Atoms Definition and 852 Threads

A laser is a device that uses light flashes to excite the atoms so you get electrons with energy levels about 2 or 3 levels above the ground state. They emit photons, which vibrate at a particular frequency, they get reflected off the half silvered mirror, to excite electrons and make them emit...

Or is it Nebulae...anyways What is the density in atoms per unit volume of most nebulas? I am just looking for a rough estimate to help me picture it.. And what would it look like if u were inside one..would u even see anything?