Antimatter is a type of matter that is composed of antiparticles, which have the same mass as regular particles but with opposite electric charge. For example, an antiproton has the same mass as a proton but a negative charge. When matter and antimatter particles come into contact, they annihilate each other and release a large amount of energy. This is different from regular matter, which is composed of particles with the same electric charge.
Theoretically, an antimatter universe could exist, but it is currently unknown if one actually does. The laws of physics allow for the creation of equal amounts of matter and antimatter in the early universe, but for some reason, there is much more matter than antimatter in our observable universe. Scientists are still studying this imbalance and trying to understand why it exists.
There are a few ways that a matter and antimatter universe could differ, but they are purely speculative at this point. For example, if there were an antimatter universe, it would emit photons with opposite circular polarization compared to our universe. Additionally, there could be differences in the behavior of gravity and other fundamental forces in an antimatter universe.
Scientists can create small amounts of antimatter in laboratory settings, such as in particle accelerators. They can also study the properties of antimatter particles by observing their behavior in high-energy collisions. However, it is difficult to study antimatter on a large scale since it reacts with regular matter and annihilates quickly.
Antimatter has been used in some medical imaging techniques, such as positron emission tomography (PET) scans. It has also been proposed as a potential fuel source for space travel, but currently, it is not used in any major practical applications due to its high cost and difficult production process.