Dark matter everywhere--so why not here (or is it?)

imspartacus · Oct 3, 2007

All this talk about dark matter and how much there is of it has me wondering: Is there dark matter in our local space (i.e. within some definable distance from our Sun). If so, is there any affect this matter has on the planetary orbits, or is its density so little that it has no descernable affect on the orbits of the planets?

falkor · Oct 3, 2007

Apparently, according to the theory, Dark Matter is all around us right now in this very room, but we just cannot see it! Sounds like a load of bull&%$#@! if you ask me...

shadow735 · Oct 3, 2007

I can understand dark matter existing in space but not in earth space. If it is dark and prevents us from seeing it due to its light absorbing properties or what ever makes it so we cant see it. I doubt it can exist on earth if it did wouldnt it look like a dark cloud of something in the light? its bright sun and a dark spotty cloud is hovering around that would be dark matter, Yes? <div class="Discussion_UserSignature"> </div>

pyoko · Oct 3, 2007

Dark matter does not absorb light. It is called dark because light passes through it. It should be called 'invisible matter', so people don't get confused. And it is quite possible for dark matter to be here in this very room on this planet. Dark matter interracts with matter only EXTREMELY weakly, so it is very hard to notice it on such a small level. We have to look at whole GALAXIES just to see it's effect on matter. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

shadow735 · Oct 3, 2007

is there any comparable measurement to the gravitational pull of dark matter compared to gravity of say a star. Is dark energy related to dark matter as well? <div class="Discussion_UserSignature"> </div>

pyoko · Oct 3, 2007

Only about 4% of the total energy density in the universe (as inferred from gravitational effects) can be seen directly. About 22% is thought to be composed of dark matter. The remaining 74% is thought to consist of dark energy. (wikipedia) As for dark energy: it is not actually related to dark matter. Only the name sounds similar. Dark energy is the proposed force that is ripping the universe apart. I know this doesn't actually explain a lot, but then again, there isn't much known about it in the first place. astronomers believe there is so much dark matter in the universe that it outnumbers normal matter by a ratio of perhaps 10 to 1. (space.com) You do the math. As you can see, even people in the know (not me) are still only guessing. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

mcbethcg · Oct 4, 2007

"Dark Matter" is just the phrase astronomers use for matter that is not yet observed that contributes to the overall gravity that is present in the universe. For example, the moon is easily observable and is obviously not dark matter. But if an identical twin of the moon existed a million light years from here in the gulf between galaxies, it would not be observed or observable, and would be considered "dark matter", at least until telescopy improved to the point that it was somehow observable.

vandivx · Oct 4, 2007

for all that is known about dark matter, it is everywhere but can only be discerned on at least galactic scales, possible later on it might be detected on smaller scales but not likely at all on the scale of the solar system I expect this view would bear discussion (because the physical cause behind DM is not known yet) but it seems more valid and reasonable than not vanDivX <div class="Discussion_UserSignature"> </div>

pyoko · Oct 4, 2007

The thing is... for all we know, there might actually be some Dark Matter IN the Moon. And around it. And inside your automatic pencil. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

imspartacus · Oct 4, 2007

Actually, this leads back to the last part of my original question: "If so, is there any affect this matter has on the planetary orbits, or is its density so little that it has no descernable affect on the orbits of the planets?" What I mean by that is: Does the calcuated gravity of any planet/moon preclude the existence of DM within or near that body? Similarly, could there be a cloud or....dare, I say "an ether" surrounding both objects that skews the calcuations in an inperceptible way--such that the true gavity of both objects are less. Of course, if dark matter is everywhere then does it really matter if it is always measured or never measured... I know--or think I know--that the idea of an ether has been discredited, but I still think these are interesting questions that will likely have far more interesting answers .

alokmohan · Oct 5, 2007

Discrepancy in gravitational atrraction led to the discovery.Suppose mass of a body is m.Ii will have gravity corresponding to Newtons law.But in center of galaxies gravitational attraction should be corresponing to mass of known stars.But these two things dont tally.So either Newtons law is wrong or there is matter we cannot see. This is dark matter.Dark energy is another thing.

ashish27 · Oct 5, 2007

Dark matter may be present beyond the Oort cloud in intersteller space. But that region of space is too far for us at the moment. Again I am only speculating.

pyoko · Oct 5, 2007

If Dark Matter is affecting the orbits of this system, then it is beyond current science to measure it. It would be too small to measure at such a level. Then again, our system should not have the galactic orbit it has now. More so, the 'dark galaxies' are prime examples. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

yevaud · Oct 5, 2007

Dark Matter, per both theory and observation, show it it dominate in/at the outer shells of Galaxies; scarce elsewhere (except, perhaps, the Intergalactic voids - which may explain the "Great Attractors" - a vast concentration of Dark Matter. Who knows?) <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

MeteorWayne · Oct 5, 2007

I'd like to point out that the reason it dominates "outside" galaxies has to do with the concentration of baryonic matter. In fact "dark matter" may be more concentrated toward the center of galxies (we just don't know, cause we can't see it except by it's gravitational effects, which are on large scales) but since the normal matter is concentrated near centers, the dark matter effect is overwhelmed. On the fringes, where there is less "light" matter, it becomes more obvious. that's how I understand it, anyway. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

yevaud · Oct 5, 2007

Well, that's all true, though a matter of conjecture currently. [Side thought - if so, how much of the Galactic Central Singularity is actually comprised of Dark Matter?] <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

MeteorWayne · Oct 5, 2007

Great question. Unfortunately, as you said, a matter of some conjecture at this point. Is dark matter confined in a Black hole? If it's a real particle or wave in our universe, then the answer should be yes. If it's an effect from a nearby brane or dimension....who knows??? Owww, my brain hurts now.... <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

yevaud · Oct 5, 2007

Quoth Star Trek: "Gentlemen, Temporal Mechanics makes my head hurt." <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

MeteorWayne · Oct 5, 2007

Who said that? I don't recall it. Owwww,,,, <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

R1 · Oct 8, 2007

has everyone read the article on dark matter at the sdc homepage yet? I found it interesting. I also read elsewhere so many things that it's almost confusing now: dark matter could possibly be a particle like an axion. It probably does not interact much, only very 'weakly'. It may be possible for a photon to Q-Mechanically turn into an axion and vice versa, in the presense of a strong magnetic field. (such as galactic fields ?) Light from distant supernovae may appear dimmer than it should be because a third of that distant light may have turned into axions which can pass through the earth undetected. For the most part I keep reading that axions are still only hypothetical, and their discovery would actually contradict something else important. Can someone explain these things further yet? or is this alsready on the wrong track to studying dark matter? <div class="Discussion_UserSignature"> </div>

olivebird111 · Oct 10, 2007

ya, its one of those things like viruses, you cant see it but they're there!

alokmohan · Oct 12, 2007

In 1998, two teams of astronomers discovered that the universe is speeding up, not slowing down under the pull of gravity. They resurrected Einstein's cosmological constant in the form of dark energy. While dark energy clearly exists and its effects are visible to astronomers, no one knows what causes it or whether it is truly constant over time. "The origin of dark energy is the biggest unsolved problem in astrophysics," said Wyithe. -- Investigating Dark Energy -- http://www.spaceref.com/news/viewpr.nl.html?pid=23777

Dark matter everywhere--so why not here (or is it?)

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