'Antimatter falls down' are findings of new research, setting the scene to know more about nature of antimatter

New Delhi: Antimatter falls downwards, physicists report in a new study, adding that they have answered a long-standing question - does antimatter fall up or down? According to physics, it is thought that antimatter was created along with matter in equal amounts after the Big Bang, the cosmic explosion hypothesised to have marked the universe's origin.

While matter is made of particles, antimatter is said to be made of antiparticles, having the same mass as particles but opposite or complementary properties. However, despite knowing this, the properties of antimatter are still largely unknown.

Here, we show that antihydrogen atoms fall to Earth in the same way as regular matter, the physicists forming the ALPHA collaboration at the European Organization for Nuclear Research (CERN), Switzerland, report. Antihydrogen is the antimatter counterpart of hydrogen.

Their behaviour consistent with the Earth's gravitational attraction rules out the presence of repulsive 'antigravity', they said in their study published in the journal Nature.

The findings were a "milestone in the study of antimatter", they further said, adding that they are now closer to knowing more about the nature of antimatter.

The physical properties and laws governing antimatter have remained one of the greatest scientific mysteries, even as scientists don't yet have an explanation about where all the antimatter in the universe is.

It was June 2011 when scientists at the European Organization for Nuclear Research (CERN) had succeeded in trapping antimatter atoms for 1,000 seconds, or over 16 minutes: long enough to begin studying their properties in detail, according to CERN's statement dated June 5, 2011. The experiment at CERN's Antimatter Factory was published in the journal Nature Physics.

In the latest study, following a proof-of-principle experiment with the original 2013 ALPHA set-up, the team trapped groups of about 100 antihydrogen atoms, one group at a time, and then slowly released the atoms over a period of 20 seconds.

While a hydrogen atom is made up of an electron and a proton, an antihydrogen atom is made up of a positron (electron with positive charge) and an antiproton (negatively charged proton).

ALPHA spokesperson Jeffrey Hangst said, "It's taken us 30 years to learn how to make this anti-atom, hold on to it and control it well enough that we could actually drop it in a way that it would be sensitive to the force of gravity." The team created antihydrogen particles by taking antiprotons they produced, slowing them down and then binding them with positrons.

However, antimatter can interact with matter (present everywhere) and annihilate or destroy, thereby preventing the scientists from being able to study them.

Therefore, to prevent the lab-created antimatter from annihilating, they were confined in a magnetic trap, CERN scientists said in their statement. The annihilation resulting from matter interacting with antimatter is said to produce radiant energy in its wake, which is the energy that exists in the absence of matter.

Then, the environment inside the magnetic confinement was made as cold as possible, after which the antihydrogen particles were released within the setup, which was vertical, to witness and measure its gravitational behaviour.

"In physics, you don't really know something until you observe it. This is the first direct experiment to actually observe a gravitational effect on the motion of antimatter," said Hangst, who is an experimental particle physicist at Aarhus University, Denmark.

"We know there's a problem somewhere in quantum mechanics and gravity. We just don't know what it is. There has been a lot of speculation on what happens if you drop antimatter, though it's never been tested before now because it's so hard to produce and gravity is very weak," said Timothy Friesen, Physics and Astronomy, University of Calgary, Canada.

"Einstein's General Theory of Relativity describes how gravity works. Until now, we weren't entirely sure if this theory applied to antimatter. This experiment proves that it does and affirms one of the most celebrated scientific theories of all time," said William Bertsche, School of Physics and Astronomy, University of Manchester, UK, and a Deputy Spokesperson of ALPHA.

"The next step is to measure the (antimatter's) acceleration as precisely as we can. We want to test whether matter and antimatter do indeed fall in the same way," said Hangst.