Flying high: AMS-02 is being tested in a thermal vacuum chamber at a European Space Agency laboratory in Holland. The chamber simulates the conditions of space.

The spectrometer will look at the nature of what makes up almost 25 percent of the universe–dark matter, whose existence is inferred from its gravitational effects on visible objects. “AMS may be the first way that we understand the nature of dark matter because there is not another detector at this scale with this amount of precision,” says Steve Nahn, an associate professor of physics at MIT.

The new spectrometer will also search for clues about the dawn of the universe by hunting for antimatter, the mysterious twin of matter. (Think of protons and electrons having twin particles with equal amounts of mass but opposite electrical charges. It’s known that such “antiparticles” exist, and they can be made in particle colliders on Earth, but understanding how much antimatter exists in the universe now would be crucial to understanding the Big Bang.) Lastly, the spectrometer will study the composition and distribution of cosmic rays more accurately than has been done before, says Martin. When AMS-02 is in space, it can measure light rays that would otherwise be absorbed in the atmosphere.

The only detector with more power than AMS-02 is the Large Hadron Collider (LHC), a particle accelerator based at the European Organization for Nuclear Research (CERN). It’s being used for the largest physics experiment ever. Both the Hadron Collider and AMS-02 were built at CERN, but AMS-02 will look at dark matter from the sky in a way that the LHC cannot, and discover things about the composition of our universe in ways that can’t be reproduced in the lab, says Battiston.

“One hundred years ago people did not understand electrons, so they started to do experiments, and now we have cell phones, computers, and millions of transistors,” Nahn says. “So is it worth it to figure out what the universe is made of? Absolutely.”