[Ushergomes (OP)]

Hello everyone,,
How does one differentiate between matter and antimatter ?? The Universe has more matter than anti matter but just barely ? How do we know that?? If the contrary were true what would happen?

[Halc]

How does one differentiate between matter and antimatter ??

They're the same, but opposite, and they annihilate if they interact.  You can tell if you have antimatter because of that annihilation.

The Universe has more matter than anti matter but just barely ?

There is none that we can see, except for trace amounts that escape and regular amounts that are continuously created in places like our sun.  The latter material is immediately annihilated as fast as it is created, but the former material has managed not to interact with anything.

How do we know that??

Good question.  I imagine we know it due to the lack of characteristic radiation that would be seen if there was region of matter adjacent to a region of antimatter.  If there are both, there has to be a boundary between them somewhere at some scale.
 

If the contrary were true what would happen?

Contrary to what?
If the universe was full of antimatter instead, then it would be called the matter and the minority material the antimatter.

[evan_au]

If the contrary were true what would happen?

If the universe were made of antimatter (rather than matter), we would not notice a difference on a day-to-day basis.
- Almost everything would work the same and look "normal": Chemistry, biology, physics, astronomy, geology, etc
- There are some extremely subtle differences that can be noticed at large particle accelerators would show that "normal" antimatter behaves slightly different than that rare and strange "matter". But it wouldn't be visible in everyday life.
See: https://en.wikipedia.org/wiki/CP_violation#Experimental_status

The Universe has more matter than anti matter but just barely ?

Yes. If the amount of matter and anti-matter were exactly equal, it would all have annihilated, and the universe would be dominated by photons (and Dark Matter).

However, a slight asymmetry allowed matter to dominate.
- At this point in time, we know of no mechanism that would produce even this small level of asymmetry
- The known mechanisms are just too subtle.
- But maybe other mechanisms exist that may be reachable with future, more powerful particle accelerators (eg the supersymmetry theory predicts heavier "partners" to the known particles, which may display greater asymmetry between matter and antimatter; these would have been very abundant in the first instants of the Big Bang)

For now, the cause remains a mystery.
See: https://en.wikipedia.org/wiki/Baryon_asymmetry

[pensador]

Am I correct in thinking the universe has a charge asymmetry ?

[Bored chemist]

"What is difference between matter and antimatter ?"
About a hundred trillion dollars per gram.
https://en.wikipedia.org/wiki/Antimatter#Cost

[evan_au]

Am I correct in thinking the universe has a charge asymmetry ?

It is thought that the number of electrons equals the number of protons to a very high accuracy, and that this charge balance has been present since very soon after the Big Bang.
- But no mechanism is known that would cause such a charge symmetry.

All experiments we conduct today show that electric charge is conserved.
- So the initial charge symmetry would still be present today.

[Hayseed]

"How does one differentiate between matter and antimatter ??"   I know of three common sense ways to check for anti-matter.  This is because of 3 inversions with anti-matter.

The inversions are mass(and angular momentum), electrical polarity, and dipole direction.  And the cause of all three inversions is the handedness of charge.

"The Universe has more matter than anti matter but just barely ? How do we know that??"

Anti-matter has always been just a trace of normal matter.  I don't see evidence of equal amounts at any time.   Although, there is a very good chance that anti-matter might be able to be made in a cheap manner.  It needs to be generated at time of use.  If so, we could have some extremely clean and efficient, and small, but powerful, power sources.

"If the contrary were true what would happen?"

It can't happen.  Unlike an equation, physical law is hard to naturally invert.  It needs a scarce condition to occur.  That condition is being able to accelerate the seed particle backwards.  And that is not as easy as it sounds.  When one reverses either field on a particle, the particle will turn around......we need to hit it before it turns.  That will invert the normal charge, into an inverted charge.......which is what anti-matter is.

If one could apply a high voltage electric field fast enough, we should be able to build a matter---anti-matter engine.  Like controllable small scale lightening chambers.  The only shielding needed would be for gamma.  And catching that gamma in that shield.........could be a DC or AC source.  With no by-products.  The future is bright for young fellas.  Not with fusion, but with anti-matter.

And of course, there are other anti-matter theories that one might consider.   But the quickness of a lightening strike does generate anti-matter.  I believe that anti-matter is not created, but just an inversion of normal matter.

This would explain, but also remove the mystery.   Only hardware will tell for sure.