www.world-science.net/othernews/060821_darkmatter.htm

A colossal crash between two clusters of galaxies has wrenched apart “dark matter” and normal matter, proving the mysterious dark substance exists, astronomers say

The evidence looks pretty solid.

Just one small problem.

The Solar System has been whirling around the galaxy for nearly five billion years, yet it has never bumped into any dark matter.
(This stuff weighs MORE than ordinary matter remember.)

There is none in the Solar System.
No a measured ounce.
No satellite,even the Voyagers, ever felt it's pull.

Also double stars waltz around each other as though there were no dark matter within their stellar systems.

If it's up there.................. why ain't it down here ?

Weigh is a very crude word, especially in modern physics.
Dark Matter makes a large contribution to the Stress-Energy in our galaxy, but that does not mean it has a significant inertial presence.

"Weigh" is a perfectly good English word which has been used for 1500 years at least.

There is nothing "crude" about it.

If it weighs a tonne on earth then it's mass is a tonne.

EVERYBODY who speaks English knew what I meant.

"Planet"... "Weigh"... "Moon"... "Satellite"...where is this going to end....

Perhaps astronomers should branch out into Linguistics altogether (a place they clearly don't belong right now) and forget about Astronomy altogether.

"Weigh" is a perfectly good English word which has been used for 1500 years at least.

There is nothing "crude" about it.

If it weighs a tonne on earth then it's mass is a tonne.

EVERYBODY who speaks English knew what I meant.

"Planet"... "Weigh"... "Moon"... "Satellite"...where is this going to end....

Perhaps astronomers should branch out into Linguistics altogether (a place they clearly don't belong right now) and forget about Astronomy altogether.

What are you taking about?
Weigh doesn't really mean anything at the galactic scale.
Gravity is caused by a property of matter called Stress-Energy. Dark Matter has a signifcant amount of this quantity. However it doesn't have that great of an inertial presence within the galaxy.
Dark Matter doesn't really effect equations of motion within the galaxy.

Are you criticising Cosmology because it needs physical terminology more general than average English?

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I'm a long way from being an expert or even slightly knowledgable on this, but as far as I know, one of the main problems with dark matter is that no-one knows with any certainity what it is.

One theory is that dark matter is made up of WIMPs (weakly interacting massive particles), these particles don't react with normal* matter in any way meaningful to our senses, they can pass right thru' us everyday with our noticing (neutrinos do) i.e. can't be bumped into. WIMPs only interact gravitationally even then only on vast scales so their interaction would be too weak to be felt locally. So it could be up there and down here-but we just can't see it.

Another theory is that dark matter is made up on MACHO's (massive compact halo objects) which is basicly non-luminous matter e.g. black holes, brown dwarfs, planemos etc. The solar systems occupies such a infinitesimal space it in all likelihood will never bump into such items. In this case it could be up there and down here, but we just don't notice it as we see it everyday i.e. normal matter.

Weight= gravitional force acting on an object
Mass= the amount matter and energy the object is equivalent to
In everyday terms essentially the same, but in scientific terms not the same and so cannot be used interchangably in scientific discussions.

* In the WIMP theory it would be more correct to term dark matter as normal matter as it would be much more common than our so called normal matter.

Now I've got a headache :? and am going to lie down.

But dark matter DOES react with normal matter.

It deternines the rigid rotation of the visible part of individual galaxies.

It determines the structure of galaxy glusters through its GRAVITATIONAL pull.

It's GRAVITATIONAL force seems to exceed that of "visible" matter.

Again,the sound scientific question I posed is this:

Why is there none of it around this neck of the galactic woods ?

Why is there none of it around this neck of the galactic woods ?

There is nothing to say say there isn't any around. The interaction could be highly nonlinear and cumlative.
There are alot of systems where an evenly distribtued material only has global and not local effects.

Gravity is a lot more complicated in GR than it is in Newtonian Gravity.
Gravity is basically the result of 10 different properties of matter effecting 36 different properties of spacetime.
(A bad way of expressing the fact that it is a Tensor quantity effecting another Tensor quantity)
Newton's Gravity only keeps track of 1 of the matter properties and 4 of the spatial properties. So gravitational influence can include alot of stuff you wouldn't be familiar with from Newtonian Gravity.

Terminology can be important. Rather than this image proving the existance of dark matter, it fails to disprove it. Science does not seek to prove, but rather attempts to disprove. In failing to do so, it makes a hypothesis stronger.