Dark Matter

[China Doll]

Afternoon All,

Can anyone tell me what Dark Matter is please?

(Very brief question today for a change!)

Cheers
China xx

[Clanad]

Does the name Fritz Zwicky ring a bell... no? Well, in 1933 he (an astronomer, by the way) conducted some measurements of brightness of distant galaxies, but when he used a different method of computing their mass he came up with a significantly larger number. Over the years, scientists of all persuasions came to name this recognized difference as Dark Matter, since it can't actually be detected... yet. One site, (eclipse.net)explains..."Possibilities for dark matter range from tiny subatomic particles weighing 100,000 times less than an electron to black holes with masses millions of times that of the sun. The two main categories that scientists consider as possible candidates for dark matter have been dubbed MACHOs (Massive Astrophysical Compact Halo Objects), and WIMPs (Weakly Interacting Massive Particles." Suffice it to say, the investigation is ongoing, so simple answer to simple question is no one knows for sure...

[China Doll]

I think I understand... sort of! Cheers Clanad m'dear.

[kempie]

And because cosmologists couldn't reconcile the geometry of space with the predicted quantity of Dark Matter, let us introduce Dark Energy...

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

[China Doll]

Blimey.... thanks Kempie. Expect a question on Dark Energy in a few days time no doubt!

(You know I've actually had to set up a file in my favourites called 'Science' which has most of the links I get from everyone in here...I'm starting to get a back log! Why did my science classes at school never install this much interest?!)

[jake-the-peg]

The simple version is that when we add up all the matter that we believe is in the universe there isn't enough to account for the gravity we see.

There is therefore extra matter that we cannot see having an effect. We cannot see it so it's "dark"

The MACHOs Clanad refers to can be thought of as cold lumps of matter that we can't see because they don't shine like stars but for a number of reasons that theory is out of favour a bit.

WIMPS are an interesting possible solution but they mean that there is new type of particle that we don't know about - 1 team in Italy thinks it may have found them but nobody's yet managed to confirm.

This matter is "Dark" because we cannot see it, however
Dark energy is dark because frankly pretty much everybody is in the dark about it!

It's kind of the opposite of Dark matter in that we now see the Universe is not only expanding it's accelerating!

It shouldn't do that, it knows it shouldn't do that and it should stop right now!

Dark energy is the name given to whatever is driving this acceleration but right now this is one of the real big unanswered questions.

[China Doll]

I'm chuckling away here at your statement Jake regarding what it should or shoudn't do but I've just realised I'm not even sure if it's a laughing matter!

And I thought this would be a relatively simple question with a straight answer like 2+2=4. Ah well.... learn something new everyday and all that.

[mibn2cweus]

Seems that we are learning more and more as time goes on and our knowledge accumulates, the enormity of our ignorance.

The real tragedy evident with the revelation of our present ignorance is in reflecting on all the suffering we endured and the needless sacrifices we made to the gods we worshipped as a consequence of what we had not yet learned in the past.

Those with the courage to seek knowledge and the wisdom to impart understanding are unquestionably the heroic among us.

What relevance to your question on �Dark Matter� this has, I leave to you to evaluate. This is all I have to add to the exceptional answers that preceded mine.

[Loosehead]

One of the others will correct me but I seem to remember watching a documentary on this that concluded that 95% of the universe is dark matter/energy so what we can see and feel is on 5% of what there is, scary!

[China Doll]

Mibn... I think I have a fair idea where you're going with your answer but I'm not sure I see it as tragic exactly. Admittedly the warring aspect of religion is awful but I think a lot of knowledge has been saught as a result of it as well. And to be honest, everyone would have found something else to fight about anyway.

I'm not sure that science/pursuit for knowledge and religion are mutually exclusive either. I don't know enough to argue either side of that coin but from what I do understand there appears to be room for both. (Though I'm not sure that by religion I mean the traditional sense of the word.) Interesting thoughts though.

Loosehead - Fasinating thought. (Not sure about scary tho.)

[kempie]

The most recent WMAP observations are consistent with a Universe made up of 74% dark energy, 22% dark matter, and 4% ordinary matter.

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

[willowman]

China Doll - doesn't the answer to the question 2+2=? depend on whether we're buying or selling?
Old joke, sorry, couldn't resist.