[StefanKarpinski]

This paper claims that black holes can't come into existence, which is subtly different from claiming that they cannot exist. In particular, black holes can exist as long as they've always existed – it's just that new ones can't come into existence. Maybe the universe just has a fixed number of singularities. [I am not a physicist – this just struck me as an inaccurate implication in the article.]

[wuliwong]

I agree that it seems as if the article is a bit overzealous as to the implications of this work (claiming singularities cannot exist, in particular the one from which the big bang expanded). But, your idea that something has "always existed" in a universe that hasn't "always existed" doesn't seem plausible.

The author's claim that the big bang theory is now invalid because of this calculation of energy loss of a collapsing star being too fast to result in a black hole seems incorrect to me. The singularity from which the universe expanded (according to the big bang) is sort of "untouchable" by physics at the moment. I would guess there are some of the string/brane theory models out there that postulate what caused the big bang but currently it is my understanding that whatever information was around about the cause of that singularity is not accessible to us. Again, who knows what we will discover in the future but as of now, making any bold assertion about the lack of existence of that initial singularity seems presumptuous.

[kuhhk]

You're experiencing cognitive bias.

If it is presumptuous to present calculations that may invalidate a _theory_ based on assumptions, then it is also presumptuous to disregard such calculations and state that the _theory_ itself is automagically correct, just because the assumptions are untouchable.

A bold assertion indeed.

[lutusp]

> In particular, black holes can exist as long as they've always existed ...

This doesn't work in physics. If you say they can only exist if they've always existed, then you're obliged to say how they came into existence earlier -- the deep meaning of "always".

[kijin]

The article implies that since singularities can't come into existence now, there can't have been a singularity at the moment of the Big Bang, either.

That sounds implausible. Lots of things that cannot possibly come into existence at the present time did exist at the moment of the Big Bang (and shortly afterward), because the conditions back then were so radically different from they are now.

Perhaps the only singularity that ever existed was the Universe at the moment of the Big Bang. After the One Singularity has blown itself apart, no other singularity can come into existence. I don't see any inconsistency in that scenario.

[lutusp]

> The article implies that since singularities can't come into existence now, there can't have been a singularity at the moment of the Big Bang, either.

Yes, that's true, but if the paper's thesis is correct, then there aren't any black holes or singularities at all, at any time. If the thesis is false, then there can be black holes at the universe's beginning, and they can form today, given the right conditions.

> Lots of things that cannot possibly come into existence at the present time did exist at the moment of the Big Bang (and shortly afterward), because the conditions back then were so radically different from they are now.

Not so different, and from a theoretical standpoint, they lie on a continuum from the present to the past. The condition of the universe as a whole has changed over time, but from the present we can mimic earlier conditions using high energies.

It is often said that one goal of accelerator technology is to move backward in time toward the Big Bang. As technology advances, as accelerator energies increase, we create conditions more like the conditions in the early universe. The ultimate hope is to create conditions as much as possible like the first few seconds of the universe's existence, to be able to see the genesis of present conditions and refine physical theory.

> Perhaps the only singularity that ever existed was the Universe at the moment of the Big Bang. After the One Singularity has blown itself apart, no other singularity can come into existence. I don't see any inconsistency in that scenario.

A physicist would immediately see the inconsistency in that. If the conditions of the Big Bang theory can exist in reality, then given the same conditions of temperature and pressure, we should be able to imitate an earlier reality on a small scale. That's what an accelerator is designed to be -- an imitation of nature at an earlier time.

[kijin]

No, the article only claims that a singularity cannot arise from a collapsing blob of matter.

We have no evidence that the singularity that existed at the moment of the Big Bang was the result of a collapsing blob of matter. Therefore, we have no reason to think that it could not have occurred.

In fact, it might not even make sense to think of that initial singularity as the result of anything at all, since causality requires time and there was no time before the Big Bang. Time is asymmetric, and this is especially important when we're talking about t = 0. You cannot simply imitate it from the other direction.

[lutusp]

> No, the article only claims that a singularity cannot arise from a collapsing blob of matter.

If true, it calls into question the existence of the initial singularity thought to precede the Big Bang. The alternative -- that the working of physical theories depends on circumstances -- isn't a very good one.

People sometimes hypothesize that this universe arose as a fluctuation in some other universe. For this kind of speculation to have any credibility, we have to assume that any singularity can be explained by physical theory, not just present-day singularities.

My point is that a theory whose workings depend on the circumstances isn't a very powerful one.

> We have no evidence that the singularity that existed at the moment of the Big Bang was the result of a collapsing blob of matter.

Look at this logically. If there was a singularity at the moment of the Big Bang, then it arose from the same physical theory that creates them in the present, but on a bigger scale. The alternative is to argue that physical theory is inconsistent, depending on circumstances. That sort of condition undermines physical theory, makes it more like a soap opera than science.

> In fact, it might not even make sense to think of that initial singularity as the result of anything at all, since causality requires time and there was no time before the Big Bang.

Yes, true, but once time exists, then we can start describing phenomena as having causes and effects. So physical theory only applies after time zero, not before. But if, at time zero, there was a singularity, we can try to apply physical theory to it. I'm not saying we will be successful, but it would be a mistake not to try.

[kijin]

I'm not advocating the idea that the laws of physics depend on circumstances. I'm just pointing out that similar processes may have vastly different consequences, even according to the same theory, given vastly different environment variables (as evidenced by the ongoing Bash fiasco).

For example, we know that things tend to behave weirdly at quantum scales. It that because the usual laws of physics do not apply at quantum scales? No, our best theories should be able to explain why the scale makes such differences, and therefore accurately predict phenomena at every scale, both large and small.

Likewise, there would be nothing wrong with singularities occurring under some circumstances and not under others, as long as we can come up with a compelling theory to explain how the different circumstances affect the outcome.

That's the kind of theory we should try to come up with. Not hasty generalizations based only on limited observation of familiar circumstances. I'm not saying we will be successful, but it would be a mistake not to try.

[eyko]

There is the idea that there could be multiple, infinite number of singularities (and therefore universes).

[alchemism]

And with that, physics discovers Pandeism.