Showing revision 1"Neutrinos were later proven to exist, which was difficult considering
they have negligible [rest mass]? (which means that their [gravitational interaction]] is very small), travel very
close to the [speed of light]?, and have no charge (this means that they do interact with ordinary matter though
electromagnetic interaction either). They also don't interact through [strong nuclear interaction]?, but only
through [weak nuclear interaction]?."