dark matter?

Question

scientists say that we only know about 5% of the matter in the universe. And the remaining 95% is unknown (i think also called dark matter)

So how do we know that 95% is remaining is its really unknown??

Answer 1

Actually you seem to be counting dark energy too. Out of all matter, dark matter makes up something like 80% and normal matter 20% or thereabouts. All matter put together makes up about 30% of the entire Universe, and the other 70% of THAT is dark energy.

The reason scientists know dark matter exists is because many galaxies are rotating fast enough that the centrifugal force should rip them apart. The only answer is that they are more massive than normal, luminous matter can account for, and that extra mass that holds them together is made up of dark matter. Recently, scientists even discovered a distant galaxy which is made up almost entirely of dark matter.

You can read more here:
http://en.wikipedia.org/wiki/Dark_matter

Answer 2

Dark matter is still greatly unknown. Scientist believe that there is a large amount of this unseen matter in the universe, but they still don't understand how much or how to see it.

We have no way of actually seeing it; x-ray, infrared, and other such images can't see it. They say that even with all the known and thought matter (dark and the seen matter) they still can't understand why the universe takes the form it does. With all the matter they believe to be in the universe they say that over time two lines, running parallel to each other would eventually run off from each other. But they don't, they continue to run parallel, and we can't explain why...yet.

The 5% and 95% is an estimate, a guess. Black matter is among the widely unknown things in the universe that we just don't understand yet.

Answer 3

This is very true. We only know about what we can observe or detect through our telescopes, microscope or particle accelerators! The dark matter as it is called, is undetectable because it weakly interacts with normal baryonic matter, like protons.
It is believed that this dark matter could be some exotic form of neutrinos that were created in the first micro-moments(1x10-43sec.) or less before normal interacting matter like electrons, neutrons and protons, and all other subatomic particles were created.
Dark matter could very well be eventually detectable if we can build a collider powerful enough to do the job, but for now, we can only observe the 'effects' of the gravity of dark matter on distant galaxies!

Answer 4

Good question!

As far as I know only about roughly 4% of the total energy density in the universe (as inferred from gravitational effects) can be seen directly. About 22% is thought to be composed of dark matter. The remaining 74% is thought to consist of dark energy, an even stranger component, distributed diffusely in space. Some hard-to-detect baryonic matter makes a contribution to dark matter, but constitutes only a small portion.Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics. It has been noted that the names "dark matter" and "dark energy" serve mainly as expressions of our ignorance, much as the marking of early maps with terra incognita.

Answer 5

I've thought about this one and maybe dark matter is all those left over planets from billions of solar systems that have come and gone throughout the age of the universe. Collectively there must be a HUGE amount of matter stored up in these trillions of dark, cool bodies drifting aimlessly in empty space, cast adrift by their dying suns and just about impossible to detect.
Plausible?

Answer 6

Dark matter is a little over 20% of the mass we estimate. It's unknown because it doesn't show up as anything luminous including infrared or microwave which all normal matter gives off.

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

Answer 7

Hmmmm... sounds like a rhetorical question...

Go hit the books slugger.