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posted by janrinok on Sunday June 01 2014, @02:59PM   Printer-friendly
from the it-keeps-getting-more-complicated dept.

Zilong Li and Cosimo Bambi with Fudan University in Shanghai have come up with a very novel idea--those black holes that are believed to exist at the center of a lot of galaxies, may instead by wormholes. They've written a paper [abstract], uploaded to the preprint server arXiv, describing their idea and how what they've imagined could be proved right (or wrong) by a new instrument soon to be added to an observatory in Chile.

From the article:

Back in 1974, space scientists discovered Sagittarius A* (SgrA*) - bright source of radio waves emanating from what appeared to be near the center of the Milky Way galaxy. Subsequent study of the object led scientists to believe that it was (and is) a black hole - the behavior of stars nearby, for example, suggested it was something massive and extremely dense.

What we're able to see when we look at SgrA* are plasma gasses near the event horizon, not the object itself as light cannot escape. That should be true for wormholes too, of course, which have also been theorized to exist by the Theory of General Relativity. Einstein even noted the possibility of their existence. Unfortunately, no one has ever come close to proving the existence of wormholes, which are believed to be channels between different parts of the universe, or even between two universes in multi-universe theories. In their paper, Li and Bambi suggest that there is compelling evidence suggesting that many of the objects we believe to be black holes at the center of galaxies, may in fact be wormholes.

Plasma gases orbiting a black hole versus a wormhole should look different to us, the pair suggest, because wormholes should be a lot smaller. Plus, the presence of wormholes would help explain how it is that even new galaxies have what are now believed to be black holes - such large black holes would presumably take a long time to become so large, so how can they exist in a new galaxy? They can't Li and Bambi conclude, instead those objects are actually wormholes, which theory suggests could spring up in an instant, and would have, following the Big Bang.

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  • (Score: 1, Interesting) by Anonymous Coward on Sunday June 01 2014, @09:45PM

    by Anonymous Coward on Sunday June 01 2014, @09:45PM (#50002)

    I wouldn't overstate Hawking radiation *too* much -- it gets increasingly slow for increasingly large black holes. I think what's more likely to happen is mergers of dead galaxies will feed the hypermassive black holes at a rate far in excess of the infall from those galaxies -- the various frictions genuinely close to negligible and then, eventually, after many, many tens or hundreds of billions of years, those deadened stars will have started to fall in too. But there's other processes at play, too -- stars are always flung out of galaxies, let alone during mergers, and while yes it's true that future timelike infinity will be in a black hole that's a genuine infinity, whereas it's possible that even the likes of protons are unstable and will decay to radiation quite possibly long before encountering a hole. (Then, eventually, all those holes will themselves have decayed back to radiation, which will occasionally collide with enough energy to make matter -- or even tiny holes, and then back to radiation, like little eddies in the superlong wavelength radio waves. If we believe Penrose then since distance becomes quite meaningless in a pure-radiation universe, we could have a phase transition back to the radiation-dominated era at the start of another big bang, but he has never published anything on that one.)

    With acceleration, it really does depend on what's causing that. The acceleration is a feature of a smooth universe, and any local gradients will muck up the pressure, quite possibly enough to stop it from locally being "anti-gravitational" at all. A gradient-dominated field would have an equation of state of w=-1/3 (so satisfying the weak energy condition, barely, rather than violating it), and a velocity-dominated field has a super-stiff equation of state w=-1. The equation of state will therefore be highly position-dependent and range between -1 and 1, and we need between -1 and -1/3 to get an acceleration. It's possible then that an acceleration caused by a quintessence will not tear galaxies apart because it simply won't act that way in the presence of lumpy matter. This effect is naturally heightened if the field couples to matter, such as a Galileon, a chameleon or a symmetron.

    On the other hand, if it's a cosmological constant we still don't have to worry, since even though this will keep an equation of state of -1 everywhere and in every spacetime, we have solutions for things like Schwarzschild-de Sitter (black hole in the presence of a cosmological constant) or Lemaitre-Tolman-Bondi-de Sitter (spherical cluster in the presence of a cosmological constant) and the solutions are stable. The point is that acceleration in this way is a facet of the *global* spacetime, assuming that that spacetime looks like Robertson-Walker and obeys its evolution equations. On a local level, and GR is nothing if not a local theory, it's not necessarily the case.

    (Having fun with phantoms, though, and yeah you'll rip your galaxy apart long before the hole eats it all.)

    Sorry again for being a douche; you're right, somehow in a two-line post I missed an important point in my haste to spew a load of things on page which while broadly accurate were almost irrelevant to your post, which had nothing wrong with it (except perhaps a couple of missed edge cases).

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