Some people like to live in the moment, or in the now. That is possible a more psychological way of interpreting a moment. But physically seen, does this contain a time lap? So is it actually possible to live in the now? Or is the Planck time (5.39 × 10 −44 s) the time lap which defines 'now'?

Or when it is 17:00 h, does that moment has a time lap? Perhaps mathematically it could have a now, because 17:00 seems to be very exact. But in practice, regarding special relativity, a clock can't indicate the time precisely 17:00 because that would also imply that there is an infinite number of decimals which due to all motions can't stay zero. Or can they?

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    physics.stackexchange.com/questions/35674/… discusses this from a Physics viewpoint and googling "is time continuous or discrete" (no quotes) provides many other opinions. The general consensus is the answer is unknown (it might also be unknowable but that's saying something different).
    – user935
    Nov 4 '17 at 17:16
  • Planck time is the physicists intuitive guess that something special is likely to happen at this scale. Nov 5 '17 at 1:39
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    i'd suggest reading Hermann Weyl on the Continuum. You are speaking of mathematical time but he points out the time as experienced ('intuitive' time) is not at all like this.
    – user20253
    Nov 5 '17 at 11:46

I think that defining "now" as the time lapsed from one planck second to the next is not the best definition. Afterall, a planck second is only the time it takes for light to travel in a vacuum the smallest meaningful distance. That means that half of a planck second exists, just nothing, literally nothing can happen in that time period. For humans, the smallest meaningful time scale biologically would probably be 1/60 seconds which is the maximum limit of human vision. So long as the people that "live in the now" do something meaningful with each meaningful moment that they have, they are justified in their doing. But the length of a meaningful moment differs for everyone, so it's still an open-ended answer.


The act of study of anything, changes it. By simply reflecting on a moment in your mind, time passes, and your memory of the moment changes over time or may not be accurate in the first place. The only way to truly live in the now would be to have no short or long term memory. Yet without any memory at all you would be challenged with any situation or action you attempted.

Also your now is not the same as another persons now, because of relativity. I would suppose the philosophy of living in the now would be to minimize concerns with the past or future and give as much attention to any task at hand instead.


Physically, the present should be a dot in the line of time. Past would be on the left side of the dot, and the future would be on the right side.

But not for our perception. Our perception is based on memories. The past is not a line, but a set of segments on the left side, inside what we call the long-term memory. The present is also a segment, on the short-term memory.

Think on sounds. A sound has only a meaning when it has a duration. If the present would be a dot in time, the state of the air on such instant wouldn't be described as sound. Our memory creates the present by means of memory. How long is the present? Difficult to say. You can ask yourself "what sound am I hearing now?". Short term memory is on the range of tens of seconds.

Did you know that we still don't know what is "duration"? Even relativity uses time, but we still don't know what a duration is. Apparently, time and space don't exist at all. They are only in our perception.

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