Yesterday NASA announced that last month's LCROSS probe collision with the Moon generated a debris cloud filled with tiny particles of ice. You may remember the LCROSS experiment as NASA's attempt to "bomb the Moon" (no, blogger Frank J. was not involved) that was visually disappointing, yet apparently rich in scientific data, once the results were compiled and analyzed.
After studying the debris blasted loose by the collision, NASA announced that about 80 liters of water was present in the dust cloud. The impact occurred inside a crater where the surface has been shielded from sunlight for approximately 2 billion years. The origin of the water is unknown, but NASA scientists are speculating that it might have been deposited during numerous collisions with comets during the Moon's lifetime.
NASA originally announced that the impact would create a massive 6 km high dust plume that would be visible from large earth-based telescopes. When such a cloud failed to materialize, scoffers dismissed the collision as a failure. NASA scientists now believe that the significant amount of ice present in the crater probably dampened the degree to which debris was dislodged by the collision.
The discovery of water on the moon establishes a number of important possibilities once thought to be exceedingly remote, particularly the fact that water could be much more widespread throughout the solar system (or the galaxy for that matter) than previously understood.
And a few weeks ago (I bookmarked this but never got around to writing about it) a group of English scientists announced the discovery of molecular structures known as "spin ice" that function as magnetic monopoles , that is, crystals with only "north" or "south" magnetic orientation. Incredibly, these scientists apparently succeeded not only in observing the phenomenon, but also in inducing magnetic monopole fields and currents in the spin ice material.
In 1931, physicist Paul Dirac, considered today to be the father of modern quantum theory, speculated that if light and electric charge both exist on the subatomic level as discrete "particles" or tiny localized packets of energy (as photons and electrons, respectively) then magnetic fields must also exist in a discrete quantum state. Magnetic monopoles have been briefly detected as transient quantum states in certain kinds of highly magnetized solids, but none had ever been observed in nature. This was to be expected, since the idea of a naturally occurring magnetic monopole contradicted the fundamental, well-known laws of electricity and magnetism.
Ever since the mid-nineteenth century, physicists had understood that electricity and magnetism were inextricably linked together, and were believed to simply be different manifestations of the same phenomenon. In 1864 British physicist James Clerk Maxwell demonstrated this mathematically. Maxwell's four equations describing the link between electricity and magnetism were one of the great triumphs of nineteenth century science, and represented the first successful attempt to mathematically unify two different natural phenomena.
One of Maxwell's equations, known alternatively as Gauss's Law for Magnetism is simply:
which in plain English says that the divergence of the magnetic field is zero; in other words, magnetic fields do not radiate outward in straight lines -- they must always curve back toward each other. This directly implies that there can be no magnetic monopoles, because the flux of magnetic fields must curve back upon itself, which in turn means that magnets must have north and south poles.
A discovery that challenges the accuracy of Maxwell's equations is similar in its implications to the discovery of theories that challenged Newton's laws of gravitation. Of course that is exactly what happened when quantum theory was discovered a century ago, and when Einstein opened up the world of space-time physics with the development of special and general relativity. In those cases, Newton's original laws of gravitation were found to be accurate, but were actually special cases of general gravitation when conditions were simplified. The same thing will probably happen in the case of magnetic monopoles -- a new quantum-level theory will be developed (or perhaps an existing one verified) and Maxwell's equations will be a special case, under simplified conditions.
To a physics graduate and life-long geek, this is pretty exciting stuff!
Thanks for indulging me this morning ... you may resume your regular lives now.