wickedwind-deactivated20111103 asked: 2 questions: I recall being taught that some physicists theorize that there is only one photon of light. This is probably a lie, because my physics teacher was crap, but I keep thinking about it. Is there any relevance to it? And also, if the earth (this will never happen but just for the purposes of the question) were suddenly free of the influences of gravity of the sun and whatever is keeping it in orbit, how long from the moment of no gravity would it take for the earth to "slingshot" away from its orbit? I guess what I'm asking is how fast is gravity? That's probably a bad question because I'm not sure if gravity is a force or a thing per se, but I was wondering. Anyways I don't know anything about physics or whatever but I find it fascinating and you seem to be very good at explaining things to people like me. tldr sorry
1. A photon is a particle of light. But wait, if there is a “particle of light,” how can light have a wavelength? Aha! Here we have it. Light behaves as a particle and a wave. The “colour” of a photon depends on its wavelength/frequency/energy. There are highly technical ways to change the frequency of a photon and thereby change the colour, but it’s usually only done in laboratories—though it does happen in nature. Far away galaxies are said to be “redshifted” when they are moving away from us very quickly because they are moving so fast that the wavelength of the light that they emit is stretched out and their colours appear to be tinted reddish. The opposite is true for galaxies moving toward us very quickly; they are said to be “blueshifted”.
2. First of all, it would take ~8 minutes for us to even know. The force of gravity travels at the speed of light. The Sun would blink away, things like the moon and the other planets would stop shining and we’d travel at the same speed (~18 mi/s or 30 km/s) into the abyss of space.
