Showing posts with label time. Show all posts
Showing posts with label time. Show all posts

Friday, February 28, 2014

The Hourglass

Detail, Allegory of Good Government
Ambrogio Lorenzetti, 1338
The hourglass has become a symbol of medieval technology, one of our first attempts to quantify and measure time. We know it existed in the 14th century, from a 1338 fresco by Ambrogio Lorenzetti (c.1290 - 1348) in which the allegorical figure of Temperance holds one (Temperance, after all, is about taking a "measured" response to something, rather than uncontrolled actions). In 1345, an English merchant's receipts show that he paid for "twelve glass horologes" in Flanders, establishing that they were probably already prevalent and in demand.

Sailors found the sand-filled hourglass a definite improvement over its predecessor, the clepsydra* (the water clock), which was affected too much by the swaying of the ocean. When Magellan (c.1480 - 1521) circumnavigated the globe, his fleet had 18 hourglasses per ship, with a page dedicated to turning each one to keep accurate time.

They were also preferable in the early Middle Ages to clocks, because they did not rely on complicated and delicate machinery that needed frequent maintenance.

Where and when was the hourglass invented? A story that it was invented in the 800s by a monk at Chartres named Liutprand has no evidence to support it. The clue to the origin may be in the construction. The earliest hourglasses used marble dust for the sand. Also, the hourglass required expertise in glass-blowing. The likeliest location for these two features of the hourglass to be brought together is Italy, particularly Venice, where glass-blowing was a highly developed art and marble was readily available.

By the end of the 14th century, hourglasses were so common that the Goodman of Paris, writing a guidebook for his young wife in the 1390s, included a recipe for preparing the sand/dust for an hourglass:
Take the grease which comes from the sawdust of marble when those great tombs of black marble be sawn, then boil it well in wine like a piece of meat and skim it, and then set it out to dry in the sun; and boil, skim and dry nine times; and thus it will be good.
Not only must the hourglass have become common, but its construction was clearly something that could be contributed to by a regular household.

*clepsydra is from the Greek and means "water thief"; they could be very elaborate, but were naturally susceptible to humidity and temperature.

Thursday, July 12, 2012

What is Time?

What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not: yet I say boldly that I know, that if nothing passed away, time past were not; and if nothing were coming, a time to come were not; and if nothing were, time present were not. Those two times then, past and to come, how are they, seeing the past now is not, and that to come is not yet? But the present, should it always be present, and never pass into time past, verily it should not be time, but eternity.
With this passage, found halfway through Book XI of his Confessions, St. Augustine of Hippo (13 November 354-28 August 430) discussed the difference between Time and Eternity. He knows that he is not aware of time that is yet to come, or time that is past; only time that is present; but he still doesn't know how to define what time is.

A medieval 24-hour clock.
Measurement of time was imprecise. There were "hours" of the day: the Vigil took place between 2:30 and 3:00 a.m., Matins came at Dawn, et cetera. These hours designated times of worship and work for monks and were extended to general use, but they were not exactly a way to quantify time. The hour of Sext was at noon, for instance, which was recognized when the sun was highest, but Matins/Dawn came more or fewer hours before Sext, depending on the time of year. They were segments of the day that altered with the seasons; they did not measure a span of time.

St. Benedict of Nursia (c.480-543), in his Rule for monks, intends them to worship at specific times, and finds a way to measure a span of time. Monks were not to slack at getting up for Matins, and so:
If anyone shall come to matins after the Gloria of the 94th Psalm, which on this account we wish to be said slowly and leisurely, he shall not take his place in the choir, but go last of all, or to some place apart which the abbot may appoint for those who so fail in his sight.
Time could be measured, therefore, by comparison to a known duration.* But even durations could be tricky. Augustine had pondered thinking of a long syllable as equivalent to two short ones, "But when two syllables sound one after the other—the first short, the second long—how shall I keep hold of the short one?" Augustine seemed to be caught up in the idea that time was a continuum, and that he was living in a constant present and could not treat the past and future in the same conceptual way, since he could not live in them. The Middle Ages couldn't grab time and measure it, like water or distance or even acceleration. It was insubstantial, and belonged to God.

The concept of time had to change ... and eventually it did. There was no clear turning point; there had to be some conceptual change, planned or otherwise, to see time not as a line but as a series of points, as separate moments that could be thought of without being linked to a past or future moment.

Sometime in the mid-13th century, we find Franco of Cologne. He was a music theorist who gave us the idea that a mark on a page should distinguish how long a note should be. This was the logical extension of Franco's definition of time: "Time is the measure of actual sound as well as of the opposite, its omission."

Was this the moment? Was it music, with its attention to and reverence for mathematics that accidentally inspired the thinking of time as separate units that could be measured and counted? We might be able to believe that, if there were some evidence that the world began to measure and quantify time; for instance, if the development of mechanical clocks were to start around this time.

Well, guess what happened next?

*This method of measuring spans of time without a clock is used even today.