Antimatter Matter Repulsion

Johnleprekan

According to CPT Symmetry matter has reversed charge, spatial coordinates, and time. This includes gravity. So this means that antimatter would attract other antimatter and matter would attract other matter. The difference is when antimatter gets near matter. They repel each other.

First, can someone explain what CPT is in layman's terms? What does it mean to have spatial coordinates reversed? For time, it does not mean time is reversed but direction is. Can someone explain this one anyway?

If the cpt is reversed, why does antimatter repel matter? What is happening on a quantum level that causes it to repel?

The_Duck

No. Matter and antimatter attract each other via gravity. Gravity only cares about energy, and matter and antimatter both have positive energy.

CPT has three parts:

Slightly simplified, these are:
C - Charge conjugation. This is flipping positive and negative charges.
P - Parity. This is just reflection in a mirror.
T - Time reversal. This is just reversing the direction of motion of all particles.

CPT symmetry means that if you do all of these things at once--reflect the universe in a mirror, flip all positive charges with negative ones, and reverse the direction of motion of all particles--you get a universe that looks and acts exactly like the original one. The laws of physics will not notice if you perform C, P, and T all at once.

Johnleprekan

Thank you.

Astronuc

Matter and antimatter are attracted by charge difference, e.g., a positron is attracted to an electron, and both are annihilated.

Matter and antimatter have rest mass, and a mass (e.g., kg) of antimatter would behave the same in a gravity field as would the same quantity of mass of matter, i.e., gravity does not distinguish between matter and antimatter, as far as we know.

krash661

Maybe a interesting conversation if these two topics are combined ?

http://www.physicsforums.com/showthread.php?t=668079