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Is time descrete or continuous?

Time has no granularity greater than 5.39x10^(-44) second. At smaller scales than that there exists no physics to comment upon it, either way.

y ... no one knows.

But it is certainly reasonable that it is discrete, quantized, just as is everything else.

Accepting Uncle Al's as the real explanation.
It can't be continuous. Everything we thought was wasn't. Probably when light became quantized, continuous went out the scientific vocabuary.

y,

Check out Peter Lynds' paper on time and motion,
entitled: Time and Classical and Quantum Mechanics: Indeterminacy vs. Discontinuity

"Time has no granularity greater than 5.39x10^(-44) second. At smaller scales than that there exists no physics to comment upon it, either way."

What exactly do you mean by this; stuff doesn't move, forces don't act on particles?

"Time has no granularity greater than 5.39x10^(-44) second. At smaller scales than that there exists no physics to comment upon it, either way."

Should that not be:

"Time may have no granularity greater than 5.39x10^(-44) second. At smaller scales than that there exists no physics to comment upon it, either way."

Blacknad.

yes

Inetesting. Either way on that small of a scale, humans can just assume it's continous... unless you're working with quantum physics...

DA Morgan,

you're saying about time that "it is certainly reasonable that it is discrete, quantized, just as is everything else."

I simply have no idea what you mean with this. Are you implying that space IS discrete? Is this something you KNOW? Or are you thinking about the fact that our most fundamental descriptions of Nature are based upon quantum mechanics - and therefore in this sense - "quantized"?

In string theory, distances below the string scale L_s does not really make sense since there is a duality - called T-duality - which relates a circle with radius R to one with radius 1/R. So when you are trying to probe smaller distances you actually end up with a description in terms of large distances. And furthermore, because of quantum mechanics distances below the Planck length L_p also does not really makes sense, since if you want to probe space with a resolution of order R then you need energy with E > 1/R. It will create a black hole unless R > L_p.

What this tells us about time is still unknown, I think. But most likely, time also does not really make sense at small scales....

Implying that space is discrete? I am stating that space is discrete. And I don't know how you could go about binding together, as space-time a single entity a dimension that is not discrete with three or more that are.

Strings exist in our theories for one and only one reason: Points don't work. Strings, by the very nature of their definition have a discrete size and nothing can be smaller. Half-a-string's length makes no sense.

And in the same sense 1/2 of the amount of time it takes a photon to move a string's-length makes no sense.

Interesting question,but do you what are you asking?
Time is there to help you just like Space Scale.
If Space is discreet then why not Time.

dvk wrote:
"but do you what are you asking?"

What? Were you trying to put words together to create a coherent thought?

dvk wrote:
"Time is there to help you just like Space Scale."

What? Is this supposed to be a sentence?

DA Morgan: I'm sorry, but you're wrong here;

1) strings are extended objects and have a characteristic length, the string length L_s which is related to their tension alpha' as

L_s = hbar x c x sqrt(alpha')

where hbar is Plancks constant and c the speed of light. But that does not imply that space in itself is discrete; strings can virtually be of any size - cosmic strings, for example, could be light-years across - it is just a matter of how much energy you put into the string ;-) But, of course, a string cannot probe distances smaller than its size.

2) in string theory there are also extended objects called D-branes which can probe smaller distances ;-)

All true. But in what manner does any of this indicate a continuum rather than discreteness?

You will be hard pressed to find photons with non-discrete wavelengths. Given that everything we have proven to exist has a wavelength ... are you expecting a different behaviour with branes (still purely theoretical) or strings (still purely theoretical)?

I'd like to know if time and space are discrete. What would the implications be for calculus? The underlying assumption is continuity (and typically smoothness). The disrete analog would have limits approaching the minimum length, not zero. Integration would be sums (with usually so many terms that you would want to use a continuous approximation). I'm not sure what the analog of derivatives would be. Maybe the common value of the ultimate ratios of delta x to delta t.

I suspect that general relativity would need to be reworked to get at small scales...

steveM49 wrote:
"I suspect that general relativity would need to be reworked to get at small scales.."

I think this is already known to be true.

I think the implication for the calculus is that it is an approximation. But then that's really been the basic assumption for it all along.

Just how would you expect to observe
any discontinuity in time?
It would involve somehow getting
'outside of space/time` to make an observation.
Pragmatist

"Lord, are we worthy of the task that lies before us,....or are we just jerking off?"

I doubt a discontinuity will ever be observed, which realistically means, within my lifetime.

But I suspect the math describing reality will work far better when written to incorporate time as being a discrete unit. Though I can make an argument right now, for what it is worth, that I think would be impossible to refute.

DAM's zero-value argument.
Time is discrete and consists of units that correspond to the amount of time it takes a photon to travel one Planck's length.

Because quite frankly I doubt anything smaller is measurable. So it should be reasonable to consider it the unit of granularity.

The only experimental proof we have is that energy is quantised. Is it then reasonable to extrapolate and postulate that "everything else" is quantised? Maybe this is the reason why quantum field theory is, according to Penrose, a quaqmire.