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Mysterious X-ray Signal Hints At Dark Matter

Soulskill posted about 2 months ago | from the or-the-light-from-the-death-star-explosion-finally-reached-us dept.

Space 100

Astronomers using the Chandra X-ray Observatory and the XMM-Newton have recorded an unusual emission of X-ray light from a remote cluster of galaxies which may turn out to be evidence of dark matter. Astronomers think dark matter constitutes 85% of the matter in the Universe, but does not emit or absorb light like “normal” matter such as protons, neutrons and electrons that make up the familiar elements observed in planets, stars, and galaxies. Because of this, scientists must use indirect methods to search for clues about dark matter. he latest results from Chandra and XMM-Newton consist of an unidentified X-ray emission line, that is, a spike of intensity at a very specific wavelength of X-ray light. Astronomers detected this emission line in the Perseus galaxy cluster using both Chandra and XMM-Newton. They also found the line in a combined study of 73 other galaxy clusters with XMM-Newton. ... The authors suggest this emission line could be a signature from the decay of a "sterile neutrino." (Abstract.) Sterile neutrinos are a hypothetical type of neutrino that is predicted to interact with normal matter only via gravity. Some scientists have proposed that sterile neutrinos may at least partially explain dark matter.

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stimulate all of our senses & spirits at once (-1)

Anonymous Coward | about 2 months ago | (#47317967)

that's what creation does. trying to identify & contain it has failed us miserably... see also; motive = results some still calling this 'weather'? http://www.youtube.com/results?search_query=wmd+weather get ready to be transparent?

Re:stimulate all of our senses & spirits at on (1)

jfdavis668 (1414919) | about 2 months ago | (#47317993)

Umm.. Can someone translate this into English?

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47318043)

Here, I broke it down [imgur.com] for you.

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47318065)

Not without a bong.

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47318169)

Tried that. Still gibberish... Maybe I should try again...

Re:stimulate all of our senses & spirits at on (1)

FatdogHaiku (978357) | about 2 months ago | (#47318349)

Not without a bong.

Tried that. Still gibberish... Maybe I should try again...

You also need a bag of Oreo flavored Doritos...

Re:stimulate all of our senses & spirits at on (2)

NoNonAlphaCharsHere (2201864) | about 2 months ago | (#47318603)

...Oreo flavored Doritos...

Do you have a newsletter?

Re:stimulate all of our senses & spirits at on (1)

FatdogHaiku (978357) | about 2 months ago | (#47321643)

...Oreo flavored Doritos...

Do you have a newsletter?

No, just a buddy with keys to the Colorado research division of ConGlomCo...
but I may have said too much...

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47319025)

Weed isn't going to get you that far out. Try some ketamine!

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47319583)

It depends what kind of english?

Normal human with average IQ and understands that science is real?

Or

Extremist right wing moron speak?

Re:stimulate all of our senses & spirits at on (2)

ScentCone (795499) | about 2 months ago | (#47320119)

Normal human with average IQ and understands that science is real?

Or

Extremist right wing moron speak?

I was hoping you could translate it into left wing moron speak, perhaps using a metaphor involving healing crystals and/or homeopathy. That'd be super, thanks. If that's too hard, perhaps just translate it into some sort of yoga-energy-manipulation example, or maybe use the interaction of wind turbines killing thousands of bats as an analogy to the sterile neutrons decaying.

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47319641)

The AC is saying that we should pity the fools, those nutless neutrons.

Re:stimulate all of our senses & spirits at on (4, Funny)

kruach aum (1934852) | about 2 months ago | (#47318125)

"When the Sun shines upon Earth, 2 – major Time points are created on opposite sides of Earth – known as Midday and Midnight. Where the 2 major Time forces join, synergy creates 2 new minor Time points we recognize as Sunup and Sundown. The 4-equidistant Time points can be considered as Time Square imprinted upon the circle of Earth. In a single rotation of the Earth sphere, each Time corner point rotates through the other 3-corner Time points, thus creating 16 corners, 96 hours and 4-simultaneous 24-hour Days within a single rotation of Earth – equated to a Higher Order of Life Time Cube."

I just realized this reference may be too old, and that made me sad.

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47318563)

Anyone who does not agree with the preceding statement is probably an educated stupid fool.

Re:stimulate all of our senses & spirits at on (0)

Anonymous Coward | about 2 months ago | (#47318875)

The Time-Life Building isn't in Time Square. It's on 6th Avenue.

Re:stimulate all of our senses & spirits at on (2)

Vyse of Arcadia (1220278) | about 2 months ago | (#47319203)

I dunno about Time Cube, but I feel like the Thyme Cube [thymecube.com] guy is on to something.

I think I've figured out Time Cube (1)

tepples (727027) | about 2 months ago | (#47321339)

Really, the "4-simultaneous 24-hour Days" of Time Cube are just so many words to express the concept of dividing the world into four time zones. That's it. Now let's go play some GameCube [archive.org] .

This too shall pass (1, Insightful)

NoNonAlphaCharsHere (2201864) | about 2 months ago | (#47318001)

Phlogiston, the luminiferous aether, the Rutherford atom, dark matter, dark energy, the Higgs field...

Maybe one day we'll explore the idea that the geometry of space-time isn't flat, and that most of our constants aren't.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47318107)

Maybe one day we'll explore the idea that the geometry of space-time isn't flat, and that most of our constants aren't.

At least for the first half, we've been looking at that for nearly hundred years now, and the second half we've been trying to look for but haven't found anything yet.

Re:This too shall pass (3, Insightful)

CaptainLard (1902452) | about 2 months ago | (#47318433)

Phlogiston, the luminiferous aether, the Rutherford atom, dark matter, dark energy, the Higgs field... .

Getting closer every day...

Maybe one day we'll explore the idea that the geometry of space-time isn't flat, and that most of our constants aren't.

Whats stopping you?

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47318705)

Phlogiston, the luminiferous aether, the Rutherford atom, dark matter, dark energy, the Higgs field... .

Getting closer every day...

Maybe one day we'll explore the idea that the geometry of space-time isn't flat, and that most of our constants aren't.

Actually the that constants aren't constant (in time) is being looked at experimentally (Mentioned by one of my lecturers).
Also the idea that space it self isn't flat has also been investigated (Not an astrophysicist, but if I remember correctly current verdict is it's flat/nearly flat).

Re:This too shall pass (3, Informative)

Anonymous Coward | about 2 months ago | (#47319147)

Also the idea that space it self isn't flat has also been investigated (Not an astrophysicist, but if I remember correctly current verdict is it's flat/nearly flat).

The whole point of General Relativity, about to turn 100 years old next year, is that space is not flat on various scales. Observation suggests on the largest scales it averages out to flat, but physicists have put a lot of effort into understanding non-flat space on smaller scales (and even large scales in case observations are wrong).

Re:This too shall pass (1)

Lumpy (12016) | about 2 months ago | (#47319599)

Money and Physics.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47321005)

The lack of need for it? Given the verified discovery of intrastellar planets, and the difficulty of detecting them at galactic distances, most of the galactic constant "anomalies" are easily accounted for by these unexpected, apparently ubiquitous but quite ordinary matter components of galactic space.

I know it's very exciting for grad students to hypothesize new and exotic matter, but for cripes' sake, between inventing complex and unnecessary Higgs' Bogons, unverifiable "strings" of exotic properties, "white holes", and other unnecessary and unreproducible matter, you'd think that at least *one* thesis review committe would learn how to spell Occam's Razor.

Re:This too shall pass (1)

Anonymous Coward | about 2 months ago | (#47321605)

Given the verified discovery of intrastellar planets, and the difficulty of detecting them at galactic distances, most of the galactic constant "anomalies" are easily accounted for by these unexpected, apparently ubiquitous but quite ordinary matter components of galactic space.

What you say seems to be directly in contradiction with what studies of rogue planets and black holes found: while there are some out there, there are far, far fewer than would be needed to account for missing mass to address things like the galactic curve issue. Plus most modern models of dark matter at this point already incorporate or even suggest that there is much more normal matter out there than we can see, that not only is some 70% of the matter of the universe in some form not acting like atoms and other standard model particles, but that 75% of the ordinary matter is missing too, that there is 3-4 times as much ordinary matter out there than we can see.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47318599)

The speed of light isn't constant either. Space isn't contant, it is expanding. Space and time are connected. Speed is dependant on time, so therefore the speed of light is changing with the expansion of the Universe.

Re:This too shall pass (3, Insightful)

wonkey_monkey (2592601) | about 2 months ago | (#47318645)

so therefore the speed of light is changing with the expansion of the Universe.

No, it isn't.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47319027)

Do you have data from a 5 Billion years ago to prove this? Redshifting is great, but objects are actually farther away than they appear.

Think of a photon traveling from one end of the Universe right after the Big Bang and finally reaching Earth. It would be redshifted to hell, but how do you know that redshift corresponds to actual distance traveled or relative distance traveled?

As the Universe expands, the gap between point A and B increases. Now where is the halfway point during this trip if the Universe keeps expanding? That middle point would be continually changing. So it will take the photon less time to reach the first half, than it will take the photon to travel the last half, because of expansion.

This all seems very elementary if you just stop and think about it.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47319193)

The effect you are describing is already taken account into any basic treatment of the expanding universe and is how you get that beyond distances of a couple billion light years, the distance in light years does not equal the number years the light traveled. For more details you can look into something like comoving distance, but the idea that the halfway point is somewhere else once light gets there, etc., is already integrated into mainstream cosmology for about as long as expanding metric GR solutions have existed... decades. Nonetheless, the speed of light is defined is constant to any observer, and that is a local concept, not something you get by looking at how space on a global scale moves.

Re:This too shall pass (1)

Paradise Pete (33184) | about 2 months ago | (#47319555)

Do you have data from a 5 Billion years ago to prove this?

I think you are misplacing the burden of proof.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47321389)

That doesn't mean the light ever went faster or slower than the speed of light - it just means a naive approach of saying "It came from something x meters away, it travelled at speed c, so it must've left x / c ago" is wrong.

This is a very well known fact, and not disputed, but doesn't mean the speed of light is wrong. It just means calculating the speed of light using the distance in current space-time rather than the distance while it travelled is wrong because you're using a technique that inherently assumes the distance is a constant.

Re:This too shall pass (1)

dreamchaser (49529) | about 2 months ago | (#47323329)

When you make an extraordinary claim the onus is on you to offer proof. All evidence we have to date suggests that C is a constant and has not changed. Therefor, if you assert that it does change it's on you to prove your claim, not for others to disprove it.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47323481)

All evidence we have to date suggests that C is a constant and has not changed.

All evidence we have to date suggests that the earliest moments of the big bang everything expanded faster than C, therefore light itself would have been faster than C, therefore we have evidence to support that the speed of C *has* changed since the universes inception.

What our empirical evidence shows is that C has not changed any measurable amount since we were first able to measure it.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47323637)

All evidence we have to date suggests that C is a constant and has not changed.

All evidence we have to date suggests that the earliest moments of the big bang everything expanded faster than C, therefore light itself would have been faster than C, therefore we have evidence to support that the speed of C *has* changed since the universes inception.

No. The rate at which space expands has nothing to do with the speed of light because the speed of light refers to the *local* speed of a photon, i.e. the speed an observer would measure it to have just as it passes him. What you are thinking of are recessional velocities, which is the rate at which the coordinates of a separate object changes. In general relativity, the (local) speed of light is a constant, while recessional velocities can be anything - in fact a single object can have multiple different recession velocities if there are multiple lines of sight towards the same object due to complicated spacetime topologies.

Also, the expansion itself doesn't correspond to any particular recession velocity by itself. The expansion is simply a measurement of how long it takes the universe to grow bigger by some factor. For a given rate of expansion, there will be different recession velocities for different objects depending on the distance to each object. Those recession velocities can be higher than the local speed of light, but that doesn't mean that it's meaningful to say that space is expanding superluminally.

I recommend this review article [arxiv.org] for a discussion of these issues.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47324315)

If you are going to define c in a way that is different from what physicists use, then don't be surprised when you get different behaviour and results that don't actually get any attention. People who use their own definition for things that have standard formal definitions will get written off as ignorant of the topic they are trying to discuss.

Re:This too shall pass (2)

bill_mcgonigle (4333) | about 2 months ago | (#47318713)

Hey, there's some suggestive evidence that our universe may be discrete and quantized around 10^-27 (and cheats to the Plank length). That's almost aether.

Granted, we should study the skull surface shape of these scientists, just to be sure.

Re:This too shall pass (2)

Soft (266615) | about 2 months ago | (#47318841)

Bullet cluster, bitches! [calamitiesofnature.com]

Re:This too shall pass (1)

Livius (318358) | about 2 months ago | (#47319891)

Phogiston (thermal energy) and the luminiferous aether (space-time geometry) are real. It was the materials science metaphors that were wrong.

Re:This too shall pass (1)

Antique Geekmeister (740220) | about 2 months ago | (#47321049)

I'm afraid that the "liminiferous aether" was the medium on which electromagenetic waves were carried. It was disproven by the Michelson Moreley experiment, which led to a lot of _other_ fascinating theories. Phlogiston was no more "thermal energy" than vacuum is what you pour into vacuum tubes. It was what came _out_ of burning substances and was contained in them to leak out as fire.

Please don't rewrite the history of physics and chemistry to try and invent "privatives", the measurable absence of a something found elsewhere, as a a "real" substance.

Re:This too shall pass (0)

Anonymous Coward | about 2 months ago | (#47322257)

"Maybe one day we'll explore the idea that the geometry of space-time isn't flat"

You are not up to speed on this, are you. http://en.wikipedia.org/wiki/Shape_of_the_universe

"and that most of our constants aren't."

Why would anyone entertain the suggestion that you know more about these things than all cosmologists combined?

Re:This too shall pass (1)

m.alessandrini (1587467) | about 2 months ago | (#47322277)

Some theoretical models seem to work by admitting that there are extra dimensions hidden to our senses, like superstring theory (it has something like 11 dimensions). Very extreme, but some observed results can actually be derived by their equations. Nothing is to be discarded as too odd, I guess.

Re:This too shall pass (1)

Muad'Dave (255648) | about 2 months ago | (#47326303)

Phlogiston Paradise!!! Ruuuuby Rod!

Dark matter explained (0)

For a Free Internet (1594621) | about 2 months ago | (#47318025)

It is nose farts from slashdort beta and Mercury, the heaviest planet, which disrupts the universe by spinning the wrong way my teacher is a genius and is not a pop atart.

Why isn't time dark matter? (2)

Nyder (754090) | about 2 months ago | (#47318081)

Granted I know nothing about such matters, but I wondered why time couldn't be dark matter?

Re:Why isn't time dark matter? (1)

geekoid (135745) | about 2 months ago | (#47318137)

Because time doesn't impact mass.

Re:Why isn't time dark matter? (5, Funny)

TWX (665546) | about 2 months ago | (#47318161)

Because time doesn't impact mass.

You should see my sister-in-law...

Re:Why isn't time dark matter? (4, Funny)

PolygamousRanchKid (1290638) | about 2 months ago | (#47318509)

Because time doesn't impact mass.

You should see my sister-in-law...

Marriage impacts mass. Just compare the waistlines of your single and married friends, and you will see what I mean.

At night, a bachelor goes to the refrigerator, looks at what's inside, and then goes directly to bed.

At night, a married man goes to the bedroom, looks at what's inside, and then goes directly to the refrigerator.

Re:Why isn't time dark matter? (2)

TWX (665546) | about 2 months ago | (#47319263)

I thought marriage was created by mass, at least for most Catholics...

Re:Why isn't time dark matter? (1)

rahvin112 (446269) | about 2 months ago | (#47320149)

Although there is sometimes a weight gain with marriage, it's usually the kids that cause the waistline expansion.

Re:Why isn't time dark matter? (1)

Jason Goatcher (3498937) | about 2 months ago | (#47321571)

Even more so after they're born.

(Not trying to usurp the joke, you just didn't explain it enough ;) :) )

Re:Why isn't time dark matter? (1)

Anonymous Coward | about 2 months ago | (#47318695)

You should see my sister-in-law...

I do. Don't tell your brother.

Re:Why isn't time dark matter? (0)

Anonymous Coward | about 2 months ago | (#47318651)

Spacetime is impacted by mass. Einstein says so.

Re:Why isn't time dark matter? (0)

Anonymous Coward | about 2 months ago | (#47318913)

Space-time is a set of dimensions, mass exists within space-time.

Re:Why isn't time dark matter? (1)

Charliemopps (1157495) | about 2 months ago | (#47319465)

Because time doesn't impact mass.

Actually, mass and time are directly related:
http://en.wikipedia.org/wiki/G... [wikipedia.org]

Time is not dark matter however. We understand time, and time dilatation. As crazy as it is, we have that part figured out.
Time is another dimension, like length, width, etc... but it is treated a tad different, but this is a very deep subject, you might as well read on it from smarter people than I: http://en.wikipedia.org/wiki/S... [wikipedia.org]
Time does not have mass, though it affects mas.

Dark matter however behaves a lot like other matter. Don't let physisists fool you. They are very guarded group. But we pretty much have dark matter figured out. Things we know pretty much for sure about dark matter:
There's a LOT of it.
It's everywhere.
It clumps together just like dust in a house.
It's diffuse... so while there's a lot of it, it's very spread out.
we can't see it for some reason. Most of the ways we know to detect particles do not work on it. The only way we know it even exists is because it still interacts gravitationally with normal matter.

So we pretty much know what it is, we can describe it well enough already. We just need to find direct evidence of it and give it a proper name.

There's still a chance that we made some silly error, but that grows increasingly unlikely every day.

Re:Why isn't time dark matter? (0)

Anonymous Coward | about 2 months ago | (#47320201)

It clumps together just like dust in a house.

There isn't anything suggesting it clumps together in the sense of sticking to other dark matter. Most models that do pretty well have it just following gravity and inertia, which means forming large clouds and halos around galaxies because the particles spend a long, long time orbiting the center of the galaxy when they don't interact with things other than gravity.

Re:Why isn't time dark matter? (4, Informative)

Jason Levine (196982) | about 2 months ago | (#47318157)

Basically, IIRC, the best models that we have to explain the Universe say the Universe should have X amount of matter in it. When we look at the Universe, though, we see only 15% of X existing. So either our models are wildly off or there is a type of matter out there that we can't currently detect (so-called "dark matter" because we can't see it). In the case of the former, it's possible, but that would toss other theories - with more firm proof for them - out as well. In the case of the latter, it's completely possible that there is sort of a self-selection bias in play. We see normal matter regularly so our detection methods have been geared towards normal matter and miss the dark stuff.

Re:Why isn't time dark matter? (0)

Anonymous Coward | about 2 months ago | (#47323347)

It's not the universe, it's remote galaxies that were the first hint that dark matter exists. They rotate differently from what one would expect from the visible mass - a lot of extra mass is required for the outer parts to be able to orbit around the center at the speed they do (without being flung out into space).

Re:Why isn't time dark matter? (2, Funny)

Anonymous Coward | about 2 months ago | (#47318165)

Similarly I'm thinking that length could be magnetism. We should collaborate and revolutionize physics!

Re:Why isn't time dark matter? (2)

Russ1642 (1087959) | about 2 months ago | (#47318273)

Time is a four sided square universal time-cube, not dark matter.

Re:Why isn't time dark matter? (1)

Neil Boekend (1854906) | about 2 months ago | (#47322359)

Time is a nonlinear wibbly wobbly mess.

Omicronian scanning technology (0)

Anonymous Coward | about 2 months ago | (#47318177)

Courtesy of Omicron Persei 8.

Prepare to die, human scum!

Move along (0)

Anonymous Coward | about 2 months ago | (#47318471)

Lrrr here, that x-ray burst was just Ndnd blowing up another microwave oven with tin-foil.

Doesn't jive for me (3, Insightful)

Pro923 (1447307) | about 2 months ago | (#47318527)

If photons with a frequency in the visible spectrum don't react with "dark matter" than why would photons with a frequency in the xray spectrum?

Re:Doesn't jive for me (3, Informative)

An Ominous Coward (13324) | about 2 months ago | (#47318681)

The hypothesis is not that the X-Rays are interacting with this type of dark matter. It is that the decay of this type of dark matter generates X-Rays.

Re:Doesn't jive for me (2)

drall.kj (3527169) | about 2 months ago | (#47319099)

I get what you are saying but.... if it can decay into a photon isn't that the same as emitting a photon? The first line quoted above is "but does not emit or absorb light like “normal” matter." If it can generate a Photon (by decay or someother means) it can't be dark. I'm not that smart but Dark Mattter/Energy thing just stinks of take a stab in the dark (no pun intended). I think some where we have some constant of the universe calculated wrong, or we are estimating the mass of the galaxies wrong.

Re:Doesn't jive for me (4, Informative)

An Ominous Coward (13324) | about 2 months ago | (#47319469)

It's the ambiguity of language that's at fault here. The key to the sentence you mentioned is "like normal matter". Normal matter absorbs electromagnetic radiation, increasing its energy level, and drops back to lower energy levels by emitting electromagnetic radiation. Thus, normal matter interacts with light. This is a different physical process than the emission of light due to decay of the particle itself.

And while we haven't pinned down dark matter by any means, it's much more than a stab in the dark. For one, there are known particles--neutrinos--that do not interact via the electromagnetic force, so the idea of unknown particles with the same property isn't unrealistic.

Then, there are clues from many different directions that point to something consistent with matter that interacts gravitationally but not electromagnetically. These include calculations concerning the total matter in the universe, galaxy cluster formation, the rotational speed of stars on the out edge of galaxies, etc.

Re:Doesn't jive for me (2, Interesting)

Anonymous Coward | about 2 months ago | (#47319781)

Defining dark matter as having zero interaction with electromagnetism is at best a terse over-simplification and at worst just wrong. Dark matter does not strongly interact with electromagnetism, meaning that it for the most part doesn't interfere with light other than from gravity in places we think there are lots of it. But that doesn't preclude it from having rare or much harder to see interactions, such as decays, or rare interactions with high energy photons, or creating Cerenkov radiation when passing through a detector as some experiments are looking for. For a while, astronomers wondered if dark matter could literally just be chunks of rock or black holes, otherwise normal matter that absorbed but didn't emit light. Although surveys of the sky set upper bounds on the amount of such things to be too low. Further evidence suggests it isn't made out of normal things like protons. But none of that means it can't have weak or rare interactions with light, just that whatever interaction there is has to be weak enough to not have conflicted with previous observations.

Re:Doesn't jive for me (1)

Pro923 (1447307) | about 2 months ago | (#47323779)

I agree that it is more likely some missed calculation... My theory has always been that space itself has more physical dimensions than three. So, dark matter is just the collection of regular matter that doesn't happen to share the same 3-dimensional space as we do at any given instant. It jives because, light from our 3 dimensional space wouldn't "Hit it", though it's gravitational effects would be present. I like to use a 2-dimensional analogy to think these things through... If we were 2-dimensional beings that lived on a sheet of paper, anything above or below that paper would be dark matter to us. Our sun, in our 2 dimensional plane, wouldn't produce rays that would bounce off that matter and into our eyes. We'd be able to feel the gravitational pull though. Perhaps the universe is like an ocean, where the matter oscillates above and below the 3 dimensional space that we are presently in. The thing that always makes me think is - if I were one of these 2-dimensional beings on my sheet of paper, what possible means could i use to access that 3'rd dimension? If we could move an inch out of our 3-dimensional space for just a second - would we die instantly? Would any part of the earth occupy that 4th dimension? If it did, it would be dark to us in normal times. Could all of our calculations still work if our round planets had some 4'th dimensional component in which some matter were present?

Re:Doesn't jive for me (1)

david_thornley (598059) | about 2 months ago | (#47327951)

Why would gravity propagate where light didn't? If it extended into at least one other dimension, why does it obey the inverse square law, rather than an inverse cube law? Do you have any vague idea for a testable prediction?

Re:Doesn't jive for me (1)

Pro923 (1447307) | about 2 months ago | (#47330061)

Gravity is bending of space due to the presence of matter. To use the 2d analogy, it doesn't matter if the object were above or below the paper, you'd still feel the pull of gravity. Light is a ray of photons. What you can see, is a ray of photons that bounce off an object and into your eye. if something were above or below the paper, the light from our 2d sun would never hit it. There would be no way to detect it other than gravity. I have some ideas for testing the plausibility of space being more than 3 dimensions, but none for accessing matter or gaining any kind of momentum into that 4th dimension.

Re:Doesn't jive for me (1)

Pro923 (1447307) | about 2 months ago | (#47331927)

To be more specific about the testing of 4th dimensional space... I thought of using an enclosed cube containing some solid that isn't too - well, solid. I think that cosmic rays are chunks of matter that are thrown across the universe, possibly from a place that doesn't share the same 3-dimensional space as us (possibly off by small amounts - meters even). This is why they can pass through solid objects - the don't pass through them, they go around them in the 4th dimension. As they travel through space at high speeds, they oscillate in and out of our 3-dimensional space as they adjust for the gravity of the local matter. The cube, placed in orbit, could take a few hits from cosmic rays. The shape should be the same as if you shot a bullet diagonally through a cube of balsa wood, then cut a thin sheet from the middle of it.

Re:Doesn't jive for me (0)

Anonymous Coward | about 2 months ago | (#47333547)

Cosmic ray detectors have already been placed in space, plus there are a lot looking at both things on the ground, ones in balloons higher in the atmosphere, and telescopes that look at collisions between cosmic rays and the atmosphere. Cosmic rays are mostly protons, with some alpha particles and a small handful of other nuclei and positrons. They act just like we would expect high energy protons, and the lower energy ones act just like the protons produced in particle accelerators. This includes hitting matter, whether a solid or liquid in a detector, or the gas in the atmosphere. The primary cosmic rays (the parts from space) rarely can make it through even the upper parts of the atmosphere, and all that makes it to the surface are secondary cosmic rays, the pieces that result from the high energy collision of atom in the upper atmosphere and the cosmic ray. The part known for being particularly penetrating are the muons that are created in the spray of particles from the collision, but even then the difference between the rate they slow down and electrons slow down is only about a factor of ten for a large part, plus the muons have a lot more momentum and take longer to stop even if being slowed down by the same rate.

Re:Doesn't jive for me (1)

RockDoctor (15477) | about 2 months ago | (#47337393)

If photons with a frequency in the visible spectrum don't react with "dark matter" than why would photons with a frequency in the x-ray spectrum?

For the same reason that if photons in the red end of the visible spectrum don't interact with this red-transmitting filter, then why would photons at the X-ray end of the visible part of the spectrum?

Wavelength matters to absorption spectra. That's rather what makes them spectra.

It's always dark matter. Except when it isn't. (0)

mcelrath (8027) | about 2 months ago | (#47318579)

Hey look, it's $something_we_dont_understand, and ooh, I can claim it's evidence for $todays_fad!

Astrophysics is big, messy, complicated, and difficult to measure. We just can't send probes to other galaxies to see what's really going on. Most of the time these things have more mundane explanations. But, until we figure out why galactic rotation curves are wonky, everyone will claim everything is due to dark matter.

Re:It's always dark matter. Except when it isn't. (1)

I'm New Around Here (1154723) | about 2 months ago | (#47318667)

What is the best discussion of galactic rotation curves? Best for a layperson, I should say.

Re:It's always dark matter. Except when it isn't. (1)

mcelrath (8027) | about 2 months ago | (#47319585)

Wikipedia is usually a good reference. These two articles talk about it. It's the oldest evidence for "dark matter". Either that or it's evidence that gravity doesn't behave entirely the way described by Einstein. The latter view has fallen out of favor due to the lack of good theories adopting that viewpoint. The former has fallen into favor due to the copious selection of theories containing a particle with little or no interactions (it's easy to do). Neither of these theory-spaces has been proven to be correct (yet).

Re:It's always dark matter. Except when it isn't. (1)

Anonymous Coward | about 2 months ago | (#47318945)

Hey look, it's $something_we_dont_understand, and ooh, I can claim it's evidence for $todays_fad!

Astrophysics is big, messy, complicated, and difficult to measure. We just can't send probes to other galaxies to see what's really going on. Most of the time these things have more mundane explanations. But, until we figure out why galactic rotation curves are wonky, everyone will claim everything is due to dark matter.

Today's fad? Dark Matter as an idea has been around for many decades (in some form since the 30s). It's supported by a massive amount of observational evidence - its not just rotational curves of galaxies. Its lensing observations and cosmic microwave background observations and velocity dispersion measurements etc. If you are going to claim that scientists don't know what they are doing, at least take the time to read the wikipedia article on Dark Matter or something similar - it would give you some idea of all the evidence you are unaware of.

On top of that, many of these observations use completely independent areas of physics. For example, rotational curves of galaxies use Newtonian Mechanics, while lensing observations of clusters of galaxies use General Relativity. These are completely independent sets of physics, yet they predict consistent amounts of dark matter. So why would completely independent sets of physics all predict the same amount of dark matter from observations? Well, the most mundane answer is that dark matter is real.

Re:It's always dark matter. Except when it isn't. (2)

mcelrath (8027) | about 2 months ago | (#47319499)

Let's have some fun. [lmgtfy.com] Also remember that luminiferous aether was an idea that was around for a long time as well. Dark matter is a difficult-to-disprove fad, without any real competing ideas. That will not always be the case.

Re:It's always dark matter. Except when it isn't. (1)

rahvin112 (446269) | about 2 months ago | (#47320219)

I think of this like string theory. They've got an answer searching for a problem.

Dark matter is one of those as well. They've theorized dark matter and attributed each unexplained item in astrophysics to it but have no real evidence it exists. As the other reply said to you this is not any different than the luminiferous aether that preceded it. Dark mater may or may not exist, but it would be foolish to attribute that which we can't explain to something that we can't see or measure. All those attributes of dark matter could easily be explained by other possible items including cosmic strings, wormholes, etc.

Dark matter is currently in vogue, that doesn't mean it's reality. Much of the hype behind dark matter is that if it exists and there is enough of it then it would explain the big bang. This has created a desire among some in the scientific community to want it to be true because it presents a nice clean solution with a recyclable universe. My personal feeling on it is that we're missing something big, that something is the explanation for where all the anti-matter went and it might explain many of these other anomalies that some are attributing to dark matter. I'm probably wrong, but I'm willing to bet so are the dark matter proponents.

Re:It's always dark matter. Except when it isn't. (1)

Electricity Likes Me (1098643) | about 2 months ago | (#47320383)

The Slashdot armchair physicist brigade is out in force I see...

Re:It's always dark matter. Except when it isn't. (0)

Anonymous Coward | about 2 months ago | (#47320441)

They've got an answer searching for a problem.

Right or wrong, dark matter is a textbook case of the exact opposite, an answer posed in response to a very specific problem...

Dark matter is currently in vogue

As is bashing dark matter via internet comments.

Re:It's always dark matter. Except when it isn't. (0)

Anonymous Coward | about 2 months ago | (#47320457)

This has created a desire among some in the scientific community to want it to be true because it presents a nice clean solution with a recyclable universe.

This is all science is, the collection of theories that give the cleanest solutions. If you want the truth behind reality, go to a philosophy department instead.

Re:It's always dark matter. Except when it isn't. (1)

Lord Crc (151920) | about 2 months ago | (#47320621)

Dark matter is one of those as well. They've theorized dark matter and attributed each unexplained item in astrophysics to it but have no real evidence it exists.

No. You got it exactly backwards. It's entirely the opposite of string theory. String theory was born as a theoretical construct and they're trying to figure out how to make predictions with it so they can see if it matches the real world.

When it comes to dark matter, what they have is a ton of observations which does not match the predictions of our current theories. What they see is mass being affected by something we can't see. So they've given it a label until we figure out what it is: dark matter.

So, just to repeat, dark matter is just a label given to what we can see happening but which we cannot currently explain with our established theories (GR and Standard Model). Hence it absolutely is reality!

And no, having "enough" dark matter would not explain the big bang. However certain dark matter theory-candidates give predictions which can explain the matter distribution in the galaxy, which neatly solves another puzzle.

You can read up on some details here about the latter: http://www.illustris-project.org/about/#public [illustris-project.org]

Re:It's always dark matter. Except when it isn't. (1)

painandgreed (692585) | about 2 months ago | (#47319403)

But, until we figure out why galactic rotation curves are wonky, everyone will claim everything is due to dark matter.

Well, rotation curves, gravitational lensing by galaxies, missing amounts of matter needed in the beginning universe to show us what we are seeing today, and about four other separate methods of observations that are all hinting at the same thing. Thing is that this isn't a fad, it's been one of many different theories put forth and tested since these observations started popping up in the early part of the 20th century. So far, everything theory that hasn't been "matter that doesn't interact with EM radiation" has failed while "dark matter" actually has successes such as the Bullet Cluster. Meanwhile, such explainations such as MOND, modified gravitational equations, have yet to come up with even a hypothetical example that matches what we see. It's not a fad at this point, just tested science. Difference is that you are just hearing about it. It is a developing theory, less than a hundred years old from the first observational evidence, but at this point, if what is causing all of these observations isn't "matter that doesn't interact with EM radiation", it's something that acts just like it and is much stranger.

Re:It's always dark matter. Except when it isn't. (1)

mcelrath (8027) | about 2 months ago | (#47319523)

Well yes but if I had typed all that in my original post it would not have been as pithy and interesting. I'm not just hearing about this, I've written many academic papers on it, and I have serious reservations about the idea. *sigh* back to work...

Re:It's always dark matter. Except when it isn't. (0)

Anonymous Coward | about 2 months ago | (#47319815)

Gee, it would be a real shame to lose pithiness and interest by not oversimplifying something to the point of possibly being misleading...

Re:It's always dark matter. Except when it isn't. (1)

able1234au (995975) | about 2 months ago | (#47321561)

Can you share your alternative theory/papers? i am sure people here would be interested.

Re:It's always dark matter. Except when it isn't. (1)

RockDoctor (15477) | about 2 months ago | (#47337477)

It took me 30 seconds searching to find a couple of dozen papers in this general field of research, by someone called "McElrath". I know that it may seem heretical to you near-7 digiters, but some people use their real names (or in my case, profession) here, and have done for approaching two decades now.

Re:It's always dark matter. Except when it isn't. (0)

Anonymous Coward | about 2 months ago | (#47319691)

But, until we figure out why galactic rotation curves are wonky, everyone will claim everything is due to dark matter.

Actually this is explained by most of the Global Warming models.

What ever happened to Occam's Razor? (3, Insightful)

Squidlips (1206004) | about 2 months ago | (#47318643)

Why do these crackpot-darkmatter-theories-du-jour all smell like mysticism?

What ever happened to Occam's Razor? (4, Insightful)

Anonymous Coward | about 2 months ago | (#47318871)

Because you don't understand them, so you assume they must be hokum.

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47319513)

Why do these crackpot-darkmatter-theories-du-jour all smell like mysticism?

Hey look! An actual example of begging the question!

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47319827)

Because you judge scientific theories based on angry armchair scientists' internet posts, and they base their posts on which theories they have a gut feeling for despite having superficial and outdated knowledge of the theory they "just know" is wrong without having to check any calculations, predictions, or observations?

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47319959)

I'm not sure but I thought most monks had beards.... so William of Ockham's razor would have been rather neglected methinks.

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47322269)

"Why do these crackpot-darkmatter-theories-du-jour all smell like mysticism?"

It does not. It's just that you want to suggest that it does.

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47323543)

Why do these crackpot-darkmatter-theories-du-jour all smell like mysticism?

I wouldnt call it mysticism as much as I would call it a "great unknown". We have the math to calculate gravity in our localized space, but when we look at a bigger slice of the universe (even galaxy) we see some inconsistencies that dont make sense. This means 1 of 2 things:
  1) there is additional matter in the universe that we cannot detect
  2) we misunderstand gravity at large distances

Since we can be very precise about gravity at shorter distances the assumption that we understand gravity can be maintained, therefore the most plausible explanation is #1.

No mysticism... Just trying to understand nature in the most rational way possible.

Re:What ever happened to Occam's Razor? (0)

Anonymous Coward | about 2 months ago | (#47324295)

Since we can be very precise about gravity at shorter distances the assumption that we understand gravity can be maintained, therefore the most plausible explanation is #1.

That is not the reason physicists chose answer #1 over #2. There were many attempts to try new gravity theories to explain the effects without missing matter, and there are still research groups dedicated to working with some of the better gravity models or to come up with new ones. The problem is they don't explain things better than the models using dark matter, that they can some times address one thing that dark matter does but not all, and even then with some glaring issues. Both approaches have been tried (and are still being retried), and the plausibility of #1 vs #2 is based on the current state of the results of trying both.

My bet..? (0)

Mister Liberty (769145) | about 2 months ago | (#47320257)

It's a flock of pigeons.

Temple University, not Drexel University (0)

Anonymous Coward | about 2 months ago | (#47323729)

And certainly not University of Drexel. https://phys.cst.temple.edu/directory/faculty/tao.html [temple.edu]

Dark Matter (1)

Winkkin (1258228) | about 2 months ago | (#47331259)

Basically the dark matter may be nothing more than another type of neutrino, and we finally found its calling card.
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