6 ms·

It's more like, 1/time (i.e, frequency), is what has been defined by the observed atomic oscillator frequency, and the second is derived from that. A real weir

It's more like, 1/time (i.e, frequency), is what has been defined by the observed atomic oscillator frequency, and the second is derived from that. A real weird unit is km/l or miles per gallon, which cancels out to a unit of area.

kingkawn 5y ago
What’s to say any two oscillations of the atom are the same length?
- CamperBob2 5y ago
  It has to do with the assumed constancy of the so-called "fine structure constant." Google that for more info. TL,DR: the only way these atomic resonant frequencies can possibly change is if the fine structure constant varies from place to place, or over time. If that turns out to be the case, the discovery will invalidate, or at least upset, the last 100 years worth of physics and cosmology. It's all but unthinkable.
  - kingkawn 5y ago
    Sounds exciting
- taejo 5y ago
  You might be interested in the book Inventing Temperature by Hasok Chang which looks at similar questions but for temperature instead of time, both historically and philosophically. For example, you can define a temperature scale using the boiling point of water, but how do you know water always boils at the same temperature without a temperature scale? (And of course, it doesn't -- even at constant pressure, liquid water can exceed 100°C without boiling)
eesmith 5y ago
Regarding km/l or mpg, see https://what-if.xkcd.com/11/ https://what-if.xkcd.com/11/ which points out that the area term of the reciprocal - eg, liters per 100 kilometers - has a more direct physical interpretation: > "If you took all the gas you burned on a trip and stretched it out into a thin tube along your route, 0.1 square millimeters would be the cross-sectional area of that tube [in a car which gets 20 MPG]"
satori99 5y ago
> A real weird unit is km/l or miles per gallon, which cancels out to a unit of area. Ohms per square is another weird one. https://en.wikipedia.org/wiki/Sheet_resistance#Units https://en.wikipedia.org/wiki/Sheet_resistance#Units

kingkawn 5y ago

What’s to say any two oscillations of the atom are the same length?

CamperBob2 5y ago
It has to do with the assumed constancy of the so-called "fine structure constant." Google that for more info. TL,DR: the only way these atomic resonant frequencies can possibly change is if the fine structure constant varies from place to place, or over time. If that turns out to be the case, the discovery will invalidate, or at least upset, the last 100 years worth of physics and cosmology. It's all but unthinkable.
- kingkawn 5y ago
  Sounds exciting
taejo 5y ago
You might be interested in the book Inventing Temperature by Hasok Chang which looks at similar questions but for temperature instead of time, both historically and philosophically. For example, you can define a temperature scale using the boiling point of water, but how do you know water always boils at the same temperature without a temperature scale? (And of course, it doesn't -- even at constant pressure, liquid water can exceed 100°C without boiling)

eesmith 5y ago

Regarding km/l or mpg, see https://what-if.xkcd.com/11/ https://what-if.xkcd.com/11/ which points out that the area term of the reciprocal - eg, liters per 100 kilometers - has a more direct physical interpretation: > "If you took all the gas you burned on a trip and stretched it out into a thin tube along your route, 0.1 square millimeters would be the cross-sectional area of that tube [in a car which gets 20 MPG]"

satori99 5y ago

> A real weird unit is km/l or miles per gallon, which cancels out to a unit of area. Ohms per square is another weird one. https://en.wikipedia.org/wiki/Sheet_resistance#Units https://en.wikipedia.org/wiki/Sheet_resistance#Units