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 Originally Posted by ImSavy
Always used to annoy me how people would just disregard the question "what was there before the big bang" because what we know as time didn't exist before the big bang, but that's not really what the question is asking and there are a few hypotheses about exactly this.
The question, "What is beyond space-time?" is not a physics question... yet. Physics is interested in observable things, and since that kind of question is about something not-yet-observed, there is just no evidence to back any claims.
Still, there is good reason to ask the question and to postulate what might be, and follow through to see what the implications are.
Originally Posted by ImSavy
The question that used to piss me off was we'd get told "matter can't be created or destroyed", which leaves to the obvious question where did it come from then? Which I never really had answered by a teacher, when in reality this isn't the case and it's just a simplified theory of what is really happening which when I found out I didn't really understand why it couldn't be explained to a 14 year old.
Well, Einstein explained that matter and energy are basically 2 sides of the same coin. Until then, the smartest people in the world believed that the Law of Conservation of Mass was correct. Most people even today don't have any clue what Einstein was talking about, so you can hardly blame your teachers... unless they were physics teachers.
The Law of Conservation of Energy still holds, though, once you accept that mass is a form of energy. The thing is that there is positive and negative energy, you see. The whole equation is really
E^2 = p^2c^2 + m^2c^4
where E is the energy, p is the vector momentum, c is the speed of light in vacuum, and m is the mass of the object.
This reduces to the familiar E = mc^2 when p=0.
Since p is the vector momentum, it can be positive or negative. E.g. 2 objects of identical mass moving away from a central point at the same speed have a net energy of 0.
So long as all the conservation laws are followed, all kinds of particles can pop into existence where there was "nothing" before. This is exactly what a particle accelerator experiment does. It smashes 2 protons into each other, annihilating them and producing a whole mess of particles that spray out. Two protons go in... hundreds or thousands of particles come out.
Check out this Encyclopedia Britannica article about Pair Production for a relatively simple explanation of 1 process by which energy becomes matter.
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