What is dark matter?

Question

It's been bugging a lot of people, and i want to know.

Answer 1

I don't know, but you get a dark matter gun in the game quake 4 and it is a very powerful piece of hand held artillery, albeit in a tragic, video game type way.

Answer 2

There seems to be a halo of mysterious invisible material engulfing galaxies, which is commonly referred to as dark matter. Scientists infer the existence of dark (=invisible) matter from the observation of its gravitational pull, which causes the stars in the outer regions of a galaxy to orbit faster than they would if there was only visible matter present. Another indication is that we see galaxies in our own local cluster moving towards each other.
The Andromeda galaxy -about 2.2 million light years away from the Milky Way- is speeding toward us at 200,000 miles per hour. This motion can only be explained by gravitational attraction, even though the mass we observe is not nearly great enough to exert that kind of pull. It follows there must be a large amount of unseen mass causing the gravitational pull -roughly equivalent to ten times the size of the Milky Way- lying between the two galaxies.
Astronomers have no idea what the dark matter is that supposedly makes up 23% of all matter in our universe. Black holes and massive neutrinos are two possible explanations. Dark matter must have played an important role in galaxy formation during the evolution of the cosmos. But, even taking into account all known and suspected black holes, there seems to be much more matter out there than we can presently see or extrapolate.
Have a nice day!!!!!!!!!!!!!!!

Answer 3

Dark matter is an invention by cosmologists to try to explain a problem that may not exist.
Galaxies,which are not satellite systems,rotate around the galactic center.
The outer arms rotate locked step with the galactic center.
Dark matter is supposed to keep the arms from flying away from the system by imposing a mass of invisible matter in and around the galaxy.
The galaxies were initially formed by gravity and Newton's laws but not like a solar system
At this time another force took over.
The engine that drives the galactic center and it's modification of space is what keeps and contracts the galaxy toward the center.

Answer 4

Dark matter - said to be the most abundant type of matter in the universe. It's called "dark" because, unlike other stella material such as stars or nebulae, it emits no light of its own, and can only be detected by its effect on its surroundings.

Things which have mass exert a gravitational pull; the greater the mass, the greater the pull. All this dark matter seems to have a great gravitational impact on its surroundings, hence the the theory that there's a lot of it.

Hope this helps a little.

Answer 5

The simplest way I can explain it is like this: Basically, when scientists put together a model of the universe, it all fell apart. And when something falls apart, it means that you need something else to hold it together again. The only problem was, everything that we know exists was put into the model, so whatever is holding the universe together is something we must not know about.

Scientists have no idea what this is, so they called this hypothetical substance "dark matter". Although it cannot be seen or felt, we know from tests that it must accomodate most of the universe, and works in conjunction with gravity (which, until recently, we believed to be the only force holding the universe together).

Answer 6

If you are really expecting a simple answer to this question I'm afraid you are going to be disappointed.

Dark matter is a mysterious hypothetical substance which has been postulated to explain the way the universe is behaving and evolving.

Its composition is unknown although lots of suggestions have been made and it does not emit or reflect an observable amount of radiation. Its presence has been inferred from the effects its gravity has on observable matter.

The total mass of this dark matter and its even stranger cousin "dark energy" is calculated to be far greater than the total mass of visible matter. The Universe is expanding rapidly and the total mass of all the visible components of the universe has insufficient gravitational force to slow it down,

If there is enough dark matter its gravitational force, when added to that of the visible component, may be enough to eventually stop the expansion but estimates of its total mass, and therefore its gravity, vary wildly. It is very difficult to estimate the mass of something which can't be seen or detected directly.

Answer 7

It's really a deus ex machina cocept so far.

The visible mass in the universe can't account for some observations, which require significantly more mass.

Mass = matter

Normal matter, however, should be "visible", i.e. emit/interact with electromagnetic radiation.

So, the missing mass got explained by "dark matter", which has gravity, but doesn't emit/interact with radiation (except for gravitational lensing, of course).

A deus ex machina approach, really, but it does seem to be able to consistantly explain observations (or did, until the point came where dark energy also had to be introduced). What it is, though, nobody knows - they're trying to track the stuff down at CERN and other research sites, but so far, to no avail.

Answer 8

No one knows for sure. They think it's the missing mass of the Universe.

Some think it could be renmants of the singularity mixed in with ordinary matter. Another possiblitity it is it carbon or other byproducts of stars thrust out. This is a new theory based on why stars seem to dim.

Dark matter seems to be mixed in with galactic matter in some galaxies.

No one knows for sure.

But it can be "not seen" that is to say when they take various "pictures" of the galaxies it shows up as something that is there but not seen.

Answer 9

Er you are correct in saying that question bugs even the best physicists. I was dead lucky in doing a bit of junior research for Steve Hawkin in Cambridge, and we "discussed" this business of our universes' dark matter.
You have to go into the depths of, as there is a finite amount of energy & matter whizzing about, there is a gap in the maths that covers the current expansion of our universe. Yjis can only be explained away by the notion of "dark matter" so called as we cannot look at it.
However, Steve reckons it is all to do with countless atoms of Hydrogen and Helium, the first two elements, wandering about, a bit lost for space to form anything.
This would account for the expanding state of affairs, although will ultimately be responsible for its' contraction to another "big bang"
We were looking at the fact that there is more than one universe, sounds a bit sci-fi, but proven.
So we have neighbours, existing in the same space.
Weird, but that means we are swapping dark matter.
I do not know the current exchange rate.
Two Euros per cubic kilometer ?
The mind boggles, but thanks for making me re-think it all.
Cheers,
Bob on the daft Boat.
Which County am I in ?
Oh, Bedfordshire apparantly.

Answer 10

As I understand it the space physicists have worked out that the visible material in the universe is not sufficient to account for some of the gravitational effects they have observed and they have come to the conclusion that there is material in the universe that is not visible to our instruments and this they call "dark matter"
I am be wrong but that is what I understand

Answer 11

It the simplest terms possible: nobody knows.

When you add up the total mass of the universe, you find that it is too light - the universe does not weigh enough for cosmologists sums to make sense.

The Dark Matter theory is a method for accounting for this 'missing weight' - it must be dark because we cannot see it, it must be super heavy to account for all the missing mass, and if it is 'something' (which it must be if weighs something), then it must be 'matter': ergo 'Dark Matter'.