3 ms·
We do use resonant frequency of certain atoms to define units, but it is not arbitrary, rather it was a transition chosen for it's extremely small width and eas
by krastanov 8y ago
We do use resonant frequency of certain atoms to define units, but it is not arbitrary, rather it was a transition chosen for it's extremely small width and ease of measurement. It is quite a bit less arbitrary than using the size of our planet or of an artifact we have made.
And we are getting even better, with definitions based on fundamental constants now, independent of a particular measurement experiment. This is as non-arbitrary as it can get (we will continue using a conversion factor to make the unit human scaled, but that is all).
- Double_a_92 8y agoBut one meter is still the length we are used to. So we got the resonant frequency of some atoms, which is arbitrary because they just happened to be relatively easy to measure for us... Multiplied by some arbitrary factor so the unit reaches the usual length. That doesn't seem very fundamental to me. Could you imagine proposing that to some intergalactical economic union as new standard?
- ElBarto 8y agoThe resonant frequency of the atom is not arbitrary, it is a physical constant. That's the key and the point: It allows to measure exactly 1 second anywhere in the universe because the resonant frequency of that atom is the same anywhere in the universe. Compare with a previous definition of the second as a fraction of the solar day... A solar day isn't in fact constant and, in any case, once you leave earth it means nothing at all.
- ElBarto 8y agoThe definitions are still arbitrary. The important change is that they are arbitrary numbers of a fundamental physical constant instead of being completely arbitrary. That means that the unit may be exactly measured anywhere in the universe based on the definition only without the need of any artifact.