Zenos paradoxes of motion generally refer to actual motion through space; however for Aristotle this is motion in only one sense; an other sense could be alteration, for example change in shape and so on.

Consider a motionless particle painted blue and which slowly changes in colour intensity and then back down again - in effect a slowly flashing blue dot.

Does Zenos paradox of motion apply to this situation?

Of course, were we to model this mathematically ie via coordinates, with one axis for time and the other for colour intensity then Zenos paradoxes apply; and the standard solution suffices to the extent it does.

But I want this question to be thought through physically - can it be?

Arjuna slay thy doubts and slay thy fears:

Cast your clouds upon the sea;

And then your storms upon the lands.

  • I don't know about your flashing blue dot, but apparently the ancient Greek philosophers -- don't know about the engineers -- had no notion of measuring the speed of an object. This led to the silliness that is Zeno's Paradox. Galileo, several centuries later, essentially dispensed with it with his simple speed-distance-time formula. I'm not sure why it is still an issue for some today. Apr 28, 2015 at 3:14
  • Well it takes an accurate clock to measure time; given the Greeks adoption of geometry we can safely say they knew how to measure distances; it wouldn't surprise me they couldn't measure speed due to not having a good clock; still just because one can't measure something accurately doesn't mean that one can't have a notion of it; for example Aristotle discusses the speed of a falling object as being proportional to weight and inversely proportional to the density of the surrounding medium; though this is wrong - it does show that they had the notion of speed. Apr 28, 2015 at 3:46
  • Galileos conception doesn't solve Zenos paradoxes; for example it's generally accepted that it's the notion of infinite sums that solve that particular problem; plus there are problems to do with continua vs discrete structure. Apr 28, 2015 at 3:49
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    @DanChristensen Metaphysics is not science. The notion of infinitely differentiable speed is still logically flawed in a metaphysical sense. Observation of the provably impossible is not an argument. The actual impossible thing needs to be found and rejected. What is impossible here is the infinite division of the motion of an object along a smooth curve. This was not resolved by Galileo, or even by Newton, but by the atomists' notion of vibration, and ultimately by Heisenberg. And it is still hard for most folks to believe.
    – user9166
    Apr 28, 2015 at 15:43
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    Its modern equivalent post-Boltzmann or deBroglie. Brownian motion or quantum vibration does not allow for infinite subdivision of Achilles path. If he did not make any progress at all, his center of mass would still jerk around uncontrollably at some level of subdivision of space. Basically, the modern atomists had to take a page from Heraclitus, and admit that rest is impossible, so motion is inevitable. Elea put physics on a given path that it stayed on for a very long time, but rest, not motion, it is an illusion.
    – user9166
    Apr 28, 2015 at 20:25

3 Answers 3


However you generate light, the excited medium always 'warms up' before it can emit it and 'cools down' before it stops. If the variation in the intensity of light is not a collection of short bursts that get spaced out further to give the illusion of dimming, it is driven by a current or heat which would have to vary continuously.

So in each case there is still a continuous process involved, unless you think of these effects at a quantum level. Whatever varies continuously is subject to Zeno's paradox.

At a quantum level, Zeno's paradox does not apply, because there is no absolute rest, and so the attempt to declare the particle not to have already moved by the time you establish its position is a complete non-sequitur. Heraclitus is right, and the Eleatics and all their successors are wrong, on this: The lack of motion is the thing that is essentially alien to all matter.


The answer in this case is no since the intensity of emitted light is the number of photons emitted per unit time, which is not a continuous quantity.


Yes it does. There is a middle color between the least color intensity and highest color intensity. There is a middle color between the middle color and the least color intensity, and so on. This halving goes on infinitely. Therefore, a change in color can never be completed.

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