zero point energy has some super weird and extremely troubling potential consequences.

Fraser Cain: Yeah. So, so I just want to sort of go back to what you just mentioned. So, in other words, it’s not surprising or it’s not completely unsurprising that when you have more space, then you have more vacuum energy because you have more space, more place to put your quantum particles and your waves.

But also then you, that could then be, have being a force. We talked about the Casimir effect. So you could then imagine you get more space, you get more force, you get more, that creates more space, you get more force, and it just continues to add this pressure into the, into the universe.

But what you’re saying is, is that that’s great in theory, but the, but the amount that would be measurable is dramatically different than what we find. Yeah. Okay.

So then what are some of the sort of unsettling possibilities about this vacuum energy?

Dr. Pamela Gay: Okay. So we’re going to start with the least unsettling and perhaps the one that everyone is most familiar with. And that is black holes aren’t permanent.

If Hawking was correct. And here the idea is that the energy that you have just hanging out in space, being energy allows particles to zip in and out of existence. These are virtual particles, again, Casimir effect, we know they should exist.

Well, if, if space has all the quantities of a particle, if it has polarization, spin, all of these things, and we believe it does, this means you can have a matter particle and anti-matter particles spring into existence. And if they spring into existence and they both have mass and mass is just a quantity, it’s scalar. If they spring into existence on either side of the event horizon of a black hole, one of them can zip away while the other is trapped inside.

And the one that zips away, whether it’s matter or anti-matter, it’s carrying away mass.

Fraser Cain: So I’m going to do something completely unprecedented here in the show. And that I’m going to tell you that what you were describing is wrong. And that this is what Stephen Hawking put in his book, um, a short history of nearly everything.

And he knew that it was a misnomer and, and this sort of thought experiment has been debunked many times.

Dr. Pamela Gay: I read his book. I am guilty.

Fraser Cain: I know. I know. I know.

I know. And so let me take another crack at it, which is, and then we can sort of get to a more hybridized explanation. So, um, and I’m sorry to do this, but I know we’re going to get emails.

Dr. Pamela Gay: I am happy.

Fraser Cain: No, no. So, so, um, observational astronomer, I trust the books I read. So we know that when we, so there is this sort of mechanism called unruh radiation, and this is caused by an acceleration through the universe.

That if you were on a spacecraft and you were accelerating through the universe, you would be experiencing a flux of these particles of these virtual particles of these quantum waves striking your spacecraft. And it only exists when you are accelerated. And it’s like an increased amount of radiation that you’d be experiencing that is just coming from your interaction with space time itself.

And so we know that thanks to Einstein, your acceleration through the cosmos is equivalent to your being in a, in a gravity well, be it around a planet being around a black hole that if you closed your eyes and you couldn’t tell whether your spacecraft was accelerating through the universe and experiencing this bath of radiation, or whether you were under the influence of a really powerful gravity well that is then causing you to experience this radiation.

And so from the perspective of an outside observer, you will see radiation coming from both accelerating through the cosmos and being in the presence of a large black hole. Now this can’t come from nowhere. And so something has to give up the, has to give up the mass equivalent to the energy that is being radiated away by gravity wells, by objects, by mass.

And so that the thing that we experience is this, this Hawking radiation. And so it’s purely based on the equivalence principle between acceleration through space time and the being in a gravity well next to space time. And the amount of radiation you experience depends on the sharpness.

But it’s been theorized that even planets, people will Hawking radiate over long enough periods of time.

Dr. Pamela Gay: He lied to us with his analogy.

Fraser Cain: He admitted later that it was a rough analogy that wasn’t that useful. So yeah, yeah, yeah, I know. I know.

And so you’re hearing this all the time. And so now you get the comet brigade going, no, no, no, that’s not, that’s not true. And so, and so this, this idea of this unruh radiation is a, is sort of a much easier way to kind of wrap your mind around it.

And that gets away from the people asking like, oh, I thought that, um, you know, why is it if particles are going into the black hole, why does the black hole get less massive? Shouldn’t the black hole get more massive? Well, you know, the whole point is that, that it’s not about virtual particles that are going into black holes.

It is just about this equivalent that there is this effect on space time by both acceleration and mass because they’re equivalent.

Dr. Pamela Gay: So the wild thing is that I now need to figure out how to wrap my head around is black holes above a certain size aren’t actively getting smaller because of the amount of cosmic microwave background and other particles falling into them. So you don’t have to worry about massive black holes going away as long as we have things like the cosmic microwave background.

Fraser Cain: And because there’s still an influx of radiation coming from the CMB from particles dropping into them, whatever. And that you, you get the, the, the most of this evaporation, this radiation comes from the places where the gravity well is the steepest. And so that’s why the supermassive black holes radiate more slowly than actually the stellar mass black holes.

And the small primordial black holes will radiate the fastest. Right. They’ll go away because they have a really sharp, uh, like essentially a, a kink in their gravity.

Well, a point, a jerk, a moment of the highest acceleration.

Dr. Pamela Gay: Okay. So with that divergence aside, all right, with that divergence aside, let’s continue. Okay.

So now we can get to the extremely disturbing things. Yeah. So, so one of the ways that theorists have come up with to explain the period, the epic of inflation in the first moments of the universe where the universe went from atoms sized to solar system sized in a fraction of a moment, um, is that the universe was actually collapsing from one energy level to another and that energy expanded out our universe.

Now that implies that if we aren’t actually at a zero point energy, that we are, if we are at a quantized higher level, that the universe can again drop energy levels, right?

Fraser Cain: So what we think is the lowest amount of energy might not actually be the lowest amount of energy. Yikes.

Dr. Pamela Gay: And if we can drop energy levels again, that means we can go through inflation again. Yeah.

Fraser Cain: So like what you’re saying is like, you would like, we all, everything is nice and everything is balanced. I’m trying to, I’m trying to think of analogies, right? And so I’m sort of thinking about, let’s say an earth, you know, plate tectonics, you’ve got a bunch of plates that are sitting and they’ve reached this perfect equilibrium.

And then suddenly everything slips and shifts and you now move to a new equilibrium. But in between you had brutal earthquakes.

Dr. Pamela Gay: And it’s a little bit worse than that because, Oh great.

Fraser Cain: Yeah, no. What could be worse than brutal earthquakes?

Dr. Pamela Gay: Bring it on. So, if you think about it, we often talk about how trillions of years from now, everything will be a particle fog, essentially an energy fog. And on the way to that state, our galaxy will fall into a galaxy cluster.

Everything will slowly merge, but then everything beyond that cluster that we’re in will disappear over the horizon and we just won’t be able to get light from anything else because it’s too far away. Well, if we go through another inflation, we could have that happen fairly instantaneously at a random moment in time. And who knows what that will actually do to everything embedded in space-time.

Fraser Cain: Right. When you think about like the original inflation, it was something like everything in one, 10 to the power of minus 22 seconds, I don’t know what that is, a octotillionth of a second. The universe went through a whole bunch of doublings of size.

Dr. Pamela Gay: Yeah. Yeah.

Fraser Cain: You know, imagine if all of your atoms decided they were going to go through a, or the space between your atoms decided they were going to go through a doubling several times in a fraction of a second.

Dr. Pamela Gay: This is where when the universe did this, when everything was pure energy, you didn’t have to worry about atoms getting held together or torn apart. And so now theorists have to like worry about things like, so what forces are going to be the greater forces? We know that currently gravity is stronger than whatever is pushing our universe apart.

And so things that are gravitationally bound stay gravitationally bound. We know that in general, things that structurally hold devices together through electromagnetic effects. Atomic forces.

Fraser Cain: These are all, right. These are all way stronger than the forces that are trying to push them apart.

Dr. Pamela Gay: But what happens if inflation happens again?

Fraser Cain: Yeah.

Dr. Pamela Gay: Yeah. Yeah.

Fraser Cain: That, that, that your, the gaps between your atoms go through a series of doublings.

Dr. Pamela Gay: And this is where there, there are as many theories as you can stick theorists into a room and then multiply it a few times because some of those people are going to have more than one possible theory. And so we, we don’t know what would happen if we aren’t actually at a zero point energy. And the other side of this is the idea that there’s this background energy created by the summation of all of these different wavelengths across space kind of gets us back to the idea of ether.

And that’s just weird that everything goes full circle sometimes.

Fraser Cain: Right. Maybe that’s, that’ll be a different show. So, so is that vacuum decay, what you just described?

Yeah. Okay. Right.

And so let’s say, and, and you know, the more space you have, and if this is a probability than the bigger the universe gets, that there is a higher and higher chance that this could happen somewhere randomly across the universe, that some part of the universe could hatch upon a new idea to collapse down to a lower energy state. So what would happen next?

Dr. Pamela Gay: So this is where you start getting into all sorts of people attempting to imagine things without understanding necessarily what timescales things are going to happen on. And you end up with a very similar problem with the idea of two universes in a bubble multiverse that have different physics colliding and merging. You can imagine the difference rippling through space.

And if it is slow enough, you basically see part of the universe go weird and then you die.

Fraser Cain: But it would move at the speed of light. It couldn’t go faster than the speed of light. Could it?

Dr. Pamela Gay: No. But it could go slower than the speed of light.

Fraser Cain: Yikes.

Dr. Pamela Gay: Yeah.

Fraser Cain: Right. And so, so if I guess the worst case scenario is it goes at the speed of light. And so the moment that you find out that this is happening, you’re undergoing inflation.

But maybe a more horrific version of that is that you actually watch the universe getting torn apart as it approaches you at close to the speed of light. Let’s say neutrino speed as opposed to light speed.

Dr. Pamela Gay: Yeah. Yeah. Neutrino speed would still be hard to see.

But yeah, we don’t know these things.

Fraser Cain: Right.

Dr. Pamela Gay: There’s so many things we don’t talk about that we don’t know. We don’t know how to quantify gravity. We don’t know how to explain the fact that we have this fits on a grid like it was designed by a board computer programmer graph of particle physics.

It’s looking like supersymmetry isn’t real. Basically, folks at the LHC are now finally willing to say, look, we should have found it by now. We have not give up.

Now do string theory. So there’s all these things that kind of are predicated on each other. Understanding the full nature of the particle zoo, understanding how to quantify gravity, if it’s quantifiable.

All of these things fit together as a whole. And until we understand that whole, we can’t fully understand the consequences of universes colliding of having the background energy level of the universe drop from one level to another through vacuum decay. Yeah.

So we are at this fabulous point of knowing questions, not knowing answers and being able to make stuff up.

Fraser Cain: So how do we take advantage of this stuff? I mean, if there’s that much energy packed into every cubic meter of the universe, you know, Stargate, they had the zero generator.

Dr. Pamela Gay: Right.

Fraser Cain: How do you how do you extract energy out of the cosmos itself?

Dr. Pamela Gay: I, I’m just an observer. This isn’t something we’ve figured out yet. I’m a sci-fi fan, but this isn’t something we’ve figured out how to do beyond being able to say, yes, there’s a Casimir effect.

It’s really hard and expensive to prove it’s there, but it’s there. I think we’re better off figuring out how to do productive vision first.

Fraser Cain: Right. As opposed to attempting to extract and who knows what kind of disastrous outcomes could come, like talk about a tragedy of the commons where we drop the universe down to. Is that the Fermi paradox?

Is that the is that the is that the great filter?

Dr. Pamela Gay: I don’t think it’s the great filter, but but I mean, this is one of the problems with particle physics is there’s always this concern that we’re going to do something profoundly wrong and many good sci-fi novels are predicated on this idea where you start to imagine the big one that I think got the most publicity is the when they turned on the Large Hadron Collider to do the Higgs boson search. There was the well, what if we create microscopic black holes that fall to the center of the Earth and begin devouring the planet?

And it turns out it’s not really a problem. They eat very, very slowly. That one I did run the math for.

I was teaching physics at the time. It was far too much fun.

Fraser Cain: Right. That the science that predicts them also predicts that they will have evaporated before they even hit the ground.

Dr. Pamela Gay: 

And even if they don’t evaporate, which would have been cool because it could have allowed Hawking to finally get the Nobel Prize. But if you also run at figuring out he was wrong, they don’t evaporate. They’re not problematic.

They eat very slowly. They’re very tiny. They mostly just split between atoms going high.

I’m a black hole.

Fraser Cain: The thing that I love with that whole thing was that there are cosmic rays hitting the atmosphere with more energy than the LHC is capable of producing. And so we are already in a natural particle accelerator that is greater than anything humanity has currently built, but not necessarily what humanity might eventually build. There will come a day when someone proposes a particle accelerator that is more powerful than anything that’s ever been detected by the universe.

And then we are truly in unforeseen territory. And maybe that’s when we destroy the universe. Thanks, Pamela.

Dr. Pamela Gay: Yeah. Yeah. Some nights, some days that seems like the correct output.

Fraser Cain: We brought this around to an apocalypse, which is your favorite subject.

Dr. Pamela Gay: It’s excellent. It’s excellent. All right.

Thank you all so much. Thank you for helping Fraser keep universe today going. Thank you all of you who also support CosmoQuestX and allow me to keep everything going over there.

This show is also supported by Patreon. Everything we do, Fraser, myself, this show, we’re supported by you. This week, I’d like to thank the following humans.

Sergio Sansevero, Bill Smith, Brett Moorman, Jarvis Earle, Slug, G. Caleb Sexton, Andy Moore, Evil Melky, Breznik, Andrew Allen, Cody Ross or Cody Rose, rather, Brian Cook, Robi the dog with the dot, Kate Sindretto, Helga Bjorkog, Steven Veidt, Christian Magerholt, Andrew Palestra, Gerholt Schweitzer, ZeroChill, Les Howard, Gordon Dewis, Kim Barron, Katie Byrne, Masa Herleu, Alex Cohen, Matt Rucker, Andesor, Steven Coffey, Michael Regan, Diane Philippon, Philip Walker, Sean Matz, Cooper, Sam Brooks and his mom, Jeff Wilson, Matthias Hayden, Kami Rassian, Glenn McDavid, Kim Garish, Robert Cordova, David Bogarty, John Fays, Christian Golding, Frank Stewart, Time Lord Iroh, Jim of Everett, Sergei Manilov, Conrad Hailing.

Thank you all so very much.

Fraser Cain: Thanks, everyone. And we’ll see you next week.

Dr. Pamela Gay: Bye-bye.

Live Show

The post #751: Vacuum Energy appeared first on Astronomy Cast.

When enormous stars detonate as supernovae they release a burst of neutrinos that can be the first sign of a coming explosion. Now, astronomers have built a network to watch for that flash of neutrinos, and help direct their telescopes for when the sky show begins. Supernovae explosions occur in stages, with neutrinos being emitted hours before photons. If we can accurately detect those neutrinos, we might just be able to get on target before the light show even starts…. Maybe.

Show Notes

• Celebrating the 750th episode of Astronomy Cast.
• Topic Overview: Exploring how neutrino detection can provide advance warnings for supernova events.
• Understanding Supernovae and Neutrinos
• Supernova Mechanism
• Role of Neutrinos
• Detection Timing
• The Supernova Early Warning System (SNEWS)
• Significance of Early Detection
• Scientific Benefits
• Challenges
• Historical Context
• Supernova 1987A
• Impact on Astronomy
• Future Prospects
• Advancements in Detection Technology
• Integration with Electromagnetic Observations
• Importance of SNEWS

Transcript

Fraser Cain: AstronomyCast, Episode 750, The Supernova Early Warning System. 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?

Dr. Pamela Gay: I am doing well. Happy 750th episode, Fraser.

Fraser Cain: This is it, 750 episodes, and we’re going to celebrate by producing an episode of AstronomyCast.

Dr. Pamela Gay: Which is like science, science. We need science.

Fraser Cain: That’s just what we do. That’s why we’re here. So when enormous stars detonate a supernovae, they release a burst of neutrinos that can be the first sign of a coming explosion.

Now astronomers have built a network to watch for that flash of neutrinos, and help direct their telescopes for when the sky show begins. So before we get into all of the really cool science and the network itself, and I think people are going to go, wait, wait, wait, what? You see the neutrinos before you see the light from the supernova?

That’s weird. I thought neutrinos can’t, nothing moves faster than the speed of light, the supernova is moving at the speed of light. How do we see the neutrinos first?

Dr. Pamela Gay: So neutrinos do move slower than the speed of light. They do have mass. They are moving exceedingly fast, like it took us forever, it felt like, to figure out if they had mass or if they didn’t because their speed was close enough to the speed of light that it was within error.

We’re talking about neutrinos from galactic or near galactic supernovae, so like the Large and Small Magellanic Cloud, close enough.

Fraser Cain: Or in the galaxy, right?

Dr. Pamela Gay: Yeah, so galactic supernovae or near galactic. And because there’s a several hours lag between the neutrinos coming out and the first detection of light, that allows something moving near the speed of light to reach us before the light does.

Fraser Cain: Right, but why? Oh, sorry. How do we see the neutrinos before we see the light?

Like if we saw Betelgeuse go off and it’s only, say, 640 light years away, we would get the neutrinos before we saw the light from the supernova. Why?

Dr. Pamela Gay: It all has to do with the fact that the neutrinos are just going to fly through everything for the most part. Some will interact. Whereas it takes time for the outer parts of the star to first of all figure out they’re supposed to be glowing differently.

And second of all, for that light from inner parts of the star to escape through all that medium where it’s going to get absorbed and re-emitted and absorbed and re-emitted and get a lot of Brownian motion going on.

Fraser Cain: Right, right, right. I mean, we talk about this idea of this random walk that photons have to make to even get out of the sun in the first place. That when you have fusion at the core of the sun and it produces a photon of gamma radiation, that then gets absorbed by another atom.

And then that has to re-emit it, and then that gets absorbed, re-emitted, absorbed. And it can take 100,000 years from when a photon is generated at the center of the sun to when it actually reaches the surface. Now is it the same photon?

It’s been absorbed, re-emitted, and so on, but that’s the gist of the dilemma. But a neutrino, we’ve talked about this, they’ll go through a light year of solid lead, no problem. The interior of a star is nothing.

It is like glass, light shining through glass to them.

Dr. Pamela Gay: And the time scales for all of this happening is kind of wild. You end up with supernovae happening in a couple of different scenarios where the core of the star suddenly becomes degenerate. The one that we talk about most is iron.

The center of the star builds up into heavier and heavier atoms. It gets to the point where it has Fe, iron, in the core, and it goes to try and fuse two of these atoms together, and the atoms go high. We need to have energy added to us if you would like to do that.

Everything that’s lighter mass, you go to add them together, and they release energy. It’s at Fe, it’s at iron, where we have this sudden switch to the binding energy of the larger atom is going to need to have energy added into it.

Fraser Cain: It’s so shocking to me how instantaneously this happens, that up until iron, you’ve got this outward light pressure that’s coming from the interior of the star that’s pushing back against all of the mass that is trying to pull itself together. You have this balance, this hydrostatic equilibrium. As it moves up that chain of elements, you reach that point where you get to iron, and it’s like a light switch.

It just shuts off the entire star in a fraction of a second, and now suddenly there is no outward pressure, and the whole star just collapses inward. It can get up to 70% the speed of light, and it is falling into the very center of this star. It’s ludicrous.

Dr. Pamela Gay: One of the calculations I ran across while prepping for this show was the 5,000 kilometer across core that is iron will collapse down to about 20 kilometer across neutron degeneracy pressure supported neutron star in like one second.

Fraser Cain: One second. Yeah. Just boom.

All of that material is hammering the core to make that collapse, and you get neutrinos from the highest energy reactions in the cosmos. You get an enormous amount of neutrinos that are formed in this moment, and they instantly escape while, as you said, the light and the matter is trying to figure out what to do. Do I move over here?

Do you go over there? What’s going on here? Finally, you get this flash of radiation on the surface of this star that then continues to glow and grow, and it gets brighter and brighter and brighter, but the neutrinos are already gone.

Dr. Pamela Gay: Yeah.

Fraser Cain: They’re already out.

Dr. Pamela Gay: The neutrinos are like every flavor, every style. The number of ways that neutrinos are getting created is kind of crazy. First of all, you have as the core collapses, you have the protons and the neutrons going eek, eek.

The protons with the electrons are combining. They are producing neutrons and anti-neutrinos. Then you also have some of the protons and electrons are liberating themselves because neutrons are not stable.

You have beta decay and inverse beta decay producing electron neutrinos and anti-matter electron neutrinos via both these mechanisms. Now, creating the neutron core is the easy one to think about, but you also do have the neutrons that are going back into protons and electrons periodically. Then, you also have all the thermal radiation that’s coming out where you have a ton of positrons and a ton of electrons that are going to annihilate against each other, producing light, producing neutrinos.

So, you have particle annihilation, which is a thermal production. We still don’t have any evidence of it, but there’s also theoretical concepts that photons interacting with particles could also produce neutrinos. Yeah, it’s wild, all the different things that are spontaneously going on, all because the center of the star gave up the ghost of potential energy.

It’s something like 99% of the gravitational potential energy of the star gets converted into neutrinos.

Fraser Cain: All right, so we understand the underlying science that we get this cool trick that we can observe forthcoming supernovae. What is the Supernova Early Warning Network?

Dr. Pamela Gay: It is a network of a variety of different neutrino detectors that work in a variety of different mechanisms, from water to scintillation fluid to you can actually have these things that use lead. All these different methods of detecting neutrinos at all these different sites around the world are all unified in a collaborative agreement to share data, and if they suddenly get a flux of neutrinos, and we’ve seen this before with Supernova 1987A. We have seen neutrinos from other things like neutron star, neutron star mergers.

They’re there, and if they all detect these, they should have slight timing variations. These slight timing variations are because of the path difference to each of these different places in three-dimensional space on the planet Earth. If you have enough different places with enough accurate clocks, you can figure out where on the sky to point your telescopes.

Because the neutrinos are coming out significantly hours before the photons should be detectable, there is a chance that we will be able to see a star from moment zero of light being given off.

Fraser Cain: This is a big unsolved mystery in astronomy, that we catch supernovae after they’ve happened. Now, there are the occasional fortunate survey where someone surveyed a chunk of the space, and then one of those stars detonated as a supernova months or years later, and then they come back around, and they’re able to compare, and like, oh, it was this star, and then it detonated as a supernova. But nobody has seen those first moments, the initial brightening, the initial flash of radiation that happens in whichever order it does.

That has never been seen before, and so the hope is on the supernova warning network. Now, we know that we got that flash of neutrinos coming from supernova 1987A, but we didn’t have the warning network, right? Right.

Like, maybe something they puzzled out long after the actual supernova had been visible in the telescopes. It was like, hmm, we see an increased amount of flux here, oh, that was coming from the supernova.

Dr. Pamela Gay: And let’s face it, back in 1987, neutrino detections were still new. This was still new science. We only had a few detectors in the world.

Now we have more like a dozen-ish detectors in the world, and by having more understanding, we now know that they switch identities. Neutrinos aren’t big on staying who they’re born as, so they’ll switch flavors between electron, muon, all these different varieties. They do stay either matter or antimatter.

That is locked in stone. You also have just all these different ways that we detect them again, so this is allowing us to start to see them at a variety of different energies. We weren’t there yet in 1987.

Now we’re there.

Fraser Cain: Mm-hmm. Mm-hmm. And so, how many neutrino events, how many supernova has the Warning Network detected?

Dr. Pamela Gay: Zero.

Fraser Cain: None.

Dr. Pamela Gay: It has found none. Our galaxy is being super annoying, so it is anticipated that a galaxy like ours will have a supernova about every century. So it’s not quite one per century.

That’s what you’ll find commonly written. It’s actually more like 0.8 a century, or every couple of centuries, and three a century. We should be detecting these things.

Fraser Cain: But when was the last bright supernova that we saw in the galaxy?

Dr. Pamela Gay: Kepler supernova, 1604, was the most recent. 1604 is more than 400 years ago. So they’re behind schedule.

Yeah, and so here’s the thing. If a supernova goes off in a super dusty region, we may not see it. The neutrinos will be released, so we’re now in a position to see things we couldn’t see before.

Fraser Cain: I mean, like the other side of the Milky Way.

Dr. Pamela Gay: Yeah, exactly. A lot of these star forming regions, super dense with dust, supernovas occur in star forming regions. So there is a chance there have been supernovae that we simply haven’t been able to see because they were obscure by all of the dust in the disk of our galaxy.

Fraser Cain: Okay, so let’s imagine that we do get a flash of a supernova. Something goes off in our vicinity. Maybe not Betelgeuse close, but 10,000 light years close.

Play this out for me. What will happen?

Dr. Pamela Gay: So what we expect to happen is there will be a wave of neutrinos that hit our planet passing through the planet. The detector that is closest to this incoming wave on our spherical world will detect the neutrinos first. As that wave passes through the planet hitting each of the neutrino detectors on our world as it goes through, detectors will have signals.

This will allow us to figure out the timing if everything works and all the atomic clocks are properly synced and everything else. This will allow us to figure out where on the sky to point. Now, hopefully in an ideal universe, that side is in darkness and all of the detectors on that part of the planet point that direction.

Fraser Cain: I didn’t even think about that. You’ve got like a 50-50 shot about whether or not it’s going to be daytime or nighttime, and so then you’re going to have to depend on the space telescopes to be able to see And what’s even worse is if it’s within 30 degrees of the sun, we can’t even point the space telescopes there because it will blast them. And that’s crazy.

You could get a flash of neutrinos that are from a supernova that goes off on the other side of the sun. It would go right through the sun, no problem, right through the earth, no problem. And we would detect it, but we can’t look at it.

I don’t know, maybe like a mission like New Horizons or something that’s in a different perspective could take a shot of the supernova, but that would not compare to the combined light-gathering capacity of the earth’s and space telescopes that we have arrayed around our planet. That would suck.

Dr. Pamela Gay: Yeah. Yeah. So, so there is that, that issue now, assuming that it occurs in a part of the sky where we can observe it, we get all of the, the most important at this point are the highly sensitive wide angle cameras, because we’re not going to, with a timing method, have it down to the tiny, tiny sliver of the sky that something like Hubble is able to look at.

So we’re going to need to look with the wider angle cameras. Luckily we’re starting to get more and more space-based wider angle cameras.

Fraser Cain: Like Euclid or upcoming Nancy Grace Roman or things like that.

Dr. Pamela Gay: Sphere, things like that. Yeah. So, so you look with the wider angle cameras, software says, Hey, this bright thing didn’t used to be here.

Study, study, study. The key things that we’re going to be looking for are the evolution of emission lines. The thing that generates the light in supernovae that creates that wild light curve that we’re so used to seeing is the radioactive decay of a variety of different elements.

So as you get these different transitions, this, this is where nickel is one of the great blames for supernovae light curves. For instance, this allows us to see the emission lines and it allows us to see the, the shock wave illuminated over a period of days and weeks. Now there, there are two scenarios that are possible that, that will be very interesting.

One of them scientifically interesting. The other, Oh shoot, this will allow us to explain the lack of observations for 300 years. So assume that something like this goes off night side of the planet.

Everything’s looking, everything’s looking, nothing is seen. This will allow us to say this most closely aligns with these star forming regions, all of which have massive amounts of dust in place, a limiting magnitude of if it was in these magnitude ranges, we wouldn’t have seen it. So that starts to tell us, didn’t see it.

Now the other thing that could happen is it’s theorized that you can have core collapse without having a visible supernovae. Now if you have core collapse without a visible supernovae, that, that means you can look and look and there’s no light, but you do get the neutrinos.

Fraser Cain: Right. So like a, like an unknown, like a star just disappearing, collapsing in on itself and it not being able to create the supernova. And that’s interesting.

I mean, we’ve seen examples of stars just disappearing from the sky and it’s been thought that maybe that’s what’s going on, that it was there and then it imploded and it was very efficient and ate its, ate the entire plate, right? And just collapsed it all into a black hole, which is mind blowing. And then that would explain why we haven’t seen the supernova maybe.

And but as you say, there would be this flash of neutrinos even though, and so that would be even more sign that we detect the flash of neutrinos. We look in the direction where it supposedly came from and there’s nothing there.

Dr. Pamela Gay: Yeah. Yeah. So that’s the super interesting.

Fraser Cain: Yeah. And then the surveys show that there’s a star missing.

Dr. Pamela Gay: Right. That would be great. That would be ideal.

Now, the probability of something like that happening is fairly low. This is not one of the common forms of things happening that we expect. But these are all the possibilities that the supernova early warning system is looking for and they, they have a really cool network.

It is funded by multiple funding agencies across the planet. This is international. It engages amateurs through the American Association of Variable Star Observers, which is not just Americans.

It was just named over a hundred years ago. And so there’s people out there ready for these neutrinos to be detected, ready to point in the correct swath of the sky. This is kind of like the gamma ray burst alert network that we had in, in the early two thousands when we were still trying to catch optical afterglows of gamma ray bursts for the first time.

I mean, we’ve seen them for the first time, but for like common times now, gamma ray afterglow is just like another day at the office and it’s the neutrino afterglows that we are chasing with fervor.

Fraser Cain: Yeah. Yeah. Yeah.

And so hopefully the next time that bright supernova, that nearby supernova goes off in the Milky Way, we will be ready. And, and the, you know, the supernova early warning network is the first step. There are other plans in the works I’ve reported on this, that they’re looking to build more powerful versions of this, more sensitive versions that you could expand outward.

And the goal would be to encapsulate Andromeda and Triangulum and try to bring more galaxies into this network. And that, you know, theoretically galaxies that we see within tens of millions of light years are giving off supernova and eventually we’ll get to this place where we’ll see them every couple of years and we will have the ability to, to watch them as they unfold. But nothing would be as, as powerful as seeing one that goes off, you know, Betelgeuse distance.

Dr. Pamela Gay: Yeah. And it’s all about increasing the sensitivity of these systems. When a supernova goes off, all those neutrinos fill a, they go off in all directions, assuming symmetrical supernova, you have to do that sometimes.

And so the further away something is, the smaller the cone of that sphere of neutrinos we’re going to be able to detect. By increasing the sensitivity of our neutrino detectors, we start to be able to see supernovae going off further away. We start to be able to tap into the cosmological background neutrino flux.

There’s so much cool science to come out of this and, and I’m here for it and we will be here for it for…

Fraser Cain: Totally.

Dr. Pamela Gay: Yeah.

Fraser Cain: Hopefully, I can’t wait to report on the first detection with the, with the network. All right. Thanks Pamela.

Dr. Pamela Gay: Thank you, Fraser. And thank you to all of our patrons out there who’ve been there with us over and over through the years. All right.

This week, I would like to thank David Resetter, Travis C Porco, Mike Husey, Jonathan Poe, R.B. Basque, Jimmy Drake, Bob Crail, Tricor, Noah Albertson, Ryan Amari, Mike Dogg, Simeon Torfason, Mark Schneider, Michael Purcell, Jeanette Wink, Brian Cagle, Jason Kwong, Tiffany Rogers, Robert Plasmo, Laura Kettleson, Red Bar is watching. A pronounceable name. You’re welcome, doctor.

Jeremy Kerwin, Kinsaya Pamflenko, Cherisom, The Lonely Sandperson, Scott Briggs, Benjamin Carrier, Jim Scholar, Marco Arasi-Nayla, David Green, Smansky, Rando, Benjamin Mueller, Benjamin Davies, Planetard, John Drake, Bruce Amazine, Paul L. Hayden, Jeff Hornmurder, Pauline Middleink, Jordan Turner, Robert Hundell, Taz Tooley, Lee Harbourn. Thank you all so very much.

Fraser Cain: Thanks, everyone. And we’ll see you next week.

Dr. Pamela Gay: Bye bye.

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