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The strange fate of a person falling into a black hole

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Re: The strange fate of a person falling into a black hole

#91

Post by ars »

monocasa wrote: post #77

So I've had a question about stellar mass black holes that I can't seem to be able to get answered (the question was deleted for /r/askscience). How does a stellar mass black hole actually form a singularity given the fact that there's gravitational time dilation? Wouldn't the heart of a black hole slow down relative to an outside observer as mass is added to it so that you never actually reach infinite density? It s…

I reached the same conclusion years ago, and the answer is very simple (and controversial): Black holes do not exist.

If they existed they could exist, but it's impossible for them to form.

I've asked many many physicists this very same question, and none could answer me (or I've gotten hand-wavy non answers). It's like no one wants to be the first to declare this well accepted thing as non-existing.

The black holes observed by astronomers are not actually black holes, but rather super massive neutron starts. It's not possible to distinguish between these two objects, astronomers assume a black holes based on size, not based on observed phenomena.

Re: The strange fate of a person falling into a black hole

#92

Post by ars »

tvmalsv wrote: post #9
guard-of-terra wrote: post #2

You can only get inside black hole after time ends. That's because universe-time stops at the horizon. The moment you fall in, Anne is dead eternally long ago. Also, you are incinerated by a billion years of starlight per your second, including energetic particles I guess. You will observe the end of universe and death of everything in it before diving.

If that were the case, wouldn't that mean that the moment a black hole is formed, it would never become any larger? How have super-massive black holes formed in less than 14 billion years?

The answer is both simple and controversial: They have not. Black holes do not exist because they take an infinite amount of time to form. See the thread elsewhere on this page.

Re: The strange fate of a person falling into a black hole

#93

Post by aesthetics1 »

jamesdelaneyie wrote: post #60
dvdkhlng wrote: post #17

Somewhat related: there is a short story by Greg Egan, "The Planck Dive", describing a voyage (without return) into a black hole, in a scientifically not too absurd way. You can read it online: http://gregegan.customer.netspace.net.au/PLANCK/Complete/Pla...

Have yet to read this but huh – manually responsive web design!

That's actually really interesting. Imagine having a feature like this built into browsers for dealing with long articles and text. Yes, we have 'zoom' but that typically breaks things at a certain point. Easily swapping the background and even the left/right bias of the text is a pretty neat tool to include, even though it isn't that intuitive on the site.

Re: The strange fate of a person falling into a black hole

#94

Post by DannoHung »

jessaustin wrote: post #86
ekianjo wrote: post #34

Earlier quoted context omitted.

interstellar was more a pile of nonsense than Science.

This is not an insightful response. Of the people I know who watched the movie, those who objected the most to the science were those with little scientific training. (Similar to a relative of mine who is certain that we will "never" have self-driving cars...) If you are knowledgeable, and have specific objections, those might be more insightful.

Nah. Someone should've realized Miller's world was a bad idea before they went down there and made the whole thing a screw up.

Oh, or what about the fact that they "solve" Gravity and decide to leave Earth. HELLO, YOU NOW HAVE INFINITE ENERGY! YOU CAN FIX ANY PROBLEM WITH BRUTE FORCE!

Re: The strange fate of a person falling into a black hole

#95

Post by contravariant »

monocasa wrote: post #87
contravariant wrote: post #85

Earlier quoted context omitted.

Indeed you won't ever be able to ever see something fall into it, but when you get down to it that's just because the light will take an infinitely long time to reach you. There are coordinate systems that are able to describe stuff falling past the event horizon in finite time, you just won't be able to see this happening until you fall into it yourself.

My question isn't along the lines of how visible it is to an outside observer, it's more of how can a singularity itself form? It seems like you can't reach infinite density in finite time given gravitational time dilation.

It only takes "infinite" time in that particular coordinate system, it takes finite time in other coordinate systems, such as one where you're in orbit around the black hole.

Re: The strange fate of a person falling into a black hole

#96

Post by contravariant »

digsmahler wrote: post #89
contravariant wrote: post #85

Earlier quoted context omitted.

Indeed you won't ever be able to ever see something fall into it, but when you get down to it that's just because the light will take an infinitely long time to reach you. There are coordinate systems that are able to describe stuff falling past the event horizon in finite time, you just won't be able to see this happening until you fall into it yourself.

Are there such coordinate systems that "describe stuff falling bast the event horizon in finite time"? How does that not violate general relativity?

According to general relativity those coordinate systems are equivalent. Well apart from the fact that the "classical" coordinate system isn't able to describe the inside of the black hole. For an example see the Kruskal coordinate system [1].

[1] https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coord...

Re: The strange fate of a person falling into a black hole

#97

Post by btilly »

digsmahler wrote: post #89
contravariant wrote: post #85

Earlier quoted context omitted.

Indeed you won't ever be able to ever see something fall into it, but when you get down to it that's just because the light will take an infinitely long time to reach you. There are coordinate systems that are able to describe stuff falling past the event horizon in finite time, you just won't be able to see this happening until you fall into it yourself.

Are there such coordinate systems that "describe stuff falling bast the event horizon in finite time"? How does that not violate general relativity?

To the first, yes. For example http://en.wikipedia.org/wiki/Lema%C3%AEtre_coordinates is one.

To the second, when we talk about "coordinates" in GR, we're talking about parametrizing a volume of space-time. Given one parametrization, it is possible to create another parametrization that blows up at any particular spot - not because space-time is weird there - but because you picked a bad coordinate system.

The existence of parametrizations that carry through the event horizon demonstrate that the singularity at the event horizon in Schwarzschild's original metric is not a real problem for GR.

However the singularity at the middle of the black hole is a spot where GR breaks down. It is widely believed that a theory that combines GR and QM will make that singularity impossible.

Re: The strange fate of a person falling into a black hole

#99

Post by lottin »

drdeca wrote: post #79
lottin wrote: post #71

How can something that doesn't really exist such as space and time possibly be warped? Physicists need to get a grip and understand that their model of the universe is completely wrong. There is no space or time and the universe has no shape.

Do you have a line of reasoning for that? Models which take spacetime to be able to be warped, /to my understanding/, make what are currently the predictions which are most matched by experiment. I don't know why one would suppose that space and time do not exist, other than as some philosophical idea, but even if one does suppose that, it still appears to work well to model the universe as if they do exist. One woul…

The reasoning is very simple - If space does indeed exist, it must be somewhere, because everything that exists is somewhere, but space can't be anywhere, because if it's somewhere it must be contained in space. How can something be contained within itself? It can't.

Re: The strange fate of a person falling into a black hole

#100

Post by dragonwriter »

logfromblammo wrote: post #78
kagamine wrote: post #38

Earlier quoted context omitted.

> The instant you entered the black hole, reality would split in two. From the 3rd paragraph. However, yes the alternate universe comes into existence when you reach the singularity. Still, if you can exist both inside and outside, then your ashes can exist in both places alongside living you without causing a paradox because you simply will not exist in the same space as you ashes that will arrive very much later an…

Reality only splits in two in the sense that the observer-dependent reality of the person falling into the black hole and the observer-dependent reality of the person remaining outside of it can no longer exchange information anywhere except inside of the black hole's event horizon. The half of your light cone that extends into the future remains entirely within that event horizon. The outside observer's cone can rem…

> There might even be a sort of Zeno's Paradox inside, where once you cross the event horizon, there's another event horizon beyond that, such that anything that much closer to the singularity than you are can never communicate with you, in the same way that you can never communicate with the universe outside the first event horizon.

Isn't every step in from the event horizon effectively an event horizon? If all the mass of a black hole is effectively at the singularity in the center, and escape velocity is the speed of light at the event horizon, won't there be no point within the event horizon where escape velocity is less than the speed of light, such that at any point within the event horizon, no point farther from the event horizon is within the future light cone of that point.

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