Dark Matter

bogwalrus

I have been hearing about dark matter since i dunno what age but have never really understood what it actually is and its purpose. I know that it is quite mysterious so the questions i ask might not have answers but maybe some of you could share your ideas on what it is and so on........just so i could get some kind of picture in my head.....(my idea of dark matter now is basically a dark room of black dust floating about=(

So;

Is it a quantum particle?

Does it affect gravity and physical particles and in what way?

Does it belong to the periodic table or does it need it own special table?

Could dark matter be whats outside our universe and our space time is kind of like the air bubble in a bath of this stuff?

Any info would be great.

Boggy

Mellor

http://en.wikipedia.org/wiki/Dark_matter

I know wiki isn't 100% reliable, but the internet being home to the science buffs, the science pages, esp the large ones then to be quite up to speed and policed quite well.

That being said, im obviously going to be shot down when the dark matter wiki page is rife with errors

Professor_Fink

Hi Boggy,

I'll try to answer thlse questions as best I can.

bogwalrus wrote: »

Is it a quantum particle?

While we don't know exactly what dark matter is (although there are several suggestions) it almost definitely obeys quantum mechanics. Every particle we have ever discovered has been subject to quantum mechanics, and we have no reason to doubt that the same is true of dark matter.

bogwalrus wrote: »

Does it affect gravity and physical particles and in what way?

It effects other particles through a mutual gravitational force, just like everything else. Dark matter is unusual though in that it is not expected to interact with particles in any significant way through the other forces (electro-mag, weak and strong interactions).

bogwalrus wrote: »

Does it belong to the periodic table or does it need it own special table?

No, but then again neither do any other fundamental particles. Electrons, for example, don't belong on the periodic table, nor do quarks, etc., although atoms are composed of these.

bogwalrus wrote: »

Could dark matter be whats outside our universe and our space time is kind of like the air bubble in a bath of this stuff?

No. It's very definitely located within our universe. There is a very cool picture of the result of two galaxies colliding where you can infer the position of the dark matter (which has moved one as if there was no collision).

Hope this helps.

bogwalrus

Thanks very much for the above info. I did do some looking up on dark matter for ages and through some of the junk i came across what you were talking about (two galaxies colliding) its pretty fantastic.

I have a fair idea now on what it is but still curious to know its significance in our universe? Or does it need to be significant with all those strange qualities it has?

I keep finding these stupid sites on google that dont tell me anything about dark matter, they just keep repeating the words mysterious and "sometime in the future". really annoying

Thanks again

Sir Digby Chicken Caesar

There is a very cool picture of the result of two galaxies colliding where you can infer the position of the dark matter (which has moved one as if there was no collision).

ooh, pic?

Professor_Fink

Yes, there is a really good post on Cosmic Variance which includes and explains the pics: http://cosmicvariance.com/2006/08/21/dark-matter-exists/

Professor_Fink

bogwalrus wrote: »

I have a fair idea now on what it is but still curious to know its significance in our universe? Or does it need to be significant with all those strange qualities it has?

Dark matter does affect the other matter in the universe, but it's only noticable through gravitational effects. This makes it really hard to detect, despite the fact that it has very noticable results.

DublinWriter

I'm no expert on physics, but you think that will stop me?

The subject of Dark Matter arose when astro-physicists tried to model the gravitational behaviour of galaxies via computer.

Instead of seeing the nice spiral-arms and an obidient circling galaxy, the whole model galaxy would just 'fly-apart' as there wasn't enough physical mass to hold the whole show together under classical Newtonian physics.

Therefore, the astro-physicists had to infer that there was some other, previously unforeseen property holding the whole show together. So they christened this 'Dark Matter' although 'Unknown Matter' would have been a better name, as what 'Dark Matter' actually is is debatable.

Professor_Fink

DublinWriter wrote: »

The subject of Dark Matter arose when astro-physicists tried to model the gravitational behaviour of galaxies via computer.
...
Therefore, the astro-physicists had to infer that there was some other, previously unforeseen property holding the whole show together. So they christened this 'Dark Matter' although 'Unknown Matter' would have been a better name, as what 'Dark Matter' actually is is debatable.

Actually, cosmological models also need dark matter to match observations. It's called dark matter because we litterally can't see it. And it's pretty clear that it's something new.