Friday, February 7, 2014

Of Space-Time and Clock Towers

by Len Hart

Brian Greene is an American theoretical physicist and string theorist. A professor at Columbia University since 1996, Greene has worked on mirror symmetry.

As a result, he believes that in “infinite” universes, the number of ways in which matter can arrange itself is infinite. Eventually, a “universe” is repeated. Such a parallel universe would look very much like the one we live in. Therefore, Greene says: if the universe is infinitely large, it is also home to infinite parallel universes.

As a string theorist, he believes that apparent conflicts between current cosmology (Relativity theory) and quantum mechanics is resolved with string theory –his 'specialty' for the past 25 years. Greene believes that the entire universe is explained with small strings vibrating in as many as 11 dimensions.

Moreover, within our single universe time is relative to where you are and how fast you are going at any given instant. Therefore, time is always local even within the single universe we live in. For example, time is slower for anyone who is moving. As Einstein demonstrated, time stops for anyone traveling at light speed.

Einstein imagined a street car leaving the clock tower in Bern. As long as his speed was less than that of light, the clock viewed from the street car would appear to be moving forward, marking the 'forward' progress of time. But –should the street car exceed the speed of light, the hands of the clock would appear to go backward as the street car –velocities faster than that of light –actually catches up with and passes light beams.

This effect can be simulated with an oscillator or an old 33 and a third RPM album turntable with a disc of concentric hash marks calibrated to appear stationary under florescent (pulsing) light. If the turntable is too slow, the hash marks will appear to rotate in one direction. If the rotation is too fast, the marks will appear to move in the opposite direction. At the desired turntable speed, the hashmarks will appear absolutely motionless. By the same token, time STOPS for one traveling at the speed of light.

The downside is that many other unfortunate things will happen to you at that speed. So –don't try this at home or without the supervision of experts. You are safe if you confine your experiments to an old 33 1/3 RPM turntable and some old Rolling Stone LPs.

A few years ago, Julian Barbour “shook up” readers of “Discover” magazine when he denied the existence of “time”. He may be correct. Interestingly, he is consistent with Einstein. Einstein posits that time is merely one's local' movement relative to the speed of light. Young Einstein lived in Bern (Switzerland) where he worked at the patent office. He often took the tram home in a direction away from the famous Bern clock tower. He imagined how the clock might appear should his tram exceed light speed. He immediately concluded that the hands on the clock tower would appear to move backward relative to the forward movement perceived by pedestrians on either side of the street. The explanation is simple: at faster than light travel, the tram overtakes that light that had previously left the tower. One looking back at the tower would see the hands run backward.

That, of course, is a dramatic example that drives home the point for anyone daring to imagine faster-than-light trams. The conclusion is simpler: time is different for every person occupying a different space from every other person. For that matter, time differs from every point to every other point in the universe.

Barbour believes the past, present and future all exist in what may be called a timeless 'super-verse'. Barbour posits a series of “NOWS” like individual frames on a motion picture film strip. 'Nows' exist for actual events but, interestingly, many 'nows' are alternate possibilities, i.e, virtual universes.

This view is consistent with Einstein's analogy re: the Bern clock tower. To use Barbour's film strip analogy, NOW is a single frame, the universe –the entire film strip. Parallel universes may be compared to alternate "film strips", thus Barbour's views are consistent with Greene's idea of "parallel" universes.

If Barbour's timeless universe is a film-strip, then Greene's parallel universes are a shelf full of film-strip canisters –each containing a feature-length film. In this case the feature-length movie is the universe as it unfolds.