Protons have mass. Catholics have Mass. Religion helps define who you are and shapes your life. Show pride in your faith with this funny physics shirt fronted by a funny, punny message that says "Protons Have Mass? I Didn't Even Know They Were Catholic". Awesome for adults, men, women, kids, boys and girls. A great gift for christmas, a birthday, an anniversary, or any other present occasion. Get this present for the special physic guy in your life.