Date: December 3, 2009
Title: When the Universe Was Young
Podcaster: Richard Drumm
Organization: Drumm Digital Design
Description: Richard Drumm talks with Dr. Mark Whittle of the University of Virginia Astronomy Department about the formation of the first stars and galaxies and the surprising implications of the WMAP mission’s image of the entire universe, the largest image ever taken.
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by 3D, Drumm Digital Design of Charlottesville, Virginia. 3D is a full service production company that has astronomy as its passion. Visithttp://theastronomybum.blogspot.com/if you want to contact Richard Drumm of 3D.
- When the Universe Was Young -
For the 365 Days of Astronomy Podcast series.
And thank you again, to George Hrab for that wonderful musical introduction. If you don’t listen to the Geologic Podcast yet, why you should! Hello, I’m Richard Drumm, President of the Charlottesville Astronomical Society, here in Charlottesville, Virginia with Professor Mark Whittle of the University of Virginia Astronomy Department. Hello Doctor Whittle!
Tell me, you’d mentioned there was a roughness in the universe. Where did this roughness come from, was it, was the universe born rough? Or how’d this roughness come to be?
Yeah, well it turns out actually that if the universe if born completely smooth, and if the universe contains only matter and radiation, then there’s no way to generate roughness out of smoothness. The smooth expansion just remains smooth. And we’d end up in a universe today which was just very cold, dilute gas and photons. There’d be no stars and galaxies. So…
No fun at all!
Yeah, very sterile universe. The origin of the roughness, this mottle of slightly denser and less dense regions that we actually witness on the microwave background, the construction of the original roughness that grew into that, that grew into the sound waves, has been a puzzle for a long time. And it’s now thought that there’s a good solution to that puzzle, and the solution is really quite remarkable.
There needs to be two ingredients to make that roughness. The first of which is there’s an inherent roughness in all of physical reality due to its quantum nature. Physical reality is a quantum world, if you like. Everything, although we’d never notice it, everything down at the sub-atomic level is a constant fluctuation, that’s what one means in this context by quantum. There’s a constant hiss in fact, a sort of a background fluctuation of everything, the energy of everything is fluctuating in a very, very slight way.
So these quantum fluctuations which are very, very tiny, even if they were occurring sort of at the moment of creation, if the expansion was determined or driven by the presence of only radiation or matter, then the fluctuations are too tiny to grow into what’s needed to make stars and galaxies. What we need is a mechanism to stretch the quantum fluctuations.
Well it turns out that in the hands of a rapidly accelerating expansion, quantum fluctuations can actually be stretched and made real, and I’ll explain that in a minute, so that they will ultimately, they do provide the roughness to make stars and galaxies. This was recognized very early on after the introduction of the theory of inflation in 1980. This theory was actually introduced for actually rather different reasons. It was recognized as being a remarkable way to solve a couple of rather profound problems with the standard big bang theory.
And it solved those beautifully, but it also solved the roughness problem; the origin of roughness. And so the idea is, that early in the universe’s history, and by early here I mean definitely before a nanosecond and I say that because there are properties of the current universe that we know come from properties around a microsecond, millisecond/microsecond time. So we know that the universe was predominantly made of radiation and particles around a microsecond or so.
But the theory of inflation raised the possibility that at an earlier time, earlier in the expansion, the primary stuff of the universe was different. In fact, it was in some ways rather similar to that substance that we talked about earlier, the dark energy. In other words, there was a condition in which the space itself had energy, but this time that energy density was very high. Much, much higher than the current energy in dark energy.
So remember that when space weighs something it tends to fall outwards, and make more of itself. And the speed with which it does that depends on the density of the material. It’s easy to sort of intuit that, dense things will collapse quickly, and dense vacuums will expand quickly, fall outwards fast. And so the idea is that perhaps at a very high temperature the nature of space acquires this energy density and it falls outwards and it does so exceedingly rapidly, and it does so exponentially fast so it doubles and doubles and doubles and doubles its size and its speed. And making more of itself.
And this is inflation.
This is inflation, this is the theory of inflation. So it’s a theory for the launch of the big bang, the seed of dense vacuum falls outwards making an expansion that just perfectly launches the entire universe. It makes actually as much matter as you would like, and it launches it in exactly the right way to generate the expanding universe. And, and this is relevant to our current theme, the quantum fluctuations inherent in that space seed the roughness, and they do it in a remarkable way. Normally, quantum fluctuations sort of go up & down and up & down and they average to zero. And this is what would happen if the universe wasn’t in fact accelerating in its expansion. At that time parts of the universe would rather quickly separate from each other faster than the speed of light.
And so, so surrounding every point in space there is a region called an event horizon beyond which the material is now moving faster than light. And so as these quantum fluctuations go up & down and up & down, as they cross the event horizon, they’re disconnected from their prior material and so they no longer go back down, they no longer know what their initial fluctuation came from, they’re severed.
Don’t know what their baseline is, yes.
That’s right. And so what are quantum fluctuation they become real fluctuations, there’s this transformation as the expand…
From virtual to real.
From virtual or, yeah from virtual or quantum, those two words in this context are the same, are transformed into real fluctuations as every region expands past its event horizon. There’s another word for this actually, it’s Hubble sphere as well. It’s where the expansion speed is crossing light speed. And the nature of these fluctuations, they just keep on growing, but as they grow, more are constructed inside and then more are constructed inside those and those and those, so it’s a nested sequence; every scale has fluctuations on it and as the expansion continues the universe is driven into this flat geometry, so the space has a Euclidian geometry and it’s peppered with tiny fluctuations.
And then a crucial thing happens, because that is not the universe we’re currently in. This expanding vacuum needed to transform into radiation and matter. And when it did so, all of these fluctuations that were higher and lower energy densities of the vacuum become higher and lower densities in the radiation and in the matter.
And so we’ve now launched this expanding universe sprinkled with denser and less dense regions and as that expansion continues the density contrast, the difference between the dense and less dense region, that contrast grows. And it actually grows for a couple of different reasons. Mainly they’re to do with the fact that gravity is amplifying them so denser regions don’t expand as fast as less dense regions, and so they get denser, and so it goes and so it goes.
So that by 400,000 years those fluctuations have now become the ripples and patchiness that we see in the microwave background…
And they’re writ large as it were.
Writ large, and then by 200 million years they’ve now transformed into the first generation of stars and by the first billion years we now have the galaxies and here we are 14 billion years later with this mottled web-like pattern of galaxies and structure throughout the universe. So the remarkable fact is that the tapestry of galaxies is an amplified image of quantum fluctuations during inflation. And so too are these patches on the microwave background. That oval, all-sky WMAP image is really a frozen picture of this quantum patchiness during inflation. And depending on when inflation occurred, and most cosmologists think it probably occurred around 10 to the minus 36 seconds after the big bang. Or in a sense it was the big bang but it occurred at that time.
If you trace that entire region of the universe, which is many billions of light years across, back, then just after inflation it was the size of a bacterium. The microwave background is this extraordinary photograph of a bacterium-sized region of the universe just after inflation. And then if you track that back to the origin of the patchiness itself, to those very quantum fluctuations, those were occurring on sub-sub proton-sized scales.
So the microwave background breaks so many records if you like. It’s the earliest image we have of anything in the universe. It’s contains patches on it which will become the largest structures in the universe that we can see. It also photographs directly the structure of the universe less than a nanosecond after it was born. And those patches when they were made were smaller by far than anything we’ve ever seen with any microscope here on Earth.
So the microwave background is this, it’s a microscope, it’s a telescope, and it’s a time machine, all rolled into one, and stored in it is enough information to kind of diagnose what the character of the universe is today, what its future will be and what its birth was. It’s an extraordinary document, so you know when you look at that microwave background image, either the WMAP image or similar images, it’s nice to sort of view it as a primordial script or document. It’s written by nature in nature’s own language.
Ah. Well my mind is certainly blown, and thank you Dr. Whittle for making this all crystal clear!
You’re very welcome, Richard, that was… Thank you for interviewing me.
End of podcast:
365 Days of Astronomy
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