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Milky Way May Have Dark Matter Satellite Galaxies

CmdrTaco posted more than 3 years ago | from the whirling-and-twirling dept.

Space 174

rubycodez writes "Berkeley astronomer Sukanya Chakrabarti has detected perturbations in the gases surrounding our Milky Way and concludes there is a satellite 'Galaxy X' 250,000 light years away that is mostly dark matter, but that may contain dwarf stars visible in infrared. She expects many more such dark matter satellites to the Milky Way to be discovered using her technique."

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Very old news (-1)

Anonymous Coward | more than 3 years ago | (#34906912)

This sounds like a sci-fi blockbuster (3, Funny)

roc97007 (608802) | more than 3 years ago | (#34906970)

"The creature from invisible Galaxy X"

Re:This sounds like a sci-fi blockbuster (-1)

Anonymous Coward | more than 3 years ago | (#34907054)

Did you see the dark first post above yours?

Re:This sounds like a sci-fi blockbuster (5, Interesting)

Black Parrot (19622) | more than 3 years ago | (#34907438)

"The creature from invisible Galaxy X"

There was an interesting musing by the author of a recent Scientific American about how dark matter may interact with its own kind by forces other than the ones that cause normal matter to interact with its own kind. According to the musing (which the author rejects), dark matter operating under such forces could form complex systems, maybe even an unseen parallel universe where "people" live lives like ours, as unaware of us as we are of them. All undetectable, except by their gravitational attraction on us.

Re:This sounds like a sci-fi blockbuster (1)

ron_ivi (607351) | more than 3 years ago | (#34908422)

It'd be weird if one of those dark planets zoomed through our solar system closely enough to have it's gravity affect the earth.

Imagine one zipping by and touching one of our oceans, and a bunch of the water'll & a few people, etc might be sucked up into that dark-gravity-source.

SF plot (2)

mangu (126918) | more than 3 years ago | (#34908534)

dark matter may interact with its own kind by forces other than the ones that cause normal matter to interact with its own kind. According to the musing (which the author rejects), dark matter operating under such forces could form complex systems, maybe even an unseen parallel universe where "people" live lives like ours, as unaware of us as we are of them. All undetectable, except by their gravitational attraction on us.

A plot for an SF story: every time the universe branches due to wavefunction collapse [wikipedia.org] a copy of the universe is created which still interacts with the universe through gravitation but not through the other forces.

Local effects of this are extremely difficult to measure, but they can be perceived as a fifth force [wikipedia.org] that appears, for instance in the Pioneer anomaly [wikipedia.org] .

I wish my writing skills were good enough to write this story...

Re:SF plot (1)

Anonymous Coward | more than 3 years ago | (#34908904)

What you're saying doesn't really make sense.

"Universe branches" => Many worlds interpretation of Quantum Mechanics

"Wavefunction collapse" => Copenhagen interpretation of Quantum Mechanics

These are two different ways of interpreting the same event. Whichever one you pick negates the other. If there is such a thing as wavefunction collapse, then there is only one universe and hence no branching. Likewise, if the universe branches, then there is no such thing as wavefunction collapse (the different outcomes simply occur in different universes).

Re:This sounds like a sci-fi blockbuster (0)

Anonymous Coward | more than 3 years ago | (#34909096)

You mean like in Hideaway by Alastair Reynolds?

Re:This sounds like a sci-fi blockbuster (1)

Anonymous Coward | more than 3 years ago | (#34907576)

Glad to see the photino birds making some progress.

Re:This sounds like a sci-fi blockbuster (0)

Anonymous Coward | more than 3 years ago | (#34909218)

I don't know about you, but I'm rooting for the Xeelee.

"May"???? (-1)

Anonymous Coward | more than 3 years ago | (#34907010)

Geez that's lame.

And Uranus might have Klingons around it, too.

Re:"May"???? (-1)

Anonymous Coward | more than 3 years ago | (#34907052)

Not if you wipe.

Jokes (1)

Stenchwarrior (1335051) | more than 3 years ago | (#34907018)

Cue the chocolate milk and dark chocolate jokes. I'm too busy, otherwise I'd think of some. C'mon /., don't let us down!

Re:Jokes (0)

Anonymous Coward | more than 3 years ago | (#34907204)

So... You're a fan of the Hershey Highway, eh?

Re:Jokes (0)

Stenchwarrior (1335051) | more than 3 years ago | (#34907426)

Nice!! Keep em coming!

Re:Jokes (0)

Anonymous Coward | more than 3 years ago | (#34907644)

I don't know about chocolate jokes, but:

Yo' momma so fat, she causes perturbations in the gases surrounding our galaxy!

Re:Jokes (2, Funny)

rubycodez (864176) | more than 3 years ago | (#34909018)

I prefer my women like dark matter: attractive, hard to catch, dark, and mysterious.

Dark matter vs black holes (3, Interesting)

Fractal Dice (696349) | more than 3 years ago | (#34907092)

How do you tell the difference between a blob of dark matter and a black hole? With all the small galaxies the Milky Way has swallowed over its lifetime, would it not be reasonable to find some relic black holes that have swung back out after being stripped of most of their surrounding gas/stars? Or, when "dark matter" is being talked about in this situation, is a black hole simply one of the possible candidates to supply the mystery mass?

Re:Dark matter vs black holes (2)

spottedkangaroo (451692) | more than 3 years ago | (#34907148)

Blackholes would prob ably get quite bright from time to time and (if nothing else) leave a halo of glowing matter behind. Also, dark matter can be quite spread out and turns into really huge blobs, rather than point masses. I imagine her technique looked for things like that. I don't think the article says anything really useful about the technique. Hopefully they cover it on Naked Astronomy.

Re:Dark matter vs black holes (3, Informative)

Colonel Korn (1258968) | more than 3 years ago | (#34907262)

How do you tell the difference between a blob of dark matter and a black hole? With all the small galaxies the Milky Way has swallowed over its lifetime, would it not be reasonable to find some relic black holes that have swung back out after being stripped of most of their surrounding gas/stars? Or, when "dark matter" is being talked about in this situation, is a black hole simply one of the possible candidates to supply the mystery mass?

I think we'd expect to see the kind of supermassive black hole that could be mistaken for a dwarf galaxy. The processes that form black holes of that size mean that there would probably still be a lot of material in the vicinity, if not actively accreting then still getting pulled around, compressed, and prompting star formation. Also, I think nearby galactic-sized black holes would probably make for some pretty wicked and obvious gravitational lensing.

Alternatively, the detected mass might be a large number of small black holes. I doubt it, but I'm not an astronomer. Luckily, further observation will give us answers.

Re:Dark matter vs black holes (1)

Black Parrot (19622) | more than 3 years ago | (#34907694)

I think we'd expect to see the kind of supermassive black hole that could be mistaken for a dwarf galaxy. The processes that form black holes of that size mean that there would probably still be a lot of material in the vicinity, if not actively accreting then still getting pulled around, compressed, and prompting star formation

Going out on a limb... I would expect dark matter to form "dark black holes" if you brought enough mass of it together in a small enough space.

For that matter, I would expect dark matter to get caught up into "normal" black holes, and normal matter into "dark" black holes, if you brought one kind of matter near the other kind of black hole.

I suspect a physicist would say it's impossible to distinguish a "normal" black hole from a "dark" black hole.

Re:Dark matter vs black holes (1)

marcosdumay (620877) | more than 3 years ago | (#34907940)

Well, black holes are always dark. No one shines.

Now, about distinguishing a galaxy from a black hole (the original question). On this situation it is possible. Since our galaxy (with gas everywhere) is overlaping the dark galaxy, if it was a black hole some gas would fall near it and make the usual X-ray emmisions.

Re:Dark matter vs black holes (1)

TexVex (669445) | more than 3 years ago | (#34908288)

Going out on a limb... I would expect dark matter to form "dark black holes" if you brought enough mass of it together in a small enough space.

I'm no expert, but here's what I think I know:

Dark matter only interacts gravitationally. Dark matter does not collide with matter, nor does it collide with other dark matter. This means it can't form clumps. No dark matter clumps means no dark matter gravity wells, meaning no dark matter black holes.

A galaxy's dark matter, then, is a diffuse cloud of invisible non-interacting particles in orbit around and through the galaxy itself. These particles have gravity of their own, and collectively they have a huge influence on the galaxy's field of gravity.

Now, obviously dark matter particles would be unable to escape a black hole just like anything else. However, the vast majority of dark matter will never interact with a black hole -- it will just orbit forever.

Re:Dark matter vs black holes (1)

killkillkill (884238) | more than 3 years ago | (#34908668)

Hopefully, further observation will give us answers.

There. Fixed that for you. Scientific method only tests and narrows in on truth, it doesn't guarantee the discovery of it.

Re:Dark matter vs black holes (4, Interesting)

Monkeedude1212 (1560403) | more than 3 years ago | (#34907378)

How do you tell the difference between a blob of dark matter and a black hole?

Gravitational pull is probably the biggest factor. A black hole simply gets so massive that at one point the gravitational pull is so strong that not even light can escape. It will have objects orbitting around it like planets orbit stars except at distances far greater than a star would normally hold.

Dark Matter, on the other hand, simply seems to have the gravitational pull of a regular star, but doesn't emit any light.

One thing to note is that when we observe things out there, it's not just a 2D plane we're observing but a great deal of depth is involved. When observing a black hole, the light behind the black hole will get sucked into the black hole if it happens to cross the event horizon. This will create a nice black circle in the sky. However dark matter, on the other hand, would not stop the light behind it from reaching our eyes, it might bend it a little but nothing too extreme.

Re:Dark matter vs black holes (2)

Fuseboy (414663) | more than 3 years ago | (#34907682)

That doesn't sound quite right - because of the inverse-squared falloff of gravity, once you're a certain distance away, black holes and stars aren't much different in how material orbits around them.

One difference is that that black holes often spew high-energy x-rays as infalling matter is crushed, whereas dark matter is - well - dark.

Re:Dark matter vs black holes (4, Informative)

Tim C (15259) | more than 3 years ago | (#34907978)

A black hole simply gets so massive that at one point the gravitational pull is so strong that not even light can escape.

Actually that's a good working definition of a black hole - if its gravity weren't that strong, it wouldn't be one.

It will have objects orbitting around it like planets orbit stars

Yes...

except at distances far greater than a star would normally hold.
 
...and no, not necessarily. That depends entirely upon the mass of the hole. The gravitational field of a black hole at a given distance is no different than that generated by a star of the same mass at the same distance; the difference is that the hole is so much smaller that you can get much closer to its centre. That vastly reduces the r in GM/(r^2), thus increasing the maximum gravity that can be experienced.

When observing a black hole, the light behind the black hole will get sucked into the black hole if it happens to cross the event horizon. This will create a nice black circle in the sky.

The situation is a little more complicated than that thanks to gravitational lensing, but essentially you're correct - a black hole will block light, while dark matter does not.

Re:Dark matter vs black holes (1)

Have Brain Will Rent (1031664) | more than 3 years ago | (#34908458)

Mmmmm, you are saying that a photon hitting a particle of dark matter simply passes through it with no chance of being absorbed?

Re:Dark matter vs black holes (2)

The_Wilschon (782534) | more than 3 years ago | (#34908834)

This is exactly what is meant by the word "dark" in "dark matter". It precisely means that its coupling to photons is zero (except, of course, for higher order loop effects in the Feynman diagrams, but those would be incredibly, perhaps immeasurably, small).

Re:Dark matter vs black holes (1)

c++0xFF (1758032) | more than 3 years ago | (#34908908)

To be fair, there's two definitions of dark matter. One is as you said -- matter that has little or no interaction with photons.

The other is baryonic dark matter [wikipedia.org] which is simply normal matter that isn't emitting many photons, so we don't see it. And if we can't see it, we can't include it in our tally of mass.

But, it seems that baryonic dark matter can only account for a small percentage of the total dark matter in the universe, so it's usually ignored.

Re:Dark matter vs black holes (1)

Have Brain Will Rent (1031664) | more than 3 years ago | (#34909438)

Umm he didn't say "little or no interaction" with photons - he said "It precisely means that its coupling to photons is zero", no interaction with photons. Big difference.

Re:Dark matter vs black holes (0)

Anonymous Coward | more than 3 years ago | (#34909342)

Not necessarily. By "dark" it is usually meant matter that doesn't shine. Some of it might be (or some most likely is) baryonic dark matter.

A rogue planet, or a rogue planetary system without a central star would classify as dark matter. That is, matter that is not accounted for when adding up the matter in the visible stars. Yes, a lot of dark matter is believed to be non-baryonic, but not all of it.

A rogue planet, floating free of any galaxies would be (a) bigger than a black hole of the same weight and (b) absorb light and emit harder-to-detect infrared black body radiation. So yes, it would look like a rogue black hole from where we're standing.

Re:Dark matter vs black holes (1)

Have Brain Will Rent (1031664) | more than 3 years ago | (#34909366)

Ummm well I hate to rely upon Wikipedia as the cite for an opposing opinion but....

http://en.wikipedia.org/wiki/Dark_matter [wikipedia.org]

Don't stop at the first paragraph or two...

The largest part of dark matter, which does not interact with electromagnetic radiation, is not only "dark" but also, by definition, utterly transparent.

Which implies there is a part that does interact with electromagnetic radiation - photons.

nonbaryonic dark matter includes neutrinos

And of course neutrinos can interact with photons and baryonic matter... just not frequently. I can't remember the number of miles of lead a neutrino can pass through without it likely being stopped bit it isn't infinite or even really very big.

Some hard-to-detect baryonic matter, such as MACHOs and some forms of gas, is believed to make a contribution to the overall dark matter content but would constitute only a small portion.

Small does not equal zero.

At present, the most common view is that dark matter is primarily non-baryonic, made of one or more elementary particles other than the usual electrons, protons, neutrons, and known neutrinos. The most commonly proposed particles are axions, sterile neutrinos, and WIMPs (Weakly Interacting Massive Particles, including neutralinos).

Most common does not mean all. Primarily does not equal entirely. WIMPs [ re cold dark matter] interact with baryonic matter through the weak force. WILPs [re hot dark matter], e.g. neutrinos, interact with baryonic matter through the weak force and trigger an event through a head on collision with a nucleus. Colliding implies interaction.

The DAMA/NaI experiment and its successor DAMA/LIBRA have claimed to directly detect dark matter passing through the Earth, ......

Direct detection implies interaction,

Experiments with the Large Hadron Collider (LHC) may be able to detect WIMPs... these experiments could show that WIMPs can be created

Created by baryonic matter and/or the known forces other than gravity...implying interaction although possibly only in one direction.

And finally, describing other efforts to detect dark matter...

Both of these detectors are capable of distinguishing background particles which scatter off electrons, from dark matter particles which scatter off nuclei.

Scattering off nuclei sounds like interaction with baryonic matter to me.

Re:Dark matter vs black holes (3, Informative)

c++0xFF (1758032) | more than 3 years ago | (#34908580)

Say what?

First off, the GPP has a decent question. The largest supermassive black holes are on the order of 10^9 solar masses, about the same mass as what was calculated for this satellite galaxy. So, I suppose it's at least plausible that it's a single black hole, if unlikely.

But remember and repeat after me: a black hole has no more gravity than any other object of the same mass. As long as you stay away from the event horizon, that is. You need to rethink your first paragraph with that in mind.

So, how would we tell the difference? Well, an X-ray source from the same location would be a good clue that it's a black hole, which says that it's feeding off of something. You should also be able to tell from the gravitational lensing -- dark matter is incredibly diffuse compared to a black hole. It would still bend light, but not quite in the same way, especially considering the distances involved.

But what about a black circle in the sky? Well, the even horizon for such a black hole has the same diameter as the orbit of Pluto, if I remember right. Detectable, maybe, under the right conditions (but not by Hubble -- you'd need something with about 20x better resolution ... if I did the math right, which I probably didn't). But we have to capture it overlapping with some other body, such as a background galaxy. By then you'd be better off looking at the lensing effect, anyway. Here [wikimedia.org] is a classic simulation of what I'm talking about.

Re:Dark matter vs black holes (2)

bcrowell (177657) | more than 3 years ago | (#34909046)

How do you tell the difference between a blob of dark matter and a black hole?

Gravitational pull is probably the biggest factor. A black hole simply gets so massive that at one point the gravitational pull is so strong that not even light can escape. It will have objects orbitting around it like planets orbit stars except at distances far greater than a star would normally hold.

Dark Matter, on the other hand, simply seems to have the gravitational pull of a regular star, but doesn't emit any light.

No, this is completely wrong. A black hole doesn't have stronger gravity than the star or stars that it formed out of.

One thing to note is that when we observe things out there, it's not just a 2D plane we're observing but a great deal of depth is involved. When observing a black hole, the light behind the black hole will get sucked into the black hole if it happens to cross the event horizon. This will create a nice black circle in the sky. However dark matter, on the other hand, would not stop the light behind it from reaching our eyes, it might bend it a little but nothing too extreme.

This is also wrong. Gravitational lensing occurs both for black holes and for other objects that aren't black holes. The black hole in the sky that you're describing is not what is predicted for a black hole either.

For anyone who wants to see the actual paper, here it is: http://xxx.lanl.gov/abs/1101.0815 [lanl.gov]

Re:Dark matter vs black holes (2)

vlm (69642) | more than 3 years ago | (#34907384)

How do you tell the difference between a blob of dark matter and a black hole?

In theory due to hawking radiation etc black holes temperature increases over time as it shinks (weird but true). Both probably live around the cosmic microwave blackbody limit.

A big array of dark matter would be a hair above 2.7 kelvin and tending to thermalize down to 2.7, but a big array of black holes would tend to be a hair above 2.7 kelvin and tend to increase over time.

So basically something cold that tends to stay cold is probably dark matter and something that seems to be warming up more than reasonable is probably a black hole.

Given a long enough time for thermal like diffusion, a mixture of them might behave like stellar formation, and the higher temperature of the black holes would tend to push dark matter away. So in a density map of old empty space, look for a "bulls eye" to find the black holes.

There are some scalability problems here.

Re:Dark matter vs black holes (0)

Anonymous Coward | more than 3 years ago | (#34907416)

As I understand it "dark matter" is in modern usage is a term for a fairly poorly understood class of stuff that has mass but otherwise doesn't interact with anything (except possibly itself). If they suspected a black hole, they would not have said "dark matter".

There are ways of distinguishing between "dark matter" and reasonably well understood objects like black holes. For one thing black holes generally are surrounded by really bright accretion discs (there are pictures of these), and tend to be a lot of mass in one place. "dark matter" on the other hand tends to be highly diffuse (it's effects are only measurable on a much larger scale than that of a single star), and is not detectable except by it's gravitational effects. This why you hear about "dark matter galaxies" but not "dark matter stars".

One example of the difference between dark matter and "normal" matter is while normal matter tends to be denser at the center of a galaxy, dark matter is not any more common at the center than out near the edge of a galaxy. that observation has led some to speculate that dark matter may self annihilate (like what happens to mater + anti-matter, but dark matter does it with itself rather than with an anti-dark matter).

Re:Dark matter vs black holes (1)

Locke2005 (849178) | more than 3 years ago | (#34907464)

A black hole would occlude light from behind it, making it detectable by a circular absense of light as it travels across the sky. Apparently a blob of "dark matter" either does not absorb light or has such a small diameter that it does not detectably occlude light. But if the dark matter was a point source of gravity, wouldn't we still see some gravitational lensing? It appears dark matter would have to be much less dense than a black hole. But then, I'm not astrophysicist.

Re:Dark matter vs black holes (0)

Anonymous Coward | more than 3 years ago | (#34907708)

A black hole would occlude light from behind it, making it detectable by a circular absense of light as it travels across the sky.

Uh, with current technology we can't detect a circular black disk a few km in diameter when it's halfway across the galaxy. When you use the phrase "making it detectable by", what follows should be something feasible.

Re:Dark matter vs black holes (1)

Locke2005 (849178) | more than 3 years ago | (#34907996)

You are correct. I was trying to say that dark matter would be distinguishable from a supermassive black hole. But it would still be difficult to tell the difference between dark matter and a large group of small black holes. I too am unclear why the phenomena attributed to "dark matter" could not be adequately explained by a large number of small black holes.

Re:Dark matter vs black holes (1)

fbjon (692006) | more than 3 years ago | (#34908890)

Dark matter is not just dimly lit, it doesn't emit or interact with photons and matter at all, except through gravity (and maybe some other effects). An amount of ordinary matter spread out like a galaxy shines fairly brightly, while the same amount of dark matter would have the same mass/gravity distribution but no EM emissions.

Re:Dark matter vs black holes (1)

Locke2005 (849178) | more than 3 years ago | (#34909226)

Black holes by definition have no EM emissions from inside the event horizon. The energy emitted by black holes comes from gas being accelerated outside the event horizon, so a black hole without any surrounding cloud of matter would be much harder to detect. One could only judge it's position by it's effect on light/radio waves coming from behind it.

Re:Dark matter vs black holes (2)

c++0xFF (1758032) | more than 3 years ago | (#34908824)

The calculated mass of this body is about 1% of the Milky Way, or about 7x10^9 solar masses. The event horizon of said black hole would be about 20 billion kilometers.

The actual distance is about 260,000 light years away, or 2.5x10^18 kilometers.

And ... if I did the math right, the circle would be about .00165 arcsecond. Hubble is about .04 arcseconds for comparison. We need a telescope with about 25 times the angular resolution.

Feel free to check my math ... I probably made a mistake in there somewhere.

The point is, this would have to be a MASSIVE black hole ... but might actually be directly observable with future technology if we can manage a couple orders of magnitude improvement in angular resolution.

Re:Dark matter vs black holes (1)

Black Parrot (19622) | more than 3 years ago | (#34907624)

How do you tell the difference between a blob of dark matter and a black hole? With all the small galaxies the Milky Way has swallowed over its lifetime, would it not be reasonable to find some relic black holes that have swung back out after being stripped of most of their surrounding gas/stars? Or, when "dark matter" is being talked about in this situation, is a black hole simply one of the possible candidates to supply the mystery mass?

Good thinking - astronomers thought of it too.

I don't know the details, but they've ruled out black holes, brown dwarfs, neutrinos (except the hypothetical sterile neutrino), and all the other "normal" matter anyone knows about.

Dark matter is transparent. Black holes are opaque (2)

jfengel (409917) | more than 3 years ago | (#34907926)

Both interact with light solely through gravitation, but dark matter is constitutionally incapable of interacting with light. It's dark not because it holds onto light, but because light just passes through it the same way a piece of plastic ignores a magnetic field. (Actually, not quite the same, but it's close enough for the moment.)

Black holes may or may not interact with light; what's inside a black hole is undefined. But when light falls on it, it passes the point of no return and never leaves.

Light passing near either will be bent by the gravity, but you can tell the difference in light that falls directly on it.

In fact, because the inside of a black hole is unseeable, it's possible that you could have a black hole that condensed from a blob of dark matter. You couldn't see it, but you could infer it: if there's a black hole inside a dark matter blob, it might have fallen in that way. Unfortunately, our tools for detecting dark matter are poor, so we can't resolve them with that kind of precision.

It is possible that some of the evidence that caused us to deduce dark matter could have implied black holes instead. There are two competing theories, Weakly Interacting Massive Particles (dark matter) and Massive Compact Halo Objects (black holes). That these are called WIMPs and MACHOs is a sign that we have detected physicist humor. The MACHOs hypothesis has been largely ruled out by the failure to detect the kind of gravitational lensing that small, massive objects cause, so the suspected mass must be more diffuse. That leaves us with the WIMPs as the best hypothesis, but it leaves a lot of questions open.

A galaxy of what? Dark stars? (2)

starglider29a (719559) | more than 3 years ago | (#34907094)

What is the form of the dark matter? Does it coalesce into spherical bodies? Or does it homogenize into equidistant particles due to mutual repulsion? And if it is bound to the Milky Way by gravity, and itself bound to as a 'galaxy', does it exert cosmos expanding repulsion in an "inverse almost square" relationship? Is it 1/ (r- fudgeFactor)^2 or 1/ (r)^(2-fudgeFactor)?

Seriously. I'm a rocket scientist, and I'm baffled by the mixed properties of 'dark matter'. Can we land a probe on it, or would baryonic space probes pass right through it?

Re:A galaxy of what? Dark stars? (4, Informative)

rainmouse (1784278) | more than 3 years ago | (#34907234)

What is the form of the dark matter?

Assuming it exists at all. There is much circumstantial evidence but some argue no direct proof yet (though NASA believe the have proof). Still this excerpt from NASA seems to imply that dark matter does not interact with matter except through gravity.

"The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. "

Source: http://www.nasa.gov/home/hqnews/2006/aug/HQ_06297_CHANDRA_Dark_Matter.html [nasa.gov]

Re:A galaxy of what? Dark stars? (2)

gstoddart (321705) | more than 3 years ago | (#34907306)

Seriously. I'm a rocket scientist, and I'm baffled by the mixed properties of 'dark matter'. Can we land a probe on it, or would baryonic space probes pass right through it?

I think that's kind of the point, isn't it?

We don't know WTF it is, or what it's made up of ... only that we can measure it's gravitational effects but can't directly figure out how to observer it.

Beyond that, I've never heard anyone offer an good, testable explanation of what it is, merely what we think it isn't.

Re:A galaxy of what? Dark stars? (1)

The_Wilschon (782534) | more than 3 years ago | (#34908950)

There are lots of testable explanations of what it might be. Many of them are being tested by experiments in progress today, or will be tested by experiments in the planning or building stages. For example, the lightest supersymmetric partner (LSP) is a good candidate for dark matter. Weakly interacting massive particles (yes, WIMPs) are another good candidate, and the LSP might in fact be a WIMP, depending on the values of the parameters describing supersymmetry (if it exists).

Some proposed explanations have already been ruled out by observations. For instance, "hot" dark matter (low mass, and therefore high average momentum) is easily ruled out by observations of galactic rotation curves. "hot" dark matter would not clump together nearly tightly enough to produce the observed rotation curves. So we're left with higher mass, lower momentum cold dark matter models.

Re:A galaxy of what? Dark stars? (2)

catmistake (814204) | more than 3 years ago | (#34907326)

Seriously. I'm a rocket scientist, and I'm baffled

C'mon, man! It ain't brain surgery!

Re:A galaxy of what? Dark stars? (1)

blair1q (305137) | more than 3 years ago | (#34907334)

It doesn't emit or absorb electromagnetic radiation, or it wouldn't be "dark".

I'm not sure how there would be "mutual repulsion" in a body of free particles unless they all had the same charge. But charge is mediated by photons, which are electromagnetic radiation (from radio on up to gamma rays). Without EM, it would take a new force.

I'm kind of skeptical that such a dark-matter galaxy could exist. Galaxies are coalescence of gas by gravity. Why would there be a huge collection of particles affected by gravity that wouldn't have attracted those in the young universe that happen to do EM as well?

Re:A galaxy of what? Dark stars? (0)

Anonymous Coward | more than 3 years ago | (#34907404)

Normal matter coalesces into spherical bodies because when two particles meet, they reduce their relative speed by giving off heat. Dark matter particles just zip through each other and so they don't coalesce.

Re:A galaxy of what? Dark stars? (1)

Black Parrot (19622) | more than 3 years ago | (#34907494)

Seriously. I'm a rocket scientist, and I'm baffled by the mixed properties of 'dark matter'. Can we land a probe on it, or would baryonic space probes pass right through it?

Due to the presumed lack of electrostatic interaction, your probe could not "touch" it. You could orbit it or settle into a common center of gravity, but not land on it.

Re:A galaxy of what? Dark stars? (0)

Anonymous Coward | more than 3 years ago | (#34907608)

Give up your day job. If you're a rocket scientist and can't understand "Only interacts through the gravitational force" and you don't know that gravity could only ever be attractive (outside quantum effects) you really shouldn't be building/designing or even painting rockets. Learn about the Bullet Cluster where we observe the effects of dark matter.

Re:A galaxy of what? Dark stars? (1)

arcsimm (1084173) | more than 3 years ago | (#34907756)

I'm no scientist, but to my untrained nose dark matter has the same smell as "luminiferous aether" and "epicycles." Basically, it's a theoretical placeholder for something we don't fully grasp yet.

Re:A galaxy of what? Dark stars? (1)

blueg3 (192743) | more than 3 years ago | (#34907944)

"Dark matter" isn't really a name for a particular kind of matter with known properties. Some observations about gravitational forces don't work out quite right, as if there was a bunch of matter that we can't see. We don't really know any properties of it other than that it has mass and is otherwise undetectable (so far). Hence, "dark matter".

Re:A galaxy of what? Dark stars? (1)

The_Wilschon (782534) | more than 3 years ago | (#34908912)

There are a lot of different models for dark matter candidates. All of them have in common that the coupling of dark matter to photons is zero. Also the strong coupling constant (coupling to gluons) is zero. Some models have dark matter that interacts via the weak interaction (W and Z bosons), eg WIMPs. Other models have zero weak interaction. Some models propose brand new interactions among dark matter particles that normal baryonic matter does not couple to, but TTBOMK none of these have a coupling significantly above the weak scale. All models have a normal coupling to gravity and massive particles.

So, depending on the proposed model, the dark matter particles may interact weakly with each other, which would lead to a clumpy distribution (but clumps much larger and less dense than stars or planets), or they may interact only gravitationally (that is, _very_ weakly), leading to a distribution much like you would expect of an ideal gas (pretty uniform throughout the galaxy, maybe higher density nearer the center, maybe not).

Mark my words (0, Insightful)

Anonymous Coward | more than 3 years ago | (#34907124)

One day we'll find out why we're having to explain shit with "dark matter", and the stupid concept will be laughed at like the Luminiferous aether is now.

Re:Mark my words (4, Informative)

Beelzebud (1361137) | more than 3 years ago | (#34907358)

I don't think that's the case at all. The only reason we have "dark matter" is because of astronomical observations. That is classic science. Make an observation, and then come up with a theory to explain it. From observations we know that there is some type of mass out there affecting gravity. We call it 'dark matter' because we don't know what it is. This isn't an aether theory, it's based on real observations.

Re:Mark my words (-1)

Anonymous Coward | more than 3 years ago | (#34907596)

From observations we know that there is some type of mass out there affecting gravity. We call it 'dark matter' because we don't know what it is.

Or, there's something wrong with gravitational theory and its equations that only work when there's "dark matter" under certain circumstances.

What's more likely: that there's some unobserved physical phenomena that is called "dark matter" or that gravitational theory is incomplete and as a result, the equations describing it are also incomplete?

Re:Mark my words (0)

flaming error (1041742) | more than 3 years ago | (#34907726)

> it's based on real observations.
We can't see dark matter any more than our predecessors saw the Luminiferous aether.

> Make an observation, and then come up with a theory to explain it.
Like "Whew, those were seven bad years. Must have been that mirror I broke."

Making observations and theories is part of science. But what sets science apart from superstition is rigorous testing of the theories.

And we don't have any way to test for matter whose only property is it brings our mathematical formulae in line with our physical observations.

Re:Mark my words (1)

Alarindris (1253418) | more than 3 years ago | (#34908106)

Think of it this way: In day to day life, for everyday objects, x = 2y describes gravitational interaction. Test it over and over, and it works just fine.

Now, when we look way out into the universe at galaxies, x = 2y doesn't quite work, but if we use the formula x = 2y + .01 everything falls into place. And it works over and over.

We don't know what the .01 is, so we call it dark matter. Someday we'll figure out what it is, for now we call it dark matter. That's it.

Re:Mark my words (1)

khallow (566160) | more than 3 years ago | (#34908118)

it's based on real observations.

We can't see dark matter any more than our predecessors saw the Luminiferous aether.

Actually, we can via the gravitational effects of dark matter.

Re:Mark my words (1)

Lumpy (12016) | more than 3 years ago | (#34909600)

Then why does dark matter, that is supposed to be in bigger amounts than bright matter (stars and junk) do not form gravitational lenses like normal galaxies do?

I should be able to spot a gravitational lens that has no visible source if this dark matter coalesces into "galaxies".

This should be the easy proof to get. If this stuff is so prevalent in the universe then we should have a scientific "metric buttload" of evidence in photographs of gravitational lenses without a central galaxy.

Re:Mark my words (0)

Anonymous Coward | more than 3 years ago | (#34908144)

> it's based on real observations.
We can't see dark matter any more than our predecessors saw the Luminiferous aether.

> Make an observation, and then come up with a theory to explain it.
Like "Whew, those were seven bad years. Must have been that mirror I broke."

Making observations and theories is part of science. But what sets science apart from superstition is rigorous testing of the theories.

And we don't have any way to test for matter whose only property is it brings our mathematical formulae in line with our physical observations.

pretty much all of that is wrong.

we can in fact detect dark matter. It's the stuff that lenses light in the absence of "normal" matter. It has been observed acting in the collisions of galaxies, and galaxies composed of essentially all dark matter have been observed.

There is _something_ out there being observed. It's not just a bit of made up matter to make the equations work out, or an ad hoc addition to correct one specific inaccuracy. the question of exactly what would have the properties observed (interacts with matter gravitationally but not under any other known mechanism) is an open one. However to claim that we've never "seen it" is to not understand the advances in relevant research over the past couple of decades.

Re:Mark my words (1)

flaming error (1041742) | more than 3 years ago | (#34908344)

I'm not saying there's no such phenomenon as "dark matter" or "dark energy".

I'm agreeing with GP that our understanding of dark matter is no better than Huygen's or Boyle's understanding of the aether.

They didn't invent the aether for kicks. They had made physical observations of light and magnetism that known science could not account for. The "luminiferous aether" was an initial clumsy attempt to understand an emerging frontier in Science.

I think our successors will laugh at our clueless "dark matter" explanations for exciting phenomena we are on the cusp of discovering. But as long as our understanding is this vague, our "dark matter" is not much different than the "Luminiferous Aether" concept was three centuries ago.

Re:Mark my words (0)

Anonymous Coward | more than 3 years ago | (#34909420)

The difference is that the "luminiferous aether" is a theory that has predictive values (i.e. there should be a doppler effect on light while earth moves through the ether), while "dark matter" is merely a placeholder for a cause for a multitude of effects that we see (galaxies spinning differently from what we extect, gravitational lensing that doesn't match the visible masses etc), with multiple theories trying to explain it.

Re:Mark my words (2)

Bengie (1121981) | more than 3 years ago | (#34908196)

The difference between Dark Matter and Luminiferous Aether is they made something out of nothing. What's going on here is we have "something". We have gravity. This gravity is measurable and is out there, but we cannot find the matter associated with it.

Heck, based on the amount of gravity "Dark Matter" has, there is more of this unknown material than material we do see.

Something out there is creating a crap ton of gravity and we can't see it. Since mass is needed for gravity and matter is the only thing we know of that has mass, we figure we'll call it "Dark Matter" until we know more about it.

Dark Matter itself isn't something, Dark Matter is just the "idea" of something we don't know and we describe this unknown something as "Dark Matter".

The truth is out there..... LAWL.. had to.

I like to think of Dark Matter as a NULL value in a Database. It's a known unknown.

Re:Mark my words (4, Interesting)

Black Parrot (19622) | more than 3 years ago | (#34908340)

Let's get this out of the way first:

And we don't have any way to test for matter whose only property is it brings our mathematical formulae in line with our physical observations.

The, "Gee, that's funny" observation is what drives all science.

Now:

Making observations and theories is part of science. But what sets science apart from superstition is rigorous testing of the theories.

Believe it or not, some scientists do real science.

There was a competing explanation for this family of "Gee, that's funny" observations called MOND - Modification Of Newtonian Dynamics. It was ruled out on the basis of evidence. (There may be a MOND v. 2.0 out there now - not sure.)

One candidate for dark matter is the sterile neutrino, which people - real scientists - are trying to detect right now. A few years ago they were almost ready to dismiss its existence, but more recent results suggest that it may actually exist.

So no, contrary to your majestic disbelief, dark matter is a Real Hypothesis (tm), investigated by Real Scientists (tm), doing Real Science (tm).

If you want to actually learn something about the topic rather than simply using Slashdot as an outlet for you whingeing about the universe not working the way you learned in fifth grade, Wikipedia is an easy place to get started.

Re:Mark my words (1)

Colonel Korn (1258968) | more than 3 years ago | (#34909412)

Let's get this out of the way first:

And we don't have any way to test for matter whose only property is it brings our mathematical formulae in line with our physical observations.

The, "Gee, that's funny" observation is what drives all science.

Now:

Making observations and theories is part of science. But what sets science apart from superstition is rigorous testing of the theories.

Believe it or not, some scientists do real science.

There was a competing explanation for this family of "Gee, that's funny" observations called MOND - Modification Of Newtonian Dynamics. It was ruled out on the basis of evidence. (There may be a MOND v. 2.0 out there now - not sure.)

One candidate for dark matter is the sterile neutrino, which people - real scientists - are trying to detect right now. A few years ago they were almost ready to dismiss its existence, but more recent results suggest that it may actually exist.

So no, contrary to your majestic disbelief, dark matter is a Real Hypothesis (tm), investigated by Real Scientists (tm), doing Real Science (tm).

If you want to actually learn something about the topic rather than simply using Slashdot as an outlet for you whingeing about the universe not working the way you learned in fifth grade, Wikipedia is an easy place to get started.

I think they're up to MOND 45.2 now. The problem with MOND is that it has yet to successfully predict anything. Every new set of data requires a refinement of the concepts in MOND, whereas general relativity has successfully predicted a lot of things that were later observed. That doesn't mean MOND can't be right, but there's no particular reason to think it's right.

Re:Mark my words (4, Insightful)

Anonymous Coward | more than 3 years ago | (#34908010)

One day we'll find out why we're having to explain shit with "dark matter", and the stupid concept will be laughed at like the Luminiferous aether is now.

I don't think that's the case at all. The only reason we have "dark matter" is because of astronomical observations. That is classic science. Make an observation, and then come up with a theory to explain it. From observations we know that there is some type of mass out there affecting gravity. We call it 'dark matter' because we don't know what it is. This isn't an aether theory, it's based on real observations.

I think we actually have enough evidence for dark matter but, to be fair, the luminiferous aether was also based on real observations. There used to be a great deal of controversy over whether light was a particle or a wave. If it was a particle, it didn't need a medium to travel through, but it became very hard to explain refraction and diffraction properties. If it was a wave, then it needs a medium. We know from experiments that the medium wasn't something we could normally interact with. You can pump air out of a glass container with something that is making noise inside it, and you will no longer be able to hear the noise, because the sound waves have no medium to travel through. You'll still be able to see the object, though. Therefore, it was easy to conclude, from experimental data, that if light was a wave, there had to be some medium for light to travel through, permeating through everything, but that we couldn't interact with (pump out).

We had a bunch of observations that really demanded the presence of the Aether, until Einstein came along with his photoelectric effect papers and came up with the real solution: you know what? Light is both a particle AND a wave. That was completely unlike what we normally experience, so it's not the interpretation people were coming up with to explain their observations. A whole lot of things happened in those years, between Einstein, Planck, and deBroglie that really enriched our understanding of the universe. None of them set out to disprove the aether, it's simply that when they finally had a theory which explained every observation, the aether was no longer necessary.

I think dark matter is probably real. We can measure mass via the dynamics of celestial objects, measure mass via gravitational lensing, and come up with similar results: there's more mass there. So it doesn't seem like it's a problem with our theories. That said, there's a lot of observations dark matter doesn't explain, so if it turned out that it doesn't exist after all, I wouldn't be entirely surprised, and it would be very much like the story of the aether. There's nothing wrong with that, and there was nothing wrong with introducing the aether back in those days. That really is what science is about. You make a theory that best fits your observation, and right now dark matter beats any other alternative. If someone comes up with a better alternative, scientists will drop dark matter as fast as they dropped the aether, but until then we need to go with what we have.

Re:Mark my words (1)

m50d (797211) | more than 3 years ago | (#34908254)

The aether was exactly the same thing - an explanation for the real observation that light behaved like a propagating wave. It was perfectly legitimate science too. The situations are quite similar.

Re:Mark my words (2)

VortexCortex (1117377) | more than 3 years ago | (#34908354)

Make an observation, and then come up with a theory to explain it. From observations we know that there is some type of mass out there affecting gravity. We call it 'dark matter' because we don't know what it is. This isn't an aether theory, it's based on real observations.

So, let me get this straight, all empty space is assumed to have the same "density" properties?

When we observe gravity as a warping of space, is it not reasonable to think that the warping of space might cause an effect similar to gravity, without requiring any mass at all?

My question is this: Why do we assume that all "empty space" is uniform?

Could it be that "dark matter" is simply "empty space" that is naturally "curved"?

One theory is that our universe exists on a "(mem)brane". What's to say that the membrane itself is perfectly smooth?

Perhaps it was, but the big bang (or other past universe-scale forces) caused ripples in the fabric of space-time itself.

Perhaps the variations in the space-time fabric density explain why energy/matter began to "clump" together, perhaps it just pooled into the valleys.

TL;DR: Dark matter may actually be nothing at all -- thus explaining: Why we can't observe dark matter; Why normal energy & matter pass right through it; Why the big bang's energy was not uniformly distributed.

Re:Mark my words (1)

Drethon (1445051) | more than 3 years ago | (#34908554)

I'm not an expert in astronomy by any stretch (engineering is my area of expertise) but my understanding of a lot of astronomy is a lot of what we observe is interpretation. Most of physics was determined by watching something move and producing a model. In astronomy we can't actually watch things move (much beyond our solar system anyway), instead we look at light and try to translate this into the motion that we can't see (primarily using red shift). What if red shift or our other ways of interpreting this light is wrong? Not so much about the whole theory (though has red shift ever been detected in an object we can also measure the actual velocity of?) but even if red shift is not linear or off by a certain factor, how much would that mess up the existing theories?

Re:Mark my words (1)

Ramze (640788) | more than 3 years ago | (#34909394)

Obviously, there are gravitational distortions in space-time that current theories cannot explain. The idea that there is some sort of exotic matter creating those gravitational distortions is an untestable hypothesis (unless you know of a way to go out and collect the dark matter which may exist in these regions to run experiments on it).

It is equally likely that those regions of space are experiencing distortions due to some unknown natural distortion in space-time's structure itself or are caused by an interaction with another universe in the multiverse. It's also possible that our current model of how gravity works is incorrect at large scales due to other factors we don't yet understand. In any case, the distortions are at such a large scale and at such great distance from us that any hypothesis will be difficult to test.

"Dark Matter" is just a word for "something out there we can't see is causing gravitational distortions we can't account for." There's no reason the cause has to be some form of matter we haven't seen yet. Particle physicists haven't a clue what kind of a particle would have mass, but no interaction with light. People assume the distortions are caused by mass because all known distortions our theories work for are caused by mass, but all known normal mass particles also interact with light or emit light. So, people simply make up hypothetical particles with mass, but no interaction with light -- because they NEED for them to exist to fit their assumption that mass in our universe is causing the distortion.

I think it's far more likely we don't yet understand some aspect of gravity on galactic scales than there is some sort of magic form of matter that makes our current equations make sense in the areas that currently make no sense to us whatsoever.

Re:Mark my words (1)

Anon-Admin (443764) | more than 3 years ago | (#34907382)

Ahhhh, and me with no mod points! Some one should mod this up!

Re:Mark my words (5, Insightful)

Black Parrot (19622) | more than 3 years ago | (#34907588)

One day we'll find out why we're having to explain shit with "dark matter", and the stupid concept will be laughed at like the Luminiferous aether is now.

Yeah, like neutrinos and X-rays and all that other weird shit people made up to explain problems away.

Re:Mark my words (1)

scorp1us (235526) | more than 3 years ago | (#34907754)

Dark matter is the fudge factor which explains the rotation of galaxies whose outer extents rotate too fast for known orbital mechanics. Applying Occums's razor, the explanation is missing mass. The alternative explanations:
Time is not as constant as we think. (Allowing for General Relativity)
Gravity does not work as we think over large distances.
Dark Energy (companion/alternative to DM)

Those first two are often dismissed as being too complicated because we've got plenty examples of our predictions being right based on those assumptions, and sort-of rule out Dark Energy. But be it Energy or matter it is some form of a quantifiable unknown.

Faced with revising our equations for reality on the small-medium scale, we'd rather say matter is escaping detection for the large scale.

Re:Mark my words (2)

Zorpheus (857617) | more than 3 years ago | (#34908502)

Gravity does not work as we think over large distances.

The Pioneer Anomaly [wikipedia.org] and the Flyby Anomaly [wikipedia.org] are indicating that gravity actually works a bit different than we think. Maybe we will see a new formulation of gravity in the future, explaining these and removing the need for dark matter.

Re:Mark my words (0)

Anonymous Coward | more than 3 years ago | (#34909270)

New formulations of gravity can't work. To show that all you have to do is find two spots in the universe that have similar visible mass neighborhoods, but different kinetic behaviors. However innovative or complicated the formulation f of gravity is, you can't have f(x) != f(x). Dark matter postulates a new invisible scalar field which can explain the different kinetic behaviors by being different in the two neighborhoods.

Occlusion? (1)

popo (107611) | more than 3 years ago | (#34907316)

Wouldn't dark matter galaxies so close to ours result in the occlusion of galaxies behind them?

Since a galaxy is mostly empty space -- wouldn't this result in a detectable degree of light variation?

Re:Occlusion? (1)

Black Parrot (19622) | more than 3 years ago | (#34907532)

Wouldn't dark matter galaxies so close to ours result in the occlusion of galaxies behind them?

Since a galaxy is mostly empty space -- wouldn't this result in a detectable degree of light variation?

No, for the dark matter hypothesis to work as an explanation of what it's supposed to explain, it doesn't have any kind of EML interaction with normal matter, so it can't obscure any more than it can be seen.

It does bend space, and AIUI the best support for the DM hypothesis is the lensing effect it has at a distant cluster, but there may not be enough in the postulated satellite galaxies to cause any detectable lensing.

Re:Occlusion? (0)

Anonymous Coward | more than 3 years ago | (#34907832)

Or better yet, why can't "dark matter" be merely regular matter that is occluded from observation by other masses? Imagine a galaxy that is in near perfect rotation with another galaxy (relative to us) but just slightly farther away. We would not be able to see any emission from the 2nd galaxy, or if we did, it would be very difficult to separate it from the emissions of closer galaxy. On a smaller scale, it could be two solar systems, or even just a pair of stars (one bright, one dead).

Or why can't "dark matter" be small objects with mass that are spread throughout our universe. They are small enough that they interact very rarely, and when they do, it blends in to other emissions or perhaps we have explained the emission away with another theory (background radiation?)

What if there are particles spread all over space and the cosmic microwave background radiation is actually the emission caused by interaction with these particles?

Re:Occlusion? (1)

The_Wilschon (782534) | more than 3 years ago | (#34908998)

These are good ideas. They are so good, in fact, that lots of people who work on this stuff have already had them. The consequences of these hypotheses are not too difficult to work out, and people have done that, too. However, having worked out those consequences, and learned where and how to look to see if these hypotheses are correct, we find that their predictions do not agree with observation. A slashdot comment is certainly not the place to recount all of this, so if you are still curious or don't want to take my word for it, I'd suggest a look at the relevant and current literature. For instance, try looking up information on MACHOs (MAssive Compact Halo Objects), which are none other than your hypothesized "small objects with mass that are spread throughout our universe".

Re:Occlusion? (1)

Fnkmaster (89084) | more than 3 years ago | (#34908160)

I believe the whole deal is that this dwarf dark matter galaxy is on the far side of the milky way and in the same plane (or nearly so) as the majority of the milky way, and thus is difficult to directly detect in terms of gravitational lensing effects. The article wasn't clear however on what the actual technique used was, but obviously it must be *some* form of gravitational lensing.

Dark matter is always there when you need it (1)

DaKritter (158840) | more than 3 years ago | (#34907514)

Tell me, what properties does dark matter have, save for explaining the factor 2-4 miscalculation of the universe's mass?

Re:Dark matter is always there when you need it (1)

Black Parrot (19622) | more than 3 years ago | (#34907790)

Tell me, what properties does dark matter have, save for explaining the factor 2-4 miscalculation of the universe's mass?

What you describe isn't a property, it's an effect. (And I've never heard of any such miscalculation anyway.)

Properties: it has mass (bends space)... don't know of any others, except the trivial stuff like it can move and be scattered around.

Effects: explains galactic rotation curves, explains some instances of lensing, possibly explains the perturbations this article is about.

Re:Dark matter is always there when you need it (2)

DaKritter (158840) | more than 3 years ago | (#34908274)

Properties: it has mass (bends space)... don't know of any others, except the trivial stuff like it can move and be scattered around.

Effects: explains galactic rotation curves, explains some instances of lensing, possibly explains the perturbations this article is about.

Yeah, it has exactly the one property that someone is missing: mass. But is conveniently free of any other property that could influence anything.

The explanations you refer to are all based on calculations that are ultimately based on our understanding of gravity. The least understood force, the one that just won't fit into the picture. What a real scientist should do was to better research and explain gravity instead of making up some magic invisible soup to fix it all.

Pseudoscience, I say.

Re:Dark matter is always there when you need it (1)

Black Parrot (19622) | more than 3 years ago | (#34908370)

Pseudoscience, I say.

I'm sure the cosmology journals are eagerly awaiting your article.

Re:Dark matter is always there when you need it (1)

jkauzlar (596349) | more than 3 years ago | (#34909196)

This guy gets some flak from moderators, but really, he makes an interesting point. How do we know that 'dark matter' isn't an invention to compensate for errors in our understanding of the gravitational force in the same way that the 'luminescent ether' was an invention? I'm not saying the parent is right, I'm only asking, how do we know?

Fault (0)

Anonymous Coward | more than 3 years ago | (#34907612)

It's all George W. Bushes fault! He didn't sign Koyoto, causing Global Warming, and this Darkie matter.

I know what dark matter ist!!! (1)

Tanuki64 (989726) | more than 3 years ago | (#34907762)

Ages ago I have seen 'The Elegant Universe'. There was a real nice explanation of several flavours of the string theory. One of the points was that gravity is so weak compared to the other forces because part of it wanders off into neighbouring universes. If this is true, why should only our gravity wander away from us? It would be expected, that at the same time gravity from other universes would come into ours. So dark matter is simply normal matter from a neighbouring universe from which we 'see' part of its gravity footprint. We cannot see anything else because it there is nothing there in our universe.

Disclaimer: 'The Elegant Universe' was a very entertaining science documentation. Easy to understand, fun to watch, but most likely got it totally wrong. Probably as wrong as my fun theory.

:-D

Re:I know what dark matter ist!!! (1)

pavon (30274) | more than 3 years ago | (#34908128)

Actually, preliminary data [arstechnica.com] from the LHC seems to invalidate the forms of string theory that predict that.

Obligitory... (0)

Anonymous Coward | more than 3 years ago | (#34907836)

I for one welcome our new dark matter overlords from Galaxy X !!!

Absoluteley Stunning! (0)

Anonymous Coward | more than 3 years ago | (#34908590)

her picture! Don't just stop with her pictures, check out her CV, too (http://astro.berkeley.edu/~sukanya/). Impressive for some one quite young. The geeks all over have a new geek goddess!

I wonder if M&M/Marrs... (1)

PinchDuck (199974) | more than 3 years ago | (#34908694)

will sue the astronomers who found it over copyright violations. They've had "Mikey Way Dark' out for years.

Re:I wonder if M&M/Marrs... (0)

Anonymous Coward | more than 3 years ago | (#34909000)

That's not covered by copyright. If you're going to try to bring your politics into a situation at least be good enough to know when it applies.

mmm candy.. wait (1)

JonnyRocks (877543) | more than 3 years ago | (#34908952)

It took me three seconds to realize I wasn't reading about a new dark chocolate milky way candy bar. I guess it's time to go home.
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