Zeno's Paradoxes

[Mentat]

There are a couple of Zeno's paradoxes that I just don't agree with. There may be something to them that I haven't understood properly, but I just don't agree with them as I've understood them.

One is the paradox of motion. He posits that you can never get anywhere because you have to cover half of the remaining distance everytime. Since there are infinite halves, you can't ever get there. I disagree because you don't have to continue to cover half of each new distance, you can cover more than that, if you so desire. Also, once you have come into physical contact with something, I think it can be reasonably concluded that you have "gotten there".

I would very much like that someone should explain where my misunderstanding of this paradox is, before I go on to the next one please.

Any help would be appreciated.

[wuliheron]

There must be million websites devoted to this paradox. Here's the most mickey mouse plain english one I could find.


http://www.mathacademy.com/pr/prime/articles/zeno_tort/index.asp

[Mentat]

Ok, then that particular paradox is not considered authentic?

[Lifegazer]

Originally posted by Mentat
There are a couple of Zeno's paradoxes that I just don't agree with.

I hope you don't mind me hogging your posts tonight. I like supporting Zeno, when given a chance.

One is the paradox of motion. He posits that you can never get anywhere because you have to cover half of the remaining distance everytime. Since there are infinite halves, you can't ever get there. I disagree because you don't have to continue to cover half of each new distance, you can cover more than that, if you so desire.

That's not the point Mentat. A 'half' is used because it's the most readily-understandable fraction. Even if you were to traverse three-quarters of the distance every time, Zeno's ultimate conclusion would still apply: that if you travel 3/4 of a length, and then 4/7's of the remaining-length, and then 7/9's of the remaining-length - ad-infinitum - then you will never reach the end of that length.
I want to say more about this. But one of my favourite films is just starting...

[Mentat]

Originally posted by Lifegazer
I hope you don't mind me hogging your posts tonight. I like supporting Zeno, when given a chance.

That's not the point Mentat. A 'half' is used because it's the most readily-understandable fraction. Even if you were to traverse three-quarters of the distance every time, Zeno's ultimate conclusion would still apply: that if you travel 3/4 of a length, and then 4/7's of the remaining-length, and then 7/9's of the remaining-length - ad-infinitum - then you will never reach the end of that length.
I want to say more about this. But one of my favourite films is just starting...

Which film is that?

I understand that it could be any fraction, and that a point particle, with no real determined size, couldn't get to the end. However, I have mass, and so I would eventually be touching whatever was at the "end of the line".

[wuliheron]

Originally posted by Mentat
Ok, then that particular paradox is not considered authentic?

Nahhh.... its only valid according to fundamentalist mathematicians in their ivory towers. Quantum Mechanics has its own versions of the paradox:

http://www.tcd.ie/Physics/Schools/what/atoms/quantum/uncertainty.html

No doubt it is easy, expedient, and comforting to tell little kids mom and dad know what life is all about and have a firm grasp on the situation, but the reality between adults is different. That's also why all these teachers and professors still teach outdated fundamentalist stuff first, and then get down and dirty with a more honest admission of the extent of their ignorance.

[Tom Mattson]

Originally posted by Mentat
One is the paradox of motion. He posits that you can never get anywhere because you have to cover half of the remaining distance everytime. Since there are infinite halves, you can't ever get there. I disagree because you don't have to continue to cover half of each new distance, you can cover more than that, if you so desire.


The fraction used really doesn't matter. The reason Zeno's paradox fails is that, in his argument, he assumes that the infinite series of powers of 1/2 diverges to infinity, when in fact it converges to 1.

It goes like this:

Assume you are traveling at speed v and must cross a distance L in time T.

Before you can get to L, you must get to L/2. Once you have gotten to L/2, you must then get to 3L/4, etc. This continuous halving of distances can be represented by the series:

Distance=L/2+L/4+L/8+...

Note that it takes an infinite number of steps to travel the distance. Since it is not possible to perform an infinite number of steps in a finite time, it is not possible to cross any distance L in time T at speed V.

Zeno's mistake is in assuming that an infinite number of steps cannot be done in a finite amount of time. In other words, he tacitly assumes that it would require an infinite amount of time, and so could never be done.

Is that true? Let's see.

T=L/v=(1/v)Σn=0oo(1/2)n

The series on the right is a geometric series. In order for Zeno's argument to hold up, it would have to blow up to infinity--but it actually converges to 1.


Also, once you have come into physical contact with something, I think it can be reasonably concluded that you have "gotten there".


That suggests the conclusion is wrong, but it doesn't say why it is wrong. The flaw in Zeno's argument is in assuming the divergence of a series that actually converges.

[ahrkron]

Originally posted by Mentat
One is the paradox of motion. He posits that you can never get anywhere because you have to cover half of the remaining distance everytime. Since there are infinite halves, you can't ever get there. I disagree because you don't have to continue to cover half of each new distance, you can cover more than that, if you so desire.

I think it is here's where you miss the point of the paradox. You cannot "cover more than that" without covering the menitoned half.

i.e., In order to cover 1m, you have to cover half a meter first, no matter how you do it, you will pass through the middle point. Similarly, on your way to cover the first half, you necessarily passed trhough the 25cm point. No matter what you are thinking during your movement (what you are "aiming for"), the matter is one of principle: you need to pass through an infinity of "middle-points".

Since all those partial movements, the paradox goes, must take some time, and you need an infinity of them, the final destination cannot be reached.

Does that help?

[Dissident Dan]

Yes, if you've ever studied Calculus, it would be more apparent to you.

The summation of a constanct divided by anything greater than -1 and less than 1 to the nth power is always a finite number, even when n goes to infinity.

[sum]1/xn= c, when -1 < x < 1, regardless of bounds

This can be verified by comparing the integration of such a term from a finite number to infinity, because the integratin can be used as an upper bound for the summation.
for example,

[inte]1/2x = -1/((ln2)2x

so the integration of that from 1 to infinity is

0 - (-1/((ln2)2) = 1/((ln2)2)

[wuliheron]

Yeah, yeah, calculus suggests its not really a paradox. Philosophy suggests otherwise. I tried to keep it simple, but you asked for it. Zeno's paradox of motion is related to the Sorites Heap paradox.

http://plato.stanford.edu/entries/sorites-paradox/

This paradox and the Cretan Liar's paradox are both considered the most insoluable known. A central issue in the sorites paradox is vagueness.

http://plato.stanford.edu/entries/vagueness/#5

Something is vague if there are cases which do not fall clearly inside or outside the range of applicability of the term. That isn't to say vague words have no meaning. The word "heap" definitely has meaning, but its meaning is vague. Likewise the meaning of infinity is vague and it is debatable whether or not infinity is real.

[Tom Mattson]

OK, you're going to have to explain the connection between Sorites and Zeno. For one thing, I don't see the vagueness in Zeno's paradox. In fact, everything seems to be quite well defined.

As for the Cretan paradox, I don't see the vagueness there either, nor do I see the connection to Zeno. The Cretan paradox is an illustration of the breakdown of logic as a formal system, whereas Zeno attempted to prove the impossibility of motion. The former pertains to a mental construc (logic), while the latter pertains to something in the real world (motion).

[jammieg]

Here's another way of telling the story that takes into account Mentat's point of view:

A mathematician and an engineer were both standing 20 ft away from this pretty girl when they were asked by another Zeno guy that if they could only walk half the distance to the girl each time what would they do?
The mathematician exclaimed "Zeno, I will stand right here because I can conclusively prove that I'll never reach her", whereas the engineer said, "I agree but I can get close enough for practical purposes".

[wuliheron]

Originally posted by Tom
OK, you're going to have to explain the connection between Sorites and Zeno. For one thing, I don't see the vagueness in Zeno's paradox. In fact, everything seems to be quite well defined.

As for the Cretan paradox, I don't see the vagueness there either, nor do I see the connection to Zeno. The Cretan paradox is an illustration of the breakdown of logic as a formal system, whereas Zeno attempted to prove the impossibility of motion. The former pertains to a mental construc (logic), while the latter pertains to something in the real world (motion).

Actually, the Cretan Liar's paradox is not widely considered vague. I mentioned it here just to put both paradoxes in perspective. That's the irony of it, the two most respected paradoxes cover both the vague and the well defined.

Zeno's paradox is vague because the concept of infinity is vague just as the concept of a heap is vague. The concept of time isn't that well defined either.

[dr-dock]

if they both go with a constant speeds (V1 and V2) then:
dX1/V1=dt=dX2/V2 so if it was X1>X2 to become X2>X1 it has to be dX2>dX1 => dX2/dX1=V2/V1>1 => V2>V1 (it is enough).in fact it only seems like a paradox but it ain't cause as you shrenk dX you shrenk dt. at a infinite shrenking step you end up with 0/0=V=const.

just mantein your speed Achilles and you'll win.
wisdom is the might of the physically weaker.

[wuliheron]

Originally posted by dr-dock
if they both go with a constant speeds (V1 and V2) then:
dX1/V1=dt=dX2/V2 so if it was X1>X2 to become X2>X1 it has to be dX2>dX1 => dX2/dX1=V2/V1>1 => V2>V1 (it is enough).in fact it only seems like a paradox but it ain't cause as you shrenk dX you shrenk dt. at a infinite shrenking step you end up with 0/0=V=const.

just mantein your speed Achilles and you'll win.
wisdom is the might of the physically weaker.

He'll win at the end of eternity, what a paradox.

[Dissident Dan]

The thing to remember in Zeno's paradox is that if he continues at a constant speed, as the distance travelled halves, so does the time. So, with continual halving, the distance approaches 0, and so does the elapsed time. But time keeps on a'going...

[heusdens]

The essential problem, highlighted by Zeno’s paradoxes, is the inability of formal logic to grasp movement. Zeno’s paradox of the Arrow takes as an example of movement the parabola traced by an arrow in flight. At any given point in this trajectory, the arrow is considered to be still. But since, by definition, a line consists of a series of points, at each of which the arrow is still, movement is an illusion. The answer to this paradox was given by Hegel.

The notion of movement necessarily involves a contradiction. Consider the movement of a body, Zeno’s arrow for example, from one point to another. When it starts to move, it is no longer at point A. At the same time, it is not yet at point B. Where is it, then? To say that it is "in the middle" conveys nothing, for then it would still be at a point, and therefore at rest. "But," says Hegel, "movement means to be in this place and not to be in it, and thus to be in both alike; and this is the continuity of space and time which first makes motion possible." (Hegel, op. cit., Vol. 1, p. 273.) As Aristotle shrewdly observed, "It arises from the fact that it is taken for granted that time consists of the Now; for if this is not conceded, the conclusions will not follow." But what is this "now"? If we say the arrow is "here," "now," it has already gone.

Engels writes:

"Motion itself is a contradiction: even simple mechanical change of place can only come about through a body being both in one place and in another place at one and the same moment of time, being in one and the same place and also not in it. And the continual assertion and simultaneous solution of this contradiction is precisely what motion is." (Engels, Anti-Duhring, p. 152.)

[Lifegazer]

Originally posted by wuliheron
He'll win at the end of eternity, what a paradox.
No... he will win at the end of time/change. Which doesn't signify the end of existence.

[heusdens]

Originally posted by Lifegazer
No... he will win at the end of time/change. Which doesn't signify the end of existence.

Which in other words is infinity, but anyway that is not the answer, since the paradox is only a trick of the mind, and not a real paradox (since movement does occur).

[drag]

O.K. I believe that one is covered already. [;)]
What's next Mentat ?

Live long and prosper.

[DrChinese]

Zeno's Paradox is successful because it seems so reasonable.

When Einstein first published on Special Relativity, it was rejected by many classicists because the Newtonian model was so reasonable. Similarly, QM lacks some "reasonable" elements ("God does not play dice") and even today scientists still seek to restore the determinism implied by putative undiscovered hidden variables.

Science provides us with the means to compare one theory with another. Zeno's theory failed, and he knew it was completely wrong when it was proposed! He simply didn't understand how to make sense of an argument that appears so reasonable, yet is utterly wrong.

[Adam]

The reason it is NOT a paradox, and the reason it is basically not worth discussing, and the reason why Zeno was a dumb-arse, is because it relies on a faulty assumption. Ie. it relies on the premise that we travel some fraction (half, quarter, whatever) of the remaining distance, when in fact we travel a certain amount regardless of what the remaining distance is.

To clarify:

Zeno assumes that you are going 1000 metres. In a step you go 500 metres. next step 250 metres, then 125, and so on.

In reality, if you are travelling 1000 metres or 5000 metres, you will take steps of, for example, one metre, then another metre, then another metre, and so on.

Zeno's paradox only exists if you are dumb enough to consider the possibility that you would be stupid enough to reduce the size of your steps constantly.

You might say "Well, it's supposed to be more abstract than that". Whoopey-doo. Either you step 500 metres then step another 500 metres, or you do the Zeno Shuffle and take ever-shortening steps for no real purpose.

There's no actual paradox going on. It's very simple: if you choose to continually divide any number by anything other than 1, you get a fraction.

[wuliheron]

Originally posted by DrChinese
Zeno's Paradox is successful because it seems so reasonable.

When Einstein first published on Special Relativity, it was rejected by many classicists because the Newtonian model was so reasonable. Similarly, QM lacks some "reasonable" elements ("God does not play dice") and even today scientists still seek to restore the determinism implied by putative undiscovered hidden variables.

Science provides us with the means to compare one theory with another. Zeno's theory failed, and he knew it was completely wrong when it was proposed! He simply didn't understand how to make sense of an argument that appears so reasonable, yet is utterly wrong.

How do you know Zeno believed he was wrong when he proposed motion was impossible? He asserted that the universe is indivisible, eternal, immortal, and unchanging. Today, string theory proposes all distances are really the same one short distance. Who knows, maybe Zeno will have the last laugh after all. :0)

[Lifegazer]

Originally posted by Tom
Zeno's mistake is in assuming that an infinite number of steps cannot be done in a finite amount of time. In other words, he tacitly assumes that it would require an infinite amount of time, and so could never be done.

Is that true? Let's see.

T=L/v=(1/v)&Sigma;n=0oo(1/2)n

The series on the right is a geometric series. In order for Zeno's argument to hold up, it would have to blow up to infinity--but it actually converges to 1.

But does it actually converge to '1'?
At what point does "Distance=L/2+L/4+L/8+..." converge to 'L'?

The length is singular. And the time to traverse it is also singular. It's not really surprising to see that '1' is at the heart of the debate. Zeno may have implied that the time to traverse a given length would be infinite. But what he means here is that the time to traverse a given-length cannot become singular in itself. I.e., that the oneness (completeness) of time to traverse a given singular-length cannot be achieved.
I think he was really arguing (or he should have been arguing) that the time to traverse a given length can never become complete - and that therefore, time does not converge to a singular value. I.e., does not converge to '1' (which is the symbol of completeness, in this case).

The flaw in Zeno's argument is in assuming the divergence of a series that actually converges.
That may well be a flaw. But I only find it to be a grammatical flaw.
The question remains whether the convergence to '1' can be achieved. If it cannot, then the underlying issue is still open to debate.

[Lifegazer]

Originally posted by DrChinese
Zeno's theory failed, and he knew it was completely wrong when it was proposed! He simply didn't understand how to make sense of an argument that appears so reasonable, yet is utterly wrong.

He knew it was wrong, because...? Because he could see that motion was taking place? That just begs the question about perception being internal, or external.

[ahrkron]

Originally posted by Lifegazer
He knew it was wrong, because...? Because he could see that motion was taking place? That just begs the question about perception being internal, or external.

I don't know about Zeno, but we know it is wrong because the argument is applied to whatever it is we call "motion" (be it internal, external or mixed), and it would imply that we would not even perceive it, which is evidently false.

[Lifegazer]

Originally posted by ahrkron
I don't know about Zeno, but we know it is wrong because the argument is applied to whatever it is we call "motion" (be it internal, external or mixed), and it would imply that we would not even perceive it, which is evidently false.
The thing with internal-motion, is that it is conceptual. You don't really walk-around in your dreams, for example. It just appears that way. But it's not real motion.
Zeno's paradox fundamentally asks whether any form of perceived motion can be 'real'... or whether it's all conceptual.

[ahrkron]

Originally posted by Lifegazer
The thing with internal-motion, is that it is conceptual. You don't really walk-around in your dreams, for example. It just appears that way. But it's not real motion.

That is entirely irrelevant for Zeno's argument. Even in your dreams, in order to go to a different point, you need to have the perception of having passed through the intermediate points. You may argue otherwise in the case of dreams, but in the realm of perceptions, it is clearly the case.

Even if all reality was "in the Mind", Zeno's arguments can be equally applied. They do not tell anything about what is "behind perceptions", but only about our description of motion, and our assumptions about infinite decomposition.

[Lifegazer]

Originally posted by ahrkron
That is entirely irrelevant for Zeno's argument. Even in your dreams, in order to go to a different point, you need to have the perception of having passed through the intermediate points.

Zeno's paradox asks the reader - even indirectly - to ponder the nature of reality. If motion (in an external reality) doesn't make sense, then one is forced to ponder the possibility that all motion is conceptual (in the mind). Of course, it may or may not be possible to show why Zeno's reasoning is incorrect. But I've never seen an argument to convince me that this is the case. Conceptual mathematics doesn't always apply to tangible (finite) reality. Especially when the term "infinite" is being used.

You may argue otherwise in the case of dreams, but in the realm of perceptions, it is clearly the case.

'Dreams' are evidence that motion can ~appear~ to occur where no motion has occured. But as for our concious perceptions, the discussion is still open to debate, as I see it.

Even if all reality was "in the Mind", Zeno's arguments can be equally applied.

But if motion was really a figment of the Mind's ability to fool itself somehow, then Zeno's arguments do make sense. It's when we apply Zeno's arguments to external-reality where the problems seem to arise.

[Tom Mattson]

Originally posted by Lifegazer
But does it actually converge to '1'?


Yes. I wouldn't have said it does if it does not.


That may well be a flaw. But I only find it to be a grammatical flaw.
The question remains whether the convergence to '1' can be achieved. If it cannot, then the underlying issue is still open to debate.

Grammatical flaw?! The flaw is mathematical, and it has been settled for quite some time.

[Lifegazer]

Originally posted by Tom
Yes. I wouldn't have said it does if it does not.

Will you show us how? And can you do this without getting too fancy with the math?

[Tom Mattson]

Originally posted by Lifegazer
Of course, it may or may not be possible to show why Zeno's reasoning is incorrect.


We do know exactly why his reasoning is incorrect. It is because he assumed the divergence of an infinite series that actually converges.


But I've never seen an argument to convince me that this is the case. Conceptual mathematics doesn't always apply to tangible (finite) reality.


Then why listen to Zeno? He's the one who tried to show that motion is impossible using mathematics. You are willing to accept Zeno's use of "conceptual mathematics" with a glaring mistake and reject "conceptual mathematics" done correctly just because it supports your beliefs.

That makes no sense whatsoever.

[Tom Mattson]

Originally posted by Lifegazer
Will you show us how? And can you do this without getting too fancy with the math?

You and I interacted in 2 "Zeno" threads in PF v2.0, and I showed you how then. Rather than type it out again, I am going to refer you to this website:

http://mathworld.wolfram.com/GeometricSeries.html

Let r=1/2, and you've got Zeno's series.

[ahrkron]

Originally posted by Lifegazer
But if motion was really a figment of the Mind's ability to fool itself somehow, then Zeno's arguments do make sense. It's when we apply Zeno's arguments to external-reality where the problems seem to arise.

I think you did not get my point at all.

What I'm saying is that Zeno's arguments also apply to your theory, in which motion is just a projection within the Mind.

This being the case, it is clear that Zeno's paradox has no saying on whether motion is a projection within the Mind or an aspect of reality.

This is just natural, since the paradox does not contend with the nature of reality, but with the description of motion and infinite aggregates.

[Lifegazer]

Originally posted by Tom
We do know exactly why his reasoning is incorrect. It is because he assumed the divergence of an infinite series that actually converges.

Yes... you've shown that it converges towards '1'. But you didn't explain why '1' is ever reached. That's why I asked at what point does "Distance=L/2+L/4+L/8+..." converge to 'L'? And even if Zeno is wrong with the terms which he uses, the fundamental-issue of real-motion is not resolved unless it can be shown how this happens. Because I don't understand how it can, to be honest. Not tangibly, anyway.

Then why listen to Zeno? He's the one who tried to show that motion is impossible using mathematics.

I happen to agree with his conclusion, even if he did make what I consider to be an error of language. I tried explaining why in my previous post to you.
"The length is singular. And the time to traverse it is also singular. It's not really surprising to see that '1' is at the heart of the debate. Zeno may have implied that the time to traverse a given length would be infinite. But what he means here is that the time to traverse a given-length cannot become singular in itself. I.e., that the oneness (completeness) of time to traverse a given singular-length cannot be achieved. [added note: basically, what he's saying is that it would take an eternity to achieve completeness/singularity of the given-length, if travelling in a manner which mirrors "L/2+L/4+L/8+...".]
I think he was really arguing (or he should have been arguing) that the time to traverse a given length can never become complete - and that therefore, time does not converge to a singular value. I.e., does not converge to '1' (which is the symbol of completeness, in this case)."
If it takes an eternity to converge towards '1', then '1' is not grasped.

You are willing to accept Zeno's use of "conceptual mathematics" with a glaring mistake and reject "conceptual mathematics" done correctly just because it supports your beliefs.

It is Zeno's use of language which is the issue. His 'paradox' can equally be applied to the eternal-convergence of singularity.

That makes no sense whatsoever.

I have no doubts that present-day mathematics are more advanced than in Zeno's day. But that's not the issue. The issue is whether those mathematics are conceptual, or whether they also reflect a tangible-reality (to which they are being applied). I think the issue is one of reason, rather than of mathematics.

[Lifegazer]

Originally posted by ahrkron
What I'm saying is that Zeno's arguments also apply to your theory, in which motion is just a projection within the Mind.

Misunderstood you. Sorry.
However now that I understand your point, I have to disagree with it anyway. For Zeno's arguments are irrelevant to a Mind-reality. Such a reality is a physical-singularity. Motion doesn't really occur. And since Zeno's paradox seems to question the actuality of motion, my hypothesis fits in nicely with this challenge to real-motion. The motion of an observer, within his own mind (full of sensations), is the motion of the mind itself... within itself. It is a shift of perception which yields the appearance of motion - within the mind. The mind doesn't really cross lengths. It changes its perspective of that length, thus yielding the perception of motion. But the mind moves nowhere. Only sensations are changed.

[Mentat]

Alright, I'd say that that particular paradox is pretty well covered. My thanks to everyone, especially those who explained it using math. I got up to basic Calculus, so I got the meaning out of the equations (possibly easier than I would have gotten it, if someone had tried to explain it in words - rather, it was much more solid/believable, when seen from a mathematical stand-point).

For some reason, I can't think of another of Zeno's paradoxes, at the present moment. I'll try and think of another one - I know I had some in mind, when I posted the thread. If anyone else can think of one to discuss, I'd be happy to discuss that one also.

[Tom Mattson]

Originally posted by Lifegazer
Yes... you've shown that it converges towards '1'. But you didn't explain why '1' is ever reached. That's why I asked at what point does "Distance=L/2+L/4+L/8+..." converge to 'L'?


The link I gave you explains how the series converges. As for "at what point" does it converge, I don't know what you mean.


"The length is singular. And the time to traverse it is also singular. It's not really surprising to see that '1' is at the heart of the debate. Zeno may have implied that the time to traverse a given length would be infinite. But what he means here is that the time to traverse a given-length cannot become singular in itself.


What do you mean by the last sentence? I know what Zeno meant, and it has nothing to do with 'singular', it has to do with 'infinite' (as in: "It will take an infinite amount of time to cross any distance").


I.e., that the oneness (completeness) of time to traverse a given singular-length cannot be achieved. [added note: basically, what he's saying is that it would take an eternity to achieve completeness/singularity of the given-length, if travelling in a manner which mirrors "L/2+L/4+L/8+...".]


What is "oneness(completeness) of time"? What is "completeness/singularity of the given-length"?


I think he was really arguing (or he should have been arguing) that the time to traverse a given length can never become complete - and that therefore, time does not converge to a singular value. I.e., does not converge to '1' (which is the symbol of completeness, in this case)."
If it takes an eternity to converge towards '1', then '1' is not grasped.


Sure, that is what he was arguing. Basically it goes like this:

1. If it takes an eternity to traverse a distance L, then that distance cannot be traversed.
2. It takes an eternity to traverse a distance L.
3. Therefore, that distance cannot be traversed.

But Premise 2 is false.


It is Zeno's use of language which is the issue. His 'paradox' can equally be applied to the eternal-convergence of singularity.


No, it is not his use of language. It is his mathematical error which is the issue.


I have no doubts that present-day mathematics are more advanced than in Zeno's day. But that's not the issue. The issue is whether those mathematics are conceptual, or whether they also reflect a tangible-reality (to which they are being applied). I think the issue is one of reason, rather than of mathematics.

It is an issue of mathematics because that is how Zeno defined the problem from the start. Just read any account of the paradox, and you will see it.

[Tom Mattson]

Originally posted by Mentat
For some reason, I can't think of another of Zeno's paradoxes, at the present moment.

Oooh, I t'ought you'd neva ask. [a)]

http://plato.stanford.edu/entries/paradox-zeno

[Mentat]

Originally posted by Tom
Oooh, I t'ought you'd neva ask. [a)]

http://plato.stanford.edu/entries/paradox-zeno

I'd never heard of the "Plurality Paradox". It seems like utter nonsense to me (no offense to anyone who agrees with Zeno on this).

Would anyone like to try and defend it?

[Lifegazer]

Originally posted by Tom
The link I gave you explains how the series converges. As for "at what point" does it converge, I don't know what you mean.

I'm not a mathematician, as you know. I was hoping you'd give a narrative of those math and explain what they say, in language. And I know we've spoken about it last year. But I honestly can't remember what your explanation was. But I do remember that I saw a problem with the tangibility of those math. I.e., I doubted that they could be applied to a tangible-reality (with real motion). This might not be important to you, but whether reality is 'tangible' (as opposed to conceptual... mind-ful) is the underlying issue raised by Zeno's paradox. And so I consider such a question to be worthy of discussion.

You say that Zeno was wrong because he dealt with the divergence of a series, as opposed to the convergence of a series. But the same 'paradox' exists with both possibilities. So it's not even relevant that he should make this error. The question still remains:-
How does "Distance=L/2+L/4+L/8+..." , converge to 'L'?
Or; how can there be an eternal progression towards '1', whereby '1' is finally yielded? Does this signify the end of eternity? Paradox abounds and Wuli should be all over you like a rash, at any minute.

What do you mean by the last sentence? I know what Zeno meant, and it has nothing to do with 'singular', it has to do with 'infinite' (as in: "It will take an infinite amount of time to cross any distance").

Again, it's not really relevant as to whether we deal with a diverging-series, or a converging-series. But you don't seem to grasp that "It will take an infinite amount of time to cross any distance"; can also be stated thus: It will take an eternity to converge towards any point (singularity). Or; it will take an eternity to converge towards '1'.
Zeno isn't really saying anything which contradicts a convergence towards '1'. I think he's been misread.

Sure, that is what he was arguing. Basically it goes like this:

1. If it takes an eternity to traverse a distance L, then that distance cannot be traversed.
2. It takes an eternity to traverse a distance L.
3. Therefore, that distance cannot be traversed.

But Premise 2 is false.

Given "Distance=L/2+L/4+L/8+..." , is a series that goes on forever, I do not see how a such a series can come to a convergence (an end) at 'L' (or '1'). If it comes to an end, then that series is not going-on forever. So how does mathematics overcome this problem?

It is an issue of mathematics because that is how Zeno defined the problem from the start. Just read any account of the paradox, and you will see it.

It is actually a discussion about concepts (motion; length; time.). Any mathematics which deals with these concepts, must obviously conform to the reasoning which distinguishes between 'tangible' and 'conceptual'. Because, if mathematicians trust the reason which has formulated math, then mathematicians should also take notice of any reason which makes those aforementioned distinctions.
Any philosophy which seeks to discredit Zeno, cannot do so merely with mathematics. For Zeno does not ask how mathematics manages to converge towards '1', conceptually. Zeno asks how tangible-things can achieve such events. And so, an argument of reason is required to discredit Zeno. Mathematics, when dealing with concepts such as 'infinity', has to take-note of the fact that 'infinity' is an intangible-concept.

[Tom Mattson]

Originally posted by Lifegazer
I'm not a mathematician, as you know. I was hoping you'd give a narrative of those math and explain what they say, in language.


I don't expect you to be a mathematician. That's why I presented a link that uses only high school math. I can't explain how to sum a series "in language".


But I do remember that I saw a problem with the tangibility of those math. I.e., I doubted that they could be applied to a tangible-reality (with real motion). This might not be important to you, but whether reality is 'tangible' (as opposed to conceptual... mind-ful) is the underlying issue raised by Zeno's paradox. And so I consider such a question to be worthy of discussion.


You still don't get it: Zeno is the one who brought the math into it. Any problems you have with the 'tangibility' of math, and you'll have to take it up with Zeno. I'm only telling you why he's wrong.


You say that Zeno was wrong because he dealt with the divergence of a series, as opposed to the convergence of a series. But the same 'paradox' exists with both possibilities. So it's not even relevant that he should make this error.


I don't know what you're thinking, but the paradox disappears completely if you correct the mistake.


The question still remains:-
How does "Distance=L/2+L/4+L/8+..." , converge to 'L'?


As I said, the link explains it. Ask me again, and I'll tell ya the same.

Originally posted by Lifegazer
Again, it's not really relevant as to whether we deal with a diverging-series, or a converging-series.


Of course it is--Zeno relies on the divergence of the series to say what you are about to say...


But you don't seem to grasp that "It will take an infinite amount of time to cross any distance"; can also be stated thus: It will take an eternity to converge towards any point (singularity). Or; it will take an eternity to converge towards '1'.


...and of course, it won't take an eternity. The series I gave you is the time that it will take.


Zeno isn't really saying anything which contradicts a convergence towards '1'. I think he's been misread.


Certainly by you, it seems, because the infinite series is part of the problem, and he gets it wrong.


Given "Distance=L/2+L/4+L/8+..." , is a series that goes on forever, I do not see how a such a series can come to a convergence (an end) at 'L' (or '1'). If it comes to an end, then that series is not going-on forever. So how does mathematics overcome this problem?


It does converge, and the link explains why.


It is actually a discussion about concepts (motion; length; time.). Any mathematics which deals with these concepts, must obviously conform to the reasoning which distinguishes between 'tangible' and 'conceptual'. Because, if mathematicians trust the reason which has formulated math, then mathematicians should also take notice of any reason which makes those aforementioned distinctions.


No--really--it is a discussion about mathematics. Just read the paradox on any one of a zillion webpages.


Any philosophy which seeks to discredit Zeno, cannot do so merely with mathematics.


Of course it can, because Zeno brought it into the arena of mathematics. Again, just read the paradox.


For Zeno does not ask how mathematics manages to converge towards '1', conceptually.


Of course he doesn't ask how the series converges--He asserts that it diverges. Again, just read the paradox.

You've obviously got some studying to do on this issue. Read the paradox, see where Zeno puts the infinite series into it, and see where he gets it wrong. It's not that difficult.

[Lifegazer]

Originally posted by Tom
...and of course, it won't take an eternity. The series I gave you is the time that it will take.

Does L/2 + L/4 + L/8 + L/16 + L/32... ad-infinitum... converge to 'L'?
And if the above series is considered to be infinite, then how can it ever stop at 'L'?

An infinite-convergence (towards 'L' or '1') cannot stop - simply by definition. The fact that it stops means that it isn't an infinite-series.
There's more to this than math. But if you're not interested, then never mind.

[Tom Mattson]

Originally posted by Lifegazer
Does L/2 + L/4 + L/8 + L/16 + L/32... ad-infinitum... converge to 'L'?


Yes

You can stop asking me the same question. Trust me, I'm not going to change my answer.


And if the above series is considered to be infinite, then how can it ever stop at 'L'?


The "how" is in the link I gave you. All the deductions are there.


An infinite-convergence (towards 'L' or '1') cannot stop - simply by definition. The fact that it stops means that it isn't an infinite-series.
There's more to this than math. But if you're not interested, then never mind.

No, there really isn't more to it than math. Again, read the paradox. I can't stress that enough. The solution is found in the calculus of infinite series. If you can't be bothered taking it upon yourself to read the problem and learn the math that solves it, then why bother with these discussions?

[Lifegazer]

Originally posted by Tom
No, there really isn't more to it than math. Again, read the paradox. I can't stress that enough. The solution is found in the calculus of infinite series. If you can't be bothered taking it upon yourself to read the problem and learn the math that solves it, then why bother with these discussions?
I consider the discussion to be one of reason. Fundamentally, the discussion is about the nature of reality, and discusses the possible 'substance' of particular concepts. Whether they can exist as tangible-entities, outside of perception.
You don't seem to want to debate any issue concerned along these lines. Fair enough. But to think that all such matters are solved because 'mathematics' (which is conceptual) can make an infinite-series come to a stop, is an incorrect attitude, imo.
I could probably come to understand the mathematics you pointed-out. But after I came to understand these mathematics, I would make the exact-same points I've been making all along. I do not contend that the mathematics are wrong. I contend that they don't make sense in relation to existence. A series which is 'infinite', by definition, simply cannot stop.

[Tom Mattson]

Originally posted by Lifegazer
I consider the discussion to be one of reason. Fundamentally, the discussion is about the nature of reality, and discusses the possible 'substance' of particular concepts. Whether they can exist as tangible-entities, outside of perception.


Everyone involved--you, me, Zeno--considers the discussion to be one of reason. The question is, "How did Zeno reason his argument, and where did he go wrong?"


You don't seem to want to debate any issue concerned along these lines. Fair enough. But to think that all such matters are solved because 'mathematics' (which is conceptual) can make an infinite-series come to a stop, is an incorrect attitude, imo.


First, I never said that "all such matters" were solved with mathematics. I said that Zeno's paradox was solved with mathematics, and that is because Zeno based his argument on mathematics. Again, you would know that if you had read the problem.

Second, the infinite series does not "come to a stop". It converges, meaning that all its terms add up to a finite number.


I could probably come to understand the mathematics you pointed-out. But after I came to understand these mathematics, I would make the exact-same points I've been making all along.


I doubt it. For one thing, you would not be making the point that it takes an eternity to traverse a finite length at constant speed. That is precisely where Zeno went wrong.


I do not contend that the mathematics are wrong. I contend that they don't make sense in relation to existence.


Well then tell Zeno! I am only analyzing his argument.


A series which is 'infinite', by definition, simply cannot stop.

And it doesn't. It's just that the infinite number of parts add up to a finite number. I know what your next question is going to be:

"But how...?"

The "how" is contained in the link I gave you. If you go through it--and understand it--you will see that some infinite series can be summed, despite the fact that they do not "stop".

[Dissident Dan]

In other words, you can keep adding up 1/2n all day long, but you will never get past 1. If you feel really bored, try it...

[ahrkron]

Originally posted by Lifegazer
The motion of an observer, within his own mind (full of sensations), is the motion of the mind itself... within itself. It is a shift of perception which yields the appearance of motion - within the mind. The mind doesn't really cross lengths. It changes its perspective of that length, thus yielding the perception of motion. But the mind moves nowhere. Only sensations are changed.

Phrase it as you will. The fact is, the perspective/perception/appearance or anything you want to use for the description, gives as good a basis for the paradox as realism.

For instance:

In order for the mind to "change perspective", it needs to do it in a way that (according to its own perspective) sweeps the intermediate perspective-states.

In order for it to "change sensations" from here to 1m, it first has to "change perspectives" up to 0.5m, and then to half that "perspective", and then half that.

i.e., if you don't accept that an infinite sum can converge to a finite number, then you have to accept that even in your mind, motion cannot be completed ever.

In any case, you can see that Zeno's argument does not favor either view (with or without the "Mind").

[Raavin]

Second, the infinite series does not "come to a stop". It converges, meaning that all its terms add up to a finite number.

I'm no mathematician but I don't think that's strictly true. The infinite series sums to what is, to all intents and purposes, a finite number given that .9999999....... is equal to 1.

Taking Uncertainty into account, the 'smearing' of space time as one approaches infinitesimal quantities might logically translate to numbers in that any conceptualy finite number n, is in 'reality' or practical use, n+-1/[oo]. The problem being that using this concept, 1 is not a strictly finite number. If there was a symbol for 'infinitesimal' that would be better.

Applying this to Zeno, in the case of Achilles, depending on what infinitesimal amount short of the total distance is deemed to be equal to the distance, he reaches the finish line long before a infinite amount of time has passed. In the case of the arrow, it always in motion an never stationary.

Raavin [:((]

my head hurts

[Lifegazer]

Originally posted by ahrkron
In order for it to "change sensations" from here to 1m, it first has to "change perspectives" up to 0.5m, and then to half that "perspective", and then half that.

i.e., if you don't accept that an infinite sum can converge to a finite number, then you have to accept that even in your mind, motion cannot be completed ever.

In any case, you can see that Zeno's argument does not favor either view (with or without the "Mind").
If the mind changes perception like the frames of a movie (incrementally, rather than smoothly), then would motion be achieved without such considerations?

[heusdens]

Originally posted by Lifegazer
If the mind changes perception like the frames of a movie (incrementally, rather than smoothly), then would motion be achieved without such considerations?

You may never believe it, but motion occurs in nature without any need for perception of it. One doesn't need a mind to have motion occur in nature.

[wuliheron]

Originally posted by heusdens
You may never believe it, but motion occurs in nature without any need for perception of it. One doesn't need a mind to have motion occur in nature.

To assert either position is pointless imo. Might as well argue how many angels can dance on the head of a pin. The same goes for infinity and time. We perceive what we perceive and that perception is consistent enough that we can make productive use of it or waste our time with silly debates.

[Mentat]

Alright people, let's move on. I think Tom's link provides a clear enough explanation.

Are there any of Zeno's paradoxes that are not considered to be resolved?

[Tom Mattson]

Originally posted by Mentat
Are there any of Zeno's paradoxes that are not considered to be resolved?

I'm sure you are aware of this by now, but that depends on who you ask! Let's just go through the paradoxes and check them out for ourselves.

Earlier, Heusdens brought up The Arrow. Let's go through that one next.

[Mentat]

Originally posted by Tom
I'm sure you are aware of this by now, but that depends on who you ask! Let's just go through the paradoxes and check them out for ourselves.

Earlier, Heusdens brought up The Arrow. Let's go through that one next.

Alright. What does that one postulate?

[Tom Mattson]

http://plato.stanford.edu/entries/paradox-zeno

From Section 3.3 of the above document:

3.3 The Arrow
The third is … that the flying arrow is at rest, which result follows from the assumption that time is composed of moments … . he says that if everything when it occupies an equal space is at rest, and if that which is in locomotion is always in a now, the flying arrow is therefore motionless. (Aristotle Physics, 239b.30)
Zeno abolishes motion, saying "What is in motion moves neither in the place it is nor in one in which it is not". (Diogenes Laertius Lives of Famous Philosophers, ix.72)

edit-
Here's another page on the subject.
http://faculty.washington.edu/smcohen/320/ZenoArrow.html

[BoulderHead]

Originally posted by wuliheron
To assert either position is pointless imo. Might as well argue how many angels can dance on the head of a pin. The same goes for infinity and time. We perceive what we perceive and that perception is consistent enough that we can make productive use of it or waste our time with silly debates. I like that, Wu Li.

The third is … that the flying arrow is at rest, which result follows from the assumption that time is composed of moments … .You know, I'm just not sure what time is composed of, but I think this could get interesting.

[Lifegazer]

Originally posted by Tom
The third is … that the flying arrow is at rest, which result follows from the assumption that time is composed of moments … . he says that if everything when it occupies an equal space is at rest, and if that which is in locomotion is always in a now, the flying arrow is therefore motionless. (Aristotle Physics, 239b.30)
Zeno abolishes motion, saying "What is in motion moves neither in the place it is nor in one in which it is not".

And how does math resolve this one?

[Raavin]

We perceive what we perceive and that perception is consistent enough that we can make productive use of it or waste our time with silly debates.

I don't think it's silly at all. While these sorts of debates are time consuming, they give people the ability to nut out ideas and stretch creative thinking. That's applies to those people who don't just grab the answers off of other websites.

Looking at the arrow, my personal gut instinct tells me something like this....

If we apply uncertainty principle (non-mathematically), as the time period approaches or reaches zero (an instant), so the inability to determine precise location increases.

If we can determine the location precisely then the momentum becomes indeterminable and not necessarily zero. Inversely, if we measure the momentum precisely, then we must accept that it's precise position must be indeterminable.

Therefore the arrow cannot exist in one position in an instant of time simultaneously but rather exists over some interval in a vague position.

Raavin ;)

[Mentat]

Originally posted by Tom
http://plato.stanford.edu/entries/paradox-zeno

From Section 3.3 of the above document:

3.3 The Arrow
The third is … that the flying arrow is at rest, which result follows from the assumption that time is composed of moments … . he says that if everything when it occupies an equal space is at rest, and if that which is in locomotion is always in a now, the flying arrow is therefore motionless. (Aristotle Physics, 239b.30)
Zeno abolishes motion, saying "What is in motion moves neither in the place it is nor in one in which it is not". (Diogenes Laertius Lives of Famous Philosophers, ix.72)

edit-
Here's another page on the subject.
http://faculty.washington.edu/smcohen/320/ZenoArrow.html

*scoffs in utter derision* I am now of the opinion that Zeno came up with these "paradoxes" just to irritate people (just kidding).

Why didn't Zeno realize that things do not remain the "now"? If they did, he would have been wrestling dinosaurs, while baking in the molten lava that was the Earth.

[Tom Mattson]

OK, it goes something like this:

1. If the arrow occupies a space its own size, then it is at rest.
2. The arrow always occupies a space its own size.
3. Therefore, the arrow is always at rest.

As far as I can see, the error in this argument is that the first premise is false. It basically says that if you know the position of the arrow, you know its state of motion. But every student of Physics I knows that you have to specify both the initial position and the initial velocity to get the state, because motion is described by a 2nd order differential equation.

So, in order to conclude that motion is impossible, Zeno had to assume that motion is impossible!

[wuliheron]

Zeno's paradoxes all make extensive use of reductio ad absurdum. Formal logic had not been invented yet and his were all inductive arguments. Instead of attempting to prove motion was impossible or false, he was really attempting to show that the idea of motion was just as absurd as his own idea that nothing moved. Therefore the real issue on the table is not whether or not he proved motion is impossible, but did he prove it was equally absurd, illogical, irrational.....

[Tom Mattson]

Originally posted by wuliheron
Zeno's paradoxes all make extensive use of reductio ad absurdum.


For sure that's true of The Dichotomy, but I don't see how The Arrow is reductio ad absurdum.


Formal logic had not been invented yet and his were all inductive arguments.


It seems to me that they are all attempts at deductive arguments. The only problem with them is that they all use false premises. If Zeno were right about the infinite series or one parameter specifying a dynamical state, he would have two sound deductive arguments here!

[wuliheron]

Originally posted by Tom

For sure that's true of The Dichotomy, but I don't see how The Arrow is reductio ad absurdum.


Zeno's argument revolves around the concept of infinitely divisible space and an "instant" in time which is not divisible by definition. Hence the paradox of our ordinary perception of time. He was pointing out that people tacitly accept some things are infinitely divisible while others are not.

Can you have half a human being, a half pregnent woman, etc? Why should space be infinitely divisible and not time? On the other hand, if you accept that nothing is infinitely divisible it leads to an equally absurd paradox, motion is impossible.

It seems to me that they are all attempts at deductive arguments. The only problem with them is that they all use false premises. If Zeno were right about the infinite series or one parameter specifying a dynamical state, he would have two sound deductive arguments here!


Nah, his style of absurity was the common fare among ancient Greeks at the time for entertainment purposes as much as anything else. Another more pointed purpose was political and religious. Criticism of the established faith and political leaders was punishable by death. A way around this was to create "puzzles" which did not directly criticize religion and politics, but humorously pointed out the absurdity of the situation as indirectly as possible.

[Lifegazer]

Originally posted by Tom
But every student of Physics I knows that you have to specify both the initial position and the initial velocity to get the state, because motion is described by a 2nd order differential equation.

That just implies that nothing can exist unless it moves. As observed by the eye. But you cannot impose physical-law upon all existence. There is no solid argument of reason which can make that claim. So when you deconstruct Zeno's argument by-way of reason deducted via physics, your argument has little merit Tom.

Edit: I expect you to reply that the paradox is about 'matter', and that therefore your reason is valid. But your reason is actually about fundamental-matter (fundamental energy). You are discussing the base-energy of existence itself. And so, as mentioned above, your logic is invalid.

[Tom Mattson]

Lifegazer, you have a real knack for completely missing the point.

Let's look at what I wrote again:

1. If the arrow occupies a space its own size, then it is at rest.
2. The arrow always occupies a space its own size.
3. Therefore, the arrow is always at rest.

There is Zeno's argument. The first premise says that if the arrow has a location at some time, then it is at rest. In other words, he is saying that specifying x(t0) at some time logically implies that it is not moving. If we take the correct specification of a state, namely that one must specify both x(t0) and v(t0), then we see that Zeno tacitly assumes that v(t0)=0.

When the tacit assumption is recognized and inserted into the argument, we have "If an arrow is at a location and not moving, then it is not moving", which is trivial.

Originally posted by Lifegazer
That just implies that nothing can exist unless it moves.


Nothing I wrote implies that. You just pulled it out of the air.


As observed by the eye. But you cannot impose physical-law upon all existence. There is no solid argument of reason which can make that claim. So when you deconstruct Zeno's argument by-way of reason deducted via physical-laws, your argument has little merit Tom.

Again, you completely misunderstand both me and Zeno. Zeno is starting from what he believes are physical laws. He just got it wrong is all.


Edit: I expect you to reply that the paradox is about 'matter', and that therefore your reason is valid. But your reason is actually about fundamental-matter (fundamental energy). You are discussing the base-energy of existence itself. And so, as mentioned above, your logic is invalid.


There is nothing in either Zeno's argument or my argument about "fundamental energy" or "existence". You are seeing something that is not there.

[Lifegazer]

Originally posted by Tom
When the tacit assumption is recognized and inserted into the argument, we have "If an arrow is at a location and not moving, then it is not moving", which is trivial.

I disagree with this. Zeno says more than this. He also says the arrow cannot exist in any other state (premise 2). Therefore, the conclusion (premise 3), still seems to have validity.

There is nothing in either Zeno's argument or my argument about "fundamental energy" or "existence". You are seeing something that is not there.
Okay, I apologise for that. I thought you was hinting at QM.

[Tom Mattson]

Nope, no QM is necessary here.

Originally posted by Lifegazer
I disagree with this. Zeno says more than this. He also says the arrow cannot exist in any other state (premise 2). Therefore, the conclusion (premise 3), still seems to have validity.


Premise 2 only says that the arrow always has to have a location, which is true. However, that has no bearing on Premise 1, in which Zeno says that the position alone specifies the state. Premise 1 is false, and the argument is deductively valid, so we know that the conclusion is false.

[Tom Mattson]

Incidentally, it is said that Zeno's reason for forwarding Premise 1 is that, at any instant, there is no physical difference between a stationary arrow and a moving arrow. I don't see the logical connection there, but we now know that there is a physical difference: the moving arrow would be length contracted as per Special Relativity.

If SR were known at the time, would Zeno have offered this argument?
Did Zeno forsee SR?

Hmmm....

[wuliheron]

Originally posted by Tom
Incidentally, it is said that Zeno's reason for forwarding Premise 1 is that, at any instant, there is no physical difference between a stationary arrow and a moving arrow. I don't see the logical connection there, but we now know that there is a physical difference: the moving arrow would be length contracted as per Special Relativity.

If SR were known at the time, would Zeno have offered this argument?
Did Zeno forsee SR?

Hmmm....

He did in the sense that special relativity proposes an indivisible spacetime continuum, and Zeno believed everything was indivisible. Again, the argument is that having half a human being or a half pregnent woman or whatever is impossible. The alternative which he makes fun of in his paradoxes is that everything is infinitely divisible and, at that point, the Sorites heap paradox kicks in.

[ahrkron]

Originally posted by Tom
[...]Zeno's reason for forwarding Premise 1 is that, at any instant, there is no physical difference between a stationary arrow and a moving arrow. I don't see the logical connection there, but we now know that there is a physical difference: the moving arrow would be length contracted as per Special Relativity.

If SR were known at the time, would Zeno have offered this argument?
Did Zeno forsee SR?

I don't see the connection either, but if there is one, we can also ask the question in a slightly different way: would motion be possible in a universe with no length contraction?

This reminds me of the fact that Poincare was extremely close to the gist of SR. He even mentioned that there is no experimental backup for the idea that simultaneity is absolute (which is closely related to length contraction).

Of course, Poincare had the context of Maxwell equations and the struggle to interpret the "Lorentz-Fitzgerald contraction", but anyway, it strikes me as impressive that he made the connection, and the sole idea that Zeno may have glanced at it so long ago is just mind-boggling.

[heusdens]

Originally posted by Tom
Incidentally, it is said that Zeno's reason for forwarding Premise 1 is that, at any instant, there is no physical difference between a stationary arrow and a moving arrow. I don't see the logical connection there, but we now know that there is a physical difference: the moving arrow would be length contracted as per Special Relativity.

If SR were known at the time, would Zeno have offered this argument?
Did Zeno forsee SR?

In SR we would just state that the arrow, in it's own space-time frame is at rest. It shows to be moving, according to a different space-time frame, and also is lenght contracted and has a little more mass. These are observational things though. As seen from the arrow itself, physical properties don't change.

[heusdens]

Originally posted by ahrkron
[B]I don't see the connection either, but if there is one, we can also ask the question in a slightly different way: would motion be possible in a universe with no length contraction? [/b/]

This is a weird interpretation, you better focus on the causes of length contraction and other relativistic phenomena, which are of course a consequence of the speed of light.
We could state it differently, what if the speed of light were infinite? Then every measurement would be instantaniously, since no time elapse between the happening of the event and the observation of it from a distant. Hence, no lenght contraction or any other relativistic phenomena would occur.

I would reformulate this then as:

Suppose the light speed would be infinite, would there still be motion possible?

What would the universe look like if the speed of light were infinite?


But let us look at the problem again, the arrow in motion.
What is the difference between an arrow, that is in motion and one that is at rest (relative to some default intertial frame of reference that is).
Both arrows are at some point in time T at some point in space S.
Yet, the moving arrow is at a different point in space at a different time, and the arrow in rest, does not change it's point in space at a different time. So obviously, the arrows differ.

We have to be aware of the fact though that the moving arrow, did not start it's motion out of nothing, but it was accelerated due to some force. This force has transferred energy onto the arrow.
That makes the arrows physically different. The moving arrow carries kinetic energy, the arrow at rest not.

The speed of light in this experiment is of no theoretical consequence. Hence this would not be of any influence to the fact that one arrow is moving, and the other is at rest.

[heusdens]

Originally posted by Lifegazer
That just implies that nothing can exist unless it moves.

This is fairly true, there is no existence without motion or change.

But you cannot impose physical-law upon all existence

Since all existence is physical existence, it is obvious that all physical existence is subject to physical laws.

[Mentat]

Originally posted by Tom
OK, it goes something like this:

1. If the arrow occupies a space its own size, then it is at rest.
2. The arrow always occupies a space its own size.
3. Therefore, the arrow is always at rest.

As far as I can see, the error in this argument is that the first premise is false. It basically says that if you know the position of the arrow, you know its state of motion. But every student of Physics I knows that you have to specify both the initial position and the initial velocity to get the state, because motion is described by a 2nd order differential equation.

So, in order to conclude that motion is impossible, Zeno had to assume that motion is impossible!

Relativity also contradicts the first premise, doesn't it? In Relativistic reasoning, any frame of reference could be said to be "at rest".