- #1
Deepak K Kapur
- 164
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Hi
Any line joining points A and B has infinite points.
So, when I move from A to B, do I cross infinity?
Any line joining points A and B has infinite points.
So, when I move from A to B, do I cross infinity?
No. You cross the finite distance between A and B.Deepak K Kapur said:Hi
So, when I move from A to B, do I cross infinity?
rumborak said:You cross an infinite number of infinitely small distances. They cancel out.
jtbell said:What exactly do you mean by "cross infinity"?
You do pass through an infinite number of points, but you also pass through a finite distance in a finite amount of time.Deepak K Kapur said:I mean do I travel an infinity of points when I move from A to B?
I think it's more commonly known as "Achilles and the tortoise." IIRC Aristotle wasn't much of an athlete.rumborak said:Zeno's paradox, that is "Aristotle and the tortoise".
rumborak said:I highly suggest you read the Wikipedia article on Zeno's paradox, that is "Aristotle and the tortoise". That's what you are asking here essentially.
Deepak K Kapur said:Space is continuous and therefore there are infinite points between A and B. If I move from A to B point by point, how can I ever reach B.
Drakkith said:Don't let the math confuse you. Points are mathematical objects that help us describe the universe. The fact that there are an infinite amount of points between A and B simply doesn't stop you from moving between A and B.
Deepak K Kapur said:1. It means math does not describe nature fully/accurately. If so what about all the equations of Physics that contain an awesome amount of math?
Deepak K Kapur said:2. What is it that stops any physical distance from being infinitely divided. If you say it's the plank's length, what is the reason for not being able to go beyond the plank's length?
Deepak K Kapur said:Please don't mind but your post seems to be faith oriented and not logic oriented...
There is no "sequence" of point to point moves that both touches all points in an interval and respects the natural ordering of the reals.CWatters said:If there are an infinite number of points then each is infinitely small. So if you move point-to-point you move infinitely slowly. So I'd say no you won't reach B. At least not in finite time.
I would prefer if you learned it instead of thinking it was illogical and that you have to accept it on faith. This issue is not difficult. It ain't quantum mechanics!Deepak K Kapur said:@Drakkith
Great many thanks for such a considerate answer.
I think I will have to accept this as a mystery even more deeper and confusion than the 'cause of big bang'
Only if you don't divide the time intervals by the same factor as you divide the distance intervals.CWatters said:If there are an infinite number of points then each is infinitely small. So if you move point-to-point you move infinitely slowly. So I'd say no you won't reach B. At least not in finite time.
Perhaps that could be put another way. The initial description of the phenomenon is where the problem starts. The situation cannot be described in terms of finite steps because it is a continuum of states. Initially describing it in the wrong way is what introduces the 'paradox'. Maths should not beat itself up about this.rumborak said:This is probably partially the usual "does physics/math describe reality, or only reality's phenomena?" discussion. Points, limits (in the mathematical sense) etc are excellent tools to describe all of our experiments, but that in turn does not necessarily mean they are physically "real" (nor does physics make a claim that they are). In that sense, one must be careful using those mathematical tools for thought experiments like this.
russ_watters said:I would prefer if you learned it instead of thinking it was illogical and that you have to accept it on faith. This issue is not difficult. It ain't quantum mechanics!
Try this: if you need to measure the length of a 1m object and have a choice of meter sticks with tick marks in meters, centimeters, millimeters or micrometers, does your choice of meter stick change the length you are measuring?
The point is that it doesn't matter how many points there are (how small the divisions are), the length does not change: it is still just 1 meter. Even if there are an infinite number of points -- which there are.Deepak K Kapur said:You are right. The length will not change.
But suppose..
I use infinitometers (infinitely small unit of length), would I be able to measure the length of the said object?
russ_watters said:The point is that it doesn't matter how many points there are (how small the divisions are), the length does not change: it is still just 1 meter. Even if there are an infinite number of points -- which there are.
If the length is always the same, then traversing it is always the same. Take a large step. Did you just tavel 1m, 100cm or 1000mm? All of them: they are all the same.Deepak K Kapur said:I think the question is not of the sameness of
length but that of 'traversing' the said length...
russ_watters said:If the length is always the same, then traversing it is always the same. Take a large step. Did you just tavel 1m, 100cm or 1000mm? All of them: they are all the same.
How does this relate to your original question? Aren't we talking about reality here? If you take 1 step, you take one step. Not 100, not 1000, not a million, not infinity, one. That's reality. It is almost like you are trying to disprove reality by making up a scenario that isn't reality and disproving that!Deepak K Kapur said:I may be wrong but by 'traversing' I mean point by point 'traversing'.
If point are infinite, point by point 'traversing' cannot take me from A to B. Infact, I think I even will not be able to move from A in this way.
No. But so what? You don't do that. You can't do that -- the way you actually move is different. So what use does this question have?I mean if I 'move point by point from A' i.e one point at a time, can I reach B?
russ_watters said:How does this relate to your original question? Aren't we talking about reality here? If you take 1 step, you take one step. Not 100, not 1000, not a million, not infinity, one. That's reality. It is almost like you are trying to disprove reality by making up a scenario that isn't reality and disproving that!
[edit] From your second post (which it doesn't appear anyone really answered directly):
No. But so what? You don't do that. You can't do that -- the way you actually move is different. So what use does this question have?
These questions are not identical to each other. When you take a step you take one step. You don't do "point by point traversing" (stopping at every point), but you do cross an infinite number of points.Deepak K Kapur said:My original question also meant point by point 'traversing'. May be I was not able to make it clear..
When I take a step how many points do I traverse?
If it's infinite points, how can infinity be ever traversed?
russ_watters said:You don't do "point by point traversing" (stopping at every point), but you do cross an infinite number of points.
Sorry, they are not.Deepak K Kapur said:I think the two ideas in the above statement are contradictory.
Why? That makes no sense. The universe is filled with points that people don't travel to and stop. Whether you stop at a point has nothing to do with whether they exist (as real entities or non-physical, mathematical tools).If there is no stopping, the concept of a point ceases to exist,IMO.
Fictitious tool or not is not a critical issue, but they most certainly do correspond to reality; The math works.Then, a 'point' is just a fictitious tool. Points don't correspond to reality.
That's just not true. We have a definition that works: you invented your own definition, that doesn't work, and are trying to use it to say reality is wrong. It makes no sense. Why do that? Why not just use what works?Perhaps, a 'continuum' has no proper definition.