For decades scientists have tried to find a way to measure the mass of the lightest matter particle known to exist. Three new approaches now have a chance to succeed.
If you were asked to weigh something—your dog for example—how would you do it? You could set the dog in your car, watch the compression, measure how many inches the car is displaced, then convert that into a measurement of the dog’s mass. You’d need to know the weight of the car, the technical specifications of the shocks, how much air is in the tires, and something about spring constants. That’s an indirect (and hard) way. Alternatively, you could simply set the dog on a bathroom scale. The decision on which approach to use, direct versus indirect, depends on what resources you have available. If you don’t have a bathroom scale, an indirect measurement using your car could hypothetically be your best option. When it comes to neutrinos, scientists have faced a similar situation.