alkalin's got it right,<br /><br />and you've asked some classic questions. Light does behave like a wave, the fact that it refracts into a rainbow, and can create interference patterns is proof of that. And because all other waves require a medium, physicists believe light had a medium it traveled in as well, the aether (or ether). All attempts to find this aether have failed and attempts to show that some required properties/observations don't exist...have succeeded. So aether doesn't/didn't work out.<br /><br />Magnetic and electric fields can exist in a vacuum, without any medium. Light is these two fields messing with eachother, and those alterations propagating out from the source.<br /><br />One way to think of it, is the universe has electrical and magnetic fields everywhere already. Imagine them as untouched, so completely calm. Then, an electron moves, causing a disturbance. This disturbance, this change, takes time to communicate itself to the field everywhere else, and you get a ripple, like in a pond. A water wave is made of water, and EM wave is made of EM fields. In that sense, it is a wave, in a medium.<br /><br />The complication arises with the observed fact that you can isolate small "packets" of light (photons)...and thus rises the concept of a self-propagating wave (with no medium).<br /><br />Each photon has a size about equal to it's observed classical wavelength IIRC. So each color has at least a single seperate photon. The more photons of that color/energy, the brighter the observed light of that color. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>