Space

The Big Shablam and background radiation
According to The Big Bang Theory (not the TV-sitcom), the universe was created out of nothing after a, drum roll... big bang, that happened 13.7 billion years ago. Electromagnetic radiation from this event is called background radiation. It was visable light before, but got longer wave-length due to the universe expanding and is now in the microwave-area on the spectrum. We can measure the variation in this radiation that gives us information about the universe's age, composition and expansion speed.

Stars
Stars send out differents amounts of wave-lenghts, and this affects their color based on thir surface temperature. A star with a hotter temperature on the surface, sends out short-waved radiation, making the star appear more blue. Stars who send out long-waved radiation, are cooler on the surface and appear more red.

Other info about space:
Doppler effect

What can we measure in space?