A basic accounting rule in physics says whenever a particle collision creates a baryon—something like a proton or neutron that consists of three particles called quarks—it must simultaneously create a similar antibaryon. Such “baryon number conservation” implies the amount of nuclear matter in the universe is fixed. However, physicists have never determined where within a baryon the conserved number resides. For decades, the textbook answer has been simple. Each quark carries a baryon number of 1/3 and each antiquark carries a baryon number of –1/3. Because a collision can only ever make quark-antiquark pairs, the total baryon number cannot change. However, a recently published study suggests the baryon number is not carried by the quarks, but instead resides in an agglomeration of particles called gluons that bind the quarks together and is called a baryon junction. Learn more: @NewsfromScience