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ljbrs
SFN Regular
USA
842 Posts |
 Posted - 06/16/2001 : 16:07:21
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There are a lot of people who cannot understand that there most likely is unseen *stuff* out there which most certainly must exist. At the beginning of the last (20th) century, all that was understood to exist was visible light, the characteristics of which were just beginning to be understood themselves. Since then, a lot of dark matter/energy has been found: Cosmic rays and electromagnetic radiation (radio, infrared, visible light, ultraviolet, x-ray, gamma), all of which are identified as *light*, and matter/energy which emits no radiation (at known frequencies) but which shows up as hidden mass which has a decided gravitational effect on objects which can be seen. Astronomers have found a lot of evidence for this, but the public is still skeptical, because such hidden mass cannot be seen and, therefore, according to the ignorant (meaning not-knowing) public, it cannot and does not exist. Only seeing, for them, is believing. *Dark matter (DM) has been MEASURED by its effect on mass (which can be viewed). So, *dark matter* is similar to a skeptical subject, but one which is very much real, meaning that the skeptics of dark matter (DM), in this instance, are wrong. Scientists are definitely able to take photographs (using special detectors) of a lot of the electromagnetic spectrum. However, the truly dark matter which remains unseen is an enigma. Nobody can see it, but it is there. We see the hidden mass through its effects on the movement of other *seen* objects.
Is anybody here skeptical of *missing mass* or of *dark matter*? I promise not to use ad hominems (or ad womanems) when responding to your answers.
ljbrs
Scientists today, know better and do better than ever before!
Edited by - ljbrs on 06/16/2001 16:12:22
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The Bad Astronomer
Skeptic Friend
137 Posts |
Posted - 06/16/2001 : 21:05:11 [Permalink]
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Dark matter does indeed exist. In fact, there are probably several flavors of it. For example, we see spiral galaxies, and can measure the speed at which they rotate. In the solar system, planets close to the Sun orbit quickly, and planets farther out more slowly. This means we can measure the mass of the Sun.
This works for those spiral galaxies too. But we can see very plainly that the rotation pattern indicates that a lot of mass is outside the visible "edge" of the galaxy. Therefore much of the mass of that galaxy must be invisible to us.
A similar argument holds for clusters of galaxies; given their measured velocities the cluster should fly apart. However, we see very old clusters that have clearly not flown apart, so something is holding them together. It must be gravity from dark matter.
Everything emits some form of EM radiation. However, it may be that this stuff is just too dim to see. Pluto is relatively nearby and it wasn't discovered until 1930 because it is so dim!
So we are very confident that DM exists. We just don't know what form (or forms) it takes.
*****
The Bad Astronomer
badastro@badastronomy.com
http://www.badastronomy.com |
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bestonnet_00
Skeptic Friend
Australia
358 Posts |
Posted - 06/17/2001 : 02:18:55 [Permalink]
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The existance of Dark Matter is pretty much a certainty.
Its probably a few MACHOS, with mostly neutronios (which are very likely to have mass) and WIMPs.
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Rift
Skeptic Friend
USA
333 Posts |
Posted - 06/17/2001 : 08:12:58 [Permalink]
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I'm going to sound like John Kierein here (ACK) but I think that at least a goodly part of it are brown dwarfs and failed stars and planets with no associated solar system, all of which would be very hard to detect.
You may be getting hung up on semantics. The "missing mass" isn't really missing... it's effects can be seen we just don't know where the hell it is... Which is why Dark Matter is a more correct term, it's there, we just can't see it and don't know where it is.
If neutrinos do have mass, then that will be a huge part of it too...
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Lars_H
SFN Regular
Germany
630 Posts |
Posted - 06/17/2001 : 08:44:58 [Permalink]
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I am not an expert on this sort of stuff and probably just understood ljbrs posting wrong, but what the hell has "dark matter" to do with the fact that at the beginning of the last century people did not know the entire electromagnetic spectrum?
Scientist argue how to account for the "dark Matter" of the universe wich is really not much more than a discrepancy between the predictions of how objects should behave and how they do behave.
I don't really see any problem in the fact that people don't belive in "dark matter". That a large part of the public is unaware of the discussion is bad. That people don't belive in anything where their is no proof is a good thing in my book.
I am skeptical, too. Can you give me a reference for your claim that the public is skeptical about "dark matter" or did you just made this part up?
Addendum:
You mentioned that at beginning of the last century only visible light was known to exist of the electromagnetic spectrum that is wrong. From your list of things that have been found since then:
Radio has been discoverd by Hertz about about 1888. Infrared light has been known since the 1880. Visible light has been known since man had eyes to see. Ultraviolet has been known since about 1840(I think). X-Rays were discovered by Röntgen in 1895. And Becquerel discovered radioactivity in 1896.
You also seem to think that cosmic rays are not electromagnetic radiation. And I don't understand your remark that e/m radiation does not radiate e/m radiation itself.
Edited by - Lars_H on 06/17/2001 12:28:41 |
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/17/2001 : 21:38:43 [Permalink]
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Lars_H:
I will attempt to answer your post, paragraph by paragraph.
You state:
quote:
I am not an expert on this sort of stuff and probably just understood ljbrs posting wrong, but what the hell has "dark matter" to do with the fact that at the beginning of the last century people did not know the entire electromagnetic spectrum?
The general public takes awhile to catch up with scientific understanding. Electromagnetic radiation is akin to dark matter. Einstein's E=mc^2 shows matter as being a form of energy. Much of the universe was opaque to us until we could get the satellites outside the Earth's atmosphere to image it. Now we have fantastic images at many wavelengths, but there is a vast portion of the electromagnetic spectrum which is yet to be imaged. At the moment, it is dark energy of a sort.
You misunderstood a lot of my posting. If the electromagnetic spectrum was not able to be viewed by the majority of the people first half of the Twentiety Century, then they did not have a clue as to how the universe would appear at radio, infrared, ultraviolet, x-ray and gamma wavelengths. Of course, there were scientists who knew about these things, but this information was not known by most, if not almost all, of the public. It was not able to be imaged, so most of the public did not know through no fault of their own.
You continue:
quote:
Scientist argue how to account for the "dark Matter" of the universe wich is really not much more than a discrepancy between the predictions of how objects should behave and how they do behave.
That "discrepancy between the predictions of how objects should behave and how they do behave" is alot of it (if not all of it). Scientists can see the effect of the gravitational action of mass upon mass, whether seen, or not seen. The unseen mass is capable of being measured by the action of the seen mass. Gravitational lensing is also a very secure technique for such imaging. Einstein rings and Einstein arcs are very visible and give evidence of unseen mass. Recently, white dwarfs have been discovered in the halo of The Galaxy (our Milky Way). White dwarf stars are most certainly part of the missing dark matter and there are expected to be an enormous number of them in the halo of our galaxy. Anything which cannot be seen, whether it is made of matter particles or of other unseen particles would be dark matter. If it is not seen, then it is DARK.
You continue:
quote:
I don't really see any problem in the fact that people don't belive in "dark matter". That a large part of the public is unaware of the discussion is bad. That people don't belive in anything where their is no proof is a good thing in my book.
There is a lot of proof, but the general public does not read SCIENCE, NATURE, PHYSICS TODAY, PHYSICAL REVIEW LETTERS, THE ASTROPHYSICAL JOURNAL, etc., nor do most of them care about science. Therefore, the general public is ignorant of a lot of science. The general public is not considered to be involved in peer review for scientists. On the other hand, the general public believes in a lot of nonsense: Pseudoscience and the media (television and radio, the web, etc.) show evidence of their abysmal ignorance.
You continue:
quote:
I am skeptical, too. Can you give me a reference for your claim that the public is skeptical about "dark matter" or did you just made this part up?
You seem to be somewhat skeptical about the scientific evidence for *dark matter*. Count yourself in as one of those skeptics. I am in a situation quite often where members of the non-scientific public are gathered. When I discuss astronomy or astrophysics, they are very skeptical about so much of it. When people are ignorant of a part of a subject, they are often skeptical of it. They often consider what they do not know as being non-existent. I am around many amateur astronomers and a lot of them are skeptical about dark matter and the accelerating universe -- anything that has changed in the field of astronomy and astrophysics brings on denial at first. But, you, yourself, are skeptical, so you ought to understand. I do not have an easy access to figures, other than ones concerning the ignorance of the American public about scientific matters. Look at all of the creation science nonsense in education which seems to be going through the courts ad infinitum. I do not want to bother looking it up. There have been studies in the past. I am certain that, if I put forth the extreme effort, I could find some of those studies.
You continue:
quote:
Addendum:
You mentioned that at beginning of the last century only visible light was known to exist of the electromagnetic spectrum that is wrong. From your list of things that have been found since then:
Radio has been discoverd by Hertz about about 1888. Infrared light has been known since the 1880. Visible light has been known since man had eyes to see. Ultraviolet has been known since about 1840(I think). X-Rays were discovered by Röntgen in 1895. And Becquerel discovered radioactivity in 1896.
I was not talking about the work in the laboratory. I was talking about imaging the universe at the various wavelengths. The discussion is concerning dark matter as making up a large portion of the unseen universe. The dark matter (DM) is out there in the universe. I was discussing the knowledge open to the general public, not about the knowledge known to scientists. The scientists are not the ones I am concerned about -- the members of the general public are.
You conclude:
quote:
You also seem to think that cosmic rays are not electromagnetic radiation. And I don't understand your remark that e/m radiation does not radiate e/m radiation itself.
Cosmic rays are not electromagnetic radiation. The major part of cosmic rays consist of matter particles (mostly electrons and some protons) with some electromagnetic (light) particles mixed in. Electromagnetic radiation consists only of light particles (at the various wavelengths: radio, infrared, visible light, ultraviolet, x-ray, and gamma ray).
Do not forget neutrinos. There is thought to be a difference in mass between at least two of the neutrino *flavors* (probably muon neutrinos and tau neutrinos). There are so very many neutrinos that if that is confirmed, a lot of the missing mass would lie in neutrinos |
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bestonnet_00
Skeptic Friend
Australia
358 Posts |
Posted - 06/18/2001 : 02:35:48 [Permalink]
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Neutronios probably do have mass, our measurements do indicate that they travel slower then the speed of light, which can only happen if they have mass (E = gamma*m*c^2), also there is the type change, from electron neutronio to muon neutronio, such switching around can only occur when particles have mass.
Since our neutronio detectors can only detect electron neutronios it is quite possible that the lower neutronio flux from the sun is due to many of them becoming muon or tau along the way.
Only one possible explanation, but a good one.
Although something else is needed, as neutronios are just too fast to be all there is, and MACHOS wont do for that.
WIMPs would do nicely. Now to find them.
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/18/2001 : 22:09:17 [Permalink]
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quote:
Neutronios probably do have mass, our measurements do indicate that they travel slower then the speed of light, which can only happen if they have mass (E = gamma*m*c^2), also there is the type change, from electron neutronio to muon neutronio, such switching around can only occur when particles have mass.
Since our neutronio detectors can only detect electron neutronios it is quite possible that the lower neutronio flux from the sun is due to many of them becoming muon or tau along the way.
Only one possible explanation, but a good one.
Although something else is needed, as neutronios are just too fast to be all there is, and MACHOS wont do for that.
WIMPs would do nicely. Now to find them.
Good. Somebody else here keeps up with the neutrino *stuff*. Of course, as you indicated, neutrinos could only account for a part of the dark matter. However, old dim white dwarf stars might be responsible for a lot of the missing mass. Of course, the mass is not missing. The massive objects simply are too dim to find easily. There are many candidates for the dark matter.
Personally, I think that the best way to foster skepticism is through science. You have to get it across early, or the children are gone for life with weird beliefs.
ljbrs
If you knew better early enough, you'd do better in the long run...
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bestonnet_00
Skeptic Friend
Australia
358 Posts |
Posted - 06/19/2001 : 04:49:45 [Permalink]
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WIMPs whilst they haven't been found are also quite likely to have some effect.
There have been computer simluated universes done to test out the Dark Matter theory, from what I have heard a universe with Neutronios was rather like ours, but there were a few things wrong with it, a universe with only WIMPs was also a lot like ours but still not as close as it could be.
I have heard that a simulation was being run on what it would be like with both but I haven't been able to find the results.
MACHOS do account for some dark matter as well.
WIMPs are highly likely to exis and there is or was a group working in a British salt mine trying to find it (they use the salt mine because it is so far below ground, cosmic rays can stuff up instruments pretty well). I don't know if they are still trying or how close they think they are but they do or did have the best chance of finding WIMPs.
In terms of science education, it really isn't enough.
Sure they teach the facts, and maybe that mixing those three chemicals will blow the school up, but they don't teach the method.
Which is actually the most important part of science education.
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Lars_H
SFN Regular
Germany
630 Posts |
Posted - 06/19/2001 : 06:02:32 [Permalink]
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thanks for the reply ljbrs but I am afraid I still don't get your point.
quote:
I am around many amateur astronomers and a lot of them are skeptical about dark matter and the accelerating universe
Do you expect everybody to know about the discussion about "Dark Matter"? It is a very specialized Problem after all.
Do you expect People to understand that there is a problem after you explained it to them? Or dou you expect them to buy into your favorite explanation of it?
I hope you meant *expanding* Universe rather than *accelerating*.
quote:
Einstein rings and Einstein arcs are very visible and give evidence of unseen mass.
I thought that these effects were primary used as indicators of the unseen mass of Black Holes. Did I get this wrong?
- Lars (who wishes more people were skeptical about things that can't be seen)
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bestonnet_00
Skeptic Friend
Australia
358 Posts |
Posted - 06/19/2001 : 07:49:42 [Permalink]
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Not everything that can't be seen really can't be seen.
Dark matter we can measure its effects and determine that something exists.
We can also look at what we know and find things that might cause it.
So far MACHOS, neutronios, and the hypothetical (and likely existant) WIMPs.
Gravitational lensing has detected black holes which could be some of the dark matter (if there are 300 black holes every cubic light year averged over the whole universe it isn't that suprising).
They have also be used to detect some MACHOS.
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/19/2001 : 20:31:24 [Permalink]
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bestonnet_00:
Axions are another possibility. They are more difficult to image, however, and are presenting some problems to the astrophysicists involved. Of course, I have mentioned the white dwarf stars which have recently been imaged in the halo for our Milky Way. They ought to make up a considerable percentage of the dark matter sought in our galaxy. They would, of course, be too faint to be imaged in other galaxies.
Lars_H:
quote:
Do you expect everybody to know about the discussion about "Dark Matter"? It is a very specialized Problem after all.
Do you expect People to understand that there is a problem after you explained it to them? Or dou you expect them to buy into your favorite explanation of it?
A lot of the people in MY astronomy club have advanced degrees in chemistry, physics, astronomy (including Ph.D. degrees). I would expect that some of them read magazines/journals such as *Science*, *Nature*, and *Physics Today* -- at least occasionally. I would expect them to be interested in astrophysics and cosmology (a branch of astrophysics).
Of course, the educated members of my astronomy group are not the ones who are skeptical about the existence of Dark Matter (which includes the proposed dark energy, Lambda, theorized as accelerating the huge galactic structures in the universe away from each other).
It always amazes me that those who have not examined the evidence carefully (either because of laziness or ignorance) should feel that they have any opinion at all about something they know absolutely nothing or next-to-nothing about. It is this assumption of knowledge in the ignorant (not knowing) public which is risible, ludicrous. I do not pay much attention to the naysayers. I am not really a proselytizer, and it is not any problem for me, EXCEPT WHEN THE NAYSAYERS WANT TO RESTRICT THE SCIENCE CURRICULA IN THE PUBLIC SCHOOL SYSTEMS and, in the process, dumb down the future public and future voters.
The Big Bang is an important foundation for any theory which might include an accelerating universe. A lot of these ignorant (meaning *not knowing*) people are the ones (Creationists, Intelligent Design folks) who want to restrict the science education in the public school systems of this country. By doing so, these dolts will effectively restrict the dissemination of real scientific information.
I guess that the old saying, *Ignorance is bliss*, still holds. Why would anybody have an opinion on a topic in which they know nothing or next-to-nothing? Beats me.
ljbrs
*Nobody ever lost money underestimating the intelligence [taste] of the American Public.* [H.L. Mencken - both versions]
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/29/2001 : 21:07:20 [Permalink]
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quote:
thanks for the reply ljbrs but I am afraid I still don't get your point.
quote:
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I am around many amateur astronomers and a lot of them are skeptical about dark matter and the accelerating universe
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Do you expect everybody to know about the discussion about "Dark Matter"? It is a very specialized Problem after all.
Do you expect People to understand that there is a problem after you explained it to them? Or dou you expect them to buy into your favorite explanation of it?
I hope you meant *expanding* Universe rather than *accelerating*.
quote:
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Einstein rings and Einstein arcs are very visible and give evidence of unseen mass.
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I thought that these effects were primary used as indicators of the unseen mass of Black Holes. Did I get this wrong?
- Lars (who wishes more people were skeptical about things that can't be seen)
I meant ACCELERATING UNIVERSE. This is recent (the past decade or so, with a paper in Nature *Letters* section which is actually where the research is shown). It has been accepted by this time by the astrophysical community. They are still testing it. Saul Perlmutter, et al. started out attempting to find out the rate at which the universe was DECELERATING. To their amazement, their computations (using Type Ia Supernovae, the best *standard candle* for the distant universe) showed that, to the contrary, the universe is not only expanding, but is accelerating in its expansion. They are still testing it in every way possible to make certain that there is not a flaw in the data. None. None. None. THE ACCELERATING UNIVERSE was selected as the *Discovery of the Year* by the journal/magazine SCIENCE for December 18, 1998. It is really one of the most exciting things in Cosmology today. If you read any science magazines regularly (Science News, Publication for the Astronomical Society of the Pacific (PASP), Science, Nature, Scientific American, Physics Today, Astronomy, Sky & Telescope, etc., the subject has been discussed over and over again. It has answered all challenges. Do not miss it. Of course, by now, it is old history, but it is still very important and the only game in town. If you are to know something about astronomy, make certain that you check this out.
ljbrs
Saul Perlmutter, et al., knew better, so they did better...
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