All Kinds of Time

The history of clocks and calendars is that of a constant struggle to measure time with more precision. Time and time again (so to speak), we arrive at a more accurate way to measure time, one more exact than the previous way. And over time (again please excuse the recursion) that time measurement system eventually shows some fatal weakness, exposed by either greater cultural or scientific demands of precision, or because of some inherent flaw that can no longer be ignored.

Flies with a mutant gene that disrupts their circadian rhythms do not live as long as flies that have no such mutation, researchers from Oregon Stare University have found.

Throwing off a fly's circadian rhythm brings about "accelerated neurodegeneration, loss of motor function and premature death," according to the research published last week.

The history of time-keeping is one of striving to achieve ever-more precise increments of time. We started measuring time in quarterly seasons, and now we measure it billionths of a second. Sometimes improvements in time-keeping drives human advancement; sometimes human advancement drives improvements in time-keeping. The two dance together perhaps in the same way that electricity and magnetism do in order to form light.

The Network Time Protocol (NTP) is used to update a computer's clock time from a time server over the Internet.

Synchronization is done through an exchange of packets between a NTP time server and the computer, known here as the client. The client sends a request packet to the server, which includes the time the packet was sent (called the "originate timestamp"). When the server receives the packet, it sends back another packet with the time it received that packet (the "receive timestamp").

At first glance, computerized timekeeping might seem like a cinch. A computer sees time as one thing: A uniform accumulation of discrete moments. The more accurately such moments are captured, the more precise the resulting time.

In almost each cell of the human body is a tiny molecular clock, made up by a set of protein gears. These gears play a role in almost every biological function, such as cuing body hunger and sleepiness, and even affecting cellular division and the aging process overall.

Traditionally, it was thought the body had a master clock to synchronize time with all the cell clocks, called a suprachiasmatic nucleus (SCN), which has about 20,000 neurons, and resides in the brain.

The word "time" actually refers to two different abstract concepts. One is the length or duration of some event, such as "That movie was over three hours long." The other is the period in time, as in "That movie opened Friday." The date is a point within a larger set of cycles; The period is a select number of cycles.

Time keeping, then, is a matter of keeping track of the number of cycles that have passed. The date and the period both use a cyclic interval of some sort: a month, a hour, a minute, a second.

Given that time can not be measured directly, one might suspect that it doesn't exist at all. An anti-time argument could almost work, too, except for the fact that this elusive entity provides a foundation for at least one basic law of physics, namely the second law of thermodynamics.

You may know the four laws of thermodynamics, the guide to how energy gets shuffled around this universe. These laws have been well-known for more than a century and rely pretty much entirely on Newtonian mechanics. The exception is the second law.

The upcoming month of June may seem a slightly longer than usual. Last week, the International Earth Rotation and Reference Systems Service has added a leap second at midnight, June 30.

That additional second will be placed between 11:59:59 p.m. June 30 2012 and 12:00:00 a.m. July 1, 2012. For computer systems, it will take the form of 11:59:60.