Feb. 22, 2026

Dark Matter Mysteries, Telescope Innovations & the Quest for Gravitons | SN602 Q&A

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Show Notes
Transcript

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This episode of Space Nuts is brought to you by NordVPN. Protect your online privacy with the one we trust - NordVPN. To get our special deal, visit nordvpn.com/spacenuts.
And Incogni - incogni.com/spacenuts

Exploring Dark Matter, Telescope Innovations, and Olympus Mons
In this engaging Q&A edition of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson tackle a range of fascinating listener questions that dive deep into the mysteries of our universe. From the elusive nature of dark matter to the future of space telescopes, this episode promises to enlighten and entertain.
Episode Highlights:
- The Mystery of Dark Matter: Listener Bob from Chicago asks how astronomers have determined that approximately 80% of the universe is made up of dark matter. Fred explains the historical context and the groundbreaking techniques that have led to this astonishing conclusion.
- Next-Gen Telescopes: Ben also inquires about the next large telescope to be launched. Fred shares his excitement for the Extremely Large Telescope (ELT) in Chile, which promises to revolutionize our understanding of the cosmos with its advanced capabilities.
- Understanding Telescopes: Ash from Australia seeks clarity on the different types of telescopes and the wavelengths they detect. Fred elaborates on the intricate designs of optical, infrared, and radio telescopes, explaining how their unique technologies allow them to observe various forms of light.
- The Graviton Enigma: Russ from the UK poses a thought-provoking question about the graviton and its relation to Einstein's theory of gravity. Fred discusses the complexities of gravity as a force and the ongoing quest to understand its fundamental particles.
- Olympus Mons and Space Elevators: Robert from Iceland wonders if Olympus Mons could serve as a staging point for a space elevator. The hosts explore the challenges and feasibility of this intriguing concept, revealing the importance of location in such ambitious projects.

For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, Instagram, and more. We love engaging with our community, so be sure to drop us a message or comment on your favorite platform.
If you’d like to help support Space Nuts and join our growing family of insiders for commercial-free episodes and more, visit spacenutspodcast.com/about.
Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.

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WEBVTT

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Hi there, thanks again for joining us. This is Space Nuts,

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a Q and A edition. This is where we answer

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audience questions. Well, we read them out and then we

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pretend we know what we're talking about, and most people

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fall for it. They might not fall for it today though,

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because we've got some really interesting questions about a matter

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of matter that we cannot see. Does it matter? We

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will find out questions come up about gravitons. We're also

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going to answer a question about space telescopes. Now that's

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right up, Fred Zali. He knows everything there is to

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know about space. Telee's written books about these things, so

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this is going to be a good question. And a

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question has come up about whether or not Olympus mons

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might make a good staging point for a space elevator.

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We will answer all of that on this episode of Space.

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Nuts fifteen, Channel ten nine ignition sequence Space Nuts or

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three two one Space Nurse.

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And I report it meels good and it feels good

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to have his one and only self, professor've Fred's on

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Astronomer at Large back in the chair.

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Hello Fred, Hello, hello here, all ready to go, fresh and.

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Well?

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Slept, yeah, sort tough weird.

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Night last night. I actually went to sleep fast, didn't

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I only woke up kind of once once, which is

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a new world record. And then I woke up at

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five eighteen am and that was it. My body went

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out that we're done binget up, go and watch something

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on television because I'm not you know, I don't want

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to go to sleep it ever again. So here we go.

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Who knows what will happened tonight. Sleep is a weird thing.

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We need it, and yet our bodies sometimes refused to comply. Yeah, yeah,

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it is.

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It's bizarre.

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It's a strange thing. Shall we answer some questions? I

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thought that was it. Well, I was just going to say, Fred,

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why can't I sleep?

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Let's answer some questions?

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Okay? Our first one comes from Ben. He says Ben here.

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It's good because I thought he was Ben too, the

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Aussie and Chicago with a few new questions. In your

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Last Question podcast, you mentioned about how eighty percent of

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matter is missing or not visible to us, and it

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made me think, how do we know or measure that

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amount in the first place. I know a lot of

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science is about measuring what we didn't find in results,

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but I'm curious about how they came to that eighty

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percent dark matter number. And secondly, for a smaller question,

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if you could pick the next large telescope to be launched,

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what would it be and why I'd personally love to

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see a new larger Hubble type telescope with all the

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advances we've applied to it that we've learned from the

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James Webb Space Telescope. Thanks again for the great podcast.

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Thank you, Ben. Great to hear from you. I hope

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all is well in Chicago, home of the Bears, Chicago Bears. Right,

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So it's a matter of matter, and he's saying, we

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know there's eighty percent of the universe made up of

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dark matter or thereabout. How do we know that?

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We actually the way that we get the you know,

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the accurate figures is quite interesting because it involves work

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of the kind that wasn't possible before astronomers started using

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fiber optics in their telescopes. And that's what I did.

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Was one of the pioneers of fiber optics in astronomy.

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The systems that we built back in the eighties the

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nineteen eighties have now evolved into Mars machines which are

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fully automated. The organization that I worked for has just

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delivered one to Chile, which will position two four hundred

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fibers in fifty seven seconds. And each one of those

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fibers can be aligned with a target star or galaxy,

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and that's the way you collect lots of information about

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very large numbers of galaxies and about their velocities, what

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we call their red shifts. So we'll get to that

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in a minute, because that's how we are so certain

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about these numbers, because of the ability to do that,

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to measure these very large numbers of galaxies what we

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call large girl surveys. But the story starts back in

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nineteen thirty three with Fritz Vicki, the man who famously

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called some of his colleagues not just bastards, they were

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spherical bustards. The reason for that was that they were

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bustards whichever way you looked at them. That's why call

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them spherical beasts. Astronomers love him, Yeah, I'm sure they do.

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I usually turned that down a bit and make it

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wrap bags. But for this show, I can reckon. I

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could quote him about him, it isn't quote.

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Therefore it's a quote. Yeah, part of it's a part

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of history.

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It is indeed part of history. But what he was

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doing was measuring cluster of galaxies actually in the Northern Hemisphere,

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consolation of Coma Baronesses, the Coma Cluster, a very rich

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cluster of galaxies, and he figured out that the he

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was measuring the motions of all the galaxies and when

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he looked at it, they're all going too fast for

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the gravity of what he could see to hold onto them.

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So if all that was there was what all he

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could see, then this cluster should have evaporated gazillions of

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years ago, and it hasn't. And he was the person

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who coined the term dark matter. He said, there's something

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there that we can't see. The astronomy basically ignored it

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because it was just too hard to get your head around.

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There's obviously something wrong, we don't know what it is.

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We'll go and do something else. And it wasn't until well,

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actually there was an Australian who in nineteen seventy Ken

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Freeman A and U still a good friend, He figured

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out that galaxies were rotating too fast for what was

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in them to hold them together, and that again was

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largely ignored that nineteen seventy result until VERA. Reuben basically

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did the same thing, but worked out that in order

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for galaxies to stay together and not fly apart as

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they rotate, they must all be enveloped in a sort

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of sphere or halo as we call it, of something

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we call dark matter, and that in nineteen seventy eight

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was the start of the modern era of dark matter.

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And so you can actually use those those measurements to

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make a crude estimate of what's missing. You know that

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you can say, use something called the virial theorem, which

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I've thought about for a long time, but that's what

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lets you weigh things by their motion. So you can

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weigh the dark matter by the motion of galaxies in

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a cluster, for example. You can then weigh what you

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can see because you know roughly how much stars weigh,

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and the stars are what you can see in the

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gas two, and then you can divide one by the

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other end you do get this sort of eighty ish percent.

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But the way that it's done today, as I've said,

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it involves these very large scale surveys of galaxies and

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their positions and velocities in you know, as much of

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the universe as you can see, very very large scale

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surveys involving millions of galaxies. And when you do that,

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you can make statistical deductions that tell you that the

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universe is made of something like seventy percent dark energy,

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about twenty percent dark matter, about five percent normal matter,

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most of which is hydrogen. So that comes from the

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large scale surveys, and it's because the positions of galaxies

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are actually determined by the gravitational forces.

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That they feel.

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And you know, that's the key to understanding dark matter

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and dark energy, to see how these forces stuck up.

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It's so hard to comprehend because when you say that

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five percent of the universe is made up of stars, planets,

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and gas, and you look out into space and see

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so many stars, so many other things, and yet you're

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only saying five percent of what is out there, it's

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it's mindblow, that's right.

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I mean some of that that figure of five percent

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is that when you look at it as a fraction

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of the mass and energy budget and energy and matter,

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you know they're interchangeable equals mc squared, and so it's

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when you do that something you realize that, yes, seventy

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percent of the mass energy budget of the universe is

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dark energy, twenty percent is dark matter, five percent thereabouts

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is his normal matter. But most of that normal matter

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is invisible to us because most of it's just cold hydrogen.

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The you know, the materials that make up the planets,

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in particular, the the you know, the normal elements that

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we see around us on Earth. There's a vanishingly small

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fraction of that that represents you know, their fraction within

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the universe.

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Yeah, all right, so that covers these eighty percent question.

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But he asks a question about what will be the

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next large telescope to be launched. What would you like

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it to be?

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Yeah, that's an interesting question. I mean, the thing that

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I'm looking forward to, and we'll see it online within

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the next probably two years, is the ELT, the extremely

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large telescope down in Chile that's going to be visible

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light telescope with a mirror thirty nine meters in diameter,

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and it will be able to observe because it's got

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this very sophisticated adaptive optic system that effectively puts it

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above the atmosphere. It is.

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It will have.

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Twenty times the resolution of the Hubble telescope. So if

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you've thought the Hubble images that you see have find

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detail in them, wait till you see what's going to

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come from the ELT, because it'll be twenty times better.

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And the reason why that's my favorite big telescope is

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that its cost has been almost since the beginning estimated

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at one point three billion euros and it still is.

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It's on budget and pretty well on time. And remember

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the James Web Telescope costs ten billion dollars to build, launch,

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and you know, and keep it going. As soon as

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you put things into space, their price tag goes up enormously,

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which is why I'm a big fan of ground based astronomy,

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especially when we now have sites like so Amazonas in

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northern Chile, which is where the ELT will be. Who's

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who's uh, you know, whose clarity and atmospheric stability you

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can hone with that adaptive opsic system that the telescope's

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got to be fitted with. So that's that's what I'm

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looking out for next. I don't think you need to

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launch anything else into space to get anywhere near what

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the ELT will do.

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Very exciting. Yeah, I heard they're going to have a

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visitors center at the el T, but the only thing

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on the menu will be BLT. So sorry had they

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do that joke? It just you know my brain doesn't

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let me stop something. No, I don't. Thank you Ben

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for the question. Great to hear from you. Let's talk

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I'm going to do a bit of a switcheroo here

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because we were already talking about telescopes, and we've got

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a question about telescopes, so we might just jump straight

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to that one. Hi, Fred and Andrew. Just wondering if

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Fred can shed some light pun fully intended on telescopes

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and the different types of light they can detect. I

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was recently thinking about how the James web Space telescope

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uses mirrors to observe infra red light but not visible light,

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while Hubble also uses mirrors for visible light yet can't

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really see infra red. That got me wondering how mirrors, detectors,

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and telescope design all come together or don't for different wavelengths.

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Could you please walk us through the various types of

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telescopes optical, infra red, radio all the way to gamma

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and explain what kinds of light they detect, how they

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do it, and why each telescope can only be used

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in certain ways. Absolutely loved the show. May Your Reign,

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May You Reign Supreme for many years to come. Cheese Ash,

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Thank you Ash, and he just wants to know everything

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you've ever written down a bed telescopes read.

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Yeah, there's a book on it. I recommend USh hunted out.

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It's called Stargaz's Other Life and Times of the Telescope.

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It's the first big, thick book that I wrote, and

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are still one of my favorites because even though it's

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slightly out of date. It opens by talking about what

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used to be called OWL, the overwhelmingly Large telescope, which

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was actually the precursor of the ELT. We were just

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talking about there. But when they were proposing OWL, which

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had an overwhelmingly large mirror of one hundred meters in diameter,

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and then they realized it also had an overwhelmingly large

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price tag, which is why it came down to thirty

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nine meters. And that's fine, because that's still.

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An extremely big telescope. Anyway.

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That's the plug over, that's the advert over. So basically,

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telescopes have sort of got the same ingredients no matter

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what they're observing, and that is something to gather at

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the radiation, and whether that's very short wavelength radiation like

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gamma rays or long wavelength radiation like radio waves, you've

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got something to gather the radiation and either focus it

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in some way or at least concentrate it, and then something.

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To detect it. And it's usually the.

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Detectors that are perhaps the most waveband critical, because you

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need different detectors, for example, to detect visible lights from

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the ones that you would use to detect infra red light.

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And again it depends on the infrared wavelength. So I

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guess starting right short wavelength end with gamma ray and

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X ray detectors. They are almost the same sort of

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technology as are used in medical imaging, but to focus

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them you've got to have very special technologies. My recollection

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of gamma ray telescopes and things might have changed a

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little bit here, but they made mirrors which were called

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grazing incidence mirrors, which looked more like a piece of

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origami than a reflector that you'd imagine, but they did

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focus the light to provide that thing. And then you

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go to ultraviolet. The hubble is sensitive to ultraviolet lights

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and that for that it needed a very precise mirror.

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And we all know that the mirror was made very precisely,

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but to the wrong prescription for reasons that we went

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time to go into. So once again, you know the

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detector is sensitive to ultraviolet radiation. In fact, they've got

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wide band quite wideband detectors. Hubble detect long wavelength ultraviolet

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whole of the visible and also the short wavelength infrared

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what we call the near infrared, and its mirror and

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detectors are capable of doing that. When you go up

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to the James Web, you're right, that's tuned for infrared light,

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and that means your tolerances on the accuracy of the

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mirror are slightly less because infrared light's got a longer wavelength,

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and you know, how accurate your mirror needs to be

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made is dependent on the wavelength. The longer the wavelength,

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the more relaxed you can be about the shape of

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the mirror. So Web telescope is slightly more relaxed, although

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still to very high tolerances. But the detectors are the

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thing that really render it not suitable for visible light.

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It's definitely got infrared sensitive detectors. It's also got a

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gold coating and that's so that rather than an aluminium

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or silver coating like a visible light telescope would have,

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it's got a gold coating because gold reflects in for

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red light better and then you get up to radio

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waves and you're talking about often dishes, and you know

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a dish is just a big mirror, but one that's

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as I said before, it doesn't have to be as

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accurate as the mirror on a visible light telescope because

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the wavelength is longer. And that's why we see these

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much bigger, bigger telescopes for radio waves.

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You get the.

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Same sensitivity to detail with a bigger dish than you

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do with visible light with a smaller dish. That's cause

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that sensitive to details proportional to the wavelength. But the

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detectors are quite different. In radio telescopes. They use often

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very sophisticated technologies where they're actually measuring the waveform itself,

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which you don't do with visible light what are called

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heterodyne receivers and things of that sort. So that's walking

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through the various types of telescopes, as you've suggested, is

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from another bit to the question how they do it? Well,

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I've explained that why each telescope can only be used

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in certain ways.

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Yeah, yeah, I guess the question he asks prompt a

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question in my mind or a suggestion that you really

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could not build a single telescope that could do absolutely

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everything you'd want to do on all spectrums.

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That's correct. There is a device which in fact is

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only used really in the microwave region.

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Of the spectrum.

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But it's called a bolometer, and a bolometer is something

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that is basically detect stuff, but it's insensitive to wavelengths.

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So in a sense, a bolometer, a perfect bilometer, will

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be able to detect all wavelengths. Now, the reality is

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you can't do that, but that's the notion behind a bilometer,

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and what it means is that for microwave astronomy, the

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bolometer gives you a very wide range of wavelengths to cover.

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So when you banning to build a telescope, do you

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have an objective in mind before you build it? Or

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do you build it and then think, well, what come.

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O you do?

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Is no, it's definitely the other way around. You you

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start off with the science case, what are the questions

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that we really think are the most urgent questions to answer?

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And you've got things like, you know, the nature of

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dark energy, the nature of dark matter, are there any

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living organisms anywhere else in the universe? All the questions

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that you and I talk about on the show are

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the ones that scientists are still intrigued by, and there

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are many others as well, the details of the way

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galaxies interact with the environments. What about all these young

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galaxies that seem to be more mature than we think

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they should be at you know, when the universe is

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only a couple hundred millionaiears or questions like that. They're

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all the ones that would go into the science case

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for a project. But there is always the background that

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you're going to find things out that you simply did

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not expect to find out, So that's usually added into

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the science case, the stuff that we just don't expect,

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serendipitous discovering. There's been so many of those made by

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the world's great telescopes.

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Yeah, thank you, Ash. That's a great question, and I

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could tell Fred was excited about it. I'm just going

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to go I'm going to go back to Ben's question

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about you know, what do you want the next big

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thing in telescopes to be. I've thought of one. I

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want to see the f WST in Fred Watson Space telescope.

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That's that's what I am said of that. Yeah, on

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the side of that, thank you, well, you're a pioneer

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in fiber optics. I mean, it makes sense to me

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that you should have one named after you.

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I always think the reason for my hairstyle is because

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I worked in fiber optics. Because the individual follicules got

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jealous of all these thin strands of material that I

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was playing with and they all just fell out.

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Yeah, they gave her. Yeah, so now we can't beat that.

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See later, friends, We're going somewhere else. Thanks Ash for

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the question. This is Space Nuts with Andrew Dunkley and

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Professor Fred Watson, a Q and A edition. Let's tell

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a peaceful online existence without digital disturbance. Open anguality, Babe,

388
00:23:40.880 --> 00:23:47.920
here the lambage space nuts. Next question comes from somebody else, Hi,

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00:23:48.079 --> 00:23:52.319
Fred Andrew. Gravity is described by Einstein's theories as the

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bending of space time in the presence of massive objects. Great,

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Why then, does physics discuss the hype anthetical graviton as

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a force carrier for gravity? What would a graviton look

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like were we to discover it or discover its existence?

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And why is it needed at all in the context

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of Einstein's theory? Thanks keep up the good work. Love

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