FROM ETERNITY TO HERE

A revealing look into the fourth and thorniest dimension.

Time, a famous scientist pointed out, is nature’s way of making sure everything doesn’t happen at once. Carroll (Theoretical Physics/Caltech) has read all the literary and scientific writing on the subject but has plenty of his own opinions. In his debut, the author writes in accessible prose, so readers who make the effort will absorb an avalanche of information. Everyone knows one needs three dimensions to locate anything, but without the time no one can find a specific event. As a result, educated readers accept time as a legitimate dimension, yet no one can shake the feeling that it’s odd. All laws of physics remain unchanged everywhere, and none assert that time can’t run backward, but it never does. Carroll’s explanation relies heavily on the second law of thermodynamics (to which he returns again and again), which states that all systems in the universe tend to become disorganized (increase in entropy). No law forbids an omelet from spontaneously turning back into an egg, but it’s extremely unlikely. Travel in time is simple provided one travels forward. Since relativity requires moving clocks to run slower than those at rest, one can speed up time by simply traveling and then returning. Sadly, travel into the past would produce paradoxes and, the author stresses, paradoxes don’t happen. Carroll delves deeper than the typical PBS science hour. Understanding time requires an acquaintance with entropy, relativity, cosmology, thermodynamics and statistical mechanics, which Carroll enthusiastically delivers at great length.

Not for the scientifically disinclined, but determined readers will come away with a rewarding grasp of a complex subject.