Re: Could Dark Matter be here on earth?

On Sun, 24 May 2009 20:38:36 -0700, Eric Gisse wrote:

On May 24, 4:47 pm, Marvin the Martian <mar...@xxxxxxxxxxxx> wrote:
On Sun, 24 May 2009 13:27:52 -0700, Eric Gisse wrote:
On May 23, 12:43 pm, Marvin the Martian <mar...@xxxxxxxxxxxx> wrote:
On Sat, 23 May 2009 16:23:35 -0400, Yousuf Khan wrote:
HardySpicer wrote:
Could it be possible that dark matter is nearer to life than we
think? Could it be amongst us?

In theory, it should be all around us, and even going straight
through us.

If so it would be detectable surely - it has mass. Would we know
the difference between it and ordinary matter though?

No, Dark Matter is magical fairy dust bunny material. It'll never
be detected, I tell ya, never, never!

In theory, it only interacts with the gravitational force, so
forces like the electomagnetic force won't interact with it, and
therefore we'll never see it, feel it, smell it, etc.

Seriously, scientists have no idea what it is, and they're hoping
beyond hope that it can be made to interact with the electroweak
force at high enough energies so that it can be detected. This is
what they call a WIMP (Weakly Interacting Massive Particle), and
it's their last chance to prove it exists. Because if that's not
what Dark Matter is, then there's no way that they can prove it
exists experimentally, other than to stomp up and down and shout,
"but look at these pictures of gravitational lensing, that proves
it completely, trust us we got Ph.D's".  :-)

   Yousuf Khan

Let's follow the physics, and say that this dark matter 1) Didn't
interact with any electromagnetic forces. 2) It interacts with
gravity.

Then, it should easily gather into bodies like planets and stars.

Why?

There's no interaction, other than through gravitation, to shed
angular momentum to allow coalescence.

Plop a cloud of dark matter out yonder, with nothing but its' own
gravitational influences. Give it a Maxwellian speed distribution, or
any distribution.

What's gonna make it collapse? No electromagnetic interactions to
push things along, and the weak interaction (IF there is one, big IF)
is irrelevant. All that's there is gravitation.

Some of the particles will have velocities so similar that they will be
trapped in each other's potential well. This is the simple physics of
why fairly evenly distributed matter will condense to form stars and
planets.

...and if they don't have velocities similar enough? How do you get them
to come together?

I see... they can form clouds, but ... they can't get any denser than
that... why?

IF they create gravity, they are affected by gravity. WE should see
normal matter create a potential well which captures dark matter just as
regular matter is captured into orbits. So, the masses of planets and
stars should be increasing for no good reason at all.

We don't see that.

Gravity makes it collapse. IF the "dark matter" interacts via gravity
with ordinary matter, it must interact with itself by gravity as well.

Let's play "example". The nucleosynthesis of all of creation presumably
created a _shitton_ of neutrinos. They are light - somewhere on the
order of a fraction of an eV - and traveling relatively quickly.

Change of subject and attempt at bad analogy is noted.

Why haven't we seen any neutrino-based structures? Or anything that
could be construed as being formed by neutrinos?

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