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Berkeley Scientists Devise Experiment To Test Whether Antimatter "Falls" Up

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May 01, 2013 01:10 PM EDT
Antimatter Graphic
Do atoms of antihydrogen weigh the same as atoms of ordinary hydrogen? Could they even have 'negative' weight? Scientists from Berkeley Lab and UC Berkeley have used data from the ALPHA Experiment at CERN to measure antimatter gravity directly. (Photo : Illustration by Chukman So)

For years physicists have wondered if antimatter "falls" up. Then, on Tuesday, a group of physicists published the results of a study designed to measure just that in the journal Nature Communications.

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The answer, as it turns out, is still unclear. However, the researchers argue, the experiment was not without its successes.

By measuring where the antihydrogen particles started, then measuring where they ended up after a period of free-fall, the scientists found that antimatter may fall the same direction as regular matter.

However, those that worked on the project will be the first ones to admit the results were unclear.

The method used included the creation of antihydrogen atoms united by a single antiproton with single positrons (antielectrons).

Scientists have since found a way to freeze these antimatter particles in a strong magnetic trap that, when turned off, releases them and allows them to come into contact with regular matter. When this happens, the antimatter is annihilated in a flash of pure light.

However, the magnetic fields don’t turn of instantly: in all it takes almost 30-thousandths of a second before the fields decay to near zero. Meanwhile, flashes occur all over the trap walls and, according to researcher Jonathan Wurtele, very few of the anti-atoms escape after the field has been turned off for 20-thousandths of a second.

“Our results far from settle the question of antimatter gravity,” the group wrote in an ALPHA Experiment press release. “But they open the way towards higher-precision measurements in the future, using the same technique, but more, and colder trapped antihydrogen atoms, and a better understanding of the systematic effects in our apparatus.”

In other words, while the study may not have successfully measured the direction the antimatter particles “fell,” it did prove that measuring antimatter gravity is possible through the use of an experimental method that, the scientists said, “points toward much greater precision” in the future.

“Is there such a thing as antigravity? Based on free-fall tests so far, we can’t say yes or now,” researcher Joel Fajans said in a Lawrence Berkeley National Laboratory press release. “This is the first word, however, not the last.”

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