Antimatter, Negative Mass, & Gravity: Unveiling the Mysteries

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Discussion Overview

The discussion revolves around the properties of antimatter, particularly its interaction with gravity, the concept of negative mass, and whether antimatter behaves differently from normal matter in gravitational fields. Participants explore theoretical implications, experimental challenges, and the definitions of antimatter.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants assert that antimatter reacts to gravity in the same way as normal matter, challenging the idea that it has antigravity properties.
  • Others argue that the terminology surrounding antimatter is misleading, emphasizing that it is still matter with opposite charges for certain particles.
  • There are claims that experiments have not definitively shown whether antimatter has positive or negative gravitational effects, with references to ongoing research at CERN and Fermilab.
  • Concerns are raised about the feasibility of conducting gravity experiments with charged antimatter due to the dominance of electromagnetic forces over gravitational effects.
  • Some participants recall historical plans for experiments designed to test the gravitational behavior of antiprotons, questioning whether such experiments have been conducted or achieved conclusive results.
  • Discussions include the idea that the labels of matter and antimatter are arbitrary and do not affect the fundamental physics governing their interactions.

Areas of Agreement / Disagreement

Participants express disagreement on the nature of antimatter's interaction with gravity, with some asserting it behaves like normal matter while others question this assumption. The discussion remains unresolved regarding the definitive experimental evidence for these claims.

Contextual Notes

Limitations include the lack of definitive experimental results regarding the gravitational behavior of antimatter and the challenges posed by electromagnetic forces in conducting such experiments. The discussion also reflects uncertainty about the historical context of proposed experiments.

Who May Find This Useful

This discussion may be of interest to those studying particle physics, gravitational theory, and the properties of antimatter, as well as individuals curious about the experimental challenges in these areas.

  • #31
Isn't it a hole in a sea of negative-energy states, so the hole represents absence of negative-energy?
 
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  • #32
The sea of negative energy states is normally packed full of electrons, and this vacuum state has no net gravitational attraction, since the sea of electrons is homogeneous and isotropic. Now if we remove one of these electrons and send it some where far away, then all that is left is a hole where that electron used to be. Because of the hole the sea is no longer isotropic or homogeneous, and so if you are an ordinary matter particle looking at the hole then you have an infinite line of mass behind you, and an infinite - 1 line of electrons in front of you, therefore you will be pulled backwards, away from the hole.

Mathematically, I had to think carefully because normally a single point does not contribute to an integral, but in this case the mass of the hole, if we imagine it as being an empty site on a lattice with all other sites occupied, is less than the mass on neighboring sites by a factor of infinity, and so a delta function is appropriate which renders allows the integral to be effected in a finite way by the subtraction of a single point.
 
  • #33
Bob S said:
protons are uud, neutrons are udd, I believe that anti-protons are u-bar,u-bar,d-bar, anti-neutrons are u-bar,d-bar,d-bar.

That's a very superficial view. Those are the valence quarks. The proton is also composed of gluons, and sea quark-antiquark pairs. In fact, the parts other than the valence quarks carry the majority of the momentum of a proton.

I maintain my previous position - a different pull on matter and antimatter would yield a composition dependent force. Which is not observed.
 
  • #34
I know almost nothing about this, so I'll probably find myself in the sea over my head, but here goes ... :rolleyes:
ExactlySolved said:
The sea of negative energy states is normally packed full of electrons,

So isn't it a sea of negative energy electrons?
and this vacuum state has no net gravitational attraction, since the sea of electrons is homogeneous and isotropic.

This is true if the sea were all the electrons were positive energy, or if the see were all negative energy electrons.
ExactlySolved said:
Now if we remove one of these electrons and send it some where far away, then all that is left is a hole where that electron used to be.

Where a negative energy electron used to be? Thus, if a normal positive energy electron drops into the hole, it falls to a lower energy (in this case, negative) and emits radiation; pait annihilation.
ExactlySolved said:
Because of the hole the sea is no longer isotropic or homogeneous, and so if you are an ordinary matter particle looking at the hole then you have an infinite line of mass behind you, and an infinite - 1 line of electrons in front of you, therefore you will be pulled backwards, away from the hole.

Shouldn't "infinite line of mass behind you" be "infinite line of negative energy behind you", etc., so a normal electron is pulled (gravitationally) towards the hole?
 
  • #35
It is correct that the electrons in the dirac sea have negative energy, so this together with what GR says about the gravitational effect of negative energy would resolve the contradiction, thanks George.

It looks like what I said would be true for a large homogeneous mass of ordinary matter with a hole in it, the hole could be treated as a gravitational repeller, my mistake was extending this picture too far.
 

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