attn Scotty

Kind of bored today and came across this:

antimatter-belt-found-circling-earth

btw, one article mentioning this is "dark matter" [can't find it now] was just wrong. Or I am very much mistaken. Dark matter has surprised the s**t out of astronomers, they don't really know what it is. But from what I have read it is expressly *not* protons, neutrons, or electrons [either matter or antimatter variety] and is not detected at all except that it is known by its gravitational powers. In other words, it is as if it does not exist except for its gravity, and must be considered 'matter' because that is all we would know that would have gravity. If we ever come to understand it, instead we might declare something else exists that exerts gravity.

Very strange business.

Quote: odiousgambit

btw, one article mentioning this is "dark matter" [can't find it now] was just wrong. Or I am very much mistaken. Dark matter has surprised the s**t out of astronomers, they don't really know what it is. But from what I have read it is expressly *not* protons, neutrons, or electrons [either matter or antimatter variety] and is not detected at all except that it is known by its gravitational powers. In other words, it is as if it does not exist except for its gravity, and must be considered 'matter' because that is all we would know that would have gravity. If we ever come to understand it, instead we might declare something else exists that exerts gravity.

Very strange business.

All this is right, as best I understand it. But equally as likely an explanation as dark matter is that they're not measuring velocity correctly over such great distances, or that gravity has some sort of bizarro relativistic effect when great distances are involved. Any alternate explanation that keeps the stars from flying off and "changes" the momentum of light works as well as dark matter, and has been equally as "proved."

As for me, it sounds a little revolutionary, but I kind of lean towards a bizarro relativistic effect. Not that it's been "proved" or anything, but neither has dark matter and they've been looking for that for nearly 80 years. But bizarro-relativity would explain lensing, possibly align with inflation theory, and would imply that the universe is not as old as the current guess. And, dark matter, on the surface, seems just as wishful-thinking as Einstein's cosmological constant.

Gravity bizarro-relativity would only apply at galactic distances or greater, kind of in the same way that relativity only applies at near-light speeds. (Well, it ALWAYS applies, but its effects are so small that they're not worth accounting for.) But since we can barely measure gravitomagnetism, I think we're even that much further from measuring gravity-bizarro-relativity.

Quote: odiousgambit

btw, one article mentioning this is "dark matter" [can't find it now] was just wrong. Or I am very much mistaken.

No one knows what dark matter is, or even if it actually exists. There are many hypotheses, but no concrete evidence.

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In other words, it is as if it does not exist except for its gravity, and must be considered 'matter' because that is all we would know that would have gravity. If we ever come to understand it, instead we might declare something else exists that exerts gravity.

Oh, it's easy to explain.

Using the Doppler shift on the spectra taken of galaxies, one can easily determine at what speed the stars in that galaxy are spinning along their orbits.

Well, it turns out stars are spinning too fast. That is, at the speed they show, the galaxies should not be able to hold them in orbit given each galaxy's gravity. the only thing in the Universe that can generate gravity is mass. Given that stars are in orbit around their galaxies and not flying off into deep space, the logical conclusion is there is a source of gravity unaccounted for. Since only mass can produce gravitational force, that means there's a missing mass no one has been able to detect.

Now, mass doesn't mean matter. Energy has mass, too. But an awful lot of energy is equivalent to a small amount of matter, therefore most likely the missing mass is made of matter.

Since it cannot be detected, and certainly not seen, it's called "Dark Matter." It's a common terminology. The side of the Moon that faces away from the Earth is known as "The Dark Side of The Moon." it isn't dark, of course, as it gets as much sunlight as the other side of the Moon, but we can't see it unless we travel physically to the Moon (in person or by space probe proxy) and look at it.

As I said, there are hypotheses concerning Dark Matter. Most have to do with subatomic particles (not protons, neutrons, electrons, anti-protons, anti-neutrons or positrons[anti-electrons], nor any others of the many found in the Standard Model, including anti-matter), but there's a small school of thought that believes gravity behaves differently at galactic scales. The latter is improbable, but not necessarily impossible. The more we learn, the more we find out there's much more to learn.

Quote: odiousgambit

But from what I have read it is expressly *not* protons, neutrons, or electrons [either matter or antimatter variety] and is not detected at all except that it is known by its gravitational powers.

This (well, roughly, this) is only one of the theories of dark matter (WIMP dark matter).
Another one (MACHO) supposes that dark matter consists of regular baryonic particles, that just do no emit any light.

Regardless, there actually is something else besides matter that exerts gravity - it's the energy. Dark matter is not it thought. It is matter. That much is actually known.

Quote: Nareed

Oh, it's easy to explain.

Using the Doppler shift on the spectra taken of galaxies, one can easily determine at what speed the stars in that galaxy are spinning along their orbits.

Well, it turns out stars are spinning too fast. That is, at the speed they show, the galaxies should not be able to hold them in orbit given each galaxy's gravity. the only thing in the Universe that can generate gravity is mass. Given that stars are in orbit around their galaxies and not flying off into deep space, the logical conclusion is there is a source of gravity unaccounted for. Since only mass can produce gravitational force, that means there's a missing mass no one has been able to detect.

This phenomenon is more traditionally explained by a presence of massive black holes in the centers of galaxies.

The dark matter is different. Its existence is inferred from comparing the observed mass of the universe to the theoretical calculations.
It turns out that only about 10% of the mass that should be in the universe is observed by electromagnetic means. The remaining 90% is missing and attributed to dark matter and dark energy.

Quote: weaselman

This phenomenon is more traditionally explained by a presence of massive black holes in the centers of galaxies.

The dark matter is different. Its existence is inferred from comparing the observed mass of the universe to the theoretical calculations.
It turns out that only about 10% of the mass that should be in the universe is observed by electromagnetic means. The remaining 90% is missing and attributed to dark matter and dark energy.

Not really. Central black holes don't explain lensing that occurs away from the center. The lensing thing is what "forces" the current best guesses to say that dark matter is more (kinda) infused throughout a galaxy than just a mass at the center.

That's kind of the hard thing to ignore about the gravity-bizarro-relativity thing. It's just a thought experiment, is not accepted in the scientific community, and has ramifications that contemporary science would be slow-in-the-extreme to accept (the most far-reaching being that the universe would be younger than current guesses, not so young as to reconcile with the bible but younger). But it does (sort of) unify lensing, star velocities, and inflation - which dark matter doesn't do. And, as much "proof" for it has been "found" as for dark matter.

Weirdy McWeirdweird.

In case you're still bored, there was a just a news story about a very dark planet.

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TrES-2b, a Jupiter-sized gas giant around 750 light-years from Earth that's now taking top billing as the darkest exoplanet that astronomers have ever discovered.

Brightness readings measured by NASA's Kepler spacecraft suggest that TrES-2b reflects less than one percent of the sunlight that hits it – and that's coming from a star a mere three million miles away from the planet itself (GSC 03549-02811).

It's not clear what is responsible for making this planet so extraordinarily dark," said Princeton University professor David Spiegel, co-author of the paper that first reported the planet's existence. "However, it's not completely pitch black. It's so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove."

http://www.pcmag.com/article2/0,2817,2391050,00.asp

Quote: ItsCalledSoccer

Not really. Central black holes don't explain lensing that occurs away from the center. The lensing thing is what "forces" the current best guesses to say that dark matter is more (kinda) infused throughout a galaxy than just a mass at the center.

What did you mean by "not really"? That is more or less exactly what I said - dark matter is not mass in the center. Black holes (in the center or not) are sometimes considered a variety of dark matter, but more often than not they aren't.

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That's kind of the hard thing to ignore about the gravity-bizarro-relativity thing. It's just a thought experiment, is not accepted in the scientific community, and has ramifications that contemporary science would be slow-in-the-extreme to accept (the most far-reaching being that the universe would be younger than current guesses, not so young as to reconcile with the bible but younger). But it does (sort of) unify lensing, star velocities, and inflation - which dark matter doesn't do. And, as much "proof" for it has been "found" as for dark matter.

Weirdy McWeirdweird.

What is? What are you talking about?

Quote: weaselman

What did you mean by "not really"? That is more or less exactly what I said - dark matter is not mass in the center. Black holes (in the center or not) are sometimes considered a variety of dark matter, but more often than not they aren't.

Oh, okay. Guess I misunderstood. Although I would not say a black hole is the same as Dark Matter. Black holes are dark, and they are matter, so they are dark matter in a sense, but they aren't Dark Matter in the sense of the proposed mass that exists but nobody can find. We've found black holes; we haven't found Dark Matter.

Quote: weaselman

What is? What are you talking about?

Well, in a sense, nothing real. It's just a postulate, and it's not gaining momentum and won't unless and until the whole Dark Matter theory loses favor. It would require a lot of clarification and discovery, but at least as a thought experiment, it seems to point us in the right direction. But at this stage, it's just as imaginary as Dark Matter.

Quote: ItsCalledSoccer

Although I would not say a black hole is the same as Dark Matter. Black holes are dark, and they are matter, so they are dark matter in a sense, but they aren't Dark Matter in the sense of the proposed mass that exists but nobody can find. We've found black holes; we haven't found Dark Matter.

That is again, exactly what I said. Black holes are sometimes referred to as one of the "flavors" of dark matter. But it is quite clear, that there exist other flavors as well, and it these other, yet unkown flavors, that are usually collectively referred to as dark matter.

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Well, in a sense, nothing real. It's just a postulate, and it's not gaining momentum and won't unless and until the whole Dark Matter theory loses favor. It would require a lot of clarification and discovery, but at least as a thought experiment, it seems to point us in the right direction. But at this stage, it's just as imaginary as Dark Matter.

What postulate?
Dark matter isn't imaginary, BTW. It is very real ... just dark :)

Weasel, have you held a piece of dark matter? Dark matter is really just theoretical and used as a way to tie the rate of expansion of the universe to the mass of the universe, or to account for the difference in gravitational effects observed vs the mass observed.

There have been plenty of possible explanations as to what "dark matter" is, but there has been no observation of dark matter. The effects of "dark matter" due to the excess force of gravity has been seen.

Of course it's much more complex than that. And certainly today's theoriets cannot jive the observational evidence with what they see, so they make up the difference with "dark matter" and postulate what that is made up of.

Quote: weaselman

Dark matter isn't imaginary, BTW. It is very real ... just dark :)

What I know about it is limited, and I would have to bow quickly to superior knowledge, but I would have to say I don't think black holes are much accepted as an explanation per se. Black holes are in a sense not invisible, because the matter surrounding and orbiting them is visible and often especially visible due to the stress. They really can't be created in an environment where this wouldnt be the case. I concede it is possible for a black hole to be ejected from a system where black holes were orbiting each other and have one subsequently be traveling in space with no matter around it to reveal it [one doomsday scenario for Earth involves the possibility of such heading our way], but clearly there could not be enough of these to explain the phenomenon of dark matter.

I would say what isn't imaginary is the gravity exerted by this hypothetical matter. Astronomers don't seem willing to say gravity in space is something they don't understand. However, there we seem to be discovering things on heaven and earth, and in the universe, undreamt of in our philosophies... now we have to invent a theory about a type of matter that we can't really describe.

Quote: boymimbo

Of course it's much more complex than that. And certainly today's theoriets cannot jive the observational evidence with what they see, so they make up the difference with "dark matter" and postulate what that is made up of.

Indeed.

But this isn't the first time.

Back in the XIX century Mercury's orbit did not conform to what Newton's Law of gravity predicted. Scientists therefore postulated the existence of an undetected, small planet inside Mercury's orbit (or a swarm of smaller bodies). Such a planet would be hard to detect visually, as it would be lost in the glare of the sun. Long story short, no planet or sizable body was ever found there. Early in the XX century, Einstein's extension of Newton's laws, part of the theory of Relativity, explained Mercury's peculiarities, as well as minor ones of other planets.

At the time scientists made the assumptions that their knowledge led them to. So is the case today. Back then the answer came from an unexpected direction. Today we don't know what the answer is, but the assumption that there is undetected matter is reasonable. We'll just have to wait and see.

Quote: weaselman

That is again, exactly what I said. Black holes are sometimes referred to as one of the "flavors" of dark matter. But it is quite clear, that there exist other flavors as well, and it these other, yet unkown flavors, that are usually collectively referred to as dark matter.

No, this is incorrect. Dark Matter in the sense of the proposed stuff that keeps stars from flying off is only postulated, and has not been observed. Dark matter - matter that is dark - is not what Dark Matter means. Merging the two is a somewhat elementary mistake, like confusing the moon and the earth. Black holes are not a form of Dark Matter in the sense Zwicky meant. Black holes help keep stars from flying away but the observations say that (among other things) black holes, in and of themselves, are insufficient. The fact that they contribute to keeping stars in orbit does not make them a flavor of Dark Matter.

You are probably thinking of MACHOs - brown dwarfs, black holes, etc. If you think that the missing 25% or so of the universe is black holes ... be my guest. That would put you in disagreement with Walter Stockwell, which is not where you want to be on this topic. That's why the effort to find WIMPs is so intense. Those are, so far, unfound, but they haven't been looking for those very long. For that matter, they can't figure out the dark energy thing, either (which amounts essentially to the Lambda).

It will be interesting to see if they ever find them. It will also be interesting that, if they do, what they will have to say about their ridicule of Einstein for postulating the Lambda to keep the universe at steady state.

Here is a NASA article. I don't know who wrote it, but it explains the correct understanding and the movement away from MACHOs to explain the missing mass.

Quote: weasleman

What postulate?

Forget it. It doesn't matter.

Quote: weaselman

Dark matter isn't imaginary, BTW. It is very real ... just dark :)

Except for it's imaginary. It's never been found. This is a pretty good elementary article from Dr. White over at Cal on exactly what it is and isn't. It also flirts with lensing and inflation (called "evolution of the expansion factor" in the article).

It's pretty clear that Dark Matter is only postulated and never found. You can disagree with and Dr. Stockwell, NASA, and Dr. White if you want, no skin off my nose. It just kind of makes it hard to have a discussion on the topic.

Quote: boymimbo

Weasel, have you held a piece of dark matter?

I haven't held a piece of quark either. Or a photon or higgs boson for that matter, not to mention a superstring or a P-brane.
What's your point? Do you consider real only those things you can touch?

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Dark matter is really just theoretical and used as a way to tie the rate of expansion of the universe to the mass of the universe, or to account for the difference in gravitational effects observed vs the mass observed.

Yes, in the same sense as photon is "just theoretical" and used to explain why the black body does not emit radiation with infinite power. So what?

Quote: ItsCalledSoccer

No, this is incorrect. Dark Matter in the sense of the proposed stuff that keeps stars from flying off is only postulated, and has not been observed. Dark matter - matter that is dark - is not what Dark Matter means. Merging the two is a somewhat elementary mistake, like confusing the moon and the earth.

It looks like you are not reading my posts. Just picking a random quote, and state, that "it is incorrect" :)
I am not sure what is your goal in such a discussion, but let's just agree, that you have reached it, and stop?

Quote: ItsCalledSoccer

It's pretty clear that Dark Matter is only postulated and never found.

I am not sure in what sense you use the term "found" here. In a way, you are right, it has not been found. Neither have been "found" black holes, super strings, higgs particles, and many, many other things, that are instrumental to the modern physics and cosmology.
They have not been "found", but they are a well founded, and accepted part of the physics, they exist in the realm of the modern physical theory, which, in time, can, possibly get overturned, like it has happened before, but for now, it is the only well-defined and self-consistent view of reality available to us.

Quote: weaselman

I am not sure in what sense you use the term "found" here. In a way, you are right, it has not been found. Neither have been "found" black holes, super strings, higgs particles, and many, many other things, that are instrumental to the modern physics and cosmology.

Several black holes have been found.

That aside, any body or particle postulated by theory or model is hypothetical until it is either detected or a flaw in the theory or model is found. Photons are routinely detected, for example, and lots of particles have been, like neutrinos, quarks (in several "flavors"), protons, anti-protons, etc etc.

No dark matter has been detected so far. At least not other than by its assumed gravitational influence. It may yet turn out that our understanding of gravity remains incomplete and there's no dark matter. I wouldn't cite odds either way. But after years of looking for it, no dark matter's been detected. The same, BTW, goes for magnetic monopoles.

Quote: Nareed

Several black holes have been found

Found how? Did someone hold them in their hand? They are not "found" in the way boymimbo suggested. Their existence was deduced via indirect electromagnetic and gravitational effects that have been observed.

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That aside, any body or particle postulated by theory or model is hypothetical until it is either detected or a flaw in the theory or model is found. Photons are routinely detected, for example, and lots of particles have been, like neutrinos, quarks (in several "flavors"), protons, anti-protons, etc etc.

Oh yeah? :) Did somebody hold them in their hand? :) Or do we just look at a white spot on an exposed photo layer, and declare, that it has been left by a photon because that's what the theory is?

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No dark matter has been detected so far. At least not other than by its assumed gravitational influence.

Same hold true for black holes.

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It may yet turn out that our understanding of gravity remains incomplete and there's no dark matter.

Of course. It can even be the case that the universe just jumped into existence a few microseconds ago as a result of a random superposition of quantum effects, and everything we think we know and remember is just an illusion.
I am talking about "reality" as described by the physics, that we know, not some abstract "absolute" thing.

Quote: weaselman

It looks like you are not reading my posts. Just picking a random quote, and state, that "it is incorrect" :)

I would have to say it was necessary to take issue with your position that dark matter was explained by black holes. That seemed to indicate you didnt understand what astronomers are postulating. If there is some connection with black holes you have read about, a source would be nice, as the rest of us have not seen that it seems.

Quote: odiousgambit

I would have to say it was necessary to take issue with your position that dark matter was explained by black holes.

It looks like you are not reading my posts either :)
I have said at least three times in this thread that black holes are separate from dark matter.
It was never my position that it is explained but black holes. If it was explained by black holes, there would not be any need for a separate term :)

I apologize. I did misunderstand your first statement about black holes.

Quote: weaselman

Of course. It can even be the case that the universe just jumped into existence a few microseconds ago as a result of a random superposition of quantum effects, and everything we think we know and remember is just an illusion.

And I kind of wish Mark Twain had started a religion and written a full Genesis type chapter.

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The Creator sat upon the throne, thinking. Behind him stretched the illimitable continent of heaven, steeped in a glory of light and color; before him rose the black night of Space, like a wall. His mighty bulk towered rugged and mountain-like into the zenith, and His divine head blazed there like a distant sun. At His feet stood three colossal figures, diminished to extinction, almost, by contrast -- archangels -- their heads level with His ankle-bone.

http://www.sacred-texts.com/aor/twain/letearth.htm

Is it me or do the red lines and orange-ish flare on the right side of Earth look like the wave motion gun firing? :)