Posted on 08/21/2006 6:13:30 PM PDT by vikingd00d
Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA's Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter.
"This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
These observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.
"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."
In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.
The team was granted more than 100 hours on the Chandra telescope to observe the galaxy cluster 1E0657-56. The cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped cloud of hundred-million-degree gas. The X-ray image shows the bullet shape is due to a wind produced by the high-speed collision of a smaller cluster with a larger one.
In addition to the Chandra observation, the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done by measuring the effect of gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity.
The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.
"This is the type of result that future theories will have to take into account," said Sean Carroll, a cosmologist at the University of Chicago, who was not involved with the study. "As we move forward to understand the true nature of dark matter, this new result will be impossible to ignore."
This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.
"We've closed this loophole about gravity, and we've come closer than ever to seeing this invisible matter," Clowe said.
These results are being published in an upcoming issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass. For additional information and images, visit:
http://chandra.nasa.gov
yes, I am aware of the theories on motors, and also some of the arguments.
I got into a lot of that stuff when I was maintaining some electric cranes that use DC Mag Amp systems essentially based on loosely on submarine drive controls and coupled with AC motors....
The argument were over the Fields and how they were able to modify the AC waveforms to control the motor speeds and torque.
At the time, we really did not have all the answers on how the interactions worked, but they did. Fun to argue at times...
And then there is the hole theory with silicon transistors. Something we have used for 70 or more years, yet the theorists were still arguing whether the electron came out of the hole or went into it, or something to that effect.....LOL... it is just anecdotal to understanding gravity.
Anyway, my primary questions are focused on gravity and mass and all that it entails, and not electromagnetism, which we understand well as you said, yet in some areas of the physics, we still have heated arguments, or at least did about 8 years ago when I retired.
What we do know, is that we don't know a lot, and new questions are arising frequently.
It's certainly no disgrace if electricians don't understand the modern theory, because it's just not relevant to what they do. The fact that circuit diagrams represent current as flowing in the opposite direction to that in which electrons actually drift makes no difference to making the motors run and the lights go on.
As for gravity, what this result shows is that Einstein's nearly 100-year-old theory of gravity still works perfectly well. Some people thought that certain discrepancies in astrophysical measurements were showing us that Einstein's theory was wrong, but it turns out that the matter isn't what (or where!) we thought it was. The theory was making the correct predictions all along.
This is why most wire was solid.
We eventually derated the solid wire construction and uprated the stranded, which carried more current with less copper.
The last technical class I had on that subject was in the late eighties, when the phrase, "not completely understood" was used.
Praytell, do you know why?
Specifically why electrons flow on the surface, and not so much down the middle of a conductor....?
That must be car wiring, we work with AC, and it goes both directions. Most electricians, these days, do get training in DC controls, but don't spend a lot of time with theory, or DC circuitry.
I am a bit different as electricians go, because I started in electronics, and moved to electricity.
I once repaired televisions and the like. i still like to dabble with board level stuff and amplifier design.
Most master electricians don't venture into that field, because there is no need to. There is little money in it anymore.
My questions on gravity are not related to what it is or how to measure it. It is related to how it manifests it's self.
What sort of energy is the field attraction comprised of, and how can we manipulate it and by doing so, create it artificially.
I know the theory, and I don't pretend to understand them as it is not my field, but I have never met anyone who claims to know everything about gravity. If that were the case, why are we still using rocket propulsion and making a bird that has to fall out of orbit and endure reentry heat to land like a jumbo jet.
This is what my questions are.
So are you saying we know this!
Placemarker
If it isn't an ether, is it an ester? Maybe a ketone?
I don't really "get" dark matter. Having spent time in caves, I don't consider normal matter "luminous", unless excited.
Is it not just 'regular' matter that is cold, as in near or at zero K?
Can you enlighten?
I should have read further through the posts.
If I go in to a thick forest in the middle of the night and turn out all the lights and I can not see my hand the dirt on the ground is dark matter is it not?
Gravity is the curvature of spacetime. One of the consequences of this is that the dipole moment of the field is constrained to be zero. This poses a problem for gravitational engineering: all of our electromagnetic technology exploits the electromagnetic dipole interaction, but while there are positive and negative charges, there is only positive mass and energy. (Even anti-matter has positive mass.)
So you won't find anti-gravity, artificial gravity gravitational wave communicators, or the like. The field just doesn't work that way.
I know the theory, and I don't pretend to understand them as it is not my field, but I have never met anyone who claims to know everything about gravity. If that were the case, why are we still using rocket propulsion and making a bird that has to fall out of orbit and endure reentry heat to land like a jumbo jet.
Whatever the next theory of gravity has in store for us, it can't repeal the conservation of momentum and energy. We use rockets because, in order to accelerate, you have to have something to push against (conservation of momentum). Things heat up on reentry because the orbital energy has to go someplace (conservation of energy).
You: AFAIK, it would be the same as our galaxy encountering a galaxy of visible matter of equal mass:
[Slaps forehead] Ah, of course!
The interesting thing is that we wouldn't see it coming. Or for the most part even realize it if were in the middle of such an event.
When my imagination is turned on, (happens occasionally), I alway get this feeling that we are not seeing the tree clearly because the Forest is blocking the view.
I understand that conservation of energy is a given, and that the tremendous amounts of energy needed to mimic and create artificial gravity may theoretically prevent it's creation. But i cannot get over a feeling that I have always had, that tremendous amounts of literally free energy have been at our fingertips, yet we cannot realize it.
So I continue to try to find out where, and what it might be. If found, conservation of energy may well be a problem no longer.
Sometimes it pays to skip the first day of a science thread.
.... most of which cannot be answered until they come up with some idea of what the "dark" matter is made up of, which is probably a job for the particle physicists.
Physicist; do you have any info on lines of research trying to determine what the dark matter is? What do they know it is is NOT made out of?
It is not made out of any known type of particle. It can be bound gravitationally, as we see here, but it does not form clumps like stars or dust grains.
As for the black hole question, as luck would have it, I answered that before.
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