# Precise Measurements

1. Oct 16, 2007

### Rahmuss

I'm not sure which location to post this in; but since it deals with the very small (sub-atomic), then I'll post it here.

Does anybody know just how precise they can measure time? Can they measure seconds down to 50 yotta seconds ($$10^{-24}$$)?

I have a theory (well, not quite that far yet, just a thought so far really) that would need to detect a difference in $$51.7*10^{-24}s$$ as an average, and some values would be much smaller.

Does anyone know how short of a time interval we can measure currently?

2. Oct 16, 2007

### meopemuk

Measuring time is equivalent to counting oscillations of some periodic process. Traditional (e.g., Cs) atomic clocks used radio and microwave frequencies. The corresponding oscillation period in the nanosecond range. Recently a "frequency comb" technique has been invented which has allowed to count electromagnetic oscillations in the visible spectrum. This is the femtosecond range, which is still 10 orders of magnitude too coarse compared to your needs.

Eugene.

Last edited: Oct 16, 2007
3. Oct 16, 2007

### Rahmuss

meopemuk - Wow! Thanks for the quick answer. That's good to know. I guess I'll work on that theory later. :D

Oh, hey, I thought of another way to try and accomplish what I need. Do we know how long absorption and emission takes for a hydrogen (single electron) atom in ground state? And if so, is there a way to determine which direction the re-emitted photon will travel? My guess is that the absorption and emission is not calculable and that the direction of the emitted photon could be anybody's guess... is that right?

Last edited: Oct 16, 2007