A philosophical problem of the Big Bang theory

The Big Bang theory accounts for the observed expansion of the universe. If the universe is expanding, then the further we go back in time, the smaller universe we find. Doing so, we eventually end up with the initial singularity, an infinitely small point of seemingly infinite density. But actual infinites are impossible in the physical world, because everything that is physical is, at least potentially, divisible - that is, we could always, at least potentially, take away something and still have something. So, it would be more accurate to say that the extention of a singularity tends asymptotically to infinitesimal - that is, is always approaching infinitesimal without ever reaching it. The problem is: are we, at this point, still talking about the absolute beginning of the universe? Or have we fallen into an infinit regress, wich would cause even more problems?
If you think there’s something about the Big Bang theory that I haven’t understood, feel free to point it out.

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You are correct. On the scale of the universe cosmologists generally use Einstein’s General Relativity. That works very well except…

As you point out when the universe was very young it was also very small; in fact it was quantum size. Unfortunately, General Relativity is not a quantum theory and it breaks down at such small sizes.

Hence the need for a theory of gravity which works at small, quantum, scales. Hence the search for a theory of Quantum Gravity.

Watch this space.

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When discussing the big bang we are discussing the beginning of this current universe.

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Are you saying that there could have been another universe before our universe? Where did that universe come from, then?

Philosophically we can define the universe as “all that exists”. Such a universe obviously has no external cause, since anything external to that universe cannot exist by definition.

There are a number of possible hypotheses as to the origin of the Big Bang, colliding branes or a multiverse spawning many universes, including our own. Currently there is not enough evidence to settle on any particular hypothesis, but at least the cosmologists are having fun.

When we talk about the universe, we usually talk about the physical reality. In this sense, if a non-physical reality exists, then the universe can have an external cause.

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Apparent infinity isn’t actual infinity. The Universe is still a finite quantity, and therefore not infinite in size/mass/anything. There is no issue here.

Eh, there are theists who would not say that God exists because exists is word that describes the way finite beings exist. But they don’t see only two options. God is something more. So to these hardcore apophatic theology theists, All That Exists would not include God.

But me myself I hold to the St. Thomas Aquinas’ analogy of being anyway, so I would still say God exists, even if his mode of being is unlike everything else.

Anyway, we’ve never observed a singularity. I’m not saying absolutely they don’t occur, but we frequently use singularities in idealized mathematical models of nature even if they don’t physically occur. That may be the case here, and it may be a red flag and reminder that General Relativity is itself a mathematical model of physical systems and one that can be improved on.

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Cyclical. This universe causes the next one. Rinse and repeat.

This would cause an infinite regress, wich is logically impossible.

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It’s not an infinite regress. Which would be linear. This is cyclical. Which is not.

If this universe causes the next one, it should have been caused by another one, wich should have been caused by another one, wich should have been caused by another one, and we could go on and on and on. If this isn’t an infinite regress, I don’t know what is.

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It’s still an infinite regression because something had to set off the sequence to begin with. A universe had to exist before it could reach its conclusion and begin the next iteration.

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IF anything in the universe had been slightly off this universe wouldn’t exist it would be completely different actually the odds that it happened as it did are astronomical I don’t think an exact duplicate universe exists unless for every possibility another universe comes into existence

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That is why I specified philosophically. I was including more than just the physical STEM universe.

Later I mentioned possible external causes for the STEM universe, such as the multiverse and branes.

Even if these hypoteses were true, there would be two possibilities:

  1. the events you described would need to be caused. In this case, we still end up with the necessity of a first cause.
  2. the events you described wouldn’t need to be caused. In this case, the principle of causality would have to be totally abandoned, and with it any possibility of an ordered, rational reality.

Why? The integer numbers are an infinite regress back to minus infinity yet they are far from logically impossible. The real numbers r in {r: 0.0 < r <= 1.0} are an infinite regress back towards, but never quite reaching, 0.0. Again, real numbers are not logically impossible.

We are talking about infinite regresses in causal series. Of course infinite regresses are possible in mathematical series.

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