Tuesday, March 21, 2006

Of dreams and reality

As Lewis Mumford put it: "If man had not encountered dragons and hippogriffs in dream, he might never have conceived of the atom."

According to Mumford, a historian and critic of Western culture, it was from the experience of dreams that humans came to believe that there is more to reality than meets the eye. Dreams gave sleepers access to an unseen world, veiled from our senses and daily experience, but as apparently real as the food we eat.

We no longer believe in the literal reality of dream images. But belief in an unseen world veiled from our senses is an important part of modern science. We believe, for instance, in atoms. Atoms are as real to us as were dragons and hippogriffs to our ancestors.

Sometimes the unseen realities of science seem no less bizarre than the creatures of dream. Is any dragon or hippogriff stranger than the solar neutrino?

As you sit at your computer reading this post, a flood of neutrinos from the sun is pouring through the roof of your house. Every second, hundreds of billions of these unseen subatomic particles pass through every square inch of your body! At night, equal numbers of solar neutrinos enter the Earth on the opposite side, zip virtually unhindered through the body of the planet (and your mattress) and pierce you in your sleep.

It is easier, I suppose, to believe in dragons. But neutrinos have been an indispensable part of physical theory since Wolfgang Pauli proposed their existence in 1931 to balance the books on energy in certain nuclear reactions. They have been produced and detected experimentally since 1956. These will-o'-the-wisps are securely established as a very real part of the unseen world of physics.

It takes some stretch of the imagination to think about neutrinos. It cannot hurt to have practiced on hippogriffs and dragons.