PDA

View Full Version : Podcast: Dark Matter Maps



Fraser
2005-Dec-14, 05:46 PM
SUMMARY: What's the Universe made of? Don't worry if you don't have a clue, astronomers don't either. The Universe is dominated by a mysterious dark matter that seems to form the true mass of a galaxy, not the regular matter - like stars and planets - that we can actually see. Dr. James Jee from Johns Hopkins University used the Hubble Space Telescope to create a detailed map of dark matter concentrations around two galaxies. And astronomers just got some new clues.

View full article (http://www.universetoday.com/am/publish/podcast_dark_matter_maps.html)
What do you think about this story? post your comments below.

robertgrunberg
2005-Dec-17, 01:14 AM
Dark matter is aether is tripositronium molecules, chemical symbol, Ps3; the idealest, most cosmically abundant (not H2) and lightest of all gases.

GBendt
2005-Dec-19, 12:32 AM
Hi,

dark matter is something very hypothetical. It is an idea, but yet nothing real. Neither nuclear physicists nor astrophysicists have found a single particle of dark matter yet, in spite of decades of manifold and scrutinising research. There are strong indications that dark matter is nothing that we know of, and it may even not exist at all.

It is not a gas. It does not interact with any particles. Is does not interact with any kind of radiation. It seems to exist only in the halo of galaxies, but not in my morning tea pot, or within our sun.
If you say that you call it positronium, you may call it so, but nobody has found it yet and has proveb its existence. It think it is an invention of yours, but nothing found in nature or by any scientific research, published in scientific papers and discussed and tested by professional scientists.

If we try to understand the universe, we must not replace it by our imagination. It is beyond our imagination.
You have no chance to imagine a universe with a hundred billion of galaxies, each with a hundred billion of unique and different stars. But every now and then we may catch a glimpse on it, and may learn a little bit more about it.

regards,

Günther

George
2005-Dec-19, 04:02 PM
Very Cool, Fraser. Thanks. Now I am getting interested enough to reveal my ignorance...

What does this say about MOND?

If dark matter is collisionless, how does it stay in cloud form?

Are there "dark" black holes?

GBendt
2005-Dec-20, 03:17 PM
Hi George,

nice questions you have!

MOND is a theory which explains the behaviour of galaxy movement and rotation of galaxies without requiring any dark matter. Those who like the idea of dark matter more are not very much attracted by the approach of the MOND theory.

The idea of dark matter is that there is a field of gravity strong enough to keep the dark matter at its place. Such it builds a stable cloud. On the other hand, this dark matter must stay away from real matter.
If dark matter were in stars, it would most likely make up so much of the mass of any star that it would by far exceed the mass of the hydrogen in that starīs core. This would surely have an impact on both the starīs energy production as well as the time span of that energy production of the star, the star would shine hotter as well as shorter: and that does not comply with our proven findings on stars.

I donīt think that "dark matter" does create black holes, as dark matter evidently keeps a vast distance to any real matter. Such, the "dark matter" is a very "thin" stuff, and you cantīt compress it. A matter that is not compressed cannot end in a black hole.

I have doubts in the existance of something that avoids something the existence of which it canīt detect. With time, other may share my point of view, or change it by a better one.

Regards,

Günther

George
2005-Dec-20, 05:05 PM
Hi Gunther,

nice answers you have! ;)


MOND is a theory which explains the behaviour of galaxy movement and rotation of galaxies without requiring any dark matter. Those who like the idea of dark matter more are not very much attracted by the approach of the MOND theory.
That is where I was headed. This evidence seems to be detremental to the MOND camp. IIRC, MOND works best in singular galaxy applications, and fails in super cluster velocity predicitions. This new evidence is based on individual galaxy parameters, right?


The idea of dark matter is that there is a field of gravity strong enough to keep the dark matter at its place. Such it builds a stable cloud. On the other hand, this dark matter must stay away from real matter.
If dark matter were in stars, it would most likely make up so much of the mass of any star that it would by far exceed the mass of the hydrogen in that starīs core. This would surely have an impact on both the starīs energy production as well as the time span of that energy production of the star, the star would shine hotter as well as shorter: and that does not comply with our proven findings on stars.
That is logical, thanks. Are you saying, though, the gravitational field acts to keep dark matter from wandering apart? Why couldn't gravity cause it to condense?


I donīt think that "dark matter" does create black holes, as dark matter evidently keeps a vast distance to any real matter. Such, the "dark matter" is a very "thin" stuff, and you cantīt compress it. A matter that is not compressed cannot end in a black hole.

I have doubts in the existance of something that avoids something the existence of which it canīt detect. With time, other may share my point of view, or change it by a better one. So it seems to like being "thin ground", so "dark matter" is a pun, too. Ok, great! Now you do have my interest. :)

GBendt
2005-Dec-26, 12:13 AM
Hi George,

The dark matter problem is puzzling. The existence of dark matter was postulated to explain why dynamic galaxy clusters are stable, and why stars in the outer areas of galaxies move faster than they are expected to do, if you consider the gravity that is effected by the visible and detectable mass of such a galaxy. There ought to be more mass in the outer areas of galaxies than could be traced by photographs or by radio astronomy research.

Unfortunately, all efforts to explain what this dark matter is have failed so far. Renowned professoers of astrophysicists call this the greatest possible mishap in contemporary astrophysics.

This leads to the conclusion that there may be an error in the assumptions on which the idea of the existence of dark matter is based.
If you look and look and look and canīt find what you are looking for, you may either be taking the wrong means, or you are searching at the wrong places, or you may be looking for something that does not exist at all.

We see a galaxy cluster and assume that this galaxy cluster must be stable, as otherwise the galaxies of this cluster would move out of the cluster. But we do not know whether this galaxy cluster is stable, we just assume it to be, as we transfer findings from our solar system (which is stable) to a galaxy cluster. We know how a galaxy cluster looks like, and we see how the galaxies of this cluster are moving. But we cannot know whether this cluster will still be a cluster in the future, we just assume it to be, as we have the concept that a cluster is something stable.

Further, I get the impression that all the figures that were mentioned on the masses of galaxies during the last decades turn out to be assumptions, too.

Our galaxy, for instance, was said to contain 100 billion stars and a mass of 100 billion solar masses, of which 80% was said to be accumulated in stars.
Well, a few days ago I read a paper which says that our galaxy may contain 600 billion stars and at least 500 billion solar masses. It is embedded in vast clouds of cold hydrogen gas, each of a hundred million solar masses, which are falling into our galaxy, thus providing new material for future stars. This information was not available when the concept of dark matter was created.

You can even read scientific papers which say that galaxy clusters were found to be embedded in vast clouds of hydrogen which have a mass that is several times greater than that of all the galaxies of the cluster! This may indicate that the stars of a galaxy may contain just a few percent of the available mass acting in the entire galaxy. There seems to be plenty of mass of which nobody thought of before.

Thus, the dark matter problem may be solved if you can prove that there is much more real matter out there as was expected when the theory which demands the existence of dark matter was designed.

I read that dark matter was the cause which attracted real matter to build galaxies. But if you look at stars, they do not contain any dark matter. If you look at galaxies, they either do not contain dark matter. Dark matter is always said to be somewhere far out: between the galaxies, and at their outmost edge: Dark matter seems always to be distant.
And if you look at this, it is puzzling, because there is no indication how dark matter can detect from where it must stay away, and how it keeps its distance from these locations (You wonīt find dark matter in your coffee pot, the pot only contains coffee).

Currently there are only guesses about the amount of real matter which does exist in the universe. Some say it is 6e51 kg, some assume 6e52. As we find numerous new galaxies every day, auch with hundreds of billions of suns, the figure may even rise. With time, we will see better and more reliable data, and then we can sort out which theory may offer the best description.

It is becoming late now (it is past 1 a.m. in Germany), so I shall stop at this point and go to bed.

Merry Christmas, and Regards,

Günther

George
2005-Dec-27, 02:40 AM
Well, a few days ago I read a paper which says that our galaxy may contain 600 billion stars and at least 500 billion solar masses. It is embedded in vast clouds of cold hydrogen gas, each of a hundred million solar masses, which are falling into our galaxy, thus providing new material for future stars. This information was not available when the concept of dark matter was created.
I have not heard that, it would be interesting to read about, but it may be due to recent news that Andromeda is 3 times bigger in diameter than prior values.


You can even read scientific papers which say that galaxy clusters were found to be embedded in vast clouds of hydrogen which have a mass that is several times greater than that of all the galaxies of the cluster! This may indicate that the stars of a galaxy may contain just a few percent of the available mass acting in the entire galaxy. There seems to be plenty of mass of which nobody thought of before.
But what about the OP article? Are you suggesting their halo is hydrogen, or dark matter? Would this be a Lyman Marsh, instead. :) I would think spectrum lines would reveal if it was normal matter.


With time, we will see better and more reliable data, and then we can sort out which theory may offer the best description.

If I may take a WAG at it...could stable anti-neutrons (anti-proton + anti-electron) explain it? This would help with the Big Bang baryon symmetry. Why it would be so stable vs. normal neutrons immediately comes to mind. Yet, it also might explain the near collisionless aspects being found. [Just meat for the lions around here, I suppose, as I know very little of particle physics. ;)]



It is becoming late now (it is past 1 a.m. in Germany), so I shall stop at this point and go to bed.

Hope you had a great Christmas and a big bright tannenbaum.

C0ppert0p
2006-Dec-13, 01:47 AM
Dark, Unknown, Non-detectible, Non-visible, Objects, Somewhere.
I prefer this to either WIMPS and MACHOS.
Sorry, I've been dying to say that since I read, A Short History of Nearly Everything. This is the only place anyone would understand what the joke was about

George
2006-Dec-13, 02:21 PM
I didn't read the book, but I really enjoyed his audio. Although he made a number of minor mistakes, it was a treat and easy to listen to.