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newton1
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is that cosmological constant exist??
Originally posted by Newton1
why Einstein said this is his greatest mistake?
Originally posted by Nacho
Janus,
But is it really runaway expansion now, or do the observations just show that expansion is increasing at a low rate? If it just means expansion increasing at a low rate, that would suggest to me that it's something that had started recently, in terms of cosmic time.
Originally posted by Nacho
marcus,
Thanks for the links. Most of them are WAY over my head .. I took a quick look at them, and printed them out for study tonight.
Janus,
I'm more inclined to believe if there is now an increase in the rate of expansion, that it has been around since somewhere close to the BB.
If so, I'm under the impression that rate should have been increasing for billions of years, and would diverge from the number it started at .. sort of like a geometric progression. So that the effective rate the Universe is expanding now should be very-very hugh, not what the Hubble Constant shows.
Also, it seems to me our observations should show the Universe as a whole would not follow a Hubble Constant as a line, that is a graph of distance vs redshift should show a curve, not a straight line. That is because the light we are getting from galaxies billions of light years ago would have been emitted when the effective rate of expansion was lower. The light we get from closer galaxies was emitted when the effective expansion rate was higher. And charting redshift to distance should show that curve.
Originally posted by Janus
Basically, the observations show that the universe's rate of expansion has increased over time for as far back as we can see. ...
Originally posted by Nacho
Janus,
I'm more inclined to believe if there is now an increase in the rate of expansion, that it has been around since somewhere close to the BB.
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Originally posted by Janus
That's basically what the observations show.
Originally posted by marcus
this has me quite puzzled
everything I've read has the expansion rate decreasing for a long period of time (on the order of 10 billion years) because of
matter dominance
and only after that long period of decelerating expansion is the matter thinned-out enough so that the accelerating effect of the cosmological constant is seen
where is this other view of things written up?
Originally posted by Janus
Put it down to trying to rush off a post too quickly, too late at night.
...is there something familiar to compare this to.
Originally posted by Nacho
I understand the concept now .. the graph tells all. It was also included in the Lineweaver ph.0305179 article you linked, marcus.
It kinda conjures up the thought to me that Inflation is viewed backwards; that it is the normal operation of the Universe, and was stopped for a period of time by something after the BB, but is picking up steam again ...
Wonder if these observations will hold.
The cosmological constant is a term in Einstein's theory of general relativity that represents the energy density of empty space. It is often denoted by the Greek letter lambda (Λ) and is responsible for the acceleration of the expansion of the universe.
The cosmological constant was first introduced by Albert Einstein in 1917 as a way to counteract the effects of gravity and maintain a static universe. However, after the discovery of the expansion of the universe in the 1920s, Einstein abandoned the idea and referred to it as his "greatest blunder."
The strongest evidence for the existence of the cosmological constant comes from observations of distant supernovae, which have shown that the expansion of the universe is accelerating. This acceleration can be explained by the presence of a cosmological constant, as it would provide the necessary energy to drive the expansion.
The cosmological constant is often referred to as a constant, but it is not truly a constant value. It is a parameter that can vary depending on the state of the universe, and it is currently believed to have a small but non-zero value. This value is often referred to as the "dark energy density" of the universe.
If the cosmological constant does indeed exist, it has significant implications for our understanding of the universe. It would mean that the energy density of empty space is not zero, which goes against our current understanding of particle physics. It would also suggest that the expansion of the universe will continue to accelerate in the future, leading to a "heat death" scenario where the universe becomes cold and dark.