This Kilogram Has A Weight-Loss Problem

NPR ^ | 20 Aug 2009 | Geoff Brumfiel

[MosesKnows]

At what temperature?

The electron resonance frequency of the cesium atom does not vary with temperature.

[Billthedrill]

Aw, f'Petessake! Why not just get it right this time and make it an even two pounds? And while yer at it, could we please make a kilogram 1024 grams and a kilometer 1024 meters? And what was wrong with the furlong, anyhows?

Dang iggorant Yoorpeens. Sheesh.

[PapaBear3625]

Now define a second.

A second:

The second is 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 cesium 133 atom.

[agere_contra]

Temperature is to do with the movement of molecules.

At any temperature where Caesium is still Caesium, those hyperfine levels internal to Caesium won’t change.

Analogy: no matter how fast you drive your car, the distance between your pedals doesn’t change. Unless you crash the car :0)

[r9etb]

Now define a second.

Under the International System of Units, the second is currently defined as follows:

The second is 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.

That definition, btw, is actually used in real life for any number of precise timing applications, including your ATM and cell phone transactions.

[r9etb]

Analogy: no matter how fast you drive your car, the distance between your pedals doesn’t change. Unless you crash the car

Or unless you skid sideways at an appreciable fraction of the speed of light ... in which case the pedals would get closer together, as measured by an observer.

[dirtboy]

The second is 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.

They could re-define it as how long it takes the Obama Administration to spend $9,192,631,770.

[C19fan]

From wikipedia:

Under the International System of Units, the second is currently defined as

The second is 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.[1]

[KarlInOhio]

This didn't happen back in the old days when we defined weights and lengths based on barleycorns and kings' feet.

[BlueLancer]

Is that the unladen air-speed of an African or a European swallow?

[Lazamataz]

"Originally the meter was equal to the length of a piece of metal kept alongside the kilogram, but in 1983 it was redefined as the distance light travels in a vacuum over 299,792,458ths of a second."

Now define a second.

A second is the amount of time it takes light to travel 299,792,458 meters.

Q.E.D.

[CodeToad]

The Kilogram: A unit of measure designed by committee.

[CodeToad]

Define a meter.

[DuncanWaring]

In a vacuum.

[Lazamataz]

In a vacuum.

Define a vacuum.

[Billthedrill]

Is that the unladen air-speed of an African or a European swallow?

I don't kn- AHHHHHHHHH!!!!!!!

[Lazamataz]

A second is the amount of time it takes light to travel 299,792,458 meters in a vacuum, and a meter is the distance it takes light to travel in a vacuum for one 299,792,458th of a second.

I mean, it's all very plain and easy to understand, for goodness sake!

[Lazamataz]

Of course, we do need to define 299,792,458.

[dirtboy]

So while you are counting to 9,192,631,770 cesium hyperfines , you have to divide by 299,792,458.

So at the end of the day, a meter is how far light travels in a vacuum while a cesium 130 atom shakes its booty 30.6633189884984 times.

Sounds messy.

[BlueLancer]

"Define a meter."

Isn't that when you first approach a woman?