Dark Matter?

[mctonale]

found this @ http://www.thebigview.com/spacetime/questions.html

What is dark matter?

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 that supposedly makes up 90% to 99% of the mass of the universe is made of. 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. Its existence will decide the ultimate fate of the universe, because it depends on the universe's total mass, whether gravitation is strong enough act against the expansion of space and eventually induce a period of contraction, or whether space keeps on expanding forever.


Why try to explain something that we can't explain as invisible?

Could it not be that.

Given that space is infinite to the power of infinity.
Could space not contain an infinate number of galaxys?
All expanding.
And could Andromeda not be (by complete coincidence) just expanding in our direction?

And before you ask no i can't explain paragraph one.


This is more of a question than a theory.

[Thomas Knierim]

mctonale: Why try to explain something that we can't explain as invisible?

Because the phenomenon is quite literally 'invisible'. Dark matter does seem to be there -this can be inferred from its gravitational effect on visible matter- but it does not itself emit any light or radiation. I am glad that you quoted this excerpt, because it's a few years old now, and in the meantime there have been some important developments in cosmology, in particular the discovery of 'dark energy', which calls for a revision of this entry.

mctonale: Given that space is infinite to the power of infinity.

Infinite to the power of infinity does not make any mathematical sense. Either something is finite or it is infinite. Wouldn't you agree?

mctonale: Could space not contain an infinate number of galaxys?

Our universe contains a finite number of galaxies. Whether there are any other universes beyond ours -possibly an infinite number- we don't know. Personally, I think that nature abhors infinity. Just a metaphysical hunch.

mctonale: And could Andromeda not be (by complete coincidence) just expanding in our direction?

No, it's moving. But we can likewise say that our galaxy is moving towards the Andromeda galaxy, since it depends on the observer's frame of reference. The movement is a consequence of the gravitational attraction that the two galaxies exert on each other.

Cheers, Thomas

[todd]

Dark matter is still a concept.
We have to understand that our knowledge on universe is based on theories and models that will prove themselves false sooner or later if we try to expand their area of interest too much.
The black matter came out of the impossibility to explain the rate of the universe expansion, and other phenomena. This doesn't necessarily means that there is a hidden amount of matter we cannot see, but it can mean that matter may have a different existence or we do not yet understand matter properly.
What if a grain of sand is the peak of an Everest in another set of dimensions, changing the space around it according to physical characteristics we cannot observe?

[mctonale]

Infinite to the power of infinity

Just thought i would try to expand the concept of infinite space.

does not make any mathematical sense.

You are probrably right i expect it adds up to 0.0000000000000000000000000000 and so on.

[Thomas Knierim]

todd: The black matter came out of the impossibility to explain the rate of the universe expansion, and other phenomena.

The expansion of the universe itself does not suggest the existence of black matter. It is the other way round - the existence of dark matter would have certain influences on the expansion. If enough dark matter exists then we should expect the expansion to slow down at some point. However, you are right about dark matter being rather mysterious concept. Its existence is inferred from the observation of the relative and rotational velocities of stellar and interstellar objects, for example from the attraction of galaxies within a cluster. We think that we observe gravitational effects, and classical physics tells us that gravity is associated with matter, but we cannot see it, so we call it "dark matter".

Cheers, Thomas