An experiment at CERN is asking members of the public to analyse particle tracks over the internet, in an attempt to help answer one of the weirder questions in modern physics: whether antimatter falls up. Although, for now, antigravity is confined to science fiction, antimatter is our best hope of finding an example in the real world. Difficult and expensive to study, physicists have yet to see how it responds to gravity. Some theories suggest antimatter will fall exactly like matter, and others indicate extra gravity -- like forces that would pull down on antimatter even harder, but antigravity is not ruled out.

Computer algorithms have been created that can, in principle, trace the tracks that particles leave behind, but the trouble is they were originally designed to study neutrinos, which produce totally different tracks, so the algorithms need adapting. The software asks you to watch short animations based on real particle annihilations and trace over any straight lines that could be particle paths. Physicists will then use the human-spotted tracks to update the algorithms' criteria for tracing out tracks. The idea is that humans will flag up tracks that the software misses, or rule out false positives.

It's a good test-bed to see whether we can get crowdsourcing to help us, says Michael Doser. We want to see whether humans are better than algorithms.