Re: Dark matter/energy - is it real?


"Wayne Throop" <throopw@xxxxxxxxx> wrote in message
news:1144344469@xxxxxxxxxxxx

: I never saaid cooling was only by interaction with a star.

Neither does my question imply it, so your response is a non-sequitur.



Your question definitely implies it-

"Have you calculated how long it takes for a WIMP to cool by gravitational
interaction with a star, yet?"




: You are now degenerating into constructing strawmen for you to respond
to.

You claimed dark matter would clump, because it would be cooled by
gravitational interaction.



Why, yes, I did.

And you claim that it would not because it is too hot.

What a conundrum...

Oh, wait, maybe scientists have addressed this question-

http://astro.berkeley.edu/~mwhite/darkmatter/hdm.html

....

"One of the most revealing criteria as to whether the Universe is dominated
by CDM or HDM is the way that matter, in particular galaxies, are
distributed throughout the sky. HDM, as represented primarily by neutrinos,
does not account for the pattern of galaxies observed in the Universe.
Neutrinos, as aforementioned, would have emerged from the Big Bang with such
highly relativistic velocities (i.e. close to light speed) that they would
tend to smooth out any fluctuations in matter density as they streamed out
through the Universe. In the early Universe, the neutrino density was
enormous, and so most of the matter density could be accounted for by
neutrinos. Given their great speeds, neutrinos would tend to free stream out
of any overdense regions--that is, regions with densities greater than the
average density in the Universe. This process implies that density
fluctuations could appear only after the neutrinos slowed down considerably.
(i.e. As the Universe expanded, its temperature decreased, thereby resulting
in neutrino "cooling.")
"When coupled with the amount of power seen on large scale by the COBE
satellite, it turns out that a neutrino-dominated Universe would contain
insufficient power on small scales to be compatible with observations. This
rules out any purely HDM model of the Universe.

"When people discuss HDM nowadays they usually refer to it in the context of
"Mixed Dark Matter" of "Cold+Hot Dark Matter" models. In these models the
bulk of the dark matter is cold, but a tiny fraction is hot. Current
experiments limit the amount of "hot" dark matter in the universe to at most
a few percent, with the best fit being unmeasurably small. This is to be
compared to the cold dark matter component, which is around 1/3 of the total
energy in the universe."

..






> How do hot weakly-interacting particles cool down?
Gravitational interactions and gravity wave emissions.

So. Have you calculated how fast this would happen, or not?
No straw man, no degeneration, just a question which you are avoiding.


When respected physicists say things like "Current experiments limit the
amount of "hot" dark matter in the universe to at most a few percent, with
the best fit being unmeasurably small." I think it safe to assume that there
is sufficient cold dark matter to notice the gravitational effects of.



.

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