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
If dark matter only interacts through gravity, what is the light coming from to determine where the dark matter is located?
Sounds like there are still research opportunities here.
Hmmmmmm, I don't think that is the explanation for the surface flow. It explains the basic phsysics of the flow of electrons, but not the type of flow and why it behaves in specific ways..
The logical explanations have been varied, but the flow of electricity basically starts out as a turbulent and chaotic flow, just as a liquid flows within a pipe. As time progresses and we add Milli seconds to the event, the chaos that tends to expand outward creates a laminar flow on the outside of the conductor, or in liquids, the pipe. laminar flow allows for a more efficient flow rate and less resistance. This is why multi-stranded conductors are less resistive, creating less heat than the solid variety.
This is the layman's explanation that we use in the field where we know that electricity, like a liquid, seeks the path of least Resistance on it's own. And no, we have not known this for a hundred years. And no, it is not that simple. we are constantly trying to improve wiring methods, and the field procedures we use to improve the process, just as they do in fluid mechanics by improving valve and piping designs.
Efficiency is the game, and with improved efficiency we lower costs and reduce weight. we are constantly learning, and nobody can tell me that we know all there is to know. Except maybe a engineer, because they tend to do that all the time.....:-)
There is constant friction between the field and the guys with the pencils...There is no formula, that I have ever been aware of that describes and can predict the efficiency of the flow, but over time we have made note of the better wire and cable designs as far as number of conductors on the bundle vs the conductor size required. wire engineers have this at their figertips, and I simply pick from the best quality based on practical experience.
I am the guy in the field who has to build the stuff the engineer conceives on paper...I usually do a pretty fair job of smoothing out the bumps between concept and reality, but it is not easy. Only 35 years ago, we had this all wrong, and were building electrical distribution systems that were faulty and could have been much better. We are constantly improving, and by no means do we understand it all.
That is why I responded to your claims. The mind set should be that we know that we don't know everything. Not that we do....Electricity is certainly no exception.
As for the black hole question, as luck would have it, I answered that before.
Thanx.
We are not on the same page here, which is not unusual when I make a statement on the thread that a engineer wants to parse, which is what they do with a BLT sandwich or anything that anyone says.
I simply mentioned the hole theory. Nobody really cares which way a electron moves in a circuit diagram, because you just need to pick one way or the other to make calculations. In the field, it helps if you wire the power supply correctly.
Here the deal! I had a exchange up the thread with another FReeper, in which we marveled at the amount of things we know and more importantly, what we don't know.
You guys jumped in and blasted the statement referencing what we don't know, as if to say we know all we need to know and have known it for a while.
My contention holds that we don't understand enough to pick our own nose on a variety of subjects. Only a fool would say we know enough, when in fact, we only know enough to be dangerous.
Your commentary on electrical flow is a great example. Electrons move radially, only because of the atomic structure of the conductor. It is the way the atoms are stacked that causes the radial movement, and the end result that a signal applied to one end takes time to get to the other because it travels a much greater distance then that of the wire length. You think we know it all, yet we have yet to produce efficient conductors without dicking around with gold and copper.
Currently, much work is being done to make better conductors that are constructed similar to a polymer chain and will increase signal speed dramatically. We don't yet know how. We don't yet know a lot of things, like how to transmit raw power wirelessly. We cannot even create efficient and safe power economically without putting in more than we take out, excluding nuclear.
So here I simply state the obvious and you all want to parse it.
You cannot parse the truth. The truth is, we are in the dark ages on many levels of development.
All the hundred year old understandings notwithstanding.
The truth is, that we should know that we don't know a great deal....
That's the truth.....Parse it......If you can.
One moving faster than another? Two galaxies with an intersecting trajectory?
I'm beginning to tire and I don't tire easily.
I was about to go back and reexplain to you what and why I said what I said about the current direction comment, which quite frankly came out of the blue, and then you do more of it.
So I won't.
What you claim to be my misunderstanding has to do with the neat little box that some of you fellows seem to build around your fragile egos.
This for example........Again, you have confused engineering and physics. Is it hard to build an efficient conductor? Who cares? That is irrelevant to our physical understanding of ideal (and imperfect) conductors.
My post was not confined to engineering. You confined it so it would fit in your little box! A tiny box from my perspective. I was addressing current inadequate conductor properties which very well could involve quantum physics or any number of sciences.
I find this highly irritating when I am wide open and you cannot get out of your box for ten friggin seconds to do anything but insult me for what you mistakenly perceive I said.
I don't and never have confined myself to such a narrow scope as to be so arrogant, but I find it common in your field and that of engineering. I don't know what causes it, but it holds us back.
Get out of your box once and while. Think out side. The world may be untidy, but believe me, you will not achieve squat without digging into the pile.
Maybe that analogy is beyond your perception as well. for example this:We cannot even create efficient and safe power economically without putting in more than we take out
To that you said.....Ever hear of a little law called the conservation of energy?
I don't get it. I thought the sentence was perfectly constructed and clear. I indicated that I do understand conservation of energy and that I am aware of the energy losses we suffer daily because of our outmoded transmission abilities. "More than we take out", certainly does not lead anyone to assume I think there is some way to get more than we put in.
To assume that you would have to believe that I am a simpleton! That I believe in the holy grail! A machine that puts out more energy then it consumes.
The truth is, our energy losses due to transmission are very significant. A large part of it goes up in heat.
Now one would assume when talking to a electrician, that he might have some idea of what he is talking ABOUT. You have done this same leap of logic (sarcasm) for everything I have said on this thread.
The purpose of this reply is to let you know, that I don't like it and I won't put up with it for a new york second. I occasionally learn something on this forum. But not today...no sir.
Since your field is physics, I thought maybe I could learn a little about using quantum physics to transmit signal data over vast distances. Maybe tap the cosmic energy that is all around us to create power on the spot. But you definitely cannot get there from here, and no new theories will ever be written when physicists are in a box. Have a nice day.........
Huh? That's where the free electrons are. The ones inside are all shared by multiple atoms, while the ones on the outer surface are free to skip from one to another.
No?
It's related to surface area...which is related to gauge.
At a glance, I'd say that for copper the function of ohms per thousand feet is something like subtracting 10 from the gauge, dividing that by 10, and taking the antilog of the result. That seems to get you pretty close.
As of now, we have a free electron theory, a radial movement theory, and my own chaos theory, and that is just three people.
This is what they instructor told me some twenty five years ago, that there was not agreement.
But, that was not the subject of the thread, and I digress. I made a mistake and pointed out that we don't know what we don't know, and apparently I have learned that we actually don't even know that we don't know.:-)
Have a nice day......
As a electrician, I deal with A/C currents, not DC. In DC, the flow is pretty much equal throughout the cross section of the wire. It is in A/c where we have the problems in transmission.
A large portion of the problem is caused by the frequency, which causes induction in the wire's central core. The higher the frequency, the more induction. This forces the current to the outside.
There are a lot of reasons why the surface of a wire catches hell, and why we silver coat some conductors, and copper coat aluminum and steel conductors.
I came here to see if I could learn something......Guess not...
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