Why does it not propagate where sound does, and vice versa?
Something I myself forgot to ask.
Also, you seem to be thinking of the sun and stars as focused spotlights, which they are not. They are throwing light in all directions, and only tiny infinitesimal amounts of that light actually point at earth.
I think scepti is talking about the light coming off the star at angles (thus allowing us to see the edges of a star, along with the side directly facing us) and since the star is bigger than Earth, the same wall of light/energy we'd receive close up from those "parallel rays", should also be received far away.
Yes we can see those photons on the sides but we don't feel the radiation from them.
Actually, we do. The energy they carry reaches us, whether that energy be visible light, IR (heat), UV or whatever. The reason we aren't getting cooked is that we only receive the energy from the photons that came in this direction, which is a relatively small portion of the total number of photons emitted. Actually, if I can chuck in some more numbers, the earth only receives 4.5x10
-10% (if I got my maths right this time
) of the total energy output from the sun, because all the rest of that energy has gone off in other directions. Even that tiny amount of energy is quite powerful though; it's a common occurrence for the bitumen on the roads to melt during summer in my home town, and that's 30° South of the equator!
Oh, and keep in mind, that 4.5x10
-10% of the sun's total energy output is spread over the ~255,000,000km
2 of the earth's surface that is exposed to the sun at any one time, so the bit that we feel on our ~1m
2 of exposed skin (if we're average build and not wearing any clothes) really is a very tiny proportion of the total output (about 1.8x10
-24%).