Will Antimatter Obey Gravity’s Pull?

by Elizabeth Howell on May 1, 2013

What matter and antimatter might look like annihilating one another. Credit: NASA/CXC/M. Weiss

What matter and antimatter might look like annihilating one another. Credit: NASA/CXC/M. Weiss

What goes up must always come down, right? Well, the European Laboratory for Particle Physics (CERN) wants to test if that principle applies to antimatter.

Antimatter, most simply speaking, is a mirror image of matter. The concept behind it is that the particles that make up matter have an opposite counterpart, antiparticles. For example, if you consider that electrons are negatively charged, an antielectron would be positively charged.

This sounds like science fiction, but as NASA says, it is “real stuff.” In past experiments, CERN’s particle accelerator has created antiprotons, positrons and even antihydrogen. Properly harnessed, antimatter could be used for applications ranging from rocketry to medicine, NASA added. But we’ll need to figure out its nature first.

The experiment CERN described snares antihydrogen atoms in a powerful magnetic field (inside a container) for several minutes. As the researchers let these atoms go, they can watch on which walls the atoms crash into. The experiment is called ALPHA, for Antihydrogen Laser Physics Apparatus.

While researchers weren’t originally looking to learn more about gravity, the team working on the experiments came to realize their data “might be sensitive to gravitational effects,” CERN stated.

To be sure, these atoms would have a bit of energy when they are released, so one wouldn’t expect them to hit the ground right away. But what the scientists are doing now are figuring out, with reference to how the antihydrogen atoms moved, what the limit might be on “anomalous gravitational effects.”

The scientists have made new use of the ALPHA data they collected in 2010 and 2011 for other purposes, and now plan to do more experiments in 2014 with gravity specifically in mind.

So far, they’ve been able to begin constraining the gravitational to inertial mass ratio (the particle’s reaction to gravity), but it will take further work to learn more about how gravity affects these particles more generally.

“Based on our data, we can exclude the possibility that the gravitiational mass of antihydrogen is more than 110 times its inertial mass, or that it falls upwards with a gravitational mass more than 65 times its inertial mass,” CERN said on its website.

Already, though, the scientists are starting to talk about what could happen if antimatter behaves differently than matter in the face of gravity.

If antimatter fell up, stated Joel Fajans, an ALPHA physicist at the University of California, Berkeley, this could mean that gravity does not universally affect all types of particles.

“In the unlikely event that antimatter falls upwards, we would have to revise our view of the way the universe works,” he said. “We’ve taken the first steps toward a direct experimental test of questions that physicists and non-physicists have been wondering about for more than 50 years.”

Source: CERN


Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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