wyatt@cfa.HARVARD.EDU (Bill Wyatt) (12/19/89)
From article <963@YaleVM.YCC.Yale.Edu>, by HOWGREJ@YaleVM.YCC.Yale.Edu: > In article <822@tahoma.UUCP>, jpg3196@tahoma.UUCP (James P. Galasyn) writes: >>I just heard from a fairly reliable source that CalTech has demonstrated >>the Big Bang never happened. [...] > [...] I really don't know how you could *disprove* the BB; it's > been pretty well accepted since the '60s. There's a lot of data that it > explains real well that you'd have to come up with a better explanation > for... 3 degree background, expansion, primordial nucleosynthesis, etc. > The BB theory, combined with Guth's inflation, does a fine job at the > moment... [...] Well, the BB in general is separate from inflation theory. And no, inflation theory certainly does not do `a fine job': it is a pretty theory completely at odds with observations. Most theorists really *want* the Universe to be closed (i.e. Omega >= 1.0), so much so that they call these the `standard' theories. People ignore the fact that the standard theories currently require exotic (i.e. unknown) physics. The inflation theory predicts Omega is exactly 1.0000... , but every piece of observational evidence says Omega is between 0.1 and 0.3, so the Universe is open. There are lots of truly creative ways of reconciling the discrepancies; shadow matter, tailored particles, etc., etc. None of them has any observational basis; their sole reason for being is to close the Universe. Bill Wyatt, Smithsonian Astrophysical Observatory (Cambridge, MA, USA) UUCP : {husc6,cmcl2,mit-eddie}!harvard!cfa!wyatt Internet: wyatt@cfa.harvard.edu SPAN: cfa::wyatt BITNET: wyatt@cfa
stubbs@astroatc.UUCP (Dennis J. Kosterman) (12/20/89)
In article <822@tahoma.UUCP> jpg3196@tahoma.UUCP (James P. Galasyn) writes: > >I just heard from a fairly reliable source that CalTech has demonstrated >the Big Bang never happened. I haven't heard anything else about this, but on the surface it sounds suspicious. Scientists don't usually make assertions this dog- matic. I don't see how it's possible to say absolutely that the Big Bang did or did not occur. We can only talk about probabilities. Dennis J. Kosterman uwvax!astroatc!stubbs
panoff@hubcap.clemson.edu (Robert M. Panoff) (12/20/89)
In article <822@tahoma.UUCP>, jpg3196@tahoma.UUCP (James P. Galasyn) writes: > > I just heard from a fairly reliable source that CalTech has demonstrated > the Big Bang never happened. Cjeck out the latest issue of The Sciences, published by the New York Academy of Science. There are a number of fine articles, including one by Anthony Peratt of Los Alamos which discusses how the universe could have come to be the way it is without postulating a Big Bang. This is a far cry from sayong that it ``proves'' the Big Bang never occurred. If there is enough interest, I will summarize this article for the net. The article is titled, ``Not With a Bang -- The Universe May Have Evolved from a Vast Sea of Plasma.'' One quotation is worth including: ``Many physicists believe the time is fast approaching when the big bang must prove its worth anew or step out of the limelight.'' -- rmp, for the Bob's of the World
tim@hoptoad.uucp (Tim Maroney) (12/20/89)
In article <263@cfa.HARVARD.EDU> wyatt@cfa.HARVARD.EDU (Bill Wyatt) writes: >The inflation theory predicts Omega is exactly 1.0000... , but >every piece of observational evidence says Omega is between 0.1 and >0.3, so the Universe is open. There are lots of truly creative ways of >reconciling the discrepancies; shadow matter, tailored particles, >etc., etc. None of them has any observational basis; their sole >reason for being is to close the Universe. I've often wondered about this. So many scientists seem to take the dark matter for granted, but I've yet to see any clear reason for postulating it other than a sort of religious dogma that the universe will eventually recollapse. Is there really any stronger basis for believing that we only see ten percent of the universe, or are people letting their aesthetics guide their modeling? -- Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com "I've been called an evil genius by cities of assholes... but I know who these people are! And they're on my list!" -- Robert Crumb
cet1@cl.cam.ac.uk (C.E. Thompson) (12/20/89)
In article <2951@astroatc.UUCP> stubbs@astroatc.UUCP (Dennis J. Kosterman) writes: >...... I don't see how it's possible to say absolutely that the Big >Bang did or did not occur. We can only talk about probabilities. !!!!!!!!!!!!! Likelihoods, not probabilities, *please*. Or are you all unreformed Bayesians out there? Chris Thompson JANET: cet1@uk.ac.cam.phx Internet: cet1%phx.cam.ac.uk@nsfnet-relay.ac.uk
ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) (12/20/89)
As someone who has spent some years playing with cosmology, I'd thought
I'd kick in a few comments on the Big Bang.
There are at least two senses in which people are using that
phrase. In one sense it refers to the idea that are universe is
currently expanding, has been doing so for some time, and at some
finite time in the past (somewhere between 10 and 20 billion years ago)
was extraordinarily hot and dense. In another sense it refers to
the idea that the universe began with an initial singularity, and
"before" this point neither time nor space existed. The first version
of this idea can be analyzed using our current understanding of
physics (like GR, particle physics etc.) and by choosing to approximate
our universe as homogeneous and isotropic. This usually goes by
the name of the "standard model".
There is an impressive amount of evidence in favor of the first
idea and no compelling evidence against it. Besides being consistent
with physics as we know it, it can be tested by comparing the
current blackbody background temperature (probably 2.75pm.05)
with the estimates of the primordial abundance of certain light
elements (H, He3, He4, D, Li7). Consistency between these
figures can be used to constrain the average baryonic density
of the universe (This does not represent a trivial prediction.
It is difficult to get consistency and easy to imagine answers
for the elemental abundances which would be inconsistent with this
picture.) In addition, it has been used to predict the number
of light, or massless weakly interacting particles (i.e. neutrinos).
This prediction has just been verified. It is probably worth
noting that the predicted abundance of baryonic matter is not
inconsistent with dynamical estimates of the mass density of the
universe. It has already been mentioned here that this model
has the only consistent explanation for the blackbody background.
The weakest aspect of this model is that it does not incorporate
galaxy formation. There are a number of galaxy formation models
that are consistent with the standard model, some of which cannot
be ruled out at the present time. None of them is particularly
compelling, although models using cold dark matter are probably
ahead of the rest. These models may fail if current observations
of large scale structure and motion hold up. One of the tightest
constraints on all such models is the incredible isotropy of
the blackbody background. The growth of gravitational structure
in an expanding universe is slow enough that the perturbations
that would have to grow into galaxies should have left some
remnant disturbance in the blackbody background.
Inflation is a way of explaining the features of the standard model
by using particle physics, and appealing to the high temperatures
present at *very* early times. It is a nice idea, but has problems
and may not end up as part of the standard model. As someone
else has noted it does seem to predict that the universe is
very close to critical density. It does *not* predict that
the universe is closed or open (although specific models of inflation
do make such predictions). The bulk of the observational evidence
seems to indicate that the universe has a much lower mean density.
Inflation (at least in some versions) also predicts a power spectrum
for temperature anisotropies in the blackbody background.
The idea of the Big Bang as a real singularity in the fabric of
space-time is another issue. This view results from an unreasonable
extrapolation of classical GR into temperature regimes where quantum
effects must be important, and there is no consensus view on how to
make such corrections. There have been many speculative papers on
how to do away with the initial singularity without changing the
standard model appreciably. None of them command general assent, nor
are they likely to in the near future.
The bottom line is that the initial singularity and inflation could
be disproved (in some sense) tomorrow and our view of the universe
would not have changed a great deal. I certainly wouldn't regard
it as the death of the "Big Bang Theory".
--
I'm not afraid of dying Ethan Vishniac, Dept of Astronomy, Univ. of Texas
I just don't want to be {charm,ut-sally,emx,noao}!utastro!ethan
there when it happens. (arpanet) ethan@astro.AS.UTEXAS.EDU
- Woody Allen (bitnet) ethan%astro.as.utexas.edu@CUNYVM.CUNY.EDU
These must be my opinions. Who else would bother?henry@utzoo.uucp (Henry Spencer) (12/21/89)
In article <9364@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >I've often wondered about this. So many scientists seem to take the >dark matter for granted, but I've yet to see any clear reason for >postulating it other than a sort of religious dogma that the universe >will eventually recollapse. Is there really any stronger basis... It is very difficult to explain either the motions of stars in our galaxy or the motions of galaxies in clusters without assuming that there is quite a bit of extra mass present somewhere. Galactic velocities are too high for clusters to survive unless there is extra mass present to raise the clusters' escape velocities. The distribution of star velocities in our galaxy is grossly wrong if you assume no dark mass; it doesn't fall off nearly quickly enough as you go out from the center, and the only way to account for it is to assume considerable extra mass which is much more spread out than the visible mass. Now, whether this extra mass is enough to close the universe is a different question. As I understand it, one reason for suspecting an Omega of 1 (universe flat, precisely balanced between closed and open) is that the current Omega is within an order of magnitude or so of 1, and differences from 1 get magnified with time. That is, it must have been *very* close to 1 in the beginning to be this close now. This is considered a suspicious coincidence; pre-inflationary theories offer no reason for it. -- 1755 EST, Dec 14, 1972: human | Henry Spencer at U of Toronto Zoology exploration of space terminates| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
goldader@uhccux.uhcc.hawaii.edu (Jeff Goldader) (12/21/89)
In article <9364@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: > >So many scientists seem to take the >dark matter for granted, but I've yet to see any clear reason for >postulating it other than a sort of religious dogma that the universe >will eventually recollapse. Is there really any stronger basis for >believing that we only see ten percent of the universe, or are people >letting their aesthetics guide their modeling? Yes, there is in fact strong observational evidence for dark matter. For a long time, it was generally assumed by the astronomical community that the distribution of *mass* in galaxies was traced by the distribution of *light*; that is, where things are brighter, there is more mass than where things are relatively dim. However, when astronomers began to measure the rotation curves of galaxies, things became confused. The rotation curves of spiral galaxies, that is, a plot with distance from the nucleus on the x-axis and velocity on the y-axis, allow us to trace the REAL mass distribution, to some extent. Because of Kepler and Newton, if a galaxy were mostly a point mass in the nucleus, we'd expect the rotational velocity to fall off rapidly with distance from the nucleus. Instead, we find that the rotational velocities stay mostly constant out to large radii. This means there is some extra matter whose distribution is not traced by the light distribution, since the light distribution falls off exponentially the farther out you get in the disk and the higher you get above the disk. This matter is necessary to explain the extra gravitational force needed to keep the stuff at large radii moving as quickly as the stuff at smaller radii. The unseen matter is generally believed to be in the form of a "dark halo", roughly spherically symmetric, surrounding the galaxy. This evidence for dark matter is very persuasive, and no one has yet come up with a better explanation for the observed rotation curves. No one has been able to directly observe dark matter, although there are many theories as to its nature. Some say massive neutrinos, others say very heavy exotic particles (axions, wimps, etc.), many like the idea of lots of large planets (brown dwarfs), and one astronomer has jokingly suggested that the dark matter is nothing more than a very, very large number of basketballs. Physicists have calculated the properties of the odd particles (if they exist) and are devising detectors to sense them, astronomers are frantically searching for brown dwarfs, and lots of people play basketball, so we may learn something of the true nature of dark matter in the next few years. Jeff Goldader University of Hawaii goldader@uhccux.uhcc.hawaii.edu Institute for Astronomy "Bill, strange things are afoot at the Circle-K..." -Ted, "Bill and Ted's Excellent Adventure" Disclaimer: The University of Hawaii and the Institute for Astronomy neither support nor are in *any way* responsible for these opinions.
gary@dgcad.SV.DG.COM (Gary Bridgewater) (12/21/89)
What the article - in the San Jose Mercury News, anyway - said was that
CalTech scientists say they have observed large scale structures similar
to or suggesting cell/bubble boundaries. These structures seem to be made of
galaxies at extreme distances. The inference being that they are, therefore
very old - too old to have been formed in the time since the Big Bang. Or,
the time for the Big Bang is way, way off which would also pretty much
invalidates current theories.
The article also alludes to the cell-like structures' being similar to another
theory's predictions. (Hyper Inflation?)
There was an illustration which looked not at all like a picture - possibly an
artistic rendering.
More Science by Press Release?
--
Gary Bridgewater, Data General Corporation, Sunnyvale California
gary@proa.sv.dg.com or {amdahl,aeras,amdcad}!dgcad.SV.DG.COM!gary
Shaken but not stirred.