(Phys.org)—A small team of researchers with the University of Hawaii, Ponta Grossa State University in Brazil and Stanford University has found what they believe is the reason that the surface of the sun rotates more slowly than its core. In their paper published in the journal Physical Review Letters, the team explains how they used a new technique to measure the speed of the sun’s rotation at different depths and what it revealed about the speed of the sun’s outer 70km deep skin.