New insights on how spiral galaxies get their arms

Apr 02, 2013
Powerful new computer simulations are allowing astronomers to understand how spiral arms in galaxies form and survive. These simulations suggest that the arms arise as a result of the influence of giant molecular clouds - star forming regions or nurseries common in galaxies. Introduced into the simulation, the clouds act as "perturbers" and are enough to not only initiate the formation of spiral arms but to sustain them indefinitely. In this frame from one such simulation, more than 100 million "stellar particles" form the familiar shape of a spiral galaxy. Credit: Thiago Ize & Chris Johnson (Scientific Computing and Imaging Institute)

(Phys.org) —Spiral galaxies are some of the most beautiful and photogenic residents of the universe. Our own Milky Way is a spiral. Our solar system and Earth reside somewhere near one of its filamentous arms. And nearly 70 percent of the galaxies closest to the Milky Way are spirals.

But despite their common shape, how galaxies like ours get and maintain their characteristic arms has proved to be an enduring puzzle in astrophysics. How do the arms of spiral galaxies arise? Do they change or come and go over time?

The answers to these and other questions are now coming into focus as researchers capitalize on powerful new to follow the motions of as many as 100 million "stellar particles" as gravity and other astrophysical forces sculpt them into familiar galactic shapes. A team of researchers from the University of Wisconsin-Madison and the Harvard-Smithsonian Center for Astrophysics reports simulations that seem to resolve long-standing questions about the origin and life history of spiral arms in disk galaxies.

This video is not supported by your browser at this time.

"We show for the first time that stellar spiral arms are not transient features, as claimed for several decades," says UW-Madison Elena D'Onghia, who led the new research along with Harvard colleagues Mark Vogelsberger and Lars Hernquist.

"The spiral arms are self-perpetuating, persistent, and surprisingly long lived," adds Vogelsberger.

The origin and fate of the emblematic spiral arms in disk galaxies have been debated by astrophysicists for decades, with two theories predominating. One holds that the arms come and go over time. A second and widely held theory is that the material that makes up the arms - stars, gas and dust - is affected by differences in gravity and jams up, like cars at rush hour, sustaining the arms for long periods.

The new results fall somewhere in between the two theories and suggest that the arms arise in the first place as a result of the influence of giant molecular clouds - star forming regions or nurseries common in galaxies. Introduced into the simulation, the clouds act as "perturbers" and are enough to not only initiate the formation of spiral arms but to sustain them indefinitely.

This Hubble Space Telescope photo of Messier 74 reminds us that spiral galaxies are some of the most beautiful and photogenic residents of the universe. Nearly 70 percent of the galaxies closest to the Milky Way are spirals. New research finds that spiral arms are self-perpetuating, persistent, and surprisingly long lived. Credit: NASA/ESA/Hubble Heritage Team

"We find they are forming ," explains D'Onghia. "Past theory held the arms would go away with the perturbations removed, but we see that (once formed) the arms self-perpetuate, even when the perturbations are removed. It proves that once the arms are generated through these clouds, they can exist on their own through (the influence of) gravity, even in the extreme when the perturbations are no longer there."

The new study modeled stand-alone disk galaxies, those not influenced by another nearby galaxy or object. Some recent studies have explored the likelihood that spiral galaxies with a close neighbor (a nearby dwarf galaxy, for example) get their arms as gravity from the satellite galaxy pulls on the disk of its neighbor.

According to Vogelsberger and Hernquist, the new simulations can be used to reinterpret observational data, looking at both the high-density molecular clouds as well as gravitationally induced "holes" in space as the mechanisms that drive the formation of the characteristic arms of spiral galaxies.

The team's research was published in the March 20 issue of The Astrophysical Journal and is available online.

Explore further: Computers beat brainpower when it comes to counting stars

More information: arxiv.org/abs/1204.0513

Related Stories

Hubble eyes a loose spiral galaxy

Nov 26, 2012

(Phys.org)—The Hubble Space Telescope has spotted the spiral galaxy ESO 499-G37, seen here against a backdrop of distant galaxies, scattered with nearby stars.

A new, distant arm of the Milky Way galaxy

Jun 13, 2011

(PhysOrg.com) -- Our Milky Way galaxy, like other spiral galaxies, has a disk with sweeping arms of stars, gas, and dust that curve around the galaxy like the arms of a huge pinwheel.

A spiral galaxy in Hydra

Apr 09, 2012

(Phys.org) -- This image from the NASA/ESA Hubble Space Telescope shows NGC 4980, a spiral galaxy in the southern constellation of Hydra. The shape of NGC 4980 appears slightly deformed, something which is ...

Space image: Spiral galaxy

Dec 19, 2011

(PhysOrg.com) -- Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing ...

Hubble image of galaxies' El Dorado

Mar 12, 2012

(PhysOrg.com) -- NASA's Hubble Space Telescope has produced this beautiful image of the galaxy NGC 1483. NGC 1483 is a barred spiral galaxy located in the southern constellation of Dorado — the dolphinfish ...

Recommended for you

ESO image: A study in scarlet

19 hours ago

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

Astronomers: 'Tilt-a-worlds' could harbor life

Apr 15, 2014

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, ...

Pushy neighbors force stellar twins to diverge

Apr 15, 2014

(Phys.org) —Much like an environment influences people, so too do cosmic communities affect even giant dazzling stars: Peering deep into the Milky Way galaxy's center from a high-flying observatory, Cornell ...

Image: Multiple protostars within IRAS 20324+4057

Apr 14, 2014

(Phys.org) —A bright blue tadpole appears to swim through the inky blackness of space. Known as IRAS 20324+4057 but dubbed "the Tadpole", this clump of gas and dust has given birth to a bright protostar, ...

User comments : 53

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1.3 / 5 (18) Apr 02, 2013
Garbage in, garbage out... Stellar traffic jam? Fools!
Jeffhans1
1.8 / 5 (12) Apr 02, 2013
Or they are remnants of an active SMBH at the center of the galaxy causing a tremendous magnetic field that drags stars and gases into the field lines that spin at the same rate as the black hole.... Oddly enough this would explain multiple inconsistencies like the outer stars of most galaxies spinning at a higher velocity than can be explained by gravity alone or why galaxies seem to organize themselves into clusters. There doesn't need to be any dark matter or dark energy. A stuttering EM field emanating from Galactic centers would alternate from the gravity dominated quiescent phase when the SMBH is not ripping a star into its components.
rubberman
1.5 / 5 (11) Apr 02, 2013
@ Jeff's post - Well said.

"A stuttering EM field emanating from Galactic centers ..."

The funny thing is that it doesn't stutter, once the field is established, even it's initial source blowing apart (planetary nebulae) doesn't cause the field to diminish as long as there is energy present to sustain it. A galactic scale field wouldn't behave any differently.

http://www.youtub...lyiW-xGI

Agreed CD. (not on the fools thing though, "astrophysicist" and "fool" don't usually collide in the same sentence)
Torbjorn_Larsson_OM
4.7 / 5 (12) Apr 02, 2013
Nice! This make ellipticals and irregulars the odd ones out.

And now for the PhysOrg crowd of those who have nothing interesting to say on any subject whatsoever, the lackluster incompetents that feel the itch to scratch what they mistake for "science" (unsupported, often crackpot, speculation), sadly on precisely on a site that should be devoted to science instead:

@cantread: "Stellar traffic jam? Fools!"

No, since it was part of the working prediction. You are the obvious fool here.

@Jeffhans: "Or they are...". No, since this model worked and we have no other as good. Certainly not based on SMBHs.

@rubberman: "EM field emanating from Galactic centers". Which mapping shows none of. Galactic fields magnitude are diminutive. (Easy to google.)
trapezoid
1.8 / 5 (5) Apr 02, 2013
AWT DID IT
Dr_toad
3 / 5 (2) Apr 02, 2013
I hope that was meant to be funny. 8)
rubberman
1 / 5 (4) Apr 02, 2013
Oh sorry tor...name one object of any structure that is PROVEN to exist having been constructed using a purely attractive force....
ValeriaT
1.9 / 5 (9) Apr 02, 2013
The point of this article is, so far the scientists believed, that the spiral arms are typical for galaxies in certain stage of their evolution only: the young galaxies are spherical, those of averaged age are flat and the very old galaxies are elliptical again. But the Milky Way galaxy is very old, yet it remains spiraled and flat. It's evident, its spiral shape is characteristic for galaxies of certain size, not age. The very small or large galaxies like the Abel were probably never fully flat or structured into arms.
ValeriaT
1.9 / 5 (9) Apr 02, 2013
DarkHorse66
3.5 / 5 (8) Apr 02, 2013
@Zeph:
http://www.theatl...08873/2/

Just what does the Tozo parasite and crazy cats have in common with spiral galaxies?!?!?
I STRONGLY suggest that from now on, you open any chosen link and copy the address from INSIDE the article! That might just stop you from posting irrelevant or wrong stuff.
You REALLY need to check what you posting!!!!
DH66
Fleetfoot
5 / 5 (1) Apr 03, 2013
I hope that was meant to be funny. 8)


It was, and it was ;-)
Fleetfoot
5 / 5 (3) Apr 03, 2013
I STRONGLY suggest that from now on, you open any chosen link and copy the address from INSIDE the article! That might just stop you from posting irrelevant or wrong stuff.
You REALLY need to check what you posting!!!!
DH66


You presume he can tell the difference?
Fleetfoot
5 / 5 (3) Apr 03, 2013
The point of this article is, so far the scientists believed, that the spiral arms are typical for galaxies in certain stage of their evolution only: the young galaxies are spherical, those of averaged age are flat and the very old galaxies are elliptical again.


Nope, they know that the morphology depends on their formation history and their location within a cluster. Age is a secondary consideration but of course is generally correlated with the number of mergers they have undergone.
Fleetfoot
5 / 5 (3) Apr 03, 2013
Just to give the cranks a clue, the significance of this modelling is that it offers a modification or perhaps an alternative to the current 'density wave' theory:

http://en.wikiped...e_theory
GSwift7
3.3 / 5 (7) Apr 03, 2013
The funny thing is that it doesn't stutter, once the field is established, even it's initial source blowing apart (planetary nebulae) doesn't cause the field to diminish as long as there is energy present to sustain it.


That last bit is the downfall of any electric universe theory. The energy to sustain it is the problem. You would be seeing galaxies slow down and collapse due to conversation of energy/momentum.

Gravitation isn't a true force, and doesn't need energy input to sustain it. EM force would require a massive energy source, which doesn't appear to exist. Such an energy source should be observable with existing telescopes.
rubberman
1 / 5 (4) Apr 03, 2013
The energy to sustain it is the problem. You would be seeing galaxies slow down and collapse due to conversation of energy/momentum.


We do. THis is how you go from a quasar to the milky way...to whatever it will end up as in another 13 billion years.

Your massive energy source is all of the matter/energy in the galaxy. Gravitation makes spheres. Not clouds, arms or filaments or rings...essentially, structure.
GSwift7
3.7 / 5 (6) Apr 03, 2013
uh, that should have been conservation, not conversation; you know what I mean. lol

Anyway, you can't use any true force at these scales over billions of years or the structures wouldn't be sustainable. We can easily measure the magnetic fields inside our solar system, and Voyager is getting close to measuring the magnetic fields outside the solar system. There's no indication that any galactic magnetic field of the magnitude you suggest exists.

You can't use any true force to do what gravity does. Since gravity is a consequence of the effect matter has on time and space, it doesn't require any input to sustain it. It is the only thing capable of this. If you don't like gravity, then suggest some other self-sustaining force. EM cannot be self-sustaining, or you have just built the largest perpetual motion machine imaginable. Pure fiction.
TimESimmons
1 / 5 (6) Apr 03, 2013
spiral galaxy simulations created on a pc here:-
http://www.presto...ndex.htm
rubberman
1 / 5 (4) Apr 03, 2013

"You can't use any true force to do what gravity does. Since gravity is a consequence of the effect matter has on time and space, it doesn't require any input to sustain it. It is the only thing capable of this."GS

I agree with all of this except that I believe gravity is the effect matter has on other matter only. Time is a human construct, a tool we use to measure progressive events. Space contains matter, but matter's only effect on it is to occupy it.
Q-Star
3.6 / 5 (14) Apr 03, 2013
I agree with all of this except that I believe gravity is the effect matter has on other matter only. Time is a human construct, a tool we use to measure progressive events. Space contains matter, but matter's only effect on it is to occupy it.


That is just not true. Unless ya provide some model of gravity and spacetime that works better than Special Relativity and General Relativity. Matter not only occupies space, but actually shapes it. Relativity has held up to every test fairly applied to it. It only fails on the quantum scale and then only locally and the local "failures" average out to zero when applied to macroscopic scales.

Gravitation has been shown by experiment to influence EVERYTHING in spacetime. Both matter and energy (of every kind).
GSwift7
3 / 5 (6) Apr 03, 2013
That is just not true. Unless ya provide some model of gravity and spacetime that works better than Special Relativity and General Relativity. Matter not only occupies space, but actually shapes it


Just a minor point here: Cause and effect could be reversed in this case. It's entirely arbitrary, whether matter is the cause or if matter is the result of the distortion in space/time. Since we have zero knowledge of the mechanism that causes it, it could go either way. It's probably most accurate to say that there is a relationship, without assigning a cause and effect direction.
Q-Star
3.7 / 5 (12) Apr 03, 2013
That is just not true. Unless ya provide some model of gravity and spacetime that works better than Special Relativity and General Relativity. Matter not only occupies space, but actually shapes it


Just a minor point here: Cause and effect could be reversed in this case. It's entirely arbitrary, whether matter is the cause or if matter is the result of the distortion in space/time. Since we have zero knowledge of the mechanism that causes it, it could go either way. It's probably most accurate to say that there is a relationship, without assigning a cause and effect direction.


That's a very true distinction. But regardless of the direction, it was wrong of him to state that matter only affects other matter through gravitation. Or the reverse that gravitation only affects matter and not the other things we find in spacetime.
GSwift7
3 / 5 (4) Apr 03, 2013
That's a very true distinction. But regardless of the direction, it was wrong of him to state that matter only affects other matter through gravitation. Or the reverse that gravitation only affects matter and not the other things we find in spacetime


Yes, that's true. We measure the effect that gravity has on time every time we use a GPS device. If gravity did not effect electromagnetic waves, then we wouldn't need to adjust the GPS signals to account for it. Furthermore, the magnitude of the relativistic effect of gravity match exactly with calculated values, within the limits of our ability to calculate an exact value. The precision is astounding.

So, yes, he is entirely incorrect.
rubberman
1 / 5 (4) Apr 03, 2013
Electromagnetic waves are matter/energy. I don't disagree that gravity effects them, this falls well within the parameters of my statement about matter effecting matter (you know that whole interchangeability of matter energy thing). As far as matter shaping space, gonna need the original model of space before matter occupied it so that you can prove that the matter is "shaping" it. Lastly, the relativistic effects of gravity only match with calculated values on a galactic level when you allow for a 75% fudge factor that also must produce gravity to make the model work...quite the opposite of astounding precision....just sayin.
rubberman
1 / 5 (4) Apr 03, 2013
And I didn't say matter only effects matter through gravitation, I said that gravity only effects matter. Meaning I don't believe gravity has any effect whatsoever on empty space. Again, to prove that it does, you have to be able to tell the difference between normal empty space, and "gravitationally influenced" empty space. Logic dictates to perform this measurement you require means of detecting something other than an EM fluctuation....because thats still matter ya see.
Q-Star
3.3 / 5 (12) Apr 03, 2013
As far as matter shaping space, gonna need the original model of space before matter occupied it so that you can prove that the matter is "shaping" it.

We observe the "space before matter occupied it" all the time. It's the space between the things we take note of "out there".
Lastly, the relativistic effects of gravity only match with calculated values on a galactic level when you allow for a 75% fudge factor that also must produce gravity to make the model work...quite the opposite of astounding precision....just sayin.

"....just sayin" something doesn't make it so. I don't know where ya got that from unless ya are referring to "dark energy". Which has no bearing on the validity of Relatively until it can be isolated and tested experimentally.

If ya were referring to "dark matter", then ya should have claimed a much different "fudge factor" which by the by, has been dealt with by several independent methods of measurement/inference.

Present your explanation please.
Q-Star
3.3 / 5 (12) Apr 03, 2013
Logic dictates to perform this measurement you require means of detecting something other than an EM fluctuation....because thats still matter ya see.


Fields are NOT matter ya see. Forces are NOT matter ya see. And trying to conflate and commingle them to argue some "intuitive" point won't work because that is not the reality we are trying model.
rubberman
1 / 5 (4) Apr 03, 2013
I didn't say fields or forces are matter and wiki lists that 84% of the matter in the universe is DM, not 75 (i understated the degree of fudge). Again, I'm not talking about the total energy density which you somehow percieved I was even though I specifically named DM, just the mass content (which in reality can all be detected, just not whatever the reality is you think you are trying to model ). I am well aware of your job observing space both empty and occupied but your response proves nothing of the properties of empty space that change under gravity's influence. You basically just said we can see when it's empty and when something is there, it's not. Very profound.
Q-Star
3.3 / 5 (12) Apr 03, 2013
I didn't say fields or forces are matter


But ya did say just that. EM is something that ya said was matter. It is not, it is a field (or force.)

Matter is particles known as fermions. Forces and fields are mediated by particles call bosons. The only boson known which has any stability outside of a fermion nucleus is the photon. It is massless and is not considered matter. They share some attributes, but are not all of a kind. But most people accept at the fundamental level, photons are fields, wave packets, not an actual "particle". They are not part of the "matter" of the universe.

The terminology and distinctions are very important. A couple of artistic youtube videos is not a good model of reality. That's how Zephyr was lead down the wrong road years ago.
Fleetfoot
5 / 5 (2) Apr 03, 2013
Gravitation makes spheres. Not clouds, arms or filaments or rings...essentially, structure.


Wrong, gravitational collapse acts on the shorter axes of any shape more quickly. For a generic ellipsoid, it will first reduce it to a thin elliptical pancake shape, then to a filament and finally to a sphere. That's what we see in the large scale distribution of dark matter and in simulations. At the largest scales, that process is still ongoing. See for example:

http://www.mpa-ga...lennium/
rubberman
1 / 5 (4) Apr 03, 2013
EM isn't matter, it is a property of all matter (leptons, femions and yes, even photons). The physics you were taught told you photons are not matter but they are energy? THis must be what you mean by "not all of a kind" but regardless, in order for anyone to calculate a gravity induced spacetime curvature you would have to be measuring gravity's effect on SOMETHING besides empty space because as I understanded it empty space has no measurable properties, if this is incorrect please tell me what they are and how they change under gravity's influence. I only say this Q because we know that gravity effects photons, but why the assumption that it is all of the space in the vicinity of the object producing the gravity that curves, and not just the path of the photons that we are detecting?
cantdrive85
1 / 5 (6) Apr 03, 2013
Both Bostick's plasmoids and the particle in cell simulations performed by Anthony Peratt give a complete creation and evolution galaxies confirmed by observation. The simulations also can explain the various anomalous galaxies, such as ellipticals and irregular types in addition to the observed rotation, polar jets, synchrotron radiation, and other "mysteries" purported by the mainstreamers. Such a realization of the obvious would require astrophysicists to abandon the simplistic MHD models they use to explain the Universe and begin using models that actually match the observations. I know it's complex, but maybe even astrophysicist will catch on.
Fleetfoot
5 / 5 (4) Apr 03, 2013
I agree with all of this except that I believe gravity is the effect matter has on other matter only. Time is a human construct, a tool we use to measure progressive events. Space contains matter, but matter's only effect on it is to occupy it.


In the gravitational bending of starlight by the Sun, half the angle comes from bending space and half from bending time. That's why GR produces a prediction that is double that of Newton's Law. In general, it is almost impossible to reconcile presentism with GR.
rubberman
1 / 5 (5) Apr 03, 2013
Fleet, I use those exact same illustrations as evidence that it isn't gravity that produces the structures because I don't need DM to be in there to explain why it looks the way it does. The day we actually find DM I'll eat my words with barbecue sauce on them.
Q-Star
3.2 / 5 (11) Apr 03, 2013
I only say this Q because we know that gravity effects photons, but why the assumption that it is all of the space in the vicinity of the object producing the gravity that curves, and not just the path of the photons that we are detecting?


I think we are on verge of an agreement if I understand your question. It is not a force from the massive object acting on the photon. The warping of spacetime around the massive object is the gravitational effect ya see as the photon moves through space.

The photon is not "attracted", it's line of propagation is geodesic ie,warped. We observe this directly. We also observe that when the photon is traveling in spacetime where there is no massive object, that's it's path is flat, straight, euclidean.

If ya were "riding" the photon, ya would only see that ya are moving in a straight line regardless of whether ya were near a strong gravitational field or in the complete absence of a gravitational field.
Fleetfoot
5 / 5 (1) Apr 03, 2013
But most people accept at the fundamental level, photons are fields, wave packets, not an actual "particle".


Anyone who has looked at QM will say that there is no fundamental difference, all particles act like waves under the right circumstances. For example electrons show their wave nature in the double slit experiments.

They are not part of the "matter" of the universe. ... The terminology and distinctions are very important.


They are but unfortunately "matter" and "radiation" aren't as well defined as other terms. We all probably learned that there are three kinds of radiation you meet in the lab: alpha, beta and gamma, but helium nuclei and electrons are classified as matter in the early universe.
Q-Star
3.3 / 5 (12) Apr 03, 2013
They are but unfortunately "matter" and "radiation" aren't as well defined as other terms. We all probably learned that there are three kinds of radiation you meet in the lab: alpha, beta and gamma, but helium nuclei and electrons are classified as matter in the early universe.


Which is why I am very careful when I use the word "radiation". I try to use it as a "process" than a "thing". When forced to use it, I try to be consistent by including a qualifier such as EM radiation, or beta radiation, cosmic radiation, etc,,,

As to the wave-particle thing, the model used should fit the phenomena being addressed. Unfortunately many on this forum don't know when or how to switch back and forth.

Same with gravity, force? Fine if ya only are using slow heavy objects.

Gravity, field? That's where Einstein advanced things so significantly, he realized, unlike Newton, that photons were massless so an attractive force wouldn't work. But a field would work most handily.
Fleetfoot
5 / 5 (1) Apr 03, 2013
Fleet, I use those exact same illustrations as evidence that it isn't gravity that produces the structures because I don't need DM to be in there ...


That's fine but I was simply correcting your incorrect statement. This is supposed to be a science site so making statements which are the opposite of what the science says isn't helpful.
rubberman
1 / 5 (4) Apr 03, 2013
Fleet, I use those exact same illustrations as evidence that it isn't gravity that produces the structures because I don't need DM to be in there ...


That's fine but I was simply correcting your incorrect statement. This is supposed to be a science site so making statements which are the opposite of what the science says isn't helpful.


OK...you do realize that at some point alot of what we have discovered/observed scientifically has been very different from what was once believed to be accurate right? Your link showed the structures as we have observed them, the physics behind those structures is nowhere near settled as far as the mainstream is concerned, meaning I am scientifically confident that the BBQ sauce is staying in the fridge. The second they programmed the simulation with a variable representing the PROPOSED gravitational effect of DM so that it could explain the observation they stopped helping science. I agree 100% with you about wave energy.
rubberman
1 / 5 (4) Apr 03, 2013
"Gravity, field? That's where Einstein advanced things so significantly, he realized, unlike Newton, that photons were massless so an attractive force wouldn't work. But a field would work most handily."

Also agree totally with this Q.
(accepting relativistic mass excluded?)
GSwift7
2.7 / 5 (7) Apr 03, 2013
The day we actually find DM I'll eat my words with barbecue sauce on them


Then you need to get a fork and a napkin ready. There's a story about finding dark matter on Physorg today. Apparently, they are having success with the dark matter detector on the ISS, and the results are quite good. I'm waiting to see a more comprehensive report though. As usual, the physorg story is a bit sketchy. It says something about an abundance of positrons.

As for the difference between an EM field and matter: Any field is merely the difference between potentials over a distance. An EM field is the difference between EM potential over a distance. The strength of the field is not proportional to the absolute energy at either location, rather on the difference between them. So the strength of an EM field, and therefore the force exerted by an EM field, is not equivalent to mass as implied by the E=mC2 equation. Besides, that's GR, which you are trying to throw out.
cantdrive85
1 / 5 (6) Apr 03, 2013
It's ironic how the relative success of experiments to discover either DM or aether leads to completely different outcomes. Although still not detected after numerous efforts, DM is still held as a very well supported hypothesis, whereas aether although still not detected is cast aside without further consideration. GS, the presence of the extra positrons could also be evidence of the matter being broken down into the constituent particles that make up the aether such as neutrinos, etc...

cantdrive85
1 / 5 (6) Apr 03, 2013
"... Lorentz, in order to justify his transformation equations, saw the necessity of postulating a physical effect of interaction between moving matter and æther, to give the mathematics meaning. Physics still had de jure authority over mathematics: it was Einstein, who had no qualms about abolishing the æther and still retaining light waves whose properties were expressed by formulae that were meaningless without it, who was the first to discard physics altogether and propose a wholly mathematical theory..." Herbert Dingle, Science at the Cross-Roads.
ValeriaT
1 / 5 (6) Apr 03, 2013
It's ironic how the relative success of experiments to discover either DM or aether leads to completely different outcomes
Because the aether concept was heavily misunderstood even with aetherists itself. Even the most aether dedicated "crackpot" of all times T.J.J.See did fight with Oliver Lodger for his dense aether model. He wasn't abble to understand, that the sparse aether PERVADING space cannot mediate the energetic waves or forces - so it must FORM the space instead. Whole generations of physicists handled the luminiferous aether concept like some sparse gas coexisting with light waves, instead of forming them. After all, the contemporary physicists cannot understand it even today, after one hundred of years... The (lack of) understanding of some trivial connections about reality defies the understanding.
rubberman
1 / 5 (4) Apr 03, 2013
GS, The strength/size of an EM field is dictated by the motions of the matter/energy that generates it, the energy available to sustain it and how much of it there is. Re DM and the ISS, if they say they found it, I'll chow down. If they say that positrons are evidence for DM without explaining how they are produced, and precisely why they indicate DM detection, I'll treat it exactly how I treat all DM claims right now... yet another facepalm and a chuckle at watching some of the smartest people on the planet being duped into chasing their tails because of application of flawed logic. The water ripple duck pond is more based in reality because water ripples and ducks exist. As for Dm, let the snipe hunt continue!
GSwift7
1.8 / 5 (5) Apr 03, 2013
GS, the presence of the extra positrons could also be evidence of the matter being broken down into the constituent particles that make up the aether such as neutrinos, etc


In this sense, you are calling DM aether. If there is some mass that is breaking down to create positrons, then that mass is the dark matter we have been looking for. It very well could be neutrinos. They said nothing about the source in the above article. I would guess that more info about the energy of the positrons in question will limit the possible sources. Positrons at certain energy levels can only be created by certain means, therefore eliminating others. The discovery above is a sign that we will be able to finally build a detector that can answer exactly that question, if I'm understanding the situation correctly.

BTW, you know you posted this in the thread about spiral galaxies, right?
GSwift7
2.6 / 5 (5) Apr 03, 2013
GS, The strength/size of an EM field is dictated by the motions of the matter/energy that generates it, the energy available to sustain it and how much of it there is


Extremely energetic matter, like that in the sun, with only a small difference in electromagnetic potential over a given distance, will create the same field strength as low energy matter in your bedroom with that same difference in electromagnetic potential over the same distance.

The engergy/mass density in the sun will be much higher than the energy/mass density in your bedroom, despite the magnetic field strength being the same. The two terms are not interchangeable. You cannot equate magnetic field and energy/mass density.

You can create extremely strong EM fields with low density matter and have extremely dense matter with zero EM field. Or the opposites.
ValeriaT
1 / 5 (6) Apr 03, 2013
In this sense, you are calling DM aether
DM is very sparse, it cannot serve as a luminiferous aether even in your wildest dreams. After all, the light apparently doesn't require any dark matter for its spreading between galaxies. IMO you're just confusing the aether model. In history many concepts were labeled as aether, although they had nothing in common with concept of particle environment. For me the aether is geometric concept only - it doesn't contain any other attributes, fitted to dark matter or whatever else behavior. Aether is not white, dark or magnetic.
cantdrive85
1 / 5 (6) Apr 03, 2013
What are the geometric properties of nothing?
Fleetfoot
5 / 5 (3) Apr 03, 2013
Your link showed the structures as we have observed them, the physics behind those structures is nowhere near settled as far as the mainstream is concerned, ..


There's no doubt at all in the "mainstream" about the primary mechanism behind the large scale structure, that part is relatively simple. It is the later effect of dissipative collapse when the early galaxies and AGN formed that becomes extremely difficult due to 'feedback'.

meaning I am scientifically confident that the BBQ sauce is staying in the fridge.


In terms of the specific properties of dark matter, you may well be safe for some time ;-)

The second they programmed the simulation with a variable representing the PROPOSED gravitational effect of DM so that it could explain the observation they stopped helping science.


The density used is that determined by the overall flatness (e.g. from WMAP, etc.) and from studies of clusters velocity dispersion, it is not fitted to the LSS observations.
Fleetfoot
5 / 5 (4) Apr 03, 2013
It's ironic how the relative success of experiments to discover either DM or aether leads to completely different outcomes. Although still not detected after numerous efforts, DM is still held as a very well supported hypothesis, whereas aether although still not detected is cast aside without further consideration.


Lorentz's aether theory was on a par with special relativity but had to be discarded when Eddington's observation of gravitational bending of light showed the Newtonian prediction was wrong and GR was right. Since GR simplifies to the Minkowski Metric far from a mass, the geometry of SR is unavoidable so the aether was left with no effects to explain.

DM is similarly supported by observation from the overall flatness of the universe, cluster virial dispersion velocities, X-ray observations, large scale structure, galaxy rotation curves and gravitational lensing, all of which lead to the same conclusion.
GSwift7
2.7 / 5 (7) Apr 04, 2013
DM is very sparse, it cannot serve as a luminiferous aether even in your wildest dreams. After all, the light apparently doesn't require any dark matter for its spreading between galaxies. IMO you're just confusing the aether model.


Valeria, I think you need to read the comment again. I wasn't saying this is true. I was responding to another incorrect comment from cantdrive. I was pointing out that HE was equating DM with aether. I do not support any aether theory, but if I did, cantdrive's comment doesn't fit any of the aether theories. Aether theory is meant to eliminat the need for DM. Cantdrive's comment just confused five or six different theories and mixed them all up in some strange psychotic comment wonderland Universe theory. Cantdrive has a habit of coming up with the most outlandish and whimsical versions of theories, doesn't he? I think I just coined a good term "Psychotic Comment Wonderland Universe" theory. I like that.
GSwift7
2.7 / 5 (7) Apr 04, 2013
DM is still held as a very well supported hypothesis, whereas aether although still not detected is cast aside without further consideration


The subtle difference here is that while DM hasn't been detected, it also hasn't been ruled out. On the other hand, aether is discarded because it HAS been ruled out. There are several basic reasons that aether CANNOT be correct. There's no way to wiggle around basic facts of observation.

DM is a very strong leading contender amongst the options which have not been ruled out. Some kind of matter which we have not yet detected would fit all of our observations. That is why it is such a strongly supported idea. Besides, the debate will likely be over within a decade anyway. There's not really any rush to solve this. Get a bag of popcorn and enjoy the show while we try to figure it out, and stop wasting time with aether or electric theory, which are both ruled out by multiple observations.

More news stories

Meteorites yield clues to Martian early atmosphere

(Phys.org) —Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published ...

Let's put a sailboat on Titan

The large moons orbiting the gas giants in our solar system have been getting increasing attention in recent years. Titan, Saturn's largest moon, is the only natural satellite known to house a thick atmosphere. ...

Red moon at night; stargazer's delight

Monday night's lunar eclipse proved just as delightful as expected to those able to view it. On the East Coast, cloudy skies may have gotten in the way, but at the National Science Foundation's National Optical ...