Rethinking the origins of the universe

My understanding of what Laura Mersini-Houghton's paper is claiming is that stars cannot collapse into black holes, but they can get damned close. So those things that we have observed are not "black holes", but things that are damned close. In the paper, she and her co-author write, "Both effects (slowdown and mass-loss) balance such that the evaporating star remains very slightly outside its event horizon."

Even if this paper is correct, I don't think it's warranted to be so smug about people thinking they found black holes. We had a theory, and we had positive evidence for that theory. That's reasonable. If this paper is correct, then it turns out those things are not actually "black holes", but objects "very slightly outside" of being black holes. That's not too bad.

Disclaimer: I am not a physicist.

I think that interested people should just read the abstract, introduction and conclusions of the actual paper: http://arxiv.org/abs/arXiv:1409.1837

You will not understand the full implications of it (well, unless you are an astrophysicist), and I didn't bother with the meat of the paper (because I am also not an astrophysicist). But the abstract, introduction and conclusion are rather understandable, and far less hyperbolic than the press release. And even though I can't understand all of it, I'd much rather get a misunderstanding from the original source material, then get a compounded misunderstanding from a press-release.

We have observed things in our universe which match our expectations of black holes: http://en.wikipedia.org/wiki/Black_hole#Observational_eviden...

That we have observed something is not in dispute, as I understand it. What's in dispute is what, exactly, these things are.

> The other thing that sets off my hand-wave-o-meter is the pretending that we are somehow already observing these things "new telescope detects hints of black holes" or have concluded that they exist without any positive evidence.

Actually, the evidence is pretty good. We have orbital velocities around the mass at the center of our galaxy that cannot exist unless there is a very massive, very dense object at one focus of the ellipses:

http://astro.uchicago.edu/cosmus/projects/UCLA_GCG/

This doesn't prove anything by itself, it only reduces the number of possible explanations.

We also have general relativity, which basically says that, once you exceed a certain spacetime curvature, you enter into the realm where black holes (or something like them) are inevitable.

The observations are very good, and the theory has stood the test of time, producing very reliable and consistent results. None of this is conclusive, there are difficulties with general relativity at the smallest scales, but the black hole idea is a reasonable conclusion to draw based on both theory and evidence.

> In the hypothesis Einstein's field equations obviously break down ...

General relativity doesn't break down for a black hole per se, only the realm inside it. If we observe phenomena from a great distance up to the event horizon, GR reliably predicts the outcomes. Within the black hole, i.e. between the event horizon and the hypothetical singularity at the center, we have a the region for which claims like "all physics breaks down" are appropriate.

But the fact that general relativity cannot explain everything isn't by itself a reason to doubt what it can explain. But it is a reason to look for a more complete theory, one for which GR is a subset. The same can be said about quantum theory -- it also has domains of excellent agreement with observation, and other places where it's less useful.

> ... we seem to have bought into this completely untested idea that matter can continue bending space-time around into a singularity and all that.

But that idea isn't hypothetical, it's pretty easy to see that it falls out of the mathematics. I won't present the general relativity treatment, but here's one from special relativity that's easier to understand. This equation tells us the relationship between space and time in SR:

t' = t √(1-v^2/c^2)

t = time

v = space velocity

c = speed of light

t' = time rate of passage at velocity v relative to velocity 0

Now try increasing v so it equals c (try traveling at the speed of light). See? Time stops, which in SR is roughly equivalent to an infinite curvature in GR.

Photons travel at the speed of light. This means in their frame of reference v = c, and therefore t' = 0. Does this mean that photons don't experience time? That's exactly what it means. In a photon's frame of reference, it's created in an atomic interaction, then it's taking part in another atomic interaction somewhere else, with no intermediate time having passed.

The above example is pretty remarkable when you think about it, but it doesn't mean the laws of physics have broken down, any more than they do at a black hole's even horizon.

> 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".