Researchers have proposed a new device that could help solve the mystery of whether antimatter falls up or down.
Antimatter refers to sub-atomic particles that have properties opposite normal sub-atomic particles.
Scientists have long wondered if antimatter falls down, responding the same way to gravity as ordinary matter.
The standard model of particle physics assumes this is the case, but experimental evidence remains hard to gather: measurements are complicated by the fact that antimatter is rare and annihilates when brought into contact with matter.
"We don't really understand antimatter," study author Holger Muller, a physicist at the University of California at Berkeley, told 'LiveScience'.
"For instance, the fundamental laws of physics suggest there should be equal amounts of matter and antimatter in the universe, but our observations tell us there is vastly more matter than antimatter in the universe, and there is no agreed-upon explanation for that," Muller said.
"The combination of antimatter and gravity has never been directly experimentally tested before.
"There are indirect observations others have obtained, but the very simple experiment of letting a chunk of antimatter drop and seeing what happens has never been done," Muller said.
Researchers have proposed a device, a light-pulse atom interferometer, that could measure the behaviour of any particle - atoms, electrons and protons, as well as their antimatter counterparts.
It works by studying cold particles - ones cooled to a degree above the coldest possible temperature, absolute zero.
At such cold temperatures, scientists can see particles behaving much like waves, rippling up and down within a chamber.
By analysing how these "matter waves" interfere with each other, the researchers can distinguish the force of gravity each particle is experiencing.
The device could be integrated into the ALPHA antihydrogen trap at CERN physics lab in Geneva, Switzerland, researchers suggest.
With current antihydrogen production rates, the scientists expect their system will reach an initial accuracy of better than 1 per cent for measuring how anti-hydrogen falls, and they could eventually improve this accuracy 10,000-fold.
The scientists detailed their findings in the journal Physical Review Letters.
