The Dark Universe: Exploring the Euclid Mission with Jason Rhodes

What are dark energy and dark matter? Neil deGrasse Tyson and comedian Chuck Nice learn about the Euclid Mission and our latest efforts to uncover the secrets of The Dark Universe with JPL Researcher, Jason Rhodes.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Neil deGrasse Tyson?

  Coming up on StarTalk, we speak to my friend and fellow astrophysicist, Jason Rhodes. He works for NASA's Jet Propulsion Laboratory, and he's one of the world's experts on dark energy, the detection of dark energy. He's one of the principal scientists on the European Euclid mission that'll attempt to do just that. So, what is dark energy? How does using balloons help us get there? And more, coming up on StarTalk.

• 0:32Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:45Neil deGrasse Tyson?

  This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. I got with me my co-host, Jack Nice. Jack?

• 0:52Chuck Nice?

  Hey Neil, what's happening?

• 0:54Neil deGrasse Tyson?

  Yeah, today, I think, is one of the hottest topics in all of science.

• 1:00Chuck Nice?

  Yes.

• 1:01Neil deGrasse Tyson?

  We want to figure out what dark energy is, who made it, where's it coming from, where's it going, and will we all die? Will we all die?

• 1:10Chuck Nice?

  Once, once we find out what it is, the universe can't tell us unless it kills us.

• 1:16Neil deGrasse Tyson?

  Unless it kills us, unless it kills us. We've got with us for this episode, my friend and colleague, Jason Rhodes. Jason, welcome to StarTalk.

• 1:24Speaker 02

  Thank you for inviting me. I'm really looking forward to talking about dark energy with all of you today.

• 1:29Neil deGrasse Tyson?

  Yeah, yeah. So you, you hail from the Jet Propulsion Labs. We all know that's in Pasadena, California. It's a branch, one of 10 branches of NASA, and JPL's affiliated with Caltech. And so that makes sure you all are doing the right things. All right? No slouching.

• 1:48Speaker 02

  That's right. We have two bosses here, Caltech and JPL. So, or sorry, Caltech and NASA.

• 1:54Neil deGrasse Tyson?

  And NASA, and NASA, so, and, and JPL, right?

• 1:58Speaker 02

  That's right, yeah.

• 1:59Neil deGrasse Tyson?

  NASA headquarters, JPL headquarters, eh, okay. So, no, no, no slouch in there. So, your, your research interest, what I like about you for this conversation is, you not only have deep interest in dark energy, which we'll get to in a minute, which we all do, but you also, you're not just talking about it. You're actually trying to solve the problem using experiments, using telescopes, detectors, balloons. And I want to get into how all that works. How could a balloon launched from Earth tell you anything about dark energy in the universe?

• 2:34Speaker 02

  Unless it's a Chinese spy balloon.

• 2:37Neil deGrasse Tyson?

  Oh, those!

• 2:38Speaker 02

  Hey, those balloons are able to tell you a great deal.

• 2:44Neil deGrasse Tyson?

  Alright, so first tell me, just remind us all what dark energy is and how you got into it?

• 2:49Speaker 02

  Well, uh, dark energy is really the name we give to our ignorance of what's causing the universe to expand faster and faster over time. And about 25 years ago, uh, two groups of scientists were trying to understand how fast the universe was expanding and how, how that, uh, expansion was slowing down due to gravity. And so they were doing these experiments and they almost simultaneously came up with the same result, which was very surprising. It was not slowing down due to gravity, but instead that expansion was speeding up as if something was pushing the universe apart. And they gave the name of whatever that is, uh, dark energy. And we are still 25 years later trying to figure out what that dark energy is, where it comes from,

• 3:35Speaker 02

  and what it's gonna do to the universe in the future. And right now, we think dark energy is the dominant component of the universe and it is only gonna become more dominant over time in the future.

• 3:45Chuck Nice?

  So, this is an invasion, what you're saying. We're absolutely being taken over. We're being, yeah, we're being taken over by this force.

• 3:54Speaker 02

  We really are, and if you look back, uh, deep into the universe's history 10 billion years ago, dark energy was a very sub-dominant, small component of the universe. Uh, now it's the dominant component of the universe. And as I said, 10 billion years or more from now, it's gonna be even more dominant, where the universe is completely dominated by this dark energy. But it really is an invasion.

• 4:17Neil deGrasse Tyson?

  Well, if we're, if the universe is expanding and getting thinner...

• 4:22Neil deGrasse Tyson?

  How do you get more of something?

• 4:24Speaker 02

  That is a really interesting question for us to ask. So, one of the theories of dark energy is maybe it's a property of spacetime itself. And that is, when there's more spacetime, there's more dark energy. And as there's more dark energy, it's causing spacetime to expand faster and faster, making more and more dark energy in this sort of runaway effect. And for some-

• 4:48Chuck Nice?

  It's self-propagating, is that the deal?

• 4:50Speaker 02

  A little bit like that. And for some physicists, they don't like this because it really sounds like a violation of the conservation of energy. We're getting more dark energy over time. So, if we think of dark energy as energy in the classical Newtonian physics sense, we're really not conserving energy in the universe, which is a very distasteful concept to some physicists. On the other hand, the equations we're using to describe dark energy are just equations that have been around for 100 years, come from Einstein, and they seem to fit the universe. So, the universe is telling us something very profound here.

• 5:30Chuck Nice?

  It's telling us something profound, but it's also contradicting something profound at the same time. It's very much like being in a weird relationship, you know, where you don't know what to do.

• 5:44Neil deGrasse Tyson?

  I would say you're allowed to contradict something profound with something equally as profound. And then, you know, put it in the octagon and let it sort itself out.

• 5:54Chuck Nice?

  Nice. I like that.

• 5:58Chuck Nice?

  Two postulates enter, one postulate leaves.

• 6:03Neil deGrasse Tyson?

  So, if the universe is expanding, then the gravity is thinning. So, the dark energy is becoming ever more powerful regardless. And relative to gravity, it's getting that much more powerful. So, gravity doesn't stand a chance going forward.

• 6:21Speaker 02

  That's right. We are seeing a universe that's increasingly dominated by this dark energy.

• 6:27Neil deGrasse Tyson?

  So Jason, that the original results from 25 years ago, which if I remember correctly, got the Nobel Prize, the discovery of dark energy, they use like supernova exploding like out to the edges of the universe and you get a distance from that, get a distance from some Hubble laws. And so are there other ways to verify that? To know that what we're thinking is really, that these other measurements are really true?

• 6:54Speaker 02

  With the original experiments on supernova that led to the Nobel Prize and the discovery of dark energy, they were really only looking out to supernova at a redshift of about one, Z of one, about halfway to the edge.

• 7:08Neil deGrasse Tyson?

  That's like halfway, that's only halfway across the universe, not all the way.

• 7:11Speaker 02

  That's right. So not back to the beginning of time. And one of the things we'd like to do is we'd like to push that back, push those measurements back further to a redshift of about two. And for that, we're going to use the Nancy Grace Roman Space Telescope, which NASA will launch in 2027. Whoa.

• 7:28Chuck Nice?

  Wait, you mean the, so, so the crime lady from HLN actually was an astronomer as well?

• 7:36Speaker 02

  No, in fact, Nancy Grace Roman was NASA's first chief astronomer soon after NASA was formed in 1958. And she was a champion of space telescopes. And in fact, she was called the mother of the Large Space Telescope. And the Large Space Telescope, when it was launched, had a different name, and that was the Hubble Space Telescope. So she was really one of the chief people pushing to build the Hubble Space Telescope, which of course has transformed our views of the universe and astrophysics in so many ways.

• 8:13Chuck Nice?

  Look at that, behind the scenes, a great woman, and of course, out front, some dude taking all the credit.

• 8:20Neil deGrasse Tyson?

  What are you talking about?

• 8:21Chuck Nice?

  Mr. Hubble. I mean, don't get me wrong, I understand Hubble was an incredible scientist, and he deserved to have his name on the telescope. But who knew that behind that whole project, there was a woman pushing the entire thing? That's amazing.

• 8:34Neil deGrasse Tyson?

  Yeah, yeah. So Jason, I know that Lyman Spitzer wrote a very early research paper after the Second World War, realizing that if V2 rockets can leave the atmosphere and do harm, they can also launch something into orbit, like a telescope. And he knew the value of telescopes above Earth's atmosphere for this purpose. But he wasn't active with NASA, right? Now, somebody at NASA inside has to make this happen as a goal.

• 9:03Speaker 02

  Yeah, sure. And Lyman Spitzer was a huge voice in the science community, making space telescopes happen at the same time that people like Nancy Grace Roman at NASA were making them happen. And of course, Lyman Spitzer had a fantastic infrared space telescope named after him. And so in 2027, Nancy Grace Roman is finally going to get her due with the space telescope named after her.

• 9:28Chuck Nice?

  Look at that. The women, first in, last out. Look at that. God, so predictable.

• 9:38Neil deGrasse Tyson?

  So what are these telescopes going to do? Are they still going to look at supernova, but just farther away?

• 9:44Speaker 02

  So one of the things Roman will do is look at supernova. But Roman is going to join a telescope already in space called the Euclid Space Telescope, and use a couple of other techniques to look for dark energy. And those techniques include weak gravitational lensing, where we look at small distortions in the measured shapes of background galaxies to measure the dark matter between us and those galaxies. And also a technique called baryon acoustic oscillations, which is a way of talking about the clustering of galaxies, how close galaxies are to each other. He's both.

• 10:21Neil deGrasse Tyson?

  Wait, wait, okay, but wait, so you're talking about dark matter there, right? Not dark energy?

• 10:28Speaker 02

  That's right.

• 10:29Neil deGrasse Tyson?

  Did I hear you right?

• 10:30Speaker 02

  You did, and so one of the things that we know is that dark matter, which is another mysterious component of the universe, interacts with gravity. So over time, dark matter becomes more clustered due to gravity. Gravity tends to pull things together. But at the same time, the dark matter is pushed apart by the dark energy. So by looking at how dark matter clusters and changes over time, we're learning about not just the dark matter itself, but the interplay between gravity and dark energy. And so that's how we learn about dark energy by studying dark matter.

• 11:06Neil deGrasse Tyson?

  Okay, so you know what to expect from dark matter? And if it doesn't live up to those expectations, something else is meddling within it. And you can track that over time.

• 11:16Speaker 02

  That's right.

• 11:16Neil deGrasse Tyson?

  That's interesting. All right, now what's this about balloons?

• 11:21Speaker 02

  Well, the reason we want to go to space with a telescope is we want to get above the Earth's atmosphere. The Earth's atmosphere causes things to twinkle, causes stars to twinkle. You know, I have a two-year-old daughter, and she started to sing "Twinkle, twinkle, little star", and I want to stop her and say, "No, no, it's not the star that's twinkling. That's actually the atmosphere."

• 11:43Speaker 02

  I hold myself back, but we want to get above that.

• 11:46Chuck Nice?

  Fun, more. Sweetie, you should be singing "Twinkle, twinkle, refracting atmosphere", okay?

• 11:55Speaker 02

  That's right. I'll correct her when she's three.

• 12:00Neil deGrasse Tyson?

  Worst dad ever.

• 12:05Speaker 02

  The atmosphere also absorbs a lot of wavelengths of light, so we want to get above the atmosphere. But a rocket launch is expensive.

• 12:14Speaker 02

  And it takes a lot of time to develop a space mission that's gonna go into space and you can't tweak it. So one of the things that NASA and other space agencies do is they put telescopes hanging from balloons, and these are huge balloons, the size of a football stadium.

• 12:32Chuck Nice?

  Wow.

• 12:33Speaker 02

  That are filled with helium, and they take these telescopes to the edge of the atmosphere, so that they're above most of the atmosphere, and then we can do days or even weeks of observations above most of the atmosphere. And so we just did that earlier this spring with a balloon called Superbit, which circumnavigated the Earth about five times from a launch in New Zealand. It's just the winds that take it around the Earth.

• 13:01Chuck Nice?

  Right, right.

• 13:02Speaker 02

  And all that time, we're making observations of clusters of galaxies, trying to understand the dark matter in those galaxy clusters.

• 13:09Chuck Nice?

  And China didn't shoot it down?

• 13:12Speaker 02

  No. In fact, NASA brought it down on purpose over land, because most of the Earth is ocean, and we wanted to recover the telescope and the hard drives. So NASA eventually said, alright, we're gonna bring it down where we can send a team to get the hard drives, because if they fall into the ocean, we're not getting those back.

• 13:34Chuck Nice?

  Well, I mean, listen, why not? You're setting up a balloon. You wanna tell me you can't attach a little raft to it, or some swimmies? Some swimmies? So that you can, so it will float and you can get the hard drives? I mean, even if something were to happen by accident, and listen, by no means am I denigrating the great efforts that you guys do, but I'm just saying, as a person who's been to a pool, that if you put some swimmies on your telescope, you might be able to recover it in case of emergency, that's all.

• 14:09Neil deGrasse Tyson?

  A minimum of pool noodle.

• 14:10Chuck Nice?

  Exactly.

• 14:13Neil deGrasse Tyson?

  Pull noodle.

• 14:14Speaker 02

  That wouldn't be a, that would have been a good idea, yeah. But, but we did come up with what I thought was a crazy idea about 10 years ago. We said, you know, hard drives are cheap compared to everything else. Let's eject some hard drives from this balloon and bring them down on a glider or a parachute during the mission. And so we had a crazy idea and we pursued it a bit. And in fact, we actually employed that on this Superbit mission. And we dropped some hard drives from way up in the atmosphere and then had them fall to the earth and then we can go recover it. It turns out we didn't need to do that because we used satellite downlink of the data and we were getting it all down. But we didn't know how well that was gonna work.

• 14:59Speaker 02

  So we had this backup of just dropping the hard drives out of the sky and finding them where they fell to the ground.

• 15:07Chuck Nice?

  That makes sense. In this age of 5G, you can just take the, almost in real time, take the information as you're collecting it. So, yeah.

• 15:16Neil deGrasse Tyson?

  Back in my day, back in my day, we would speak of bandwidth. We would compare bandwidth to the bandwidth of FedEx, right? You just take a tape, hand it to FedEx and they deliver it across the country faster than the uplink would allow you to transmit the data.

• 15:34Chuck Nice?

  I remember when we used to put satellites in space using a giant rubber band. It was like a slingshot. It was made by me.

• 15:53Speaker 03

  I'm Joel Cherico and I make pottery. You can see my pottery on my website, cosmicmugs.com. Cosmic Mugs, art that lets you taste the universe every day. And I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

• 16:18Neil deGrasse Tyson?

  So, I'd like these other methods to try to think about dark energy. So, all you're doing, though, is making more measurements of what we know is there, but you're not really telling us what it's made of.

• 16:30Chuck Nice?

  Well, the way I like to describe it is there's lots of theories for what dark energy might be: a new force, a property of spacetime, some mysterious particle, lots of different theories, and the theorists have really had a field day. And these theories all produce results, or would produce results, in the real world that are slightly different, and especially different with these different measurements: supernova, the Baryon oscillations, and the weak lensing. And so what we're trying to do is gather all the data to rule out huge classes of theories and say, "It wasn't that, it wasn't that," and it's sort of a last man standing thing where we say, "Okay, it's this one."

• 17:10Neil deGrasse Tyson?

  There might be just one left that you can't rule out, and so maybe that's it. I get you. Okay. All right, cool.

• 17:16Chuck Nice?

  Interesting.

• 17:17Neil deGrasse Tyson?

  All right, Chuck, let's go to Q and A here.

• 17:19Chuck Nice?

  You wanna go to Q and A?

• 17:20Neil deGrasse Tyson?

  Let's go. Got some Patreon members here.

• 17:22Chuck Nice?

  Here we go. And thank you all for supporting us on Patreon. And this is Calvin Wait. And Calvin says, "Hello, Jason, Lord Nice, and the longtime reigning king of StarTalk and the cosmos, Neil deGrasse Tyson."

• 17:38Neil deGrasse Tyson?

  They do that because they think that's gonna get their questions answered more.

• 17:42Chuck Nice?

  And they're right, because I'm reading it. Clearly, sucking up works.

• 17:53Chuck Nice?

  No, this is why I'm reading it, because he says, "I am 13 years old, and I recently became a Patreon member. This is a 13-year-old kid who is taking his paper route money and giving it to StarTalk so that he can ask questions, so the rest of you have no excuse at all, okay?"

• 18:12Neil deGrasse Tyson?

  Well, he doesn't know what the term "paper route" even means.

• 18:14Chuck Nice?

  No, he doesn't. I know. I know. Right. I'm dating myself, because I had a paper route. "I am currently on a trip in Talkeetah, Alaska, and I send you my regards with this question: due to the theory that the space and time places flip in a black hole..." If said black hole.

• 18:34Neil deGrasse Tyson?

  Well, that's that's Talkeetna.

• 18:36Chuck Nice?

  Talkeetna, is that how you say that?

• 18:38Neil deGrasse Tyson?

  I think, does it spell that way?

• 18:39Chuck Nice?

  It's just exactly that way.

• 18:41Neil deGrasse Tyson?

  Yeah, yeah, my wife is from Alaska and that's.

• 18:42Chuck Nice?

  I said Talkeetna, but it's Talkeetna.

• 18:45Neil deGrasse Tyson?

  Talkeetna, yeah, yeah.

• 18:46Chuck Nice?

  Okay, Talkeetna. Due to the theory that space and time flip places in a black hole. If said black hole is comprised of dark matter. Could we harness this dark matter or energy to travel through time and create wormholes to distant galaxies? I've been a fan for a very long time and I'm so excited to hear the answer.

• 19:05Neil deGrasse Tyson?

  Oh. Yeah, Jason, what do you got for that?

• 19:09Speaker 02

  Well, I'm gonna say unfortunately, Calvin, I think I had the name right. Unfortunately, once matter, whether it's dark matter or a normal matter falls into a black hole. It's really gone to us and we have no way to access it. And so a black hole could have normal matter in it. It could have dark matter in it. But that matter is gone and we don't have a way to access or harness the matter inside the black hole.

• 19:40Neil deGrasse Tyson?

  You think the black hole cared whether it ate matter or dark matter?

• 19:43Speaker 02

  Hmm, I think it was indifferent. It's gonna grow either way.

• 19:48Neil deGrasse Tyson?

  It doesn't discriminate.

• 19:49Chuck Nice?

  It doesn't care.

• 19:51Neil deGrasse Tyson?

  Now, what's gonna be fun is if Calvin actually invents this device in his basement. And then comes back, say, see, I was right all along. See, that's what's gonna happen here.

• 20:02Speaker 02

  You know, you know, that that sort of reminds me, Neil, that a lot of people think scientists never want to be wrong. But I would be thrilled if Calvin invented that. And in general, scientists are thrilled when their experiment shows something that makes them go, huh, that's not what I was expecting. So that's what happened with dark energy 25 years ago. We, we as a community said, that is not what we are expecting. And it's really exciting to be alive in a time where we find something completely unexpected.

• 20:35Chuck Nice?

  Right.

• 20:35Neil deGrasse Tyson?

  This was Isaac Asimov's edict. He said, "The, the, the, the clarion call of the scientist is not eureka. It's, hmm, that's, that's funny. You see some result. It's, I, I, what is, I don't know what this is." That's the discovery. It's not eureka. It can be eureka, but mostly it's not. All right, Chuck, give me more.

• 20:58Chuck Nice?

  Roland P. says, "Hello, Dr. Tyson, Lord Nice, and Dr. Rhodes. My name is Roland, and I'm writing from Cologne, Germanly. Sorry, Chuck, my na, my last name is unpronounceable to you."

• 21:12Chuck Nice?

  You don't even give me a chance to butcher your name, man. You don't even give me a chance to butcher it.

• 21:17Neil deGrasse Tyson?

  He just abbreviated with a P, right?

• 21:18Chuck Nice?

  He just went with the P, you know what I mean?

• 21:22Chuck Nice?

  My question about, my question is about the Euclid mission.

• 21:26Neil deGrasse Tyson?

  Hmm.

• 21:27Chuck Nice?

  When they say the probe will generate a 3D map of the universe, how do you cope with the fact that most of this map is outdated? The stars you are seeing might not be there anymore. The galaxies have moved, they've merged, et cetera. During the billions of years the light took to reach us, what you're looking at is a ghostly image.

• 21:50Neil deGrasse Tyson?

  Ooh.

• 21:51Chuck Nice?

  Oh, look at that gauntlet thrown down there, Jason. What's going on?

• 21:56Speaker 02

  That is a very interesting question, and the answer is, we don't want to know necessarily what those, uh, parts of the universe look like today, because we assume that they look very similar to the parts of the universe close to us that we can already see. We want to see what the parts of the universe look like in the past, and that's why we're looking further and further out. We're using infrared light to look closer to the beginning of the universe, because we want to see how the universe has evolved. So we don't want a static picture of the universe today. We want to measure this three-dimensional map, uh, where looking further away in that third dimension is also looking further back in time. So we want to look at the time evolution of the universe,

• 22:42Speaker 02

  because that's what's driven by this interplay between dark energy and gravity. So that, uh, what Roland has brought up is not so much a, um, a problem with Euclid. It's what Euclid is designed to measure.

• 22:55Chuck Nice?

  Alright, yeah, so it's

• 22:57Neil deGrasse Tyson?

  Euclid is a European Space Agency, correct?

• 22:59Speaker 02

  Yes, Euclid is a European Space Agency mission that launched July 1st, 2023. I'm wearing my Euclid shirt because I'm the US Science Lead for Euclid. NASA provided some great infrared detector technology to Euclid, and we have over 100 NASA-funded US scientists working on Euclid with our European counterparts.

• 23:20Chuck Nice?

  So when these agencies come together and collaborate, but yet you're still working independently, is there any competition or jealousy when somebody comes up with something great and the other part did not?

• 23:36Speaker 02

  Well, scientists are still human, so we can be jealous when somebody else has a good idea or a great mission from another agency or another country. But what we're seeing increasingly is scientists from different countries and agencies from different countries working together because the telescopes and the projects are becoming more complex and more interconnected. And so we have a telescope like Euclid that will work in certain ways, and it's going to be very complementary to NASA's Roman Telescope, which the European Space Agency is participating in, just like NASA participated in Euclid.

• 24:20Speaker 02

  So we're working together to build all of these telescopes on the ground and space. And we're going to use the data from all of these telescopes as a science community together to get the best constraints on dark matter and dark energy and the properties of the universe.

• 24:35Neil deGrasse Tyson?

  So I like the idea that you're saying we're looking back in time on purpose, and the fact that galaxies might have collided or stars won't be there by today, you don't care. You care that they were there back when we saw them. So that's an important distinction to make here.

• 24:49Speaker 02

  Interesting.

• 24:50Neil deGrasse Tyson?

  There it is. Alright, Chuck.

• 24:51Chuck Nice?

  Very cool, very cool. Let's go to Fabiola Hordvath. And Fabiola says, "My dear Dr. Tyson, Dr. Rhodes, and sweet Lord Nice, Fabiola here from Hungary. We are international for sure today, man."

• 25:06Chuck Nice?

  In my opinion, Euclid might be one of the most exciting research tools ever built. Can't wait for the results. I wonder if it will be able to shed light on what the Great Attractor might be, or debunk its existence once and for all. Thank you. I will always keep looking up. And please tell me your thoughts on the Great Attractor.

• 25:29Speaker 02

  So the Great Attractor is a group of galaxies and the associated dark matter, associated with those galaxies that's relatively nearby in the universe and is attracting other galaxies towards it through its gravity. And so Euclid will be able to produce not just a map of the dark matter there, but a map of the dark matter over fully a third of the sky. So one-third of the sky. And that's the best third of the sky in the sense that it's the darkest and furthest away from our Milky Way, which is littered with stars, which block our view of the distant galaxies.

• 26:12Speaker 02

  So Euclid will produce a huge dark matter map that not only can tell us about this Great Attractor, but other, many other, thousands of other dark matter conglomerations or galaxy clusters out there in the universe, much further away than just the local universe that we've been studying for the last hundred years.

• 26:32Chuck Nice?

  Interesting.

• 26:33Neil deGrasse Tyson?

  But what's been doing the attracting in the Great Attractor?

• 26:36Speaker 02

  Well, we think it's...

• 26:37Neil deGrasse Tyson?

  Is it related to the work you're doing?

• 26:38Speaker 02

  Well, we think it's galaxies and the dark matter associated with those galaxies. So it's just a big conglomeration of mass.

• 26:48Chuck Nice?

  As they coalesce and all this mass comes together, it just creates more of an attraction. Is that the deal? Or is it something like the Great Garbage Patch, where there's a natural flow to a particular point? You know, or something even more like the pooling of a LeGrande's Point? Do you guys, or do you know? At this point, I'm just throwing out a bunch of stuff.

• 27:13Speaker 02

  In fact, this is very related to one of the ways that Euclid and in a few years, Roman will probe dark energy. It's gonna, we're gonna use a technique called redshift space distortions. And what that is, is it's us looking at galaxies in redshift. So we're gonna see where they are in three dimensional space. That redshift tells us the distance. But there's some distortions there in those measurements because there's a local movement of the galaxies as they're attracted to big conglomerations of dark matter. And so we're looking at those sort of very minute local distortions in how the galaxies are moving.

• 27:53Speaker 02

  And encoded in the motions of the galaxies is a lot of information about the dark matter. And as we've talked about, that information about the dark matter is gonna tell us about the properties of dark energy in the universe.

• 28:07Neil deGrasse Tyson?

  So the movement of the galaxies, separate from the expansion of the universe, is they are your probes for the structure of where all the gravity is locally, local to that region. Is that a fair way to characterize that?

• 28:23Speaker 02

  That's exactly right. Yes.

• 28:25Neil deGrasse Tyson?

  Uh huh.

• 28:26Speaker 02

  We wanna probe that local structure.

• 28:29Neil deGrasse Tyson?

  Yeah, yeah, all right. All right, Chuck, keep it going. Time for a few more?

• 28:33Chuck Nice?

  Okay, so this is Ed Ianowski, who says, greetings from Portland, Oregon. And considering things like dark matter and dark energy, it seems we don't use Occam's razor that much. Why do we assume that dark matter is matter at all? Or that dark energy is indeed energy? What about the nature of space itself? We know space can warp, stretch, expand. Just because regular matter warps space, do we have to assume that the warping associated with this dark matter is also caused by some sort of matter that we call dark? Couldn't it just be a part of the nature of space itself? What is space?

• 29:13Chuck Nice?

  And why does it produce a vacuum energy, virtual particles, and the such? Okay, all right.

• 29:24Chuck Nice?

  That's a lot.

• 29:25Speaker 02

  Well, that was a lot, wasn't it?

• 29:27Chuck Nice?

  That was, wow.

• 29:28Speaker 02

  That was a lot, man. I'm gonna address the dark matter part first. So, you know, dark matter was first theorized, you know, close to 100 years ago. And the real, um, the first real, uh, strong evidence for dark matter was found, um, say in the 1970s and before that by a pioneering astronomer named Vera Rubin, who, who looked at, uh, the, the rotations of galaxies and said, these galaxies are rotating faster than they should be if, if the, um, if the, uh, galaxies are made up of just stars and dust, so there must be something else in there. And so this was the first real evidence, uh, for dark matter.

• 30:09Speaker 02

  And at the time, uh, dark matter was just the name given to whatever was causing this, uh, uh, rotating galaxies to be rotating faster than we thought they should be. However, over the course of the last half century, you've had increasingly, uh, num, an increasing number of different observations across all areas of astrophysics, which have told us that this dark matter is there, it's some sort of particle, and it is a mass, uh, just like normal matter, but it just, uh, only interacts gravitationally. And so the dark matter has gone from being sort of the way we explain some observations to being something predictive.

• 30:50Speaker 02

  That is, I am able to now say, okay, I think this is the properties of dark matter, so I should go out and I should measure something. And indeed, I, I confirm that, yes, there probably is this dark matter out there. However, yeah.

• 31:04Neil deGrasse Tyson?

  Wait, wait, you, you don't have a dark matter particle yet, though.

• 31:07Speaker 02

  We, we do not. Well, so there's two ways to look for dark matter. There's the astrophysical way.

• 31:13Neil deGrasse Tyson?

  Why'd you say that up front? Why'd you say that up front?

• 31:15Speaker 02

  Okay.

• 31:16Neil deGrasse Tyson?

  You said, well, we don't have any kind of dark matter particle, but we still want to think it's matter. That, that's what you just said.

• 31:21Speaker 02

  Yeah.

• 31:22Neil deGrasse Tyson?

  Okay, so what gives you the confidence that dark matter is made of matter? If we don't have a dark matter particle yet?

• 31:30Speaker 02

  So we see a lot of clustering of dark matter at different levels in the universe. So there's what we call a hierarchical clustering of dark matter that we can measure. And if it's a particle, that's the exact type of clustering we would see. And we see this astrophysically. So lots of groups on the ground are trying to detect the dark matter particle. And they so far have only come up with what we call null detections.

• 32:03Chuck Nice?

  Wow, that is so cool.

• 32:08Neil deGrasse Tyson?

  Okay, so null detections is they think it's a particular kind of particle. They set up an experiment and they should see that it's not. Then they think, is it a different kind of other particle? You set up a way to detect it and it's not. So these are all the null detections. So once again, maybe some other particle will be the last man standing.

• 32:25Speaker 02

  That's right, that's right.

• 32:27Chuck Nice?

  So you guys, I mean, that's a long process. You just have to keep ruling things out, like you're striking the list.

• 32:34Neil deGrasse Tyson?

  Yeah, half of science is ruling stuff out.

• 32:36Chuck Nice?

  It's just ruling it out, okay.

• 32:38Speaker 02

  Yeah, that's a lot of science.

• 32:39Neil deGrasse Tyson?

  And okay, now what about, the guy kept going though. He didn't stop there, but he still did go.

• 32:45Speaker 02

  Well, he asked about dark energy. And indeed, dark energy may be simply a process or a...

• 32:52Neil deGrasse Tyson?

  A property of...

• 32:53Speaker 02

  A property, a spacetime, that's right, a property of spacetime. And I don't know that dark energy was the best name for our ignorance of what's causing the accelerating expansion of the universe. But I wasn't the one that was asked to name it. So that's the name somebody came up with. I think it was actually a US astrophysicist named Mike Turner who came up with the name dark energy. And that's the name that stuck. But it's not an energy in the classical physics sense of an energy that we think about. It's perhaps some property of the universe. So we don't really know.

• 33:34Speaker 02

  And that's where we really are, just designing these experiments to rule out big classes of theories.

• 33:43Neil deGrasse Tyson?

  I would add that the dark matter could be literally and accurately named dark gravity. But no one's, no one picked up on that. And so, because that's what it is, right? It's, it's gra, it's gravity and we don't know where it came from. So it's dark gravity. And people just assuming that matter, you need matter to have gravity. And I thought that was overstepping, given our state of ignorance at the time.

• 34:08Speaker 02

  That, that's, uh, that's very possible. And you know, I think even dark matter isn't the best name because you can see the screen behind me is, is mostly dark because it's absorbing the light. Well, dark matter doesn't absorb or give off light. So it could be more accurately now called clear matter because the light passes right through it, uh, but it's, the path of the light is distorted by the gravity, but the light passes right through it.

• 34:32Neil deGrasse Tyson?

  Mm-hmm, mm-hmm.

• 34:34Chuck Nice?

  So that it doesn't interact with the light at all?

• 34:37Speaker 02

  Uh, no, it doesn't interact with the light at all. It only bends spacetime. The dark matter bends spacetime, so the path of the light is, is curved.

• 34:46Chuck Nice?

  I got you. But see, that happens anyway to, uh, what I call light surfing.

• 34:51Neil deGrasse Tyson?

  You get that for free. So, but you, Chuck, your hair is dark because it's absorbing light hitting it and not reflecting it back to me. It's interacting with the light.

• 35:01Chuck Nice?

  Uh, thank you for noticing. I appreciate that. All right. Wow, that was cool, man. That's, that's really cool.

• 35:24Neil deGrasse Tyson?

  Give me a couple more.

• 35:26Chuck Nice?

  All right. Uh, let's go with Kevin Curry. And Kevin says, hello, this is Kevin Curry from Sparks, Nevada. My question is about gravity. I understand that gravity moves in waves and propagates at the speed of light. However, do masses with high gravitational fields affect the waves from other masses? If so, is it possible to tell them apart? If not, how can we know the gravity from one mass actually came from the specific mass and was not modified by another mass between us and the original masses? In short, is gravity affected by gravity? Ooh.

• 36:11Speaker 02

  I like this question because it allows me to mention a new way of measuring the universe that's become increasingly popular and increasingly possible over the last decade, and that's by measuring gravitational waves. These are ripples in spacetime caused by massive particles, or not particles, but massive objects like black holes orbiting each other, or neutron stars orbiting each other, and they give off these gravitational waves. And we can see those gravitational waves interact with each other, and they interact with our very sensitive detectors here on Earth that are looking for very, very minute changes

• 36:56Speaker 02

  in the path of a wavelength of laser light that are caused by these ripples in spacetime. And that's only in the last decade, or even less than a decade, that we've been able to measure these, and it's an entirely new window on the universe. Previously, we had used light, whether that's light that we can see, or radio waves, or X-rays, but always electromagnetic radiation. And now we're building telescopes and using different techniques to study these gravitational waves, which are telling us about some of the same phenomena, but in a very different way. So it's a really exciting time to be an astrophysicist.

• 37:33Neil deGrasse Tyson?

  Well, if two of them intersect, do they resonate in some way? Do they cancel each other out? Two gravitational waves moving through space from two different origins?

• 37:45Speaker 02

  I think they can. They can interact. If you imagine ripples on a pond, if you throw a pebble in, and you throw another pebble in, you can get the interaction. And I think it's very similar for gravitational waves. You can get that interaction. And that's likely something that we'll be able to, you know, measure in the future as we get ever more accurate detectors. And in fact, there's a mission that the European Space Agency is going to build in hopefully the 2030s, and NASA will participate, called LISA, where they're going to put these lasers in space to measure gravitational waves in space.

• 38:26Neil deGrasse Tyson?

  Hmm, over a much bigger baseline than just two locations on Earth's surface.

• 38:31Speaker 02

  That's right, yeah.

• 38:32Neil deGrasse Tyson?

  We can get to see that, okay. Alright, I'm loving it. Alright, Chuck.

• 38:36Chuck Nice?

  Okay.

• 38:37Neil deGrasse Tyson?

  Good questions.

• 38:38Chuck Nice?

  Yeah, these people are on point today, I have to say.

• 38:41Neil deGrasse Tyson?

  And by the way, a thirteen-year-old has already created the wormhole.

• 38:44Chuck Nice?

  Yes, exactly.

• 38:46Speaker 02

  Congratulations.

• 38:49Chuck Nice?

  Uh, this is Thomas Cochran, who says, greetings from Kansas City, Missouri. I'm curious how you will go about exploring the mystery of dark energy with instruments that are tuned to collect data in the visible and near-infrared spectrum. Any speculation on how we can circumnavigate the issue of collecting data on something that doesn't interact with our universe in this typical way? Thank you for making us all smarter, right? So we just learned that it doesn't interact with light, so he's asking, if it doesn't interact with light, how are you using light to actually measure something?

• 39:28Speaker 02

  So we're measuring the properties of galaxies, and those properties are the shapes, the distances, and the motions of the galaxies. And encoded in the shapes, distances, and motions of galaxies is a lot of information about dark matter and dark energy. We can't measure dark matter and dark energy directly, but we measure those properties of the galaxies using visible and infrared light, and then we use the techniques that I talked about earlier, the gravitational lensings, the baryon acoustic oscillations, the redshift space distortions, uh, by measuring those galaxies to discern the properties of dark matter and dark energy.

• 40:06Chuck Nice?

  Everything's a bank shot. Everything you're doing is a bank shot. That's basically what you're saying. It's like, yeah, we don't try to sink the basket, we go off the backboard, and that's the deal.

• 40:17Neil deGrasse Tyson?

  By whatever way you can, right?

• 40:18Speaker 02

  That's right.

• 40:20Neil deGrasse Tyson?

  Yeah.

• 40:21Chuck Nice?

  Sweet. That is so cool, man.

• 40:24Neil deGrasse Tyson?

  I'll tell you, just in aside to this, Chuck, you know the electron, which we all talk about, and we...

• 40:30Speaker 02

  Of course.

• 40:30Neil deGrasse Tyson?

  You know what the charge is, and we don't know how big it is.

• 40:34Chuck Nice?

  Oh, wow.

• 40:35Neil deGrasse Tyson?

  We've never measured the size of an electron, ever. As far as we know, it's infinitesimally small. So what does it even mean to talk about an electron as though it's an actual particle? When in fact, what we really mean is, whatever it is, it has these properties that we've measured for it. And it's the properties that interact with everything else we care about.

• 40:59Chuck Nice?

  So if we don't know how big it is, so there's been no actual sighting of an electron?

• 41:05Neil deGrasse Tyson?

  Basically, but you can cite the effects of an electron.

• 41:07Chuck Nice?

  Right, yes.

• 41:08Neil deGrasse Tyson?

  But not the electron itself. Right, so that's all Jason is saying, I think, Jason, is that the better, the more precisely you know the galaxies, the better you are able to know what effect the dark matter, dark energy has on the galaxy. Because that's, otherwise you're not catching it in the open field, right?

• 41:26Speaker 02

  That's, that's right, with one subtlety, in that these effects of dark matter and dark energy are very subtle. And so we want to measure not just a very precise measurement of a galaxy. What we're gonna do with Euclid is we're gonna measure shapes of over a billion galaxies and to do a statistical study. And so it's really, these new telescopes, Euclid and then Roman in a few years, are going to provide huge amounts of data, huge amounts of measurements on galaxies that allow us to discern the properties of dark matter and dark energy through statistical studies. So our measurement of any one galaxy.

• 42:07Neil deGrasse Tyson?

  If it's a billion galaxies, if a billion galaxies, you've got AI helping you in there somewhere.

• 42:11Speaker 02

  We, we, we have to have AI helping us because we can't, we don't have enough grad students to look at each galaxy individually. Over time, yes.

• 42:21Chuck Nice?

  You need something that can look at millions of them all at once and say, that's not necessary, or we don't have to look at that, or those are all the same, or here are the anomalies. That makes sense.

• 42:32Neil deGrasse Tyson?

  Mm-hmm.

• 42:33Chuck Nice?

  That's super cool, man. Damn. God, you guys have such a cool job. It's amazing.

• 42:42Neil deGrasse Tyson?

  Well, we got time for one last question, I think, Chuck.

• 42:44Chuck Nice?

  This is Gavin Bamber. Bamber says, hello, from North Vancouver. Where? Where it doesn't matter that I have energy?

• 42:57Neil deGrasse Tyson?

  What?

• 42:58Chuck Nice?

  Okay.

• 43:00Chuck Nice?

  But, yeah, he's, um, I think that was a joke. He says, why is it called the Euclid Mission? And how does that, how does any of this pertain to geometry? Okay, so he's going, he's going very literal with the Euclid.

• 43:16Neil deGrasse Tyson?

  Calling it out.

• 43:17Chuck Nice?

  Calling, yes.

• 43:19Neil deGrasse Tyson?

  Calling it out.

• 43:20Speaker 02

  So when we were looking for a name for this mission, uh, we thought about what are we measuring? And when you measure the, uh, expansion history, uh, of the universe, uh, one way that scientists describe that, they say you're measuring the geometry of the universe, what the universe looks like. And who is more associated with, uh, geometry than the, the father of geometry, uh, Euclid, who wrote a textbook on geometry, um, you know, 2,000 years ago, uh, that was still in use up to a couple hundred years ago. So this was an amazing, uh, scientist, uh, who, who really founded the field of geometry. And so we are trying to measure the geometry of the whole universe.

• 44:03Speaker 02

  So it seemed an apt person to name this mission after.

• 44:06Neil deGrasse Tyson?

  I would add, however, I would add, just to be, just to be snarky, but I agree with everything you said, of course. But to be snarky, uh, when Einstein showed that matter and energy distort the fabric of space and time, Euclidean geometry was no longer Euclidean. It was non-Euclidean geometry. So everything that is in the universe is a negation of the flat. Plain, flat space world that Euclid had described. But he just started all, so I give him that.

• 44:44Chuck Nice?

  Yeah, okay.

• 44:46Neil deGrasse Tyson?

  Because Chuck, you remember, Chuck, you remember, parallel lines never meet?

• 44:50Chuck Nice?

  Right. Exactly.

• 44:51Neil deGrasse Tyson?

  In Euclidean geometry, in non-Euclidean geometry, they either meet or diverge. Okay, they don't just stay the same distance. Weird stuff happens. There was a whole other step that everybody had to take. And it was quite an adjustment, I might add, to go there. But non-Euclidean, so we should have called it the non-Euclidean.

• 45:13Chuck Nice?

  The non-Euclidean mission. Wow, that.

• 45:19Neil deGrasse Tyson?

  Get people looking that stuff up.

• 45:21Chuck Nice?

  Man, that's a serious diss right there. By the way, Euclid, this is not your mission, okay? Just letting you know, this is the non-Euclidean mission, okay?

• 45:33Neil deGrasse Tyson?

  So Jason, this is great. It looks like you're gonna have new knowledge to surface in the coming months and definitely years. So give us a call when you got something to report and we would be delighted to get you back on.

• 45:46Chuck Nice?

  Would love to.

• 45:46Neil deGrasse Tyson?

  Because for me, it's the biggest mystery in all of science now is the dark energy problem.

• 45:51Chuck Nice?

  It really is very perplexing.

• 45:53Neil deGrasse Tyson?

  Yeah, yeah. All right. And so Jason, also thank your three bosses, the head of JPL, the head of Caltech and the head of NASA for lending you to us.

• 46:03Chuck Nice?

  Yes.

• 46:04Neil deGrasse Tyson?

  You'll do that for us.

• 46:04Chuck Nice?

  I will, thank you, yeah.

• 46:06Neil deGrasse Tyson?

  All right, excellent. Thanks for being on with us. Chuck, always good to have you, man.

• 46:09Chuck Nice?

  So much fun, always a pleasure.

• 46:12Neil deGrasse Tyson?

  All right, this has been StarTalk, our dark energy edition with a touch of cosmic queries within, and my friend and colleague, Jason Rhodes from JPL. This has been StarTalk, as always, I bid you to keep looking up.