Does Antimatter Fall

Do you recall the tale of Galileo plunging objects from the top of the Leaning Tower of Pisa to determine whether gravity applied to all objects equally? And an astronaut later proved it was true by hammering a feather into the Moon's surface due to that annoying air resistance back on Earth?

Hundreds of years after Galileo's discovery, scientists attempted to determine whether antimatter falls similarly to regular matter in one of the world's most advanced science labs. Naturally, they dropped it to test it out.

Studying the universe's fundamental building blocks is the main goal of particle physics. Electrons, protons, and neutrons make up the majority of the subatomic particles that make up the universe that we are all familiar with. However, as it happens, there is an antimatter counterpart for every type of particle. Scientists typically indicate this by appending the prefix "anti-" to the name.

An antielectron is therefore an electron's antimatter counterpart. It also goes by the name "positron," emphasizing the primary distinction between matter and antimatter twins. Their electric charges are in opposition to each other. Hence, antielectrons have a positive charge of the same strength as electrons, whereas electrons are negatively charged. Apart from that, the two are exactly the same, having the same mass and size. Or at least, we believe they are the same. We still don't know a lot about antimatter because its detection is so challenging.

You see, in a flash of light, an antimatter particle and a particle of the same kind of matter annihilate one another. Thus, even though scientists can create a large amount of their own antimatter using sophisticated devices like particle accelerators—which they most definitely can—it doesn't usually last for very long. Eventually, it collides with errant particles of matter. However, as a result of advancements in technology, we are now able to produce antimatter particles in greater quantities at once as well as capture and hold them for extended periods of time.

This usually entails placing the antimatter in a magnetic field to suspend the antiparticles so they don't bounce against the solid walls and in a vacuum chamber so there are no stray air molecules for them to react with. Because antimatter is such a well-oiled machine, it has found some practical uses in the real world, such as identifying malignant tumors in medical scanners. However, there are a lot of unanswered questions about antimatter. One of the main ones is the reason for its extreme rarity in the universe—at least in comparison to ordinary matter.

Physicists are especially concerned about this because, according to their best theories, if the two are exactly the same except for their charge, then they should have been created in equal amounts during the Big Bang. Luckily for you and me, though, it appears that there was only the smallest of imbalances, causing most of the regular matter to be destroyed along with all that primordial antimatter. Some physicists believe that a force of nature may treat matter and antimatter differently, instead of assuming that there must have been different amounts of each at the beginning of reality.

For instance, even though antiparticles and regular particles are supposed to have the same mass, it's possible that gravity pulls on them differently. But if that example were real, it would contradict Einstein's well-known equivalency principle, which forms the basis of his General Relativity theory. In essence, the theory assumes that all mass, regardless of source, is subject to gravity in the same way. Thus, gravity should not behave any differently toward antimatter, according to experimental physicists. However, that doesn't mean that everyone should hang up their lab coats and live assuming all their life!

People, we really need to put our theories to the test. That is somewhat necessary for the entire "sciencing" process. And that brings us to the CERN particle physics lab's ALPHA-g experiment. The experiment is extremely complex. Powerful magnetic fields are used to trap and move the antimatter, which is created by subatomic particle collisions, as well as clever techniques to cool the batch to almost absolute zero. However, Alpha-g is also quite basic at its core. Antihydrogen atoms were merely placed in a box, and the researchers simply watched to see if they fell out.

Similar to an enhanced rendition of Galileo's fictitious Leaning Tower of Pisa experiment. It should be noted that antihydrogen is the antimatter form of ordinary hydrogen, which is the lightest and most prevalent atom in the universe. One positively charged proton and one negatively charged electron make up regular hydrogen. It is therefore approximately electrically neutral. The same concept applies to antihydrogen, but in reverse, with a negatively charged antiproton bound to a positively charged antielectron. You may be asking yourself why, rather than depending on a fleet of lone antielectrons or antiprotons, scientists went to all that extra trouble to create antimatter atoms.

Since the electric force is far, far stronger than the gravitational force, they kind of had to. A neutrally charged atom won't be impacted by any stray electric and magnetic fields in the lab nearly as much as an individual positive or negative particle, allowing the experiment to focus entirely on the effect of gravity. Approximately eighty percent of the antihydrogen atoms that the experimenters dropped into their elaborate science box fell out shortly after they were dropped, according to their findings.

This may seem strange at first, but even in ordinary matter, the force created when atoms collide can be greater than the pull of gravity because of their small size. Thus, some of the 100 atoms in a cloud, whether regular or antimatter, will be propelled upwards only by collisions and will fall too slowly for the experiment to detect. Their team's simulations ended up matching that 80 percent falling figure. Subsequent investigation revealed that the antihydrogen descended at a pace that was nearly equivalent to that of regular hydrogen.

However, there is still a significant margin of error in these preliminary results, which were released in September 2023. They do not, in theory, rule out the possibility that gravity is between twenty and fifty percent weaker for antihydrogen. If more sensitive follow-up experiments go in that direction, it would be completely devastating. However, Alpha-g has eliminated the possibility that antimatter is somehow flipped for antihydrogen and has most likely ruled out the theory that it reacts to gravity in any way at all. The antimatter collapses. Hence, even though these findings may not lead to any novel or surprising discoveries in physics, it is comforting to know that gravity still applies to matter and antimatter interactions. It would make Galileo proud.