what is dark matter ?

[AtomSplitter]

What exactly is dark matter? Is it even real or is it just made up? I read a small paragraph about it and would like to know more, if anyone could help it would be greatly appreciated. Thanks

[iNow]

The way our galaxies move in the universe implies that there should be more mass than we can see. We do calculations based on all of the mass we expect (based on what we can see), and it doesn't account for the way things move and interact.

 

So, the idea is that there must be some kind of mass out there which we just cannot see. We're still looking for it.

 

Now, if we later determine that there is no such thing as dark matter, then we will need to find out why our models work so well with nearly everything else, but don't account for the mass we expect based on observations. The tricky part is that the models DO work really well with everything else, so it seems very likely there is something out there we just can't yet see.

[AtomSplitter]

thank you for replying so quickly, i would also now like to know if scientists think they are any nearer to finding dark matter as something we could recognise, or is it a merely a theory that baffles the average peon like myself.

[insane_alien]

we have found dark matter, we can even map out its distribution. we just have no idea of what it actually is.

 

because it doesn't interact with anything other than gravity (and maybe the weak force) it is very very hard to observe, especially on a lab scale. this is primarily why we don't know what it is.

 

we call it dark because it doesn't interact with light. its just a label until we can analyse it better.

[AtomSplitter]

When you say that it does not interact with light , do you mean that it does not reflect light in a way so that we would see it in a certain colour?

[insane_alien]

no it doesn't reflect light, nor does it absorb it. or does anything with light. the photon will just pass it by as if it wasn't there.

[AtomSplitter]

So does that mean that there may be an opposite to light ( and not just the absence of)?

[insane_alien]

err, no. i don't know how you got that from what i said.

[AtomSplitter]

sorry, my brain was working faster then my fingers could dark matter interact with something we havent discovered yet? and i just wondered if light had an opposite (Other than darkness which is merely the absence of light) i didn't really have anything to do with it , sorry

[insane_alien]

its possible it interacts with something normal matter doesn't interact with but as such we have no evidence of it so far.

[AtomSplitter]

we have found dark matter, we can even map out its distribution. we just have no idea of what it actually is.QUOTE]

So having found it does it look like there are any practical applications for dark matter? i.e a way to explain otherwise un explained events?

[insane_alien]

nope none so far, perhaps once we find out what it is then we can work on that.

[AtomSplitter]

yes, well... not knowing what something is can be a minor setback... In your personal opinion, do you think that it may have any practical applications in the forseeable future?

[insane_alien]

yes, well... not knowing what something is can be a minor setback... In your personal opinion, do you think that it may have any practical applications in the forseeable future?

 

nope, not in the forseeable future.

[AtomSplitter]

ok, great, so at the moment, we know at best, almost nothing about it, we havent seen it, and it only exists in theory to make our models work well?

 

presumably dark matter must have a formula, does that mean we dont know ANY of it?

[insane_alien]

well, no, we have detected it. and detected it in enough detail to make a map of where it is. so it does have an effect.

 

dark matter is not made of atoms, it doesn't have a molecular formula.

[AtomSplitter]

iNow says above that it must theoretically have mass, therefore it must have a molecular formula right? or am i just confused?

[insane_alien]

it would only have a molecular formula if it were made of atoms. it is not made of atoms as atoms a really easy to detect even from very far away because they interact with light.

[AtomSplitter]

ok sorry, so how does something have a mass whilst not being made of atoms as we know them?

[insane_alien]

well there are other particles that have mass,

 

neutrons need not be part of an atom and they have mass, same with electrons and protons. quarks, gluons W and Z bosons neutrinos these all have mass and are not made of atoms. and i'm sure there are more. but i'm not too clued up on subatomic particles, i'm a chemistry man myself so i deal with atoms and stuff. and i can tell you right now that dark matter is not made of them.

[AtomSplitter]

i have read very little of antimatter myself, do you think that it could be composed of positrons, or antiprotons?

[insane_alien]

antimatter and dark matter are very different things. and we know antimatter is composed of positrons and anti-protons and so on. we have known this for quite a few decades now.

[iNow]

Go check out these, and follow the links in the explanation:

 

http://apod.nasa.gov/apod/ap030814.html

 

http://apod.nasa.gov/apod/ap060824.html

 

http://www.space.com/scienceastronomy/070108_mm_darkmatter_map.html

[AtomSplitter]

are there any simple tests for anitmatter?

[Klaynos]

are there any simple tests for anitmatter?

 

Hit it with normal matter if it's antimatter it'll anihilate giving off a pair (or more) photons...

 

There are other tests, finding the mass and charge for example...