Author: Eelco de Groot
Date: 15:00:25 11/28/99
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On November 28, 1999 at 02:04:09, KarinsDad wrote:
>Eelco,
>
>Not to belabor this a lot, but the entire issue is one of 90 to 99% of "matter"
>is dark matter (according to the theorists). However, it only affects two known
>light phenomena in space out of dozens (and only one of these is via fairly
>direct gravitational effect, the other is pure mathematics based on a theory).
You are right, KarinsDad, I was using the term dark matter somewhat liberally.
The reason was that I was mentally including some things I had read about (see
Scientific American January 1999 for instance). There were some new
developments: observations of supernovae at far distances seem to indicate that
they are not moving away from us as fast as their distance, measured by their
specific brightness, would predict. In other words expansion in the early
universe was less rapid, but I admit the evidence is just one lightphenomenon
again. But if true that would be evidence for a type of antigravitation, or an
effect similar to what Einstein described as his "cosmological constant". This
could be seen as a form of "dark matter" that is actually a form of energy and
is present even in the vacuum of space.
That would give the following list:
Type Likely composition Main Evidence
Visible matter Ordinary matter Telescope observations
visible in stars etc.
Baryonic Ordinary matter Big bang nucleosynthesis
dark matter but too dim too see calculations,deuterium abundance
Nonbaryonic Various exotic Orbital speeds of stars and galaxies
dark matter particles too high
Cosmological Energy of empty Microwave background observations,
"dark matter" space Supernovae
The expansion of the universe might even be accelerating if this is true.
That would make life in the very, very distant future difficult.
>For example, scientists cannot find out if neutrinos have mass at all, but
>consider them to be a main candidate for some major fraction of dark matter.
>Does it not seem strange that scientists can measure the mass of a proton, but
>not the mass of a neutrino when neutrinos should outnumber (in quantity) normal
>protons by a billion to one? One would think that if there are so many of them,
>that the mass could be measured via quantity somehow.
That would probably due the fact that neutrinos are very hard to catch, I
believe I read somewhere they can fly through lightyears of lead without being
stopped. They interact very little with other matter so measurements are very
difficult. Another thing is that there are various forms of neutrinos, some even
harder to measure than others and they may even interchange.
>
>The entire thing is just an attempt to keep the big bang theory (or even the
>inflationary universe theory) alive (via mathematics) and to give people
>something to write their PhD thesis' on in physics. It is extremely difficult to
>remove a theory that held sway for such a long time. Look how long it took for
>the solid state theory to go away.
Maybe but there aren't many good candidates to replace it. But true, there are
many variants of the Big Bang theory that people test against observations.
>
>If you are interested, you can read the following web page on dark matter and
>mysticism. It will show you the level at which people will believe almost
>anything (even PhDs).
>
>http://www.thuntek.net/sumeria/cosmo/darkmatter.html
>
>Finally, consider the following. If scientists are merely deluded into thinking
>that the universe is really expanding (similar to how scientists one day thought
>the earth was flat or the center of the universe), then if the universe is not
>really expanding (just appears to be expanding), then dark matter (and the big
>bang theory) is a total sham based on a false premise. In our arrogance, could
>it be that we have created the 20th century version of the flat earth theory?
There would have to be another explanation for the universally observed
redshifts then and that would have to give rise to completely new theories
about that I think.
>
>KarinsDad :)
>
>PS. I haven't had a good off topic discusion since I became moderator. I felt
>like loosening my collar for a change. I used to post a few off topics a month.
>
>PSS. Although dark matter theories have been around for years, the quantity of
>dark matter is not only an estimate, but that estimate has been changing every
>time they come up with a different size of the universe
It is more the density of dark matter that is important. If it isn't high enough
the universe will keep expanding indefinitely
I think only the observable universe is important for the calculations. The size
depends on the calculated age of the universe for instance, estimates vary.
> (which probably doesn't have a set size, or at least not a measurable one). >This is what I meant by
>bleeding edge in my previous message. The theory changes everytime a
>technological advance puts a better telescope up.
That's why they put them up :)
Eelco
Sorry for late response, apart from the two of us is anybody still following
this by the way? :) Completely spaced out thread this.
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