Axioms
Axioms
Posted Feb 24, 2021 1:00 UTC (Wed) by SiB (subscriber, #4048)In reply to: Axioms by mpr22
Parent article: An introduction to lockless algorithms
Some years ago in our coffee room at the institute there was a discussion about the possibility that the fine-structure constant α may not have been constant in the past after all. The question was raised, which of the constituents of α=e²/(4πε₀ħc) may be the reason. Well, the answer is e, if at all. α is a constant without units. It is pure physics. It defines the strength of electromagnetic interactions. The universe cares a lot about the value of the fine-structure constant α. In our experimental units it is the charge of the electron e that represents that strength, but in the end, it also just defines units of measure.
Theoretical physics defines the units differently than experimental physics. They mostly use c=4πε₀=ħ=k=1. Everything is measured in eV or eV¯¹.
From a theoretical point I am a bit unhappy about the new definition of the SI units. They fixed the value of e, although it indirectly represents a quantity the universe cares about. The cost is that µ₀ and ε₀ are now _not_ fixed by definition in the SI, as they were before, like Wol said.
Ideally, all units were defined by fixing the value of some fundamental constant. We are now almost there. The second is still defined by an artifact. At least it is an atom, so it can be reproduced everywhere in the universe. To fix that we need to fix the gravitational constant. But metrology defines units by what they can measure with the best precision. The gravitational constant does not apply, it has to catch up at least eight orders of magnitude in precision.