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New Evidence for Open Universe

Posted by michael on from the reverse-engineering-the-cosmos dept.

Observations made by the Hubble telescope have produced evidence that the universe is full of "dark energy", stuff that has mass but does not emit nor block light, and that a disregarded theory first postulated by Einstein about "negative gravity" is actually valid. If true, this would provide firm evidence that the universe will not collapse in a "big crunch" but will expand indefinitely. See the SF Chronicle, New York Times, MSNBC, or CNN for stories (the Chronicle story is the best, IMHO). For background information, you may want to check out the cosmology FAQ or more information about negative gravity. (Update: 04/04 11:03 AM by michael : A couple of people have pointed out that this write-up is inaccurate; I'm not going to try to correct it, but read the comments for more information.)

7 of 231 comments (clear)

  1. As always... by Amphigory · · Score: 5
    As always, I am most interested in the philosophical implications. If this ever-expanding universe idea is correct, then there is no "cosmic contraction" to provide the point of mass & energy which exploded in the big bang. That is, there is no never-ending cycle of "big bang/big crunch", and steady state is well and truly dead.

    This leaves you with a singularity that exploded for no apparent reason and existed for no apparent reason. Where did it come from? Why did it explode?

    How complex do things have to get before "God did it" becomes the best explanation?

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    -- Slashdot sucks.
    1. Re:As always... by fiziko · · Score: 5

      > This leaves you with a singularity that exploded
      > for no apparent reason and existed for no
      > apparent reason.

      I can't tell you if it had a reason for existance, but it may be possible to explain why a singluarity exploded. (That whole "where did it come from" question cannot be answered by science: a singularity destroys almost all information about what it was made of. All you can possibly know about what a black hole as absorbed are the total mass, and net charge and angular momentum of what it swallowed. You need the "God did it" method if you demand an answer to that question.)

      Stephen Hawking has shown that the particle-antiparticle pairs that are perpetually being created in all of space (according to the current models) can provide a mechanism for a black hole to lose mass and energy. To explain how, we first must relax the conservation of energy by incorporating the results of quantum mechanics.

      In high school, you were taught that energy can neither be created nor destroyed, only transformed. Well, this is mostly true. Conservation of energy can be violated, provided that violation can never be observed. The Heisenberg Uncertainty Principle of quantum mechanics puts limits on our observations. (Our uncertainty in the energy of a particle, multiplied by our uncertainty in the time we spend measuring it must be no smaller than an amazingly small number, Plank's constant h divided by 4pi.) The Universe can violate energy conservation, provided that excess energy is gone so fast it cannot be observed.

      The Universe, therefore, is able to conjure up a particle and its antiparticle anytime, anywhere. The creation of these particles is referred to as vaccum fluctuations. Anyway, these particles can be produced near a black hole.

      What happens if one of these particles falls into the black hole, while the other has enough energy to escape? Well, if you do the math, you find that in some cases, the particle that escaped can survive indefinitely; it can behave exactly as if it were a real particle.

      What effect does this have on the black hole? The net effect is a loss of energy. Because of mass energy equivalence, this corresponds to a loss of mass. In effect, the particle that escaped is behaving as though it had escpaed the black hole. If this happens often enough, a black hole can reach a point where it no longer meets the requirements of mass and density to be a black hole.

      What happens then? Well, nobody really knows. There are a lot of theories, including a Big-Bang type explosion. The one point I feel I should note is that, if this were a Big Bang sort of situation, then there would be matter in the Universe outside the singularity before it exploded. I'm still not sure how much matter this would be. I also don't know what kind of timescales it requires; if it's fast enough, it may appear as though it were a single explosion.

      This may not be the answer you're looking for, but I hope I convinced you that answers are possible when you're asking what triggered the Big Bang.

      --
      - W. Blaine Dowler
      http://www.bureau42.com
  2. Some additional points. by RobertFisher · · Score: 5

    For full disclosure, I am a physics graduate student working in the astronomy department at Berkeley. Although I am not a cosmologist, I heard the latest on the supernova searches from one of the key investigators yesterday at an informal brown bag lunch. As a regular /. reader, I thought I would put in my own two cents worth of corrections and additional info.

    First, the existence of a cosmological constant is NOT at all news. Prior observations by both the LBL group doing observations of supernovae type Ia (group page) and the BOOMERANG group doing observations of the cosmic microwave background (group page) verified the existence of a cosmological constant several years ago.

    Second, as a previous poster has stated, the geometry of the universe is NOT necessarily open.
    See especially this informative figure which shows the allowed region of parameter space based on both the SNIa and the BOOMERANG results. As you can easily see, the combined results are consistent with a flat universe with a cosmological constant, but the flat universe is a critical case, and one cannot exclude either an open or closed universe.

    Third, what IS new is the detection of an extremely distant SN at redshift z = 1.6. The discovery, made largely by Adam Riess, who is now at the Hubble Space Telescope Institute, was largely serendipitous; it was detected in the Hubble Deep Field, and a number of prior observations allowed Riess to piece together a light curve from which he could infer the intrinsic luminosity. The NEW results are remarkable for two main reasons :

    1) Critics have argued that a thin smattering of grey dust in intergalactic space could mimic the effect of a cosmological constant (ie, for a fixed redshift, objects seen are dimmer not due to an acceleration of the expansion of the universe, but instead due to obscuring dust along the line of sight, where the dust must absorb equally well at all frequencies). However, at very high redshift, the relative contribution of matter is higher, and so objects seen are BRIGHTER than what one expects in a freely coasting universe. This is not the trend predicted by the simplest dust model. So the recent evidence is one further advance for the non-zero cosmological constant model.

    2) At such high redshifts, clocks appear to be moving faster because of the relative expansion of the universe since then (a photon wavelength is stretched out, but c remains constant, hence the photon frequency is also slowing in time in the universe, as are all clocks). The high redshift SNIa light curve exhibits this general relativistic time effect, and one cannot make sense of the curve without correcting for it.

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    Science, like Nature, must also be tamed, with a view turned towards its preservation.
  3. Astronomy Picture of the day by alexjohns · · Score: 5

    http://antwrp.gsfc.nasa.gov/apod/
    Today's Astronomy Picture of the day is all about this, too. It's got a bunch of links at the bottom for people wanting to read more.
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  4. Open universe ? by Salsaman · · Score: 5

    Great ! Does that mean I can change its source and recompile it ?

  5. Re:Einstein's mistake by krlynch · · Score: 5

    It was a psuedo-mistake. It was thrown in because it *can* exist.

    It was not a mistake to include it, not even a pseudo-mistake. At least in hindsight :-) And I don't mean from an observational viewpoint; from a fundamental theoretical viewpoint, you EXPECT there to be a cosmological constant term. Here are just two reasons:

    • The Einstein equations (with the cosmological constant term) are the most general (torsion free) equations you can write down using the metric and its first derivatives, that is invariant under general coordinate transformations. If you DON'T include the cosmological constant term, you have to come up with a new symmetry that appears in nature and that explains why there is zero vaccum energy. Explaining how you can leave it out is a more vexing problem than putting it in in the first place.
    • From fundamental particle physics, we expect the cosmological constant to be non-zero; every time you pass through a symmetry breaking phase transition (such as the electroweak phase transition, or a GUT scale transition, or breaking supersymmetry, or any of innumerable other phase transitions), the vacuum energy density is increased...i.e. there are positive contributions to the cosmological constant. (Now, those contributions from known phase transitions are naively sixty or seventy orders of magnitude larger than the observations, but that is another problem :-) So again, without some other unknown mechanism, you expect it to be nonzero.

    The problem since the seventies has not been to explain why the cosmological constant is not zero (since you wouldn't naively expect it to be), but why it is so CLOSE to zero; that is, why does the universe have some approximate symmetry that keeps the cosmological constant so small, despite what would otherwise be its natural inclination to be large.

  6. NOT OPEN!! by rknop · · Score: 5

    A common misconception, left over from decades of cosmology textbooks which implicitly assumed a zero cosmological constant (equivalently, no dark energy). These textbooks all make the equation that closed geometry = universe recollapses, open geometry = universe expands forever, flat geometry = borderline case.

    In fact, if you have a cosmological constant (or dark energy), you can have a closed univere which expands at an accelerating rate.

    The best evidence about the geometry of the universe currently comes from cosmic microwave background observations, which suggests that the geometry is *flat*. The supernova evidence suggests that the expansion of the universe is accelerating.

    It is a mistake to state that an eternal expansion, or an accelerating expansion, is an "open" universe.

    -Rob