Out of the four fundamental forces, gravity is the one we are most familiar with. It keeps Earth spinning around the Sun, and it turns upon us every morning when we try to leave the bed. Gravity seems so familiar and yet is the most mysterious force of all.
Gravity is incredibly weak. Yes, it seems strong for us because Earth is huge, but even a tiny magnet can overcome gravity. The weakness of gravity is good news for us (planets and stars can form), but it doesn’t really fit well in particle physics. We have no way to explain why gravity should be so weak.
A new theory, N naturalness, has an interesting solution to explain weak gravity. Instead of having three families of particles (each with two quarks, one neutrino, and an electron-like particle), there are actually 10 quadrillion (1016) families.
"The idea is a little wild," co-author Tim Cohen, from the University of Oregon in Eugene, told New Scientist. "The absence of new physics at the LHC has motivated us to – instead of introducing a few new particles – introduce 1016 new particles."
This model requires a single kind of particle operating during the first instants of the Big Bang, called a reheaton. This particle would decay during the time of cosmic inflation, and since particles prefer to be in the lowest possible energy state, the resulting “allowed” particles are the known members of the Standard Model along a weak gravitational interaction.
The billions upon billions of never-before-seen particles might seem rather absurd, but it’s not the first theoretical physics idea that uses a large number of parameters to find a convenient solution. It’s unremarkable that constants and laws of the universe fall into a certain range, and when this principle appears to be violated (like a weak gravity perfect for us), it could indicate that there’s more science for us to explore in that direction.
The Standard Model does provide us with the best description of particle physics, but we know it’s limited, so physicists are looking beyond it both in theory and experiments. Some of the claims of N naturalness can be tested by current experiments, so we might soon see if this quirky idea has some truth behind it.
[H/T: New Scientist]
