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This article is inaccurate I believe. It's inconsistent to state that we believe that the Big Bang theory is a theory about the origin of the Universe and in t

This article is inaccurate I believe. It's inconsistent to state that we believe that the Big Bang theory is a theory about the origin of the Universe and in the same time state that before some point in time we don't know what happened. If we don't know what happened before some time t, then we don't know the origin, by definition. I vaguely recall a physicist stating that a more accurate description of the big bang theory is that a long time ago, about 13.8 billion years ago, the whole universe was much, much more dense and hot, actually denser and hotter than the core of any star, and that it very quickly expanded (or rather diluted) and cooled. Back then it very much is possible the Universe was still infinite in space anyway, it was just much denser and hotter. And before that, we simply don't know.

pavel_lishin 11y ago
As I understand it, space and time didn't exist until the "instant" of the big bang - and that space itself began to expand. So it's not like a firecracker gases expanding to fill an empty box.
- grondilu 11y ago
  It's true that space-time itself did expand, but it's only speculation that space itself was created at the big bang. There may be theories that go far enough to explain the creation of space-time, but that's not the big bang theory.
lutusp 11y ago
> It's inconsistent to state that we believe that the Big Bang theory is a theory about the origin of the Universe and in the same time state that before some point in time we don't know what happened. If that rule were in force, mathematics would disintegrate because it's built on a foundation of axioms. But scientific theories are often predicated on axioms whose consequences are examined, but whose existence are accepted without explanation until a more encompassing, more global, theory is created. Like relativity replacing Newtonian gravitation -- the new theory still has axioms, but the theory explains and encompasses more. > If we don't know what happened before some time t, then we don't know the origin, by definition. A scientific theory is by definition a testable, falsifiable explanation of what can be observed. For each such theory, there are limits to what can be observed. > Back then it very much is possible the Universe was still infinite in space anyway ... Yes, unless (imagine time running in reverse) spacetime collapsed to a point, as is often claimed, and as relativity theory requires. In that case, an infinite universe would occupy no space or time at all. The notion of infinity doesn't require infinite size.

pavel_lishin 11y ago

As I understand it, space and time didn't exist until the "instant" of the big bang - and that space itself began to expand. So it's not like a firecracker gases expanding to fill an empty box.

grondilu 11y ago
It's true that space-time itself did expand, but it's only speculation that space itself was created at the big bang. There may be theories that go far enough to explain the creation of space-time, but that's not the big bang theory.

lutusp 11y ago

> It's inconsistent to state that we believe that the Big Bang theory is a theory about the origin of the Universe and in the same time state that before some point in time we don't know what happened. If that rule were in force, mathematics would disintegrate because it's built on a foundation of axioms. But scientific theories are often predicated on axioms whose consequences are examined, but whose existence are accepted without explanation until a more encompassing, more global, theory is created. Like relativity replacing Newtonian gravitation -- the new theory still has axioms, but the theory explains and encompasses more. > If we don't know what happened before some time t, then we don't know the origin, by definition. A scientific theory is by definition a testable, falsifiable explanation of what can be observed. For each such theory, there are limits to what can be observed. > Back then it very much is possible the Universe was still infinite in space anyway ... Yes, unless (imagine time running in reverse) spacetime collapsed to a point, as is often claimed, and as relativity theory requires. In that case, an infinite universe would occupy no space or time at all. The notion of infinity doesn't require infinite size.