Dark Matter? What is that Dark Matter?

I would like to to add a few words to a great input other people have already provided.

In Astronomy, as in all sciences, one can detect an object in one of two ways: either by observing it directly, or observing the effect that it has on other, more easily observed, objects.

It's always been known that there was matter in the night sky that we couldn't really directly see. When astronomers use telescopes, or even radio telescopes, they can only see objects which emit light or radio waves. Not all of the matter in the Universe does this - for instance, we wouldn't be able to see planets like our own, because they would be too dim to see.

All the mass of of all the planets in our solar system, though, is significantly less than one percent of the Sun's mass. So worrying about matter that didn't shine - non-luminous matter - wasn't of great concern.

The first evidence: Clusters of Galaxies The first evidence that there was a significant amount of matter that we couldn't readily see was in investigating clusters of galaxies, which are simply aggregates of a few hundred to a few thousand clusters otherwise isolated in space.

What is Dark matter? This still is an open question. There are many possibilities, and nobody really knows much about this yet. Here are a few of the many published suggestions, which are being currently hunted for by experimentalists all over the world. Remember, you need at least one baryonic candidate and one non-baryonic candidate to make everything work out, so there may be more than one correct choice among the possibilities given here.

The baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). The term "baryon" is derived from the Greek barys, meaning "heavy," as they are heavier than the other main groups of particles. http://en.wikipedia.org/wiki/Baryon

•Normal matter which has so far eluded our gaze, such as:

dark galaxies

brown dwarfs

planetary material (rock, dust, etc.)

•Massive Standard Model neutrinos. If any of the neutrinos are massive, then this could be the missing mass. On the other hand, if they are too heavy, as the purported 17 keV neutrino would have been, massive neutrinos create almost as many problems as they solve in this regard.

•Exotica (See the Particle Zoo FAQ entry for some details. http://math.ucr.edu/home/baez/physics/ParticleAndN...

Here are a wew references

What is the Universe Made Of? http://map.gsfc.nasa.gov/m_uni/uni_101matter.html

Cosmic Hide and Seek http://www.eclipse.net/~cmmiller/DM/

Dark Matter, Cosmology, and Large-Scale Structure of the Universe http://www.astro.queensu.ca/~dursi/dm-tutorial/dm1...

Experiment

Experiment with simulation of cluster of galaxies http://www.astro.queensu.ca/~dursi/dm-tutorial/clu...

What is dark matter? http://math.ucr.edu/home/baez/physics/Relativity/G...

Dark matter is pure invention of mathematician who try to explain why stars remain in galaxies because there is not enough mass to keep them together, like dark energy is the invention to explain why the universe expands when it had to stop long ago. These inventions arise because science still defend that the universe is gravitational, and is electrical neutral, even if data that came from Hubble and other space observatories, earth telescopes, etc constantly and almost daily prove that the gravitational theory can not explain these observations anymore.

But humans we are very resilient to change, and this would be a very fundamental change for all of us, too much to withstand. So, dark matter doesnt exist at all!!!

Nobody know for sure. We only now how much of it there is. Dark Matter as the name suggest cannot be seen. It only interacts with baryonic matter trough gravity and the weak nuclear force. We know it exist because the observed gravity of distant galaxies. If the galaxies were composed only of the matter we can see they wouldn't have enough gravity to hold them together.

Observing this effect tells us that dark matter makes between 90-99% of all matter, and around 25% of the universe's matter-energy balance.

Dark Matter is the 96% of the universe that we have yet to locate and identify.

We know its there because it creates gravity and gives enough gravity to hold all systems together (solar and galactic). We don't know what is made of, however. All we know is that it is matter made from particles other than molecules and atoms.

I personally think dark matter is a device to get the equations to work. Basically modern observations don't match theoretical calculations, so astrophysicists have to invent something astronomers can't see to make theory match reality. (Speaking from profound ignorance and cynicism.)

Dark matter is matter out in space that we cannot see from here on Earth. It doesn't reflect enough light in order for us to see it.

no one really knows what it is....all they know is that something is providing a gravitation pull on our galaxy but we cant see it or even tell if it even really there.....so, no, cant use it in any practical sense