<human>:  Why is it called the ‘Up quark’?
<bot>: The Up quark is named after the direction it is traveling. In particle physics, the up quark is the third of the six quarks that make up protons and neutrons. It is the only quark that carries a positive charge. The Up quark is also the heaviest of the three light quarks, and it is the only quark that has a spin of 1/2.