Proof of Dark Matter?

Mick:
Spock mentioned that you don't have to be at the other side of the universe
to prove gravity is the same there as here.

Spock was mistaken. One can gather evidence of this and make an
inference, even a sufficiently strong inference that it is tantamount
to proof, but one cannot prove it. It is worth learning the relative
meanings of "evidence" and "proof." We are still learning about
gravity. See recent evidence that the expansion of the universe is
accelerating, e.g.

...Why can't we detect influences of "dark matter/energy" right
here with our magnificent men and their flying machines and
marigolds man in the moon [sic]?

If dark matter and/or dark energy exist, it is likely that we have not
detected them in our own little corner of the universe because a larger
quantity of DM/DE is required to have a measurable effect than is
present in our vicinity. Note that DM/DE are inferred by the observed
behaviour of galaxies, not of individual stars, planets, or running
dogs.

Davoud

--
usenet *at* davidillig dawt com

Spock mentioned that you don't have to be at the other side of the
universe
to prove gravity is the same there as here.

Spock was mistaken. One can gather evidence of this and make an
inference, even a sufficiently strong inference that it is tantamount
to proof, but one cannot prove it. It is worth learning the relative
meanings of "evidence" and "proof." We are still learning about
gravity. See recent evidence that the expansion of the universe is
accelerating, e.g.


Nein!..if I drop a rock here it will behave the same if I drop a rock 13
billion LY's away. Or if my anti-self drops a rock the same time I do 13
BLYs away it will behave the same. A tree does produce sound waves when it
falls in the forest. A needle and recording paper will record this event and
I will not hear it but read about it.

The pioneer space craft that has left the solar system is not anywhere near
its predicted position. There is some undetected influence that is acting.

The gravitation effect of unseen matter has been observed in galaxy
rotation and gallactic clusters for decades.


The gravitation effect of unseen matter has been theorized in galaxy
rotation and gallactic clusters for decades.


Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

If the naysayers don't like this theory,
the burden is on them to come up with another explanation for the
evidence.

I have no need for evidence, I merely choose not to believe this theory.

Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

If dark matter and/or dark energy exist, it is likely that we have not
detected them in our own little corner of the universe because a larger
quantity of DM/DE is required to have a measurable effect than is
present in our vicinity. Note that DM/DE are inferred by the observed
behaviour of galaxies, not of individual stars, planets, or running
dogs.

Amazing how it's all concentrated AWAY from here, isn't it??
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

Bill Foley wrote:
The gravitation effect of unseen matter has been theorized in galaxy
rotation and gallactic clusters for decades.

I'm sorry, I don't understand how you can claim that Vera Rubin's work
is theoretical and not observational.

Mojo
--
Morris Jones *
San Rafael, CA

http://www.whiteoaks.com

In message , Brian Tung writes
Alan Hall wrote:
I've read articles stating that there is scientific proof of the existence
of dark matter in the universe, as well as articles stating the contrary.
How can one prove the existence of what one cannot see?

Don't you essentially prove the existence of things you can't see all
the time? When you hear them but can't see them?

Or UV light which we can't see, but we can make detectors to do the job.

The straight answer is, I believe, by its gravitational interactions.
For example, galaxy clusters often consist of galaxies that are moving
too fast for gravity to hold them together--if the only mass in them
were the visible mass of the galaxies. In order for them to hold
together, some unseen mass must be present.

That and on a smaller scale the rotation curves of spiral galaxies which
do not follow the shape you would expect if all of the material in them
was luminous.

What would really be hard is to *disprove* the existence of dark matter.
How would one go about that?

You would be on very sticky ground. In the 80's a famous astrophysicist
was fond of teasing cosmologists by pointing out that exotic cold dark
matter could equally well be broken chair legs, sticks of rhubarb, old
biros, or dead planets (basically it could include just about anything
non-luminous that isn't dust).

That isn't quite the case now - normal matter seems to have been pretty
much ruled out of the frame by the most recent experiments. The hunt is
on to find some and/or determine what this exotic matter is made of.

Regards,
--
Martin Brown

I'm sorry, I don't understand how you can claim that Vera Rubin's work
is theoretical and not observational.


The work is based on observations, but the conclusions of this work are
necessarily theoretical. A LOT of things are being proposed to prop up
theories, some of which might be correct, but will remain unproven.

Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

There's Israeli physicist Moti Milogrom's theory that Newton's law of
gravity changes at a galactic scale. His "Modified Newtonian Dynamics"
theory also explains the movement of galaxies without resorting to
Dark Matter to explain things.

On Wed, 15 Oct 2003 13:41:24 -0700, "Bob May"
wrote:

There is some reason why the galaxies are spinning at a slower speed than
what the calculations would show for what can be seen. Either we can't see
the matter that is surrounding the galaxy or there is something else that is
slowing the speed way down. Thus, the title of Dark Matter for the matter
that we are presently unable to see.

Al Hall wrote:
There's Israeli physicist Moti Milogrom's theory that Newton's law of
gravity changes at a galactic scale. His "Modified Newtonian Dynamics"
theory also explains the movement of galaxies without resorting to
Dark Matter to explain things.

But it does resort to modifying a neat little law. Any particular
reason to prefer this resort over the other?

Brian Tung
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