The telling of this paradox I most remember says, “Between point A and point B, there are an infinite number of points through which the arrow must pass. So it must take the arrow an infinite amount of time to pass through those points. How can the arrow get from point A to point B?”
This is the problem with mapping a mathematical metaphor onto reality: it doesn’t always work. If the metaphor disagrees with the observation that the arrow does get from point A to point B, then it’s not doing useful work.
In fact, modern physics tells us there is a smallest possible length, the Planck length, which means there is not an infinite number of points through which the arrow must pass. Still, you don’t need modern physics to defeat this paradox; you only need the ability to observe that the arrow does get from point A to point B.
I thought the problem with the paradox was that the math was wrong. Even if we assume that there’s an infinite number of points between A and B, the more points we have, the less time the arrow would spend on each point, so if the number of point is infinite, the arrow would spend an infinitesimal amount of time at each point.
As it turns out, you need to know about time series and limits (and maybe l’Hopital’s rule) in order to correctly calculate the total flight time of the arrow (or, rather, to prove that it does not change even when the number of points is infinite), because infinity is not a number, and neither is 1 / infinity. Zeno did not know about these things, though.
Yes, you’re right. You can defeat the paradox on mathematical grounds, without having to appeal to physics. But Zeno could have defeated it on his own without using any math, simply by realizing that his metaphor was not paying rent.
I think ArisKatsaris (on the sibling comment) is right: Zeno’s whole goal was to prove that physics doesn’t work (ok, he didn’t call it “physics”, but still), so using physics to disprove his paradox would be nonsensical.
Zeno’s argument was that movement was an illusion, that all was one—that was the point of his paradoxes. The fact that things seemed to move, in combination with his paradox, proved (to him) that reality was an illusion.
The telling of this paradox I most remember says, “Between point A and point B, there are an infinite number of points through which the arrow must pass. So it must take the arrow an infinite amount of time to pass through those points. How can the arrow get from point A to point B?”
This is the problem with mapping a mathematical metaphor onto reality: it doesn’t always work. If the metaphor disagrees with the observation that the arrow does get from point A to point B, then it’s not doing useful work.
In fact, modern physics tells us there is a smallest possible length, the Planck length, which means there is not an infinite number of points through which the arrow must pass. Still, you don’t need modern physics to defeat this paradox; you only need the ability to observe that the arrow does get from point A to point B.
I thought the problem with the paradox was that the math was wrong. Even if we assume that there’s an infinite number of points between A and B, the more points we have, the less time the arrow would spend on each point, so if the number of point is infinite, the arrow would spend an infinitesimal amount of time at each point.
As it turns out, you need to know about time series and limits (and maybe l’Hopital’s rule) in order to correctly calculate the total flight time of the arrow (or, rather, to prove that it does not change even when the number of points is infinite), because infinity is not a number, and neither is 1 / infinity. Zeno did not know about these things, though.
Yes, you’re right. You can defeat the paradox on mathematical grounds, without having to appeal to physics. But Zeno could have defeated it on his own without using any math, simply by realizing that his metaphor was not paying rent.
I think ArisKatsaris (on the sibling comment) is right: Zeno’s whole goal was to prove that physics doesn’t work (ok, he didn’t call it “physics”, but still), so using physics to disprove his paradox would be nonsensical.
Zeno’s argument was that movement was an illusion, that all was one—that was the point of his paradoxes. The fact that things seemed to move, in combination with his paradox, proved (to him) that reality was an illusion.