Topic: Dark Matter Warping Milky Way

[Dracho]

Dark matter may affect our galaxy’s warp
Milky Way’s disk flexes in response to satellite galaxies’ loop-the-loop

By Ker Than
Space.com
Updated: 7:40 p.m. ET Jan. 9, 2006


A slow-motion collision between mysterious dark matter and two of the Milky Way’s galactic neighbors may be causing our galaxy to warp like a vinyl record left out in the hot sun, scientists announced Monday.

Astronomers have puzzled over the Milky Way’s warped shape for nearly half a century but have been unable to provide a convincing explanation for what might be causing it.

The warp is most clearly visible in a thin disk of hydrogen gas that extends across the entire 200,000-light-year diameter of the Milky Way.

Viewed sideways, half of the hydrogen disk appears to stick up above our galaxy’s plane of stars and gas, while the other half dips below the plane for a bit and then rises upward again farther away from the galaxy’s center.

Old theory, new twist
One early explanation was that the gravity from two neighboring dwarf galaxies known as the Magellanic Clouds was causing the Milky Way to warp as the pair moved in their 1.5-billion-year orbit around our galaxy.

This hypothesis was later dismissed after it was shown that the combined mass of the two dwarf galaxies is only about 2 percent of the Milky Way’s enormous hydrogen disk — not nearly enough to cause the warp.

Now researchers from the University of California at Berkeley have revived this old theory with a new twist.

Using computer models, the team showed that the Magellanic Clouds could warp the shape of the Milky Way, but only if they were moving through a thick halo of hypothetical dark matter.

Dark matter can’t be directly observed because it neither emits nor reflects visible light or other electromagnetic radiation. However, its presence has been inferred from the gravitational effect it has on visible matter such as stars and galaxies. Astronomers believe that dark matter may make up as much as 90 percent of the mass in the universe.

The computer model suggests that if the dwarf galaxies were moving through dark matter, then their gravitational influence would be enhanced to the point where they could cause warping similar to what has been observed.

The model also revealed another surprise.

“We often think of the warp as being static, but this simulation shows that it is very dynamic,” said Leo Blitz, an astronomer from UC Berkeley who was involved in the study.

The model indicates that as the Magellanic Clouds interact with dark matter, they create vibrations that cause the Milky Way’s hydrogen disk to oscillate. The overall effect is reminiscent of the edges of a tablecloth flapping in the wind, the researchers said.


Since many other galaxies are also warped, the researchers believe similar processes might explain their shapes as well.

The study was detailed here in a press conference at the 207th Meeting of the American Astronomical Society and will be published in an upcoming issue of the Astrophysical Journal.

http://www.msnbc.msn.com/id/10779532/

[Bonk]

Not to rain on your parade, but I really do tire of theoretical "science". It serves only to damage the reputation of genuine empirical science. I suspect that capitalism has adversely affected the aims of science as it has governance. 

[Dracho]

Rain on my parade?  Hell Bonk, when I first saw the headline I thought it was an article about a new candy bar..

[Tus-XC]

Not to rain on your parade, but I really do tire of theoretical "science". It serves only to damage the reputation of genuine empirical science. I suspect that capitalism has adversely affected the aims of science as it has governance. 

Bonk,

All science is theoretical by nature, and can only be verified by duplicatable expiraments.  Simply throwing out a theory because doesn't fit your view of science is quite interesting since the only way to emprical data is to do expiraments in the theoretical science.  Hell if we stuck by such a narrow view of science i think we would still be the in the dark ages and still thinking the world was flat (hey, during that time period it would be relativly the same thing as your refernce to theoretical sciences and empirical science... i mean think about it... it took hundreds of years just to get to keplers laws)

[Bonk]

No, a hypothesis is still necessary for the implementation of the scientific method, of course. However, if your hypothesis cannot be tested by experiment, it is not science but rather philosophy.

I am just continually offended by philosophy and cosmology being passed off as genuine science, marring the reputation of real scientists.

It is all about funding unfortunately, that is my point.

There is nothing wrong with thought experiments, but science it is not. 

[Tus-XC]

no it would be a theroy still, especially if it hasn't been proven or disproven by an expirament.   and yes sadly it is about money, if it wasn't then maybe funding wouldn't be an issue and we could get further

[Bonk]

A philosophical theory. Scientific theories can be tested by experiment with phenomena that are known to exist. One can theorise about superstrings and dark matter all one likes, but neither is known to exist, thus cannot be experimented upon.

Gravity is a good example, because while it still is essentially a mystery and still a theory, its effects are measurable and its behaviour can be empirically determined with objects and apparati that actually exist. Using the theory of gravity to explain an observed property of matter (our galaxy) by interaction with a hypothetical object (dark matter) is just plain invalid, a logical fallacy.

I suspect that too many journalism graduates with no science background are responsible for a lot of the populist spin on "science" in the media these days.

edit: People like Natasha Stillwell on Discovery's Daily Planet... she makes me want to puke.    Totally unqualified. Unlike Jay Ingram, I have no idea how he puts up with her... I mean maybe if she was the least bit decorative...  Biologists... sigh... 

[KBF-Kapact]

Not to rain on your parade, but I really do tire of theoretical "science". It serves only to damage the reputation of genuine empirical science. I suspect that capitalism has adversely affected the aims of science as it has governance. 

Do you not believe in dark matter, or do you not believe that it is the cause of the warping of the Milky Way? (I always knew the place was warped, I just didn't know why  )

[Bonk]

I've got dark matter in my bowels!    Maybe that's why I'm so warped. 

[Dracho]

One of you guys who knows the math might know the answer to this:

Dark matter is predicated on the notion that all of the matter in the universe does not have enough mass to explain the effects fo gravity.  What if there is no such thing as "Dark Matter", but what we think is Dark Matter is actually normal matter accelerated beyond the speed of light (yes I know Mr. Einstein).

Think about the compression wave of a sonic boom.  What if matter can be accelerated beyond the speed of light and the space-time of the universe were compressed in a wave just like a sonic boom?

It would explain:

Why you can't see it (it's moving faster than light so the space-time compression makes it "invisible"..
and Why there is more gravity than there should be..

[Bonk]

Interesting thought! Not sure on the math, as it would require new math as I see it.

The problem that I have with the "need" for dark matter is that it is based on the observation of light that was generated many millenia  ago. We need to know what is happing now, not then, and this may never be possible.

Your idea is not so far from my idea that if there is indeed missing mass in the universe, it may be mass/energy under the control of an intelligence.

The recent confirmation of the event horizon surrounding black holes makes the likeliehood of matter or energy naturally moving beyond the speed of light pretty improbable, otherwise, this "event horizion" would not exist. (?)

[Dracho]

Interesting thought! Not sure on the math, as it would require new math as I see it.

The problem that I have with the "need" for dark matter is that it is based on the observation of light that was generated many millenia  ago. We need to know what is happing now, not then, and this may never be possible.

Your idea is not so far from my idea that if there is indeed missing mass in the universe, it may be mass/energy under the control of an intelligence.

The recent confirmation of the event horizon surrounding black holes makes the likeliehood of matter or energy naturally moving beyond the speed of light pretty improbable, otherwise, this "event horizion" would not exist. (?)

Unless the "event horizon" is actually the leading edge of the "gravitational shock wave" and what we are seeing is actually centrifugal force at C+1.

An aeronautical engineer can tell you great stories about the F-86 Saber (Digression alert, but point illustration):

In the Korean war the MIG-15 was eating the lunch of our prop planes and the Shooting Star Jet the navy used.  The only way our jet could match it was to entice it into a dive.  For some reason it would lost maneuverability near the speed of sound.

What we now know is that the compression wave created at Mach1 would cause air to disrupt across the rear control surfaces.  So, we built the F86 Saber with the rear elevators far enough up that the shockwave did not affect the control surfaces.  Viola, we could do a Mach1 dive and eat the MIG.

I think, based on the properties of light, that when something goes beyond the speed of light that rather than the Enterprise E flash, we'd probably see it simply disappear. 

However, if it's possible, then how does one slow back down (or can one)?  Or, is the physical universe merely matter than has slowed below a normal translight state?  Rather than speeding things up, we might be the manifestation of a slowing down.  It certainly explains me in the mornings..

[Dracho]

Here is an interesting new theory on the magnifcation of gravity.

Gravity bends light, but can it also magnify itself?
Einstein made his fame with the idea that gravity bends light, a notion proven by observations of the planet Mercury in 1919. Once a crazy idea, it has shaped how scientists think about gravity ever since. Even now, astrophysicists aim telescopes at the violent regions around distant black holes, hoping the intense pull of those collapsed stars will fully reveal gravity's secrets. But up close in our solar system, a certifiably "crazy idea," according to National Science Foundation cosmologist Michael Turner, may offer a test of Einstein's theory of gravity.
 
  Albert Einstein's theory of General Relativity may get tested by one cosmologist's "crazy idea." 
AP

The idea comes courtesy of astronomer Robert Nemiroff of Michigan Technological University, who proposed it at last week's American Astronomical Society meeting in Washington, D.C. We know gravity bends light, but he proposes that "gravity might magnify itself," as well. If true, he suggests that regions of magnified gravity may exist in our solar system near the orbit of the planet Neptune. These "gravitational hollows" — or spikes of magnified gravitational pull — would exist at the point where the sun's gravity focuses the gravity from a distant star or black hole, much like a magnifying glass focuses light at a certain point. He compares how gravity looks around a star to the looks of a sea urchin, with hollows radiating away from the sun like sea urchin spines.

   Read more   
 
For a look at an abstract on the topic of gravity lensing, follow this link from the American Astronomical Society meeting.
 
 
 
 
 
How do you test this idea? Fly a spacecraft though a region of magnified gravity and see if it slows down. The largest hollow would come from the giant star Sirius, whose gravity, if magnified, would create a hollow almost 40 miles wide. An atomic clock like the ones made now by the National Institute of Standards & Technology would be sensitive enough to pick up the difference in travel time, Nemiroff says. Much smaller hollows would be created by the pull of Polaris, the North Star, and the massive black hole at the center of the Milky Way galaxy.

Nemiroff says he has polled experts on Einstein's theory of gravity, better known as General Relativity, and they aren't certain whether gravity could bend gravity like it bends light. Turner is dubious, but adds "We know Einstein didn't have the last word on gravity. We're all looking for an idea crazy enough to be correct and this definitely is a crazy idea." Also cautious is astrophysicist Michael Martin Nieto of Los Alamos National Laboratory who says, "It is fun to think about, but for now Nemiroff's comments are intuitive," and not formally defined enough for other physicists to critique.

Still, Nemiroff says either way his idea merits investigation. If true, it would shake up our understanding of General Relativity and if false, it might tell us something about how gravity will perform around those distant black holes that cosmologists plan to investigate in coming decades.

http://www.usatoday.com/tech/science/columnist/vergano/2006-01-15-einstein-gravity_x.htm?csp=15

[Death_Merchant]

One of you guys who knows the math might know the answer to this:

Dark matter is predicated on the notion that all of the matter in the universe does not have enough mass to explain the effects fo gravity. 

...and that's the deal

either
a) our understanding of gravity is flawed
b) or there is something out there we can't account for (called "Dark matter" because "weird mystery crap" sounds stoopid)


So physicists reasoned that fewer laws of physics get all a' busted up if "dark matter" exists.
So lets look for & theorize about "dark matter"

[Nemesis]

We know gravity bends light, but he proposes that "gravity might magnify itself," as well. If true, he suggests that regions of magnified gravity may exist in our solar system near the orbit of the planet Neptune. These "gravitational hollows" — or spikes of magnified gravitational pull — would exist at the point where the sun's gravity focuses the gravity from a distant star or black hole, much like a magnifying glass focuses light at a certain point. He compares how gravity looks around a star to the looks of a sea urchin, with hollows radiating away from the sun like sea urchin spines.

A possible explanation for comets being deflected towards the sun from the Oort cloud without having to have any undiscovered giant planets out there.

Still no explanation for the 3 probes out there that are off course.