Scientists at CERN plan to take some antiprotons out for a spin in a never-tried-before test drive. Over about four hours, teams will gingerly wheel out about 100 antiprotons suspended in a “cloud” that’s encased in a vacuum inside a box and held in place by supercooled magnets for the ride in a truck at its Geneva campus. Each particle has corresponding antiparticle, like an antiproton, exactly matching the particle but oppositely charged. If the opposites come into contact, they “annihilate” each other and set off energy. The mass in the test is tiny, so the worst that can happen is losing the antiprotons.