Does a point have no dimension?

- anonymous

Does a point have no dimension?

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- mathslover

yes a point is dimensionless

- zepp

0D = Dot
1D = Line
2D = Plane
3D = Solid
4D = Space-time
5D = ...idk :P

- anonymous

Then how does it make a line?

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## More answers

- zepp

What do you mean?

- zepp

. <-- This is not a point, it's just a representation because a point has no height, no length, no thickness.

- zepp

One dimension: A line, numbers, they have only a length;

- zepp

2D: Shape, Length and width
3D: Solids, Length, width and thickness

- anonymous

What is the definition for a line?

- zepp

4D Spacetime: 3 dimentional object travelling/moving through time and space.

- zepp

Straight objects without depth and width.

- anonymous

Is it made of many points?

- zepp

Um, you can see it that way :)

- anonymous

When a point has no dimension then how can a collection of points make a line?

- zepp

A point has no length, depth, width, when you align then, you just created a length

- TuringTest

take a point and send it in some direction through space
the path that it traces out is a line
the real number line is infinitely dense so now we are getting into some of the trickyness of infinity

- TuringTest

|dw:1341410594698:dw|here is the real number line (still a line, consisting of infinitely many points)
I can ask you to pick out the point 1

- TuringTest

|dw:1341410679112:dw|and there it is
I can also ask you to find numbers between numbers
so if I ask you to find 1.5 it should be on the line

- anonymous

My doubt is when a point has zero dimension, then how can it make a line that has one dimension?

- TuringTest

|dw:1341410742343:dw|similarly I can keep asking you to find points between the two we have already found
1.75 must be on the line
1.85
1.8
1.8243574687654365768....
etc. must all be on the line
therefore there are infintiely many points on a line

- TuringTest

between any two points there are infinitely many numbers, do you agree?

- TuringTest

like between 1 and 2 are there not an infinity of numbers?

- anonymous

Though there are infinitely many points, each has zero length, zero breadth etc.

- TuringTest

but you are trying to add an infinity of infinitely tiny lengths!\[\infty\cdot\frac1\infty=\text{undefined}\]you can't treat infinity like a number and perform addition on it; it is a concept, rather than a number.

- TuringTest

it would require an infinity of points lined up in a row, and they still would have not length
this may seem paradoxical, but it reflects the infinite density of number distribution on the real line, so it is not trivial

- anonymous

Wouldn't 0+0+0+0........ be zero?

- TuringTest

no, because \(0\cdot\infty\) is undefined

- TuringTest

again, I know this does not make instinctive sense
infinity is a tricky topic that has driven many mathematicians mad!

- TuringTest

http://math.stackexchange.com/questions/28940/why-is-infinity-multiplied-by-zero-not-an-easy-zero-answer

- anonymous

When 0*infinity is undefined, then how does it produce a length?

- TuringTest

because you don't have to build a line one point at a time; it's a mathematical construct that contains infinitely many points

- TuringTest

if there were some finite number of points that you could put together to make a line, then the real number line would not be infinitely dense (i.e. some points would be missing from the line because there would have to be a limit on the number of times I can tell you to find the midpoint between two points)

- TuringTest

|dw:1341411610187:dw|take any line segment; I want the midpoint (whatever it is)

- TuringTest

|dw:1341411643038:dw|now I want the midpoint of the right half

- TuringTest

|dw:1341411666632:dw|now again, the midpoint of the right half

- TuringTest

|dw:1341411687412:dw|we could do this forever, right?
that means there are infinitely many points on that line; I can always ask you to find the midpoint between any two points.

- TuringTest

yet even though it is an infinity of points, they only add up to a finite line segment, so an infinity of things can add to something finite.
Reference to Zeno's paradox.

- anonymous

What does "though it is an infinity of points, they only add up to a finite line segment" mean?

- zepp

TuringTest just showed that there's an amount of point between two point, but when this infinite adds up, it gives something finite, something you can just count on your fingers.

- zepp

an infinite amount*

- anonymous

How can infinite things add and give some finite value?

- anonymous

It is important to understand here that points and lines are simply geometric realizations of abstract concepts. As mentioned earlier, a . is not a point, nor is a drawing of a line actually a line. A point takes up no space, so it can't be shown, and similarly a line can't be shown because it has no height. Even a plane can't be shown really, because it has no depth. So, when you're asking these questions, it is best to avoid relying too heavily on your geometric interpretation of the concepts. Instead, it is better to look at them using the tools of analysis.
TuringTest is referring to some relevant results of analysis, for example, the uncountability of the real line. Not only is the real line infinite in the number of points, it is uncountably infinite. This ends up implying that the number of points between 0 and 1 is actually the same as the number of points on the entire real line. So, to interpret this somewhat geometrically, you can zoom in as close as you would like to the real line and still be looking at the same number of points. Of course, this doesn't work like any real-world object.
Another relevant way of looking at the real line is through the lens of topology. We can talk about the real line as a metric space, and we define the metric abstractly. We simply define how distance works. One sees by learning some introductory topology that the real line is actually just one way to look at the set of real numbers, and there are many others. So, this is another way to look at the problem.

- TuringTest

in answer to how an infinity of things can add up to something finite
do you know what an infinite series is @abdul_shabeer ?

- anonymous

No @TuringTest

- zepp

The sum of all terms of the geometric sequence that halves each time would be the perfect example :D

- TuringTest

\[\sum_{n=1}^\infty(\frac12)^n=\frac12+\frac14+\frac18+...=1\]when you study them this may make a little more sense
the one above can be said to represent Zeno's paradox

- anonymous

In general, we don't have an infinity of things simply "adding up" to finite value. We have an infinity of things approaching a limit that has finite value.

- asnaseer

Hey guys - I'm at work at the moment but spotted this discussion and remembered a thread I saw that might help explain this to to you @abdul_shabeer : http://mathforum.org/library/drmath/view/55297.html
Hope it helps - back to work now... :)

- UnkleRhaukus

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