When asked once what time was, Albert Einstein replied that it was what clocks measure. In Idle Theory exactly the same notion of time is used. Time is what clocks measure.

However the way that people experience time is generally not one of a steady flow. Sometimes time goes by very slowly. Sometimes it hurries by quickly. Very often, with nothing to do, time seems to hang heavy. And, equally, immersed in some task, hours flit by like minutes. And people sometimes report that, during a train or car crash, the few seconds in which it takes place seem to expand into minutes. So even if time is actually proceeding at the same rate, it seems to speed up and slow down.

Idle Theory can perhaps offer something of an explanation of this experience. According to Idle Theory, people alternate between busy and idle states. When they are busy, they devote their attention to some task - chopping wood, solving equations -. When they are idle, they can do more or less anything.

And one thing that people can do in their idle time is to watch clocks. Watching a clock is seldom, perhaps even never, something that is done when people are busy at work. Indeed, "clockwatching" is one term used for being idle rather than working.

If someone is very busy, and 90% of their time is devoted to work, with only 10% idle, then assuming that this idle time alternates evenly with busy time, then every one idle minute is experienced every ten minutes.

And if someone else only 60% busy, and 40% idle, then a minute of idle time is experienced every three minutes or so.

Now if, during their idle time, both these people glance once at the same clock, then the busier of the two will find that the clock has advanced 10 minutes each time he looks at it. For him, the clock will advance at a rate of 10 minutes per glance.

However, since the more idle individual experiences idle moments more frequently than the busier individual, he is able to look at the clock more frequently. And so the more idle of the two will find that the the clock has advanced three minutes each time he looks at it. For him the clock will advance at a rate of 3 minutes per glance.

And so the experience each has of the clock is that for the busy individual time appears to pass more quickly than for the more idle person.

Therefore, if one extrapolates to the extremes of busyness and idleness, the more idle anyone becomes, the slower time seems to pass for them. And for a completely idle individual, time seems to stop. And, equally, the busier someone becomes, the faster time goes by, so that for a completely busy person, time goes by at infinite speed.

None of this requires mechanical clocks. Such clocks simply reproduce the natural clock of a planet Earth that rotates on its axis once every 24 hours, and orbits once a year around the sun. By day the sun traverses the sky, and shadows turn and shorten and lengthen. At night the stars rotate around the celestial pole, tracing circular paths like the hands of a mechanical clock. And the human body uses several biological clocks to regulate its processes.

The same argument may be used to explain how time sometimes seems to expand or dilate. And if car crashes and similar events seem to expand in duration, this might be explained by the fact that those who experience them are idle onlookers, who are watching a clock very attentively. For such people, from one glance at the watch to the next, the second hand hardly moves. Looking at a clock 20 times per second results in time seeming to pass 20 times slower than it is actually passing.

Thus time can seem to be passing both faster and slower than it is 'actually' passing.

Another oddity of this effect may be experienced during an ordinary working day, in which someone puts in 8 hours of work, and then enjoys 8 hours of leisure. If, while at work they are diligently busy, they will find that their work is over almost as soon as it has begun, the 8 hours passing in a twinkling. And if in their leisure they are diligently idle, they will find their idle time seems to expand. The result is that however busy or idle such a person actually is, as measured by clock time, their life will seem to them to mostly consist of leisure, as the apparent duration of their busy time contracts, and the apparent duration of their idle time expands. And conversely, if someone spends their working hours idly watching the clock, and their leisure hours in busy recreational activity - pastimes -, they will find that their working hours seem to expand, and their leisure hours seem to contract, and life seems to them to be all work.

Again, the effect of psychoactive drugs, such as marijuana or opium, is very often to expand time, make time seem to pass slowly. Since the physical effect of these drugs is very often to make their users torpidly inactive, this suggests that it makes them more idle. And this increased idleness would result in time appearing to slow. Conversely, drugs such as cocaine or amphetamines may act in the opposite sense, making someone more active, and speeding up time.