Richard Bond and George Efstathiou: meet the astrophysicists who are shaping our understanding of the early universe

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Hello, and welcome to the Physics World Weekly

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podcast.

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I'm Hamish Johnston.

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This episode is sponsored by the Shaw Prize

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Foundation.

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I'm very pleased to be joined by Richard

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Bond and George f Stathieu,

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who share the 2025

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Shaw Prize in Astronomy.

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The award is given for their pioneering research

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in cosmology,

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and in particular, for their studies of fluctuations

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in the cosmic microwave background,

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which is a relic of the early universe

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that permeates the cosmos.

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Their theoretical predictions of the nature of the

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cosmic microwave background have been verified

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by an armada of ground, balloon, and space

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based instruments,

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leading to precise determinations

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of the age, geometry,

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and mass energy content of the universe.

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The Shaw prize is an international prize based

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in Hong Kong.

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It consists of three annual

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awards.

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The prize in astronomy,

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the prize in life science and medicine,

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and the prize in mathematical sciences.

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Each prize carries a monetary

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award of 1,200,000.0

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US dollars.

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The prize was established by Runrun Shaw, a

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media mogul and philanthropist,

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and it was first presented

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in 02/2004.

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Now celebrating

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its twenty second anniversary,

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the prize has honored over 100

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individuals

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from across the world.

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This year, the Shaw prize is awarded to

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four

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distinguished

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scientists and mathematicians.

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They are Wolfgang

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Baumeister

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for life science and medicine,

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Kenji Fukaya

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for mathematical

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sciences,

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and Richard Bond and George f Stathieu

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for astronomy.

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George f Stathieu is Emeritus Professor of Astrophysics

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at the University of Cambridge in The UK,

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And Richard Bond is a professor

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at the Canadian Institute for Theoretical

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Astrophysics

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and university professor

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at the University of Toronto

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in Canada.

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They share the award equally.

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Richard and George,

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welcome to the podcast,

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and congratulations

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for winning this year's

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Shaw prize.

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So let's start off by setting the scene

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for your research.

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George, can you tell us a little bit

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about the cosmic microwave background?

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What is it?

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Okay. Well, our universe

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started off in a very hot and dense

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state,

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and,

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it was full of radiation.

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And as the universe has expanded,

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that radiation has cooled down,

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and we now observe it as an all

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pervasive,

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background radiation

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with a low temperature of 2.7

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Kelvin.

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So it was discovered,

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by Penzias and Wilson,

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back in,

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1965.

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And it was a

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a very, very significant discovery because,

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it confirmed

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that, you know, the universe must have started

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off in a in a hot and dense

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state. And so it excluded the steady state

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theory, which, you know,

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had a non evolving universe.

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So our universe,

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has been evolving

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and,

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has,

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evolved from this very hot then state to,

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the, you know, cold,

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radiation that we see today.

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And, Dick, can you just explain

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how,

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astronomers

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observe

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the the cosmic microwave background? What what what

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sort of instrumentation

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are they using, and and what are they

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actually seeing?

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Well, this has been a,

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great development. I mean, you know, we're

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honored for the theory in the microwave background,

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but,

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the the enabler has been the tremendous advances

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in technology, in particular, the, methodologies

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for detection

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and the ability to get

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into space, but also

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very remote locations on the ground and in

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balloons.

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The primary technologies that are used right now,

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there was a whole series of lower frequency

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things called,

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HEMPs, which I won't even tell you what

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they are. They involve transistors for the microwave,

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and they're more coherent,

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absorbers of radiation.

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But the one that, you know, has really

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made a huge difference in our subject

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are called the bolometers.

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And, essentially, what you're doing is you're measuring

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temperatures with bolometers. That is to say the

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microwave background comes in, and you are

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heating up,

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a solid state system,

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and then it's,

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relaxing back, and that

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allows the transform of,

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electrons, which you observe as currents.

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The reason I'm going into this little bit

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of detail

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is because there is this remarkable chain from

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what is out there on the sky

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through to what we actually see and process

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in order to be able to,

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extract the fundamental physics associated with this tremendous

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flow of signals that are, coming at us

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all the time carried by the microwave background.

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I see. And the radiation itself, it's it's

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microwaves.

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But am I right in thinking that it

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it it didn't start out

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as microwaves? We're we're seeing radiation

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from a very long time ago, and and

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therefore,

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it its wavelength has changed?

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That that's right. So so,

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the the radiation has a very accurate black

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body spectrum. In fact,

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the COBE satellite back in 09/1992

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measured the spectrum of the background,

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radiation, and it was,

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the most accurate black body that's ever been

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seen.

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So the temperature of 2.7

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Kelvin means that,

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it peaks at,

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millimeter wavelengths.

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And,

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but but as if if we go back

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in time, the temperature,

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is higher in the early universe.

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So,

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so what we see on the sky

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is the the temperature pattern,

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that was imprinted

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at the time that the universe had cooled

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to the point where,

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electrons and protons combined to make neutral hydrogen.

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So that happened about,

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you know, three hundred thousand years after the

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big bang. And so when we,

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make a picture of the the fluctuations

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over the sky, we're seeing this pattern imprinted

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as it was,

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when the universe was 300,000

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years old.

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So, you know, so a

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a direct measurement of the, of the very

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early universe.

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I see. And and so this,

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this radiation started off as

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light, and it's well, I suppose,

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visible light,

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and then it's it's been

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red shifted as the as the universe gets

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older and older?

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Yes. I mean, you know, I mean,

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you know, at at very early times,

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I mean, at the times that the

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fluctuations

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were generated,

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the the

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the energy of a photon,

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would have been about 11 orders of magnitude

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higher

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than the

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maximum energy achievable in the Large Hadron Collider.

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So super high energy.

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And, of course, that gives us access to

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to physics

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to physical mechanisms,

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that you just can't,

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ever access from accelerators on the ground.

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So you can test exotic yeah. You can

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test exotic physics in the early universe.

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And so so this is giving us, I

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suppose, a a picture of what the universe

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looked like

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very early on in its existence

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when it That's right. When it had an

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incredible

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energy density, a density that we could never

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well, I'll never say never.

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We could never study,

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on Earth.

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Yes. And and the observations

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fit with the theory

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in which,

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the

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fluctuations

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all of the structure in the universe,

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that we can see today,

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were generated from quantum fluctuations,

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that were

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expanded in scale as the universe,

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expanded faster than the speed of light. And

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that imprinted

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a a pattern of fluctuations, which we observe

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today.

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I see. And so these these fluctuations

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tell us about the early universe, but do

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do they also tell us about

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how what what's happened in the universe since

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then? How the the universe has expanded

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over the last, what is it, thirteen

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billion years?

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Yeah. Yeah. So,

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just to go back to George's point and

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your point,

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the

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energy,

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which was,

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in basically relativistic particles, this

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the current view is that there was a

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big

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event

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called heating or preheating

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after the early universe inflation

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in which all of the,

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basically energy,

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in matter

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got created as

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little fluctuations,

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but they were in all sorts of components.

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And

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as

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the universe cooled,

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and it's still unimaginably

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hot, but as it cooled,

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the form of the components changed.

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And so the remarkable thing is that the

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two main components

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that arose

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from the big bang

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were neutrinos

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and also the photons.

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But that's like the relic.

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And before that, it was in all sorts

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of different forms like positrons and electrons,

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very

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high energies, w mesons, and,

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and all of the quarks and gluons before

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they

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consolidated

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into,

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the protons and the neutrons, which then

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form the helium.

291
00:11:09,509 --> 00:11:11,290
So all of these different transmutations

292
00:11:11,910 --> 00:11:12,410
occurred.

293
00:11:12,950 --> 00:11:15,190
And one of the reasons that we can

294
00:11:15,190 --> 00:11:17,290
handle this story so well

295
00:11:17,750 --> 00:11:20,330
is because there is a conserved quantity,

296
00:11:20,790 --> 00:11:23,110
which I hesitate to bring it up, but

297
00:11:23,110 --> 00:11:25,574
George will at least laugh at me bringing

298
00:11:25,574 --> 00:11:27,195
it up. There's a

299
00:11:27,654 --> 00:11:29,115
a quantity called entropy,

300
00:11:29,815 --> 00:11:31,975
and the thing that was generated in the

301
00:11:31,975 --> 00:11:32,475
transformation

302
00:11:33,174 --> 00:11:35,274
from the early universe expansion,

303
00:11:36,855 --> 00:11:38,714
through this heating epic

304
00:11:39,519 --> 00:11:40,259
is the

305
00:11:40,639 --> 00:11:43,519
entropy, which is huge, really large in the

306
00:11:43,519 --> 00:11:46,799
universe. Some people say it's tiny. It's all

307
00:11:46,799 --> 00:11:47,779
eye of the beholder,

308
00:11:48,080 --> 00:11:49,440
but it's considered to be,

309
00:11:50,080 --> 00:11:51,839
but the main thing is that that is

310
00:11:51,839 --> 00:11:54,075
the conserved quantity more or less

311
00:11:54,875 --> 00:11:56,014
as all of the transmutations

312
00:11:56,634 --> 00:11:58,014
of forms occurred,

313
00:11:58,394 --> 00:12:00,554
which allow us to do the accounting with

314
00:12:00,554 --> 00:12:01,455
high accuracy.

315
00:12:02,315 --> 00:12:02,634
And,

316
00:12:03,514 --> 00:12:04,315
and so,

317
00:12:05,274 --> 00:12:06,894
what happens is that

318
00:12:08,154 --> 00:12:09,134
that entropic

319
00:12:10,090 --> 00:12:10,590
form,

320
00:12:11,049 --> 00:12:12,990
which is changing its nature,

321
00:12:15,370 --> 00:12:19,230
it starts to take different paths towards us.

322
00:12:19,769 --> 00:12:21,210
So prior to,

323
00:12:22,815 --> 00:12:25,054
what we call a redshift of 1,100, but

324
00:12:25,054 --> 00:12:26,414
George referred to it as,

325
00:12:28,014 --> 00:12:30,254
the three hundred and eighty thousand years after

326
00:12:30,254 --> 00:12:31,315
the big bang,

327
00:12:31,695 --> 00:12:34,914
that's when the electrons and protons combined.

328
00:12:35,600 --> 00:12:36,259
And that,

329
00:12:37,360 --> 00:12:40,740
meant that the electrons were not around to

330
00:12:41,440 --> 00:12:44,080
anchor the photons, and the photons, of which

331
00:12:44,080 --> 00:12:45,220
there were so many,

332
00:12:46,639 --> 00:12:47,700
started to stream

333
00:12:48,160 --> 00:12:49,700
freely towards us.

334
00:12:50,014 --> 00:12:51,855
And then they were encoding all of the

335
00:12:51,855 --> 00:12:53,794
information that occurred at that time.

336
00:12:54,254 --> 00:12:55,075
But in particular,

337
00:12:56,014 --> 00:12:56,495
they were,

338
00:12:57,054 --> 00:12:57,554
encoding

339
00:12:58,335 --> 00:13:01,394
the different forms of matter at the time.

340
00:13:01,934 --> 00:13:03,149
And so by,

341
00:13:03,790 --> 00:13:07,009
reading the signals in the cosmic microwave background

342
00:13:07,149 --> 00:13:07,649
fluctuations,

343
00:13:08,269 --> 00:13:11,170
which with these detectors that we talked about,

344
00:13:11,710 --> 00:13:14,769
exquisite work, we've been able to unravel

345
00:13:15,434 --> 00:13:18,254
what the constituents of the universe have been

346
00:13:18,394 --> 00:13:21,134
because of that split into the multiple forms.

347
00:13:21,674 --> 00:13:24,174
And the photons just keep giving,

348
00:13:24,554 --> 00:13:26,414
more light, pardon the expression,

349
00:13:26,955 --> 00:13:28,894
to us because it's revealed.

350
00:13:30,970 --> 00:13:33,529
It's not an exaggeration to say that the

351
00:13:33,529 --> 00:13:36,410
microwave background has revealed more about cosmology than

352
00:13:36,410 --> 00:13:39,290
anything else, including all of our observations of

353
00:13:39,290 --> 00:13:40,350
large scale structure.

354
00:13:40,809 --> 00:13:43,904
So it's very, very rich, and it continues

355
00:13:43,904 --> 00:13:45,605
to be extremely rich subject.

356
00:13:46,625 --> 00:13:48,625
I see. I I wanted to sort sort

357
00:13:48,625 --> 00:13:50,565
of focus in on these fluctuations

358
00:13:50,865 --> 00:13:53,825
with which both of you have studied. Now

359
00:13:53,825 --> 00:13:56,404
are these are these fluctuations, are they fluctuations

360
00:13:56,625 --> 00:13:57,125
in

361
00:13:57,720 --> 00:13:58,220
intensity

362
00:13:58,600 --> 00:14:02,059
or in the the temperature or wavelength of

363
00:14:02,279 --> 00:14:04,600
the cosmic radiation? Is it is it the

364
00:14:04,600 --> 00:14:05,100
polarization

365
00:14:06,279 --> 00:14:07,100
of the radiation

366
00:14:07,639 --> 00:14:09,899
of or is it all of the above?

367
00:14:10,200 --> 00:14:12,735
Is that how that this wealth of information

368
00:14:12,735 --> 00:14:14,334
is carried in the last say all of

369
00:14:14,334 --> 00:14:16,274
the above, but take over George.

370
00:14:17,054 --> 00:14:17,554
Well,

371
00:14:18,495 --> 00:14:19,954
so the the,

372
00:14:20,575 --> 00:14:22,754
fluctuations in intensity, which translates,

373
00:14:23,855 --> 00:14:26,034
one to one with fluctuations in temperature.

374
00:14:27,309 --> 00:14:28,110
The the,

375
00:14:29,070 --> 00:14:30,210
the pattern of fluctuations

376
00:14:30,750 --> 00:14:31,250
is,

377
00:14:32,110 --> 00:14:33,970
independent of wavelength and,

378
00:14:34,590 --> 00:14:37,309
you know, the physical process is the the

379
00:14:37,389 --> 00:14:37,889
we're,

380
00:14:39,389 --> 00:14:40,289
you know, analyzing.

381
00:14:42,495 --> 00:14:43,715
On on large scales,

382
00:14:44,174 --> 00:14:44,914
we see

383
00:14:45,615 --> 00:14:46,115
the

384
00:14:46,575 --> 00:14:47,955
variations in the gravitational

385
00:14:48,654 --> 00:14:49,154
potential,

386
00:14:50,174 --> 00:14:52,894
as they were created. They haven't evolved and

387
00:14:52,894 --> 00:14:54,914
so on. So it's going right back

388
00:14:55,215 --> 00:14:55,715
to,

389
00:14:56,279 --> 00:14:58,120
the very early universe, maybe 10 to the

390
00:14:58,120 --> 00:15:00,700
minus 32 seconds, you know,

391
00:15:01,959 --> 00:15:04,679
after the origin of the universe, something like

392
00:15:04,679 --> 00:15:05,179
that.

393
00:15:06,039 --> 00:15:06,539
So,

394
00:15:07,480 --> 00:15:10,279
and then on intermediate angular scales, what we

395
00:15:10,279 --> 00:15:10,779
see,

396
00:15:12,414 --> 00:15:14,495
the ripples of the, as Dick said, at

397
00:15:14,495 --> 00:15:17,315
very early times, the electrons and, photons

398
00:15:18,575 --> 00:15:19,955
act as a single fluid.

399
00:15:20,414 --> 00:15:21,955
And so the so you've

400
00:15:22,335 --> 00:15:23,315
the the fluctuations

401
00:15:23,774 --> 00:15:25,475
oscillate like sound waves.

402
00:15:26,620 --> 00:15:27,120
And,

403
00:15:28,379 --> 00:15:29,919
what we can what we,

404
00:15:31,100 --> 00:15:32,959
see on the sky,

405
00:15:33,659 --> 00:15:35,839
tells us about the the,

406
00:15:37,100 --> 00:15:38,240
the sound speed,

407
00:15:39,740 --> 00:15:41,600
you know, at at early times.

408
00:15:42,035 --> 00:15:44,695
And it's the fact that different constituents

409
00:15:45,315 --> 00:15:46,934
can alter the sound speed,

410
00:15:47,555 --> 00:15:49,095
that allows us to infer,

411
00:15:49,875 --> 00:15:51,955
what the universe was made of back in

412
00:15:51,955 --> 00:15:53,014
in those times.

413
00:15:54,240 --> 00:15:54,559
So,

414
00:15:55,120 --> 00:15:56,740
it's, you know, it's quite a rich,

415
00:15:58,639 --> 00:16:00,159
you you in a set of,

416
00:16:01,519 --> 00:16:02,980
you know, observables.

417
00:16:04,080 --> 00:16:04,820
In addition,

418
00:16:05,759 --> 00:16:07,620
the the coupling between,

419
00:16:08,159 --> 00:16:09,620
the photons and

420
00:16:10,054 --> 00:16:10,875
the electrons,

421
00:16:13,095 --> 00:16:15,034
is BDSU by Thompson scattering.

422
00:16:15,735 --> 00:16:17,995
And Thompson scattering is a

423
00:16:18,375 --> 00:16:18,875
anisotropic

424
00:16:19,254 --> 00:16:22,615
process. So if you illuminate the electrons with

425
00:16:22,615 --> 00:16:23,194
the quadripolar

426
00:16:23,495 --> 00:16:24,475
radiation pattern,

427
00:16:25,029 --> 00:16:28,009
then it can generate polarization and net polarization.

428
00:16:28,710 --> 00:16:30,889
And so the polarization has been observed,

429
00:16:31,429 --> 00:16:33,129
and it's been beautifully observed,

430
00:16:33,830 --> 00:16:35,450
now with the,

431
00:16:36,149 --> 00:16:37,289
Azakama Cosmology

432
00:16:37,830 --> 00:16:38,330
Telescope.

433
00:16:38,975 --> 00:16:39,475
And,

434
00:16:39,855 --> 00:16:41,315
the polarization pattern,

435
00:16:42,254 --> 00:16:43,634
tells us additional information,

436
00:16:44,654 --> 00:16:46,514
you know, in addition to the temperature fluctuations.

437
00:16:47,535 --> 00:16:49,315
And, ultimately, we might hope

438
00:16:49,935 --> 00:16:51,779
to find gravitational waves,

439
00:16:52,180 --> 00:16:55,160
by searching for the large angular scale polarization

440
00:16:55,779 --> 00:16:58,019
in the cosmic microwave background. But but just

441
00:16:58,019 --> 00:16:59,980
to jump in there, if I can for

442
00:16:59,980 --> 00:17:00,600
a second,

443
00:17:01,300 --> 00:17:03,860
when George and I were first doing our

444
00:17:03,860 --> 00:17:05,924
theoretical developments on this, which

445
00:17:07,445 --> 00:17:09,924
had a role in the development subject, we

446
00:17:09,924 --> 00:17:12,005
built polarization in from the very beginning. It

447
00:17:12,005 --> 00:17:13,384
was absolutely clear

448
00:17:14,005 --> 00:17:16,404
that it wasn't clear that we would be

449
00:17:16,404 --> 00:17:16,904
observing

450
00:17:17,205 --> 00:17:18,644
it, but it was clear that if you

451
00:17:18,644 --> 00:17:19,945
wanted accurate calculations,

452
00:17:20,419 --> 00:17:23,640
you had to include those anisotropic effects

453
00:17:24,500 --> 00:17:27,480
that George was talking about. So, you know,

454
00:17:27,539 --> 00:17:29,400
theoretically, we were well prepared

455
00:17:29,940 --> 00:17:31,400
for everything that came

456
00:17:32,099 --> 00:17:32,599
ahead.

457
00:17:32,900 --> 00:17:34,200
And not only that,

458
00:17:34,500 --> 00:17:35,319
it stimulated

459
00:17:36,255 --> 00:17:37,234
the experiments

460
00:17:38,015 --> 00:17:38,595
to be

461
00:17:40,494 --> 00:17:42,335
developed in a form that they would be

462
00:17:42,335 --> 00:17:43,634
able to go after this.

463
00:17:44,494 --> 00:17:44,994
Heroic

464
00:17:45,535 --> 00:17:47,454
that we were able to get to the

465
00:17:47,454 --> 00:17:48,755
really tiny levels

466
00:17:49,159 --> 00:17:52,119
of ripples in the sky in the microwave

467
00:17:52,119 --> 00:17:52,940
background radiation

468
00:17:53,640 --> 00:17:54,940
to actually observe it.

469
00:17:55,480 --> 00:17:56,700
But we have with

470
00:17:57,159 --> 00:17:57,659
incredible,

471
00:17:58,359 --> 00:17:58,859
exquisiteness,

472
00:17:59,720 --> 00:18:02,599
modulo that one thing that George talked about,

473
00:18:02,599 --> 00:18:05,445
which was I call the seventh pillar of

474
00:18:05,445 --> 00:18:06,424
the many pillars

475
00:18:06,884 --> 00:18:07,545
that we've,

476
00:18:09,285 --> 00:18:11,625
observed with the microwave background, which is,

477
00:18:12,565 --> 00:18:15,945
the influence of ultra early universe gravity waves

478
00:18:16,484 --> 00:18:18,105
having an effect on the photons,

479
00:18:18,640 --> 00:18:19,599
which can then be,

480
00:18:20,559 --> 00:18:23,140
observed by the same techniques that we're observing,

481
00:18:23,759 --> 00:18:26,319
but it's a very small signal and rather

482
00:18:26,319 --> 00:18:27,700
difficult to go after.

483
00:18:28,000 --> 00:18:30,240
There's a lot of effort right now for

484
00:18:30,240 --> 00:18:33,525
us going after it. There always was, but

485
00:18:33,525 --> 00:18:35,204
we have to go deeper and deeper and

486
00:18:35,204 --> 00:18:37,605
deeper to try and unearth it if we

487
00:18:37,605 --> 00:18:38,664
can unearth it.

488
00:18:39,284 --> 00:18:40,904
So the the the structure,

489
00:18:41,765 --> 00:18:44,345
that existed in the early universe that

490
00:18:45,390 --> 00:18:48,210
was imprinted onto the cosmic microwave background.

491
00:18:49,470 --> 00:18:51,630
Is that something that we can see in

492
00:18:51,630 --> 00:18:52,849
the universe today?

493
00:18:53,309 --> 00:18:55,549
I mean, for example, you know, we've got

494
00:18:55,549 --> 00:18:58,509
distributions of galaxies, and they seem to be

495
00:18:58,509 --> 00:19:00,769
connected in in this sort of web

496
00:19:01,444 --> 00:19:04,184
type thing. Is that is that something that

497
00:19:04,325 --> 00:19:04,825
that

498
00:19:05,765 --> 00:19:06,585
that evolved

499
00:19:06,884 --> 00:19:07,865
along with the

500
00:19:08,164 --> 00:19:09,865
cosmic microwave background?

501
00:19:10,644 --> 00:19:12,904
The microwave background is, basically

502
00:19:14,920 --> 00:19:17,259
giving an earlier image of

503
00:19:17,559 --> 00:19:20,920
what evolved into the current cosmic web of

504
00:19:20,920 --> 00:19:22,140
interconnected structures.

505
00:19:22,680 --> 00:19:24,200
And the emphasis that I like to put

506
00:19:24,200 --> 00:19:25,259
on this is that,

507
00:19:26,119 --> 00:19:28,528
you you know, it used to be that

508
00:19:28,528 --> 00:19:31,080
astronomy was about independent objects, and you'd say,

509
00:19:31,080 --> 00:19:33,633
oh, look at that. There's a galaxy there,

510
00:19:33,633 --> 00:19:36,185
a galaxy there. But the emphasis that grew

511
00:19:36,185 --> 00:19:38,738
partly probably out of the microwave background and

512
00:19:38,738 --> 00:19:41,290
the insight of its relationship to the early

513
00:19:41,290 --> 00:19:44,250
universe is that everything is interconnected with everything

514
00:19:44,250 --> 00:19:45,789
else that's kind of a tautology.

515
00:19:46,490 --> 00:19:49,130
But nonetheless, it's a profound thing that we

516
00:19:49,130 --> 00:19:50,589
have learned that the universe

517
00:19:51,049 --> 00:19:53,470
so if you're dealing with an object somewhere,

518
00:19:53,884 --> 00:19:56,684
it's being, disturbed and affected by all of

519
00:19:56,684 --> 00:19:58,845
the objects around it, and it all sort

520
00:19:58,845 --> 00:20:01,025
of becomes this cosmic web.

521
00:20:01,404 --> 00:20:01,904
So

522
00:20:03,164 --> 00:20:05,485
in effect, we are observing the cosmic web.

523
00:20:05,485 --> 00:20:07,759
It's just at a much earlier time.

524
00:20:08,220 --> 00:20:10,159
So, I mean, the the fluctuations

525
00:20:10,619 --> 00:20:12,240
in the cosmic microwave background,

526
00:20:14,299 --> 00:20:16,159
they they correspond to

527
00:20:16,700 --> 00:20:17,200
irregularities

528
00:20:17,579 --> 00:20:19,980
of about a thousandth of a percent. They're

529
00:20:19,980 --> 00:20:21,194
they're they're tiny.

530
00:20:22,154 --> 00:20:22,654
And,

531
00:20:23,434 --> 00:20:24,974
the the challenge for,

532
00:20:25,674 --> 00:20:28,075
cosmology is to, you know, you start off

533
00:20:28,075 --> 00:20:29,375
with these tiny

534
00:20:29,755 --> 00:20:30,255
fluctuations,

535
00:20:30,875 --> 00:20:32,654
thousandth of a percent in amplitude,

536
00:20:33,274 --> 00:20:35,259
and you want to understand all of the

537
00:20:35,259 --> 00:20:36,400
structure that's formed

538
00:20:37,339 --> 00:20:39,680
since then. Now to put that in context,

539
00:20:40,140 --> 00:20:40,640
the

540
00:20:41,019 --> 00:20:42,160
density contrast

541
00:20:42,460 --> 00:20:45,200
in a typical galaxy is over a million.

542
00:20:46,154 --> 00:20:46,654
So

543
00:20:47,195 --> 00:20:49,775
gravity has taken these tiny fluctuations,

544
00:20:50,715 --> 00:20:52,414
and the action of gravity,

545
00:20:53,434 --> 00:20:56,715
has amplified these fluctuations and produced these very

546
00:20:56,715 --> 00:20:57,615
highly nonlinear,

547
00:20:58,634 --> 00:20:59,134
objects.

548
00:20:59,434 --> 00:21:01,215
The amazing thing is

549
00:21:01,589 --> 00:21:02,089
that

550
00:21:02,390 --> 00:21:05,750
starting off with the tiny fluctuations that we

551
00:21:05,750 --> 00:21:07,049
observe from the CMB,

552
00:21:08,789 --> 00:21:09,690
the we

553
00:21:10,549 --> 00:21:12,009
we could get,

554
00:21:12,869 --> 00:21:14,089
through computer simulations,

555
00:21:15,524 --> 00:21:18,325
really quite good matches to what we observe

556
00:21:18,325 --> 00:21:20,345
today with very highly nonlinear

557
00:21:21,125 --> 00:21:22,664
fluctuations. So it's a remarkable,

558
00:21:23,845 --> 00:21:25,625
you know, it's a remarkable achievement.

559
00:21:26,565 --> 00:21:27,865
And I I just have one

560
00:21:28,500 --> 00:21:30,759
one more question about these fluctuations.

561
00:21:31,220 --> 00:21:33,619
As you mentioned, George, they are really, really

562
00:21:33,619 --> 00:21:34,119
tiny.

563
00:21:34,660 --> 00:21:37,619
And I've often wondered how, you know, how

564
00:21:37,619 --> 00:21:40,519
have these tiny fluctuations survived for

565
00:21:41,225 --> 00:21:43,625
all that time? You know, why are they

566
00:21:43,625 --> 00:21:46,345
still there? Why why weren't they sort of

567
00:21:46,345 --> 00:21:46,845
scrambled

568
00:21:47,705 --> 00:21:50,445
as they you know, as that radiation moved

569
00:21:50,825 --> 00:21:53,545
through the universe, as the universe expanded? Or

570
00:21:53,545 --> 00:21:54,904
are we just lucky that,

571
00:21:55,669 --> 00:21:58,470
that they're still there, or it it it

572
00:21:58,470 --> 00:22:01,109
it is there a a I'm sure there

573
00:22:01,109 --> 00:22:03,210
is a good reason for why the fluctuations

574
00:22:03,589 --> 00:22:05,210
persist to this day.

575
00:22:06,549 --> 00:22:09,029
Well well, they do something that, we call,

576
00:22:09,429 --> 00:22:11,144
collisionless damping. That is

577
00:22:13,144 --> 00:22:13,785
to say, they do diminish. They diminish because

578
00:22:13,785 --> 00:22:15,805
they're flowing around here, there, and everywhere.

579
00:22:16,424 --> 00:22:16,924
But,

580
00:22:17,865 --> 00:22:19,305
it happens to be big enough for us

581
00:22:19,305 --> 00:22:20,045
to see them.

582
00:22:20,744 --> 00:22:21,565
And so

583
00:22:22,105 --> 00:22:22,765
you know?

584
00:22:24,470 --> 00:22:26,789
But they are basically, at some level, trying

585
00:22:26,789 --> 00:22:27,529
to uniformize.

586
00:22:28,470 --> 00:22:28,970
However,

587
00:22:29,670 --> 00:22:31,910
there's a fundamental answer here. I shouldn't go

588
00:22:31,910 --> 00:22:33,910
into it, but I'll put the word out.

589
00:22:33,910 --> 00:22:35,990
Entropy is associated with this. That is to

590
00:22:35,990 --> 00:22:36,375
say,

591
00:22:37,015 --> 00:22:39,275
there's a conservation of the number

592
00:22:39,654 --> 00:22:40,474
of photons,

593
00:22:42,134 --> 00:22:43,914
which is that the

594
00:22:44,375 --> 00:22:47,595
basic patterns are, are effectively conserved,

595
00:22:48,055 --> 00:22:50,470
and that's, you know, we we understand this

596
00:22:50,470 --> 00:22:52,809
extremely well. That's part of the way we

597
00:22:53,109 --> 00:22:55,910
actually calculate what to see on Scott. That

598
00:22:55,910 --> 00:22:57,849
maybe another point to emphasize,

599
00:22:58,549 --> 00:22:58,710
which,

600
00:23:01,615 --> 00:23:04,255
when we have got all of these new

601
00:23:04,255 --> 00:23:06,434
observations with such exquisite detail,

602
00:23:07,375 --> 00:23:09,315
the comparison with the theory

603
00:23:09,934 --> 00:23:10,914
and the observations,

604
00:23:11,775 --> 00:23:13,954
you can't essentially tell the difference.

605
00:23:14,299 --> 00:23:17,119
The lines are essentially exactly the same.

606
00:23:17,579 --> 00:23:18,059
So,

607
00:23:18,539 --> 00:23:21,839
there's something really right about the fundamental

608
00:23:22,140 --> 00:23:23,200
underlying theory

609
00:23:23,500 --> 00:23:26,460
that we have describing this, and then we

610
00:23:26,460 --> 00:23:28,894
take the results from these early times.

611
00:23:29,434 --> 00:23:31,674
And and George is one of the great

612
00:23:31,674 --> 00:23:34,174
pioneers of this subject, which is,

613
00:23:34,795 --> 00:23:37,914
called n body studies, which is describing the

614
00:23:37,914 --> 00:23:39,055
growth into nonlinearity.

615
00:23:40,220 --> 00:23:41,660
And I and I work on it too.

616
00:23:41,660 --> 00:23:43,599
That's the cosmic web whole story.

617
00:23:45,019 --> 00:23:48,059
Everything falls into place. It's just amazing. So

618
00:23:48,059 --> 00:23:49,359
it's essentially like

619
00:23:49,660 --> 00:23:51,759
you you know, the standard story we have

620
00:23:52,059 --> 00:23:52,700
is that,

621
00:23:53,900 --> 00:23:55,805
which which is seems to be the correct

622
00:23:55,805 --> 00:23:57,984
story is that we essentially, the

623
00:23:58,365 --> 00:23:58,865
information

624
00:23:59,325 --> 00:24:01,664
in the universe is encoded in effectively

625
00:24:02,285 --> 00:24:02,785
seven

626
00:24:03,244 --> 00:24:04,224
cosmic parameters

627
00:24:04,845 --> 00:24:06,924
and that everything flows from that. Well, that's

628
00:24:06,924 --> 00:24:07,664
an amazing

629
00:24:09,000 --> 00:24:09,500
simplification.

630
00:24:10,759 --> 00:24:13,480
We're actually hoping for more cosmic parameters so

631
00:24:13,480 --> 00:24:14,859
we can get more information,

632
00:24:15,400 --> 00:24:17,580
but the fact that we've got these exquisitely

633
00:24:17,799 --> 00:24:20,299
determined seven parameters or six parameters

634
00:24:21,464 --> 00:24:23,944
is, been one of the real triumphs, and

635
00:24:23,944 --> 00:24:24,924
it's such a privilege

636
00:24:25,545 --> 00:24:27,865
for us to have been, part of throughout

637
00:24:27,865 --> 00:24:30,105
all of the decades in in the development

638
00:24:30,105 --> 00:24:30,924
of this story.

639
00:24:31,305 --> 00:24:33,164
Yeah. Now I just wanted to add something

640
00:24:33,224 --> 00:24:34,444
about the survival

641
00:24:35,144 --> 00:24:35,644
of,

642
00:24:36,400 --> 00:24:37,539
fluctuations because

643
00:24:38,320 --> 00:24:41,059
because an absolutely key aspect

644
00:24:41,920 --> 00:24:42,420
of,

645
00:24:44,320 --> 00:24:45,380
generating fluctuations

646
00:24:45,759 --> 00:24:48,079
that we, you know, that can grow to

647
00:24:48,079 --> 00:24:48,820
make nonlinear

648
00:24:49,279 --> 00:24:51,404
structure today is the fact that

649
00:24:53,205 --> 00:24:54,465
the universe has,

650
00:24:56,525 --> 00:24:59,085
the the matter content is dominated by cold

651
00:24:59,085 --> 00:25:00,865
dark matter, by dark matter.

652
00:25:02,045 --> 00:25:04,640
Without that, we couldn't make models

653
00:25:05,259 --> 00:25:07,279
that that work and reproduce our universe.

654
00:25:08,380 --> 00:25:10,080
So it's the fact that there's a component

655
00:25:10,700 --> 00:25:12,000
that doesn't interact

656
00:25:12,380 --> 00:25:14,880
with ordinary matter or photons,

657
00:25:15,980 --> 00:25:17,440
that leads to the survivability

658
00:25:17,820 --> 00:25:18,194
of

659
00:25:18,835 --> 00:25:20,994
fluctuations that grow to make structure in the

660
00:25:20,994 --> 00:25:21,894
universe today.

661
00:25:22,514 --> 00:25:24,375
That was the reason George and I,

662
00:25:25,474 --> 00:25:27,954
joined hands and, did the theory of the

663
00:25:27,954 --> 00:25:30,674
microwave background. It was because of the cold

664
00:25:30,674 --> 00:25:34,259
dark the dark matter. We still had the

665
00:25:34,259 --> 00:25:36,500
issue, and we still do, of exactly what

666
00:25:36,500 --> 00:25:38,500
the form of the dark matter is. There

667
00:25:38,500 --> 00:25:40,820
are certain universal forms of which cold dark

668
00:25:40,820 --> 00:25:43,460
matter is one. We actually started in hot

669
00:25:43,460 --> 00:25:45,400
dark matter, which is massive neutrinos.

670
00:25:45,700 --> 00:25:48,575
That's how George and I got together on

671
00:25:48,575 --> 00:25:50,815
a scientific project, and the rest has been

672
00:25:50,815 --> 00:25:52,035
history, of course. But,

673
00:25:53,214 --> 00:25:53,795
a great

674
00:25:54,174 --> 00:25:55,714
pleasure, but the motivation

675
00:25:56,575 --> 00:25:58,355
was the dark matter issue

676
00:25:58,654 --> 00:26:00,994
in order to see how we could

677
00:26:02,039 --> 00:26:04,460
determine the response of the microwave background

678
00:26:05,000 --> 00:26:07,259
essentially to the existence of dark matter

679
00:26:07,559 --> 00:26:09,900
as the main organizing component

680
00:26:10,279 --> 00:26:11,740
for the structure of the universe.

681
00:26:12,200 --> 00:26:14,360
At that time, we weren't talking about the

682
00:26:14,360 --> 00:26:14,860
cosmological

683
00:26:15,400 --> 00:26:16,220
dark energy

684
00:26:16,904 --> 00:26:18,585
that came along a little later, not too

685
00:26:18,585 --> 00:26:20,765
much later, but a little bit later, theoretically.

686
00:26:21,465 --> 00:26:23,805
But we really had the context

687
00:26:24,505 --> 00:26:27,465
even way back when in the, in the

688
00:26:27,465 --> 00:26:28,924
relatively early eighties.

689
00:26:29,740 --> 00:26:32,140
So so, you know, if if people's if

690
00:26:32,140 --> 00:26:32,640
people

691
00:26:33,339 --> 00:26:34,319
express skepticism

692
00:26:35,419 --> 00:26:37,659
about dark matter, you know, the does it

693
00:26:37,659 --> 00:26:39,039
really exist? You know?

694
00:26:40,140 --> 00:26:41,819
And so we would not be able to

695
00:26:41,980 --> 00:26:44,284
we wouldn't come close to making sense of

696
00:26:44,284 --> 00:26:45,744
the cosmic microwave background

697
00:26:46,125 --> 00:26:47,105
without dark

698
00:26:47,644 --> 00:26:50,444
matter. Right. And does that also apply to

699
00:26:50,444 --> 00:26:53,025
to dark energy? Does does does that,

700
00:26:54,365 --> 00:26:56,684
having some sort of concept of dark energy,

701
00:26:56,684 --> 00:26:59,099
is that is that needed when you're trying

702
00:26:59,099 --> 00:27:00,720
to understand Yes.

703
00:27:01,259 --> 00:27:02,799
Yes. When when you get to,

704
00:27:03,700 --> 00:27:04,640
you know,

705
00:27:05,099 --> 00:27:06,160
detailed comparisons,

706
00:27:06,859 --> 00:27:08,000
then you need,

707
00:27:08,380 --> 00:27:09,359
the dark energy

708
00:27:10,220 --> 00:27:11,679
to understand the amplitude

709
00:27:12,055 --> 00:27:12,875
of the fluctuations.

710
00:27:14,295 --> 00:27:15,994
But but the the the

711
00:27:16,455 --> 00:27:17,994
the the actual characteristics,

712
00:27:18,375 --> 00:27:19,515
the pan, the fluctuations,

713
00:27:21,654 --> 00:27:24,535
you wouldn't come close to replicating them without

714
00:27:24,535 --> 00:27:26,869
the cold dark matter. So so, you know,

715
00:27:26,869 --> 00:27:29,049
if you you you can think of the

716
00:27:29,509 --> 00:27:30,009
the

717
00:27:30,549 --> 00:27:33,429
impact of dark energies to change the overall

718
00:27:33,429 --> 00:27:35,929
level, the overall amplitude of the fluctuations,

719
00:27:36,630 --> 00:27:39,130
but the dark matter changes the shape drastically.

720
00:27:40,265 --> 00:27:41,484
So for a long time,

721
00:27:42,825 --> 00:27:44,904
at least, you you know, there was the,

722
00:27:45,304 --> 00:27:47,865
discovery of acceleration of the universe with the

723
00:27:47,865 --> 00:27:50,605
supernova data, which I won't get into here.

724
00:27:51,065 --> 00:27:53,804
But the way we got at dark energy

725
00:27:54,105 --> 00:27:54,424
from

726
00:27:55,880 --> 00:27:58,779
it was microwave background plus large scale structure,

727
00:27:58,839 --> 00:28:01,480
that is to say the movement towards the

728
00:28:01,480 --> 00:28:04,839
nonlinear structures that George was talking about. That

729
00:28:05,079 --> 00:28:06,700
it it was the two in combination

730
00:28:07,345 --> 00:28:10,065
that were able for us to show from

731
00:28:10,065 --> 00:28:11,845
that structural point of view

732
00:28:12,305 --> 00:28:13,285
why the cosmological

733
00:28:13,664 --> 00:28:16,625
constant or dark you know, it it may

734
00:28:16,625 --> 00:28:18,005
not be constant, but,

735
00:28:19,265 --> 00:28:20,245
why it's needed.

736
00:28:21,390 --> 00:28:21,890
Then

737
00:28:22,509 --> 00:28:24,130
and we didn't talk about this.

738
00:28:25,630 --> 00:28:27,150
One of the things that happens to the

739
00:28:27,150 --> 00:28:30,509
microwave photons is they're propagating to us. They're

740
00:28:30,509 --> 00:28:31,650
streaming freely,

741
00:28:32,029 --> 00:28:34,049
but they're following what are called geodesics,

742
00:28:34,724 --> 00:28:36,804
which means that they move in and out

743
00:28:36,804 --> 00:28:38,345
depending upon what the,

744
00:28:39,365 --> 00:28:41,944
gravitational field is. This is called,

745
00:28:44,565 --> 00:28:45,065
gravitational

746
00:28:45,365 --> 00:28:47,204
lensing, and in this case, this is the

747
00:28:47,204 --> 00:28:48,184
microwave background.

748
00:28:48,730 --> 00:28:50,569
And so all of the structures that are

749
00:28:50,569 --> 00:28:51,529
in front of us are

750
00:28:52,250 --> 00:28:54,649
the photons are propagating through them, and they're

751
00:28:54,649 --> 00:28:55,950
bending and they're amplifying,

752
00:28:56,730 --> 00:28:57,549
and that

753
00:28:58,009 --> 00:29:00,990
we have been now seeing as a tremendous

754
00:29:01,289 --> 00:29:02,589
signal for us

755
00:29:02,894 --> 00:29:05,474
in order to unravel a lot of information

756
00:29:05,695 --> 00:29:06,195
about

757
00:29:06,575 --> 00:29:08,654
the structures that are in front of what

758
00:29:08,654 --> 00:29:10,815
you would have called the microwave background, which

759
00:29:10,815 --> 00:29:11,934
is released at,

760
00:29:12,894 --> 00:29:14,815
three hundred and eighty thousand years after the

761
00:29:14,815 --> 00:29:17,134
Big Bang. So it's been incredibly rich. And

762
00:29:17,134 --> 00:29:18,515
the reason I brought it up

763
00:29:18,869 --> 00:29:21,029
is because if you use that with the

764
00:29:21,029 --> 00:29:24,009
microwave background, so it's all microwave background, basically,

765
00:29:24,630 --> 00:29:25,849
you can get the cosmological

766
00:29:26,150 --> 00:29:28,250
constant to a high degree

767
00:29:28,549 --> 00:29:29,930
of precision now, actually.

768
00:29:30,390 --> 00:29:33,029
I see. Okay. And the other the other

769
00:29:33,029 --> 00:29:33,910
thing that you can do,

770
00:29:35,164 --> 00:29:37,984
with that is that you can cross correlate

771
00:29:38,444 --> 00:29:41,025
the lensing of the cosmic microwave background

772
00:29:41,804 --> 00:29:42,304
with,

773
00:29:42,845 --> 00:29:45,744
you know, galaxy surveys and any other tracer,

774
00:29:47,005 --> 00:29:47,984
at low redshift.

775
00:29:49,369 --> 00:29:51,529
And that gives you a topographic way of

776
00:29:51,529 --> 00:29:54,250
understanding how structure has evolved as a function

777
00:29:54,250 --> 00:29:56,250
of time. And so, you know, with the

778
00:29:56,250 --> 00:29:58,569
cosmic microwave background, we'd tell you what the

779
00:29:58,569 --> 00:30:00,890
universe was like three hundred and eighty thousand

780
00:30:00,890 --> 00:30:01,390
years

781
00:30:02,144 --> 00:30:02,644
after

782
00:30:02,945 --> 00:30:04,404
the the big bang.

783
00:30:05,345 --> 00:30:07,205
But now you can you can

784
00:30:07,585 --> 00:30:09,525
look at how that structure has evolved,

785
00:30:10,465 --> 00:30:11,285
to to,

786
00:30:12,144 --> 00:30:14,190
to low red shift when the universe was

787
00:30:14,349 --> 00:30:15,649
was, you know,

788
00:30:16,269 --> 00:30:17,649
half its present age.

789
00:30:19,789 --> 00:30:21,950
Okay. So, I mean, it sounds like there's

790
00:30:21,950 --> 00:30:25,230
lots of amazing information that can be gleaned

791
00:30:25,230 --> 00:30:27,869
from the cosmic microwave background. But I I

792
00:30:27,869 --> 00:30:29,924
I wanted to take both of you back

793
00:30:29,924 --> 00:30:30,424
to,

794
00:30:31,205 --> 00:30:33,205
the, you know, the work that you've done,

795
00:30:33,205 --> 00:30:35,525
the the sort of theory and models that

796
00:30:35,525 --> 00:30:36,265
you've developed

797
00:30:36,644 --> 00:30:37,545
that have allowed,

798
00:30:38,565 --> 00:30:42,244
us to interpret the cosmic microwave background. It

799
00:30:42,244 --> 00:30:44,250
sounds, I mean, it sounds like a really

800
00:30:44,250 --> 00:30:46,730
difficult thing to do, you know, just listening

801
00:30:46,730 --> 00:30:47,549
to your description

802
00:30:48,330 --> 00:30:50,410
of of the early universe. It was a

803
00:30:50,410 --> 00:30:50,910
very

804
00:30:51,769 --> 00:30:53,950
violent, very hot place with,

805
00:30:54,730 --> 00:30:57,529
you know, maybe some nuclear physics going on

806
00:30:57,529 --> 00:30:58,430
as well as

807
00:30:59,095 --> 00:31:00,634
electromagnetic and gravitational

808
00:31:01,014 --> 00:31:01,514
interactions.

809
00:31:02,134 --> 00:31:05,974
How how did you begin to to to

810
00:31:05,974 --> 00:31:07,115
look at that,

811
00:31:08,375 --> 00:31:11,335
sort of state of the universe and begin

812
00:31:11,335 --> 00:31:13,115
to understand how it would

813
00:31:13,920 --> 00:31:17,360
create the cosmic microwave background and how that

814
00:31:17,360 --> 00:31:18,100
would evolve

815
00:31:18,559 --> 00:31:20,580
to what we see today. What

816
00:31:21,119 --> 00:31:22,820
where did where did you begin

817
00:31:23,440 --> 00:31:25,519
when you when you started to look at

818
00:31:25,519 --> 00:31:26,019
this?

819
00:31:26,515 --> 00:31:28,515
Well, it's it's it's actually a much simpler

820
00:31:28,515 --> 00:31:29,894
problem than than,

821
00:31:31,714 --> 00:31:33,335
than you described because,

822
00:31:33,954 --> 00:31:36,295
the universe at very early times was in

823
00:31:36,674 --> 00:31:37,815
in thermal equilibrium.

824
00:31:38,759 --> 00:31:40,920
So it was very accurately in thermal equilibrium.

825
00:31:40,920 --> 00:31:42,359
So you don't really have to worry about

826
00:31:42,359 --> 00:31:43,180
all of the

827
00:31:43,559 --> 00:31:46,440
particles that were generated and the interactions and

828
00:31:46,440 --> 00:31:47,660
and so on.

829
00:31:48,519 --> 00:31:49,019
So,

830
00:31:51,484 --> 00:31:53,644
Yeah. So the problem, you know, is is

831
00:31:53,644 --> 00:31:56,144
is much simpler. You break it down into,

832
00:31:58,204 --> 00:32:01,484
the the important constituents. So so radiation and

833
00:32:01,484 --> 00:32:01,984
radicals

834
00:32:02,764 --> 00:32:03,744
is one constituent.

835
00:32:05,119 --> 00:32:05,599
Then,

836
00:32:06,079 --> 00:32:08,640
neutrinos at at late times because neutrinos are

837
00:32:08,640 --> 00:32:09,380
not coupled

838
00:32:10,159 --> 00:32:10,819
to the photons

839
00:32:11,440 --> 00:32:12,339
and and,

840
00:32:13,359 --> 00:32:13,859
baryons.

841
00:32:14,880 --> 00:32:15,539
And then,

842
00:32:16,894 --> 00:32:17,714
you know, baryons,

843
00:32:18,414 --> 00:32:21,454
is an ionized component that's tightly coupled to

844
00:32:21,454 --> 00:32:23,775
to the radiation. So that's so you simplify

845
00:32:23,775 --> 00:32:24,434
the system

846
00:32:24,734 --> 00:32:26,654
down to a small number of components. You

847
00:32:26,654 --> 00:32:29,160
don't worry about, you know, all of the,

848
00:32:29,320 --> 00:32:30,140
you know, very,

849
00:32:32,039 --> 00:32:32,779
the the particles

850
00:32:33,400 --> 00:32:35,019
that have, you know, formed,

851
00:32:35,960 --> 00:32:37,500
at very, very early times.

852
00:32:38,359 --> 00:32:40,920
So, yeah, it's not as complicated as you

853
00:32:40,920 --> 00:32:41,595
might imagine.

854
00:32:42,474 --> 00:32:43,775
It's really complicated.

855
00:32:46,954 --> 00:32:47,355
So,

856
00:32:48,075 --> 00:32:50,095
just to play off of that,

857
00:32:51,434 --> 00:32:53,994
when we were really first getting into the

858
00:32:53,994 --> 00:32:54,494
game,

859
00:32:55,595 --> 00:32:57,119
there was an issue of

860
00:32:57,680 --> 00:32:59,380
what happened at high temperatures,

861
00:33:00,480 --> 00:33:02,720
what the species were, but it was pretty

862
00:33:02,720 --> 00:33:04,640
clear that it, you know, you would always

863
00:33:04,640 --> 00:33:06,819
have the electrons and the protons.

864
00:33:07,279 --> 00:33:10,500
And and, there was a huge subject area

865
00:33:11,075 --> 00:33:13,875
in the, in the sixties, but in particular

866
00:33:13,875 --> 00:33:16,934
in the seventies. It's called big bang nucleosynthesis

867
00:33:18,115 --> 00:33:18,855
in which,

868
00:33:19,875 --> 00:33:21,255
it was shown that,

869
00:33:22,434 --> 00:33:24,855
well, first of all, that's the period when

870
00:33:25,549 --> 00:33:28,289
this huge neutrino sea of particles

871
00:33:29,390 --> 00:33:31,710
decoupled. So what what we're seeing with the

872
00:33:31,710 --> 00:33:34,049
microwave background is when the photons decoupled.

873
00:33:34,910 --> 00:33:36,670
And so that's the three hundred and eighty

874
00:33:36,670 --> 00:33:38,714
thousand years, but the proverbial

875
00:33:39,174 --> 00:33:39,674
number,

876
00:33:40,054 --> 00:33:42,394
which Steven Weinberg wrote a book on, is

877
00:33:42,534 --> 00:33:45,014
first three minutes, but it's more like first

878
00:33:45,014 --> 00:33:48,054
minute. But that's when the decoupling of the

879
00:33:48,054 --> 00:33:50,934
neutrinos occurred. And what that turned out to

880
00:33:50,934 --> 00:33:51,434
allow,

881
00:33:52,069 --> 00:33:53,929
partly because the density is dropping,

882
00:33:54,549 --> 00:33:55,369
is for,

883
00:33:57,429 --> 00:34:00,329
the electrons not to be entirely electron

884
00:34:01,190 --> 00:34:02,410
positron pairs,

885
00:34:03,269 --> 00:34:06,730
but, they were able to undergo nuclear reactions.

886
00:34:07,734 --> 00:34:10,775
And the nuclear reactions only went so far.

887
00:34:10,775 --> 00:34:11,275
They

888
00:34:11,574 --> 00:34:12,795
primarily left

889
00:34:14,855 --> 00:34:15,355
protons,

890
00:34:15,815 --> 00:34:16,315
clearly,

891
00:34:16,614 --> 00:34:17,014
but,

892
00:34:17,414 --> 00:34:19,275
helium particles primarily

893
00:34:19,815 --> 00:34:21,034
as well as the protons

894
00:34:21,659 --> 00:34:22,400
and deuterium

895
00:34:22,780 --> 00:34:23,739
and a few other,

896
00:34:24,380 --> 00:34:25,280
trace particles.

897
00:34:25,739 --> 00:34:27,039
What you couldn't do,

898
00:34:27,579 --> 00:34:29,339
you could have done if the universe had

899
00:34:29,339 --> 00:34:31,339
been different, you could have broken through and

900
00:34:31,339 --> 00:34:33,579
produced all of the elements. But that that

901
00:34:33,579 --> 00:34:34,799
occurred in the stars.

902
00:34:35,135 --> 00:34:37,234
But, anyway, that subject was being,

903
00:34:37,855 --> 00:34:38,835
well probed

904
00:34:39,454 --> 00:34:40,835
and well computed,

905
00:34:41,534 --> 00:34:43,474
and that was, like, one minute after.

906
00:34:44,255 --> 00:34:44,755
But

907
00:34:45,054 --> 00:34:46,835
going back to milliseconds

908
00:34:47,135 --> 00:34:47,954
and earlier,

909
00:34:49,299 --> 00:34:51,940
nobody knew what the degrees of freedom were

910
00:34:51,940 --> 00:34:53,780
in the universe. You said, okay. It's gonna

911
00:34:53,780 --> 00:34:55,639
be mesons and all of that.

912
00:34:56,099 --> 00:34:58,599
And it took a really big theoretical

913
00:34:58,900 --> 00:34:59,400
step

914
00:34:59,780 --> 00:35:01,400
to be able to have the audacity

915
00:35:02,184 --> 00:35:04,364
to think that we could take the constituents

916
00:35:04,424 --> 00:35:06,025
and understand that what they were gonna be

917
00:35:06,025 --> 00:35:09,144
like in these ultra early moments in which

918
00:35:09,144 --> 00:35:11,085
these fluctuations are generated.

919
00:35:11,704 --> 00:35:13,484
And that was a major breakthrough.

920
00:35:14,025 --> 00:35:16,025
In the jargon of the time, it was

921
00:35:16,025 --> 00:35:16,924
called asymptotic

922
00:35:17,319 --> 00:35:18,619
freedom, but what it meant

923
00:35:19,239 --> 00:35:20,059
is that,

924
00:35:20,839 --> 00:35:22,460
instead of having all of the complexity

925
00:35:23,319 --> 00:35:25,500
of mesons like pions, etcetera,

926
00:35:26,440 --> 00:35:29,079
it became simple. It became a simple gas

927
00:35:29,079 --> 00:35:29,819
of quarks,

928
00:35:30,775 --> 00:35:33,094
like simple gas of gluons, which have a

929
00:35:33,094 --> 00:35:34,795
lot of similarity to photons,

930
00:35:35,255 --> 00:35:36,715
except they interact more.

931
00:35:37,175 --> 00:35:37,974
And these,

932
00:35:39,014 --> 00:35:41,494
these species were around, but they were free

933
00:35:41,494 --> 00:35:43,114
of each other more or less.

934
00:35:43,574 --> 00:35:45,034
And that was a remarkable

935
00:35:45,494 --> 00:35:45,994
development,

936
00:35:47,400 --> 00:35:49,719
and it allowed us to take the great

937
00:35:49,719 --> 00:35:50,219
leap

938
00:35:50,839 --> 00:35:53,739
towards the ultra earliest moments of the universe.

939
00:35:54,119 --> 00:35:54,940
And so,

940
00:35:55,800 --> 00:35:57,659
but at some level,

941
00:35:58,199 --> 00:35:59,880
what George and I did, we didn't need

942
00:35:59,880 --> 00:36:01,260
any of that because

943
00:36:01,715 --> 00:36:03,014
we could just propagate

944
00:36:03,875 --> 00:36:06,114
the state from, let's say,

945
00:36:07,715 --> 00:36:09,715
a little bit later than a minute all

946
00:36:09,715 --> 00:36:10,695
the way through

947
00:36:11,074 --> 00:36:11,735
to now,

948
00:36:12,835 --> 00:36:14,534
with the basic constituents

949
00:36:15,150 --> 00:36:17,809
without knowing what happened in the ultra early

950
00:36:18,589 --> 00:36:19,089
moments,

951
00:36:19,549 --> 00:36:22,049
but we always built that in.

952
00:36:22,589 --> 00:36:24,190
The way I used to have to present

953
00:36:24,190 --> 00:36:24,690
it

954
00:36:24,989 --> 00:36:26,829
is that there was at the beginning of

955
00:36:26,829 --> 00:36:29,089
time a Greek dragon that was breathing

956
00:36:29,704 --> 00:36:31,085
breathing a fire.

957
00:36:32,184 --> 00:36:34,364
Our theory is not that more sophisticated

958
00:36:34,744 --> 00:36:35,644
than that now,

959
00:36:35,945 --> 00:36:38,125
but that was the key development

960
00:36:38,425 --> 00:36:40,364
that we were able to relate

961
00:36:41,144 --> 00:36:43,885
what happened now to something that was there

962
00:36:43,945 --> 00:36:46,339
built in from the earliest moments,

963
00:36:46,799 --> 00:36:49,139
but the key thing is that it remained

964
00:36:49,279 --> 00:36:52,079
basically invariant for almost all of the history

965
00:36:52,079 --> 00:36:54,339
of the universe, and then it got modified

966
00:36:54,480 --> 00:36:56,639
as we went through three hundred and eighty

967
00:36:56,639 --> 00:36:57,859
thousand years.

968
00:36:58,364 --> 00:37:00,764
And so it's it's really an amazing story,

969
00:37:00,764 --> 00:37:02,525
and it's the reason we have been able

970
00:37:02,525 --> 00:37:03,505
to now learn

971
00:37:03,965 --> 00:37:06,525
all these precious details about the ultra early

972
00:37:06,525 --> 00:37:07,025
universe

973
00:37:07,485 --> 00:37:09,005
and could even say it without,

974
00:37:11,324 --> 00:37:12,690
you know, with without

975
00:37:13,569 --> 00:37:15,650
nudge, nudge, wink, wake, what a joke it

976
00:37:15,650 --> 00:37:16,150
is.

977
00:37:16,690 --> 00:37:19,170
It's an amazing accomplishment of human beings that

978
00:37:19,170 --> 00:37:21,170
we can even think that we can think

979
00:37:21,170 --> 00:37:22,150
about those eras

980
00:37:22,849 --> 00:37:23,589
with precision.

981
00:37:24,130 --> 00:37:26,835
And so I'd say that's maybe the greatest

982
00:37:26,835 --> 00:37:28,275
thing that came out of all of the

983
00:37:28,275 --> 00:37:28,775
work.

984
00:37:29,315 --> 00:37:32,034
I see. And, I mean, my understanding of

985
00:37:32,034 --> 00:37:34,675
of your of your early work is that,

986
00:37:34,675 --> 00:37:36,835
you know, you you developed the theories and

987
00:37:36,835 --> 00:37:37,494
the models,

988
00:37:38,275 --> 00:37:40,994
to such a point that you you could

989
00:37:40,994 --> 00:37:41,494
tell

990
00:37:42,030 --> 00:37:42,769
the observational

991
00:37:43,309 --> 00:37:45,010
community what to look for

992
00:37:45,710 --> 00:37:46,190
and,

993
00:37:46,510 --> 00:37:47,809
and sort of help them,

994
00:37:48,349 --> 00:37:50,050
I suppose, design their experiments,

995
00:37:50,429 --> 00:37:51,250
design their

996
00:37:51,630 --> 00:37:54,050
observatories. And and lo and behold,

997
00:37:54,844 --> 00:37:56,144
they they saw

998
00:37:57,005 --> 00:37:58,224
essentially what you

999
00:37:58,525 --> 00:37:59,025
predicted.

1000
00:37:59,804 --> 00:38:01,505
I mean, that must have been a very

1001
00:38:02,125 --> 00:38:02,625
satisfying

1002
00:38:03,085 --> 00:38:05,324
experience for you. I mean, I I don't

1003
00:38:05,324 --> 00:38:08,339
think a lot of theorists get that

1004
00:38:08,800 --> 00:38:10,579
in their careers, do they?

1005
00:38:11,280 --> 00:38:12,000
I mean, I think

1006
00:38:12,559 --> 00:38:14,880
did you think that we'd ever observe these

1007
00:38:14,880 --> 00:38:15,380
things,

1008
00:38:15,760 --> 00:38:17,380
that position? But The

1009
00:38:17,839 --> 00:38:18,420
the concept

1010
00:38:18,719 --> 00:38:21,280
concept of, of seeing some of them seem

1011
00:38:21,280 --> 00:38:23,804
to be far fetched, but that's because we

1012
00:38:23,804 --> 00:38:24,304
weren't,

1013
00:38:24,844 --> 00:38:26,844
I would say, ambitious enough. No. I mean,

1014
00:38:26,844 --> 00:38:29,005
the the, you know, technology improved. We didn't

1015
00:38:29,005 --> 00:38:31,244
think the technology could do this. But, you

1016
00:38:31,244 --> 00:38:33,005
know, I mean, I have, you know, I

1017
00:38:33,005 --> 00:38:34,525
mean, back then when we were doing these

1018
00:38:34,525 --> 00:38:35,025
calculations,

1019
00:38:35,670 --> 00:38:36,409
we made

1020
00:38:37,269 --> 00:38:37,769
pictures

1021
00:38:38,469 --> 00:38:39,449
from the calculations

1022
00:38:40,230 --> 00:38:43,449
instead of just summarizing the calculations to statistical,

1023
00:38:45,109 --> 00:38:46,809
quantities that people could measure.

1024
00:38:47,815 --> 00:38:50,695
We generated simulated pictures of what the CMB

1025
00:38:50,695 --> 00:38:51,914
sky would look like.

1026
00:38:52,454 --> 00:38:54,074
And this is nowadays,

1027
00:38:54,534 --> 00:38:57,015
it would be considered trivial. But when I

1028
00:38:57,015 --> 00:38:58,635
first showed these pictures,

1029
00:38:59,175 --> 00:39:01,094
people didn't know what it was. What what

1030
00:39:01,094 --> 00:39:03,275
have we actually done? We've just generated

1031
00:39:03,949 --> 00:39:07,250
random realizations of a two dimensional random field,

1032
00:39:07,630 --> 00:39:09,630
which is, you know, really simple thing to

1033
00:39:09,630 --> 00:39:10,289
do. But,

1034
00:39:10,750 --> 00:39:13,069
initially, the audience members of the audience didn't

1035
00:39:13,069 --> 00:39:14,769
really know what what we were doing.

1036
00:39:15,069 --> 00:39:16,829
But these were these were picked up by

1037
00:39:16,829 --> 00:39:17,329
observers.

1038
00:39:18,589 --> 00:39:19,089
And

1039
00:39:19,864 --> 00:39:22,105
and lo and behold, you know, now we

1040
00:39:22,105 --> 00:39:25,164
we have measurements of actual maps, beautiful maps,

1041
00:39:25,704 --> 00:39:26,444
high resolution

1042
00:39:26,905 --> 00:39:28,605
that show all these blobs.

1043
00:39:28,905 --> 00:39:31,005
And you can test whether,

1044
00:39:31,704 --> 00:39:33,164
the statistical properties,

1045
00:39:34,139 --> 00:39:35,760
of these fluctuations match,

1046
00:39:36,539 --> 00:39:38,799
the expectations of inflationary

1047
00:39:39,099 --> 00:39:39,599
cosmology,

1048
00:39:40,059 --> 00:39:41,599
and it's just remarkable.

1049
00:39:42,699 --> 00:39:44,619
May maybe I could add on to that

1050
00:39:44,619 --> 00:39:47,099
and something I'm very proud of. But, you

1051
00:39:47,099 --> 00:39:48,639
know, George was there fundamentally.

1052
00:39:49,795 --> 00:39:52,675
We, held a meeting not too long after

1053
00:39:52,675 --> 00:39:55,255
I arrived in Toronto from California.

1054
00:39:55,875 --> 00:39:58,355
It was called delta t over t. Delta

1055
00:39:58,355 --> 00:39:59,175
t meaning

1056
00:39:59,554 --> 00:40:01,094
small changes of temperature

1057
00:40:02,039 --> 00:40:04,760
over t is usually the average temperature, but

1058
00:40:04,760 --> 00:40:07,480
here it was over t e a because

1059
00:40:07,480 --> 00:40:08,059
it was

1060
00:40:08,519 --> 00:40:11,079
Canada, Britain joined together, and we all like

1061
00:40:11,079 --> 00:40:11,579
T.

1062
00:40:12,440 --> 00:40:15,239
But the key thing about the expect, about

1063
00:40:15,239 --> 00:40:15,980
the meeting,

1064
00:40:16,405 --> 00:40:17,785
it was the first time

1065
00:40:18,164 --> 00:40:18,805
that the,

1066
00:40:19,285 --> 00:40:20,505
experimental community

1067
00:40:20,805 --> 00:40:22,905
was brought together with the theory community

1068
00:40:23,445 --> 00:40:25,144
as a collective group.

1069
00:40:25,525 --> 00:40:27,445
And that had a big impact on the

1070
00:40:27,445 --> 00:40:27,945
subject

1071
00:40:28,325 --> 00:40:29,945
because at that time,

1072
00:40:30,630 --> 00:40:31,449
the experimentalists

1073
00:40:32,069 --> 00:40:34,250
were all buried in their labs,

1074
00:40:34,789 --> 00:40:37,690
like in MIT or at Berkeley or something,

1075
00:40:37,829 --> 00:40:40,329
and they were all totally into their devices

1076
00:40:40,549 --> 00:40:42,329
because the devices were fascinating.

1077
00:40:43,094 --> 00:40:45,034
But they weren't really tuning

1078
00:40:45,734 --> 00:40:46,635
in to the,

1079
00:40:47,335 --> 00:40:47,835
context,

1080
00:40:48,454 --> 00:40:48,954
cosmological.

1081
00:40:49,815 --> 00:40:52,554
And then, George and I did this work.

1082
00:40:52,695 --> 00:40:53,675
So the epiphany

1083
00:40:54,295 --> 00:40:55,594
I had was to get

1084
00:40:55,969 --> 00:40:56,869
Dave Wilkinson,

1085
00:40:57,650 --> 00:41:00,449
who was the great experimentalist in the microwave

1086
00:41:00,449 --> 00:41:02,630
background at the time after the

1087
00:41:03,089 --> 00:41:05,569
originator of of much of what we were

1088
00:41:05,650 --> 00:41:06,789
have been able to do,

1089
00:41:08,130 --> 00:41:10,710
Dickie who is Princeton, but Wilkinson was great.

1090
00:41:11,525 --> 00:41:12,905
They launched what was called

1091
00:41:15,445 --> 00:41:17,625
the microwave anisotropy probe

1092
00:41:18,005 --> 00:41:18,505
map

1093
00:41:19,045 --> 00:41:20,965
designed to make maps of the universe, and

1094
00:41:20,965 --> 00:41:21,625
this was

1095
00:41:23,780 --> 00:41:24,440
the major

1096
00:41:24,739 --> 00:41:27,239
satellite after the COBE satellite.

1097
00:41:28,099 --> 00:41:28,760
And then,

1098
00:41:29,619 --> 00:41:32,340
sadly, Dave Wilkinson died, but just before he

1099
00:41:32,340 --> 00:41:32,840
died,

1100
00:41:33,619 --> 00:41:35,940
they added Wilkinson in the front. It became

1101
00:41:35,940 --> 00:41:36,679
the WMAP

1102
00:41:37,155 --> 00:41:37,655
telescope.

1103
00:41:38,114 --> 00:41:40,454
In fact, there's a Shaw prize for

1104
00:41:40,755 --> 00:41:41,255
WMAP.

1105
00:41:42,914 --> 00:41:43,315
And,

1106
00:41:44,755 --> 00:41:46,535
and by bringing him,

1107
00:41:47,635 --> 00:41:50,195
he drew in the experimental community. I drew

1108
00:41:50,195 --> 00:41:51,335
in the theory community.

1109
00:41:52,829 --> 00:41:53,329
George

1110
00:41:53,630 --> 00:41:56,289
George's talk there was to unveil

1111
00:41:56,990 --> 00:41:58,050
all of our calculations

1112
00:41:59,230 --> 00:42:01,470
in the primary what we call the primary

1113
00:42:01,470 --> 00:42:02,530
microwave background,

1114
00:42:02,829 --> 00:42:04,530
including where to look,

1115
00:42:05,150 --> 00:42:07,490
you know, that there is this mountain,

1116
00:42:07,864 --> 00:42:10,424
which is called the first acoustic peak, which

1117
00:42:10,424 --> 00:42:13,385
is really where it's easier to make the

1118
00:42:13,385 --> 00:42:13,885
detection.

1119
00:42:14,585 --> 00:42:16,984
It wasn't where the first detection was actually

1120
00:42:16,984 --> 00:42:19,804
made. It was made at larger angular scales

1121
00:42:20,105 --> 00:42:21,405
by the COBE satellite,

1122
00:42:22,400 --> 00:42:22,900
but,

1123
00:42:23,760 --> 00:42:25,700
it it was basically a blueprint.

1124
00:42:26,239 --> 00:42:26,739
And

1125
00:42:27,760 --> 00:42:28,500
there was

1126
00:42:28,960 --> 00:42:30,260
a little bit of skepticism

1127
00:42:30,559 --> 00:42:33,119
that who are these young Turks that seem

1128
00:42:33,119 --> 00:42:33,700
to know

1129
00:42:34,014 --> 00:42:35,795
what the whole subject could do.

1130
00:42:36,094 --> 00:42:38,494
But it was embraced. People took it seriously

1131
00:42:38,494 --> 00:42:40,594
and a lot focused on that region,

1132
00:42:40,894 --> 00:42:42,914
and that's where the second

1133
00:42:43,695 --> 00:42:46,335
detections occurred. And when you brought the two

1134
00:42:46,335 --> 00:42:46,835
together,

1135
00:42:47,135 --> 00:42:49,480
you started to piece that it was the

1136
00:42:49,480 --> 00:42:50,300
full story.

1137
00:42:50,840 --> 00:42:53,559
And every step along the way, there were

1138
00:42:53,559 --> 00:42:56,539
major theoretical results that came out of it.

1139
00:42:56,760 --> 00:42:57,420
In particular,

1140
00:42:58,680 --> 00:43:00,140
that there was this huge

1141
00:43:00,599 --> 00:43:01,099
acoustic

1142
00:43:01,400 --> 00:43:01,900
mountain

1143
00:43:03,234 --> 00:43:03,635
of,

1144
00:43:04,355 --> 00:43:04,855
anisotropy

1145
00:43:05,635 --> 00:43:06,855
that could be detected

1146
00:43:07,315 --> 00:43:08,135
meant that

1147
00:43:09,394 --> 00:43:11,574
the first stars that formed in the universe

1148
00:43:12,034 --> 00:43:14,534
couldn't have formed at redshift or,

1149
00:43:15,050 --> 00:43:16,650
you know, maybe within a million years of

1150
00:43:16,650 --> 00:43:18,190
the big bang. It had to be later

1151
00:43:18,409 --> 00:43:20,090
because otherwise, it would have been all wiped

1152
00:43:20,090 --> 00:43:22,429
out. Well, that was an amazing accomplishment.

1153
00:43:23,449 --> 00:43:25,130
I'd you know, it's like a yes or

1154
00:43:25,130 --> 00:43:25,949
no thing

1155
00:43:26,489 --> 00:43:29,414
that was determined, and that was determined really

1156
00:43:29,414 --> 00:43:31,675
very early, very, very early nineties.

1157
00:43:32,454 --> 00:43:35,494
And so one thing after another, everything locked

1158
00:43:35,494 --> 00:43:36,235
in place.

1159
00:43:36,535 --> 00:43:37,974
It didn't have to be that way. It

1160
00:43:37,974 --> 00:43:39,815
could have been another theory. There were other

1161
00:43:39,815 --> 00:43:41,114
theories floating around.

1162
00:43:41,589 --> 00:43:43,849
But now the theory is unassailable.

1163
00:43:44,150 --> 00:43:45,130
It's called the

1164
00:43:45,589 --> 00:43:47,210
standard model of cosmology.

1165
00:43:47,510 --> 00:43:50,329
It has the dark energy associated with it,

1166
00:43:50,710 --> 00:43:51,929
but our goal

1167
00:43:52,710 --> 00:43:55,530
is beyond the standard model of cosmology.

1168
00:43:55,985 --> 00:43:57,925
We want the newer physics

1169
00:43:58,304 --> 00:43:58,804
that's

1170
00:43:59,105 --> 00:44:01,925
associated with something that's not just

1171
00:44:02,224 --> 00:44:04,005
dark energy, dark matter,

1172
00:44:04,385 --> 00:44:05,925
and then the baryons electrons.

1173
00:44:06,864 --> 00:44:08,644
And it does say the protons,

1174
00:44:09,025 --> 00:44:10,085
neutrons, electrons,

1175
00:44:10,750 --> 00:44:13,090
you know, the usual constituents. We wanna

1176
00:44:13,550 --> 00:44:15,890
see more physics from it. Right.

1177
00:44:16,269 --> 00:44:17,489
Hopefully, with glimpses

1178
00:44:18,030 --> 00:44:18,769
early universe.

1179
00:44:19,070 --> 00:44:21,230
And that's that that's how I wanted to

1180
00:44:21,230 --> 00:44:23,950
to sort of end this discussion on what

1181
00:44:24,110 --> 00:44:25,010
what's next,

1182
00:44:25,950 --> 00:44:26,450
in

1183
00:44:27,125 --> 00:44:27,625
research,

1184
00:44:28,565 --> 00:44:31,144
involving the cosmic microwave background?

1185
00:44:32,164 --> 00:44:34,344
Are there are there new observatories

1186
00:44:34,644 --> 00:44:37,304
that are coming online that you're very excited

1187
00:44:37,364 --> 00:44:38,425
about? Or

1188
00:44:38,940 --> 00:44:41,739
are is the community working on new ways

1189
00:44:41,739 --> 00:44:42,559
to interpret

1190
00:44:43,179 --> 00:44:46,139
data that we have already to maybe get

1191
00:44:46,139 --> 00:44:48,960
a handle on the nature of dark matter

1192
00:44:49,260 --> 00:44:51,099
or dark energy? So what what what are

1193
00:44:51,099 --> 00:44:53,339
you most excited about? Maybe, George, can I

1194
00:44:53,339 --> 00:44:55,264
start with you on that question?

1195
00:44:56,284 --> 00:44:57,105
The great

1196
00:44:57,565 --> 00:45:00,525
thing about the the cosmic microwave background is

1197
00:45:00,525 --> 00:45:01,344
that because

1198
00:45:02,525 --> 00:45:03,025
the

1199
00:45:04,324 --> 00:45:05,664
we're making these measurements

1200
00:45:06,045 --> 00:45:06,864
when the fluctuations

1201
00:45:07,324 --> 00:45:08,385
with small amplitude

1202
00:45:09,565 --> 00:45:11,239
that the theory is simple.

1203
00:45:13,300 --> 00:45:13,800
So,

1204
00:45:14,820 --> 00:45:16,760
so if you can improve the measurements,

1205
00:45:17,860 --> 00:45:18,360
then

1206
00:45:18,739 --> 00:45:19,239
you

1207
00:45:19,780 --> 00:45:21,000
get clean

1208
00:45:21,460 --> 00:45:21,960
interpretation

1209
00:45:22,340 --> 00:45:24,675
of what's going on from the physics because

1210
00:45:24,675 --> 00:45:26,135
there there aren't the complicated

1211
00:45:26,675 --> 00:45:29,715
nonlinear processes when you're dealing with astrophysical objects

1212
00:45:29,715 --> 00:45:32,215
like galaxies or supernovae or whatever.

1213
00:45:33,394 --> 00:45:33,894
So,

1214
00:45:34,994 --> 00:45:36,675
so and there's a lot of information to

1215
00:45:36,675 --> 00:45:39,414
be extracted from the cosmic microwave background.

1216
00:45:39,769 --> 00:45:41,690
Now the the at the moment, I think

1217
00:45:41,690 --> 00:45:43,550
the the premier new facility

1218
00:45:44,409 --> 00:45:46,269
is going to be the Simons Observatory,

1219
00:45:47,210 --> 00:45:48,589
and that will,

1220
00:45:49,690 --> 00:45:51,389
you it's you know, it's just a fantastic

1221
00:45:51,609 --> 00:45:52,909
science case because,

1222
00:45:55,184 --> 00:45:55,684
it'll

1223
00:45:57,824 --> 00:46:00,005
do a wide range of things. But

1224
00:46:00,704 --> 00:46:01,204
primary

1225
00:46:02,224 --> 00:46:03,525
thing that it will do

1226
00:46:03,904 --> 00:46:06,179
is improve the polarization

1227
00:46:06,960 --> 00:46:07,460
measurements

1228
00:46:07,920 --> 00:46:09,119
of the CMB, get,

1229
00:46:09,840 --> 00:46:11,780
more accurate polarization measurements.

1230
00:46:12,079 --> 00:46:13,140
It also has,

1231
00:46:13,599 --> 00:46:14,559
a series of,

1232
00:46:15,199 --> 00:46:18,000
small aperture telescopes that is designed to try

1233
00:46:18,000 --> 00:46:19,140
and go,

1234
00:46:20,655 --> 00:46:23,155
to high sensitivity to search for the signatures

1235
00:46:23,215 --> 00:46:24,515
of gravitational waves

1236
00:46:24,894 --> 00:46:25,394
from,

1237
00:46:25,855 --> 00:46:28,735
an inflationary era. I mean, if if if,

1238
00:46:30,255 --> 00:46:32,195
if a signal like that were were detected

1239
00:46:32,335 --> 00:46:33,635
that you could unambiguously

1240
00:46:33,934 --> 00:46:36,940
say came from the very early universe gravitational

1241
00:46:37,079 --> 00:46:39,319
waves. It'd be the first time that a

1242
00:46:39,319 --> 00:46:42,519
quantum gravitational effect would have been detected, which

1243
00:46:42,679 --> 00:46:44,319
so it's a you know, it would be

1244
00:46:44,319 --> 00:46:45,960
a big deal. See, I would disagree with

1245
00:46:45,960 --> 00:46:46,780
that. Well.

1246
00:46:47,204 --> 00:46:47,684
Because,

1247
00:46:48,005 --> 00:46:50,565
I think that the fluctuations themselves that we

1248
00:46:50,565 --> 00:46:51,065
observe

1249
00:46:52,244 --> 00:46:52,985
are quantum.

1250
00:46:53,364 --> 00:46:56,164
Everything's quantum. Yeah. You could But in particular,

1251
00:46:56,164 --> 00:46:59,305
I'm not exaggerating with that. They're essentially phonons,

1252
00:46:59,364 --> 00:47:01,945
which is what we observe, the impact of

1253
00:47:02,109 --> 00:47:04,130
of phonons from the ultra early universe.

1254
00:47:04,750 --> 00:47:05,889
But just like

1255
00:47:07,070 --> 00:47:07,889
you can have,

1256
00:47:10,750 --> 00:47:14,109
transverse elastic waves as well as longitudinal elastic

1257
00:47:14,109 --> 00:47:15,570
waves, so you can have

1258
00:47:16,215 --> 00:47:18,075
gravity waves as well

1259
00:47:18,614 --> 00:47:19,355
as phonons.

1260
00:47:19,815 --> 00:47:22,535
And they're all occurring at that Yeah. I

1261
00:47:22,535 --> 00:47:24,295
know you agree with that. It's just that

1262
00:47:24,295 --> 00:47:25,035
some skeptics

1263
00:47:25,335 --> 00:47:27,434
might say, well, you know, maybe the fluctuations

1264
00:47:27,655 --> 00:47:30,295
were generated by topological defects or something else,

1265
00:47:30,295 --> 00:47:31,515
you know, whatever.

1266
00:47:31,920 --> 00:47:33,920
But I don't think that's plausible. You see,

1267
00:47:33,920 --> 00:47:36,319
we can still have our lively conversations about

1268
00:47:36,319 --> 00:47:38,579
it. But just to amplify on,

1269
00:47:39,199 --> 00:47:41,920
I'm still well, actually, George too, but I'm

1270
00:47:41,920 --> 00:47:44,099
still engaged with these experiments

1271
00:47:44,800 --> 00:47:45,699
in my dotage.

1272
00:47:46,184 --> 00:47:48,684
So I'm a member of the Simons Observatory,

1273
00:47:48,905 --> 00:47:51,724
but that was a basically, a direct outgrowth

1274
00:47:52,425 --> 00:47:54,364
with a huge amount of money from,

1275
00:47:54,905 --> 00:47:56,285
the great Jim Simons,

1276
00:47:57,704 --> 00:48:00,605
of the Atacama Cosmology Telescope, which George

1277
00:48:01,230 --> 00:48:02,289
alluded to already.

1278
00:48:02,989 --> 00:48:05,329
So, you know, Planck is unbelievable.

1279
00:48:06,110 --> 00:48:07,489
And then what just

1280
00:48:08,110 --> 00:48:08,849
was released

1281
00:48:09,789 --> 00:48:10,269
was,

1282
00:48:10,829 --> 00:48:13,489
information from the Atacama Cosmology Telescope.

1283
00:48:14,344 --> 00:48:15,804
That mission is over.

1284
00:48:16,264 --> 00:48:18,184
It was really high up in the Andes

1285
00:48:18,184 --> 00:48:19,324
because you're trying to get

1286
00:48:19,625 --> 00:48:21,644
above as much,

1287
00:48:22,664 --> 00:48:24,525
as much water vapor as you can.

1288
00:48:25,385 --> 00:48:28,679
And it just has given exquisite results, and

1289
00:48:28,679 --> 00:48:31,239
Simons Observatory is gonna be so much better

1290
00:48:31,239 --> 00:48:33,800
than that. And it's going to have legs

1291
00:48:33,800 --> 00:48:34,780
into around

1292
00:48:35,319 --> 00:48:36,280
2035

1293
00:48:36,280 --> 00:48:37,579
to 2037.

1294
00:48:38,119 --> 00:48:41,000
Then there may be other experiments that'll be

1295
00:48:41,000 --> 00:48:43,500
taking over, one in space called Lightbird,

1296
00:48:44,295 --> 00:48:44,795
another,

1297
00:48:46,295 --> 00:48:47,755
on the ground that has

1298
00:48:48,454 --> 00:48:51,094
big support from the Department of Energy in

1299
00:48:51,094 --> 00:48:52,074
The United States.

1300
00:48:52,454 --> 00:48:52,934
It's called,

1301
00:48:54,375 --> 00:48:57,929
CMB stage four, and I'm part of that,

1302
00:48:57,929 --> 00:48:59,789
but it's kind of beyond my

1303
00:49:00,090 --> 00:49:01,469
working time horizon

1304
00:49:01,849 --> 00:49:04,829
because it's probably 2036

1305
00:49:05,210 --> 00:49:07,630
before it really starts We're getting old.

1306
00:49:10,824 --> 00:49:13,065
Well, for every young George and even for

1307
00:49:13,065 --> 00:49:15,304
you, for every young, you will learn that

1308
00:49:15,304 --> 00:49:17,485
that's the mantra to sing to the world,

1309
00:49:18,184 --> 00:49:20,364
because it's an extremely exciting period.

1310
00:49:20,985 --> 00:49:21,485
But

1311
00:49:21,785 --> 00:49:23,804
what I think is as fundamental

1312
00:49:24,905 --> 00:49:25,304
as,

1313
00:49:26,699 --> 00:49:27,440
the experimental

1314
00:49:27,739 --> 00:49:30,960
advances and, you know, cleaning up the story

1315
00:49:31,900 --> 00:49:35,019
is that the theorists keep working away on

1316
00:49:35,019 --> 00:49:36,079
trying to find

1317
00:49:36,699 --> 00:49:37,599
new signatures

1318
00:49:37,900 --> 00:49:39,440
to look for in the data

1319
00:49:39,835 --> 00:49:43,035
that will deliver new information to us to

1320
00:49:43,035 --> 00:49:45,054
shape the physical theories of cosmology.

1321
00:49:45,755 --> 00:49:48,635
And so that's this beyond the standard model

1322
00:49:48,635 --> 00:49:49,375
of cosmology

1323
00:49:49,675 --> 00:49:52,074
thing that I referred to. And it's a,

1324
00:49:52,074 --> 00:49:53,535
you know, a goal which,

1325
00:49:54,339 --> 00:49:57,219
should be informing the theory side as well

1326
00:49:57,219 --> 00:50:01,239
as the tremendous experimental advances, which are absolutely

1327
00:50:01,460 --> 00:50:01,960
astounding,

1328
00:50:02,900 --> 00:50:04,440
that we are seeing happening.

1329
00:50:05,139 --> 00:50:06,839
And then it's all completely

1330
00:50:07,139 --> 00:50:07,639
connected

1331
00:50:08,420 --> 00:50:08,920
to

1332
00:50:10,494 --> 00:50:12,494
the thing that we haven't talked about, which

1333
00:50:12,494 --> 00:50:14,574
is the cosmic web and the large scale

1334
00:50:14,574 --> 00:50:16,574
structure and all of that, of which there

1335
00:50:16,574 --> 00:50:18,275
are huge, huge experiments.

1336
00:50:18,815 --> 00:50:21,534
We've always gotten a huge amount of data

1337
00:50:21,534 --> 00:50:22,275
from that,

1338
00:50:22,619 --> 00:50:23,359
but we're

1339
00:50:23,659 --> 00:50:25,119
you know, it's like a discontinuous

1340
00:50:25,420 --> 00:50:27,259
step upward in terms of the amount of

1341
00:50:27,259 --> 00:50:27,759
data

1342
00:50:28,059 --> 00:50:29,359
coming in. And so

1343
00:50:29,739 --> 00:50:31,440
we're getting these exquisite

1344
00:50:31,900 --> 00:50:32,400
mappings

1345
00:50:32,779 --> 00:50:33,279
of

1346
00:50:33,659 --> 00:50:36,045
the universe and all of its epics, and

1347
00:50:36,045 --> 00:50:37,505
putting them all together

1348
00:50:38,125 --> 00:50:39,585
will make this incredibly

1349
00:50:40,364 --> 00:50:40,864
precise,

1350
00:50:41,244 --> 00:50:44,684
we think, cosmic story of evolution from the

1351
00:50:44,684 --> 00:50:47,324
ultra early moments right to now. I mean,

1352
00:50:47,324 --> 00:50:49,744
the the here and now. Development of

1353
00:50:50,045 --> 00:50:50,545
the

1354
00:50:52,599 --> 00:50:55,320
Lambda CDM model that that that, you know,

1355
00:50:55,320 --> 00:50:56,539
fits the data beautifully.

1356
00:51:00,280 --> 00:51:02,219
You know, it's a big success story.

1357
00:51:02,519 --> 00:51:03,019
However,

1358
00:51:04,804 --> 00:51:07,224
if we actually analyze the key ingredients,

1359
00:51:07,605 --> 00:51:10,085
an inflationary year at very early times, we

1360
00:51:10,085 --> 00:51:12,105
don't understand the physics behind that.

1361
00:51:12,644 --> 00:51:15,605
The the cold, dark matter that's necessary to

1362
00:51:15,605 --> 00:51:17,570
make the model work, We don't know what

1363
00:51:17,570 --> 00:51:18,309
it is.

1364
00:51:19,010 --> 00:51:19,510
And

1365
00:51:19,890 --> 00:51:22,530
the dark energy, we haven't a clue. And

1366
00:51:22,530 --> 00:51:24,289
and, I mean, you know, dark energy is

1367
00:51:24,289 --> 00:51:26,690
just deeply mysterious from the theoretical point of

1368
00:51:26,690 --> 00:51:29,489
view. So the key ingredients, we don't really

1369
00:51:29,489 --> 00:51:29,989
understand

1370
00:51:31,405 --> 00:51:33,425
from the point of view of fundamental physics.

1371
00:51:34,204 --> 00:51:34,704
So,

1372
00:51:35,325 --> 00:51:37,265
you know, the hope is

1373
00:51:38,045 --> 00:51:40,704
that if we make more detailed observations

1374
00:51:41,325 --> 00:51:43,485
that the model will break, and it will

1375
00:51:43,485 --> 00:51:44,704
break in some way

1376
00:51:45,805 --> 00:51:47,025
that tells us

1377
00:51:47,460 --> 00:51:48,760
something about the physics

1378
00:51:49,139 --> 00:51:49,639
of,

1379
00:51:50,179 --> 00:51:51,480
of these, components.

1380
00:51:52,500 --> 00:51:54,599
So to give you an ex an example,

1381
00:51:55,059 --> 00:51:55,960
the the,

1382
00:51:56,900 --> 00:51:57,639
in inflation,

1383
00:51:59,539 --> 00:52:00,039
the

1384
00:52:00,579 --> 00:52:01,079
interactions

1385
00:52:02,094 --> 00:52:04,994
between fields involved in inflation can introduce

1386
00:52:05,695 --> 00:52:06,195
statistical

1387
00:52:06,574 --> 00:52:07,074
correlations

1388
00:52:08,175 --> 00:52:10,735
that can in principle be detected. They haven't

1389
00:52:10,735 --> 00:52:13,055
been detected yet. But then that would tell

1390
00:52:13,055 --> 00:52:14,755
us, you know,

1391
00:52:15,695 --> 00:52:16,994
a lot about the nature

1392
00:52:18,030 --> 00:52:21,070
of, the fields that were responsible for an

1393
00:52:21,070 --> 00:52:21,570
inflationary

1394
00:52:21,869 --> 00:52:22,369
epoch.

1395
00:52:23,309 --> 00:52:23,809
So

1396
00:52:24,269 --> 00:52:24,769
so,

1397
00:52:25,070 --> 00:52:25,969
you know, the

1398
00:52:26,269 --> 00:52:28,030
the hope is that the model would break,

1399
00:52:28,030 --> 00:52:29,890
but nobody can tell you

1400
00:52:31,005 --> 00:52:33,244
how it might break, you know, what to

1401
00:52:33,244 --> 00:52:34,764
what to look for. We just have to

1402
00:52:34,764 --> 00:52:35,664
keep trying

1403
00:52:36,204 --> 00:52:38,525
and hope that nature is kind to us,

1404
00:52:38,525 --> 00:52:39,744
and we see something

1405
00:52:40,525 --> 00:52:41,585
radically new.

1406
00:52:42,364 --> 00:52:44,045
So it sounds like there might be another

1407
00:52:44,045 --> 00:52:45,929
sharp rise in the future

1408
00:52:46,789 --> 00:52:49,050
related to the cosmic microwave background.

1409
00:52:49,510 --> 00:52:51,590
Well, that's great. Thanks thanks to both of

1410
00:52:51,590 --> 00:52:54,390
you. I'm afraid that's that's all the time

1411
00:52:54,390 --> 00:52:57,110
we've got for this discussion. Thanks for such

1412
00:52:57,110 --> 00:52:59,464
a fascinating discussion, and

1413
00:52:59,764 --> 00:53:00,264
congratulations,

1414
00:53:01,284 --> 00:53:03,464
for winning the 2025

1415
00:53:03,764 --> 00:53:05,144
Shaw prize in astronomy.

1416
00:53:06,244 --> 00:53:07,065
Thank you.

1417
00:53:08,565 --> 00:53:10,644
Okay. Thank you. And, George, see you in

1418
00:53:10,644 --> 00:53:11,464
Hong Kong.

1419
00:53:12,324 --> 00:53:12,719
Yeah.

1420
00:53:19,760 --> 00:53:22,659
This episode is sponsored by the Shaw Prize

1421
00:53:22,719 --> 00:53:23,219
Foundation.

1422
00:53:24,079 --> 00:53:26,260
The Shaw Prize honors individuals

1423
00:53:26,800 --> 00:53:28,065
regardless of race,

1424
00:53:28,625 --> 00:53:29,125
nationality,

1425
00:53:29,744 --> 00:53:30,244
gender,

1426
00:53:30,625 --> 00:53:32,005
and religious belief,

1427
00:53:32,464 --> 00:53:33,444
who are currently

1428
00:53:33,744 --> 00:53:35,204
active in their respective

1429
00:53:35,505 --> 00:53:38,085
fields and who have recently achieved

1430
00:53:38,625 --> 00:53:40,164
distinguished and significant

1431
00:53:40,625 --> 00:53:41,125
advances,

1432
00:53:41,859 --> 00:53:42,679
who have made

1433
00:53:42,980 --> 00:53:43,480
outstanding

1434
00:53:44,019 --> 00:53:44,519
contributions

1435
00:53:44,900 --> 00:53:45,719
in academic

1436
00:53:46,339 --> 00:53:47,000
and scientific

1437
00:53:47,780 --> 00:53:49,320
research or applications,

1438
00:53:50,179 --> 00:53:51,960
or who in other domains

1439
00:53:52,339 --> 00:53:53,719
have achieved excellence.

1440
00:53:54,565 --> 00:53:56,505
The Shaw prize is dedicated

1441
00:53:56,965 --> 00:53:57,784
to furthering

1442
00:53:58,085 --> 00:53:58,585
societal

1443
00:53:58,885 --> 00:53:59,385
progress,

1444
00:54:00,085 --> 00:54:00,585
enhancing

1445
00:54:00,965 --> 00:54:03,784
quality of life, and enriching humanity's

1446
00:54:04,405 --> 00:54:04,905
spiritual

1447
00:54:05,765 --> 00:54:06,265
civilization.

1448
00:54:07,579 --> 00:54:09,500
I'm afraid that's all the time we have

1449
00:54:09,500 --> 00:54:10,719
for this week's podcast.

1450
00:54:11,099 --> 00:54:14,559
Thanks to Richard Bond and George F. Stathieu

1451
00:54:14,860 --> 00:54:17,659
for joining me today. And a special thanks

1452
00:54:17,659 --> 00:54:19,679
to our producer, Fred Ailes.

1453
00:54:20,059 --> 00:54:22,000
We'll be back again next week.