I hate it when otherwise sane-seeming physicists start spouting trash about the Big Bang. You can tell they're doing it by rote, that they're parroting some propaganda they've been indoctrinated with. Something they've never examined to see whether it makes a lick of sense.
First of all, there is no evidence for a Big Bang. There cannot ever be any evidence for it since the whole point of inventing Inflation Theory was to erase every last trace of the big bang to remedy the defects of the theory. The reason the Ekpyrotic model is viable at all is because of this total erasure of all traces of any big bang. But inflation? Oh you can't erase that! Even the Ekpyrotic model generally tries to replicate it. So what is today called "evidence for" the big bang is invariably evidence for hot inflation. Cosmic microwave background? Hot inflation. Expansion of the universe? Inflation.
Secondly, you have to realize that there can be no distinction between inflation and eternal chaotic inflation. If inflation happens then eternal chaotic inflation is the best possible model for it. You get eternity for free. Read my lips, no extra charges! Add quantum mechanics to inflation theory and you get chaotic inflation. And with chaotic inflation you have eternal inflation. It's FREE!
Worse than that, our living in a finite universe is mathematically impossible. If the probability of a universe arising out of nothing (assuming the whole notion isn't absurd which it is, more on that later) is finite then the probability of our living in an infinite universe is infinite. Infinity trumps finity!
If there were only one single eternal universe, and a billion billion billion finite universes, we could never tell the difference between them from any scientific experiments, but pure mathematics says that the probability of us coming from the eternal universe is 1 and the probability of us coming from any of the billion billion billion finite universes is ZERO.
It's statistically impossible.
The whole notion of something arising out of nothing is absurd. It's incoherent. It literally doesn't mean anything. The only way to ascribe any meaning to it is to say that the universe as-is is equivalent to nothing.
Which is very likely since a flat universe (as ours seems to be) has net zero energy. But to say that it's equivalent to nothing is to say that 'nothing' is subject to physical laws. or at least to mathematical laws. So it's not a true 'nothing' is it? It's something, it's laws of mathematics.
In order to say that what's beyond the universe is true nothing, you can't appeal to any sort of equivalence, you can't say that the universe came out of nothing at all. You can only say that the universe created itself. And what can you appeal to when making such a statement?
Well actually you can say that the universe created itself because it was self-consistent. But if you're going to say that then there are tons of other self-consistent universes possible. And every single one of them must have created itself.
Bravo, you've got the Mathematical (Multi)verse Hypothesis. Which is the exact kind of thing the Big Bang believers are trying to avoid. In trying to provide any kind of rigorous meaning to "the universe came out of nothing" you inevitably run into the fact that our universe can't be the only thing.
You get the same result when you try to define "non-determinism". It literally doesn't mean anything. And when you try to give it some meaning, it always turns out to be inconsistent with the vague notion of "non-determinism".
REVERSION TO RELIGIOUS DOCTRINE
So if the Big Bang is unprovable, mathematically impossible and it's not even coherent then why do these big headed logical types believe in this utter crap? Well first of all, physicists lack big picture thinking. Also known as judgement, which relies on synthesis. And synthesis is a cognitive trait physicists uniformly lack. But that only explains why it's possible for physicists to believe this crap.
Why they actually believe in it is because it's a religious notion. It's a belief in Creation. It's something that people used to believe in until science became atheistic. Until four young scientists made a manifesto and signed it with their own blood. That's why Einstein was so adamantly opposed to the Big Bang. Because it's a religious notion which science had gotten rid of!
And really, that explains it all. When cosmologists were confronted with the fact of an expanding universe, they couldn't handle the notion that ours isn't the only universe out there. So they reverted to religion. They reinvented the "Big Bang" - the Moment of Creation.
The same thing happened in the 1920s with the so-called Copenhagen "interpretation" of quantum mechanics. Which is no interpretation at all - it's the physical theory behind a bunch of useless math. Physicists like Richard Feynman who dismiss the physical meaning of math as unimportant are lackwits. So anyways, Copenhagen would be the physical meaning of QM if it weren't completely absurd and incoherent.
So believers in the Copenhagen doctrine revived vitalism because they couldn't handle the idea of a non-singular timeline. They invented all kinds of crap about "duality" and "uncertainty" because they couldn't handle that Platonism is wrong, that the universe really isn't made up of mathematical points. Even though mathematical points are physically incoherent.
They reinvented the notion that humans and other living things (so-called "observers") are Special, that they have this fundamental Living Force that makes them different from the rest of physical reality. How absurd is that!? But it's something that humans believe intuitively. It's an anthropomorphic notion. And that's why it got reinvented.
Same thing with Creation, or the Big Bang, whatever you want to call it. It's an intuitive anthropomorphic ('we are special') notion that just got reinvented when scientists were challenged to shatter it utterly. They were challenged and they failed. Because they're morons who can't grasp the big picture. Who can't grasp that maybe "creation" is something that needs to be defined before it means anything. Before it can ever be used to explain anything.
Kinda like God. For God to explain anything, it first needs to be defined. Which defeats the whole purpose of it since God is supposed to be this mysterious incomprehensible ball of crap and handwavy bullshit. And bullshit can't explain jack.
Same with Creation. /shakes head/
Previously, the disease process in physics.