| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
24 Jun 2004 07:32:42 AM |
| Object: |
New light on dark energy... perfectly constant |
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
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| User: "JM Albuquerque" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 10:37:46 AM |
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"Sam Wormley" <swormley1@mchsi.com> escreveu na mensagem
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
(snip)
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
So... dark energy remains unchanged with time.
And what about dark energy distribution over the space volume?
Is the dark energy constant over all places of the Universe?
If not, I must presume that dark energy is not in equilibrium.
If not in equilibrium dark energy cannot be constant with time, unless it is
a solid like body.
If dark energy really exists, then I guess that one must start to talk about
a quintessence, because a "constant mathematical operator" for sure it is
not. It looks like that dark energy is a solid like quintessence.
The only thing we have for granted is that : "no matter what the results of
any experiment is, Einstein is always right because it cannot be wrong."
Notice that the argument present in the article against the quintessence
work both ways: ««if the dark energy density were to change with time, a big
crunch or big rip could not occur for at least 50 billion years for models
that allow such events.»» So, if dark energy density doesn't change with
time, how could the Universe be expanding and how could the Big Bang ever
occurred?
The article looks like more of the same bull...
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| User: "tj Frazir" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 11:23:22 PM |
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Energyhas no shape , so why ,,even as the universe expands , would it
not be constant ?
1919 AE
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| User: "Sam Wormley" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 11:22:42 AM |
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JM Albuquerque wrote:
"Sam Wormley" <swormley1@mchsi.com> escreveu na mensagem
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
(snip)
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
So... dark energy remains unchanged with time.
And what about dark energy distribution over the space volume?
Is the dark energy constant over all places of the Universe?
If not, I must presume that dark energy is not in equilibrium.
If not in equilibrium dark energy cannot be constant with time, unless it is
a solid like body.
If dark energy really exists, then I guess that one must start to talk about
a quintessence, because a "constant mathematical operator" for sure it is
not. It looks like that dark energy is a solid like quintessence.
The only thing we have for granted is that : "no matter what the results of
any experiment is, Einstein is always right because it cannot be wrong."
Notice that the argument present in the article against the quintessence
work both ways: ««if the dark energy density were to change with time, a big
crunch or big rip could not occur for at least 50 billion years for models
that allow such events.»» So, if dark energy density doesn't change with
time, how could the Universe be expanding and how could the Big Bang ever
occurred?
The article looks like more of the same bull...
Ref: http://arxiv.org/abs/astro-ph/0403292
Astrophysics, abstract
astro-ph/0403292
From: Max Tegmark [view email]
Date (v1): Thu, 11 Mar 2004 20:55:44 GMT (32kb)
Date (revised v2): Fri, 23 Apr 2004 01:55:03 GMT (32kb)
New dark energy constraints from supernovae, microwave background and galaxy
clustering
Authors: Yun Wang, Max Tegmark
Comments: Matches accepted PRL version. 4 pages, 2 figs. Software using
flux-averaging statistics to compute the likelihood of an arbitrary
dark energy model from SN 1a data available at this http URL
Using the spectacular new high redshift supernova observations from
the HST/GOODS program and previous supernova, CMB and galaxy
clustering data, we make the most accurate measurements to date of
the dark energy density rho_X as a function of cosmic time,
constraining it in a rather model-independent way, assuming a flat
universe. We find that Einstein's vanilla scenario where rho_X(z)
is constant remains consistent with these new tight constraints,
and that a Big Crunch or Big Rip is more than 50 gigayears away for
a broader class of models allowing such cataclysmic events. We
discuss popular pitfalls and hidden priors: parametrizing the
equation-of-state w_X(z) assumes positive dark energy density and
no Big Crunch, and the popular parametrization w_X(z)=w_0 +w_0' z
has nominally strong constraints from CMB merely because w_0' > 0
implies an unphysical exponential blow-up rho_X ~ e^{3 w_0' z}.
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:35:56 AM |
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JM Albuquerque wrote:
"Sam Wormley" <swormley1@mchsi.com> escreveu na mensagem
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
(snip)
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
So... dark energy remains unchanged with time.
And what about dark energy distribution over the space volume?
Is the dark energy constant over all places of the Universe?
Was not measured directly so far, AFAIK, but should be fairly
homogeneous. Otherwise it would show up in measurements of rotation
curves of galaxies, for example.
If not, I must presume that dark energy is not in equilibrium.
If not in equilibrium dark energy cannot be constant with time, unless it is
a solid like body.
I don't understand your logic here, sorry.
If dark energy really exists, then I guess that one must start to talk about
a quintessence, because a "constant mathematical operator" for sure it is
not. It looks like that dark energy is a solid like quintessence.
Huh??? Why do you think that quintessence is a solid???
The only thing we have for granted is that : "no matter what the results of
any experiment is, Einstein is always right because it cannot be wrong."
Nonsense.
Notice that the argument present in the article against the quintessence
work both ways: ««if the dark energy density were to change with time, a big
crunch or big rip could not occur for at least 50 billion years for models
that allow such events.»» So, if dark energy density doesn't change with
time, how could the Universe be expanding and how could the Big Bang ever
occurred?
Err, a change in the dark energy density is not required for the
expansion of the universe nor for the occurence of the BB. Why on earth
do you think so??? (hint: this does *not* follow from the quote you gave)
The article looks like more of the same bull...
Says the one who has misunderstood it.
Bye,
Bjoern
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| User: "Greysky" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 01:47:16 PM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive, that would account for at least
half of the repulsion. "Dark energy" is actually antimatter - whatever
excess force of repulsion that is left over is probably also due to the way
antimatter interacts with matter over cosmological distances. No big
mystery...
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
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| User: "Thomas Dent" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 08:18:54 AM |
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"Greysky" <greyskynospam@sbcglobal.net> wrote
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive, that would account for at least
half of the repulsion. "Dark energy" is actually antimatter - whatever
excess force of repulsion that is left over is probably also due to the way
antimatter interacts with matter over cosmological distances. No big
mystery...
Except how to get this from any self-consistent theory. In QFT
electron and antielectron come from the same field, so how can you
couple them to gravity oppositely?
And why doesn't all this large amount of antimatter (70% of the
universe) doesn't continually annihilate with normal matter in the
time-honored fashion
e+ + e- -> 2 gamma
and produce spectacular showers of gamma-rays everywhere? This is what
antimatter, i.e. antiprotons and positrons, do. There are extremely
stringent bounds on the amount of antimatter in the observable
Universe, it's less than a percent.
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| User: "Sam Wormley" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 03:39:53 PM |
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Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive,
It is not!
that would account for at least
half of the repulsion. "Dark energy" is actually antimatter
It is not!
- whatever
excess force of repulsion that is left over is probably also due to the way
antimatter interacts with matter over cosmological distances. No big
mystery...
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
.
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| User: "Greysky" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 12:21:21 AM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DB3C14.568A1B79@mchsi.com...
Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive,
It is not!
No proof one way or the other. We still need someone to observe how
antihydrogen falls in the Earth's gravity field.
that would account for at least
half of the repulsion. "Dark energy" is actually antimatter
It is not!
If antihydrogen falls up it may be, at least in part. The entire
cosmological structure of the universe will instantly need revising the day
some research scientist observes antihydrogen going the wrong way in an EM
nulled environment. I am already on record as saying it (antimatter) does
fall the wrong way - if I am right physics just might get exciting once
again.
- whatever
excess force of repulsion that is left over is probably also due to the
way
antimatter interacts with matter over cosmological distances. No big
mystery...
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
.
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| User: "Old Man" |
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| Title: Re: New light on dark energy... perfectly constant |
06 Aug 2004 03:32:32 PM |
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"Greysky" <greyskynospam@sbcglobal.net> wrote in message
news:lDOCc.5143$%P.3385@newssvr25.news.prodigy.com...
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DB3C14.568A1B79@mchsi.com...
Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made
of.
If Antimatter is gravitationally repulsive,
It is not!
No proof one way or the other. We still need someone to observe how
antihydrogen falls in the Earth's gravity field.
that would account for at least
half of the repulsion. "Dark energy" is actually antimatter
It is not!
If antihydrogen falls up it may be, at least in part. The entire
cosmological structure of the universe will instantly need revising the
day
some research scientist observes antihydrogen going the wrong way in an EM
nulled environment. I am already on record as saying it (antimatter) does
fall the wrong way - if I am right physics just might get exciting once
again.
Greysky is mundanely simplistic. If anti-matter is gravitationally
repulsive, what of negative matter ? Negative matter possesses
negative energy. We know that anti-matter isn't negative-matter
because electron-positron annihilation yields net positive energy,
2(m_e c^2). If negative-matter exists, then one can't exclude
the existence of anti-negative-matter.
Greysky has his GTR all wrong. Supposed dark-energy has
constant positive energy density, and the expansion of space
with time is due to a uniform distribution of positive energy
density which accrues from both matter and dark energy, but
matter density declines with the expansion.
If dark energy had negative energy density, space would
collapse, not expand.
[Old Man]
- whatever
excess force of repulsion that is left over is probably also due to
the
way
antimatter interacts with matter over cosmological distances. No big
mystery...
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
.
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:39:55 AM |
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Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DB3C14.568A1B79@mchsi.com...
Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive,
It is not!
No proof one way or the other.
But good theoretical arguments against this.
[snip]
that would account for at least
half of the repulsion. "Dark energy" is actually antimatter
It is not!
If antihydrogen falls up it may be, at least in part. The entire
cosmological structure of the universe will instantly need revising the day
some research scientist observes antihydrogen going the wrong way in an EM
nulled environment. I am already on record as saying it (antimatter) does
fall the wrong way - if I am right physics just might get exciting once
again.
If there is so much antimatter in the universe that it can explain the
repulsion, why don't we see annihilations all the time?
[snip]
Bye,
Bjoern
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| User: "tj Frazir" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 11:29:19 PM |
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How many years have I told you ??????????
HA HA HA ,,IM lauphing at you silly fuckers now
=95=BA=B5=83=B6=85=9C=A1=A1=A1
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:38:22 AM |
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Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive, that would account for at least
half of the repulsion.
1) Why should antimatter be repulsive?
2) If there is equally much antimatter in the universe as matter (as you
seem to imply), why don't be observe it? (annihilations, for example)
3) Why doesn't this show up in the rotation curves of galaxies?
"Dark energy" is actually antimatter
That contradicts points 2 and 3 above.
- whatever
excess force of repulsion that is left over is probably also due to the way
antimatter interacts with matter over cosmological distances.
"probably". Interesting.
No big mystery...
To the ones who know what they are talking about...
[snip]
Bye,
Bjoern
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| User: "Greysky" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 02:29:57 PM |
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"Bjoern Feuerbacher" <feuerbac@thphys.uni-heidelberg.de> wrote in message
news:cbgrqe$dje$2@news.urz.uni-heidelberg.de...
Greysky wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:40DAC9E6.FBED69E0@mchsi.com...
Ref: http://physicsweb.org/article/news/8/6/14
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
If Antimatter is gravitationally repulsive, that would account for at
least
half of the repulsion.
1) Why should antimatter be repulsive?
Why shouldn't it? If it were a cut and dry wrong assumption, there would not
be any need for physical experiments designed to observe how antimater
interacts in a gravity field - and although I don't think any are presently
being done, there are some observations using antihydrogen planned to be
done in the hopefully near future.
2) If there is equally much antimatter in the universe as matter (as you
seem to imply), why don't be observe it? (annihilations, for example)
You would need antimater to be mixed with matter for this to happen. If
antimatter were gravitationally repulsive, the only time in the history of
the universe there was a homogenous mix of matter and antimatter would have
been at the instant when mass coalesced from energy when the universe cooled
down enough for matter to form. In fact, most of the matter would have been
annihilated at this point, as you observed above, so what we have today are
just the tiny remnants of mass that managed to escape this process - matter
and antimater would have not only have been destroyed at this time in
cosmological history, but would also have been repelling away from each
other, so not all the mass would have been converted into gamma radiation.
We are living in the tiny bit of matter left over from this process...
3) Why doesn't this show up in the rotation curves of galaxies?
Because the antimatter is no longer where we are - it has been repelling
itself away from the matter portions of the universe ever since the
beginning.
"Dark energy" is actually antimatter
That contradicts points 2 and 3 above.
- whatever
excess force of repulsion that is left over is probably also due to the
way
antimatter interacts with matter over cosmological distances.
"probably". Interesting.
Yes - such a mechanism would have left an imprint on the large scale
structure of the univeerse, and what do we observe today - large voids where
the matter which forms galaxie clusters exist in 'shells' defining these
voids, like cosmic bubbles where we are living on the bubble film...
No big mystery...
To the ones who know what they are talking about...
Greysky
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| User: "Thomas Dent" |
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| Title: Re: New light on dark energy... "perfectly" constant |
25 Jun 2004 08:24:06 AM |
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Sam Wormley <swormley1@mchsi.com> wrote
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
See: http://physicsweb.org/article/news/8/6/14
The formulation "perfectly constant" is perfectly misleading. This
would only be warranted if the dark energy density could be measured
with *absolute accuracy*. Instead, what they find is that the energy
density is constant *to within about 10%*. It might still be changing
slowly. Physicsweb is obviously written by halfwits.
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| User: "Thomas Dent" |
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| Title: Re: New light on dark energy... perfectly constant |
28 Jun 2004 04:56:55 AM |
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Sam Wormley <swormley1@mchsi.com> wrote
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
See: http://physicsweb.org/article/news/8/6/14
The formulation "perfectly constant" is perfectly misleading. This
would only be warranted if the dark energy density could be measured
with absolute accuracy. Instead, what they find is that the energy
density is constant *to within about 10%*. It might still be changing
slowly. Physicsweb is obviously written by halfwits.
.
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| User: "tj Frazir" |
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| Title: Re: New light on dark energy... perfectly constant |
28 Jun 2004 09:19:10 AM |
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Constant as energy has no shape C.
Energy reacts with enegy at C.
Repulsive as the universe is expanding in spite of gravity.
Im 5 years ahead of you.
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| User: "MorituriMax" |
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| Title: Re: New light on dark energy... perfectly constant |
28 Jun 2004 10:09:09 AM |
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tj Frazir wrote:
Constant as energy has no shape C.
Energy reacts with enegy at C.
Repulsive as the universe is expanding in spite of gravity.
Im 5 years ahead of you.
And yet you still haven't graduated from High school.
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| User: "Danica" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 02:10:50 PM |
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Sam Wormley <swormley1@mchsi.com> wrote in message news:<40DAC9E6.FBED69E0@mchsi.com>...
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
I'm pretty sure that dark energy is not the same thing as the
cosmological constant. ie. expansion of spacetime itself is different
than a repulsive "energy" for lack of a better word.
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| User: "Sam Wormley" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 03:41:45 PM |
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Danica wrote:
Sam Wormley <swormley1@mchsi.com> wrote in message news:<40DAC9E6.FBED69E0@mchsi.com>...
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
I'm pretty sure that dark energy is not the same thing as the
cosmological constant.
Funny, the data shows that Dark Energy may characterized well by
Einstein's cosmological constant!
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| User: "JM Albuquerque" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 05:28:57 PM |
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"Sam Wormley" wrote:
Danica wrote:
I'm pretty sure that dark energy is not the same thing as the
cosmological constant.
Funny, the data shows that Dark Energy may characterized well by
Einstein's cosmological constant!
It could be funny, but I cannot see how.
They have assumed a flat universe and found that dark energy remains
unchanged. No surprise.
Ref: http://physicsweb.org/article/news/8/6/14
The problem is that GRT shows that the Universe is expanding. And so
Einstein created the cosmological constant to turn it flat again. Later he
said it was his greatest mistake and removed the cosmological constant,
because the universe seems to be expanding.
The fact is that I cannot see any relationship between the cosmological
constant and the article which claims that dark energy remains unchanged
with time.
If they have assumed a flat universe at first it means that cosmological
constant must be included, otherwise they have assumed wrong. So doing they
find that dark energy doesn't change with time. So what?
If dark energy means cosmological constant, then in fact dark energy must be
changing with time, because in fact GRT assumes the universe is expanding,
not flat.
This is funny article in fact.
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| User: "Sam Wormley" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 06:11:17 PM |
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JM Albuquerque wrote:
"Sam Wormley" wrote:
Danica wrote:
I'm pretty sure that dark energy is not the same thing as the
cosmological constant.
Funny, the data shows that Dark Energy may characterized well by
Einstein's cosmological constant!
It could be funny, but I cannot see how.
They have assumed a flat universe and found that dark energy remains
unchanged. No surprise.
Ref: http://physicsweb.org/article/news/8/6/14
The problem is that GRT shows that the Universe is expanding. And so
Einstein created the cosmological constant to turn it flat again. Later he
said it was his greatest mistake and removed the cosmological constant,
because the universe seems to be expanding.
The fact is that I cannot see any relationship between the cosmological
constant and the article which claims that dark energy remains unchanged
with time.
If they have assumed a flat universe at first it means that cosmological
constant must be included, otherwise they have assumed wrong. So doing they
find that dark energy doesn't change with time. So what?
If dark energy means cosmological constant, then in fact dark energy must be
changing with time, because in fact GRT assumes the universe is expanding,
not flat.
This is funny article in fact.
An expanding universe can exist with positive, negative and flat curvature
universes. We appear to be in a expanding flat universe. And one with a non
zero cosmological constant that just might model the accelerated expansion.
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:45:07 AM |
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JM Albuquerque wrote:
"Sam Wormley" wrote:
Danica wrote:
I'm pretty sure that dark energy is not the same thing as the
cosmological constant.
Funny, the data shows that Dark Energy may characterized well by
Einstein's cosmological constant!
It could be funny, but I cannot see how.
Well, do you know the Friedmann-Lemaitre equations?
They have assumed a flat universe and found that dark energy remains
unchanged. No surprise.
Huh??? Could you please explain your logic here to me???
In a flat universe, there *could* be a change of the dark energy without
any problem!
Ref: http://physicsweb.org/article/news/8/6/14
The problem is that GRT shows that the Universe is expanding.
Err, no, the observations show a red shift, and GRT *interprets* that
as an expansion.
And so
Einstein created the cosmological constant to turn it flat again.
Wrong. He invented it to make the universe *static*.
"flat" and "not expanding" is in no way synonymous!
Later he
said it was his greatest mistake and removed the cosmological constant,
because the universe seems to be expanding.
Right.
The fact is that I cannot see any relationship between the cosmological
constant and the article which claims that dark energy remains unchanged
with time.
Again: do you know the Friedmann-Lemaitre equations?
If they have assumed a flat universe at first it means that cosmological
constant must be included,
Vaguely right, if several other assumptions are included. Could you
please tell me how *you* arrived at this conclusion?
You seem to think that "flat universe" is equivalent to "cosmological
constant unequal zero". Hint: that is totally wrong.
otherwise they have assumed wrong. So doing they
find that dark energy doesn't change with time. So what?
You seem to have severe misconceptions about cosmology.
If dark energy means cosmological constant, then in fact dark energy must be
changing with time, because in fact GRT assumes the universe is expanding,
not flat.
Oh my goodness. You indeed think that "flat" implies "not expanding".
Yes, you really have no clue of cosmology.
Is the dark energy constant over all places of the Universe?
It should be.
Bye,
Bjoern
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| User: "JM Albuquerque" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 08:11:40 AM |
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"Bjoern Feuerbacher" wrote:
JM Albuquerque wrote:
It could be funny, but I cannot see how.
Well, do you know the Friedmann-Lemaitre equations?
No, I didn't know them, but now I have them right here:
http://scienceworld.wolfram.com/physics/Friedmann-LemaitreCosmologicalModel.
html
http://supernovae.in2p3.fr/~raux/these/these/node34.html
They have assumed a flat universe and found that dark energy remains
unchanged. No surprise.
Huh??? Could you please explain your logic here to me???
Well, if the word "flat" means "static" then the logic is obvious.
In a flat universe, there *could* be a change of the dark energy without
any problem!
Below you have implied that "flat" means "static".
If so, I cannot understand your statement.
Ref: http://physicsweb.org/article/news/8/6/14
The problem is that GRT shows that the Universe is expanding.
Err, no, the observations show a red shift, and GRT *interprets* that
as an expansion.
So, you are saying that GRT doesn't predict an expanding universe, nor the
Big-Bang.
That's strange, very strange, because as far as I know Einstein also
believed that the universe was static, hence he need the cosmological
constant. Then Hubble appears and Einstein claims his big error.
http://scienceworld.wolfram.com/physics/CosmologicalConstant.html
And so
Einstein created the cosmological constant to turn it flat again.
Wrong. He invented it to make the universe *static*.
"flat" and "not expanding" is in no way synonymous!
I cannot see any difference between "flat" and "static".
Can you please explain the difference between "static" and "flat"?
(snip)
If they have assumed a flat universe at first it means that cosmological
constant must be included,
Vaguely right, if several other assumptions are included. Could you
please tell me how *you* arrived at this conclusion?
You seem to think that "flat universe" is equivalent to "cosmological
constant unequal zero". Hint: that is totally wrong.
Why I'm wrong?
The universe is expanding (by observation).
Einstein created the cosmological constant to turn it static (your words)
So the conclusion is obvious.
Oh my goodness. You indeed think that "flat" implies "not expanding".
Right, I think that "flat" implies "not expanding".
Could you please explain what "flat" means.
I would be very grateful to learn something.
Yes, you really have no clue of cosmology.
I'm not alone.
Please explain what "flat universe" means.
Is the dark energy constant over all places of the Universe?
It should be.
If dark energy is constant over all places in the Universe, how do you plan
to use dark energy to explain the galaxy rotation curves?
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| User: "" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 02:15:55 PM |
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JM Albuquerque <jm.aREMOVEBIGLETTERS@sapo.pt> wrote:
I cannot see any difference between "flat" and "static".
Can you please explain the difference between "static" and "flat"?
In cosmology, "flat" usually means "spatially flat" -- that is, at a
fixed time, the spatial geometry of the Universe is (on the average)
flat. "Static" means "not changing in time." The two are independent:
one can have a static curved space, an expanding flat space, or any
other combination.
You may be confusing the idea of a *spatially* flat Universe with the
idea of a flat *spacetime*. A flat spacetime in GR is certainly
static -- it's just Minkowski space (or a piece of Minkowski space,
possibly with topological identifications). But that's not what
cosmologists mean by "flat."
Steve Carlip
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 09:43:42 AM |
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JM Albuquerque wrote:
"Bjoern Feuerbacher" wrote:
JM Albuquerque wrote:
It could be funny, but I cannot see how.
Well, do you know the Friedmann-Lemaitre equations?
No, I didn't know them, but now I have them right here:
http://scienceworld.wolfram.com/physics/Friedmann-LemaitreCosmologicalModel.
html
http://supernovae.in2p3.fr/~raux/these/these/node34.html
Nice. Now try to understand them.
I prefer your second link, since it shows the "k" which is important
for cosmology (apparently Wolfram simply said k=1 - without mentioning
that!).
They have assumed a flat universe and found that dark energy remains
unchanged. No surprise.
Huh??? Could you please explain your logic here to me???
Well, if the word "flat" means "static" then the logic is obvious.
Since the word "flat" does not mean "static", the logic is in no way
obvious.
In a flat universe, there *could* be a change of the dark energy without
any problem!
Below you have implied that "flat" means "static".
No, I have not. Why on earth do you think so??? I said the *opposite*!
If so, I cannot understand your statement.
Try reading again what I wrote.
Ref: http://physicsweb.org/article/news/8/6/14
The problem is that GRT shows that the Universe is expanding.
Err, no, the observations show a red shift, and GRT *interprets* that
as an expansion.
So, you are saying that GRT doesn't predict an expanding universe,
nor the Big-Bang.
No, that is *not* what I said. Try reading again what I wrote.
That's strange, very strange, because as far as I know Einstein also
believed that the universe was static, hence he need the cosmological
constant. Then Hubble appears and Einstein claims his big error.
http://scienceworld.wolfram.com/physics/CosmologicalConstant.html
Nothing of that is news to me.
And so
Einstein created the cosmological constant to turn it flat again.
Wrong. He invented it to make the universe *static*.
"flat" and "not expanding" is in no way synonymous!
I cannot see any difference between "flat" and "static".
Can you please explain the difference between "static" and "flat"?
"flat" refers to the geometry (i.e. k = 0 in the Friedmann-Lemaitre
equations; k=1 means a closed universe, k=-1 an open one).
"static" refers to the expansion (i.e. adot = 0; adot > 0 means
an expanding universe, adot < 0 a contracting).
What is *realized* in our universe is adot > 0 and (probably) k=0. But
that is by no means the only possibility.
A flat universe could be static, expanding or contracting.
A static universe could not be open, flat or closed.
If they have assumed a flat universe at first it means that cosmological
constant must be included,
Vaguely right, if several other assumptions are included. Could you
please tell me how *you* arrived at this conclusion?
You seem to think that "flat universe" is equivalent to "cosmological
constant unequal zero". Hint: that is totally wrong.
Why I'm wrong?
One could have a flat universe with a cosmological constant equal to
zero without any problems. One could also have a universe with a zero
cosmological constant which is flat. k = 0 and Lambda <> 0 are by no
means equivalent.
What is *realized* in our universe is Lambda <> 0 and (probably) k = 0.
But that is by no means the only possibility.
The universe is expanding (by observation).
Right.
Einstein created the cosmological constant to turn it static (your words)
Right. What you neglect to consider is that the universe is only static
if the cosmological constant has *one particular value*. For all other
values, it is either expanding or contracting.
So the conclusion is obvious.
No.
Oh my goodness. You indeed think that "flat" implies "not expanding".
Right, I think that "flat" implies "not expanding".
Well, then you are wrong. See above.
Could you please explain what "flat" means.
k = 0.
This means that the geometry of the universe is Euclidean, e.g. that
the sum of the angles in a triangle is always 180°.
I would be very grateful to learn something.
I hope you understand now better.
[snip]
Is the dark energy constant over all places of the Universe?
It should be.
If dark energy is constant over all places in the Universe, how do you plan
to use dark energy to explain the galaxy rotation curves?
I don't. Why on earth do you think I plan to do that???
For the rotation curves of galaxies, one uses dark *matter*, not dark
energy.
Try looking here:
<http://map.gsfc.nasa.gov/m_mm/mr_content.html>
Bye,
Bjoern
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:40:34 AM |
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Danica wrote:
Sam Wormley <swormley1@mchsi.com> wrote in message news:<40DAC9E6.FBED69E0@mchsi.com>...
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
I'm pretty sure that dark energy is not the same thing as the
cosmological constant. ie. expansion of spacetime itself is different
than a repulsive "energy" for lack of a better word.
The second part of your sentence had little to do with the first part,
hence the "i.e." made no sense.
Bye,
Bjoern
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| User: "Dan" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 02:32:13 PM |
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Sam Wormley <swormley1@mchsi.com> wrote in message news:<40DAC9E6.FBED69E0@mchsi.com>...
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
If you have ever read anything about Einstein, he actually added the
Cosmological Constant b/c he didn't like the implications his GR
equations gave for the evolution of the Universe. I personally
believe that GR ( IE dark energy) is an error in the equations of
motion. If you look at large clusters, there are inconsistancies with
GR. It works great for small scales, but you need to add the annoying
factor, which has no real physical signifigance. I think someone is
going to think outside the box and prove that dark-energy isn't really
there, just a problem with our limited understanding of the universe.
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| User: "Bjoern Feuerbacher" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 04:54:42 AM |
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Dan wrote:
Sam Wormley <swormley1@mchsi.com> wrote in message news:<40DAC9E6.FBED69E0@mchsi.com>...
Ref: http://physicsweb.org/article/news/8/6/14
Cosmologists in the US have made the most accurate measurements ever
of how dark energy varies with time -- and found that it remains
perfectly constant. Max Tegmark at the University of Pennsylvania and
Yun Wang at the University of Oklahoma performed numerical
simulations on observational data from supernovae, the cosmic
microwave background and galaxy clusters. The results, which agree
with Einstein?s predictions for a non-varying cosmological constant,
lend further support to the existence of dark energy (Phys. Rev.
Lett. 92 241302).
The acceleration of the universe is driven by a force that has
repulsive rather than attractive gravitational interactions. But
although this so-called "dark energy" is thought to account for
around two-thirds of the universe, no one knows what it is made of.
Possible explanations for dark energy include a "cosmological
constant" -- which remains unchanged with time -- that was first
predicted by Einstein in 1917.
See: http://physicsweb.org/article/news/8/6/14
If you have ever read anything about Einstein, he actually added the
Cosmological Constant b/c he didn't like the implications his GR
equations gave for the evolution of the Universe.
Yes. So what? It isn't important why Einstein invented it, it is
important if that constant makes mathematical sense in the equations.
And it does.
I personally
believe that GR ( IE dark energy) is an error in the equations of
motion.
Why?
If you look at large clusters, there are inconsistancies with
GR.
Those are in general explained by dark matter.
It works great for small scales, but you need to add the annoying
factor, which has no real physical signifigance.
It has physical significance. It can be interpreted as "vacuum energy".
Something like that is predicted by QFT (well, I freely admit that
QFT gets the magnitude totally wrong so far ;-) ).
I think someone is
going to think outside the box and prove that dark-energy isn't really
there, just a problem with our limited understanding of the universe.
I would say that the idea of dark energy itself is already "thinking
outside the box".
Bye,
Bjoern
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| User: "tj Frazir" |
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| Title: Re: New light on dark energy... perfectly constant |
24 Jun 2004 07:00:42 PM |
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Told ya so ,,,for years I told you the universe is energy under presure
expanding.
GLOAT : ))
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| User: "Danica" |
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| Title: Re: New light on dark energy... perfectly constant |
25 Jun 2004 12:43:57 PM |
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Oh my God,
Are any of you people actually physicists? Where do I start...
Firstly: antimatter is in no way related to dark matter or dark
energy. Antimatter is baryonic and therefore acts exactly like
regular matter including how it is affected by gravity.
Secondly: Someone said something about dark energy affecting the
rotation curves of galaxies - again you're mixing up dark matter
(whose existence was "proved" by galactic rotation curves) and dark
energy whose only affect on galaxies is whether or not they remain
bound or fly apart eventually, totally different.
Thirdly: Einstein introduced the cosmological constant because he
didn't think the universe was expanding but threw it out when Hubble
showed that the galaxies were in fact moving apart.
Fourthly: Dark energy is only the same thing as the vacuum IF its
equation of state proves to be the same ( vacuum equation of state is
P = w*rho where w = -1). Now, so far from experiments, w for dark
energy looks to be about -0.78 and the cosmologists theorize (and only
theorize because noone actually knows) that it is really -1 simply
because w not being 0 or infinity is extremely unlikely.
Lastly: Noone knows yet what dark matter is, they only know how it
affects things and therefore what some of its properties must be.
Noone knows what dark energy is either. Noone knows what caused
inflation but string theorists are trying to work on it right now.
So please stop stating as fact things that even the world's leading
scientists haven't proved and don't know okay?
-miss D.
I suggest some of you check out the FAQ page of Dr. Douglas Scott
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| User: "tj Frazir" |
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| Title: Re: New light me Gloating : )) |
24 Jun 2004 07:02:13 PM |
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Told ya so for years .
The universe is energy under presure expanding : ))
Gloating : ))))))
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