A worth reading essay by Noble Prize winner physicist.
Imagine a planet encrusted with ice, beneath which a vast ocean lies. (Imagine Europa.)
Within that ocean a species of brilliant fish evolved. Those fish were so intelligent that they took up physics, and formulated the laws that govern motion. At first they derived quite complicated laws, because the motion of bodies within water is complicated.
One day, however, a genius among fish, call her Fish Newton, had a startling new idea. She proposed fundamental laws of motion––Newton’s laws––that are simpler and more beautiful than the laws the fish had derived directly from experience. She demonstrated mathematically that you could reproduce the observed motions from the new, simpler laws, if you assume that there is a space-filling medium that complicates things. She called it Ocean.
Of course our fish had been immersed in Ocean for eons, but without knowing it. Since it was ever-present, they took it for granted. They regarded it as an aspect of space itself––as mere emptiness. But Fish Newton invited them to consider that they might be immersed in a material medium.
Thus inspired, fish scientists set out to find the atoms of Fish Newton’s hypothetical medium. And soon they did!
That story is our own. We humans, like those fish, have been living within a material medium for millennia, without being consciously aware of it.
The first inkling of its existence came in the 1960s. By that time physicists had devised especially beautiful equations for describing elementary particles with zero mass. Nature likes those equations, too. The photons responsible for electromagnetism, the gravitons responsible for gravity, and the color gluons responsible for the strong force are all zero mass particles. Electromagnetism, gravity, and the strong force are three of the four fundamental interactions known to physics. The other is the weak force.
A problem arose, however, for the W and Z bosons, which are responsible for the weak force. Though they have many properties in common with photons and color gluons, W and Z bosons have non-zero mass. So it appeared that one could not use the beautiful equations for zero mass particles to describe them. The situation grew desperate: The equations for particles with the properties of W and Z, when forced to accommodate non-zero mass, led to mathematical inconsistencies. Click link for full article;