What kind of radiation did the universe start as shortly after the Big Bang?

How did the radiation from the Big Bang change to the radio waves that were picked up by Penzias and Wilson?

What do scientists believe is causing the universe to expand faster than it has before?

What happens to the electromagnetic radiation we see from a celestial object as it moves away from us?

What does the "dark" in terms like "dark energy" and "dark matter" mean?

What does it mean that the empty space between celestial objects measures 3K?

Hubble's Law states that the farther away a galaxy is, the __________ it moves away.

Changing the concentration of a gas through which light is passing will affect its emission spectrum.

Changing the type of gas (i.e. hydrogen vs helium) affects the way the absorption spectrum looks.

Kirchhoff's 3rd Law states that a _____________ spectrum viewed through a thin gas produces a(n) _______________ spectrum.