3 ms·
1) There is no DC. We do our scientific work at millihertz frequencies (one cycle every 1000 seconds or so). The age of the universe is ~13.6 billion years, wh
by ISL 7y ago
1) There is no DC.
We do our scientific work at millihertz frequencies (one cycle every 1000 seconds or so). The age of the universe is ~13.6 billion years, which corresponds to ~10^-18 Hz. Thinking about the zero-frequency limit is a useful crutch, but all things are always changing. Materials creep, the Earth deforms, temperature changes, aging happens. There is no DC.
2) Small forces for long times yield great change
We study torques as small as 10^-18 N-m acting on ~100 g objects. A willingness to apply a very weak force for a long time can often yield measurable, often large results.
- throwlaplace 7y ago> There is no DC. what does that mean? just because there's ripple doesn't mean it's not DC. DC doesn't mean flat and AC doesn't mean non-flat (AC means periodic).
- ISL 7y agoDC generally means time-invariant/the zero-frequency limit. Offhand, I can't think of a measured physical quantity (aside from the physical constants, so-far observed to be constant within uncertainties) that has been constant for all time.
- throwlaplace 7y agobut that's like saying there's no such thing as a 1 or 0 (or any number at all). of course. but given enough time/money/effort you can get close to zero frequency right? just add enough smoothing caps and wait right?