Intergalactic Missing Mass Missing Again

Ponca City, We Love You writes "Researchers at the University Of Alabama In Huntsville have discovered that some x-rays thought to come from intergalactic clouds of 'warm' gas are instead probably caused by lightweight electrons — leaving the mass of the universe as much as ten to 20 percent lighter (in terms of its ordinary matter) than previously calculated. In 2002 the same team reported finding large amounts of extra 'soft' (relatively low-energy) x-rays coming from the vast spaces in the middle of galaxy clusters. Their cumulative mass was thought to account for as much as ten percent of the mass and gravity needed to hold together galaxies, galaxy clusters, and perhaps the universe itself. When the team looked at data from a galaxy cluster in the southern sky, however, they found that energy from those additional soft x-rays doesn't look like it should. 'The best, most logical explanation seems to be that a large fraction of the energy comes from electrons smashing into photons instead of from warm atoms and ions, which would have recognizable spectral emission lines,' said Dr. Max Bonamente. The work was published Oct. 20 in the Astrophysical Journal."

The falloff of light is 1/r^2

[BadAnalogyGuy (945258)]

As light fans out, it does so at the rate of 1/r^2. Double the distance, and you've quadrupled the surface area of the light beam. You've also reduced the luminosity at any point in the beam's surface by a quarter.

But why do we just assume that gravity needs to fall off at the same rate as light?

Re:The falloff of light is 1/r^2

[QuantumG (50515)]

As stupid as you are, someone who is even more stupid than you will read your post and mod you up.

That's the magic of Slashdot.

Re:

[NewbieProgrammerMan (558327)]

Er, it's not that somebody "assumed" that it works that way out of the blue; hundreds of years of observations of objects interacting via gravity led some smart people to figure out that those observations are best explained by a gravity that falls off as 1/r^2 (or something very, very, very close to it).

Re:The falloff of light is 1/r^2

[Aesir1984 (1120417)]

It's because the surface area of a sphere increases as r^2 so anything that expands into a volume will fall off in intensity at this rate without outside influence. The only reason this would change is if space-time is curved which we have run experiments to test and if there is a curvature it is so slight as to be negligible for experiments like TFA talks about.

As for the person above who mentioned that light might not expand as 1/r^2 outside of a gravity well, the fact is that it doesn't expand at exactly 1/r^2 inside a gravity well. But we 1/r^2 is a good approximation for any gravitational fields near us.

Re:Bias in Physics?

[644bd346996 (1012333)]

Do you really expect language like that to cause somebody to re-evaluate some of the most well-verified physical laws ever postulated?

"Einstein fanatics"?! "demigod"?! You sound like a crackpot UFO conspiracy theorist. If you think there are flaws with the current models, the only acceptable way to address those concerns is with science. Not ad-hominem attacks against people who are demonstrably smarter and more polite than you.

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[644bd346996 (1012333)]

Whoops. I seem to have given a knee-jerk response to a troll.

By the looks of his sig, his hobby is to say "but what if your most basic, obvious principles are completely wrong?" without offering a better explanation. And without even realizing that people before him (and smarter than him) have asked the same question, and always verified the conventional wisdom. I realize now that he is wholly unconcerned with science, and merely dabbles in pseudo-science and demagoguery pandering towards those even less ed

Re:

[sammy baby (14909)]

Don't be a hater. The power of TIME CUBE [timecube.com] compels you!

Re:Bias in Physics?

[tm2b (42473)]

He might be a crackpot, but the idea isn't. Google on MOND [wikipedia.org].

What's easier to believe - that there's a ton of missing mass out there as "Dark Matter" - something that we have no direct evidence for - or that gravity works differently on large scales than a smoothe 1/r^2 at all distances - and works exactly in the way that we observe? Remember that every time that we've had a strong classical theory replaced by something else, it's been at the extremes of our observation - the very fast for special relativity (which reduces to newtonian motion at lower speeds) and the very small for quantum mechanics. We know we're not getting something right on the large scale, and we know that our picture of gravity is incomplete, as we don't have a good quantum gravitational model.

I don't know, honestly - but it's clear that there's something we don't understand and I think that our human-scale intuition is not well suited for figuring out what explanation is more likely, just as QM and SR aren't very intuitive. Right now, we've got competing models but neither is very satisfactory without more data.

Re:

[tm2b (42473)]

No, it isn't. The problem is that the data favor neither one model nor the other at this time - we don't have the whole picture and we know it. GR is clearly not sufficient to model gravity, it and QM can not be made to play well together.

By the way, did I mention my physics degree?

Re:

[phliar (87116)]

The problem is that the data favor neither one model nor the other at this time - we don't have the whole picture and we know it.

No one ever claimed GR was "the whole picture". Do you believe that MOND can do better than GR at modelling, say, gravitational time dilation?

By the way, did I mention my physics degree?

Tell me honestly: how many physics undergrads do you think really know GR or QM?

Re:Bias in Physics?

[tm2b (42473)]

I never advocated tossing GR out the window, it's way too successful and I have way too much investment in the math to reject it (as they say, nature abhors a second order differential equation, right?).

Don't be silly. MOND doesn't cover the regime of gravitational time dilation- and is in fact not at odds with GR. MOND and GR cover different regimes, MOND concerns itself with gravitational/inertial interactions at very small accelerations (of less than about 10^-10 m/s^2, ignoring the Hubble constant correction term).

The point is that we have a fundamental choice between believing that there's more mass that we can't detect by EM in the Universe than that which we can detect, or that we're missing a big piece of how gravity (or, if you prefer, inertia) works, or (of course) "something else." And the jury is absolutely still out.

While the physics community certainly favors the dark matter model right now, most will say that the door isn't shut on MOND yet. Dismissing anybody who mentions it as a crank is not reasonable and it's dishonest to try to put a Mr. Physics Authority Figure face on doing so - MOND papers are still published in indiscriminate rags like the Journal of Cosmology and Astroparticle Physics and tenure-holding proponents are seen in polite company that would shun cold fusion researchers.

I have no idea how many physics undergrads "really" know GR and QM - I suspect that most probably haven't gotten past the wave equation formulation or even heard of quantum field theory, and might or might not have had to sling a few tensors around in an elective - most probably don't do graduate computational cosmology work, either (even if it was back when having time on a Cray meant something). There's more money in commercial software, though.

Re:

[Nazlfrag (1035012)]

And that word is that today GR is the best theory of gravity we have.

Yet we have observations that don't fit the theory, both on the small and large scales. The theory is either incomplete, or our observations are incorrect. Seeing as we don't alter empirical data to fit theories, we must alter the theories to fit the empirical data. It is the best theory we have, and still it breaks, so we strive for a new theory to explain all the facts. MOND and string theory are two such theories that make real predict

Re:

[phliar (87116)]

Yet we have observations that don't fit the theory, both on the small and large scales.

So? We know GR is not THE solution; I said it was the best we have. We know it has holes. But GR is not just about gravity; it is about the structure of space-time. Gravity (and lots of other things) fall out of it. MOND is a hack to explain one kind of phenomenon. Of course we need to strive towards a better model of the physical universe than GR+QM, but MOND isn't it. As wikipedia puts it, "MOND is an effective theo

Re:

[644bd346996 (1012333)]

More ad-hominem. Any science on the menu? If you have any well-reasoned alternative theories, do please post them (or better yet, publish them where more scientists will be watching). And if you would care to respond directly to any of my points, I would probably read it.

By the way, when did you last attend a university science class?

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[SnoopJeDi (859765)]

I believe he was making a joke. It certainly was funny.

By the way, when did you last attend a university science class?

I'm pretty sure Einstein didn't dream up special relativity in class. Physics happens outside the classroom, too. In fact, being in the classroom almost prohibits overturning pre-existing science, because you're there to learn, not to make it up as you go along.

Physics happens outside the classroom too.
I mean, depending on your frame of reference and all.

Re:

[tjstork (137384)]

The Einstein fanatics and the Big Bang proponents refuse to consider it as a possibility (a lot of careers depend on Big Bang and Esintein being right). Einstein is a demigod in some circles and his wisdom must not be questioned. As a result little funding is allocated for research in this area. That's too bad. We are probably missing some very exciting physics in the process.


Boy, this is spoken like someone who is completely disconnected from the academic process. There is no bigger fantasy a 20-something

Re:Bias in Physics?

[Nazlfrag (1035012)]

...they are a bunch of sharks circling information, just waiting for that first bit of blood that suggests a hole in some established theory.

Trying to poke holes in in established theories (also known as conducting experiments and analysing empirical data) is more properly called the scientific method. You make it sound like a bad thing, and that ivory tower guardians of cryptic scrolls are the true scientists. You have it all backwards. Theories shouldn't need propping up, they should stand on their own, and especially stand up to repeated scrutiny and analysis. If we failed to poke holes in established methodology there would be no Newton, no Einstein, no progress to speak of.

Re:

[tjstork (137384)]

You make it sound like a bad thing, and that ivory tower guardians of cryptic scrolls are the true scientists. You have it all backwards

No, not at all. I think you are making the assumption that I mean to say that sharks are bad. Sharks aren't bad, they are sharks. Get it?

The guy I was replying to implied that scientists had a vested interest in propping up the cryptic scrolls. I merely called scientists sharks sniffing for blood, not to make a value judgement, but just as an example of how eager they a

To summarize it another way...

[tjstork (137384)]

All any so-called crackpot needs to do, to prove his or her alternate theory of matter correct, is to build his or her anti-gravity machine, reverse the flow of heat from cold to hot, or do something simple and repeatable that shocks us into a new way of looking at physics. If entropy is wrong, gravity is wrong, electricity is wrong, then, let's see the new gadget that proves it. Or, barring that, point to the heavens and make a prediction about something we haven't seen before, and do so with math that is

Re:

[wanerious (712877)]

But why do we just assume that gravity needs to fall off at the same rate as light?

Newton's Law for gravity specifies it as a 1/r^2 force. *Any* 1/r^2 force will behave the same way.

Do the math.

[644bd346996 (1012333)]

Please. It really isn't hard to show that the dependency on r can only take on a few values and still yield a universe that comes at all close to what we observe. For example, the only halfway-plausible power of r that allows closed orbits (such as planets around stars) in classical mechanics is exactly 2. All other values either don't allow closed orbits in general, or are trivially shown by experiment to be absurdly wrong. Now, we have observed that orbits aren't exactly closed (the most famous example being the precession of the perihelion of Mercury), but these were explained astoundingly well by relativity.

Astrophysics is way beyond getting the growth rate of a fundamental force wrong.

Thought Experiments of 1/r^2

[tjstork (137384)]

The growth rate could be proportional to 1/r^2 on a galactic scale, but diverge from that on an intergalactic scale.


I think everyone throwing out 1/r^2 needs to really think about what it means. You don't need to be a hyperphysics guy to sort this out. The idea is really simple, is that, if you have a point source of some effect, radiating out equally in all directions, its effect would diminish as to the square of the distance. This "law" is really just a model that's a consequence of two things - one i

Re:The falloff of light is 1/r^2

[Jarjarthejedi (996957)]

Precisely. I know you've gotten a lot of poor responses but I've always thought this was a good theory (from when I first heard of the idea in MOND Modified Newtonian Gravity). Science has made a lot of assumptions about the universe, and this is one of them. Whether gravity falls off at a slightly slower rate or there is a large volume of unknown matter in the universe the end result will be the same, so why do people so quickly call others idiots when they suggest an alternate explanation?

Re:

[phliar (87116)]

The problem is that dark matter explains three different phenomena, but MOND can only do galactic rotation curves. If you throw out GR, can MOND explain the precession of Mercury's orbit? Or gravitational lensing, or frame-dragging, or gravitational time-dilation, or ... that GR models correctly?

Re:

[Ambitwistor (1041236)]

All MOND states (last time I checked) is that gravities falloff rate is slower at long distances.

MOND is weirder than that. Instead of modifying gravity at some length scale as you suggest, MOND makes the gravitational force dependent on a body's acceleration instead of just its position.

MOND's main problems are that (1) it can't account for as many phenomena as can dark matter (it does great on galactic rotation curves but not so great at, say, cosmology), (2) it's hard to make consistent with relativity (Bekenstein has a proposal but it has a number of free parameters that appear to require fine tu

Re:

[jay-be-em (664602)]

It's remarkable to me that you knew that and didn't know Newton's Law of Universal Gravitation,
and the amount of evidence that it's a very close approximation in most situations.

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[Tribbin (565963)]

"As light fans out, it does so at the rate of 1/r^2. Double the distance, and you've quadrupled the surface area of the light beam. You've also reduced the luminosity at any point in the beam's surface by a quarter."

You mean reduced TO a quarter or reduced by three quarters.

Happiness is...

[zifferent (656342)]

a warm gas. (and lightweight electrons.)

soo..

[PhrostyMcByte (589271)]

is the obesity problem over then?

Re:

[wizardforce (1005805)]

is the obesity problem over then?

Researchers later reported that the missing mass has been found on Earth so that would be a no. :)

Ballpoint pen theory of mass differential

[by Anonymous Coward]

The other, slightly less, logical explanation is that the difference in mass can simply be explained by the number of missing ballpoint pens in the universe.

Re:Ballpoint pen theory of mass differential

[by Anonymous Coward]

The other, slightly less, logical explanation is that the difference in mass can simply be explained by the number of missing ballpoint pens in the universe.

No, the Dryer/Sofa Correspondence Theorem elegantly shows that the deficit of pens is exactly cancelled out by excess right socks. (And it also demonstrates that contrary to popular urban legend, the supposed "missing" left socks never existed in this universe in the first place.)

Re:Ballpoint pen theory of mass differential

[jamstar7 (694492)]

The other, slightly less, logical explanation is that the difference in mass can simply be explained by the number of missing ballpoint pens in the universe.

But that doesn't explain where all those goddamned clothes hangers come from.

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[ozbird (127571)]

But that doesn't explain where all those goddamned clothes hangers come from.

They must be the adult form of "lost" teaspoons.

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[DrVomact (726065)]

The other, slightly less, logical explanation is that the difference in mass can simply be explained by the number of missing ballpoint pens in the universe.

But that doesn't explain where all those goddamned clothes hangers come from.

Clothes hangers are the larval form of the fully adult right sock. The amazing life cycle of this organism begins, of course, with the egg—often mistaken for "paper clips". Corpses are indistinguishable from old technical journals.

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[MillionthMonkey (240664)]

I think we know why the standard kilogram is getting lighter. It's filled with pens and people are bringing them back without the caps.

uh huh...

[djupedal (584558)]

The best, most logical explanation seems to be that a large fraction of the current theories put out are similar to the remaining fractions in that they are all delivered out the little brown holes of out-of-control modern astro-theoreticians.

Lighter mass?

[noidentity (188756)]

[...] leaving the mass of the universe as much as ten to 20 percent lighter[...]

I can understand the universe being lighter, but its mass being lighter?

Now, back to my new computer that has a faster speed yet runs at a colder temperature. I'm going to move its location, which will require a longer length of Ethernet cable. Hopefully this farther distance from the router won't be a problem.

Eureka!

[headkase (533448)]

Based on nothing more than pure speculation, I believe the missing mass of the Universe is tucked away in all those little tiny extra dimensions at the planck scale of things.
Of course I'm wrong but hey - this is Slashdot.

Re:

[Bill, Shooter of Bul (629286)]

Get a couple letters after your name, write that using scientific gargon aka "Math", "earn" a reputation by publishing mostly obvious observations and restating other peoples ideas using different sentence structures, and then you'd have a better than 50/50 shot of publishing that idea in a journal.

US Consumers Clueless, says Survey

[Kohath (38547)]

US Consumers Clueless about Missing Intergalactic Mass

"A study on consumer perceptions about missing intergalactic mass, undertaken by the Asimov Institute at the University of Phoenix Online and the Speilberg Space Policy Center, found that the average American consumer is largely unaware that some x-rays thought to come from intergalactic clouds of 'warm' gas are instead probably caused by lightweight electrons. Those surveyed showed little knowledge on the extent to which the mass of the universe was previously calculated. More than half of those surveyed -- about 55 percent -- falsely assumed that large amounts of extra 'soft' galaxy clusters were actually a light chocolatey candy. ...

Dish Maintenance Log

[RuBLed (995686)]

July 2000 - Maintenance cleaning on the dish (by John) December 2000 - Damn squirrels, cleaned some surface of the dish (by John) May 2001 - Checked dish, seems to be clean (by Sir John) December 2001 - Dish seems to be clean (by Captain John) January 2002 - Sandstorm hit, sandstorms in January? heck, I'm going on vacation (by Admiral John) December 2002 - Cleaned the dish, had a hard time with the dust, now i remember.. (by Senator John) ... July 2004 - Cleaned the dish (by Emperor John) ... July 2007 - Cl

Lost and found

[tuomoks (246421)]

Maybe it's me, I'm sure it is just me, but lately it seems that there is more lost and found mass in universe than files in a system? Maybe it is more difficult subject? I'm waiting when they get the final numbers out, I'm still under 1000 years old.

Diet?

[PPH (736903)]

Is the galaxy on the same diet as Oprah?

Bohr Atom

[Whiteox (919863)]

"lightweight electrons"????
For God's Sake! There really was nothing wrong with Bohr's atom was there?
I'm still trying to explain wave and particle theory to my pug dog, who gazes intently into my eyes!
Now I've got to try and explain electrons that don't 'weigh'(?) as much!

The Importance of Intergalactic Mass

[ezzthetic (976321)]

To lose the intergalactic mass once might be considered a misfortune. To lose it twice begins to look like carelessness.

Re:

[PPH (736903)]

Socks aren't lost. They are the larval form of coat hangers.

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[beckerist (985855)]

Planetary. Planetary intergalactic. Another dimension!

Intergelatic

[jlehtira (655619)]

That's probably a typo, it should say intergelatic. That's something between ice creams.

Re:

[bradbury (33372)]

I would be inclined to agree. Spitzer isn't really equipped to study the really interesting (longer) IR wavelengths. Nor is SOFIA. Unfortunately there doesn't seem to be a strong interest in an IR survey telescope. Perhaps a telescope on the far side of the moon would be a good idea but it seems likely that will be a decade or more away.