Posted on 01/19/2018 10:32:02 AM PST by MtnClimber
Just what is a second, exactly? The question has been open to interpretation ever since the first long-case grandfather clocks began marking off seconds in the mid-17th century and introduced the concept to the world at large.
The answer, simply, is that a second is 1/60th of a minute, or 1/3600th of an hour. But that’s just pushing the question down the road a bit. After all, what’s an hour? That answer is related to the best means of time-keeping ancient civilizations had — the movement of the Earth through the heavens. The amount of time it takes for the Earth to turn once about its axis, or for it to rotate once about the sun, is fairly stable, and for much of human history, it sufficed as a way of marking the passage of time. Days, hours, minutes — they’re all just derivatives of planetary motion.
Today, however, when computers perform operations at the rate of 4 billion cycles per second, we need a better measure. The rotation of Earth, and its orbit, change slightly over time. Earth’s rotation, for example, is slowing slightly. So measuring a second based on rotation would mean that a second would get slowly longer over time. Ultimately, we couldn’t compare the second of today to the second of yesterday.
So, to pin down a truly timeless measure of a second, scientists in the 1950s devised a better clock, one based not on astronomical processes but on the movement of fundamental bits of matter — atoms — whose subtle vibrations are, for all intents and purposes, locked in for eternity. Today, one second is defined as “9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom”.
That’s a mouthful.
(Excerpt) Read more at blogs.discovermagazine.com ...
https://www.scienceabc.com/eyeopeners/why-are-there-24-hours-in-a-day-and-60-minutes-in-an-hour.html
Pinging for an answer also.
Ah, whyncha take a five rod walk off a two furlong pier into four fathoms.
It might have been 360/10o = 36 hours/day. Or 360/36o = 10... All sorts of possible definitions but, some how those were adopted. It is all based on astronomical observations.
Only Einstein's notion of Relativity since velocity effects time.
Our 24-hour day comes from the ancient Egyptians who divided day-time into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the day-time, says Lomb. “Night-time was divided in 12 hours, based on the observations of stars.
The Romans thought of February as an unlucky month. When they decided to honor Julius Caesar with his own month they took a day from February to make July a long month. Same thing happened when they honored Augustus with his own month. Might as well get rid of February as quickly as possible.
More like a bar fight.
Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity.
-Albert Einstein
-PJ
One second of kissing a girl for the first time is not the same as one second of placing your hand on a stove burner on high!
Or being on the wrong side of a locked bathroom door ....
Both are lesbians?
Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity. -Albert EinsteinSure is PJ
bttt
Or monumental food fight. Check the currents off the south tip of Africa...
Because that doesn't deal with the pesky extra 1/4 day each year...
That is the key; my memory fails me.
It may go back to the Babylonian math and astronomy system.
physics.nist.gov/cuu/Units/second.html
(affirmed by the CIPM in 1997 that this definition refers to a cesium atom in its ground state at a temperature of 0 K) ...
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