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Does anti-gravity, as a force, exist?
Hello... It seems everything in his world has an opposite:
up/down..Left/right..Positive/negative...good/evil...action/reaction etc. etc. ...But what about gravity? ...Is there a known opposite force, other than one that can be simulated? Thanks... Jon |
#2
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Does anti-gravity, as a force, exist?
Dear Johnny1000:
wrote in message ... Hello... It seems everything in his world has an opposite: up/down..Left/right..Positive/negative... good/evil...action/reaction etc. etc. These are labels, not "facts". They stand between you and reality. It is one curse of being bifurcated. ...But what about gravity? ...Is there a known opposite force, other than one that can be simulated? 1) Gravity is not a force. It can be represented as one in certain simple models, such as what they have time to teach you in high school. 2) In cosmological expansion, Dark Energy is counter to the "mutually attractive effects" of gravity. But it only "kicks in" at very large distance scales. David A. Smith |
#3
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Does anti-gravity, as a force, exist?
David,
You dismissed some examples of pairs of opposites as "labels, not facts". It looks to me like your assertion applies only to the words, not the things those words label. Many things *do* have opposites. Up and down are obviously opposite to each other. Positive and negative are clearly opposites. Your dismissal appears to be completely unjustified. It is obvious that gravity is a force. It was the first force to be described mathematically, by Galileo and Newton. Saying that it is not a force is not only counter to all experience, but counter to most physics textbooks. When you don't explain what you mean by the statement and back it up with evidence, you look like a kook. -- Jeff, in Minneapolis |
#4
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Does anti-gravity, as a force, exist?
Dear Jeff Root:
"Jeff Root" wrote in message ups.com... David, You dismissed some examples of pairs of opposites as "labels, not facts". It looks to me like your assertion applies only to the words, not the things those words label. The "things" those words label are abstract concepts that are necessarily removed from reality. Many things *do* have opposites. Up and down are obviously opposite to each other. Not if I live in Austrailia and you in America. Your up is my down, and vice versa. "Vertical axis" is at least unitary, but not absolute since others will not see it as "vertical". To be "opposite" is to have something in common with the opposite. So it is really gradations of sameness. Positive and negative are clearly opposites. Your dismissal appears to be completely unjustified. Positive and negative have something in common... charge. It does not always add to understanding to divide a unity in "half" and proclaim "look there are two parts"! It is obvious that gravity is a force. It was the first force to be described mathematically, by Galileo and Newton. Force has been described much longer than that, even mathematically. Saying that it is not a force is not only counter to all experience, but counter to most physics textbooks. When you don't explain what you mean by the statement and back it up with evidence, you look like a kook. http://hermes.physics.adelaide.edu.au/~dkoks/Faq/ http://math.ucr.edu/home/baez/physic...particles.html http://math.ucr.edu/home/baez/physic...rav_speed.html QUOTE Strictly speaking, gravity is not a "force" in general relativity, and a description in terms of speed and direction can be tricky. END QUOTE Consider that Newton himself was very uncomfortable with "action at a distance". And if you think I need to look like a kook, go ahead and think that. There are two kinds of people in the world... ;) David A. Smith |
#5
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Does anti-gravity, as a force, exist?
"Jeff Root" ha scritto nel messaggio
ups.com... It is obvious that gravity is a force. It was the first force to be described mathematically, by Galileo and Newton. Saying that it is not a force is not only counter to all experience, but counter to most physics textbooks. Before Einstein this was true, and obvious... But after General Relativity Theory gravity is defined as only a space geometrical property. Space is curved in presence of mass and in this way you don't need any force to justify attraction between masses. Is the space deformation itself that generates gravity. Luigi Caselli |
#6
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Does anti-gravity, as a force, exist?
In message , Luigi Caselli
writes "Jeff Root" ha scritto nel messaggio oups.com... It is obvious that gravity is a force. It was the first force to be described mathematically, by Galileo and Newton. Saying that it is not a force is not only counter to all experience, but counter to most physics textbooks. Before Einstein this was true, and obvious... But after General Relativity Theory gravity is defined as only a space geometrical property. Space is curved in presence of mass and in this way you don't need any force to justify attraction between masses. Is the space deformation itself that generates gravity. Don't quantum gravity theories require a graviton? Most particles have an antiparticle, though the photon is its own antiparticle so there's no reason to expect antigravity from that direction. The graviton, if it exists, may also be its own antiparticle. Anyway, the experiment to see if antimatter is attracted by gravity hasn't yet been done, AFAIK. |
#7
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Does anti-gravity, as a force, exist?
"Jonathan Silverlight" ha
scritto nel messaggio ... In message , Luigi Caselli writes "Jeff Root" ha scritto nel messaggio oups.com... It is obvious that gravity is a force. It was the first force to be described mathematically, by Galileo and Newton. Saying that it is not a force is not only counter to all experience, but counter to most physics textbooks. Before Einstein this was true, and obvious... But after General Relativity Theory gravity is defined as only a space geometrical property. Space is curved in presence of mass and in this way you don't need any force to justify attraction between masses. Is the space deformation itself that generates gravity. Don't quantum gravity theories require a graviton? Only if you believe in quantum gravity... Most particles have an antiparticle, though the photon is its own antiparticle so there's no reason to expect antigravity from that direction. The graviton, if it exists, may also be its own antiparticle. Anyway, the experiment to see if antimatter is attracted by gravity hasn't yet been done, AFAIK. And if antimatter is attracted by gravity what is the conclusion of this story? Luigi Caselli |
#8
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Does anti-gravity, as a force, exist?
Dear
"Jonathan Silverlight" wrote in message ... .... Anyway, the experiment to see if antimatter is attracted by gravity hasn't yet been done, AFAIK. http://math.ucr.edu/home/baez/physic...atterFall.html http://www.science.ca/askascientist/...on.php?qID=164 Yes, the only question is is it attracted exactly the same way. Since antimatter can be considered as "time reversed" matter, and since the Earth doesn't fly apart (all at once) by reversing time with a camera, I would fully expect antimatter to behave exactly as does matter. David A. Smith |
#9
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Does anti-gravity, as a force, exist?
Standard theory says there is no such thing as an anti-gravity force.
However, the theoretical arguments(yes, Baez's argument("Morrison argument") included) for this are fairly weak, in my humble opinion. I think there is enough wiggle room in the experimental evidence to allow for the possibility that antimatter falls up. That is that antimatter and matter repel each other gravitationally, but attract their own kind. Anyways, the earth example is silly. An antimatter Earth would not be expected to repel itself. |
#10
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Does anti-gravity, as a force, exist?
In article . com,
Intangir wrote: Standard theory says there is no such thing as an anti-gravity force. However, the theoretical arguments(yes, Baez's argument("Morrison argument") included) for this are fairly weak, in my humble opinion. I think there is enough wiggle room in the experimental evidence to allow for the possibility that antimatter falls up. That is that antimatter and matter repel each other gravitationally, but attract their own kind. Anyways, the earth example is silly. An antimatter Earth would not be expected to repel itself. If anti-matter would "fall up", that would imply different gravitational and inertial masses for anti-matter: the gravitational mass of anti-matter would be negative, making anti-matter being repulsed by gravity. But the inertial mass of anti-matter would still be positive, so that the response of the anti-matter to that repulsive force would be the expected response: to move away. Now, finding some matter having different inertial and gravitational masses would be a clear contradiction of General Relativity. So anyone who wants to "disprove Einstein", here's your opportunity: try to verify experimentally that in a gravitational field, anti-matter will "fall up". ------------------------------------------------------------------------- If we want to follow the equivalence pronciple of General Relativity, and still want to assign a negative gravitational mass to anti-matter, then its inertial mass must also be negative. This will have some weird consequences: if some force acts on the antimatter, it will move in the opposite direction than expected, since its inertial mass is negative. This alone would make any atom of anti-matter unnterly instable: the attractive force between the antielectrons and antiprotons would make the atom rapidly fall apart instead of holding it together. Otoh no strong nuclear force would be needed to keep the antiprotons in the core of the atom together - the repulsive electrical force between the equally charged antiprotons would keep them firmly in place! Anti-matter does not behave in this way. Antiparticles are repelled, not attracted, by repulsive forces. Numerous experiments have confirmed that antimatter has positive inertial mass. And if the equivalence principle of General Relativity is valid for antimatter too, then this implies that antimatter also must have positive gravitational mass. ------------------------------------------------------------------------- Finally, let's make a simple thought experiment, where we have two bodies, A and B, both initially at rest, where A has normal positive mass and B has an equal but negative mass. This applies to both gravitational and inertial masses, so the equivalence principle is assumed to be valid. The only significant force on these bodies is assumbed to be their mutual gravitational forces. All other forces (electrical, nuclear, whatever) are assumed to be negligible. What would happen? First the mutual gravity between the two bodies would be negative, i.e. a repulsive gravitational force, since the two bodies have different signs in their masses: A has positive mass and B has negative mass. So the only significant force on these bodies would be a repulsive gravitational force. Now, how would these to bodies react on this repulsive force? Body A, with positive inertial mass, would behave as expected: it would start to move away from body B. Body B, with negative inertial mass, would not behave as we're used to: it would start to move TOWARDS body A. The net result would be quite amusing: body B would start "chasing" body A. The distance between bodies A and B would remain unchanged, while both bodies would accelerate all the time - the only upper limit of their speeds would be the relativitistic light speed limit. But from where would their kinetic energy come?", I hear you ask. Well, the sum of their kinetic energy, which was zero at the start, would remain zero all the time while they accelerated: body A, with positive mass, would of course get more and more kinetic energry as it accelerated, but body B, with negative mass, would at all times have an equal amount of NEGATIVE kinetic energy as it accelerated. ---------------------------------------------------------------------------- As you can see, trying to introduce negative masses would imply some quite strange behaviour in bodies with negative masses. And there's an asymmetry in the behaviour too: an atom built with particles with negative mass would behave quite differently than a normal atom, with particles having positive mass. And in the last example here, with a negative and a positive mass interacting, the negative mass would start "chasing" the positive mass - not the other way around. I think we can safely conclude that negative masses do not exist. If they did exist, our universe would be a quite different place than it is. -- ---------------------------------------------------------------- Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN e-mail: pausch at stockholm dot bostream dot se WWW: http://stjarnhimlen.se/ |
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