Protons are found to be smaller in size Posted 13 July 2010 -
02:45 AM All atoms are made up of nuclei orbited by electrons.
The nuclei, in turn, are made of neutrons and protons, which are
themselves made of particles called quarks. For years the
accepted value for the radius of a proton has been 0.8768
femtometers, where a femtometer equals one quadrillionth of a
meter. The size of a proton is an essential value in equations
that make up the 60-year-old theory of quantum electrodynamics,
a cornerstone of the Standard Model of particle physics. The
Standard Model describes how all forces, except gravity, affect
subatomic particles. But the proton's current value is accurate
only by plus or minus one percent—which isn't accurate enough
for quantum electrodynamics, or QED, theory to work perfectly.
So physicists have been searching for ways to refine the number.
Smaller Proton Size Revealed by Lasers In a ten-year experiment,
a team led by Randolf Pohl of the Max-Planck Institute of
Quantum Optics in Garching,