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Thread: Negative mass

  1. #1

    Exclamation Negative mass

    I am assuming that for every particle, there is an anti-particle. So is there any such thing as negative mas? If we can make a mass object made of anti-atoms, then is the general charge of that mass negative.? So I am also assuming that Dark Matter is also made of positive mass. Or everything we see is positive. Or so?

  2. #2
    If Newton's equations hold true for negative masses, than pushing it would cause it to move towards you, whereas pulling it would cause it to move away from you. Gravitational attraction [between positive and negative masses] would still work the same, though (I'll concede to the next poster to explain that).

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    Bear in mind that negative matter and antimatter are two completely different things. I'm not sure if every particle has an anti particle, but I believe every massive particle has an antiparticle.

    positrion - electron
    antiproton - proton
    neutron - antineutron.

    The only difference is the particle's charge. Though, I'm not sure how one differentiates between a neutron and an antineutron since it's electrically neutral.

    Negative matter is a different beast altogether. It is hypothetical and there is no direct evidence for it.
    Here's a good introductory read:
    http://en.wikipedia.org/wiki/Exotic_matter
    And this, though a little more heady:
    http://209.85.173.132/search?q=cache...lnk&cd=6&gl=us

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    Quote Originally Posted by m74z00219 View Post
    The only difference is the particle's charge.
    Depends what sort of differences you are talking about. In the case of hadrons, which are made up of several quarks (usually 2 or 3), the antiparticle is often made up of quite different quarks from the particle, specifically, the respective antiquarks. So a proton is made up of two up quarks and a down quark, but an antiproton is made up of two up antiquarks and a down antiquark, three entirely different quarks. So the difference between proton and antiproton could be said to be more than just the charge. This is why an antineutron is different from a neutron and can annihilate it, it is made of three entirely different quarks.

    Mesons are (to a first approximation) made up of a quark-antiquark pair. When they are the same flavour, then that meson is neutral and its own anti-particle. For example, the eta mesons.

    Leptons are trickier, especially when they are neutral leptons. It seems to be the case that leptons, like quarks, come in particle/antiparticle pairs of opposite charge, at least for the charged leptons. The neutral leptons are more problematic. It remains unclear quite what is the difference between a neutrino and an antineutrino. They have opposite helicity (handedness), but maybe the helicity can change and really neutrino and antineutrinos are the same things, just in a different state.

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    Quote Originally Posted by WHITE_HOLE View Post
    I am assuming that for every particle, there is an anti-particle. So is there any such thing as negative mas?...
    Perhaps you are asking about the existence of anti-gravitons. So far they aren't theorized. If they find anti-photons, I suppose they'll look for anti-gravitons next. The hard facts are as gzhpcu points out, discussed in great detail in several other threads.
    Forming opinions as we speak

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    Quote Originally Posted by antoniseb View Post
    Perhaps you are asking about the existence of anti-gravitons.
    So far they aren't theorized. If they find anti-photons, I suppose
    they'll look for anti-gravitons next.
    Has somebody hypothesized anti-photons??? I'm interested!

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Anti-Photons? Heh, what would they do? Project darkness and take heat away from objects?

    And Anti-Gravitons? Wow, let's try to find out if the normal kind even exist yet, before we start talking about the anti-particle.

    Though I suppose either of those would be good for Sci-Fi. "Fire the Anti-Laser!"

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    anti-photon

    The anti-photon is the photon. They are their own anti-particle, so they are not only hypothesized, they have been found and are indistinguishable from the regular photon..
    Circa 1991...ish,.. they trapped an antiproton in a Penning trap and concluded it behaved like a particle with "regular" mass,too. pete

    see:http://www.iop.org/EJ/abstract/1402-4896/46/3/010

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    Quote Originally Posted by WHITE_HOLE View Post
    I am assuming that for every particle, there is an anti-particle.
    Well, careful how you put this. When physicists create particles in accelerators, they are always created in particle-antiparticle pairs. But if you look around the universe, "for every particle," the corresponding antiparticles are nowhere to be found. We can confidently say that if all those antiparticles exist at all, they are not within our visible universe.

    Current thinking is that just after the so-called big bang, all the particles and antiparticles annihilated to produce photons. Well, almost all. For every billion annihilations, one particle couldn't find an antiparticle to annihilate with. These leftovers are what make up all the regular matter in our universe. We notice that there are about a billion photons for every proton or neutron, and most of those by far are CMB photons.

    Quote Originally Posted by WHITE_HOLE View Post
    So is there any such thing as negative mass?
    No. Gravity is always positive and attracting. Charge can be positive or negative.
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by trinitree88 View Post
    The anti-photon is the photon. They are their own anti-particle,
    Is there evidence to support that beyond the lack of evidence
    for the existence of two separate particles? Can you describe
    the theoretical reasons for believing that the photon is its own
    antiparticle?

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Quote Originally Posted by Jeff Root View Post
    Is there evidence to support that beyond the lack of evidence
    for the existence of two separate particles? Can you describe
    the theoretical reasons for believing that the photon is its own
    antiparticle?
    I believe it's part of the definition for an uncharged boson.
    Antiparticles are defined as having the same mass and spin as their counterparts, but opposite values for the other conserved quantities: charge, colour, flavour, lepton number, baryon number. Since photons lack all of these numbers, there is no way to distinguish an antiphoton from a photon.

    Grant Hutchison

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    Quote Originally Posted by Cougar View Post
    No. Gravity is always positive and attracting. Charge can be positive or negative.
    Not so sure if you can definitely say no. Hermann Bondi came up with the concept of negative mass:

    In 1957, Hermann Bondi suggested in a paper in Reviews of Modern Physics that mass might be negative as well as positive [1]. He pointed out that this does not entail a logical contradiction, as long as all three forms of mass are all negative, but that the assumption of negative mass involves some counter-intuitive form of motion.
    source: http://en.wikipedia.org/wiki/Exotic_matter

    and it has recently been proposed as a possible explanation of Hawking Radiation:

    Several different explanations of Hawking radiation can be found in popular descriptions. A few of these explanations are summarized below.

    (1) Quantum fluctuations lead to the production of pairs of particles and anti-particles just outside the horizon; one of these falls into the black hole and the other escapes as radiation with positive mass-energy. The in-falling particle has negative mass-energy, so its absorption results in a reduction in the mass-energy of the black hole.
    source: http://www.mathpages.com/home/kmath591/kmath591.htm

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    Quote Originally Posted by gzhpcu View Post
    and it has recently been proposed as a possible explanation of Hawking Radiation:

    source: http://www.mathpages.com/home/kmath591/kmath591.htm
    That's a different matter from a negative rest-mass, however. If you were to fall alongside the particle that crosses the event horizon (the infalling counterpart to the Hawking radiation), you'd find it to be a perfectly ordinary particle with positive mass.
    The "negative energy" only appears in the accounting of a distant observer, and is due to the difference in reference frames between particle and observer.

    Grant Hutchison

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    Quote Originally Posted by gzhpcu View Post
    Not so sure if you can definitely say no. Hermann Bondi came up with the concept of negative mass....
    Hermann Bondi? Ha ha ha ha ha! You mean Hermann Bondi, who is best known for developing the steady-state theory of the universe with Fred Hoyle? Ha ha ha ha!

    OK, OK, Bondi was probably 100 times the cosmologist that I will ever be, and my unequivocal "no" to "negative mass" is probably going out on a limb... but it is a very massive limb, made entirely of positive matter, without so much as a quark's worth of antimatter or negative mass.
    Everyone is entitled to his own opinion, but not his own facts.

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    Question

    Quote Originally Posted by Jeff Root View Post
    Is there evidence to support that beyond the lack of evidence
    for the existence of two separate particles? Can you describe
    the theoretical reasons for believing that the photon is its own
    antiparticle?

    -- Jeff, in Minneapolis
    Jeff. Hi. There's a few webbies, such as:http://www.mathpages.com/home/kmath246.htm I was in an audience of teachers in a particle physics course at MIT's Bates Accelerator, and one of them asked a presenter (Peter Demos, or Larry Sulak, I think)...the same question.
    and at the Stanford Linear Accelerator...SLAC...the virtual tour guide says it too:http://www2.slac.stanford.edu/vvc/th...ntiquarks.html pete
    Last edited by trinitree88; 2009-Feb-07 at 05:27 PM. Reason: links

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    Quote Originally Posted by grant hutchison View Post
    That's a different matter from a negative rest-mass, however. If you were to fall alongside the particle that crosses the event horizon (the infalling counterpart to the Hawking radiation), you'd find it to be a perfectly ordinary particle with positive mass.
    The "negative energy" only appears in the accounting of a distant observer, and is due to the difference in reference frames between particle and observer.
    What I do not understand is the following: when a particle and an antiparticle annihilate each other energy is released in the form of a photons, whereas in quantum foam the virtual particles annihilate each other with no photons/energy released. Virtual particles do not behave like normal particle - antiparticles.

  18. #18
    Quote Originally Posted by gzhpcu View Post
    What I do not understand is the following: when a particle and an antiparticle annihilate each other energy is released in the form of a photons, whereas in quantum foam the virtual particles annihilate each other with no photons/energy released. Virtual particles do not behave like normal particle - antiparticles.
    Wouldn't that violate conservation of energy if they did?

    Nick

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    Quote Originally Posted by gzhpcu View Post
    Virtual particles do not behave like normal particle - antiparticles.
    That's what makes them virtual. Their energy exists only for the time stipulated by Heisenberg: so they cannot come from, or annihilate to, long-lived particles like photons.

    Grant Hutchison

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    Quote Originally Posted by Nick Theodorakis View Post
    Wouldn't that violate conservation of energy if they did?

    Nick
    The thing is, that with Hawking radiation, the particle which escapes becomes real...

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    Quote Originally Posted by gzhpcu View Post
    The thing is, that with Hawking radiation, the particle which escapes becomes real...
    So its energy has to come from somewhere: the gravitational field of the black hole.

    Grant Hutchison

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    Quote Originally Posted by gzhpcu View Post
    What I do not understand is the following: when a particle and an
    antiparticle annihilate each other energy is released in the form of
    photons, whereas in quantum foam the virtual particles annihilate
    each other with no photons/energy released. Virtual particles do
    not behave like normal particle - antiparticles.
    My understanding is that the energy of a virtual particle pair is
    "borrowed" from spacetime. It can be borrowed for only a limited
    time before it has to be returned. The length of time depends on
    the amount of energy borrowed. The more energy borrowed, the
    sooner it has to be returned. If it were not returned before the
    time limit, the particles would become "physical" and could be
    detected directly. Virtual particles cannot be detected directly
    because they return their energy to spacetime before the time
    limit is reached.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Quote Originally Posted by Jeff Root View Post
    My understanding is that the energy of a virtual particle pair is
    "borrowed" from spacetime. It can be borrowed for only a limited
    time before it has to be returned. The length of time depends on
    the amount of energy borrowed. The more energy borrowed, the
    sooner it has to be returned. If it were not returned before the
    time limit, the particles would become "physical" and could be
    detected directly. Virtual particles cannot be detected directly
    because they return their energy to spacetime before the time
    limit is reached.

    -- Jeff, in Minneapolis
    Yes, it is allowed due to the Heisenberg Uncertainty Principle. When they annihilate each other before detection, no photons/energy is released.
    Quote Originally Posted by grant hutchison View Post
    So its energy has to come from somewhere: the gravitational field of the black hole.

    Grant Hutchison
    Yes, the black hole slowly evaporates as a virtual particle from the quantum foam is captured.

    What I am saying, is that the escaping particle becomes "real", can be detected. So, isn't the virtual particle a real particle, which is so short-lived that it can not be detected? If so, why is there no energy release when the virtual particle pairs annihilate each other?

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    Quote Originally Posted by gzhpcu View Post
    What I am saying, is that the escaping particle becomes "real", can be detected. So, isn't the virtual particle a real particle, which is so short-lived that it can not be detected? If so, why is there no energy release when the virtual particle pairs annihilate each other?
    Because it's not a real particle! The escaping particle becomes real because it receives energy to "promote" it from its virtual status: it can continue to exist beyond the limit set by Heisenberg. A virtual particle is a quantity of energy that exists for a very short time period, and then simply disappears. In order to conserve quantities like charge and lepton number during its brief existence, it has to be created with, and annihilate with, its own antiparticle.

    Grant Hutchison

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    Quote Originally Posted by trinitree88 View Post
    Quote Originally Posted by Jeff Root
    Is there evidence to support that beyond the lack of evidence
    for the existence of two separate particles? Can you describe
    the theoretical reasons for believing that the photon is its own
    antiparticle?
    Jeff. Hi. There's a few webbies, such as:
    http://www.mathpages.com/home/kmath246.htm I was in an
    audience of teachers in a particle physics course at MIT's Bates
    Accelerator, and one of them asked a presenter (Peter Demos,
    or Larry Sulak, I think)...the same question.
    and at the Stanford Linear Accelerator...SLAC...the virtual tour
    guide says it too:http://www2.slac.stanford.edu/vvc/th...ntiquarks.html
    Thanks.

    I gather that the first page is rather old. It says four types of
    neutrinos exist: the electron and muon neutrino and their two
    anti-particles.

    I'm attracted by the notion, suggested near the end of that page,
    that "helicity is not the only distinction between neutrinos and
    anti-neutrinos." I would apply that to photons. For example, if
    the energy of a photon were contained entirely within a single
    wavelength, then there would be four possible configurations of
    its electric and magnetic fields:

    Jeff's hypothetical photon configurations

    I'm afraid that, confusingly, the two on the left follow the
    right-hand rule, while the the two on the right follow a left-hand
    rule. The top two have positive first and negative after, while
    the bottom two have negative first and positive after. Again,
    this is just an example of a way photons might possibly differ
    from one another.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Quote Originally Posted by Jeff Root View Post
    I gather that the first page is rather old. It says four types of
    neutrinos exist: the electron and muon neutrino and their two
    anti-particles.
    I guess old. At any rate, wrong. Add in the Tau neutrino and its antineutrino. Three flavors, each with an anti-
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by grant hutchison View Post
    Because it's not a real particle! The escaping particle becomes real because it receives energy to "promote" it from its virtual status: it can continue to exist beyond the limit set by Heisenberg. A virtual particle is a quantity of energy that exists for a very short time period, and then simply disappears. In order to conserve quantities like charge and lepton number during its brief existence, it has to be created with, and annihilate with, its own antiparticle.

    Grant Hutchison
    From a Scientific American article "Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum mechanics?"

    Thus virtual particles are indeed real and have observable effects that physicists have devised ways of measuring. Their properties and consequences are well established and well understood consequences of quantum mechanics.
    source: http://www.sciam.com/article.cfm?id=...-particles-rea

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    Terminology: Virtual photons and physical photons. Both are real.

    I first learned about virtual particles in an article by Yuval Ne'eman
    in the World Book 1968 Science Year. It is clear and concise:
    When electrons violently collide, as they do in the sun or in the hot
    filament of a light bulb, small bundles of kinetic energy are knocked
    free. The electrons slow down, due to dispersion of some of their
    kinetic energy. These energy bundles, called photons, carry the
    electromagnetic force that moves electrons in your eye-- and you
    can see.

    Photons, then, should also carry the force that exists between two
    charged particles even when neither is moving. Although the static
    charge on a too-easy-to-charge nylon shirt is often a nuisance, it is
    scientifically illuminating. For the charge is not moving and can have
    no kinetic energy, yet it does emit photons. I know of them because
    they make the hair on my arm stand up. I cannot see these photons,
    however, even when I am using the finest laboratory instruments.

    A powerful principle of physics, the principle of uncertainty, explains
    why we can observe some photons as lumps of energy but not detect
    the energy of other photons at all. A photon is the smallest amount
    of energy that we can measure. We must wait for all its energy to
    pass by us or see none of it. A definite amount of time, then, depending
    on the energy of the photon, is needed to detect it. The principle says,
    for example, that a single photon of green light, 2 x 10^-6 mev of energy,
    can be observed only if it exists longer than a million-billionth (10^-15) of
    a second of time. When this photon exists for a shorter time, it cannot
    be detected.

    No photon having measurable energy can be emitted by a static charge
    on my shirt, but unobservable photons can freely emerge from it at the
    speed of light and act on a hair. Thus, a stream of "virtual" photons--
    so called to distinguish them from the "physical" photons that we can
    observe-- carries the charges' attraction or repulsion. The less energy
    a virtual photon has, the longer the time it can act. Thus the farther
    apart two charges are, the longer the virtual photons take to leap
    between them, the smaller the energy the photons can possess, and
    the weaker the force they transmit. The electromagnetic force has an
    infinite range; infinitely weak virtual photons reach out from each charge
    to the very horizon of the universe.

    This also holds for the gravitational force. Its action is transmitted,
    also at the speed of light, by particles of energy called gravitons.
    Though virtual when simply binding the earth to its orbit around the sun,
    they are, according to theory, emitted physically whenever matter is
    accelerated. Gravitons must be exceedingly feeble. They have never
    been observed.
    I wrote to Ne'eman asking for more info about virtual particles, but he
    suggested I get his book, 'The Particle Hunters'. It was a bit pricey,
    so I haven't seen it.

    -- Jeff, in Minneapolis
    Last edited by Jeff Root; 2009-Feb-08 at 09:15 AM. Reason: fix typo
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Interesting comments everyone! I seem to recall reading somewhere that if negative mass did in fact exist, its bizarre properties would make the perfect space travel. And I don't think we have reason to deny its existence; nor do we have reason to actually believe in it. We just lack direct evidence is all.

    I've always been fascinated with the idea of negative mass ever since the day I first heard of it.

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    The link gzhpcu has in post #27 to sciam.com made my browser
    (IE 5.5) start opening new windows at a rate of about one or two per
    second. They kept opening after I unplugged the cord to the modem.
    I finally got it to stop with Alt-Ctrl-Del and going down to the bottom
    of the long list of windows, finding the lowest one that said "Scientific
    American", and clicking End task.

    That has happened before on a SciAm page.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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