Dark Matter?

Question

Though only theoretical, what is your take on it?

Answer 1

Dark Matter is an unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter.

SIMPLE ^_^

Answer 2

I'm disinclined to believe in Dark Matter.

The basic premise is: "we think there is more mass in galaxies than just the stars, and since we don't observe it, it must not interact much with regular matter."

To be fair, the evidence is getting better. Recently, a study of colliding galaxies showed that most of the mass of the galaxies passed through each other without interacting, which means most of the galactic mass isn't gas. That's one of the better observations in favor of Dark Matter.

Other observations are more dubious. For instance, light bending around galaxies is one "proof," but that is a complicated assertion because it combines two difficult calculations (how a dispersed massive object like a galaxy bends light, and how much mass it takes to match galactic rotation curves). The calculations are difficult because they require detailed numeric compuations involving General Relativity.

So I think the "proof" for Dark Matter, while getting better, is still a bit fuzzy.

Also, this sort of result is often disproven historically. For a long time, we thought light waves must move through an unseen "ether", until DeBroglie and others proved that light waves are probability oscillations, not real vibrations. Before that, chemists thought fire came from phlogiston (an unseen element in anything that burned), until we learned more about oxidation reactions. I know there are examples that go the other way, such as Dirac's theoretical prediction of antimatter before the experimental discovery, but Dark Matter strikes me as more of a stretch.

I believe that we are starting to make astronomical observations that are pushing the limits of current theories. Either we make up strange assumptions so the theories work ("over half the universe is non-interacting dark matter"), or the theories need some tweaking.

Answer 3

It is somewhat more than theoretical.
Something that we cannot otherwise detect exhibits gravitational attraction as has been observed to cause a 'gravitational lens` the way galaxies do.
We just can't seem to agree on what it is.
I hope to learn more in the time I've got left.