# 1 Second

## Main Question or Discussion Point

What is the official count of one second? What I mean by this is: how would one go about measuring one second exactly? Basically, at the creation of a second, how was it measured?

Also, if a day is 23 hours and 56 minutes, wouldn't our clocks be off 4 minutes after each day? I understand the system of correction, but until time is 'corrected' for our clocks, we have the incorrect time, correct?

jcsd
Gold Member
The old defintion was 1/86,400 of a mean solar day and then it was 1/31556925.9747 of a tropical year, but since 1967 it has been 9,192,631,770 oscillations of a cesium-133 atom.

mathman
23 hrs 56 min. is time for one complete rotation of the earth on its axis. During this time the earth has moved in its orbit around the sun. The extra 4 minutes is needed to keep the same face toward the sun.

Originally posted by mathman
23 hrs 56 min. is time for one complete rotation of the earth on its axis. During this time the earth has moved in its orbit around the sun. The extra 4 minutes is needed to keep the same face toward the sun.
That's why it's called a siderial day. Because it is in relation to the backround of stars, not the sun we orbit.

People, people, people [mathman and ORW] I knew all this, I was simply asking would our clocks not be off each day increasing by 4 minutes.

jcsd, would you happen to know how many ticks an electric clock goes through before it turns another second?

A day is "noon to noon" which means we return to the same position wrt to the sun, not the stars. Hence our day is 24 hours long. The reason our clocks arn't off is because we build them to make 24 hours to be 24 hours. Its all arbitrary really.

jcsd
Gold Member
Originally posted by kyle_soule
People, people, people [mathman and ORW] I knew all this, I was simply asking would our clocks not be off each day increasing by 4 minutes.

jcsd, would you happen to know how many ticks an electric clock goes through before it turns another second?
No I ****ing don't

Integral
Staff Emeritus