[Potironette]

So..the dark blue I see at night is actually bits of blue light arriving from the other side of the planet :o?

Also, just a sort of random question out of curiosity: when a light in a room turns on, does the light actually travel/move to fill up the space or does everything just magically light up at once? Or, if I have a laser on top of one hill hitting a mirror over 186,282 miles away angled to hit some surface beside me, will there be a delay in my seeing that surface? Actually, this is probably a badly thought out question and stuff will take the time of light speed--and it just looks like a dark room fills up with light at once because light speed is so fast, and rooms so small.


I have a math review problem (midterms are coming up) that asks me to find a factor of (j-3)^2 - (k-5)^2 but I'm not sure how to do it. I tried to expand it, but just got j^2 - 6j - 16 - k^2 + 10k and it doesn't seem useful. Should I have expanded it at all?