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Ville502

Define "Second"

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What is the formula for "second"?

Edited by Ville502
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http://letmegooglethat.com/?q=how+is+a+second+defined

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A second used to de defined as 1/86400 of one mean solar day.

But with the ever increasing need for accuracy and the knowledge that the Earth's rotation rate was not constant, this was changed to a set fraction of the tropical year (at the start of a particular epoch). This was finally changed to today's definition of  "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom" (at a temperature of 0 K).  This particular number of periods was chosen so that the duration of the second exactly matched that of the one based on the tropical year.  This was a more practical standard as you can't very well go back in time to check the accuracy of your clock against the length of the tropical year in 1900, but you can check it against the radiation emitted by a caesium-133 atom. 

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I am tempted to say "'second' comes between 'first' and 'third'".

Edited by Country Boy

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8 minutes ago, Country Boy said:

I am tempted to say "'second' comes between 'first' and 'third'".

Not far off actually lol.

Second division of an hour by sixty.

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1 hour ago, Endy0816 said:

Not far off actually lol.

Second division of an hour by sixty.

And 'minute" for the same reason:

Quote

"one-sixtieth of a minute of degree," also "sixtieth part of a minute of time," late 14c. in geometry, from Old French seconde, from Medieval Latin secunda, short for secunda pars minuta "second diminished part," the result of the second division of the hour by sixty (the first being the "prime minute," now called the minute), from Latin secunda, fem. of secundus "following, next in time or order" (see second (adj.)). 

https://www.etymonline.com/word/second#etymonline_v_23075

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It is also the begin of the hexadecimal system for measuring time. Less than a second are measured in /100. Which is completely bogus.

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1 hour ago, michel123456 said:

It is also the begin of the hexadecimal system for measuring time. Less than a second are measured in /100. Which is completely bogus.

sexadecimal. Hexadecimal = base 16; sexadecimal = base 60. Also, time is measured in very mixed base; 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, 365.25odd days in a year, and (mostly) decimal from that point on. 

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1 hour ago, michel123456 said:

It is also the begin of the hexadecimal system for measuring time.

Hexadecimal is base 16

 

(edit: xpost with uncool)

Quote

Less than a second are measured in /100. Which is completely bogus.

It's factor of 10, not 100, and what's bogus about it? That makes it consistent with the rest of physics, which is based on SI units. Everything else in physics is done in decimal. We hang on to historical units like the minute, and longer intervals that are in common use, but the SI unit is the second, so it's perfectly consistent to apply decimal to fractions of a second.

 

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1 hour ago, uncool said:

sexadecimal. Hexadecimal = base 16; sexadecimal = base 60.

It is sexagesimal not sexadecimal.

https://en.wikipedia.org/wiki/Sexagesimal

 

https://www.merriam-webster.com/dictionary/sexadecimal

"Definition of sexadecimal: of or relating to sixteen or sixteenths : proceeding in computation by sixteens : expressed in the scale of sixteens"

ps. Sorry for nitpicking..

 

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5 hours ago, michel123456 said:

It is also the begin of the hexadecimal system for measuring time. Less than a second are measured in /100. Which is completely bogus.

The use of base 60 goes all the way to the Babylonians

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Sorry lost in translation from "exadiko" (εξάδικο) base 6 in Greek.

And instead of "bogus" I should have said "incoherent".

Here a clock in decimal system https://en.wikipedia.org/wiki/Decimal_time#/media/File:Decimal_Clock_face_by_Pierre_Daniel_Destigny_1798-1805.jpg

Senary system (I had never heard of it in English. I learned something today).

https://en.wikipedia.org/wiki/Senary

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