Time is an illusion

Here is just part of a good article by Amanda Gefter for New Scientist magazine. (Jan. 19,2008)

"IT IS the invisible presence that governs your world. Trailing you like an unshakeable shadow, it ticks and tocks incessantly - you can sense it in your heartbeat, in the rising and setting of the sun, and in your daily rush to make meetings, trains and deadlines. It brings order to our lives through the categories of past, present and future.
Time. There is nothing with which we are so familiar, and yet when you try to pin it down you find only a relentless torrent of questions. Why does time appear to flow? What makes it different from space? What exactly is it? It's enough to make your neurons misfire, then sizzle and smoke.
You are not alone. Physicists have long struggled to understand what time really is. In fact, they are not even sure it exists at all. In their quest for deeper theories of the universe, some researchers increasingly suspect that time is not a fundamental feature of nature, but rather an artefact of our perception. One group has recently found a way to do quantum physics without invoking time, which could help pave a path to a time-free "theory of everything". If correct, the approach suggests that time really is an illusion, and that we may need to rethink how the universe at large works.
For decades, physicists have been searching for a quantum theory of gravity to reconcile Einstein's general relativity, which describes gravity at the largest scales, with quantum mechanics, which describes the behaviour of particles at the tiniest scales. One reason it has been so difficult to merge the two is that they are built on incompatible views of time. "I am more and more convinced that the problem of time is key both to quantum gravity and to issues in cosmology," says Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada.
According to general relativity, time is stitched together with space to form four-dimensional space-time. The passage of time is not absolute - no cosmic clock ticks away the hours of the universe. Instead, time differs from one frame of reference to the next, and what one observer experiences as time, another might experience as a mixture of time and space. For Einstein, time is a useful measure of things, but nothing special.
Not so in quantum mechanics. Here time plays a key role, keeping track of the ever-changing probabilities that define the microworld, which are encoded in the "wave function" of a quantum system. The clock by which the wave function evolves records not just the time in one particular frame of reference, but the absolute time that Einstein worked so hard to topple. So while relativity treats space and time as a whole, quantum mechanics splits the universe into two parts: the quantum system being observed and the classical world outside. In this fractured universe, a clock always remains outside the quantum system (see Diagram).
Something has to give. The fact that the universe has no outside, by definition, suggests that quantum mechanics will be the one to surrender - and to many, this suggests that time is not fundamental. In the 1990s, for instance, physicist Julian Barbour proposed that time must not exist in a quantum theory of the universe. All the same, physicists are loath to throw out quantum theory, as it has proven capable of extraordinarily accurate predictions. What they need is a way to do quantum mechanics in the absence of time."