Create an account
Big Bang Theory
The theory that the universe began to expand after an explosion of concentrated matter and energy.
Cosmic microwave background (CMB) radiation
Radiation left over from the big bang, detected in the microwave portion of the spectrum with a temperature of only 2.7 K.
A model of the universe in which a stationary Earth is at the center and all other celestial bodies revolve around it.
A model of the universe in which a stationary Sun is at the center and the planets revolve around it.
Hertzsprung-Russell (H-R) diagram
A plot of stars according to their luminosity and surface temperature.
The observed relationship that the velocity of recession of a galaxy is proportional to its distance.
A model that explains the formation of the solar system from a large cloud of gas and dust floating in space 4.56 billion years ago.
A chain of nuclear reactions in which hydrogen nuclei (or protons) fuse together to form helium nuclei, releasing energy.
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together