The physicists at CERN have discovered that the antimatter falls down. It seems to be an obvious thing, but scientists have not yet been able to confirm that it responds to gravity in same way as normal matter does. A new experiment provides the best answer so far.
Antimatter is very similar to the matter that makes up everything around us, with one important difference: its particles have opposite electric charge. And this simple difference has important implications: whenever a particle & its anti-particle meet, they annihilate each other.
Luckily for us matter-based beings, antimatter is extremely rare in universe, but no one really knows why. The Big Bang was supposed to produce equal amounts of matter & antimatter, which would have ended up wiping out all of the universe’s content billions of years ago. The fact that we are here today to ask the question shows that an unknown factor has created an imbalance.
Physicists are therefore studying antimatter closely to see if there are any other differences between it & normal matter besides the charge that could account imbalance. The Standard Model says there shouldn’t be any other differences, so if scientists find anything, it could open-up a whole new world of physics.
It means going back to basics to examine antimatter. For example, each element absorbs & emits different wavelengths of light, producing a unique finger print called an emission spectrum. Antimatter should have the same spectrum as its matter counterpart, but it wasn’t until 2016 that CERN scientists finally-checked. Indeed, anti-hydrogen turned out to have the same spectrum as hydrogen.
How antimatter reacts to gravity is another seemingly easy question that has taken years of study. It may sound like something we should already know, but most of the time, antimatter is suspended in electro magnetic traps to prevent it from annihilating them with containers. Its expected that antimatter should react to gravity the same way normal matter does, but there’s a small chance that it won’t & could fall upward instead.
To test the idea, the team placed antiprotons & negatively charged hydrogen ions into electromagnetic device called a Penning trap. Once inside, the particles follow a cyclical trajectory & by measuring their frequency, scientists can calculate their charge-to-mass ratio. This ratio should be the same for particles of matter & antimatter, but any difference would be attributed to variations in their interactions with gravity.
And of course, the team found that matter & antimatter react to gravity the same way. At least, in the uncertainty of the experiment, which is less than 97% of the gravitational acceleration experienced by particles. That’s 4 times more accurate than previous experiments, according to the team.
However, that still leaves room for new physics to squeeze in. Other experiments test the interactions of antimatter with gravity through what appears to be a much simpler approach: dropping particles of antimatter & seeing where they go. If these teams find results different from the current experiment, it could suggest physics beyond the Standard Model.
The research was published in the journal Nature.