9 ms·

New ALPHA-g Detector Poised to Search for Signs of Anti-Gravity

stephengillie 8y ago
> Understanding whether antimatter obeys the same laws of gravity as matter is an important step toward confirming whether decades of theory surrounding antimatter stand true. The Economist recently covered the same experiment at CERN: https://news.ycombinator.com/item?id=18110857 https://news.ycombinator.com/item?id=18110857
makotech222 8y ago
I don't understand why it wouldn't. Anti-matter has positive mass, which means it affects the curvature of spacetime the same way regular matter does.
blueprint 8y ago
This could be one of the most important experiments that modern physics has attempted. It's funny that they must adapt their schedule to others, and not the other way around. They're being given just a few days to carry everything out before hitting a cut-off point that may realistically cause the experiment never to get done due to changes in funding or the landscape. If they obtain a positive result, how many experts will suddenly no longer have a position of expertise? Suddenly, I wonder if they are having a harder time than other experiments, and whether there are any at CERN who actually don't want the experiment to occur.
- krastanov 8y ago
  It is silly to suggest conspiracy theories like that. This is not "one of the most important experiments that modern physics has attempted". Most physicist would say "the result is a forgone conclusion, but it is our job to double check". This is why the experiment is not a priority compared to experiments where the result is unknown. Yes, if it turns out that the result is positive, this would be enormously exciting, especially for these experts that you are worried would lose their expert status. It is just that scientist do not get excited over something that has pretty enormous chances of not happening.
  - blueprint 8y ago
    No, I'm not suggesting a conspiracy theory. If you think about it, there is no need for people to conspire to produce the effect. There is simply the clear psychological reaction that people tend to reject what contradicts the things they are deeply involved in and have already accepted. Does that mean all scientists who learn about and believe they understand the Standard Model have closed minds? No. But it does mean that individual scientists' judgement will tend to be influenced to give a lower priority to the things they think are less important. Please don't misrepresent my comment. As a side note if something is true then it has 100% chance of happening. If you don't know it's not true then you don't know about the enormity of its chances.
    - krastanov 8y ago
      Your last comment about chances shows misunderstanding of how science and/or statistics work. We have not tested our theories in every possible way, so yes, we know they will need updating here and there. However, there is an immense body of work pointing to no "antigravity", so the chance of a surprising result from this experiment is vanishingly small. If you are interested, check out Feynman's Quantum Field Theory textbook where he quite descriptively puts constraints on tensor interactions (like gravity). I would be happy to suggest more introductory books if you are interested.
- eganist 8y ago
  > If they obtain a positive result, how many experts will suddenly no longer have a position of expertise? This is true of most experimentation for novel theories, and it's true of many large experiments e.g. attempting to locate the Higgs Boson (the discovery of which invalidated many theories of physics just through confirming certain unknowns.) > Suddenly, I wonder if they are having a harder time than other experiments, and whether there are any at CERN who actually don't want the experiment to occur. Well, possibly, but not for the conspiratorial reasons you're alluding to. It's a powerful device with only so much time to operate; the usage of that time needs to be prioritized, and that prioritization can really only be accomplished by gauging the likelihood of an outcome which produces new knowledge (either validating a theory or invalidating it). No one behind the operation of the ALPHA-g detector is going to block an experiment because they may personally not like the results; if the detector has a hand in a successful discovery, the detector and the team supporting it will be able to claim having a hand in the discovery.
  - XorNot 8y ago
    The real issue is so far all the supporting evidence and theory says antimatter obeys normal rules of gravity. So it really is a long-shot experiment - if it actually differs in a significant way (and let's be clear: experiencing less gravity, going in a slightly different direction - anything - would be major) - then that would be a huge surprise.
    - eganist 8y ago
      Right, and if it turns up nothing, what does it invalidate? ...well, nothing. The negative conclusion of this experiment doesn't achieve anything, and the aspirational conclusion is a colossal longshot. So more likely than not, time is wasted here (though it'd be cool if there were a Discovery, or even just a 3σ observation).
    - blueprint 8y ago
      What evidence are you referring to which supports antimatter obeying "normal rules of gravity", by which I am presuming you mean gravitating in the same direction as matter?
- chr1 8y ago
  > how many experts will suddenly no longer have a position of expertise? None. Math stays the same, and the skills needed to solve the problems stay the same. In general new discoveries in physics only add detail to what we know and do not invalidate the old knowledge.
  - deleted 8y ago
    [deleted]
  - blueprint 8y ago
    > Math stays the same Not necessarily. How much calculus which is necessary to do modern physics has been built on discrete numbers? > do not invalidate the old knowledge Of course what is truly known will never be invalidated. But it's clear that the (rare?) situation in which something which is widely accepted turns out fundamentally flawed has the potential to make those who have proclaimed their strong confidence in it lose apparent credibility (not to mention many years of their life).
ars 8y ago
If anti-matter has anti-gravity, then the next question to answer is why do photons obey normal gravity? Are there anti-photons? (Presumably only anti-matter can make them.) Or is matter special because it matches photons gravitationally and thus answers the question of baryogenesis. That second option leads to some very interesting implications for stars made of anti-matter. Any photons they make would be "shoved" away from the star - but where does that energy come from? The first option means there are photons we can not detect (only anti-matter can make them, so only anti-matter can see them). That would imply there is an entire second universe out there overlayed on this one (at least photonically overlayed) that we have never seen, except gravitationally. But during annihilation events which type of photon would be produced? Both? Randomly one or the other? Finding that anti-matter has anti-gravity would open an absolutely enormous list of questions. It's not as simple, as OK, anti-gravity - every other part of physics would have to change as well.
- akiselev 8y ago
  Do we know that photons obey normal gravity? I was under the impression that we know that light can be bent by the warping of space-time due to gravity, but not that it interacts with the Higgs field. Photons don't really have an anti-matter pair that we can observe afaik because anti-particles have the same mass and spin but opposite charge as their counterpart. Since photons have no charge, a photons anti-matter pair is just another photon. Furthermore, we know that anti-hydrogen has the same spectral lines as hydrogen so their electromagnetic interactions are the same. Finding that anti-matter has anti-gravity would be world changing, though I'm setting my expectations very low. It would mean that we have access to the kind of exotic matter needed for a practical Alcubierre warp drive and could open up an entirely new field of space time engineering. It's just extremely unlikely, given all we know, that anti-matter has such properties.
  - marcosdumay 8y ago
    The Higgs field is not directly related to gravity. Linking gravity with quantum mechanics is still an ongoing research area.
  - 8y ago

> Understanding whether antimatter obeys the same laws of gravity as matter is an important step toward confirming whether decades of theory surrounding antimatter stand true. The Economist recently covered the same experiment at CERN: https://news.ycombinator.com/item?id=18110857 https://news.ycombinator.com/item?id=18110857

makotech222 8y ago

I don't understand why it wouldn't. Anti-matter has positive mass, which means it affects the curvature of spacetime the same way regular matter does.

blueprint 8y ago

This could be one of the most important experiments that modern physics has attempted. It's funny that they must adapt their schedule to others, and not the other way around. They're being given just a few days to carry everything out before hitting a cut-off point that may realistically cause the experiment never to get done due to changes in funding or the landscape. If they obtain a positive result, how many experts will suddenly no longer have a position of expertise? Suddenly, I wonder if they are having a harder time than other experiments, and whether there are any at CERN who actually don't want the experiment to occur.

krastanov 8y ago
It is silly to suggest conspiracy theories like that. This is not "one of the most important experiments that modern physics has attempted". Most physicist would say "the result is a forgone conclusion, but it is our job to double check". This is why the experiment is not a priority compared to experiments where the result is unknown. Yes, if it turns out that the result is positive, this would be enormously exciting, especially for these experts that you are worried would lose their expert status. It is just that scientist do not get excited over something that has pretty enormous chances of not happening.
- blueprint 8y ago
  No, I'm not suggesting a conspiracy theory. If you think about it, there is no need for people to conspire to produce the effect. There is simply the clear psychological reaction that people tend to reject what contradicts the things they are deeply involved in and have already accepted. Does that mean all scientists who learn about and believe they understand the Standard Model have closed minds? No. But it does mean that individual scientists' judgement will tend to be influenced to give a lower priority to the things they think are less important. Please don't misrepresent my comment. As a side note if something is true then it has 100% chance of happening. If you don't know it's not true then you don't know about the enormity of its chances.
  - krastanov 8y ago
    Your last comment about chances shows misunderstanding of how science and/or statistics work. We have not tested our theories in every possible way, so yes, we know they will need updating here and there. However, there is an immense body of work pointing to no "antigravity", so the chance of a surprising result from this experiment is vanishingly small. If you are interested, check out Feynman's Quantum Field Theory textbook where he quite descriptively puts constraints on tensor interactions (like gravity). I would be happy to suggest more introductory books if you are interested.
eganist 8y ago
> If they obtain a positive result, how many experts will suddenly no longer have a position of expertise? This is true of most experimentation for novel theories, and it's true of many large experiments e.g. attempting to locate the Higgs Boson (the discovery of which invalidated many theories of physics just through confirming certain unknowns.) > Suddenly, I wonder if they are having a harder time than other experiments, and whether there are any at CERN who actually don't want the experiment to occur. Well, possibly, but not for the conspiratorial reasons you're alluding to. It's a powerful device with only so much time to operate; the usage of that time needs to be prioritized, and that prioritization can really only be accomplished by gauging the likelihood of an outcome which produces new knowledge (either validating a theory or invalidating it). No one behind the operation of the ALPHA-g detector is going to block an experiment because they may personally not like the results; if the detector has a hand in a successful discovery, the detector and the team supporting it will be able to claim having a hand in the discovery.
- XorNot 8y ago
  The real issue is so far all the supporting evidence and theory says antimatter obeys normal rules of gravity. So it really is a long-shot experiment - if it actually differs in a significant way (and let's be clear: experiencing less gravity, going in a slightly different direction - anything - would be major) - then that would be a huge surprise.
  - eganist 8y ago
    Right, and if it turns up nothing, what does it invalidate? ...well, nothing. The negative conclusion of this experiment doesn't achieve anything, and the aspirational conclusion is a colossal longshot. So more likely than not, time is wasted here (though it'd be cool if there were a Discovery, or even just a 3σ observation).
  - blueprint 8y ago
    What evidence are you referring to which supports antimatter obeying "normal rules of gravity", by which I am presuming you mean gravitating in the same direction as matter?
chr1 8y ago
> how many experts will suddenly no longer have a position of expertise? None. Math stays the same, and the skills needed to solve the problems stay the same. In general new discoveries in physics only add detail to what we know and do not invalidate the old knowledge.
- deleted 8y ago
  [deleted]
- blueprint 8y ago
  > Math stays the same Not necessarily. How much calculus which is necessary to do modern physics has been built on discrete numbers? > do not invalidate the old knowledge Of course what is truly known will never be invalidated. But it's clear that the (rare?) situation in which something which is widely accepted turns out fundamentally flawed has the potential to make those who have proclaimed their strong confidence in it lose apparent credibility (not to mention many years of their life).

ars 8y ago

If anti-matter has anti-gravity, then the next question to answer is why do photons obey normal gravity? Are there anti-photons? (Presumably only anti-matter can make them.) Or is matter special because it matches photons gravitationally and thus answers the question of baryogenesis. That second option leads to some very interesting implications for stars made of anti-matter. Any photons they make would be "shoved" away from the star - but where does that energy come from? The first option means there are photons we can not detect (only anti-matter can make them, so only anti-matter can see them). That would imply there is an entire second universe out there overlayed on this one (at least photonically overlayed) that we have never seen, except gravitationally. But during annihilation events which type of photon would be produced? Both? Randomly one or the other? Finding that anti-matter has anti-gravity would open an absolutely enormous list of questions. It's not as simple, as OK, anti-gravity - every other part of physics would have to change as well.

akiselev 8y ago
Do we know that photons obey normal gravity? I was under the impression that we know that light can be bent by the warping of space-time due to gravity, but not that it interacts with the Higgs field. Photons don't really have an anti-matter pair that we can observe afaik because anti-particles have the same mass and spin but opposite charge as their counterpart. Since photons have no charge, a photons anti-matter pair is just another photon. Furthermore, we know that anti-hydrogen has the same spectral lines as hydrogen so their electromagnetic interactions are the same. Finding that anti-matter has anti-gravity would be world changing, though I'm setting my expectations very low. It would mean that we have access to the kind of exotic matter needed for a practical Alcubierre warp drive and could open up an entirely new field of space time engineering. It's just extremely unlikely, given all we know, that anti-matter has such properties.
- marcosdumay 8y ago
  The Higgs field is not directly related to gravity. Linking gravity with quantum mechanics is still an ongoing research area.
- 8y ago