Ask_a_debtor said:
mkrnhr said:
Maybe I'm missing something but I guess
it would make sense if the Hz or second unity is related to some intrinsic natural phenomenon, no?
Edit :
I mean all I can find about the definition of the second (or Herz by the same occasion) is from wikipedia :
Wikipedia said:
The second (SI symbol: s), sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock.
Early definitions of the second were based on the motion of the earth: 24 hours in a day meant that the second could be defined as 1⁄86 400 of the average time required for the earth to complete one rotation about its axis. However, nineteenth- and twentieth-century astronomical observations revealed that this average time is lengthening, and thus the motion of the earth is no longer considered a suitable standard for definition. With the advent of atomic clocks, it became feasible to define the second based on fundamental properties of nature. Since 1967, the second has been defined to be
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.
I agree, hertz is based on cycles per second. And the definition of the second is essentially arbitrary^^.
wikipedia said:
The hertz (symbol: Hz) is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon.
So having whole numbers work for 432 tuning and not 440 tuning is based solely on convention.
Yes, I agree, definition of a second is arbitrary and as such it's 'removed' from intrinsic natural phenomena.
Moreover if we look at the present-day definition of second
wikipedia said:
The definition of the second was later refined at the 1997 meeting of the BIPM to include the statement
This definition refers to a caesium atom at rest at a temperature of 0 K.
The revised definition would seem to imply that the ideal atomic clock would contain a single caesium atom at rest emitting a single frequency. In practice, however, the definition means that high-precision realizations of the second should compensate for the effects of the ambient temperature (black-body radiation) within which atomic clocks operate, and extrapolate accordingly to the value of the second at a temperature of absolute zero.
and for absolute zero
wikipedia said:
Absolute zero is the theoretical temperature at which entropy would reach its minimum value. The laws of thermodynamics state that absolute zero cannot be reached because this would require a thermodynamic system to be fully removed from the rest of the universe.
it can be seen that this definition has very little to do with Nature.
On the other hand, from the old definition of second
wikipedia said:
Early definitions of the second were based on the motion of the earth: 24 hours in a day meant that the second could be defined as 1⁄86 400 of the average time required for the earth to complete one rotation about its axis. However, nineteenth- and twentieth-century astronomical observations revealed that this average time is lengthening, and thus the motion of the earth is no longer considered a suitable standard for definition.
it can be said that second has been related to Nature through Earth's rotation.
(some things about 1/(24×60×60) choice for the definition of second are nicely explained in SHOTW, ch. 11 – Time)
Time as such is only a convention and I see it as a measure of interaction/change, especially associated with periodic changes/motions in Nature.
As we live on BBM and as such we are related to it, it's 'natural' that we're measuring time as it is 'seen' on Earth and common periodic motion on Earth is its rotation. So it's natural choice to relate definition of time to Earth's rotation.
This was probably 'little' off topic. To conclude I'll quote something that came to my mind today when pondering about time.
El Condor Pasa said:
...
A man gets tied up to the ground
He gives the world
Its saddest sound,
Its saddest sound.
...
Thanks thevenusian for clarification between 'just' and 'equal tempered' tuning. Partch sure sounds strange. ;)
Here is youtube clip about Just vs. Equal Tempered tuning
http://www.youtube.com/watch?v=BhZpvGSPx6w&feature=related
Those displayed figures remind me on Lissajous' curves from my Classical Mechanics course http://en.wikipedia.org/wiki/Lissajous_curve
Just intonation bass
http://www.youtube.com/watch?v=aekjzKg3B30&feature=related
Thanks JonnyRadar for Brooks' link. It's a long read but looks like it's worth reading it. :)