Posted on 05/27/2003 4:15:08 PM PDT by RightWhale
Do We Live In A "Stop And Go" Universe?
Anyone who drives is familiar with the frustration of being caught in "stop and go" traffic, a phenomenon found in urban areas all over the world. Astronomers have found that stop-and-go traffic is even more widespread than that, affecting galaxies throughout the universe. Today at the 202nd meeting of the American Astronomical Society, Robert Kirshner (Harvard-Smithsonian Center for Astrophysics), on behalf of the international High-z Supernova Search Team led by Brian Schmidt (Mount Stromlo Observatory), presented evidence that the expanding universe slowed for billions of years before galaxies began accelerating, like cars that get past a bottleneck.
"Right now, the universe is speeding up, with galaxies zooming away from each other like Indy 500 racers hitting the gas when the green flag drops and the pace car gets out of their way. But we suspect that it wasn't always this way," said Kirshner.
John Tonry (University of Hawaii), principal investigator of the team for the new and collected previous observations reported on today, agreed. "We've been hoping to see this effect of slowing in the distant past. We saw evidence 5 years ago that the expansion of the universe currently is accelerating, but we didn't know for sure what it was doing 7 billion years ago. We are now seeing hints that, way back then, the universe was slowing down."
Astronomers discovered seven decades ago that the universe is expanding, with galaxies rushing away from each other in all directions. Physics suggested that the expansion, which began with the Big Bang, should slow down over time due to the combined gravitational pull from all matter in the cosmos.
Two groups-the High-z Supernova Search Team and the Supernova Cosmology Project-sought to study the universe's expansion by observing distant exploding stars called Type Ia supernovae. At their peak, these explosions are brighter than a billion stars like the Sun, enabling astronomers to see and study them across billions of light-years of space.
Five years ago, both teams announced that their studies of Type Ia supernovae showed the expansion of the universe is speeding up. The accelerating expansion pointed to the existence of an unexplained "dark energy" that permeates all of space.
Those initial findings were based on a few dozen supernovae. Now, the High-z Supernova Search Team has expanded that work to 79 distant and 140 nearby supernovae, some newly observed and some previously studied by observers worldwide. The additional data show with higher precision that the discovery of five years ago was correct and the universe currently is accelerating.
More importantly, Kirshner reported that Tonry and the High-z Supernova Search Team snagged four supernovae so distant that their light may well have left at a time when the universe was still slowing down, before dark energy began to dominate the gravitational pull of matter.
Future plans include doubling the number of well-observed Type Ia supernovae through an ambitious program at the National Science Foundation's Cerro-Tololo Inter-American Observatory. The ESSENCE project (standing for "Equation of State: SupErNovae trace Cosmic Expansion") seeks to make an accurate measurement of the cosmic parameter w, which provides clues about the nature of the dark energy. The parameter w is defined as p/rho, the ratio of the dark energy's pressure to its energy density.
"A better measurement of w will help answer the question: Is the dark energy Einstein's cosmological constant, or is it something else such as the so-called 'quintessence'?" said Chris Stubbs (University of Washington), one of the leaders of the ESSENCE project. "This is an important question considering that about 70 percent of the energy in the universe is dark energy, while only 30 percent is due to matter. Whatever dark energy is, it's the dominant stuff of the cosmos. We can't lose: No matter what we find, this will be interesting."
Currently, the value of w is known only to within a factor of 2. The ESSENCE project will do 10 times better, reducing the level of uncertainty to plus or minus 10 percent.
Adam Riess (Space Telescope Science Institute), as principal investigator for the Higher-z Supernova Search Team, is cooperating with the Great Observatories Origins Deep Survey (GOODS) to look for higher-redshift supernovae using the Hubble Space Telescope's Advanced Camera for Surveys (ACS). That program uses the ACS to find Type Ia supernovae at very large redshifts (and hence large distances), in order to look back even farther in time. The Higher-z project will have the best chance to determine whether the universe really was slowing down before cosmic acceleration kicked in.
The cosmological red shift assumption is indeed in question. The assumption is that the more distant the light source the faster it is receding from us. Could something else than mere velocity cause the observed shift in spectra? Also, this article throws a monkey wrench into the expansion of the universe model since it means the orderly distance measurements and therefore the timeline would be thrown off.
Vishnu's breathing? Maybe he just inhaled.
Uh Oh -- maybe he's going to wake up.....
Rush Hour????
Eh, 50 pages, but nice human interest portions e.g.
We began observing our 37 candidate objects at the Keck-II telescope on 1999 November 8. Our aim was to determine the nature of each object and to measure its redshift. Of these 37, two turned out to be active galactic nuclei at redshifts of 1.47 and 1.67; one was an M star and two were galaxies with H emission admitted because of mismatched R filters; five had disappeared, suggesting either that the discovery was well past maximum or the detection was spurious; four were judged to be Type II supernovae from spectra or blue color; two were too bright to be of interest for our purposes, I 21 mag in bright host galaxies, possibly nearby SN II, for which we did not spend time to get spectra; three were SN Ia with 0.3 < z < 0.7 which we chose not to follow; seven were faint candidates for which we did not have time to get spectra; and 11 were the candidate SN Ia which we chose to follow. These are shown in Figure 1.
The article only demonstrates that we don't know everything.
Again I'll point to Occam's Razor. The simplist explanation is usually the correct one.
The further away we look, the longer the wavelengths. What causes wavelengths to lengthen? The Doppler Effect, a known, proven and testable phenomenon.
Anything else and you might as well believe in Warp Drive.
THAT explains why my 3 day memorial day weekend only resulted in a day and a half of work! I woke up this morning thinking it was only Sunday!
Time to get our Senators involved to fix this crisis.......
The walls of the box we are expanding in.......
Read your link but feel their interpretation of 0.35+/-0.14 would be more accurately represented by >.0034/-+3/.543 factored to .937HO/.332
But hey, what do I know, I'm only a rockette scientist....
I blame Jimmy Carter. We didn't have these worries before he put us all on daylight savings time.
What a racket, rockette! Don't wreck it! But I don't reckon you will.
A. Raconteur
Mythical giants such as Isaac Asimov, Poul Anderson or Robert Heinlein wrote for Analog, the Magazine of Fantasy and Science Fiction, and Astounding, publications whose role today has been usurped by "respectable" publications drily titled "Science" or "Nature".
For sheer mind-blowing sweep across the eons, it doesn't get any better than articles like the one above, or this one: The Big Rip: New Theory Ends Universe by Shredding Everything.
Who knew that the geeks in lab coats possessed a sly sense of humor to rival Fredric Brown's or William Tenn's?
If our species survives the next 19 billion years (and there are serious doubts about this, given our Sun's projected fate) here are some signs that scientists of the future will want to look for.
- A billion years before the end, all galaxies will have receded so far and so fast from our own as to be erased from the sky, as in no longer visible.
- When the Milky Way begins to fly apart, there are 60 million years left.
- Planets in our solar system will start to wing away from the Sun three months before the end of time.
- When Earth explodes, the end is momentarily near.
At this point, there is still a short interval before atoms and even their nuclei break apart. "There's about 30 minutes left," Caldwell said, "But it's not quality time."
Is it good or bad that the eggheads at institutes of advanced research are developing disturbing scenarios that are stranger than fiction? Neither; it just is. We live today in an era that the visionaries dreamed about. The future is now. And I like the way my tax shekels are being spent.
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