[time-nuts] Are there limits to the accuracy of clocks?

Don Moss moss at microwave.nsstc.nasa.gov
Wed Mar 29 20:27:29 EST 2006

On Wed, 29 Mar 2006, Mike S wrote:

> At 06:45 PM 3/29/2006, Don Moss wrote...
> >> The Planck length is the scale at which classical ideas about gravity
> >> and space-time cease to be valid, and quantum effects dominate. This is
> >> the ?quantum of length?, the smallest measurement of length with any
> >> meaning.
> >>
> >> The Planck time is the time it would take a photon travelling at the
> >> speed of light to across a distance equal to the Planck length.
> >
> >I'm a little "uncertain" how to interpret this.  Does that mean that time
> >and distance (length) are granular rather than continuous?  So there are
> >only discrete moments, and time doesn't flow smoothly; it jumps from one
> >instant to the next, and the instants are separated by the Planck time?

> If time and distance were constrained to integral Planck units, how could
> there be any speed other than light speed or integral divisors thereof? It
> would require velocity to be discontiguous - going at light speed while moving
> one Planck distance in one Planck time, then pausing (for an integral number
> of Planck times - so the next slowest speed would be 1/2 c), then moving one
> Planck distance in one Planck time. How would an electron travelling at 70% c
> "know" to pause 1 here, 0 there, whatever it takes to satisfy the measurement?
> The physicist would likely answer that quantum uncertainty fills the gaps and
> that it cannot be understood in human terms, only mathematical - but that's
> simply petitio principii.

I've actually tried to imagine a "jumpy" world like that, thinking that
that's what the physicists were suggesting.  It's weird, and it seems to
my untrained mind to lead to contradictions -- such as the hypotenuse of
a triangle not being commensurate with the length of the other sides; which
winds up being a discussion of irrational numbers such as the square root
of 2.  I've heard that a lot of people had a problem with that idea at one

Anyway, with all lengths being integral, such geometric figures are
inconceivable, which seems to me to logically disprove the whole idea.

> I think the key is that physics at that level _is_ just math, not reality.
> That experimental results work only reflects that we've created a fairly
> self-consistent model, not discovered true nature. Newtonian physics works in
> most real-world cases. Relativistic physics covers almost everything else.
> Quantum theory (or QED, or string theory or the Higgs boson, or whatever else)
> are simply closer approximations of full self-consistency (which shouldn't be
> confused with reality).
> At some point, I think we run into Godel - we can't self-refer and be complete
> in our understanding, so if what we're trying to figure out is the physics of
> our own nature, it simply can't be done.
> I know it doesn't satisfy human nature to say "we don't and can't know what
> time _really_ is" but I think that is the case.

Too often we are stuck with plausible explanations when what we want is
truth.  Most people seem to be happy to settle for that, but for me it's

	- Don

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