jr@bbncc5.UUCP (John Robinson) (01/29/86)
Feb. 86 Smithsonian has an update on the SETI progress. Seems now the search will involve JPL, NASA Ames and Stanford - a long way from suitcase SETI - and receivers that can scan 8.4 million channels at once. Can anyone explain simply how this feat is possible? A few days ago the Boston Globe (I think) had a piece about the 3-D mapping of the distribution of galaxies in the universe, using standard red-shift to get the radial dimension, for small patches of the sky. I am embarrassed to say I forget the name of the researcher, but he is at Texas. The first such map appears to show large near-spherical voids, as though large explosions emptied them of (visible) matter, or galaxy-formation proceeds on a shock-wave front emanating from a point in the center of the sphere. My question about this is does it shed light on, or call into question, the big bang? The article mentioned that the voids might reflect conditions just after the big bang, but more likely indicate evolution of the structure much later than the inhomogeneities were supposed to have crept in (my memory may have this wrong now). I was immediately struck with the possibility that maybe these voids are the result of "little bangs" that happen every few billion years - in other words a pulsating or steady-state universe - but such theories have been out of favor for a long time. Are there still serious cosmologists willing to entertain such a theory and the contortions necessary to explain red shift, and are they helped by this new vision of the structure of the universe? I think I have always had trouble accepting the notion that everything had to arise from a single point at a single time, though the evidence is supposed to be pretty overwhelming. /jr
ajs@hpfcla.UUCP (01/30/86)
> No, it's fairly well accepted that the "Big Bang" could not have been > a perfectly smooth event, since this would preclude galaxy formation. OK, here's a naive but hopefully reasonable question. Why can't inhomogeneities arise in a homogenous medium due to the Uncertainty Principle? I picture the Universe soon after the big bang as being a very dense soup of energy and particles (i.e. various kinds of waves). It's close and dense enough that quantum effects could make changes that would show up as huge inhomogeneities in a later expanded version. What's wrong with this innocent picture? Alan Silverstein
ethan@utastro.UUCP (Ethan Vishniac) (01/30/86)
In article <1379@bbncc5.UUCP>, jr@bbncc5.UUCP (John Robinson) writes: > > A few days ago the Boston Globe (I think) had a piece about the 3-D mapping of > the distribution of galaxies in the universe, using standard red-shift to get > the radial dimension, for small patches of the sky. I am embarrassed to say I > forget the name of the researcher, but he is at Texas. And well you might be embarassed, since this refers to the CFA redshift survey. [n.b. CFA= Harvard-Smithsonian Center For Astrophysics, which is in Cambridge, less than a mile from Fresh Pond]. > My question about this is > does it shed light on, or call into question, the big bang? No, it's fairly well accepted that the "Big Bang" could not have been a perfectly smooth event, since this would preclude galaxy formation. These inhomogeneities represent only ripples on the background of the Hubble expansion. Their origin is an interesting question, and these results may give us some interesting clues. -- "These are not the opinions Ethan Vishniac of the administration of {charm,ut-sally,ut-ngp,noao}!utastro!ethan the University of Texas, ethan@astro.UTEXAS.EDU but they are the opinions Department of Astronomy of your favorite deity, who University of Texas is in daily communication with me on this (and every other) topic.