And cosmic microwave background is not perfectly uniform.

And this is our motion, relative to the cosmic microwave background.

It also predicts exactly the right kind of cosmic microwave background fluctuations, as they are observed on microwave background sky.

So next time we will talk about cosmology Cosmic microwave background fluctuations.

At the very large scales, it is normalized by using the cosmic microwave background.

We now turn to the use of the cosmic microwave background as a cosmological tool.

The existence of the cosmic microwave background is one of the two great predictions of the Big Bang cosmology.

Neither the prediction of the cosmic microwave background sky, nor formation of galaxies essentially today are is what's observed.

This test got revived through the cosmic microwave background. And it's probably now the most important of all of our tools.

And those fluctuations were stretched to astronomical sizes, and those fluctuations eventually are the things we see in the cosmic microwave background.

The expectation then is that cosmic microwave background will have large scale fluctuations with fairly high amplitudes maybe 10 to the 3.

This is the WMAP microwave background that we see.

We know largely from the precision measurements of the cosmic microwave background that universe is very close to flat, if not absolutely flat.

The first one was studies of a cosmic microwave background with exquisite precision, both from round, from balloon, burning instruments, and from space.

This is the noise that Penzias and Wilson heard the oldest sound that you're ever going to hear, the cosmic microwave background radiation

So here is the problem in the nutshell. We see the density fluctuations in the early universe imprinted on the cosmic microwave background photosphere.

These predictions are in excellent agreement with observations by the WMAP satellite of the cosmic microwave background, which is an imprint of the very early universe.

The best evidence for dark matter today comes from measurements of something called the cosmic microwave background, the afterglow of the Big Bang, but that's another story.

This shows the actual Baryonic Acoustic Oscillation as they would appear, and those will map into the peaks of the Doppler peaks in the cosmic microwave background.

The cosmic micro background remains as one of the touchstones of cosmology.

It was big enough to be transparent to light, and that's what we see in the cosmic microwave background that George Smoot described as looking at the face of God.

If you were to take an image of the cosmic microwave background, it will be pretty uniform and so you have to turn the contrast now by factor of 1000.

A completely different approach based on different measurements in different physics, is from constellations in the early universe from cosmic microwave background, and that produces result which is in perfectly good agreement.

It also happens to be exactly what we observe in the cosmic micro background.

Those are of course responsible for the Doppler peaks in the power spectrum of the microwave background.

Cosmic Strings

Cosmic Egg.

(Laughter) (Microwave beeps) (Laughter)

And then, you see that there is a dipole, due to the motion of the Milky Way relative to microwave background.

So, it turns out that actually all star light, ever made by all stars through history of universe so far is just a few percent of the energy density of a cosmic microwave background which has a very subtle effect in of itself.

Baryons from nuclear synthesis. And that is a fairly reliable measurement and from micro background and from cosmic nucleus synthesis.

A good physical mechanism for this to happen is inverse Compton cooling of hot gas on cosmic micro background photons.

So when, microwave background is released, the decoupling stops, and, whatever pattern of fluctuation was there will remain frozen and observable today.

Now, this was cosmic.

It was cosmic radiation

How long should I microwave this?

So the observed thing is, fluctuations in microwave background, since radiation and baryons are coupled before the recombination, which are parts in a million.

We've shown that it can fit all of the data that we have about the formation of galaxies, the fluctuations in the microwave background.

Suppose you're the cosmic designer.

Or because of cosmic radiation?

Please put this in the microwave oven.

Please put this into the microwave oven.

So a microwave is a similar system.

So in other words If the galaxy was at rest compared to, say, microwave background in comoving coordinates, it will have peculiar velocity of 0.

Background