Writing in Scientific American, metrologist Michael A. Lombardi explains the rather convoluted history of the 60-second minute, the 60-minute hour and the 24-hour day:
In today’s world, the most widely used numeral system is decimal (base 10), a system that probably originated because it made it easy for humans to count using their fingers. The civilizations that first divided the day into smaller parts, however, used different numeral systems, specifically duodecimal (base 12) and sexagesimal (base 60).
Thanks to documented evidence of the Egyptians’ use of sundials, most historians credit them with being the first civilization to divide the day into smaller parts. The first sundials were simply stakes placed in the ground that indicated time by the length and direction of the resulting shadow. As early as 1500 B.C., the Egyptians had developed a more advanced sundial. A T-shaped bar placed in the ground, this instrument was calibrated to divide the interval between sunrise and sunset into 12 parts. This division reflected Egypt’s use of the duodecimal system–the importance of the number 12 is typically attributed either to the fact that it equals the number of lunar cycles in a year or the number of finger joints on each hand (three in each of the four fingers, excluding the thumb), making it possible to count to 12 with the thumb. The next-generation sundial likely formed the first representation of what we now call the hour. Although the hours within a given day were approximately equal, their lengths varied during the year, with summer hours being much longer than winter hours.
Why is a Minute Divided into 60 Seconds, an Hour into 60 Minutes, Yet There Are Only 24 Hours in a Day? [Scientific American]
Very cool picture of the sky taken over a 24-hour period by Chris Kotsiopoulos of Greece. More information on exactly how he did it can be found here.
New research by physicists at the University of California, Berkley suggests that in order for the laws of physics to hold, the universe can not be finite in space or time. This means that time would have to stop at some point and they’ve calculated that this point has a 50% likelihood of occurrence within the next 3.7 billion years.
Look out into space and the signs are plain to see. The universe began in a Big Bang event some 13 billion years ago and has been expanding ever since. And the best evidence from the distance reaches of the cosmos is that this expansion is accelerating.
That has an important but unavoidable consequence: it means the universe will expand forever. And a universe that expands forever is infinite and eternal.
Today, a group of physicists rebel against this idea. They say an infinitely expanding universe cannot be so because the laws of physics do not work in an infinite cosmos. For these laws to make any sense, the universe must end, say Raphael Bousso at the University of California, Berkeley and few pals. And they have calculated when that is most likely to happen.
Their argument is deceptively simple and surprisingly powerful. Here’s how it goes. If the universe lasts forever, then any event that can happen, will happen, no matter how unlikely. In fact, this event will happen an infinite number of times.
This leads to a problem. When there are an infinite number of instances of every possible observation, it becomes impossible to determine the probabilities of any of these events occurring. And when that happens, the laws of physics simply don’t apply. They just break down. “This is known as the “measure problem” of eternal inflation,” say Bousso and buddies.
Of course, their model makes an important assumption about the laws of physics. They assume that we should be able to understand why they work instead of just being able to observe that they do work.
Time Likely to End Within Earth’s Lifespan, Say Physicists [MIT Tech Review]
During the volcano-induced airspace shutdown back in April a group of people, many of whom have never met and all of whom were stranded in various airports worked together to collaborate on a single-issue magazine:
What we’ve made of it all is an 88-page souvenir of a moment in time when a non-life-threatening crisis hit the world, one for which nobody was to blame, and nobody knew how long it would last. People scrambled to find alternative routes home, any way, any how, or tried to make the best of wherever fate had placed them. It was a moment of unplanned disruption, never to be repeated in quite the same way. The perfect subject for a magazine, in fact.
That magazine is now available for sale, and definitely looks worth the $18.95.
Stranded Takes Off [Magtastic Blogsplosion]
Really cool exposures from photographer William George Wadman showing the motion of dancers.
Motion [William George Wadman]
Lisa Simpson’s wedding from the sixth season episode “Lisa’s Wedding” (aired 19 March 1995) takes place today. Congratulations grown-up Lisa!
A.J. Jacobs (The Know-it-all, The Year of Living Biblically) has decided for his newest project to try to do only one thing at a time, i.e. unitask as opposed to multitask. It turns out to be pretty difficult for someone who normally checks his email while reading the newspaper, eating breakfast and talking to his wife, as Jacobs does. But he raises some really interesting points about how we spend our time. And the picture above? Explained:
Day four I’ve got to do something about my desk. This is where most of my crimes against focus occur. There are so many temptations. So many needs to fulfil. Snacks, cups of water, caffeine, curiosity about what Julie’s doing. I pop up from my desk once every five minutes.
I decide to engage in some light bondage. I once read about how Odysseus demanded his sailors tie him to the mast so he wouldn’t take a swan dive off the starboard side when he heard the alluring singing of the Sirens. So, in an homage, I’ve tied myself to the chair in front of my computer with a long extension cord. It feels safe, like a seat belt.
Five minutes ago, I thought of adjusting the lamp, since the bulb was spotlighting my face as if I was about to sing a solo. But then I’d have to unknot the cord and get up. I stay in the chair and return to my computer. It’s working!
My Colossal Task Burden [The Guardian]