Stumped by This Crossword Clue? Opposite Stuff Revealed!

– Opposite of matter
– In physics, it’s made up of particles with opposite charge to normal matter
– It annihilates when it comes into contact with matter
– Used in science fiction as a power source
– Its existence was theorized by Paul Dirac in 1928
– Research is being conducted to find practical applications for it
– Poses a challenge to study due to difficulty in producing and containing it
– Utilized in medical imaging techniques such as PET scans
– Plays a role in the formation of the universe according to the Big Bang theory
– Has the ability to exhibit strange properties such as negative mass