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I've read about how antimatter can be modeled as matter traveling backwards in time before but always viewed this as a sort of mathematical curiosity.

With this question I'm not so much asking if antimatter is for a fact backwards-traveling matter, so much as asking what the result of that would be, and if it is testable in itself.

From my understanding of it antimatter can be created in high energy collisions of matter, converting some of that matter into antimatter in the process. Similarly, antimatter and matter will annihilate to form pure energy on the other end.

Looking at this from a timeline of events it seems like it could be modeled as matter all around.

From the perspective of forward-time:

  1. Matter collides with matter with significant energy, resulting in a super-high energy density region of spacetime.

  2. Matter and antimatter come out of the resulting reaction and appear to move in forward time while the energy is largely lost in the form of creating the antimatter, the matter component of this can be disregarded as uninteresting.

  3. The antimatter particle eventually collides with matter to transform into high energy, "annihilating" both the matter and antimatter particles involved in the process.

From the perspective of backwards-time:

  1. A super high energy density region of spacetime exists.

  2. Matter and antimatter come out moving in different directions, the matter component is disregarded as uninteresting.

  3. The antimatter particle eventually collides with matter, resulting in high energy imparted to the original matter particles.

From this perspective it seems like the antimatter is just the conversion of energy to matter coupled with a different temporal vector. That is to say that the antimatter particle was never the antimatter particle at all, but the same matter particle moving backwards in time and streaming along entropic lines of force from low energy density to high energy density, ultimately destined to annihilate upon reaching a high enough energy density to cause a flip in the temporal vector (the way things will always get pushed into other dimensions when hit with enough force to overcome whatever is constraining them to the original dimension in a head-on collision, typically just in uninteresting/intuitive ways over 3 spatial dimensions.)

Viewing things in this manner seems to suggest that you could potentially test this notion of antimatter just being backwards-travelling matter by creating an experimental setup wherein:

  1. Two lousy antimatter-generating devices exist on one end of an experimental setup (e.g. with a 50/50 chance of creating an antimatter particle which is "stored" in the rest of the system via the beamline.)

  2. The two potential antimatter beamlines are converged into the annihilation region.

  3. The annihilation region is modified such that it has a preference for one of the two types of antimatter particles created.

  4. A detector exists in the generators described in step 1 capable of discerning whether the "output" was antimatter or just a bunch of artifacts from the collision which aren't antimatter.

  5. The generators and annihilation region are driven with the same period and proper phasing to ensure it's possible to make sense of the data.

It seems like if this is possible and the many worlds interpretation of quantum mechanics holds true that you could feasibly send messages back in time with modern technology relatively easily (at least, for a period of time equal to the effective beamline length.) It also seems like there would be some intrinsic property to energy which makes it a more "real" than either matter or antimatter if this holds true since it would appear to be the only thing really unaffected more than transiently by a temporally finite effect, but this already seems out there enough not to bother with that aspect without some degree of proof.

Is there some fault with this reasoning other than the assumptions that antimatter is backwards-travelling matter and that the many worlds interpretation would be true?

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    $\begingroup$ In your question you assume that matter travels forward while antimatter travels back in time. For example, an electron travels forward in time while a positron travels back. This however is not given. With the same logic you can assume that it is a positron that travels forward while an electron travels back. Then the rest of your question is moot. Furthermore, interpretations of quantum mechanics do not "hold" true or false. An interpretation is not a theory, but an explanation of the theory. There are many interpretations, but only one theory that holds true regardless of interpretation. $\endgroup$ – safesphere Nov 13 '18 at 21:06
  • $\begingroup$ @safesphere Yes, it makes the distinction of matter and antimatter irrelevant outside of determining if something is going forwards or backwards - from our perspective they would both appear to be moving forwards and be made of one or the other because we are made of matter and that's the direction we've determined to be "forwards." The point of this is more aimed at testing whether the MWI holds true, the theory as far as I can tell is the same regardless (though perhaps a bit more useful from an engineering perspective.) $\endgroup$ – CoryG Nov 13 '18 at 21:09
  • $\begingroup$ @safesphere That's basically what I was trying to convey with ` It also seems like there would be some intrinsic property to energy which makes it a more "real" than either matter or antimatter if this holds true...` I'm more concerned with the feasibility of this as an experiment to test MWI and time travel than whether to call a proton matter or antimatter (we already screwed that up once for electrical engineers by defining the electron as negatively charged, nomenclature is pretty well outside the realm of physics.) $\endgroup$ – CoryG Nov 13 '18 at 21:33
  • $\begingroup$ Yes, the intrinsic property of energy is that energy is always positive for both matter and antimatter. Everything else changes sign upon time reversal. This is why energy is the only thing required for a pair production. $\endgroup$ – safesphere Nov 13 '18 at 21:57
  • $\begingroup$ @safesphere I got that part, but it's still not quite what I had meant. Again, I'm more concerned about the feasibility of the experiment described to test MWI, the matter vs antimatter distinction is just what spurred the idea for the experiment. $\endgroup$ – CoryG Nov 13 '18 at 22:00

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