Antimatter is attracted by gravity in the same way as ordinary matter

 Groundbreaking experiments led by the Antihydrogen Laser Physics Apparatus (ALPHA) team at the European Center for Nuclear Research (CERN) based in Geneva have demonstrated that antihydrogen particles, the most basic known form of antimatter, don't levitate but are instead drawn downwards by gravity.

The world of antimatter, where antihydrogen is the simplest particle, is the mirror opposite of the matter universe. It consists of antiprotons, which are negatively charged protons, and positrons, the positively charged counterparts of electrons.

The widely accepted theory is that during the Big Bang, the event that birthed our universe, matter and antimatter were generated in equal proportions. The scarcity of observable antimatter has led some physicists to hypothesize a unique form of gravity that attracts antimatter to itself. However, the ALPHA group's experiments debunked this theory by showing that gravity impacts antimatter akin to matter.

How does antimatter respond to gravity? 

The most straightforward way to find the answer is to free the antimatter and observe its trajectory. However, gravity, being a feeble force of nature, doesn't significantly affect antimatter, especially in comparison to electric elements.

The ALPHA researchers theorized that due to its neutral charge, antihydrogen wouldn't be influenced by electric fields and would hence serve as the perfect candidate for gravity testing.

With the capacity to generate antihydrogen atoms, the ALPHA team initiated the construction of ALPHA-g in 2016, a platform designed to measure gravity's influence. Given that CERN's accelerators generate antimatter particles at near-light speeds, these particles needed to be decelerated first.

This was accomplished by guiding them along a loop, sapping their energy. Once their speed was reduced, they were directed into a massive magnet for trapping. Following the release of the magnetic field, the antihydrogen particles were set free, and specialized sensors were deployed to verify if they levitated or descended.

Inside the experiment

The magnet utilized in ALPHA-g, resembling a bottle and not exceeding 25 cm in length, could only house antihydrogen atoms with temperatures just above absolute zero (0.5 Kelvin, -458 Fahrenheit, -272 Celsius).

Despite these frigid temperatures, the antihydrogen atoms maintained average speeds of 100 meters per second and ricocheted off the magnetic fields within the magnet. The atoms remained confined within the bottle-shaped magnet due to the balanced magnetic fields at either end.

When positioned vertically, the atoms could either ascend due to levitation or descend due to gravity. Particles propelled by gravity could escape the magnetic field, striking the bottle container to produce a light flash upon interacting with matter. The magnetic field was eventually diminished to allow all the antimatter atoms to escape, with sensors recording their exit from either the top or bottom of the container.

Through experiments carried out in the summer and fall of the previous year, it was discovered that the gravitational acceleration of antimatter was 9.8 meters per second, consistent with the gravitational effect on matter within one standard deviation.

Moving ahead, the research team aims to enhance the precision of these measurements.

The research results were published in the journal Nature.