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Physics, Astronomy & Cosmology / Where is the point of maximum gravity inside a planet or star?

« on: 05/12/2012 01:16:56 »

We always treat gravity as attracting things to the *center* (of gravity) of a planet or star, for instance let's consider one called Plar. But if you were *inside* Plar, it would be different. At the center, you would be pulled out in every direction right? So do those forces simply cancel out and you feel nothing or do they create a tension that pulls things apart? I lean towards the first one.

In that case, where is the net force due to gravity maximum? How far into the center? And also, where is the "pressure" maximum from all the stuff sitting on top of you? Is it still the center because it all adds up from the higher material?

You can assume Plar is homogenous if that helps, surely it can be figured out with some calculus, but I'd also be interested in Earth. Finally, does this phenomenon have any noticeable effects, like on the nuclear reactions in stars or can a hole form from material being pulled out?

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Physics, Astronomy & Cosmology / Why do we assume the Big Bang was the beginning of everything?

« on: 04/12/2012 09:23:28 »

Hi, I'm new and have a bunch of questions, this is my first one. Hope you can help!

So there's plenty of evidence of a huge explosion/expansion 13.7 thousand million years ago. But what makes us think it was the beginning of EVERYTHING. Couldn't it have merely been *a* big bang caused by something? Couldn't the Big Bang turn out to be relatively tiny compared to the actual entire universe? How do we know that there is nothing behind the CMBR? And isn't this analogous to our previously supposing that the Earth was the centre of the solar system (and indeed the universe)?

Also, in my opinion, just because we discovered a cataclysmic event, doesn't mean it's the answer to all of our questions about our origins. Science can never answer philosophical questions.

Side question: Isn't it illogical to mention something like a multiverse when that goes against the notion of *the* universe? In a similar fashion to how atoms are made up of smaller things so that their name no longer seems appropriate?