About 100 trillion neutrinos are passing through your body at this very second. The particles are the second most abundant form of matter in the universe (behind light), but they interact very, very rarely. That property makes them ideal objects for studying the fundamentals of quantum mechanics; however, it also complicates measurements.

For example, neutrinos were discovered in the 1950s, but their properties are still obscure. New research, published in Nature by a team including Lawrence Livermore National Laboratory (LLNL) scientists, introduces an experimental technique to constrain the size of the neutrino’s wavepacket.

Imagine measuring a neutrino like finding a needle in a haystack. The particles are so elusive that, previously, researchers didn’t even know where on Earth the haystack was located. Now, they’ve identified the haystack, or, scientifically, the size of the neutrino’s “wavepacket.” This measurement doesn’t say exactly where the neutrino is located or how big it is, but it does constrain what those answers could be.