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Comment by sega_sai | Hacker News Reader

When there is no experimental evidence for black holes, it makes perfect sense to be resistant/skeptical to new type of objects with solutions involving infinities (singularity). Whether that's being irrational or not is up to debate. I'd say that's a good prior when there is no data (as there wasn't at the beginning of 20th century).

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On the other hand, the gold standard of scientific verification is the prediction of something not yet observed, and in that light, it seems to me to be somewhat inconsistent to reject a prediction of your own theory on the basis of it being at odds with your a priori feelings about how things should be, while still maintaining that everything else about your theory is correct.

Update: It is one thing to suppose that the singularity is a mathematical artifact, and another to reject black hole formation entirely. In this regard, the article seems vague about exactly what Einstein and Rosen were saying in their 1939 paper. It seems to me to be saying that, having concluded that collapse would not stop at the Schwartzchild radius and that would lead to a singularity, we should conclude that collapse to the Schwartzchild radius itself is not possible.

The article linked to this point is (IMHO) well worth reading, and seems to support this view of Einstein’s position.

Now it might be, but let's remember that back in the day Physics was mostly used to derive laws from observations. Only with the advancement of calculus, notation, etc. we could make predictions that later we confirmed. Granted, at the time of the black holes prediction this had been going on for a while so it should not have been too surprising, but also I don't think it'd be such a strong point as it is today.

Note that I was concurrently adding an update to my post as you posted this (though I think my update is orthogonal to your point here.)

With regard to contemporary attitudes to verification, we know that Eddington went to Principe to measure the magnitude of gravity’s effect on light specifically because it would be seen (and was) as strong confirmation of the theory.

Well yes, but they also knew stars collapsed, and that something had to happen in that case. Maybe at first they thought fine, everything becomes a white dwarf or a neutron star.

But then after Oppenheimer did the math in 1930 and showed that collapse into a black hole was within the theory of relativity would you still taken the same position?

If the theory of relativity was a person, it would not be old enough to drive or vote in 1930. :) It was an accepted theory, but it was not the wildly successful theory it is today.

Showing that a black hole was possible within the theory could just be a problem with the theory itself. Not necessarily an indication that they must exist.

This. Physics is a field of science, unlike math. They're dealing with models that keep on changing. Newton's model of F=ma is generally close enough for most things, but breaks near the speed of light. Following the model solely would give you the false idea that speed of light is just yet another number.

Case in point: the same equations predict white holes, which today are widely believed to not exist.

I’ve never seen one before — no one has — but I’m guessing it’s a white hole.

A white hole?

A door to past.

What is white hole ?

A region of space time matter/light/information can exit but you can’t send anything to.

https://en.wikipedia.org/wiki/White_hole

A person with a better astronomy background can jump in, but I'll start by quoting a couple trusted astronomy publications. In short, a white hole is an astronomical object with the property that light cannot enter it.

From the Universe Today (at https://www.universetoday.com/122715/what-are-white-holes/ ):

"Black holes are places in the Universe where matter and energy are compacted so densely together that their escape velocity is greater than the speed of light. […] Fully describing a black hole requires a lot of fancy math, but these are real objects in our Universe. […] So then what’s a white hole?

"White holes are created when astrophysicists mathematically explore the environment around black holes, but pretend there’s no mass within the event horizon. What happens when you have a black hole singularity with no mass? […]

"Now if white holes did exist, which they probably don’t, they would behave like reverse black holes – just like the math predicts. Instead of pulling material inward, a white hole would blast material out into space like some kind of white chocolate fountain. […] One of the other implications of white hole math, is that they only theoretically exist as long as there isn’t a single speck of matter within the event horizon. As soon as single atom of hydrogen drifted into the region, the whole thing would collapse."

And from Space.com (at https://www.space.com/white-holes.html ):

"White holes are theoretical cosmic regions that function in the opposite way to black holes. Just as nothing can escape a black hole, nothing can enter a white hole. […]

"To a spaceship crew watching from afar, a white hole looks exactly like a black hole. It has mass. It might spin. A ring of dust and gas could gather around the event horizon — the bubble boundary separating the object from the rest of the universe. But if they kept watching, the crew might witness an event impossible for a black hole — a belch.

"Physicists describe a white hole as a black hole's "time reversal," a video of a black hole played backwards, much as a bouncing ball is the time-reversal of a falling ball. While a black hole's event horizon is a sphere of no return, a white hole's event horizon is a boundary of no admission — space-time's most exclusive club. No spacecraft will ever reach the region's edge. Objects inside a white hole can leave and interact with the outside world, but since nothing can get in, the interior is cut off from the universe's past: No outside event will ever affect the inside."

I don't know a lot of advanced physics or quantum mechanics, but black holes also confuse me.

I would imagine that black holes show the limit of modern physics, there are still things to learn, and models of physics will probably be adjusted in the future.

I guess there are physicists who are able to predict how a black hole works and appears, and how it can be explained, but I haven't read about it.

my guess, in short, is that black holes are equivalent to infinite loops, and white holes solve the halting problem

That's quite a wild guess.

What does that even mean?

I mean, yeah there's tons of theoretical work. Predictions about lensing and structure have been done and verified. We've taken pictures of black holes. Susskind did a big fancy simulation for Interstellar that lined up great with them.

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