[Haskell-cafe] Re: A few ideas about FRP and arbitrary access in time

Heinrich Apfelmus apfelmus at quantentunnel.de
Tue Mar 9 15:18:06 EST 2010

John Meacham wrote:
> On Tue, Mar 09, 2010 at 05:23:56AM +0000, Aaron Denney wrote:
>> On 2010-03-08, Brandon S. Allbery KF8NH <allbery at ece.cmu.edu> wrote:
>>> There is a discrete time quantum.  But unless you're doing simulations  
>>> at the quantum level, you really don't want to go there (even ignoring  
>>> that one second of real time would take a really long time to  
>>> calculate on current hardware :); stick to macrocosmic physics, which  
>>> is statistically continuous.
>> That's ... contentious.  In both quantum mechanics and GR, time is
>> completely, flattly, continuous.  In certain extremely speculative
>> frameworks attempting to combine the regimes in which they are
>> applicable, that may not be the case.  But for accepted physics models,
>> time really is continous.
> Hmm.. I thought something interesting happened on the scale of the plank
> time, 10^-44 seconds or so. Or is that only relevant to our ability to
> _measure_ things at that scale and not the continuity of time itself as
> far as QM is concerned?

It may sound strange, but continuous quantities are often an
approximation. For instance, a bar of steel is composed of a finite
number of atoms, but if you want to know how it behaves under load
(theory of elasticity), you can model it as a continuous mass just fine
because the number of atoms is huge.

Same goes for time. It doesn't really matter what happens in minuscule
time scale; for the purpose of Newtonian mechanics, time is continuous.
(It's continuous for the purpose of modeling more fundamental theories
as well.) The key point is that this is not "absolute" reality, it's
just a model.

Heinrich Apfelmus


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