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 ...
Interesting article. GPS time even incorporates leap seconds to account for the Earth’s slowing rotation.
Why are there 24 hours in a ‘day’?.................
Good question, give me a second...
I want to know why the ocean hugs the shore.
Not all seconds are the same!
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!
Why do we drive on a parkway and park on a driveway?
Why 31 days in some months, 30 in others, and 28 in one ... unless there are 29?
It is NOT a funcion of the lunar cycle. Some months have two full moons.
Why not 10 36-day months with one 5-day “slack week” which stands on its own?
Good question. I don't know why but that fact makes the beach really nice. It's convenient having the shore and the ocean at the same place.
That’s what the Romans did.................
Groping caused by global warming.
Does this mean a second measured by atomic cycling in radioactive elements will be the same on any planet, in any galaxy, since it is no longer tied to Earth’s rotation?
Would anything impact the atomic measurement?
They used to be a couple and are still friends. If you go to a point where two oceans come together you will see a group hug.
It is the amount of time it takes for a pendulum that is exactly one meter long to travel from one end to the other.
I even believe GPS factors in general relativity to compensate for time dilation.
Some functions of time are based on natural cycles that can be measured here on earth. These would include a year, a season, a lunar month, and a day.
Other functions of time are human constructs. These include calendar months, weeks, hours, minutes and seconds.
What they're describing in this article is an attempt to convert seconds from a human construct to a period based on a natural cycle. This is a similar process that we've seen with metric measures that have been standardized over time.
It is because the calendars would be wrong if it were any other way.
Actually it’s based on what a New York second is.
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