Dark Matter == Anti-gravity == Anti-matter gravity?

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Absalom
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Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Absalom »

Any thoughts on this?

I don't normally concern myself with higher-end physics (I don't expect to devise any valid theories since I'm not in the field, so it's mostly not worth the time), so does anyone know if this actually jives with the predictions of general relativity? I can certainly understand that ( antimatter==matter with a negative charge ) == the implication that some other trait should have 'flipped' as well (what would this be, meta-symmetry?), but wouldn't that have already been accepted or dismissed by now? Or have we just never gotten enough anti-matter to do the tests?

The apparent lack of anti-matter galaxies does, of course, make me question this in general, though I am working on the assumption that we would have a way of distinguishing them.

At any rate, if true, then:
1) would this imply that anti-matter is the 'negative matter' theoretically required to prop some types of worm-holes open so that they can be used?
2) would this theory genuinely be a likely dark-energy killer, or just reduce the theoretical magnitude of dark-energy?
3) would this imply that a body of anti-matter large enough to generate a meaningful gravity well (let's say something about the mass & size of Ceres) would likely be "self-protecting" from most matter impacts over millennial periods?

Thoughts?

Solemn
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Solemn »

As with many things, Wikipedia is my only source of knowledge on this subject.

Apparently CERN has an experiment set up to see how antimatter and gravity interact, but the first couple of pages of a Google search don't show any actual conclusions for "CERN AEGIS," just experiment outlines and such.

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Arioch
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Arioch »

I remember not too long ago when there was a theory floating around that attempted to explain the "clumpiness" of the universe... the conventional wisdom at the time was that the Big Bang must have been perfectly uniform, and so to explain the diversity in density of the modern universe it was felt that there must be some kind of exotic cosmic "superstrings" (if I remember the terminology correctly... no relation to current "string theory") that pervaded the universe, and through gravitational attraction caused galaxies to clump in certain areas, and cause vast voids in others. There was a time when this theory was fairly mainstream -- to the point where it was referred to in several Star Trek episodes (the temporal rift in the famous Yesterday's Enterprise episode is attributed to a "Kerr loop of superstring material").

Of course, today we know from observation that the Big Bang was not at all uniform... something I think any fifth grader could have predicted. As I did.

I have similar feelings about the current theories regarding "dark matter" and "dark energy." Neither are real theories that stem from any serious models of how matter works. Both are catch-phrases for the fact that recent observations don't currently match our existing theories.

The case for the existence of "dark matter" is pretty strong, but the case for what seems to be the pervasive theory that it's some sort of exotic matter doesn't seem to me to be any stronger than the quack "superstring" theory. Especially in a universe that has experienced tens of thousands of generations of supermassive stars that tend to leave very massive remnants that you can't see. What? There's a substantial percentage of matter in the universe that you can't see? Shouldn't that be obvious? Like the existence of supermassive black holes in the centers of every galaxy wasn't obvious 30 years ago when the nutjobs were coming up with quack theories of what quasars were supposed to be... but I digress...

The first strains of "dark energy" theory are even sillier... observational evidence seems to suggest that the expansion of the universe might be accelerating. It seems to me that physicists are much more interested in inventing preposterous new theories to explain this result than in maybe considering that this result might instead mean that there's something in the current theories that we don't understand that well, or (gasp) might have wrong. The principle of Occam's Razor seems to be lost on the last generation or so of theoretical physicists.

Solemn
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Solemn »

Arioch wrote: It seems to me that physicists are much more interested in inventing preposterous new theories to explain this result than in maybe considering that this result might instead mean that there's something in the current theories that we don't understand that well, or (gasp) might have wrong. The principle of Occam's Razor seems to be lost on the last generation or so of theoretical physicists.
There are alternatives to Dark Matter, it's just that they have their own absurdities.

I'd read an article in Discover Magazine years ago that claimed Dark Matter was made more or less unnecessary by Moffat's Variable Speed of Light theory, but I can't seem to find a copy of the article. Moffat's Wikipedia page and other articles referring to his attempts to propose alternatives to Dark Matter all seem to treat this work as separate from Variable Speed of Light. Interestingly, one of the men who supports Variable Speed of Light cosmology, João Magueijo, was one of the physicists who helped debunk that Cosmic String hypothesis.

I've read articles on Variable Speed of Light before and understood nothing of the math involved, but people much brighter than myself have told me that it leaves Relativity mostly intact.

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Mjolnir
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Mjolnir »

Absalom wrote:Any thoughts on this?

I don't normally concern myself with higher-end physics (I don't expect to devise any valid theories since I'm not in the field, so it's mostly not worth the time), so does anyone know if this actually jives with the predictions of general relativity? I can certainly understand that ( antimatter==matter with a negative charge ) == the implication that some other trait should have 'flipped' as well (what would this be, meta-symmetry?), but wouldn't that have already been accepted or dismissed by now? Or have we just never gotten enough anti-matter to do the tests?
Antimatter particles mirror their matter counterparts in charge and parity, or time. Parity is basically handedness or chirality....an charge-reversing mirror would make an proton look like an antiproton, or like a time reversed proton. (One model for electrons has exactly one electron in the universe, pair production and annihilation events actually being it reversing direction through time.)

As for the suggestion that antimatter and matter repel...GR does not support repulsive gravity. Space is curved by mass-energy, and due to simple geometry, objects in free motion curve toward an area of greater curvature, regardless of the "sign" of that curvature...what matters is the path lengths being longer through that curved area of space.

In any case, antimatter has positive mass-energy, or matter-antimatter annihilation would simply make particles disappear due to their net energy being zero. Negative-energy matter has been speculated about (as something needed for wormholes or diametric drives to work, for example), but it'd be something completely different from antimatter. I've never seen any explanation for why antimatter might have negative gravity or why matter and antimatter would gravitationally repel.

As for dark matter, antimatter isn't dark, it interacts quite happily through electromagnetic forces. Dark matter is also attractive (rather at odds with the idea that antimatter and matter repel), and has an attractive effect several times greater than the visible matter. This would just switch the matter-antimatter imbalance around, while raising the questions of why we can't see the huge quantities of antimatter around us and in those cosmic voids, and why we haven't been annihilated by it yet.

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Mjolnir
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Mjolnir »

Arioch wrote:The case for the existence of "dark matter" is pretty strong, but the case for what seems to be the pervasive theory that it's some sort of exotic matter doesn't seem to me to be any stronger than the quack "superstring" theory. Especially in a universe that has experienced tens of thousands of generations of supermassive stars that tend to leave very massive remnants that you can't see.
But we can see white dwarf remnants and living supergiants as well as supernova events, and there's what we don't see in microlensing events, which gives us a good idea how many neutron stars and stellar black holes are out there. They can't account for more than a fraction of visible matter, which is largely gas and dwarf stars. Primordial black holes are another candidate, but haven't been detected and we don't have an explanation for how such a thing could have formed.

The evidence is actually pretty heavily in favor of some kind of weakly interacting particle. Given the existence of neutrinos, I'm not sure why the idea gets so much resistance. And it's not just a bunch of physicists are waving their hands about and aimlessly theorizing, there's projects under way to detect dark matter particles which have produced some positive results. (http://arxiv.org/abs/1109.0702)

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Mjolnir
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Mjolnir »

Another big issue with antimatter and matter repelling each other...photons are their own antiparticle. In gravity lensing observations, they quite clearly are not being repelled from matter half the time. Star images get deflected, they don't split into separate light and antilight images or smear out in radial lines as individual photons randomly switch between acting as photons and antiphotons.

Absalom
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Absalom »

Firstly:
Mjolnir wrote:As for dark matter, antimatter isn't dark, it interacts quite happily through electromagnetic forces. Dark matter is also attractive (rather at odds with the idea that antimatter and matter repel), and has an attractive effect several times greater than the visible matter.
For a moment I couldn't figure out why you even brought this up, then I looked at the topic title. Oops, I meant to write dark energy. Sorry about the typo.


Mjolnir wrote:Antimatter particles mirror their matter counterparts in charge and parity, or time. Parity is basically handedness or chirality....an charge-reversing mirror would make an proton look like an antiproton, or like a time reversed proton.
I'd heard of that 'theory' (isn't it actually a simple and straightforward interpretation of the relevant Venn diagram(s), actually?), and was under the impression that it was generally accepted. Though I do question your "mirror their matter counterparts ... parity" wording, since that would imply that the parity itself could be mirrored (consider: one particle looks like it's counterpart through the mirror, the other looks like itself though the mirror: their parity/chirality is mirrored, leading to bizarre results which I doubt you intended to imply).

What would the set of particles including protons, anti-protons, and any theoretical others (e.g. the various suggested 'negative matter' protons) be? The best I can think of is 'meta-protons', but I don't recall hearing of a 'meta-symmetry' postulate/theory, so I assume that's not the right name.
Mjolnir wrote:(One model for electrons has exactly one electron in the universe, pair production and annihilation events actually being it reversing direction through time.)
That road could easily take you down the path of only having one of EACH particle, and from there it's seemingly inevitable that you work your way down to the idea of there only being one (or perhaps two, if you feel like being generous to yourself) Planck units of energy (perhaps on a 4-sphere, with the extra axis obviously being time). This, in turn, leads you to things like particular FTL travel theories that would probably be utterly un-navigatable even if possible, which leads us to what I suspect such particle models probably are: useless.
Mjolnir wrote:As for the suggestion that antimatter and matter repel...GR does not support repulsive gravity. Space is curved by mass-energy, and due to simple geometry, objects in free motion curve toward an area of greater curvature, regardless of the "sign" of that curvature...what matters is the path lengths being longer through that curved area of space.
This particular theorist seems to disagree, but I'm hardly qualified to judge. Still, you're basically saying that his claim would require anti-matter to produce... 'inverse curvature' (or would 'reciprocal' be better in this case?), essentially non-Euclidean curvature effects, correct? And if simply reversing the ( energy * mass ) sign of a particle was enough to produce such an effect, we would presumably see the same effect with electrons, correct?
Mjolnir wrote:In any case, antimatter has positive mass-energy, or matter-antimatter annihilation would simply make particles disappear due to their net energy being zero. Negative-energy matter has been speculated about (as something needed for wormholes or diametric drives to work, for example), but it'd be something completely different from antimatter.
I was extrapolating on the thought 'perhaps they're supposed to collapse due to gravity affecting their structures'. Is it supposed to be related to boson-number or the like instead?
Mjolnir wrote:I've never seen any explanation for why antimatter might have negative gravity or why matter and antimatter would gravitationally repel.
The first, I believe, comes from the assumption that if you:
1) have a particle whose attributes can be tied to three axes, and
2) the product of the three axes cannot vary (or else it becomes a different particle, I assume), and
3) you can change the sign of one of these axes ('electrical charge', for example), then:

4) that means that for such a sign-change to work, you must also change the sign of another axis.

Science currently seems to say that second axis is 'time', this scientist seems to be suggesting 'gravity' instead. Which does, itself, at least imply to me the requirement that gravitons (theoretical though they be) are NOT their own anti-particle in order for this to work.


The gravitational repellance of matter and anti-matter would be a straight-forward assumption, if you already assume both (4), and that the 'second axis' is gravity.
Mjolnir wrote:This would just switch the matter-antimatter imbalance around, while raising the questions of why we can't see the huge quantities of antimatter around us and in those cosmic voids,
Indeed, I even commented on this already. Though I feel that the question 'how do we know there aren't galaxies made of anti-matter that we can already see, and have misidentified' is relevant regardless of anti-matter's 'gravitational sign'.
Mjolnir wrote:Another big issue with antimatter and matter repelling each other...photons are their own antiparticle. In gravity lensing observations, they quite clearly are not being repelled from matter half the time. Star images get deflected, they don't split into separate light and antilight images or smear out in radial lines as individual photons randomly switch between acting as photons and antiphotons.
If you're willing to accept the possibly non-Euclidean implications of 'anti-matter emits anti-gravity' in the first place, then I don't think MORE weird behavior is going to slow you down.

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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Nemo »

I tend to be a bit skeptical of dark matter theory. Anything which simply must be because it validates our own (known to be correct) understandings of life, the universe, and everything flags my phlogiston filter. We plug observations into our theory, the two dont match, theres something wrong/missing with the observation. I know Im terribly over simplifying things M, but the whole thing just grates.

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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Mjolnir »

Absalom wrote:
Mjolnir wrote:Antimatter particles mirror their matter counterparts in charge and parity, or time. Parity is basically handedness or chirality....an charge-reversing mirror would make an proton look like an antiproton, or like a time reversed proton.
I'd heard of that 'theory' (isn't it actually a simple and straightforward interpretation of the relevant Venn diagram(s), actually?), and was under the impression that it was generally accepted. Though I do question your "mirror their matter counterparts ... parity" wording, since that would imply that the parity itself could be mirrored (consider: one particle looks like it's counterpart through the mirror, the other looks like itself though the mirror: their parity/chirality is mirrored, leading to bizarre results which I doubt you intended to imply).
A correction to my earlier statements: antimatter particles mirror their matter counterparts in charge or parity, mirroring both usually gives the original system (some weak interactions break CP symmetry). Apart from situations that cause CP violations, reversing charge, parity, or time will produce the same thing, the antiparticle of the original.

Absalom wrote:What would the set of particles including protons, anti-protons, and any theoretical others (e.g. the various suggested 'negative matter' protons) be? The best I can think of is 'meta-protons', but I don't recall hearing of a 'meta-symmetry' postulate/theory, so I assume that's not the right name.
I'm not sure what you're asking. There's a hypothetical class of particles referred to as mirror matter, if that's what you're asking about...there's no direct evidence of its existence (unless part of dark matter turns out to be mirror matter), but it would allow parity to be maintained as an overall symmetry, parity violations in normal matter being balanced by corresponding violations in mirror matter.

Absalom wrote:
Mjolnir wrote:(One model for electrons has exactly one electron in the universe, pair production and annihilation events actually being it reversing direction through time.)
That road could easily take you down the path of only having one of EACH particle, and from there it's seemingly inevitable that you work your way down to the idea of there only being one (or perhaps two, if you feel like being generous to yourself) Planck units of energy (perhaps on a 4-sphere, with the extra axis obviously being time). This, in turn, leads you to things like particular FTL travel theories that would probably be utterly un-navigatable even if possible, which leads us to what I suspect such particle models probably are: useless.
The interpretation is not generally applicable to all particles (protons, for example, are compound particles that can be formed from other particles via processes other than pair production and converted to other particles via processes other than annihilation, and they don't even annihilate cleanly with antiprotons, and some other particles aren't indistinguishable in the way electrons are), and doesn't involve or imply FTL.

It's simply an observation that electrons are always created paired with a positron, and they annihilate with positrons to produce nothing but a burst of EM radiation. The mathematics describing electrons and positrons is identical, just reversed in time. Pair production can be seen as a positron going backwards in time becoming an electron going forwards in time, and annihilation as an electron reversing in time to become a positron. If all electrons and positrons came from such events, you only need one particle to describe all the electrons and positrons in the universe.

Absalom wrote:
Mjolnir wrote:As for the suggestion that antimatter and matter repel...GR does not support repulsive gravity. Space is curved by mass-energy, and due to simple geometry, objects in free motion curve toward an area of greater curvature, regardless of the "sign" of that curvature...what matters is the path lengths being longer through that curved area of space.
This particular theorist seems to disagree, but I'm hardly qualified to judge. Still, you're basically saying that his claim would require anti-matter to produce... 'inverse curvature' (or would 'reciprocal' be better in this case?), essentially non-Euclidean curvature effects, correct? And if simply reversing the ( energy * mass ) sign of a particle was enough to produce such an effect, we would presumably see the same effect with electrons, correct?
As gravity already involves non-Euclidian spacetime, I'm not sure what you're getting at. I'm not sure it's at all possible to produce an effect like antigravity with the geometric approach used by GR. I also don't know what you're suggesting with the electrons.

Absalom wrote:
Mjolnir wrote:In any case, antimatter has positive mass-energy, or matter-antimatter annihilation would simply make particles disappear due to their net energy being zero. Negative-energy matter has been speculated about (as something needed for wormholes or diametric drives to work, for example), but it'd be something completely different from antimatter.
I was extrapolating on the thought 'perhaps they're supposed to collapse due to gravity affecting their structures'. Is it supposed to be related to boson-number or the like instead?
I have no idea what you're asking, it doesn't seem related to the quote. Perhaps what is supposed to collapse? How would gravitational collapse be related to boson number?

Absalom wrote:The first, I believe, comes from the assumption that if you:
1) have a particle whose attributes can be tied to three axes, and
2) the product of the three axes cannot vary (or else it becomes a different particle, I assume), and
3) you can change the sign of one of these axes ('electrical charge', for example), then:

4) that means that for such a sign-change to work, you must also change the sign of another axis.

Science currently seems to say that second axis is 'time', this scientist seems to be suggesting 'gravity' instead. Which does, itself, at least imply to me the requirement that gravitons (theoretical though they be) are NOT their own anti-particle in order for this to work.
In the standard model, the second "axis" is parity, the third is time. There's no evidence of gravity being such a symmetry.

I don't think you need to bring up gravitons to see the problems with this theory. Gravity is a function of mass-energy. If antimatter has negative gravity, then the overall gravity of a particle-antiparticle pair is zero, meaning that the gravitational field of a system suddenly drops after producing a particle-antiparticle pair, or increases when a particle-antiparticle pair annihilate. If you annihilated a matter and antimatter star in a gamma-ray mirrored box, a nearby object would suddenly find itself in a deep gravity well, without the kinetic energy it should have gained by falling into that well. It's logically inconsistent and breaks conservation laws. And then there's the gravity lensing observations I mentioned. Antimatter having antigravity might seem like a good idea, but on closer inspection it just doesn't work.

Absalom wrote:Indeed, I even commented on this already. Though I feel that the question 'how do we know there aren't galaxies made of anti-matter that we can already see, and have misidentified' is relevant regardless of anti-matter's 'gravitational sign'.
We know they aren't antimatter because the lack of massive gamma ray emissions from annihilation. Galaxies collide quite often, and even if by pure chance no matter and antimatter galaxies collided in the visible portion of the universe, galaxies form from intergalactic hydrogen. Intergalactic space has an extremely low density of matter, but any mixing of hydrogen and antihydrogen on the scale of the huge expanses separating galaxies would still certainly be obvious.

Absalom wrote:If you're willing to accept the possibly non-Euclidean implications of 'anti-matter emits anti-gravity' in the first place, then I don't think MORE weird behavior is going to slow you down.
...what?
This "weird behavior" logically follows from the assumption that such a reversal in gravitational effect exists. That it is completely at odds with observation shouldn't just slow you down, it should bring you to a complete stop as you re-evaluate your assumptions.

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Post by Trantor »

Arioch wrote:...

The first strains of "dark energy" theory are even sillier... observational evidence seems to suggest that the expansion of the universe might be accelerating. It seems to me that physicists are much more interested in inventing preposterous new theories to explain this result than in maybe considering that this result might instead mean that there's something in the current theories that we don't understand that well, or (gasp) might have wrong. The principle of Occam's Razor seems to be lost on the last generation or so of theoretical physicists.
Huzzah! Last time I mentioned such heresy Mjolnir came after me... :mrgreen:
sapere aude.

Absalom
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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Absalom »

It appears that I skipped explanatory steps repeatedly in my last post.
Mjolnir wrote:
Absalom wrote:What would the set of particles including protons, anti-protons, and any theoretical others (e.g. the various suggested 'negative matter' protons) be? The best I can think of is 'meta-protons', but I don't recall hearing of a 'meta-symmetry' postulate/theory, so I assume that's not the right name.
I'm not sure what you're asking. There's a hypothetical class of particles referred to as mirror matter, if that's what you're asking about...there's no direct evidence of its existence (unless part of dark matter turns out to be mirror matter), but it would allow parity to be maintained as an overall symmetry, parity violations in normal matter being balanced by corresponding violations in mirror matter.
What is the name of the SET of particles which includes protons, anti-protons, and any negative-matter analogues that they might have?

Mjolnir wrote:
Absalom wrote:
Mjolnir wrote:(One model for electrons has exactly one electron in the universe, pair production and annihilation events actually being it reversing direction through time.)
That road could easily take you down the path of only having one of EACH particle, and from there it's seemingly inevitable that you work your way down to the idea of there only being one (or perhaps two, if you feel like being generous to yourself) Planck units of energy (perhaps on a 4-sphere, with the extra axis obviously being time). This, in turn, leads you to things like particular FTL travel theories that would probably be utterly un-navigatable even if possible, which leads us to what I suspect such particle models probably are: useless.
The interpretation is not generally applicable to all particles (protons, for example, are compound particles that can be formed from other particles via processes other than pair production and converted to other particles via processes other than annihilation, and they don't even annihilate cleanly with antiprotons, and some other particles aren't indistinguishable in the way electrons are),
I'm quite aware of quarks, etc.
Mjolnir wrote:and doesn't involve or imply FTL.
I was:
1) thinking of a half-remembered sci-fi story with an 'FTL' drive that involved the concept that spatial location (and, by implication, time) is nothing but a quantum effect which can be directly altered with the correct technology,
2) labeling it as useless by virtue of being impossible to navigate with (too many possible destinations), and
3) using that dismissal as a lead-in to my opinion of the electron-positron theory that you mentioned.
Mjolnir wrote:It's simply an observation that electrons are always created paired with a positron, and they annihilate with positrons to produce nothing but a burst of EM radiation. The mathematics describing electrons and positrons is identical, just reversed in time. Pair production can be seen as a positron going backwards in time becoming an electron going forwards in time, and annihilation as an electron reversing in time to become a positron. If all electrons and positrons came from such events, you only need one particle to describe all the electrons and positrons in the universe.
Which I extrapolated all the way down to having only one or two plank units of energy TOTAL, which just happen to be used for everything (including your single electron/positron). The theory is a nifty idea, but I can't comprehend any actual use for it.

Seriously, how are you even supposed to TEST this?

Mjolnir wrote:
Absalom wrote:
Mjolnir wrote:As for the suggestion that antimatter and matter repel...GR does not support repulsive gravity. Space is curved by mass-energy, and due to simple geometry, objects in free motion curve toward an area of greater curvature, regardless of the "sign" of that curvature...what matters is the path lengths being longer through that curved area of space.
This particular theorist seems to disagree, but I'm hardly qualified to judge. Still, you're basically saying that his claim would require anti-matter to produce... 'inverse curvature' (or would 'reciprocal' be better in this case?), essentially non-Euclidean curvature effects, correct? And if simply reversing the ( energy * mass ) sign of a particle was enough to produce such an effect, we would presumably see the same effect with electrons, correct?
As gravity already involves non-Euclidian spacetime, I'm not sure what you're getting at.
I was implying that you were implying that anti-gravity (or at the very least this version) would make spacetime even less Euclidean than it's currently considered.
Mjolnir wrote:I'm not sure it's at all possible to produce an effect like antigravity with the geometric approach used by GR.
Fair enough, as I'm having trouble figuring out how to picture 'inverse curvature'. And no, I don't think that turning a picture of 'conventional gravitational curvature' upside down would be an accurate representation.
Mjolnir wrote:I also don't know what you're suggesting with the electrons.
I was suggesting that if anti-matter emits anti-gravity, then electrons should too, because when their (electrons and anti-protons, specifically) energies & masses are compared, they have the same sign (negative). I am, of course, assuming that the magnitude of the resulting value would be inconsequential to whether the particles emitted gravity or anti-gravity.

Mjolnir wrote:
Absalom wrote:
Mjolnir wrote:In any case, antimatter has positive mass-energy, or matter-antimatter annihilation would simply make particles disappear due to their net energy being zero. Negative-energy matter has been speculated about (as something needed for wormholes or diametric drives to work, for example), but it'd be something completely different from antimatter.
I was extrapolating on the thought 'perhaps they're supposed to collapse due to gravity affecting their structures'. Is it supposed to be related to boson-number or the like instead?
I have no idea what you're asking, it doesn't seem related to the quote. Perhaps what is supposed to collapse? How would gravitational collapse be related to boson number?
I was talking about wormholes, I thought it would be obvious from the mention of negative-matter. Is there something else that negative matter can supposedly prevent from collapsing?

Mjolnir wrote:
Absalom wrote:The first, I believe, comes from the assumption that if you:
1) have a particle whose attributes can be tied to three axes, and
2) the product of the three axes cannot vary (or else it becomes a different particle, I assume), and
3) you can change the sign of one of these axes ('electrical charge', for example), then:

4) that means that for such a sign-change to work, you must also change the sign of another axis.

Science currently seems to say that second axis is 'time', this scientist seems to be suggesting 'gravity' instead. Which does, itself, at least imply to me the requirement that gravitons (theoretical though they be) are NOT their own anti-particle in order for this to work.
In the standard model, the second "axis" is parity, the third is time. There's no evidence of gravity being such a symmetry.

I don't think you need to bring up gravitons to see the problems with this theory. Gravity is a function of mass-energy. If antimatter has negative gravity, then the overall gravity of a particle-antiparticle pair is zero, meaning that the gravitational field of a system suddenly drops after producing a particle-antiparticle pair, or increases when a particle-antiparticle pair annihilate. If you annihilated a matter and antimatter star in a gamma-ray mirrored box, a nearby object would suddenly find itself in a deep gravity well, without the kinetic energy it should have gained by falling into that well. It's logically inconsistent and breaks conservation laws. And then there's the gravity lensing observations I mentioned. Antimatter having antigravity might seem like a good idea, but on closer inspection it just doesn't work.
You're forgetting to mention the assumption that photons (gamma-rays in this case) emit gravity, but I certainly agree.

Mjolnir wrote:
Absalom wrote:If you're willing to accept the possibly non-Euclidean implications of 'anti-matter emits anti-gravity' in the first place, then I don't think MORE weird behavior is going to slow you down.
...what?
This "weird behavior" logically follows from the assumption that such a reversal in gravitational effect exists. That it is completely at odds with observation shouldn't just slow you down, it should bring you to a complete stop as you re-evaluate your assumptions.
AS I SAID, if you're willing to accept the spacetime-curvature (yes, rephrasing) implications of 'anti-matter emits anti-gravity' in the first place, then I don't think MORE weird behavior is going to slow you down.

Let's use an analogy: Once your car has run off the cliff, the brakes won't help.

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Re: Dark Matter == Anti-gravity == Anti-matter gravity?

Post by Mjolnir »

Absalom wrote:What is the name of the SET of particles which includes protons, anti-protons, and any negative-matter analogues that they might have?
"Negative matter" is as close as I've seen, and it seems common to just call it exotic matter, though there are other kinds of exotic matter that don't have negative energy (some of which have been created and studied...muonium, positronium, Bose-Einstein condensates, etc). Given that it's a hypothetical form of matter that mainly exists to make certain wormholes and FTL drives possible, I don't think it needs anything more detailed.

Absalom wrote:
Mjolnir wrote:It's simply an observation that electrons are always created paired with a positron, and they annihilate with positrons to produce nothing but a burst of EM radiation. The mathematics describing electrons and positrons is identical, just reversed in time. Pair production can be seen as a positron going backwards in time becoming an electron going forwards in time, and annihilation as an electron reversing in time to become a positron. If all electrons and positrons came from such events, you only need one particle to describe all the electrons and positrons in the universe.
Which I extrapolated all the way down to having only one or two plank units of energy TOTAL, which just happen to be used for everything (including your single electron/positron). The theory is a nifty idea, but I can't comprehend any actual use for it.
Which is an overextrapolation. It is specifically an interpretation of the standard model of electrons. As for usefulness, exploration of the implications, possibilities, and limits of a model is generally considered useful.

Absalom wrote:Seriously, how are you even supposed to TEST this?
By testing the ability of the model to make accurate predictions. Do positrons behave like time reversed electrons? So far, a difference hasn't been found (the symmetry violations that have been found are specific to weak nuclear interactions). Are they ever created or destroyed individually? Not that we've seen.

Absalom wrote:
Mjolnir wrote:I'm not sure it's at all possible to produce an effect like antigravity with the geometric approach used by GR.
Fair enough, as I'm having trouble figuring out how to picture 'inverse curvature'. And no, I don't think that turning a picture of 'conventional gravitational curvature' upside down would be an accurate representation.
Right...that still puts the greater curvature on spacetime nearer the body. You could turn the standard "rubber sheet" model upside down, pulling the rubber "upward" into a hill. The trajectory of a test particle along the sheet will be the same, because it's not rolling "downhill" due to gravity in a higher dimension, it's following a trajectory along the rubber sheet that is locally a straight line.

Absalom wrote:
Mjolnir wrote:I also don't know what you're suggesting with the electrons.
I was suggesting that if anti-matter emits anti-gravity, then electrons should too, because when their (electrons and anti-protons, specifically) energies & masses are compared, they have the same sign (negative). I am, of course, assuming that the magnitude of the resulting value would be inconsequential to whether the particles emitted gravity or anti-gravity.
Electrons have positive rest energy and mass.

Absalom wrote:I was talking about wormholes, I thought it would be obvious from the mention of negative-matter. Is there something else that negative matter can supposedly prevent from collapsing?
Alright. Negative matter is needed to make stable wormholes because it would the gravitational forces trying to collapse the wormhole. Boson number doesn't come into it anywhere.

Absalom wrote:You're forgetting to mention the assumption that photons (gamma-rays in this case) emit gravity, but I certainly agree.
In GR, space-time is curved by mass-energy, there's no reason to think that electromagnetic energy is unusual. If photons don't curve spacetime, it is rather strange that general relativity holds together so well. Also, the observed phenomena of annihilation and pair production would allow conservation of energy to be broken due to the resulting shifts in gravitational potential energy. It's a pretty safe assumption.

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