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Dark Energy, Dark Matter - Enigmas for Physicists and Cosmologists
Posted: 26 November 2007 10:09 AM   [ Ignore ]   [ # 31 ]
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HERE is an amusing link to a recent Scientific American video that tries to explain dark matter in 60 seconds.  It’s called “What is Dark Matter?”

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Posted: 26 November 2007 10:25 AM   [ Ignore ]   [ # 32 ]
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That was fun! :grin:

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Posted: 26 November 2007 10:26 AM   [ Ignore ]   [ # 33 ]
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kkwan - 25 November 2007 07:43 PM

It is good to reflect that many of our current ideas of humanism were proposed more than 2000 years ago by the wise from diverse cultures.

We seemed to have wandered off into the realms of philosophy and humanism. However, dark energy and dark matter raises questions not only for scientists, but also for philosophers and all of us because there is so much more in the universe than what was thought. Our worldview has to change to accomodate these findings and it will be grander.

I still don’t place the significance of DM/DE that you do on the sciences and philosophy.  This is just one more aspect of reality to explore (albeit a huge one), one which scientists are already attacking with gusto.  I would agree that DM/DE “raises questions,” but again, that’s science’s job.  I think it would only be an issue for scientists, philosophers and all of us if we had confidently assumed that we already know everything there is to know about the structure of the universe.  Obviously this isn’t the case.  DM/DE is not some mystical, supernatural substance and energy; it is the fabric of our known universe.  Given a few more years, DM/DE will be as accepted and understood as, say, black holes and quasars, which were enigmas and mysteries in their time.

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Posted: 26 November 2007 11:05 AM   [ Ignore ]   [ # 34 ]
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Every generation has its scientific mysteries. It’s just the nature of the beast.

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Posted: 26 November 2007 10:21 PM   [ Ignore ]   [ # 35 ]
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Jayhox - 26 November 2007 10:26 AM

I still don’t place the significance of DM/DE that you do on the sciences and philosophy.  This is just one more aspect of reality to explore (albeit a huge one), one which scientists are already attacking with gusto.  I would agree that DM/DE “raises questions,” but again, that’s science’s job.  I think it would only be an issue for scientists, philosophers and all of us if we had confidently assumed that we already know everything there is to know about the structure of the universe.  Obviously this isn’t the case.  DM/DE is not some mystical, supernatural substance and energy; it is the fabric of our known universe.  Given a few more years, DM/DE will be as accepted and understood as, say, black holes and quasars, which were enigmas and mysteries in their time.

The frontier of science and philosophy is fuzzy. What science finds enigmatic and does not yet fully understand lies in the realm of philosophy. Why DM/DE is IMPORTANT is because it is 96% of the universe, is unknown, keeps it from collapsing and in the case of DE, permeates all space like the “ether”. Unlike black holes and quasars which are cosmological objects which can be directly observed and studied, DM/DE are not visible entities and can only be inferred from anomalous cosmological data. This makes DM/DE much more difficult to observe and study.

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Posted: 27 November 2007 05:28 AM   [ Ignore ]   [ # 36 ]
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kkwan - 26 November 2007 10:21 PM

The frontier of science and philosophy is fuzzy. What science finds enigmatic and does not yet fully understand lies in the realm of philosophy.

What science finds enigmatic and does not fully understand does not necessarily lie in the realm of philosophy.  It is unknown so it doesn’t lie anywhere.  Hopefully just for now, but it is unknown nonetheless.  There is more to philosophy than speculation.  Philosophy addresses something of a different category of issues, although it must be informed by the physical sciences in order to remain current.  Conversely, philosophy can provide fresh angles that can can inform physics.  But it also requires an epistemological framework.

kkwan - 26 November 2007 10:21 PM

Why DM/DE is IMPORTANT is because it is 96% of the universe, is unknown, keeps it from collapsing and in the case of DE, permeates all space like the “ether”. Unlike black holes and quasars which are cosmological objects which can be directly observed and studied, DM/DE are not visible entities and can only be inferred from anomalous cosmological data. This makes DM/DE much more difficult to observe and study.

I also think that dark matter and energy are interesting and important, but I would be careful about reading things into it that might not be there.  Fascinating stuff.

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Posted: 27 November 2007 06:07 AM   [ Ignore ]   [ # 37 ]
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kkwan - 26 November 2007 10:21 PM

Why DM/DE is IMPORTANT is because it is 96% of the universe, is unknown, keeps it from collapsing and in the case of DE, permeates all space like the “ether”. Unlike black holes and quasars which are cosmological objects which can be directly observed and studied, DM/DE are not visible entities and can only be inferred from anomalous cosmological data.

Is it IMPORTANT? Relation problems with your wife solved? No hunger in the world anymore? No fundamentalist terrorist attacks anymore?

Or put it differently: the mass of all the black holes in the universe is factors bigger then than the mass of all humans. Makes that black holes more important than humans? What is the IMPORTANCE of 96% unknown substance?

Or is it…. INTERESTING. With that, I would agree.

On quantum theory a whole lot of technologies is based, new facts are discovered daily, an awful lot of phenomena explained. It is still too early to say if quantum is in a crisis, maybe just a few adaptions could explain DM/DE. But may be our complete scientific world view must change. But it will still be science. To explain the movement of cars that can override you, space ships to Mars etc, Newton mechanics still suffices. For designing new transistors we possibly need no explanation of DM/DE…

Sorry, I am just reacting on the suspicious feeling, that you would like to throw science away because there is a theory that has some fundamental riddles. And: there is a big chance, that whenever these problems are solved, that no layman or laywoman (and surely no politician) will understand what it is all about.

GdB

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Posted: 27 November 2007 06:50 AM   [ Ignore ]   [ # 38 ]
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In the 60-second clip provided by erasmusinfinity the guy talks about stars rotating within a galaxy, right? I am just wondering, do galaxies also rotate?

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Posted: 27 November 2007 07:09 AM   [ Ignore ]   [ # 39 ]
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erasmusinfinity - 27 November 2007 05:28 AM

What science finds enigmatic and does not fully understand does not necessarily lie in the realm of philosophy.  It is unknown so it doesn’t lie anywhere.  Hopefully just for now, but it is unknown nonetheless.  There is more to philosophy than speculation.  Philosophy addresses something of a different category of issues, although it must be informed by the physical sciences in order to remain current.  Conversely, philosophy can provide fresh angles that can can inform physics.  But it also requires an epistemological framework.

What is philosophy?

http://objectivistcenter.org/cth—409-FAQ_Philosophy.aspx

In Greek, “philosophy” means “love of wisdom.” Philosophy is based on rational argument and appeal to facts. The history of the modern sciences begins with philosophical inquiries, and the scientific method of experimentation and proof remains an instance of the general approach that a philosopher tries to bring to a question: one that is logical and rigorous. However, while today the sciences focus on specialized inquiries in restricted domains, the questions addressed by philosophy remain the most general and most basic, the issues that underlie the sciences and stand at the base of a world-view.

Philosophy raises some of the deepest and widest questions there are. Addressing the issues in each branch of philosophy requires integrating everything one knows about reality (metaphysics) or humanity (epistemology, ethics, politics, and aesthetics). Proposing reasonable positions in philosophy is therefore a difficult task.

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Posted: 27 November 2007 07:33 AM   [ Ignore ]   [ # 40 ]
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GdB - 27 November 2007 06:07 AM

Is it IMPORTANT? Relation problems with your wife solved? No hunger in the world anymore? No fundamentalist terrorist attacks anymore?

Or put it differently: the mass of all the black holes in the universe is factors bigger then than the mass of all humans. Makes that black holes more important than humans? What is the IMPORTANCE of 96% unknown substance?

Or is it…. INTERESTING. With that, I would agree.

On quantum theory a whole lot of technologies is based, new facts are discovered daily, an awful lot of phenomena explained. It is still too early to say if quantum is in a crisis, maybe just a few adaptions could explain DM/DE. But may be our complete scientific world view must change. But it will still be science. To explain the movement of cars that can override you, space ships to Mars etc, Newton mechanics still suffices. For designing new transistors we possibly need no explanation of DM/DE…

Sorry, I am just reacting on the suspicious feeling, that you would like to throw science away because there is a theory that has some fundamental riddles. And: there is a big chance, that whenever these problems are solved, that no layman or laywoman (and surely no politician) will understand what it is all about.

Hmm… as erasmusinfinity wrote, it is interesting and important, but not in the everyday human worldy sense. It is important to find out why 96% of the universe is made of unknown DM/DE. Take away the 96% and the 4% collapses. Is the 96% not important?

Nobody can throw science away. What I am saying is science cannot as yet understand the nature of DM/DE. Perhaps, a paradigm shift or a new theory is necessary. Who cares whether any politician will understand it?

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Posted: 27 November 2007 07:43 AM   [ Ignore ]   [ # 41 ]
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George - 27 November 2007 06:50 AM

I am just wondering, do galaxies also rotate?

I did find a pretty good answer for you.

Galaxies, by contrast, rotate either direction depending on your point of view—there is no known up or down in the universe. (A study in the late 1990s suggested the universe was directional, but the work was soon refuted.)

Why do galaxies rotate in the first place? The answer goes back to the formation of the universe, when matter raced outward in all directions. Clumps eventually formed, and these clumps began to interact gravitationally. Once stuff moved off a straight course and began to curve toward something else, angular momentum, or spin, set in. The laws of physics say angular momentum must be conserved.

“Masses of material from which galaxies were formed had an initial amount of angular momentum,” explains Rick Perley of the National Radio Astronomy Observatory. As a developing galaxy’s gas, dust and stars contract into a smaller region of space, it all spins faster—just as a skater twirls more rapidly by pulling her arms in.

Astronomers don’t know exactly how a galaxy like the Milky Way gets its spiral arms. But the basics are understood. Gravitational disturbances called density waves, rippling slowly through a galaxy, are thought to cause it to wind up and generate the spiral appearance.

The spiral arms of a galaxy are places where gas piles up at the wave crests. The material does not move with the spirals, but rather is caught up in them.

Interesting stuff….

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Posted: 27 November 2007 07:46 AM   [ Ignore ]   [ # 42 ]
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George - 27 November 2007 06:50 AM

In the 60-second clip provided by erasmusinfinity the guy talks about stars rotating within a galaxy, right? I am just wondering, do galaxies also rotate?

Yes, they both rotate and move, George. Here is a fun website on this:

http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/galaxies_move.shtml

Yes, galaxies do move. They both rotate and move through space. Galaxies rotate around their centers with the sections of the galaxy that are farther out from the galaxy’s center rotating more slowly than the material closer to the center. Galaxies are also moving away from each other due to the expansion of the universe brought on by the Big Bang. A galaxy which is part of a group of galaxies, called a cluster, also rotates around the center of mass of the cluster.

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Posted: 27 November 2007 08:07 AM   [ Ignore ]   [ # 43 ]
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Hmm, if the section of the galaxy that is farther form its center moves slower than the section closer to its center, it’s not really the same thing as the rotating CD on the guy’s finger in the clip, is it?

And also, do clusters form even bigger clusters? Or is that it? Because if they were to form bigger clusters, I guess they would also rotate around some center. Is there an end to this? Would we eventually find the “center of the universe” around which everything rotates? (My only hope is that we are nowhere near close to such a center; that’s if it were to exist. Can you imagine? The Christians would be even more unbearable…:grin:)

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Posted: 27 November 2007 08:17 AM   [ Ignore ]   [ # 44 ]
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George - 27 November 2007 08:07 AM

Hmm, if the section of the galaxy that is farther form its center moves slower than the section closer to its center, it’s not really the same thing as the rotating CD on the guy’s finger in the clip, is it?

They rotate more like the solar system rotates, following Newton’s laws of motion to a high approximation. The farther out you are from the center, the slower you rotate. The discovery of dark matter comes from the fact that this rotation doesn’t exactly follow Newton’s laws ... at least, if you figure out all the visible mass, it’s still rotating faster than it should be. So there has to be additional “dark” (invisible) mass.

George - 27 November 2007 08:07 AM

And also, do clusters form even bigger clusters?

Yes, they form so-called “superclusters”.

George - 27 November 2007 08:07 AM

Because if they were to form bigger clusters, I guess they would also rotate around some center.

No, not necessarily and indeed not usually. The superclusters are organized in larger filamental structures.

George - 27 November 2007 08:07 AM

Is there an end to this?

From our vantage point, the edge of the visible universe.

George - 27 November 2007 08:07 AM

Would we eventually find the “center of the universe” around which everything rotates?

Every part of the universe is its center. Think of the three-dimensional universe as analogous to a two-dimensional surface of a balloon. Paste dots onto the balloon. If you blow it up, the dots all move away from each other, but there is no “central dot”. If you like, insofar as there is a “center” it is in an additional dimension (the third) at the center of the balloon. I suppose it’s possible that there is a fourth dimension of space which is the “center” of our three (spatial) dimension universe, but it would not be visualizable.

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Posted: 27 November 2007 08:28 AM   [ Ignore ]   [ # 45 ]
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I have heard the two-dimensional balloon analogy before. But I have never thought of the balloon’s center being compared to our “center” in a fourth dimension. It makes sense. Very interesting, Doug.

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