European scientists are currently trying to collect enough antimatter to determine if the elusive substance reacts to gravity in the opposite way that normal matter does—by “falling up” instead of down.
Anti-gravity has long been a staple of science fiction as a future technological means for propelling spacecraft away from massive objects like planets and stars? But does it really exist in nature?
Scientists working on the Antihydrogen Laser Physics Apparatus (Alpha) experiment at CERN‘s Large Hadron Collider (LHC) in Switzerland aim to find out, according to reports. They theorize that antimatter, made up of antiparticles which possess an opposite electrical charge and quantum spin to normal particles, could also be repelled by ordinary matter instead of being attracted to it.
Writing in the latest issue of Nature Communications, the Alpha experiment scientists from the LHCb team note that “there are many indirect indications that no such differences exist” in how matter and antimatter interacts with gravity. But they also suggest that the new wealth of data the experiment has collected on antihydrogen particles is worth looking through to check if anti-gravity does exist, while proposing a way to do that.
“[T]here have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the Alpha antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5 percent; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime,” the researchers write.
The LHCb research team is now prying into other mysteries of antimatter such as the rates at which exotic particles decay into either matter or antimatter, according to BBC News. Scientists last week were able to determine “a slight difference in the decay of particles called Bs mesons,” BBC News reported.
But one big hurdle in this research is that producing antiparticles is difficult—and keeping them around for any length of time is even tougher.
The universe contains plenty of normal matter but just trace amounts of antimatter. When normal particles and antiparticles collide they destroy each other in a process called annihilation, creating high-energy photons, or in some experimental instances, new exotic particles.
But in recent years, researchers working on CERN’s Alpha experiment have been able to trap and maintain antihydrogen atoms for as long as 15 minutes. That’s given them much more time to study these antiparticles, BBC News noted. Now CERN scientists are looking through data collected from 434 antihydrogen atoms they’ve trapped in the past few years “with the anti-gravity question in mind.”
“In the course of all the experiments, we release [the antihydrogen atoms] and look for their annihilation. 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,” Jeffrey Hangst, a spokesperson for the Alpha experiment, told BBC News.
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