Maggie's Farm

From the piece on time we posted yesterday, which I felt deserved an enticing quote:

In Rovelli's scheme, a clock's hands do not point upright because the universe says it is 12 o'clock; they point upright because of the location of the pendulum. Therefore the notion of time is meaningful only in a small range of physical situations in the universe, such as human experience. In most cases, however, time is meaningless. "In general, there is no time at all," Rovelli says.

Though this approach might seem radical, many researchers share Rovelli's sentiments. For example, Harvey Brown, an expert on scientific interpretations of reality from the University of Oxford, has argued that we "construct" time from the physical properties of the things around us.

Newton and Leibniz debated this very point. Newton portrayed space and time as existing independently, while Rovelli and Brown share Leibniz's view that time and space exist only as properties of things and the relationships between them.

It is still not clear who is right, says John Norton, a philosopher based at the University of Pittsburgh, Pennsylvania. Norton is hesitant to express it, but his instinct - and the consensus in physics - seems to be that space and time exist on their own. The trouble with this idea, though, is that it doesn't sit well with relativity, which describes space-time as a malleable fabric whose geometry can be changed by the gravity of stars, planets and matter. If the central property of space-time is the result of the existence of matter, how can we be sure that space and time exist on their own and are not convenient illusions? "Hence my hesitation," Norton says.

How can we be sure that time and space exist on their own and are not convenient illusions?