Quasars are known to vary in brightness by just a few hours or days. What can we say about the size of these quasars? Observations from the Compton Gamma Ray Observatory indicate that the gamma-ray...

Quasars are known to vary in brightness by just a few hours or days. What can we say about the size of these quasars?

Observations from the Compton Gamma Ray Observatory indicate that the gamma-ray bursts have an even distribution throughout the sky. How can we be sure that these bright phenomena are not coming from our own galaxy, the Milky Way?

Sometimes dark matter is called “cold dark matter.” Why do you think this is done?