Personally, I don't think there's intelligent life on other planets. Why should other planets be any different from this one?

— Bob Monkhouse

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Ep. 609: The Benefits of Volcanoes

Mon, 06/14/2021 - 1:53pm

Volcanoes can be some of the worst natural disasters we can experience here on Earth, but life wouldn’t even exist without them. What are volcanoes good for anyway?

Download MP3 | Show Notes | Transcript

Show Notes

See the First Images NASA’s Juno Took As It Sailed by Ganymede (NASA)

VIDEO: The Daily Space 10 June 2021: Solar Systems Vary From Star Type to Star Type (CosmoQuest)

Flurry of photos capture China’s Zhurong rover on surface of Mars (Nature)

PHOTOS: Fissures, Lava Flow and Evacuations Continue On Hawaii’s Big Island (NPR)

What is the Mid-Atlantic Ridge? (Universe Today)

What is a hotspot volcano? (NOAA)

Active Volcanoes of Hawaii (USGS)

Soils from Volcanoes (UCSB)

Etna volcano (Volcano Discovery)

Nyiragongo volcano (Volcano Discovery)

Obsidian: Volcanic Glass (Geology In)

Obsidian (Mindat)

Topaz (Mindat)

Tourmaline (Mindat)

Zircon (Mindat)

Granite (

Plate Tectonics (National Geographic)

Earthquakes and the Earth’s internal structure (AMNH)

Eruption on Iceland’s Reykjanes Peninsula 2021: activity updates (Volcano Discovery)

Chasing Magma Around Iceland’s Reykjanes Peninsula (Eos)

NASA’s InSight Detects Two Sizable Quakes on Mars (NASA)


Volcanoes on Mars Could Be Active, Raise Possibility of Recent Habitable Conditions (PSI)

What is a hydrothermal vent? (NOAA)

Paleomagnetism For Rookies-Part One (JOIDES Resolution)

Are we about to have a magnetic reversal? (USGS)

VIDEO: Astronomy Cast Episode 588: Lunar Resources: Lava Tubes

Geothermal Electricity Production Basics (NREL)

Manitou (Colorado) Cliff Dwellings

NASA Selects 2 Missions to Study ‘Lost Habitable’ World of Venus (NASA)

ESA selects revolutionary Venus mission EnVision (ESA)

Volcanism on Venus (SDSU)

Researchers Discover What May Be 37 Active Volcanoes on Venus (Smithsonian Magazine)

Volcanic “pancake” domes in Tinatin Planitia, Venus (NASA)

This is our best look yet at the solar system’s most volcanic object (National Geographic)

Enceladus: Ocean Moon (NASA)

Categories: Astronomy

Ep. 608: NASA Perseverance – The First 100 Days

Mon, 06/07/2021 - 4:59pm

As you all know, Pamela refuses to talk about any missions which aren’t actually doing science. Well, Perseverance has crossed the line, from fantasy to an actual working rover, scooping regolith and yeeting helicopters. What has the rover accomplished in its first 100 days?

Download MP3 | Show Notes | Transcript

Show Notes

Mars 2020 Perseverance Rover (NASA)

Mars Curiosity Rover (NASA)

Mars Sample Return (NASA JPL)

Microphones on the Perseverance Rover (NASA)



WATSON Takes a Closer Look (NASA)

What’s up with this weird green rock on Mars? Perseverance rover is trying to find out. (

NASA’s Perseverance Rover Microphone Captures Sounds from Mars (NASA)

VIDEO: Perseverance Rover’s Descent and Touchdown on Mars (Official NASA Video)

Mars Helicopter (NASA)

Mars Exploration Rovers (NASA)

VIDEO: Interview: Dr. Michael Hecht, Making Oxygen with MOXIE (Fraser Cain)

Sounds of Mars (NASA)

Perseverance rover spots its first dust devil on Mars (

Surviving an In-Flight Anomaly: What Happened on Ingenuity’s Sixth Flight (NASA)

Perseverance Rover’s Landing Site: Jezero Crater (NASA)

Stromatolites (Bush Heritage Australia)

Mars sample return (ESA)


European Space Agency

ExoMars 2022 rover (ESA)


Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast, episode 608: Perseverance Rover, 100 Days and Rolling. Welcome to Astronomy Cast, 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, publisher of Universe Today. With me is Dr. Pamela Gay a senior scientist for the Planetary Science Institute, and the director of CosmoQuest. Hey Pamela, how are you doing?

Pamela:                       I’m doing well. We didn’t get hit by tornadoes yesterday, which is always a plus.

Fraser:                         So far.

Pamela:                       Well, yeah. Well, yesterday is past, so I feel safe saying yesterday we did not get hit by tornadoes.

Fraser:                         Right.

Pamela:                       And spring is here, the yard is aflower with weeds, and we’re heading into Memorial Day weekend, which means all the yard work will be mine. How was your Victoria Day?

Fraser:                         Oh, it was relaxing, and we celebrated Queen Victoria in every way that a Canadian does, which is not one bit. So, yeah. But I didn’t do anything, which was nice. We camped. I didn’t do any work. I didn’t even do a show on the Monday. I took the whole thing off, which was great.

Pamela:                       That is awesome.

Fraser:                         So, I was rested and relaxed, and I’m ready to talk science.

Pamela:                       Good.

Fraser:                         Now, as you all know, Pamela refuses to talk about any missions which aren’t actually doing science. Well, Perseverance has crossed the line from fantasy to an actual working rover. Scooping regolith and yeeting helicopters, what has the rover accomplished in its first 100 days?

                                    I had a teenage daughter. I understand the terminology. I’m with it.

Pamela:                       You said, yeeting.

Fraser:                         Is that incorrect? Do I have to just say yeet? Is yeet it?

Pamela:                       No, you said it –

Fraser:                         Yeeting?

Pamela:                       You’re conjugating it correctly. It is a glorious concept, and it is exactly what this little rover has done to that impossible little helicopter.

Fraser:                         It didn’t. It didn’t. It gently placed it on the ground and backed away slowly and nervously is, I think, the better way to describe it.

Pamela:                       That’s true.

Fraser:                         Yeeting is not what happened.

Pamela:                       It’s true.

Fraser:                         Yeah. So, Perseverance. What is it?

Pamela:                       It is a next upgraded version of Curiosity rover. It’s built on very much the same hardware plan, but as happens when you get a few years from one design to the next, they upgraded the systems. And part of upgraded the systems meant it has a belly full of crazy robotics and electronics, and they’re gonna use that crazy belly to gather up samples of rock.

                                    It also is carrying the first ever microphone on Mars, which people are far more excited about than I ever dreamed.

Fraser:                         Like me.

Pamela:                       Well, yeah. It still caught me by surprise. And they have an experiment for creating oxygen. They have a laser and they are zotting rocks left and right. And then, of course, there’s the little Ingenuity helicopter.

Fraser:                         All right. So then, compare and contrast. If we had Perseverance and Curiosity side by side, and we were looking at them, trying to spot the differences, they’re the same size, right?

Pamela:                       They’re the same size.

Fraser:                         And they’re roughly built on the same chassis?

Pamela:                       Yes.

Fraser:                         Okay.

Pamela:                       So, the heads look very similar. It’s when you start looking at the arms and the underbelly that everything radically changes. It’s when you look at that underbelly and arm that everything radically changes. So, this arm does not have the little divot scraping machine that they have on Curiosity that they’ve been using to rove up to rocks and remove a layer of weathered rock to see what’s underneath.

                                    Instead, the arm had SHERLOC, which is an ultraviolet spectrometer, and it has a laser. And they are literally zotting rocks and listening to hear how the zap sounds, and using that sound, they’re getting an assessment of the density and other characteristics of the rocks.

Fraser:                         Whoa.

Pamela:                       This is not something I imagined. The is the moral equivalent of doing science by knocking on wood, except they’re zotting rocks.

Fraser:                         I had no idea that they actually had any kind of scientific purpose for that microphone. I just thought it was literally just to make some of us out there who wanted to finally hear the sounds from Mars happy. But no, it turns out they’ve got a job for that. That’s really cool.

Pamela:                       Yes.

Fraser:                         So, they’ve got a microscope on the arm.

Pamela:                       They do. Yes. Well, they also have the spectrometer. So, there’s the WATSON camera and the SHERLOCK spectrometer.

Fraser:                         Right.

Pamela:                       And between the two of these, they can take extremely high resolution images of that rock they are zotting, or they can look at how light reflects off of it to get a sense of what is inside, what the chemical composition is. And what’s, kind of, awesome about this entire set up, is they’re currently using it to explore what might be a meteorite from another world that landed on Mars. So, apparently we sent a rover to Mars to look at rocks that fell from space from who knows where.

Fraser:                         Right. Right. Probably Mars.

Pamela:                       So, we don’t know.

Fraser:                         Right.

Pamela:                       There’s this weird looking rock. It was one of the first things that people noticed looking at the images. It looks like it has a bunch of deep pits or holes in it, like a Texas holey rock, a piece of basalt. There’s meteorites. There’s lot of different ways to get this weird pitting texture to a rock. And the way it’s just sitting there, hanging out, looks like what you would expect from a meteorite hitting and hanging out on the surface while the landscape around it gets blown about by dust and wind.

Fraser:                         Right. I’ve seen that rock. We get that in driftwood.

Pamela:                       Yeah.

Fraser:                         Where you’ve got a piece of wood that been beetle devoured, and so has all these little drill holes that makes it look really pockmarked, and then it floats in the ocean and, I guess, shows up on your shore. Who knows where it started out? But yeah, I know exactly what you’re talking about.

                                    So, those are the differences. The arrival at Mars went pretty smoothly. We saw much better video, photographs, this time around. We got to hear.

Pamela:                       And they got higher accuracy on landing due to different cameras. So, they actually have started using machine vision to help steer not just the landing of the rover, but also this is how they steer the helicopter in part. And so, as they were coming down, they were comparing the maps they had of what they expected beneath them, and steering accordingly to make sure they got where they wanted to go.

Fraser:                         Right. All right. So, now we’ve given you mostly an overview of how the rover itself differs from Curiosity. So, know that it’s got a microphone. We know that it’s got a helicopter. We know that it’s all of these additional things. So, what has this rover been up to?

Pamela:                       Mostly it’s been babysitting a helicopter, which is – when I scheduled this 100 days of Perseverance, I was really expecting a lot of Perseverance because back in the days when we had Spirit and Opportunity, they weren’t expected to last that long. They hit the ground, they roved, they made science happen.

                                    And Percy landed, and is like, okay, I’m gonna take my time. I’m gonna rove over to this nice smooth area. I’m gonna drop my helicopter, back away 100 feet. I’m gonna watch my helicopter. And so, it hasn’t done a lot of science other than technology testing.

                                    Now, some of that technology testing it’s done is truly remarkable. Another one of the instruments it has on board – and instrument is really the wrong word. Another one of the pieces of equipment it has on board is MOXIE. This is a system that pulls in the carbon dioxide rich air that is the atmosphere on Mars, and puts it through a lot of heat and a lot of pressure, and separates with an electrode the oxygen off, leaving behind an oxygen, a carbon monoxide molecule, releases that carbon monoxide back into the atmosphere and collects the oxygen.

                                    And the hope is that eventually, instead of having to send the 25 tons of air that astronauts are gonna need to survive a typical Mars mission, they’re gonna send a one ton oxygen creating factory. And MOXIE’s showing that this just is a feasible option for the future.

Fraser:                         Now, I’m going to shamelessly self-promote an hour long interview that I did on my YouTube channel and podcast, with the principle investigator of the MOXIE experiment. And so, if you want to understand the limits of this, how it’s working, what are the constraints, why even test it on the surface of Mars, and more, I spend an entire hour talking with the principle investigator. So, you can go into a tremendous amount of detail, and it was really fascinating. One of my favorite interviews.

                                    And so, if you aren’t already subscribed, I mean, if you’re subscribed to Astronomy Cast, but you’re not subscribed to my podcast, you might want to do that because –

Pamela:                       And that’s, Guide to Space?

Fraser:                         Yeah. Just search for Universe Today wherever you get your podcasts and you’ll find my 750-ish episodes as well. So, you know, in case you’ve run out of Astronomy Cast. Anyways, shameless self-promotion out of the way. Let’s talk about the microphone.

Pamela:                       So, it’s just microphone, but they’re using it in all sorts of different ways. They’re using it, like I said, to listen to the rocks getting blasted with a laser. They have listened to the wind rolling by. They have listened to the sound that the wheels make as the rover roves across the surface to see if they can get a sense of what that surface is like from what it sounds like. As someone who used to own Jeep Wrangler, I could usually tell what was beneath my Jeep when the top was off, by listening to the various kinds of crunching noises it made, and they’re doing science this way.

Fraser:                         That’s really cool.

Pamela:                       It’s just adding an additional sense to their little robot.

Fraser:                         I’m not gonna lie. I’m a little underwhelmed. Not by the microphone, not by the rover, just by the sounds of Mars. Mars, audibly sucks.

Pamela:                       It doesn’t have enough air pressure to sound good.

Fraser:                         Right. That’s right. And I think that’s the big problem. It just doesn’t have the air pressure, and so you’re hearing the laser firing. It sounds like a clicking sound.

Pamela:                       Yeah.

Fraser:                         Or you’re hearing the wind blowing or the rover crunching, and you’re like, is that it? Is that all we got?

Pamela:                       Yeah, yeah.

Fraser:                         So, I think we’re gonna need to see generations of audio engineers working with the sound to be able to do it. And so, when you say, no, no, it’s got a scientific purpose. I’m like, okay, all right. Then this microphone is redeemed.

Pamela:                       Yes. Yes. So, so far, they have zotted rocks. They have roved. They have listened to everything. They have taken pictures of dirt devils, dust devils. They have taken panoramas to catch themselves and Ingenuity off in the distance. And they’ve done a whole lot of babysitting Ingenuity.

                                    So, Ingenuity is the first vehicle we’ve had that has taken off and landed multiple times. And just in time for this episode, it made its sixth flight, and had its first fascinatingly, that looks how I would fly a helicopter, kind of moment.

Fraser:                         Yeah, yeah. So, let’s talk about all the various flights then, or just briefly, what has Ingenuity been up to overall.

Pamela:                       So, the target goal was to test that it was able to fly up to about five meters. That it was able to fly around. No more than 100 feet was the initial goal. And take images of what was below it. It is controlled off of basically the technology you would have in a cell phone or a golf laser distance indicator, and it uses a combination of all those accelerometers to keep track of what it’s doing. And then, it uses the images to get extra control.

                                    And it was those images that caused things to go wrong today. It dropped an image, and was then overcompensating because it didn’t know what it was looking at. But, what’s amazing is that they know that flying these things is hard, so built in all sorts of extra safety things.

Fraser:                         I would say, already it’s so exciting on just the fact that they’ve been able to make this thing fly at all in that think atmosphere. And it’s a fairly large propeller. It’s turning very quickly. The gravity’s a little lower.

Pamela:                       Twenty-five hundred times.

Fraser:                         And really its only job, it’s got two cameras, a battery pack, a little bit of brain power, and a little solar panel, and then everything else is all propeller. But just this idea that you can have an autonomous scout deployed with your rover. There’s no way this isn’t gonna be a standard that ride along with every single rover ever sent  to Mars, from here on into the future.

Pamela:                       It’s a buddy movie.

Fraser:                         Yeah.

Pamela:                       So, they can’t pick the helicopter back up. And it now has an extended mission, which means as Percy goes across the surface, it’s gonna have little Ingenuity flying ahead, lagging behind, basically flitting about keeping up over time.

Fraser:                         It is interesting though, this thing that you mentioned, that it’s amazing and wonderful, but it is almost turning into a job for Perseverance, and Perseverance has work to do.

Pamela:                       Yeah.

Fraser:                         So, what is the big – we’ve talked about this many times in the past, not officially in any one place, but the fact that Perseverance’s job is to search for the conditions for life in the past or the present. That’s its job.

Pamela:                       Yes.

Fraser:                         And when it’s not watching that needy helicopter, what has it been doing to further this task?

Pamela:                       Well, so far it’s pretty much been watching the needy helicopter. Poor Ingenuity doesn’t have the power or the antenna to be able to communicate all the way back to Earth. So, it’s a relay station for the helicopter right now, but this bleak task for the rover is allowing the mission team here on Earth to go, okay, you landed exactly here on Mars. I have all the imagery of Jezero crater, we’re going to plot the best path possible through the delta, through all of the different mineral samples.

                                    And that belly full of robotics that I talked about earlier, is because this mission is gonna go up to rocks, drill into them, use an arm to hold out a sample tube, let the sample that it’s drilling go into the tube, pass it into its belly where another arm is going to grab it, going to hermetically seal it, and then put it into longer term storage. And eventually, after enough of these little sample cups are filled, it’s gonna deposit them all somewhere like, so many science eggs waiting to hatch into new results. But we’re gonna have to send a second spacecraft to go pick them up and bring them to Earth.

Fraser:                         So, you say laying eggs. I like that because I’ve just been describing it as pooping. So, if you’re gonna say that it’s laying eggs, I think that seems science eggs.

Pamela:                       You don’t want to collect poop the same way. Not unless you’re that kind of a biologist, in which case microbiomes are cool.

Fraser:                         Right.

Pamela:                       Yeah, no. It’s laying science eggs. This is how I choose to look at it.

Fraser:                         So then, I mean, what are the – at the point that we’re at right now, like you said, it’s really been just in this test out phase. It hasn’t had a lot of time to do science. What are the things that now Perseverance is gonna be looking for that will really advance its mission forward, to give us some kind of concrete answer about whether or not there were the conditions for life on Mars?

Pamela:                       So, the area that it’s in is the most, yes, there was water here, kind of structure that we’ve put a rover in so far. There is a river delta looking area, and the kinds of minerals, the kind of organics, just a little over three billion years ago that formed this area, could have had life. And so, it’s going to be looking for the kinds of rocky formations characteristic of watery environments. It’s going to be looking for the minerals that form in areas rich in organics.

                                    And if we’re lucky, it’s gonna find things like stromatolites that say, for sure, yes, there was critters here.

Fraser:                         So, sorry. What is a stromatolite?

Pamela:                       Stromatolites are rock formations made out of bacterial mats. So, if you’ve ever owned a fish tank, you know that stuff will grow and form slime layers, for lack of a better phrase. And over time, these layers can build one on top of the other, crushing down, drying out, forming a rock. And stromatolites are the built bodies of formerly live things.

Fraser:                         Slime? Right.

Pamela:                       And so, these bacterial mats that layer up, die off, become fossils that’s about the most advanced we’re willing to hope for, for life on Mars, and it would be amazing if we found these formations that we know we have here on Earth.

Fraser:                         Right. I mean, Spirit and Opportunity could have seen a fish fossil on the side of a rock on Mars.

Pamela:                       Yeah.

Fraser:                         You don’t need anything really special to be able to do that. They didn’t find that. Curiosity would have been able to find that. It didn’t find that. So, Perseverance is taking that to the next level. And so, even if it doesn’t find the Martian fish, even if it doesn’t find the Martian bacteria layer cake – 

Pamela:                       Stromatolite.

Fraser:                         Yeah, stromatolites. It could find like, there was definitely water here, and definitely the place was seeped in organic materials, and you kind of had everything you needed to be able to have life. And then, let’s get those samples home to be able to test them out.

Pamela:                       Exactly. Many years of adventure to go.

Fraser:                         I can remember times when we were looking at Spirit and Opportunity, and they said, yes, water was – there are regions that once had water.

Pamela:                       Yes.

Fraser:                         And it could have just been a flood. Who knows? And then, with Curiosity it was like there were regions that had water for long periods of time. So, if people are just watching the news from Perseverance, what is that thing that says, science goal achieved?

Pamela:                       Oh, man. They have to build these rovers a little bit opened ended. I mean, ideally, they rove up to something and it has the exact composition that you would expect in a fossilized riverbank here on Earth. That maybe even, you see things that are clearly fossilized by volcanic ash going in and petrifying whatever used to be there.

                                    That’s probably a little more advanced than we can hope for, but going through and seeing the diversity of minerals that map the specific wetness, the specific temperatures that allowed those formations to take place. That we can do. We know different minerals form in different conditions. It’s gonna go out, it’s gonna go dig into those minerals, it’s gonna see exactly what is there, and hopefully, someday, something will go and pick up those samples and bring them back to Earth.

Fraser:                         Did you just briefly wanna touch on how the sample return mission will integrate with Perseverance. How is that gonna work as it picks up eggs?

Pamela:                       So, here’s the problem. They don’t have a second mission planned yet. They know someday, something is going to have to go back to Mars and very accurately land, get the samples, and then have the ability to take back off on the Martian surface, with the samples is has picked up, and we have no idea how any of that is going to happen. It is not currently a planned named mission with a window.

Fraser:                         We know a few things. I mean, we know the plan.

Pamela:                       So, the plan is to either send one or two more missions. One which is to go and pick the things up, and have them in its hot little robotic hand.

Fraser:                         The chase rover.

Pamela:                       Yeah. And then, the other is the launching come back vehicle. And it’s possible that that could be a single mission in two parts, or that it could be two different things that land. But we’ve never landed things side by side before, so there’s a lot to be learned in the coming years, but we’re gonna watch it.

Fraser:                         The cool thing about this is that it’s a collaboration between NASA and the European Space Agency. So, my understanding right now is that NASA is gonna build the assent vehicle, using something like MOXIE to help generate the oxygen for the fuel. So, it’s gonna carry its hydrogen, or some other fuel source, and then it’s gonna be able to make the oxygen on the surface. And that will test out what future astronauts are gonna use.

                                    So, that will land on the surface of Mars in the vicinity of Perseverance. And then, Europe is going to build the chase rover, which will land and return samples from that as well as the European Space Agency’s rover, which is gonna be roving in the same vicinity as well, which is going in two years. Got pushed back because of their problems with their parachute.

Pamela:                       And it will stay dead to me until it actually takes off.

Fraser:                         Yeah. Right. If you’re Pamela, you just heard wah wah wah, but for the rest of you listening, they’re planning to build – well, the European Space Agency’s rover is almost ready to go. And that’s launching in 2022.

                                    But then, the Europeans are gonna build the return vehicle, the sample return. So, the chase rover is European, the ascent vehicle is NASA, and then the return vehicle is European to bring all those samples back home. And that will be mind-bending to think that there will be a time, in the next decade, when we will have dozens of samples from the surface of Mars that were hand chosen by scientists. Very cool.

Pamela:                       If all goes well.

Fraser:                         If all goes well. Very cool. Thanks Pamela.

Pamela:                       Thank you, Fraser.

Fraser:                         All right. Do you have some names for us?

Pamela:                       I do. As always, we are brought to you by you. We are so grateful for all of our Patreons at who make this happen.

                                    This week I would like to thank: Nial Bruce, Benjamin Davies, Steven Coffey, Kimberly Rieck, Naila, Dean, Neuterdude, The Lonely Sand Person, Joe Wilkinson, Sean Freeman who is  Blixa the cat, Frode Tennebø, Corinne Dmitruk, Gabriel Gauffin, Daniel Loosli, Kseniya Panfilenko, Alex Raine, Justin Proctor, David Gates, Arthur Latz-Hall, Eran Segev, Abraham Cottrill, Claudia Mastroianni, Kathleen Mattson, Matthew Horstman, Roland Warmerdam, Jeremy Kerwin, Saebre Lark, Tim Gerrish, Omar Del Rivero, Brent Kreinop, John, William Lauer, J. Alex Anderson, Roland McCoy, Mark Steven Rasnake, marco iarossi, Brian Kilby, Paul L. Hayden, Michelle Cullen, Aron Tannenbaum, Dustin A. Ruoff, Leigh Harborne.

                                    Thank you all so much for all you do. Because of you, we have Nancy, Beth, Rich, and Ally all running herd and keeping things running smoothly.

Fraser:                         Thank you everybody. And we will see all of you next week.         

Pamela:                       Bye-bye.

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Categories: Astronomy

Ep. 607: InSight and Marsquakes

Mon, 05/31/2021 - 1:57pm

Mars is cold and dead today, but the massive volcanoes tell us what the planet used to be like, millions and even billions of years ago. But how volcanically active is the planet today? That’s what NASA’s Mars InSight lander is there to figure out.

Download MP3 | Show Notes | Transcript

Show Notes

May 26, 2021 Total Lunar Eclipse (Blood Moon) (

Mars InSight Mission (NASA)

Volcanoes on Mars Could Be Active, Raise Possibility of Recent Habitable Conditions (Planetary Science Institute)

NASA’s InSight Detects Two Sizable Quakes on Mars (NASA)

NASA InSight’s ‘Mole’ Ends Its Journey on Mars (NASA)

Seismicity on Mars Full of Surprises, in First Continuous Year of Data Collection (Seismological Society of America)

Moonquakes (NASA)

Shallow moonquakes – How they compare with earthquakes (adsabs)

InSight tracks down the origin of two big marsquakes (Astronomy)

Tiny Volcanoes Are a Big Deal on Mars (Eos)

Volcanism on Mars (SDSU)

Shield Volcanoes (SDSU)

Stratovolcanoes (SDSU)

Cinder cone (USGS)

Intraplate Volcanism (SDSU)

Eruption Mar 2021 on the Reykjanes Peninsula: activity updates (Volcano Discovery)

Kīlauea (USGS)

Fissure-fed Flood Basalt Provinces (SDSU)

Krakatau volcano (Volcano Discovery)

Volcanic gases can be harmful to health, vegetation and infrastructure (USGS)

Curiosity’s Mars Methane Mystery Continues (NASA)


Mars MAVEN Mission (NASA)

ExoMars Trace Gas Orbiter (ESA)

A Biological Solution to the Mystery of Methane on Mars (Air & Space)


Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast episode 607 InSight and Marsquakes. Welcome to Astronomy Cast a weekly facts based journey through the cosmos, we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, 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 you doing?

Dr. Gay:                      I am doing well. I am sad though, there’s a lunar eclipse, there’s a missing moon in the sky that should be full that occurs next Wednesday and we don’t get to see it. But everyone –

Fraser:                         What do you mean we don’t get to see it?

Dr. Gay:                      Okay. Fine. Fine.

Fraser:                         I get to see it. Yeah.

Dr. Gay:                      I has a sad.

Fraser:                         I’ll report on whether or not the moon disappeared and whether it came back.

Dr. Gay:                      Excellent. Excellent. Remember to slam those pots or whatever you do in Canada to get the eclipse to end.

Fraser:                         Is that how that works?

Dr. Gay:                      I think so. That’s what I’ve been told.

Fraser:                         I’ve never done that. And I’m amazed that the moon is returned every time then. I didn’t know that it was on me. So, it’s gonna be an early morning one and the way things work, I can watch this from my bed.

Dr. Gay:                      That’s amazing.

Fraser:                         Yeah, yeah. So, I can just lay in bed and watch the moon go through the entire thing until morning and they get up for breakfast. Yeah, it’s perfect.

Dr. Gay:                      And those of you in Australia and New Zealand, you are smack in the middle of it and get the best view of all.  So, all of you wonderful humans down under go look at this for me, go look at this for me.

Fraser:                         Mars is cold and dead today. But the massive volcanoes tell us what the planet used to be like millions and even billions of years ago. But how volcanically active is the planet today? That’s what NASA’s Mars InSight Lander is there to figure out. All right, Mars InSight, volcanoes. Is there active volcanism on Mars today?

Dr. Gay:                      Maybe. And this is such a new result. We picked this topic before this science result was published through peer review. And it’s awesome when randomness like that occurs. There is a new paper out with lead author David Horvath. And it discusses how in Cerberus Fossae there appears to have been explosive volcanism as recently as within the last 50,000 years, 50,000.

Fraser:                         Wow. That’s soon. That’s recent.

Dr. Gay:                      That counts as active volcanism today. And what’s awesome is that location matches up loosely with where InSight has seen some well, seismic activity.

Fraser:                         Okay. So, I guess the answer then is maybe. All right. So, let’s go back to the beginning here. Now, I don’t know if we’ve actually done with − I haven’t done an episode on InSight in detail yet, I don’t think. So, can you just give a brief overview of what Mars InSight is there to do?

Dr. Gay:                      So, this is a fabulous little spacecraft that has proven that sometimes a world can defeat the most well-intentioned of spacecraft. InSight landed on Mars with two major missions. The first one was to put down a seismograph that would be able to detect faint earthquakes. And it’s such a sensitive seismograph that it can see the waves of an earthquake if everything is perfect, not just propagate through the world once but, actually bounce through multiple times.

And because of this, they can use a single seismograph to do the science that will require multiple seismographs to do here on Earth, where things are a little bit more noisy, because we have trucks and mining and things like that.

Fraser:                         I’m just kind of imagining this, that you’re getting some earthquake happening somewhere on Mars, InSight detects it and then also detects the reverberations of that earthquake – mars quake as it bounces around the interior of Mars.

Dr. Gay:                      Yes. And this is only possible because Mars doesn’t have oceans creating background noise, weather creating background noise, and all the activities of everything that is alive that create background noise. Now, it turns out that this has been harder than they thought. Because there’s still wind on Mars. So, one of my most amusing things to talk about when people are like, “We need to send humans to Mars because sometimes we have to be able to fix things.”

Well, they realize the wind was creating problems for the seismograph because the wind was picking the cable and just creating slight vibrations in the cable between the seismograph and the spacecraft. So, they’re now using the shovel that’s on an arm on the InSight to systematically bury the cable, as though they were playing in a sandbox. And it’s really delightful.

Fraser:                         Oh, I had no idea. Okay. And so, with InSight on the surface of Mars with its really precise seismograph, how much activity has it detected?

Dr. Gay:                      Well, Mars is pretty boring. And they haven’t been able to use the seismograph the entire time they’re there because they have a second instrument, the Mole. Didn’t work so well, it was supposed to dig itself under the ground a few meters. It determined that Mars dirt isn’t packed the way it can dig through but, it tried a lot. And when you’re hammering something into the ground, you can’t detect earthquakes, mars quakes, moon quakes, whatever kinda quake, there’s hammering going on, you can’t sense them.

So, during the time the seismograph has been used, they’ve seen a background of quakes that are very similar to the kinds of quakes that we see on the moon from a world just basically settling out over time. But they’ve also caught twice last season and twice this season fairly significant earthquakes greater than magnitude three, you would have been able to feel when you were there. Earthquakes during the northern summer and these earthquakes seem to originate up around a Lucien plateau, which is near where Cerberus Fossae is located.

Fraser:                         And so, a site that seems to be some of the most recent volcanic activity on the surface of Mars. Yeah, I think I’d read that in the last year they detected something like 300 or maybe 500 quakes. So, they’re detecting a quake a day pretty much. And as you said, magnitude two, magnitude three at the most, three point something, three point, yeah, two at the most at. So, nothing that dangerous, nothing’s gonna cause your Mars coffee to spill over.

Dr. Gay:                      And these quakes, they get divided in how they shake, rattle and roll into two basic categories. Quakes that behave very, very much like moon quakes. And those are those background quakes that they see on a regular basis. And then, there’s those two last year to this year earth-like quakes and those are the ones that are really fascinating.

Fraser:                         I’ll bite. I mean, as a resident of the West Coast, I am familiar with the unsettling experience of being in a fairly significant earthquake. So, what is an earth-like quake? How is that different from a moon-like quake?

Dr. Gay:                      So, when we have earth-like quakes it’s usually because there’s some sort of tectonic activity. It doesn’t have to be a moving plate. Iceland gets plenty of earthquakes due to the movement of magma beneath the surface. But essentially what you have is one chunk of planet decides it’s going to bulge out or it’s going to collapse down. And these motions within the rock can set waves moving through the surface and then through the core of the world.

Fraser:                         Right.

Dr. Gay:                      Now, the other thing that you have going on, which we also see on the moon is over time planets in general are just settling like a house is settling. You see things compressing, you see them responding to the constant shake of background meteorites hitting. And this slow settling causes its own background of earthquakes. And there’s nothing really exciting about this, just basically you build anything, you set it down and gravity will cause it to eventually settle into the most compact form it can be. And it takes time.

Fraser:                         I imagined you’ve got a ball of aluminum foil and you crunch it up into a ball as tightly as you can and you give it to someone stronger than you and they crunch it even tighter. And then, use some tool, a hammer to crunch it even tighter and you just got this settling where the objects just getting smaller and smaller and smaller.

Dr. Gay:                      I don’t know if you’ve ever had a precarious pile of things, for me this is usually dishes.

Fraser:                         I believe I have some around me right now.

Dr. Gay:                      Yeah. And they seem to be more or less stable in a Jenga game kind of competitive manner. And all of a sudden, you see nothing obvious going on and they’re like, “And now we’re going to switch to a lower potential.” And things move and this could be there was a breath of air, this could be that there was a tremble in the ground so small you didn’t feel it. And that tiny change to the environment was enough to take something over the edge from static friction holding it in place, to kinetic energy taking over.

Fraser:                         So, when we look at the huge volcanoes on Mars today. We’ve got Olympus Mons and the other three Mons. They’re just absolutely enormous volcanoes bigger than anything else that we know of in the in the solar system. The height is ludicrous. Clearly an enormous amount of material was pouring out of these at one point. When do we think that they died?

Dr. Gay:                      So, those massive, massive volcanoes that clearly look like volcanoes probably died billions of years ago, which is quite sad. But just like we have a variety of different kinds of volcanoes here on Earth, it turns out that Mars had a variety of different kinds of volcanoes there. When we look at the massive shield volcanoes, we can imagine pyroclastic flows going down their sides and everything just building up over time and ash getting shot into the – well escaped velocities with some of those volcanoes.

What we’re looking at with Cerberus Fossae instead is more like the ground open up and lava explosively came out of it, sort of like what we’re seeing happening in Iceland right now. And the ground cracked open and spit lava. This is explosive volcanism. And it leaves a very different marking on the surface and the images that are associated with the most recent volcanoes identified. What you see is this odd dark splotch on the ground, kind of like a pinched off oval and it’s that splotch that is the most recent lava that overlays all the other lava in the region and has so few craters that they appear young.

Fraser:                         And so, then to compare how that all looks to what we’re seeing these features in the Cerberus Fossae. Is that right? Cerberus Fossae?

Dr. Gay:                      Cerberus Fossae. Yeah.

Fraser:                         Yeah. What did those features look like as a comparison of – as I said, we know are clearly ancient volcanoes and now we see some of these more recent. What are we seeing?

Dr. Gay:                      Those are the explosive volcanoes. The ground cracked right here, oozed out a bit, and then, stopped. It didn’t bother to build mountains, it didn’t bother to build enormous structures, there’s just a dark splat across the Mars.

Fraser:                         Right. So, what makes the scientists think that this is fresh-ish?

Dr. Gay:                      So, we get at the age of things on Mars by looking at how they’re layered on top of each other. So, you have for instance, a field of non-duney surface. So, you’re seeing old surface and it’s covered in craters. The more craters you have, the longer that ground has been there exposed to space, waiting for things to crater it. Overlaying on top of this ancient surface, we periodically see things like water features, canyons, valleys, stream beds, ponding, shores, tsunami lines. All these things are on Mars.

We also see layered on top of things, volcanic activity, the tongues of lava that cut across the world. So, by looking at how you have this underlying maximum number of craters terrain. Layered on top of that you have various tongues of lava, streams of material and craters are through all of this. The places that have the smallest number of craters are the youngest. So, when we look at sand dunes that are still sweeping across the world, changing from season to season, those areas have almost no craters at all.

Sometimes they have no craters for the smaller sand dunes. That’s a young place. In this case, we have lava that is inplaced over other lava, has negligible numbers of craters, and everything lines up between what is the age of the material it’s on top of? How much stuff does it have trying to be on top of it? It seems to point to it being just 50,000 years or less.

Fraser:                         And so, if you could have been there whenever it happened, what would you see?  I’m familiar with different versions of volcanoes. I think about what you see in Hawaii with Kilauea, with big blobs of lava pouring down the landscape. I think of things like Mount St. Helens, which are more explosive.

Dr. Gay:                      Yeah, nothing that exciting. So, this would have been the ongoing volcano, currently erupting near Reykjavik, I am not going to attempt to pronounce the volcano’s name. I’m sorry, humans.

Fraser:                         Something “jokall”.

Dr. Gay:                      I don’t hear the sounds well enough to try and make the sounds and I will admit to that. There’s an ongoing eruption near Reykjavik where, basically a section of ground started spewing lava out of it and it’s slowly building up hills, it’s filling up a valley. But it’s never going to become a mountain unless it lasts for longer than anyone can imagine.

Similarly, a few years ago on the Big Island of Hawaii, the volcano there decided it wasn’t going to erupt out of its crater for a while and instead decided to eat a subdivision. And those cracks in the ground that spewed lava and ate people’s backyards and homes. That kind of a cracking, open lava explosively coming out of the ground that again is more the activity that we’re looking for.

Fraser:                         Right. And so, how close could you get and be safe, do you think? Would you wanna be kilometers away from it? Would you wanna be a few 100 meters away from it? Would it be spraying –

Fraser:                         And I wonder how it be behaving? Sorry, I got a million questions.

Dr. Gay:                      Right. So, I respect your million questions. And I love volcanoes.

Fraser:                         I know. I think that you were one geology class away from becoming a geologist and not an astronomer.

Dr. Gay:                      Well, I never took a geology class ever.

Fraser:                         So, if you had taken the geology class early on when you were doing your science degree, you could very well become a volcanologist. I’m just putting that out there.

Dr. Gay:                      So, I think that just like I love biology and animal science, but I recognize that I’m sufficiently dyslexic that I shouldn’t try to take that many chemistry courses.  I suspect that there is enough mineralogy and volcanism that I would have fled. But this is a lesson to all of you, you can be learning disabled and still get a PhD in science. Just know your limits.

Fraser:                         Yeah. So, I guess where this is all coming to is just, how active – if it was 50,000 years ago, that’s fresh. That’s now essentially. So, could there be another eruption on the surface of Mars any day now? Almost inevitably?

Dr. Gay:                      Well, probably not any day now, because the earthquakes would have been much more interesting if something was about to blow. But could there be conceivably another event? I’m gonna go with – I’m not gonna say no to that. And where I took pause and trying to answer all your questions is, I honestly don’t know how the significantly lower gravity and less atmospheric pressure is going to change the safety radius around a volcano. It’s gonna be a whole lot easier for any volcanoes on Mars to fling things in your direction. So, maybe give them a little more space than you’d give the same volcano here on Earth.

But this wasn’t a, “destroys an entire island like Krakatoa” kind of event. And it’s the thing where I can imagine being a couple of Mons away, looking across the valley, and seeing it off in the distance completely safe and edging your way forward. With all of your detectors trying to figure out what are the limitations on this new world.

Fraser:                         We’ll just remember in the 1/3, gravity, any blocks and boulders thrown into the air will travel triple the distance, so.

Dr. Gay:                      This is why you start out a couple mountains away.

Fraser:                         Yeah, start faraway and see what happens. And so, if there was some ongoing or future activity, what do you think InSight would detect? What would it look like?

Dr. Gay:                      So, what has me so excited is it’s not just InSight that could potentially be detecting things. So, inside` if there was suddenly going to be a pressure release in the form of magma oozing forth, you’d see building up earthquakes is essentially the pressure builds, and builds, and builds, just like we see in Iceland and in other places. But in addition to that, you’d see outgassing. And what fascinates me about this and I haven’t been able to find a paper discussing this new enough to take in InSight and Horvath’s work.

We have in the past detected methane during the summer months on Mars.

The two pairs of earthquakes that have been observed have been observed in the summer. And this is consistent with what we see on Earth, where when you release the added pressure of having things frozen, it liberates things to erupt. And so, we’re seeing the summertime release of methane, the summertime quakes, which point to geologic activity that I had been so hopeful was biologic activity in the past. So, now we have even more questions.

We have even more questions. So, now we need to do more work to figure out does TRACE, does MAVEN, do these gas detectors detect gas tied to the seismology?  So, do you see more methane when you see more earthquakes? Or is it different parts of Mars? And these are the things that we now need to start figuring out. The universe loves yes, and. The universe is all about improv.

Fraser:                         Right. Yeah. So, I’m just imagining this idea that you’ve got this volcanic activity that’s pinpointed roughly by InSight and that tells you that some volcanic outgassing probably happened in that region. And so, then you try to target TRACE or some other spacecrafts that’s watching the atmosphere to see if you see a buildup of methane in that region and if you do, sorry life.

Dr. Gay:                      Well so, this is where the yes, and is so important, is I think we need to one, be paying attention to those northern low lands where Lucien Phoenicia and Cerberus Fossae are located, this vast area that’s thought to perhaps be a crater. We need to be paying attention to it to see what methane is there. But then we also need to do controls, go look at the highlands somewhere. Go look someplace absolutely still and see what is it’s methane over time. There’s a lot to understand. And all because there’s geologic methane doesn’t mean there isn’t also biological thing.

Fraser:                         Right. Which is somewhat, I mean exciting but, also frustrating, because we imagine it’s going to be one thing or the other. And then our science will tell us whether it goes one way or the other. But the inevitable possibilities, that it’s a delightful blend of all of them. And as you say, yes, and.  So, is it volcanic activity? Yes. But is it also biological activity? Maybe. We still can’t rule it out. So, yeah.

Dr. Gay:                      Yeah. I wanna say yes. I have no reason to say yes, I wanna say yes.

Fraser:                         Of course, but yeah, but I love that. The answer is always more complicated than you thought and–

Dr. Gay:                      The universe is more creative than we are.

Fraser:                         Yeah, yeah. And so, we go into with these really simplistic ideas and when we walk out with is complicated questions. Right?  And then, we try to get the answers to those. And it turns out that those are complicated questions and so on. We’re never finding answers. We’re just finding better questions. And I think that’s science.

Dr. Gay:                      It’s a wonderful path forward. And we’re just gonna have to yes, and our equations too

Fraser:                         Right. Thanks Pamela.

Dr. Gay:                      Thank you.

Fraser:                         All right. Do you have some names for us this week?

Dr. Gay:                      All right. So, as always we are here thanks to the generous contributions of people like you. You allow us to pay the cat herders and make sure they have medical benefits.

And without Nancy, Beth, Allie, Rich, all those humans behind us, we would not be here for you. So, thank you and this week in particular, I wanna thank Rayvening, Allen M Price, Marek Vydareny, Mark Van Kooy, Ben Floss, Elad Avron, Phillip Walker, Matt Rucker, Joshua Adams, Nate Detwiler, David, Gregory Singleton, Karthik Venkatraman, Chris Scherhaufer, VocalWarrior24, Cooper, Gfour184, Sarah Turnbull, Scott Bieber, Don Mundis, Paul D, Disney, Matt Newbold, Jen Greenwald, Dave Lackey, Lew Zealand. I’m gonna need reading glasses for some of you.

Fraser:                         I love this. This is the best.

Dr. Gay:                      Dean McDaniel, Father Prax, Andrew Stephenson, Kenneth Ryan, Steven Shewalter, Bart Flaherty, Anitusar, Rachel Fry, Cemanski, Tim McMackin, Matthias Heyden, Glenn McDavid, Planetar, Antony Burgess, Shannon Humber, The Air Major. Thank you all.

Fraser:                         Wow.

Dr. Gay.                      Thanks all of you for everything you do.

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

Dr. Gay:                      Bye-bye.

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, 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 This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at 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 Astronomy Cast.

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Categories: Astronomy

Ep. 606: Time Dilation – Skipping Through Time

Mon, 05/24/2021 - 4:05pm

Have you ever wanted to be a time traveler? Good news! You’re time traveling right now. Into the future at one second per second. Too long? Don’t want to wait? Good news, Einstein’s got you covered. Today, let’s talk about the weird world of time dilation.

Download MP3 | Show Notes | Transcript

Show Notes

What’s Up: Mercury at Sunset and Nova in Cassiopeia (CosmoQuest)

Harvard Science Center (Harvard)

What is relativity? Einstein’s mind-bending theory explained (NBC Mach)

How “Fast” is the Speed of Light? (NASA)

The Theory Behind the Equation (PBS)

Buck Rogers in the 25th Century (IMDb)

How does relativity theory resolve the Twin Paradox? (Scientific American)

Landmark NASA Twins Study Reveals Space Travel’s Effects on the Human Body (

International Space Station (NASA)

Speed and Velocity (Math is Fun)

COMIC: Gravity Wells (xkcd)

How to Make Your Own Gravity Well (Saint Mary’s University)

Interstellar (IMDb)

The Expanse (IMDb)

How Fast Do Spacecraft Travel in The Expanse? (Wired)

Momentum (The Physics Classroom)


Transcriptions provided by GMR Transcription Services

Fraser Cain:                Astronomy Cast Episode 606: Time Dilation. 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, publisher of Universe Today. And with me as always is Dr. Pamela Gay. A senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how you doing?

Dr. Pamela Gay:         I’m doing well. It is a glorious spring day. And while the stars don’t shine as many hours each night, it is great to have Mercery over on the horizon. Have you gotten out to go look at it yet?

Fraser Cain:                I thought we went through this. I can’t see Mercury. I have no view to the East and I have no view to the West. Mercury is – I’m just gonna have to take it on faith that Mercery even exists.

Dr. Pamela Gay:         Okay. I understand. I am going to have to go to a field somewhere.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         Because I, too, have no horizon. But I have access to cornfields that don’t yet have much corn in them.

Fraser Cain:                The only time I’ve ever seen Mercery I was in Australia. That’s it. And you have the benefit that the ecliptic sort of rise is straight overhead in Australia. So, you know, as opposed to things here being very low down to the horizon.

Dr. Pamela Gay:         Right.

Fraser Cain:                But yeah. And so, someone was like, “Oh, yeah. And there’s Mercery.” And I was just like, “This is the first time I’ve ever seen Mercery.” Too great.

Dr. Pamela Gay:         I think I have seen it from the roof of a building at Harvard. The Science Center in Harvard Yard – or just outside Harvard Yard – has a small telescope on its roof that I used to work with. And light pollution always makes it questionable if you know what you’re actually looking at. Because there just aren’t enough stars. But I think I’ve seen it, but now that I live someplace darker, I’m gonna try again.

Fraser Cain:                All right. So, if people wanna see Mercery and they do have, oh, I dunno, a horizon …where and when should they look?

Dr. Pamela Gay:         So, if you go out right now it is located between the very, very bright Venus and the super-thin crescent moon. The moon’s getting higher and higher, and thicker and thicker each day. But it remains above Venus in the West/Northwest. So, go out –

Fraser Cain:                Just after sunset.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                Okay.

Dr. Pamela Gay:         Venus will pop out brightest and then look up.

Fraser Cain:                Have you ever wanted to be a time traveler? Well, good news. You’re time traveling right now into the future at one second per second. Taking too long? Don’t wanna wait? Good news. Einstein’s got you covered. Today, let’s talk about the weird world of time dilation. All right, Pamela. Time dilation. What?

Dr. Pamela Gay:         So, one of my favorite things that was like this breakthrough understanding for me with relativity. Was the understanding that no matter who you are and what you’re doing the speed of light will appear exactly the same. And in order for that to happen, how you perceive time has to change.

So, the way to think about this is what we’re used to in day-to-day life is …if I’m standing on side of the road in front of my house. And a car zips by, it appears to zip by at 30 miles per hour if they’re following the law. Now, if I’m going down the road at 30 miles per hour, the car in front of me – in theory, if they’re following the law – should appear to be moving zero miles per hour relative to me.

Fraser Cain:                Right.

Dr. Pamela Gay:         And so, we’re used to seeing everything with relative speeds. The faster I’m going, I’ll see people on the side of the road appearing to go in reverse. People around me, I see their motions relative to my own. So, it seems like using that human experience that the faster I go, I should eventually be able to catch up to those photons and perceive them as moving side by side with me.

But the reality is that while some outside observer might somehow perceive me and those light particles going at almost the same speed. I will never go as fast as the light. I will never see that. I will always see light. At the exact same speed relative to me.

Fraser Cain:                And that is such – I mean, when you think about Einstein’s ability to perceive the world in a fascinating way. To have this thought experiment that you’re traveling almost at the speed of light. And then you shine a flashlight, and you watch the flashlight. And in your mind, you be like, “Well, do I see the photons speeding away –

Dr. Pamela Gay:         Right.

Fraser Cain:                – just a little faster than me or do I see the photons speeding away at the speed of light?” And the only way – if you see them at the speed of light – is if time itself is changing.

Dr. Pamela Gay:         And so, this brings up that bizarre reality that Buck Rogers in the 21st century is actually a possible outcome of someone orbiting at a high enough velocity. Now, the fact that orbital mechanics doesn’t allow you to zip around the planet that fast. Let’s say instead they put themselves in this massive orbit at super high speeds.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         That’s more realistic. Orbit around the sun instead. But …well, good ole Buck Rogers perception of time will slow.

Fraser Cain:                Okay. So, then you talk about this idea of speed. So, let’s break down time dilation. And I mean, I wanna ask why is time dilation? But I know the answer. And the answer is because. Right? Relativity. Because that’s how the universe works. So, let’s proceed right past ‘why’ and go straight to ‘how.’ How time dilation? And there’s sort of two factors. Two ways that you can get time dilation. And the one is the speed.

                                    So, let’s break this down in some examples. And now you’re providing this example. The twin paradox is the classic one, right?

Dr. Pamela Gay:         Yes.

Fraser Cain:                We’ve got two people. One here on earth. One gets in the spacecraft. What happens next?

Dr. Pamela Gay:         Well, so we actually got to see this with the Kelly twins. And the reality is that the astronauts on the International Space Station are experiencing time ever so much slower. And the way you figure out who experiences the change in time is you look to see who experienced the force. And who experienced that acceleration that got them to that faster velocity.

                                    So, in this case, you accelerate yourself up to the International Space Station and to a velocity that keeps you circling the planet instead of falling back. And time slows.

Fraser Cain:                Right. And in that sort of very slightly –

Dr. Pamela Gay:         Yes.

Fraser Cain:                And it’s more complicated because of course the International Space Station and the twin who’s on the ground are in a gravity well. But let’s say you have the one who accelerates up to close to the speed of light. Flies for 10 years, and then returns. And then the twins meet up. So, what you’re saying is that it’s not the speed.

Dr. Pamela Gay:         Yes.

Fraser Cain:                It’s the acceleration that you experience to get yourself up to that speed.

Dr. Pamela Gay:         That determines who is the one who is experiencing the time change.

Fraser Cain:                Got it.

Dr. Pamela Gay:         It’s the velocity that you accelerate to that determines how much time slows down.

Fraser Cain:                Right. And so, twin No. 1 is sitting on earth. Twin No. 2 gets in a spacecraft. They accelerate – and that’s the key – to close to the speed of light. Compared to the twin who’s just sitting on the planet.

Dr. Pamela Gay:         Yes.

Fraser Cain:                They then return – it’d take them 10 years. Or I guess the person traveling experiences 10 years and returns home to earth to see that the twin who was on earth has experienced –

Dr. Pamela Gay:         Death

Fraser Cain:                – vastly more time.

Dr. Pamela Gay:         Death.

Fraser Cain:                Right. Right.

Dr. Pamela Gay:         Humans only live so long. The human on earth –

Fraser Cain:                Sure. Right.

Dr. Pamela Gay:         – experienced death.

Fraser Cain:                Right. And so, the twin  – so, I just want to be sure I got this clear. So, the twin who flies on the spacecraft experiences 10 years. The twin who stayed on earth experiences hundreds, maybe thousands, maybe millions of years.

Dr. Pamela Gay:         Essentially, the closer you get to the speed of light. The closer you get to stopping time for yourself while time passes for those on earth.

Fraser Cain:                Right. Because you’re experiencing the acceleration.

Dr. Pamela Gay:         Well, and so the key is who is the one whose time stops for?

Fraser Cain:                Right.

Dr. Pamela Gay:         We always see things in our frame of reference. And this is where that car idea is important to think about. So, relative to me standing on the sidewalk and the Uber driver zipping down the street. The Uber driver, if they perceive themselves as not moving. Will see me moving at 30 –

Fraser Cain:                Right.

Dr. Pamela Gay:         – miles per hour. So, if you have two spaceships in space it’s harder to sort out who’s the one moving and not than it is on earth.

Fraser Cain:                Right.

Dr. Pamela Gay:         And clearly, compared to the trees, the ground, and everything else, I’m not moving. But in the vastness of space, you stick two spacecrafts down and throw the rockets on one and don’t tell the people on board who is having the rockets thrown. You might feel it. But you can also say, “Hey, we just spun your spacecraft so you felt gravity.” So, the two could experience the same thing.

Fraser Cain:                All right. So, we talked about speed/velocity as one. And I gotta be careful, right? Because I’m using speed/velocity interchangeably. And that is bad physics, Fraser. Bad. So, velocity. Right? Velocity is speed and direction.

Dr. Pamela Gay:         So, in the equations to figure it out, they use the scalar velocity. Which is the speed.

Fraser Cain:                Okay.

Dr. Pamela Gay:         And so, for figuring out how much time has changed you can just say speed.

Fraser Cain:                Okay. Okay. All right. So, we talked about speed.

Dr. Pamela Gay:         Yes.

Fraser Cain:                And the other way is to be in the presence of a gravity well.

Dr. Pamela Gay:         It’s true. It’s true.

Fraser Cain:                And I think we’re all really fortunate because Interstellar came out a couple of years ago. And they had this happen. And so, we got to see what it did. So, what’s going on with that.

Dr. Pamela Gay:         So, the closer you get to a massive object. The way to think about it here is in a normal situation down on the planet earth, if I throw a ball slightly, I see it moving at one speed. If I throw it really hard I see it moving at another speed. And then, if I go to Jupiter and I use the exact same amount of force to throw the exact same amount of balls. They’re gonna move much slower. Because more –

Fraser Cain:                Right.

Dr. Pamela Gay:         – gravity. Now, for a poor innocent little light particle trying to escape from the super high-mass object, that light particle is experiencing all that gravity. And in order for that light particle to continue always moving at the same speed of light, time is gonna have to change as it escapes from different gravity wells.

Fraser Cain:                Right. Okay. And like we saw – you know I was talking about this idea of watching the movie Interstellar. And we saw how in Interstellar he goes down to the surface of this planet that’s orbiting around this supermassive black hole. He’s there for a day. Comes back out and the rest of the universe – the rest of his family – has experienced 80 years. Or some ridiculous amount of time.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                And so, it was not because of the speed they were doing to go through the wormhole and blah blah blah. It was because they spent this time close to the black hole in the gravity well. And so, I think, going back to that conversation that we had about the acceleration is the key.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                When you’re in a gravity well, you’re experiencing acceleration.

Dr. Pamela Gay:         Yes. It’s the – what is doing the fundamental altering of your movement through space and time. And that gravity well is doing its darndest to keep you attached to it.

Fraser Cain:                Right.

Dr. Pamela Gay:         And to keep that light attached to it.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         And the more the gravity pulls on you and light, the more time has to slow down so that light is always perceived as going at the same tick.

Fraser Cain:                Right. Right. Okay. So, now let’s put this all together. What if you are in a gravity well. Say you’re orbiting a black hole. And you’re also going very quickly compared to somebody who is going – I guess a black hole is a bad idea because you’ll be standing – but let’s say you’re on the earth. Right? I mean, but this is a practical example that we can actually do.

Dr. Pamela Gay:         Yes.

Fraser Cain:                Where you are on the surface of the earth.

Dr. Pamela Gay:         Yes.

Fraser Cain:                And so you’re in the presence of a gravity well.

Dr. Pamela Gay:         Yes.

Fraser Cain:                Or you’ve got your twin who’s flying in space on the International Space Station. They are in less of a gravity well because they’re at a higher orbit. But they’re moving faster.

Dr. Pamela Gay:         Yes. And to be fair, I haven’t redone these calculations in ages.

Fraser Cain:                Yeah, I haven’t either, and I apologize. Because it’s not in my head.

Dr. Pamela Gay:         So, last time I did these calculations, assuming I did them correctly – and I really hope I did. What I figured out was time goes more slowly for the astronaut, because the time dilation effect compared to being on the ground is greater for them. Because of the amount of acceleration that went into getting them where they are. Whereas, if you stopped them in space, this would cause them to fall to the earth. So, don’t do this.

Fraser Cain:                Right.

Dr. Pamela Gay:         And compared the time dilation due to their lesser pull from the center of the earth. But they’re still being pulled on, just less.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         But the dilation caused by the lesser pull at altitude compared to the surface of the planet – that time dilation due to gravity is a smaller effect than the time dilation due to accelerating so they don’t fall.

Fraser Cain:                And there’s gotta be like a perfect balance.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                Where you essentially experience no difference in time compared to the person who’s on the surface of the planet. Because your speed of movement balances perfectly out. The fact that they’re in a greater gravity well. And so you –

Dr. Pamela Gay:         And this would be a great homework problem.

Fraser Cain:                Yeah, there you go.

Dr. Pamela Gay:         And right now everyone is very glad I am not still teaching physics for engineers who get calculus.

Fraser Cain:                You would assign it.

Dr. Pamela Gay:         Because yeah…

Fraser Cain:                Yeah.

Dr. Pamela Gay:         You should be able to totally calculate out what density planet do you need? So, that someone on the surface and someone safely in orbit have the exact same ticking of the clock. Although, you can never sync those clocks. Because it takes time for light to get between the two points. But the ticks are the same duration tick.

Fraser Cain:                All right, so now I wanna blow peoples’ minds. And –

Dr. Pamela Gay:         I love time dilation. I just wanna say that –

Fraser Cain:                Yeah. Yeah. Yeah.

Dr. Pamela Gay:         – I absolutely love this concept.

Fraser Cain:                Yeah. Absolutely. And so, one very popular science fiction show that’s come out in the last little while is The Expanse. And they have these really powerful fusion rocket – Epstein rockets – that are able to take your spacecraft really, really fast. And so, if you could just jam on the engine and you had an unlimited fuel supply somehow. And you just kept accelerating, accelerating, accelerating …what would happen to time for you and the rest of the universe?

Dr. Pamela Gay:         Your time, by your perception, your heart would continue to beat the exact same way. But –

Fraser Cain:                You’d continue to be pressed into the seat at 1g.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                Right?

Dr. Pamela Gay:         Yeah. But the more your velocity increases …and here it’s the absolute value of it, that speed, the nonvector, scalar portion that matters. With each moment of acceleration, the moments that an outside observer sees you experience become fewer and fewer.

Fraser Cain:                Right.

Dr. Pamela Gay:         You will stop aging over time. You will stop breathing to the person watching because everything is slowed down so absolutely much. And in other science fiction series – I’m thinking of Hyperion here. There’s this wonderful example of in the future when high-speed travel between solar systems becomes practical. People of means can deposit their money and invest it in good things. And then skip through time become wealthier and wealthier. And experiencing less and less.

And I mean, imagine just how hard it would be on one hand to pop out of space travel and see all the amazing technological changes that have occurred. But at the same time be like, “And I’m rich now.”

Fraser Cain:                But the part that’s kinda crazy is that you could keep on accelerating and from your perspective you would never reach the speed of light. Because it’s impossible. But you would still be experiencing 1g of acceleration for days, months, years, decades.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                And even though, if you did the math, and you’re like, “I should have gotten faster than the speed of light.” You won’t and yet the distances that you’ll be traveling and the time that the rest of the universe will be experiencing just continue to grow.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                For as long as you can keep this going.

Dr. Pamela Gay:         And crazy things start to happen that we’ve discussed in other episodes many years ago. So, go digging through the archives. The way the equations for relativity work out is your momentum increases in ways that aren’t entirely linearly related to your mass. And the impact of this increase momentum, the faster and faster you go, is that it’s like you were gaining more and more mass.

Now, the reality is the number of atoms in your body will not change unless biological things occur. But your ability to destroy things if you hit them increases because of this apparent change in mass that is due to the relativistic effects on your momentum.

And this led to a question with which I broke a physicist and never really got a good answer. They sort of ended up walking away mumbling. And the question was if a body of mass goes fast enough so that its equivalent mass via momentum is such that it would be a black hole is it actually a black hole?

Fraser Cain:                Right.

Dr. Pamela Gay:         And the answer I’ve gotten from other theorists was no –

Fraser Cain:                No.

Dr. Pamela Gay:         – that’s crazy talk.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         But I did break one physicist –

Fraser Cain:                Good.

Dr. Pamela Gay:         – this way. I was proud of myself.

Fraser Cain:                So, the part that’s crazy is that if you could keep this acceleration up, you could be going to the point that in like a decade you would cross the Milky Way. In two decades you would go to Andromeda. In three decades you would be billions of lightyears away. And in about less than a human lifetime you would travel more than the distance to the edge of the observable universe.

Dr. Pamela Gay:         But the problem is the amount of energy that it takes –

Fraser Cain:                Of course.

Dr. Pamela Gay:         – to keep accelerating your –

Fraser Cain:                Yeah.

Dr. Pamela Gay:         – increasing effective mass. Not your actual mass increasing.

Fraser Cain:                Yes.

Dr. Pamela Gay:         Your effective mass increasing.

Fraser Cain:                Yeah.

Dr. Pamela Gay:         You would exceed the mass-energy of the universe before you exceeded the speed of light. Which is part of how we never actually go faster than the speed of light.

Fraser Cain:                Yeah. And so for someone watching you. You would just be very close to the speed of light. And you’d be doing that for billions of years.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                From your experience because you’re continuing to accelerate you would be like .999999% the speed of light. And so, it would take you two and a half million years to get to Andromeda. It would take you –

Dr. Pamela Gay:         Right.

Fraser Cain:                – 46 billion years to get to the edge of the –

Dr. Pamela Gay:         But you wouldn’t experience it.

Fraser Cain:                But you wouldn’t experience it. And yet the rest of the universe would. And so you would be – you would have to wait. You know, we’d have to wait 50 billion years for you to reach what was the edge of the observable universe. It’s absolutely mind-bending.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                And awesome. And it’s like this one hope that we can travel vast distances in a single human lifetime. Although, you have to say goodbye to everyone and everything you know.

Dr. Pamela Gay:         Well, just travel with your friends. Travel with your friends.

Fraser Cain:                That’s a good way to do it. All right. Thanks, Pamela.

Dr. Pamela Gay:         Thank you.

Fraser Cain:                Do you have some names for us this week?

Dr. Pamela Gay:         I do. I need to find the right window. I have so many monitors. I love my monitor fort.

Fraser Cain:                Your monitor fort.

Dr. Pamela Gay:         I have a monitor fort.

Fraser Cain:                Yeah. That’s awesome.

Dr. Pamela Gay:         This is what one should build – monitor forts.

Fraser Cain:                Yeah. Yeah. I love it. I’ve never heard it said that way, and I think it’s great.

Dr. Pamela Gay:         So, as always, we are here thanks to you. You out there, thank you. Thank you for supporting us and making everything we do possible. For allowing us to pay Rich, Allie, Beth, Nancy. All the people that keep Fraser and I on the straight and narrow. Because Lord knows we need herded. So, thank you for making this possible. Thank you for paying our server bills …our everything else. Thank you.

And this week in particular I would like to thank Kevin Parker, David Truog, Bill Nash, Helge Bjørkhaug, Richard Hendricks, Janelle Duncan. And it turns out that because it’s the end of the month, those are the only names I’ve got.

Fraser Cain:                Okay.

Dr. Pamela Gay:         So, thank you.

Fraser Cain:                Thanks, everybody. And thank you, Pamela. And we’ll see you next week.

Dr. Pamela Gay:         Buh-Bye, everyone.

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. 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

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