Antigravity gets first test at Cern’s Alpha experiment
Researchers at Cern in Switzerland have proved the merits of a way to test antimatter as a source of the long-postulated “anti-gravity”. How antimatter responds to gravity remains a mystery; it may “fall up” rather than down. Now researchers reporting in Nature Communications have made strides toward finally resolving that notion.
Why the Universe we see today is made overwhelmingly of matter, with only tiny amounts of antimatter, has prompted a number of studies to try to find some difference between the two. One significant difference between the two may be the way they interact with gravity - antimatter may be repelled by matter, rather than attracted to it. But it is a difference that no one has been able to test - until the advent of Cern’s Alpha experiment.
Alpha is an acronym for Antihydrogen Laser Physics Apparatus - an experiment designed to build and trap antimatter “atoms”. In 2011 the Alpha team showed they could keep antihydrogen atoms trapped for 1,000 seconds. The team has now gone back to their existing data on 434 antihydrogen atoms, with the antigravity question in mind.
"In the course of all the experiments, we release (the antihydrogen atoms) and look for their annihilation," said Jeffrey Hangst, spokesperson for the experiment. "We’ve gone through those data to see if we can see any influence of gravity on the positions at which they annihilate - looking for atoms to fall for the short amount of time they exist before they hit the wall," he told BBC News.
The team has made a statistical study of which antihydrogen atoms went where - up or down - and they are able to put a first set of constraints on how the anti-atoms respond to gravity. The best limits they can suggest is that they are less than 110 times more susceptible to gravity than normal atoms, and less than 65 times that strength, but in the opposite direction: antigravity. In short, the question remains unanswered - so far.
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