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"Ok, I'm Ned Wright, and I'm a professor of physics and astronomy at UCLA, and I work
on infrared astronomy and cosmology."
How useful is the cosmic microwave background radiation?
"Well, the most important information we get is from the cosmic microwave background radiation
at the lowest level is it's existence. When I started in astronomy, it wasn't 100 percent
certain that the Big *** model was correct. And so with the prediction of a cosmic microwave
background from the Big *** and the prediction of no cosmic microwave background from the
competing theory, the steady state, that was a very important step in our knowledge."
"And then the second reason that the cosmic microwave background is very important, is
that it's spectrum is extremely similar to a black body. And so, by being a black body
means that universe relatively smoothly transitioned from being opaque to being transparent, and
then we actually see effectively an isothermal cavity when we look out, so it looks very
close to a black body."
"And the fact that we are moving through the universe can be measured very precisely by
looking at what is called the dipole anisotropy of the microwave background. So one side of
the sky is slightly hotter (about 3 millikelvin hotter) and one side of the sky - the opposite
side of the sky - is slightly colder (about 3 millikelvin colder), so that means that
we are moving at approximately a tenth of a percent of the speed of light. And in fact
we now know very precisely what that value is - it's about 370 kilometers per second.
So that's our motion, the solar system's motion through the universe."
"An then the final piece of information we're getting from the microwave background now,
in fact the Planck satellite just gave us more information along these lines is measurement
of the statistical pattern of the very small what I call anisotropies or little bumps and
valleys in the temperature. So in addition to the 3 millikelvin difference, we also have
plus or minus 100 microkelvin difference in the temperature from different spots. And
so, when you look at these spots, and look at their detailed pattern, you can actually
see a very prominent feature, which is there's about a one and a half degree preferred scale,
and that's what's caused by the acoustic waves that are set up by the density perturbations
early in the history of the universe, and how far they could travel before the universe
became transparent. And that's a very strong indicator about the universe."
What does it tell us about dark energy?
"The cosmic microwave background actually has this pattern on a half degree scale, and
that gives you effectively a line of position, as you have with celestial navigation where
you get a measurement of one star with a sextant, then you get a line on the map where you are.
But you can look at the same patter - the acoustic wave setup in the universe, and you
see that in the galaxy's distribution a lot more locally. We're talking about galaxies,
so it might be a billion light years away, but to cosmologists, that's local. And these
galaxies also show the same wave-like pattern, and you can measure that angle at scale locally
and compare it with what you see in history and that gives you the crossing line of position.
And that really tells us where we are in the universe, and how much stuff there is and
it tells us that we have this dark energy which nobody really understands what it is,
but we know what it's doing. It's making the universe accelerate in it's expansion."