Incoming links: Big Bang
There is a slight variation in temperature of CMB across the sky of the order of 200 microKelvin. It is small to the ~2.7 K average temperature, but it can be measured.
If the initial conditions of the Big Bang and the laws of physics were perfectly symmetric, then we could expect the universe to just be one perfectly uniform boring soup.
But instead some asymetry made all the fun weird things we see today happen eventually, like galaxies and life.
And the cosmic microwave background serves as a way for us to look back in time to the early conditions of the universe, as it was set in stone as soon as the universe became transparent to this light during recombination.
Or if you want to get poetic, it is the closest we can ever get to listening to the original word of God when he setup the initial conditions of the universe.
The ansiotropies of CMB is the ultimate astronomical compass we will ever have, as it is the thing with the least proper motion.
Radio astronomy is cool because it revealed:The 1974 Nobel Prize in Physics was awarded for pioneering radio astronomy from the late 40s onwards done at the University of Cambridge which was an epicenter of early research in that area, leading to the creation of the Mullard Radio Astronomy Observatory in 1958.
- some very interesting new types of astronomical objects that were not as noticeable in the visible spectrum notably:
- quasars: quasars are extremely redshifted, which means by Hubble's law that they are very far from Earth, so the fact that we could see them at all meant they must have produced immense amounts of light
- pulsars: scientists thought they had found extraterrestrial life when they saw these regularly pulsating signal sources!
- cosmic microwave background which is a major evidence for the Big Bang
- radio wavelengths penetrate Earth's atmosphere better than the visible spectrum making it easier to make ground-based observations