- #1
Stephanus
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Dear PF Forum,
Perhaps it's not a question, just a light discussion.
From this, we get the standard time
https://en.wikipedia.org/wiki/Caesium_standard, it's 9,192,631,770 ticks per second.
I think this number should be discreet. No need to tune it to some figures after decimal point.
Is this right? Although it wouldn't match 1/86400 day length. But, then again, for a very big body like Earth with all its dynamic changes (weather, ocean, tectonic movement) it can't be too precise.
Length
And from time, we get the standard length:
https://en.wikipedia.org/wiki/Speed_of_light
Which is 9,192,631,770 / 299,792,458. And I think 299,792,458 is not discreet. Is this true? This is the law of nature, right?Or..., as in https://en.wikipedia.org/wiki/Rømer's_determination_of_the_speed_of_light
We arbitrarily set the speed of light: 299,792,458 meter per second, (whatever "meters" means) and we define that length that time travels when Ca 133 ticks 299,792,458 (discreet?) times and call it 299,792,458 meters (discreet?)
Mass
In junior high, we were taught that 1 kg is the mass of 1 litre (length already defined) water in 3.980C. https://en.wikipedia.org/wiki/Properties_of_water#Density_of_water_and_ice. But there is 1 catch. It's 3.980C in 1 bar atmospheric pressure. But we define pressure in N/m2. And 1 Newton is the force to accelerate 1 kg for 1 meter per second per second. And we meet mass (KG) again .
So since Avogadro had set that 1 mole is 6.022140857(74)×1023 . So can we safely say that 1 gram is the mass of 6.022140857(74)×1023 hydrogen atoms? (Without deuterium/tritium isotop impurity?)
And I think the rest, energy, calorie, volt, etc are derived from this standard unit.
Perhaps my questions are not physical, but rather historical.
Are these numbers:
9,192,631,770, time
299,792,458, length
6.022140857(74)×1023 , mass
discreet?
Just curious to know .
Thank you very much
Perhaps it's not a question, just a light discussion.
TimeOrodruin said:No. The definition of a second is not based on the speed of light.
The definition of a second is defined using the frequency of the radiation from a particular caesium atom.
From this, we get the standard time
https://en.wikipedia.org/wiki/Caesium_standard, it's 9,192,631,770 ticks per second.
I think this number should be discreet. No need to tune it to some figures after decimal point.
Is this right? Although it wouldn't match 1/86400 day length. But, then again, for a very big body like Earth with all its dynamic changes (weather, ocean, tectonic movement) it can't be too precise.
Length
And from time, we get the standard length:
https://en.wikipedia.org/wiki/Speed_of_light
Which is 9,192,631,770 / 299,792,458. And I think 299,792,458 is not discreet. Is this true? This is the law of nature, right?Or..., as in https://en.wikipedia.org/wiki/Rømer's_determination_of_the_speed_of_light
We arbitrarily set the speed of light: 299,792,458 meter per second, (whatever "meters" means) and we define that length that time travels when Ca 133 ticks 299,792,458 (discreet?) times and call it 299,792,458 meters (discreet?)
Mass
In junior high, we were taught that 1 kg is the mass of 1 litre (length already defined) water in 3.980C. https://en.wikipedia.org/wiki/Properties_of_water#Density_of_water_and_ice. But there is 1 catch. It's 3.980C in 1 bar atmospheric pressure. But we define pressure in N/m2. And 1 Newton is the force to accelerate 1 kg for 1 meter per second per second. And we meet mass (KG) again .
So since Avogadro had set that 1 mole is 6.022140857(74)×1023 . So can we safely say that 1 gram is the mass of 6.022140857(74)×1023 hydrogen atoms? (Without deuterium/tritium isotop impurity?)
And I think the rest, energy, calorie, volt, etc are derived from this standard unit.
Perhaps my questions are not physical, but rather historical.
Are these numbers:
9,192,631,770, time
299,792,458, length
6.022140857(74)×1023 , mass
discreet?
Just curious to know .
Thank you very much