Because it is composed of so few parts, it's the easiest antimatter atom to make. Antihydrogen's subatomic particles have an electronic charge opposite from those of regular hydrogen.
Hangst's team uses the latest technology to catch the antihydrogen atoms, hold them without letting them touch matter, and then drop them.
When the falling antimatter meets matter, the two "annihilate" each other, as scientists say, and give off energy in the process -- a kind of nano-explosion. The ALPHA scientists measure the energy bursts to find how fast the antihydrogen molecules fell after they dropped them.
So, did the antimatter fall up? Scientists with the ALPHA Experiment couldn't tell, according to study published in Nature Communications.
But the fact that they now have the technology to let it free-fall is a big deal, Hangst said. "That you can do this at all ... is a bit of a revolution."
It paves the way for scientists to get the answer in a relatively short time -- a few years instead of a few decades.
If scientists can figure out how antimatter interacts with gravity, it would take them a step closer to understanding how the universe was formed during the Big Bang, when a lot of antimatter was still around, Hangst says.
Many scientists believe that antimatter acts in the same or in a similar manner as matter when it comes to gravity. The ALPHA Collaboration puts that stance to the test.
"In a world in which physicists have only recently discovered that we cannot account for most of the matter and energy in the universe," the study says, it would be "presumptuous" to cling to the idea.
"We know that there is something fundamental about the universe that we don't understand," Hangst said.
In essence, scientists don't know why the universe exists at all.