Can Future Telescopes Solve Dark Matter Mysteries? | Bob Kirshner

Bob Kirshner and Brian Keating explore the future of the TMT and GMT telescopes in studying dark energy and exoplanets. They also consider recent controversies in cosmology regarding dark energy and the potential for astronomical measurements of neutrino mass. Learn more about your ad choices. Visit megaphone.fm/adchoices

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

• 0:00Speaker 00

  Now, more than ever, we need someone on our side. But Rob Whitman? Whitman's votes drove up costs, cut Medicaid, and risked 350,000 Virginians' health care to pay for tax breaks for himself and his donors. He's not on our side. Shannon Taylor will fight corruption, cut taxes, and bring down costs. This November, vote for Shannon Taylor. She's for us. Paid for by HMP, the House Majority PAC dot com. Not authorized by any candidate or candidate's committee.

• 0:31Speaker 01

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• 0:58Speaker 06

  Both these projects, the GMT, Giant Magellan Telescope, and ours, the TM, are ready to be advanced to the final design phase. So that's kind of a formal thing within NSF. You're in preliminary design, and we have been. You have a preliminary design review, and we did. And then, after some contemplation, the NSF could, if they wish, advance you to the final design phase. So we're hoping they'll do that soon. I would say there's been a lot of activity in Washington that has occupied the NSF people with other matters, you know, in the last few weeks. Nevertheless, I think we're on course to hear from them before too long.

• 1:39Brian Keating?

  And of all the topics that TNT is capable of unraveling in the universe?

• 1:44Speaker 06

  They wrote up, 10 years ago, a detailed science plan that said, here are the things we're gonna do. And this is taken very seriously by the engineering crew. They said, well, if you want to do this, that, and the other, what does the telescope have to do? And so they wrote specifications for the telescope based on doing the science. Perhaps you're familiar with this concept. But that was 10 years ago, and it's fair enough to ask, how much has science changed in 10 years? Honestly, my special field, the field of dark energy and cosmic expansion, hasn't changed very much. But a field that has totally blossomed, of course, is exoplanets, the discovery of planets around other stars.

• 2:27Speaker 06

  So we wanted to make sure that even with the new understanding and the broader set of questions and kind of what we do know and don't know, that the telescope is still on the path to being powerful for that work. So we did that, and that was a very healthy exercise. We got over 200 people to help fix this old report. You won't be too surprised to learn that we concluded that the telescope is going to be able to do these new things very, very well. But, but thinking farther down the line, this telescope is not for 10 years or, you know, it's for 50 years. And so it's a matter of getting the science for today and then the potential for science for tomorrow. Because if you think about it, the technology also is advancing.

• 3:10Speaker 06

  So it's not just the science, but the technology for detectors and everything is getting better. And we are going to be in a position sooner or later to have a second generation of instruments and to keep on making this telescope right up at the technological frontier. You know, if you think about Palomar, we drove by Oceanside or wherever it was there. And I thought, gee, that's right downhill from, from Palomar. That telescope was built in 1950. You know, still, it had led the world for quite a long time because the instruments kept getting better. They went from photographic plates to electronic detectors, all these things that we kind of know about and take for granted.

• 3:50Speaker 06

  And it isn't at the absolute forefront now, but it's still a very productive scientific place. So I think the lesson from that is that these big telescopes at the frontier of what you can do today are going to last for decades. And they're going to be, it's a generational thing. And I really feel that myself, that. I got to use the 200-inch telescope. I didn't build it. I got to use the telescopes at Saratololo in Chile and at Kit Peak, and I didn't build those. But after a while, you know, you grow into a role where you do help to build the telescopes. And I did help the Magellan telescopes, and I was the head of the optical and infrared

• 4:33Speaker 06

  at the Center for Astrophysics for a while. So, and I was on the, actually, I'm kind of proud of this. I was on the committee that wrote the report. This is how we take pride in ourselves. I was on the committee that wrote the report about what we should do after the Hubble Space Telescope. And of course, that eventually became the James Webb Space Telescope.

• 4:54Brian Keating?

  3D print?

• 4:55Speaker 06

  Yeah, very nice work there. It's not that color, actually.

• 4:59Brian Keating?

  Well, yeah, it's space and no one could see it. Okay. So it wasn't that Hale who went a little bit over the edge psychologically in the building of 100 inches?

• 5:08Speaker 06

  Well, it was in between the 100-inch and the 200-inch. So it was very, here's the interesting story. If I can remember the guy's name, I will tell you, but I haven't got it quite at the top of my mind. But there was at the, the money for the 200-inch telescope came from the Rockefeller Foundation. And the Rockefeller Foundation did not want to give the money to the Carnegie Institution, which had been running Mount Wilson where Hale had been working. But Hale had another pocket there where he said, well, I also have this California Institute of Technology I've helped build. And so the money came to Caltech for the, for the 200-inch telescope.

• 5:51Speaker 06

  And the grants officer at the Rockefeller Foundation was a physicist and participated quite a bit in the design and, you know, approval of the, of the project. And when Hale became incapacitated, just he was having nightmares. Clearness break in his job. Yeah, well, you'd call it that. He, this guy, whose name I gotta remember, came from the organization, organization that was doing the funding to be the head of the project. Mm-hmm. Now for the TMT, the Gordon and Betty Moore Foundation was a very important part of getting this thing going. And I was the person at the Moore Foundation over the last,

• 6:35Speaker 06

  right, well, since 2015, anyway, not getting it started, but sustaining it for the TMT. Right. And I was the observer on the board, but you know, did everything but vote. Right. And when it came time to, well, of course,

• 6:54Speaker 06

  Ed Stone was the executive, whatever we call ourselves, he's the executive. But you know, when it was time for him to step down, they looked around, they thought, well, who could do this? They asked me to do it. So I used to be the funder and now I'm the head of the, of the project, just like the guy for the 200 is. And hopefully I should remember.

• 7:17Brian Keating?

  Hopefully the same fate won't befall you, Bob, because that would be a tragic loss for all of astrophysics. So speaking of your field, so you're one of the few people that can say, you proved this guy, this is Albert, good old Albert, wrong. You discovered, effectively discovered the accelerating expansion of the universe courtesy of what we now, you know, think might be related to dark energy. But lately, there's been a little bit of a controversy, as our British friends might say, that maybe there is no dark energy. Maybe we live either in a universe where dark energy is evolving or doing something, or we live in a void, in which case, you know, well, you legitimately lost an O L prize. You don't have to give one back. But would your students, you know, would your, your former very close colleagues,

• 8:01Brian Keating?

  Adam Reese, who sat there last year, and Brian Schmidt, who I talked to last year as well, tell me, what would be, what's the state of play of that field?

• 8:09Speaker 06

  Well, I think the first one that you mentioned, that the dark energy might be evolving over time, that has some, well, it's very interesting. It is true. And there's a statistical signal that, you know, matches up better with changing dark energy than with constant dark energy. It's data from DESI. This is a very large spectroscopic survey. And there's going to be a lot more data. So you know, when there's a controversial result, well, you need more data. And sometimes the result gets stronger.

• 8:47Brian Keating?

  Yep.

• 8:47Speaker 06

  And sometimes it goes away. So I think we're at that kind of a point where you should pay attention for sure. And this is really interesting. And we should encourage those DESI people to keep going.

• 8:59Brian Keating?

  All right.

• 8:59Speaker 06

  And do more of their analysis and more of the data taking. So I think that's really interesting and a big possibility. The other one that you mentioned that maybe we're in a void and therefore

• 9:11Brian Keating?

  Timescape for the listeners that I mean, I know it's called Timescape cosmology. I hope to have the authors of this controversial, but provocative in an interesting way.

• 9:19Speaker 06

  Yeah.

• 9:19Brian Keating?

  So what's your take on this?

• 9:20Speaker 06

  I'm not less interested in that. I think you have to satisfy many constraints to get a complete picture of the cosmology. So you heard of the microwave background. You gotta do that.

• 9:33Brian Keating?

  All right there.

• 9:34Speaker 06

  I've got to do that properly. I mean, the ages of things, right?

• 9:37Brian Keating?

  That's right.

• 9:38Speaker 06

  And the level of homogeneity that we observe has to somehow be embedded into an analysis of all the stuff. So it is true that if you use this particular model for how things are arranged and how that affects the expansion, that you can get an effect that looks like cosmic acceleration. But you have to do all those other things too, it seems to me. And the picture, the broader picture of Lambda cold dark matter kind of picture seems to be a much more comprehensive physical picture. Now, that's not exactly an experimental, you know, test.

• 10:20Speaker 06

  But I think it does matter that you do not just one thing, even if you do it as well or better, but that you, at the same time, satisfy all these other constraints, the ages of the stars and the clustering of galaxies and all that stuff that we've been working so hard to turn from hand waving into real statistical understanding.

• 10:45Brian Keating?

  Right. And a lot of the sort of analysis that goes into the timescape model for my listeners who may or may not be familiar with it has to do with, you know, kind of, I would say, Not in a pejorative sense, but manipulation of confidence intervals and, you know.

• 10:59Speaker 00

  Now, more than ever, we need someone on our side. But Rob Whitman? Whitman's votes drove up costs, cut Medicaid, and risked 350,000 Virginians' healthcare to pay for tax breaks for himself and his donors. He's not on our side. Shannon Taylor will fight corruption, cut taxes, and bring down costs. This November, vote for Shannon Taylor. She's for us. Paid for by HMP, the House Majority PAC dot com. Not authorized by any candidate or candidate's committee.

• 11:28Brian Keating?

  Bayesian reasoning applied to, you know, to this, to this problem, to then set a threshold at which you would exclude the proposition that at least, you know, dark energy is a cosmological constant, according to what I've seen. But as you pointed out, it has to, you know, it's very hard to break the standard model, whether it's particle physics or cosmology, right?

• 11:47Speaker 06

  Yeah, and I think looking at a particular data set and showing that your model fits it well is not the same thing as getting the whole physical picture, which is not the work of one person or of 10, you know, it's of thousands who have worked so hard on all of this. So I think we should reserve judgment. I just, that to me is less interesting, yeah, just personally, than the DESI result.

• 12:16Brian Keating?

  Mm hmm. Another, you know, maybe more pressing, more important thing, you know, if dark energy goes away, if it evolves, well, it's not a cosmological constant. That's okay. It won't affect us for, what, 100 billion years? But, but there's something floating around in space that's gotten in the news recently. It's related to this. This is a piece of Chelyabinsk meteorite, which I've gotten. This is actually a gift for you, Bob.

• 12:38Speaker 06

  Oh, because you got that into the window or something?

• 12:41Brian Keating?

  So this was delivered by the United States Postal Service. But this is actually a meteorite. This is from the Campo de Cielo Fall in, in Argentina. I give these away to those of you on my, on my email list.

• 12:53Speaker 06

  We're generous, fellas. This is for you.

• 12:56Brian Keating?

  And if you have a, and that's to go to briankeating.com/yt for YouTube or list. But if you have a dot edu email address, like many of our proteges. And friends and colleagues do.

• 13:06Speaker 06

  Yeah.

• 13:06Brian Keating?

  I'll send you one of these for sure if you live in the United States. So this is a real meteorite. I give it to him. He had to come all the way down and give a colloquial and say, you, you gotta.

• 13:13Speaker 06

  You must have tons of this stuff.

• 13:15Brian Keating?

  Literally.

• 13:15Speaker 06

  Well, illegal.

• 13:16Brian Keating?

  Yeah, it's illegal to get to, to export them now. So I got a whole bunch of them. Um, I have here a plate collected by, um, a former, uh, denizen of Pasadena. Uh, her name was, uh, Margaret Burbidge. You want a Margaret's old plates? Cause this is Jeff Burbidge's office. I don't know if you knew that. I inherited his.

• 13:33Speaker 06

  He did come here when Jeff and Margaret were here, but at, in London, might've been seventy four or five or six years.

• 13:40Brian Keating?

  Well, he, yeah, so he passed away about fifteen years ago now. It's incredible. Uh, I miss him and, uh, Margaret passed away at the beginning of COVID. Uh, not from COVID, but we must heard tremendously too. She was the original founder here. Uh, so she actually worked very closely with Vera Rubin. Uh, and actually Vera did a sabbatical here. She couldn't get a professorship, as you know, and so, uh, but, but the Burbidge is very kind to her. And she credited them with, with, um, Margaret, especially, you know, Jeff wasn't an observer. He was a theorist, uh, but with teaching her how to do the spectroscopy. And actually Margaret measured a lot of these rotation curves before, uh, before Vera did.

• 14:12Speaker 06

  Yes, I know that.

• 14:13Brian Keating?

  She just didn't really.

• 14:14Speaker 06

  I know that. And I remembered reading those papers when I was a graduate student. And the penny didn't drop for me either.

• 14:20Brian Keating?

  And oh.

• 14:21Speaker 06

  Uh, I should have thought more about what does it mean about the mass distribution?

• 14:27Brian Keating?

  Exactly.

• 14:28Speaker 06

  To have a, a rotation curve of that shape and which I, you know, I was just a kid.

• 14:33Brian Keating?

  Yeah.

• 14:33Speaker 06

  But I should have thought of that.

• 14:35Brian Keating?

  But you literally have forgotten more than I know most people will ever know. But so I, I talked to Michael Turner, not too long ago, friend. He's, or he's for. And I told him, well, we were looking for these axioms with the CMB polarization, with the Simons array and Simons observatory. He's like, and I was like, well, your paper was actually the first one. He's like, no, I didn't, you know? We went back and forth and I, I showed him, actually you've forgotten that you created this, uh, this, this term. Probably always in the context of code. Anyway, I'll get back to dark matter.

• 15:01Speaker 06

  Yeah.

• 15:01Brian Keating?

  Uh, dark matter is another thing that's quite controversial. You may know in the, in the two different approaches, one is looking at the heavens. One is looking, um, in the laboratory, we have experiments here to look for. Um, what's, what's the current thinking on dark matter? What can TMT do perhaps? What, what, what is the alignment with the future science goals of that amazing?

• 15:18Speaker 06

  That's true. That's a good question. Uh, for the dark matter, of course, something that we could measure is how clumpy it is. And we could do that because the telescope will have fantastically good angular resolution. So if you're looking at a bunch of stars, say a globular cluster where there are lots and lots of stars in the field, very close to one another, and you measure their positions over time, you could see the effect of a medium sized black hole or clumpy dark matter on the positions of the of the objects. So we're not going to image the dark matter, but we're going to see the effects of it.

• 16:00Speaker 06

  And of course, that's the whole story here for the physicists, trying to see the dark matter bump into a xenon nucleus or something like that.

• 16:10Brian Keating?

  Right here, yeah.

• 16:11Speaker 06

  That's a great idea. And we thought for a long time, I mean, decades now, that it was just around the corner.

• 16:18Brian Keating?

  Yeah.

• 16:19Speaker 06

  And it was gonna happen. And now tremendous ingenuity has been devoted to this. And a lot of xenon, by the way, which is quite bad. Yes, it is quite, but you can use it for something else after you're done. The, you know, the, there's still no evidence for the weakly interacting massive particles of wimps that Michael Turner also was very influential in popularizing.

• 16:49Brian Keating?

  You touched upon the DESI results recently.

• 16:51Speaker 06

  Yeah.

• 16:52Brian Keating?

  Which were phenomenal. They've been out for about a year. I'm devoting a special explanation episode of the of the podcast in a couple of weeks. I don't know if it'll be out by the time this comes out, but one of the interesting conclusions has come from a colleague here, Professor Dan Green, who claims that there's evidence for negative neutrino mass. So one of the main outcomes of DESI has to do with neutrino mass as well as many other science schools. So you're shaking your head maybe?

• 17:17Speaker 06

  Well, I, you know, not because I really know.

• 17:20Brian Keating?

  No.

• 17:21Speaker 06

  Or have a strong understanding, but you know, it's very novel. Um, and it's could be so, I guess, but it's not an area where I have any expert.

• 17:32Brian Keating?

  No, but your, I mean, your book was very formative in my, in my career early on as a graduate. So the extravagant universe, wouldn't this be sort of the most extravagant thing that you could think about? Negative mass or, or even, um, well, first address that. So how extravagant, has the universe gotten more or less extravagant in the 20 plus year, 26?

• 17:51Speaker 06

  Well, I, you know, it is surprising to me, uh, not that we've made so little progress because there has been progress.

• 17:58Brian Keating?

  Yes.

• 17:59Speaker 06

  And the, the signals have gotten stronger, the measurements are way, way better. You know, instead of having 10 supernovae, we've got the thousand in the, in these samples. And we're soon going to have tens of thousands and many more. So the evidence is really better, but what's been surprising to me and what you're hinting at is that there's a conceptual gap. Where is the new idea that is so persuasive that everybody says, well, that must be the, that must be the right story. And, uh, you can think of other areas, like the one you work in, where the idea of inflation somehow seemed like just the right thing.

• 18:42Speaker 06

  Uh, and, uh, you know, that is still, well, what everybody talks about. And if you can make a measurement, which I know you want to, uh, that shows that that's really the case. That'll be a big step forward. So going from, uh, an idea that kind of sweeps the field, but you know, still leaves room for speculation. To a story where the evidence is so strong that, uh, it really tells you what this story is. That takes a lot of effort and, uh, so just having a good idea is one thing. Having a good idea that other theorists think is interesting, that's better.

• 19:25Speaker 06

  Uh, but even that doesn't prove it, you know, the thing that is, uh, and even when you have a prediction that's matched by the data, that doesn't exactly prove it, but it sure makes you think you're on the right track. And, uh, you know, the, the last hundred years or so have been a fantastic story of, uh, uh, coming to some deep understanding of what the universe is. It's not exactly where it came from and so on, but you know, people are care about that too. And there are different models for how things could have begun. The inflation model is the one a lot of people like to talk about, but you know, there are also.

• 20:07Speaker 06

  So, so I think it, you have to have a strong enough motive to carry out the observations, but you also have to keep an open mind about what it might mean.

• 20:18Brian Keating?

  That's right. And on that, in the vein, as we wrap up, I want to be a good, you know, co-host here and not make you miss your coffee and cookies that you're legally entitled to.

• 20:28Speaker 06

  Yes.

• 20:29Brian Keating?

  Is another concomitant measurement that we'll get with the CMB hopefully, and DESI might get as well, and that's of neutrino mass themselves, negative or positive, but the, but that as a study, I want to ask you not in terms of technique or technology, but that would be the first time as far as I, you know, can be aware of that an elementary particles mass would have been measured by an astronomical, not a laboratory-based experiment. And knowing the sociology of the field so well as you do from your just illustrious career, what do you think would be the reaction? I mean, I've asked this of particle physicists too, but do you think it would be accepted? I mean, do you think that those stodgy, you know, people working in deep underground labs at the LHC or whatever, do you think they're really going to, you know, really

• 21:12Brian Keating?

  my, my former, you know, co-author on our audiobook, or she at least read the, read the intro of Galileo's Dialogue, Fabio Lignati, is she gonna, is she gonna accept the measurement of the, from, from these, you know, astronomers looking around with a telescope?

• 21:26Speaker 06

  Well, I don't know. You can't tell other people what to think.

• 21:29Brian Keating?

  That's true.

• 21:30Speaker 06

  But my guess is that the cultures are sufficiently different and the ways of going about things are sufficiently different that it would take quite a long time.

• 21:41Brian Keating?

  Yeah.

• 21:41Speaker 06

  For that to happen. But look at the solar neutrinos, for goodness sakes. There, we don't exactly know the mass. Well, we know the difference of the mass. Well, that's, that's a real step forward and that everybody accepts. Yeah. That now from the neutrino mixing. So I would say these things that are at the boundary of the various tribes are the things where we have to be really cautious and helpful to each other. The physicists tend to think they know better.

• 22:12Brian Keating?

  Yep.

• 22:13Speaker 06

  But sometimes the results come from a more straightforward way of doing things that astronomy is used to.

• 22:23Brian Keating?

  Yeah. And as you say about this, thinking about the greatest breakthroughs did come about because of the comity of man and woman and the agreement between formerly disparate fields, everything from, you know, climate change to, as you say, neutrino mass differences and even things like speed of light, relativity historically.

• 22:41Speaker 06

  Yeah, right. So that's a good lesson. And that's why people should listen to your podcasts.

• 22:47Brian Keating?

  And go to other people's talks.

• 22:48Speaker 06

  Yes, I bet you better go. That's ultimate in being, Bob Kirshner, it's always a pleasure to be with you. We should do this more often. Thank you, Brian. Every time I come down Interstate 5, I'll stop in here.

• 23:01Brian Keating?

  Thank you. You heard it here, folks. Thanks very much. Stay tuned for another episode of the Into the Impossible podcast with yours truly. Thanks a lot, Bob.

• 23:08Speaker 00

  Now, more than ever, we need someone on our side. But Rob Whitman? Whitman's votes drove up costs, cut Medicaid, and risked 350,000 Virginians' health care to pay for tax breaks for himself and his donors. He's not on our side. Shannon Taylor will fight corruption, cut taxes, and bring down costs. This November, vote for Shannon Taylor. She's for us. Paid for by HMP, the HouseMajorityPac.com. Not authorized by any candidate or candidate's committee.