I read that there is an effort to define a kilogram in terms that can exactly be reproduced in a lab. Why has it taken so long to get this done? It seems this would be fairly important. Edit Today I ...
If the metre is now defined as the distance light travels in vacuum in 1⁄299,792,458th of a second and the speed of light is accepted to be ...
This might be a question to ask in a Chemistry site, but because there is a lot of talk about redefining many units of measurements in terms of Avogadro's Number / the Mole, I was wondering why we ...
I could understand that the definition of a second wouldn't have an uncertainty when related to the transition of the Cs atom, so it doesn't have an error because it's an absolute reference and we ...
What is the exact dependence of the refractive index of air and the temperature? Is there a theoretical derivation of it?
I'm confused by the many contradictory descriptions I see about how UTC leap seconds are accounted for. I understand that there are various ways to handle them in common practice, and I've seen a ...
The reasons for choosing length, mass, time, temperature, and amount as base quantities look (at least to me) obvious. What I'm puzzling about is why current (as opposed to resistance, electromotive ...
I recently answered a question about the meaning of the word "dimension" as used in physics. In that response, I provided the definition given in the International Vocabulary of Metrology (VIM) and ...
I was wondering what dimension can mean in physics? I know it can mean the dimension of the space and time. But there is dimensional analysis. How is this dimension related to and different from the ...