Yesterday, I started a facebook thread entitled “Ask Dr. Science.” My friends responded with the nagging questions about the nature of the universe that had been bothering them for a while. Some of my favorites:
Q: Is it true that the Earth will eventually get swallowed into the black hole at the center of the milky way? Does that make you sad?
A: No, but if it were, Yes. The earth’s only got about 5 billion years before the sun turns into a red giant, and even if we had longer, the black hole isn’t the unstoppable killing machine it’s made out to be. After all, it’s only grown to about 3 Million solar masses so far (about a millionth the total mass of the Galaxy). We’re fine.
Q: Why does the moon seem so big in the horizon but so small in the late night sky? I’ve been told the size doesn’t change. Please tell me it’s related to the oceans, as that is a good excuse for changes in size.
A: Rest easy in the knowledge that size doesn’t matter. And it’s not the oceans, either, although it _would_ be cool if the moon got bloated as it submerged. No, the reason the size seems to change is that near the horizon you have something to compare it to, trees and whatnot. Hold your thumb at arm’s length toward the moon when it’s overhead or near the horizon, and it both cases, it’ll approximately span the moon.
Q: Is it possible that the earth is spinning faster making a year seem as though it is much shorter … or is this just part of the aging process for humans? This is a SERIOUS question!
A: As it happens, the tidal forces from the moon cause the moon to slowly increase its orbit and slow down the length of the month. By the same token, the rotation period of the earth is slowing down. This means that the day gets longer, by about 4 milliseconds a century. So… since days are longer, there are fewer of them in a year, but that’s probably not the effect you were thinking of…. Read More
And the grand prize winner:
Q: Can all of Superman’s powers be explained as sub-effects of the singular ability to manipulate the inertia of any matter he comes into contact with?
A: I have to cheat here and expand your question. If we allow superman to (temporarily) change the mass or energy (same thing, of course) of the objects or fields around him, including himself, then we can explain:
Flight: (provided we basically allow him jump and then “swim” through the air) sure — although it’s not clear how he would maneuver in space.
Superspeed: Basically, this is just strength, so yes.
Heat vision: He’d have to do this really fast, but if absorbed visible light photons and reflected them at thermal energies, then sure. Of course, he’d also have to figure a way to increase the intensity of the radiation, or store the light for a long time.
X-ray vision: This is tougher. While he could change visible light to X-rays, it doesn’t do any good to shoot x-rays at people. It’s very bad, actually. X-ray machine work by passing x-rays through something, not by reflecting them.
Super hearing: Presumably if can amplify light-waves, we’ll let him amplify incident sound waves as well.
Freezing breath: One of the cases where he has to remove energy from the system. In this case, we’ve got a super-entropy decrease.
Nothing, however, can explain that ridiculous thing he does in Superman 2 when he throws his “S” emblem at General Zod and his minions.
— If you have your own random physics/astronomy questions, knock yourself out!