# Not an exact brain teaser, but..

Tags: brain, exact, teaser
 P: 364 This was in a maths textbook. An arrow approaches its mark, (where its supposed to hit) but as it approaches closer and closer, it will approach half the distance it was at some time ago away from the target, and so on and so on and so on.. So im asking: Why does the arrow ever reach the target?
 PF Patron Sci Advisor Emeritus P: 16,094 Ask yourself this first: why wouldn't the arrow ever reach the target?
P: 364
 Quote by Hurkyl Ask yourself this first: why wouldn't the arrow ever reach the target?
Huh..? confused..

I don't understand what you mean. Forgive me if i am being an idiot of somewhat flavour..

To answer your question in a ridiculous, ambiguous, and idiotic way: the distance between the arrow is somewhat infinite..?

I've heard it reaches the target because it depends on dimentions..but i wasn't quite satisfied with that answer, so im asking here..

HW Helper
P: 11,717

## Not an exact brain teaser, but..

The arrow is one object,how do you define:"the distance between the arrow"...?

What dimensions are involved here...?

Daniel.
P: 364
 Quote by dextercioby The arrow is one object,how do you define:"the distance between the arrow"...? What dimensions are involved here...? Daniel.
I honestly don't know. I've just heard of answers of that kind, but by no means am i saying those are true.
 HW Helper Sci Advisor P: 11,717 Well,then do some recherche on the problem and then come with a "sound" version to us... Da
P: 364
 Quote by dextercioby Well,then do some recherche on the problem and then come with a "sound" version to us... Da
I presume you'll have to see evidence that i've put some effort into it?

Fair enough. I will try and reword the question, and put down my 'hypothesis'.
 HW Helper Sci Advisor P: 11,717 I mean to be stated very clear,just like a maths problem,not to leave room for interpretations or missunderstandings. Daniel.
 P: 34 Space is quantized so eventually it gets to the point where it can't go halfway any more and has to "make the leap"
 P: n/a Are you trying to tell us one of the Zeno's paradoxes? http://mathworld.wolfram.com/ZenosParadoxes.html
 HW Helper Sci Advisor P: 11,717 Yes,my guess is that is sounds very much like one of them.Anyway,let there be noted,that,up until now,the OP is not clear what he is trying to ask... Daniel.
P: 364
 Quote by Icebreaker Are you trying to tell us one of the Zeno's paradoxes? http://mathworld.wolfram.com/ZenosParadoxes.html
I didn't know it was Zeno's paradoxes. It was just in my mathematics textbook and interested me a lot.

 Space is quantized so eventually it gets to the point where it can't go halfway any more and has to "make the leap"
Thats the kind of answer i wanted, since (well now i know) the mathematics behind it seems complicated..

Let me try and make the question more accurate. (although it has already been answered)

Consider a archer firing his arrow to a target at a certain distance away, E. When he fires the arrow, the arrow will travel towards the target, until it reaches a distance of E/2, then E/4, then E/8 and so on.

Looking at this, the arrow shouldn't hit the target at all. However, we know this is not true, as we do actually see the arrow hitting the target.

So, what causes the arrow to hit the target?
 HW Helper P: 2,635 This is an ancient paradox, and one that was not satisfactorily resolved till the theory of limits was formalised. Ask yourself : Can the sum of an infinite series be finite ? Under what circumstances ? What does a constant velocity of the arrow mean ? What is the relationship of the distance travelled to the time taken to travel that distance ? Hence what is the time taken to travel each smaller "division" of the distance ? What is the total time taken ? I think you can answer your own question here.
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Emeritus
P: 16,094
 Space is quantized so eventually it gets to the point where it can't go halfway any more and has to "make the leap"
*sigh* There is absolutely no empirical evidence space is quantized. Not only is there no working model of the universe that includes quantized space, none of the popular alternatives (e.g. String Theory and Loop Quantum Gravity) feature quantized space.

 Looking at this, the arrow shouldn't hit thea target at all, since the distance is infinite.
You said the distance is E. Why do you now think it's infinite?

It is true that you have divided the problem into an infinite number of subtasks, the distance is still finite.
P: 364
 Quote by Hurkyl *sigh* There is absolutely no empirical evidence space is quantized. Not only is there no working model of the universe that includes quantized space, none of the popular alternatives (e.g. String Theory and Loop Quantum Gravity) feature quantized space. You said the distance is E. Why do you now think it's infinite? It is true that you have divided the problem into an infinite number of subtasks, the distance is still finite.
Forgive my idiocy. I'm not as familiar as you are on QM.

EDIT: 'infinite' removed.
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P: 2,635
 Quote by Bladibla Forgive my idiocy. I'm not as familiar as you are on QM.
Forget QM, this has nothing to do with QM (Quantum Mechanics). The poster who talked about spatial quantisation is wrong.

Just think of it as an infinite series problem. What conclusions can you draw ?
 P: 2,378 You can look at this another way too. If you are marking off the milestones then why should it even ever leave the starting point? It is never halfway to anything before it leaves the starting gate.
P: n/a
 Quote by Hurkyl *sigh* There is absolutely no empirical evidence space is quantized. Not only is there no working model of the universe that includes quantized space, none of the popular alternatives (e.g. String Theory and Loop Quantum Gravity) feature quantized space.
Should there be?

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