Why 60 seconds and minutes but 24 hours?  JUL 22 2011

Why are there 60 seconds in a minute and 60 minutes in an hour but 24 hours in a day?

Thanks to the ancient civilizations that defined and preserved the divisions of time, modern society still conceives of a day of 24 hours, an hour of 60 minutes and a minute of 60 seconds. Advances in the science of timekeeping, however, have changed how these units are defined. Seconds were once derived by dividing astronomical events into smaller parts, with the International System of Units (SI) at one time defining the second as a fraction of the mean solar day and later relating it to the tropical year. This changed in 1967, when the second was redefined as the duration of 9,192,631,770 energy transitions of the cesium atom. This recharacterization ushered in the era of atomic timekeeping and Coordinated Universal Time (UTC).

Read more posts on kottke.org about:
time

kottke.org

Front page
About + contact
Site archives

Subscribe

Follow kottke.org on Twitter

Follow kottke.org on Tumblr

Like kottke.org on Facebook

Subscribe to the RSS feed

Advertisement

Ads by The Deck

Support kottke.org shop at Amazon

And more at Amazon.com

Looking for work?

More at We Work Remotely

Kottke @ Quarterly

Subscribe to Quarterly and get a real-life mailing from Jason every three months.

 

Enginehosting

Hosting provided EngineHosting