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.
Just remember that you're standing on a planet
That's evolving
And revolving
At nine thousand miles an hour.
It's orbiting at nineteen miles a second,
so it's reckoned,
'Round the sun that is the source of all our power.
Now the sun, and you and me,
and all the stars that we can see,
Are moving at a million miles a day,
In the outer spiral arm,
at fourteen thousand miles an hour,
Of a galaxy we call the Milky Way.
Our galaxy itself contains a hundred million stars;
It's a hundred thousand light-years side to side;
It bulges in the middle
sixteen thousand light-years thick,
But out by us
it's just three thousand light-years wide.
We're thirty thousand light-years
From Galactic Central Point,
We go 'round every two hundred million years;
And our galaxy itself is one of millions of billions
In this amazing and expanding universe.
Our universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go,
that's the speed of light, you know,
Twelve million miles a minute
And that's the fastest speed there is.
So remember,
when you're feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there's intelligent life
Somewhere out in space,
'Cause there's bugger all down here on Earth!
-- Eric Idle
Sure, if you're prepared to postulate new physics and to give up energy conservation. You also have to explain why supernovae seem to have developed more slowly in the distant past.
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.
The most accurate estimates for the age of the universe do not depend on the cosmological distance ladder, but on the WMAP data. Furthermore, even if the distance ladder were all we had, a non-constant Hubble parameter wouldn't defeat the principle; it would simply reduce its accuracy. (The fact that the index of refraction of air changes over moderate distances doesn't change the fact that things look smaller as they get farther away.)
I know the Creator of the Universe and he said it won't be that bad.
Anything else and you might as well believe in Warp Drive.
The Doppler Shift may be observable fact, but when one observes a phenomenom that seems to be occuring at a certain distance that should have a specified Red Shift and DOES NOT, then one MUST start examining one's assumptions.
Several observations from the last few years are causing a serious re-thinking of the assumptions behind the velocity explanation for the so called Doppler Shift. The observation of objects that theory says only existed billions of years ago with red shift associated with much younger objects, the quantification of the red shift itself, the subject of this article, all force us to re-evaluate our assumptions.
Applying the Doppler Shift to astronomy involves the assumption that observed tonal changes (apparent wavelength) of sound from approaching and receeding sound sources is analogous to light from distant objects. Perhaps this is a falacious analogy.
The acceptance of the Doppler like velocity explanation for the observed red shift assumes that the conditions we experience in our local neighborhood are the same conditions elsewhere... which may be a very provincial view. For example, velocity is actually composed of TWO qualtities... distance and time. Perhaps it is TIME that is varying rather than distance! Our assumption that time proceeds at he same rate everywhere in the Universe is just that... an assumption. It may be that the farther away from any observational point, the passage of time is faster. We have no way of actually checking this assumption. An increase in the passage of time would distort both our measurement of velocity, distance, AND frequency.
Yeah and I'm gamma girl, red shifts are my specialty.
I can see the NY Times headline when it announces the Universe is collapsing on itself, "Universe to End. Homeless and Poor Most Affected".
Oh come on, think it o-o-ver.
I also recall reading that the "can't find it" anomaly gives rise to the possibility that dark energy is a signature of some (as yet) unknown property of space/time or gravity.
Have you heard of either of these and if so, do you have any updates for us?
IOW Wherever you go, there you are!
Seven decades ago some astronomers assumed the red shift observed in all directions was evidence of recessional velocity and posited that the receding sources of light must have originally proceeded from a single point in what they came to call the Big Bang. This idea, in spite of many contrary observational data in the decades since, has become the standard dogma, the theoretical glass slipper for which many observational toes have been crushed to conform or simply ignored.
No, it is NOT true. Objects HAVE been observed with a lower red shift that are farther away than other objects with much higher red shifts... and other objects have been discovered that have higher red shifts but are apparently in front of objects that have lower red shifts. It is these anomolies that are causing the re-evaluation of the Doppler Red Shift theory.
Just ONE thing that does not fit the theory means you must re-evaluate your data, you theory, or your assumptions.
It may be that the observers of these anomolous objects are mistaken in their observations or their calculations, or it is possible that the entire theory is incomplete or just wrong, or the assumptions you are basing your analysis upon are flawed.
If your simple, elegant theory does not cover the observed (and confirmed) events, then, regardless of William of Occam's razor, it is wrong. You start looking for a simpler, more elegant theory.
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