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Thread: Black holes key to uniting general relativity with quantum physics?

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    Lightbulb Black holes key to uniting general relativity with quantum physics?

    The biggest issue in physics, science etc. Maybe one of the ways we can get a theory of everything is if we studied black holes, more than just staring at quasars or observing their pull on other objects like Sagittarius A. I'm surprised it's taken this long to even have an idea and execute it like the Event Horizon Telescope to image the actual event horizon.

    I saw the movie Interstellar last week and they mention this exactly, they can't unite gravity with quantum physics without getting data from a black hole. I wonder how true that is, if that's one of the only ways to unite general relativity and quantum physics since no physicists anywhere can do it so far from what our civilization has as far as data. If this is a high priority then studying black holes should be high.

    All we've had is theories like Hawking radiation and the holographic universe from Susskind. No real data from black holes. None of these provide a theory of everything.

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    yes, I have though this. An extreme environment for both quantum mechanics, and relativity.

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    Quote Originally Posted by MVAgusta1078RR View Post
    The biggest issue in physics, science etc. Maybe one of the ways we can get a theory of everything is if we studied black holes, more than just staring at quasars or observing their pull on other objects like Sagittarius A. I'm surprised it's taken this long to even have an idea and execute it like the Event Horizon Telescope to image the actual event horizon.

    I saw the movie Interstellar last week and they mention this exactly, they can't unite gravity with quantum physics without getting data from a black hole. I wonder how true that is, if that's one of the only ways to unite general relativity and quantum physics since no physicists anywhere can do it so far from what our civilization has as far as data. If this is a high priority then studying black holes should be high.

    All we've had is theories like Hawking radiation and the holographic universe from Susskind. No real data from black holes. None of these provide a theory of everything.
    My bold. Do you think we should be searching for some sort of data that in principle should be observable? If so, what do you have in mind?

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    The problem is that both theories seem to be right according to all of the tests we've done so far, and we even have reliable technology that depends on each of them in order to work. That's because, for most situations we normally experience or work with, they don't make significantly conflicting predictions. All we have is scenarios in which either they say pretty much the same thing, or one of them is applicable but the other isn't.

    That might sound like a description for two theories that don't actually conflict with each other and might even really not be two separate theories at all... but there are situations in which they do make conflicting predictions. And that's where we'd need to look in order to find which one's right, or find that neither is but we can develop a third option that does better than either of them.

    Black holes (especially around their event horizons) are such a setting. Others are in even shorter supply than that.

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    I think the problem is that the event horizon of a stellar-mass black hole is actually a pretty tame setting (and the event horizon of a supermassive black hole is tamer still). There are strong enough tidal forces there to rip apart matter, but not much more, you can do that with a wrecking ball. I don't think the evidence is very good that what you could observe from there will tell you much about quantum mechanics, it's pretty much a pure-GR environment. Perhaps there is a "wall of fire" at the event horizon if you tried to fall through, and perhaps there isn't (it's debated by people who know a lot more than I do, with no agreement), but I'm pretty sure you won't see much where we are-- too much gravitational redshifting. So I can't see why imaging a black hole, a la Interstellar, does much more than test GR. I could be wrong.

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    Quote Originally Posted by Hornblower View Post
    My bold. Do you think we should be searching for some sort of data that in principle should be observable? If so, what do you have in mind?
    What the Event Horizon Telescope is doing, imaging Sagittarius A's event horizon. There's even speculation by some physicists that SMBH might be wormholes depending on what size the event horizon is which they are waiting on. Why don't we send a space telescope like Hubble or Kepler to image black hole event horizons', either Sagittarius A or the closest stellar mass black hole.

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    Quote Originally Posted by MVAgusta1078RR View Post
    What the Event Horizon Telescope is doing, imaging Sagittarius A's event horizon. There's even speculation by some physicists that SMBH might be wormholes depending on what size the event horizon is which they are waiting on. Why don't we send a space telescope like Hubble or Kepler to image black hole event horizons', either Sagittarius A or the closest stellar mass black hole.
    Send? Sagittarius A* is 26000 light years away.It will be several 100000 years before we can do that., if ever. The Wiki article on Sag A* is here:

    http://en.wikipedia.org/wiki/Sagittarius_A*

    You can see Sag A* is an object of intense interest and is heavily studied with every observing tool we have. 4 million solar masses and a radius that would reach halfway to Mercury! I don't think I want to take that lady to dinner.
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

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    Quote Originally Posted by MVAgusta1078RR View Post
    Why don't we send a space telescope like Hubble or Kepler to image black hole event horizons', either Sagittarius A or the closest stellar mass black hole.
    Send the telescope where?

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    Quote Originally Posted by Shaula View Post
    Send the telescope where?
    Where Hubble and Kepler are, Earth orbit, but obviously better equipped to image a black hole. For some reason Hubble can image galaxies billions of light years away but not the accretion disk of a stellar mass black hole a few thousand light years away or Kepler for that matter can pick up exoplanets but not the event horizon of a black hole. I don't see why Hubble doesn't work but since we haven't with Hubble than a bigger more advanced space telescope.

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    The event horizon of a stellar mass black hole is much, much smaller than the exoplanets we've detected; even if one were pretty close, we wouldn't be able to resolve it with Hubble or anything similar. And Sagittarius A* is very far away. Distant galaxies are huge on a scale that's hard to comprehend, which is why we can get good images of them even very far away, even though we can't resolve an image of something tiny in comparison, even if it's rather closer.

    Note that the planned Event Horizon Telescope will actually be a linked array of radio telescopes in various locations. I think the plan is essentially to have multiple radio telescope facilities around the planet work together to give us an effective baseline the size of Earth; it's a great idea.

    I think that you're imagining that we haven't done this yet because nobody is interested or nobody cares, but that's not the case. It's that it hasn't been technically feasible. Astronomers have always wanted bigger telescopes and better resolution, and over the years we continue to push technology to let us see more. The current limits of resolution are simply the best we can do at this point, but we're steadily coming up with ways to do better, and we'll continue to do so.
    Conserve energy. Commute with the Hamiltonian.

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    And Sag A* is obscured by dust at opticle frequencies. Pointing Hubble at Sag A* will give us great pictures of clouds of interstellar dust much much larger than A*.

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    Oh, and I'd agree with Ken G that observing a supermassive or stellar black hole close up would probably be more useful for learning more about constraints of general relativity alone, rather than helping us merge quantum theory and general relativity. For the latter, we'd want nano-sized black holes, small enough that they exhibit strong quantum effects as well as strong relativistic effects. The only way we'd be able to observe such a thing would be to make it ourselves. Unfortunately, even our most powerful particle accelerators are many orders of magnitude too small to create such a thing (there was some panic from the uninformed that this could happen by accident at the LHC, but those fears were completely unfounded). I imagine that someday we might be able to do so, but it's not something that we'll be capable of any time soon.
    Conserve energy. Commute with the Hamiltonian.

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    I was thinking the same thing-- the way to use black holes to probe quantum mechanics is to make black holes that are themselves a kind of elementary particle. And then people will worry that it will eat the Earth or be its own universe that we have responsibility for....

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