Quote:
Originally Posted by
fire_faerie 
"I'm not sure but I think there is a principle that gravity follows called the Superposition Principle. According to the superposition, gravity is a force interacting between two bodies with no consideration of any other bodies around it. This means that each planet, regardless of the other planets' positions, exerts the same amount of gravity on the earth all the time - and that's why, in my opinion, a catastrophe could not occur from the planets aligning - because there is no importance to where they are in relativity of each other," Rachel said, her hand a little tired from being in the air for so long.
"Erm, I'm not sure that's correct," Kiri spoke up quietly, blushing. She hated disagreeing with her classmates, and this girl looked much older than Kiri -
and she was a Ravenclaw. Ordinarily, that would go towards convincing Kiri that
she was wrong, but Astronomy was the only subject where she could argue with some authority.
She turned around in her seat to look at the girl. Or, at least, her general direction. "I mean, gravity clearly does
not exert the same amount of pull all the time. It depends on the mass of an object and its distance - most of the time, anyway. If a planet is farther away, Earth feels less of its gravity than when it's closer. So, erm, yes, it changes over time. It's not constant."
Kiri was a little more encouraged as she continued, "And even if that was true, I don't think it would, you know, solve the problem stated in the article. If each planet just exerted its gravitational pull on Earth regardless of every other planet, in a conjunction, Earth would still feel all of their gravity coming from one side, and the tidal force would increase.
"I mean, I agree with you, there's absolutely no danger, but I don't think your argument, is, er... is entirely correct." Her face still felt a little hot.