"Dark Matter" Observed

An anonymous submitter writes: "The space news site Space Flight Now has an article about the first direct "observation" of so called dark matter. Galaxies appear to have more gravitation (mass) than we can currently observe. The theory of dark matter tries to explain this missing mass by the existence of massive bodies too faint to detect. These bodies include everything from dim stars to exotic particles called WIMPs. The previously dark matter, a dwarf star, was detected when it passed in front of a brighter blue star, creating a gravitational lens. It is thought that there are many more like it out there creating all that extra gravity, we just can't see them." Wired has another story; or see the European Space Agency's original article.

Fate of the Universe . . .

[JJ]

The fate of the universe is held by dark matter. Without dark matter, there is insufficient gravity to bind all matter together forever. If there is enough dark matter, with its attendant gravity, then eventually the universe will collapse back onto itself. Probably the end result of that would be another Big Bang.
What a pair of choices.

Um, if it's a star it can't be dark matter....

[LMCBoy]

The observed object is a dwarf star. It is luminous. This article should have been titled "Confirmation that one of the MACHO objects is not Dark Matter".

Re:Fate of the Universe . . .

[Jburkholder]

>Probably the end result of that would be another Big Bang.

so its possible that the universe has banged, expanded, collapsed in on itself and banged again multiple times already, right? (in fact, you can give yourself a serious headache by pondering the implications that this sequence of events is repeated infinitely, that there was never a 'first' time and there will never be a last).

Re:Fate of the Universe . . .

[nerdlyone]

I don't think the argument for dark matter has to do with the expansion/contraction of space-time (i.e., the universe). I think the argument for dark matter is based on gravitational models of galaxies and the idea that, according to current theory, most galaxies do not appear to have enough (visible) matter to create the gravitational force needed to hold that galaxy together. The expansion of the universe appears to be accelerating. See one article on this here. [astronomytoday.com]

Interesting Dark Matter Properties

[BadBlood]

If in fact dark matter is matter which exists gravitationally but will not interact w/the EM spectrum, wouldn't you be able to feel it with your hands but not see it? (Provided you have a small bit of it nearby)

Then, couldn't you somehow use this "material" for stealth purposes? Body armor making you invisible, etc. etc.

I find it amusing that as humans, we can only detect the existence of something if we can collide EM particles w/it (photons, etc.) We should rephrase a familiar motto to be "I can interact w/EM particles, therefore I exist." :)

Re:Interesting Dark Matter Properties

[Anonymous Coward]

If in fact dark matter is matter which exists gravitationally but will not interact w/the EM spectrum, wouldn't you be able to feel it with your hands but not see it? (Provided you have a small bit of it nearby)

No. If you touch an object, you don't feel it because it's interacting gravitationally with you. You feel it because its atoms are electromagnetically repelling with your atoms. If it didn't interact electromagnetically, it would pass right through you, just like neutrinos do. The mass of your body is way to small to be any hindrance as far as the gravitational interaction is concerned.

I find it amusing that as humans, we can only detect the existence of something if we can collide EM particles w/it (photons, etc.)

When LIGO goes online, we should be able to directly detect gravitational radiation, as opposed to just electromagnetic radiation. (Of course, we need electromagnetic radiation to read the instruments...)