Experiments, Magnetism, News, Quantum mechanics, Subatomic particles

Effects of gravity on antimatter

An experiment on CERN confirmed that antimatter is attracted by gravity in the same way as common matter.

Source: LiveScience

On Sept. 27, an international team of physicists reported a major finding about an elusive form of matter known as antimatter. It appears that antimatter responds to gravity the same way regular matter does, validating theories proposed by Albert Einstein more than a century ago.

This result marks the first-ever direct observation of free-falling antimatter, in which atoms are made of antiprotons instead of protons and antielectrons (positrons) instead of electrons.

Matter and Antimatter Comparison
Antimatter particles have electric charges opposite of matter.

The new research ultimately proved that atomic antihydrogen — made up of one antiproton in the center with a positively charged positron orbiting around it — is pulled downward due to gravity instead of upward like you might expect with a form of matter that presents as the “opposite” of normal matter.

Furthermore, close to three decades after antihydrogen was first created in a lab, today’s scientific triumph is yet another confirmation of Einstein’s general theory of relativity, which predicts that all masses, irrespective of differences in their internal structures, react to gravity in a similar manner.

Capturing antimatter

Jonathan Wurtele, a physics professor at the University of California at Berkeley and his team, created, trapped and studied antihydrogen particles at The European Center for Nuclear Research (better known by its French acronym, CERN). The particles were trapped within what was essentially a magnetic bottle, both ends of which contained controllable magnetic fields. To witness the effects of gravity on the antihydrogen particles, researchers reduced the magnetic field strength at each end to let the particles escape.

I wrote two posts about my visit to CERN and I recommend that the readers also visit.

Visit to CERN (Part 1)Click here

Visit to CERN (Part 2)Click here

When each particle wandered to the top or bottom of the magnetic bottle, it zapped in a flash. Researchers then counted those flashes and found a higher number wandered to the bottom of the bottle compared to the top. A staggering 80% of them behaved in such a way, in fact, and this result held true for a dozen repeats of the experiment. According to the new study, that conclusively demonstrated that gravity causes the antihydrogen to fall downward.

The team also found that the gravitational acceleration of antihydrogen was close to that of normal matter, which is 9.8 meters (32 feet) per second squared. That result is expected to hold true for other antimatter particles too, researchers say.

However, though the latest findings rule out theories that posit antimatter is repelled by gravity, only more precise measurements will tell if there is any difference in the gravitational force on antimatter compared to matter.

Nonetheless, by achieving the first direct observation of gravitational effects on antihydrogen, researchers mark the beginning of detailed and direct pursuit of the gravitational nature of antimatter, which remains puzzlingly scarce in the universe.

It’s believed that soon after the Big Bang, there were equal quantities of matter and antimatter in the universe. However, if both are in contact with each other, both will be destroyed, liberating high energy. Nobody knows why there’s much more common matter in the universe.

About Pedro Ney Stroski

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