Actscelerate.com Forum Index Actscelerate.com
Open Any Time -- Day or Night
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
r/Actscelerate

A little math conundrum I need help with....

 
   Actscelerate.com Forum Index -> Acts-Celerate Post new topic   Reply to topic
View previous topic :: View next topic  
Message Author
Post A little math conundrum I need help with.... Aaron Scott
First, we know that three dimensions are perceivable by us: one dimension, two dimensions, and three dimensions. The other day, I just happened to think of a way to demonstrate all three (at least in theory):

You have a perfectly flat plane and a perfect sphere (lets say about the size of a baseball) rolling on the plane. Well, the place where the sphere touches the plane is one dimensional, the plane is two dimensional, and the sphere is three dimensional.

So, that's just for free. Now for the puzzle (and I don't know the answer either!):

If a perfect sphere is placed on a perfect plane, how large is the point of contact between them?

If you claim that it is a thousandth of an inch (say), is that correct? For if the sphere and plane are perfectly round and flat, respectively, it seems that the point of contact is infinitely small (or so it seems to me).

It is infinitely small then it would almost seem that one could argue that the sphere never really touches the plane, since there is no (seemingly) literal size to the point of contact.

At the same time, if the sphere is resting on the plane, then surely there must be a point of contact.

Ideas?
Hon. Dr. in Acts-celeratology
Posts: 6027
10/19/20 11:32 am


View user's profile Send private message Visit poster's website
Reply with quote
Post According to smart people on Quora and Reddit... Aaron Scott
this problem is not original with me. But it does make me feel good to know that I am thinking like smart people.

They said that, first, there is no such thing as a perfect sphere or plane in reality. But a mathematically perfect sphere that is touching another sphere or a perfect plane...would have, at most, a single atom making contact.

At least I think that's what they said. I think they were Pakistani or Cuban.

If you wish to contest this answer, let me know, and I will get right over to smack you about the face with a wet dish towel (NOT that I'm doing dishes are anything girly like that!).
Hon. Dr. in Acts-celeratology
Posts: 6027
10/19/20 1:50 pm


View user's profile Send private message Visit poster's website
Reply with quote
Post Bro Bob
The contact area would be one point. That point has no size. But that one point would be common to both the plane and the sphere. The same as when two lines intersect or when a line penetrates a plane.

And this is a geometry problem I believe, not a math problem.

Anyway, that is how I see it in my mind.
Golf Cart Mafia Underboss
Posts: 3945
10/19/20 8:07 pm


View user's profile Send private message
Reply with quote
Post Bro. Bob, now it gets interesting.... Aaron Scott
If it has no size, then is it touching the plane? Hon. Dr. in Acts-celeratology
Posts: 6027
10/20/20 9:48 am


View user's profile Send private message Visit poster's website
Reply with quote
Post Dave Dorsey
It is a point on the plane. It is not distinct from the plane. [Insert Acts Pun Here]
Posts: 13654
10/20/20 10:32 am


View user's profile Send private message
Reply with quote
Post Dave... Aaron Scott
I agree with you that it MUST be touching. But if it has no size (or at least none we can define), then just what IS touching?

It kind of reminds me of that claim that if John receives the kick-off in his own end zone, at some point, he goes half the distance to the other end zone...then half of that, then half of that, then half of that, and then...you get the idea.

If he is always reaching the halfway point between where he is and the end zone, then how can he ever score a touchdown?
Hon. Dr. in Acts-celeratology
Posts: 6027
10/20/20 11:01 am


View user's profile Send private message Visit poster's website
Reply with quote
Post Dave Dorsey
There are not three distinct entities -- the sphere, the plane, and the point of contact. There are only two. The sphere is touching a point on the plane.

The plane itself is made up of an infinite number of points existing in two dimensions, giving it both width and height. If it is touching the plane, the sphere is touching one or more of those points.


Last edited by Dave Dorsey on 10/20/20 7:49 pm; edited 1 time in total
[Insert Acts Pun Here]
Posts: 13654
10/20/20 6:18 pm


View user's profile Send private message
Reply with quote
Post Bro Bob
Just as a line that touches a circle at only one point is a tangent line, a plane that touches a sphere at only one point is a tangent plane.

A circle is always the result when a plane intersects a sphere.
Golf Cart Mafia Underboss
Posts: 3945
10/20/20 7:48 pm


View user's profile Send private message
Reply with quote
Post Dave Dorsey
Bro Bob wrote:
Just as a line that touches a circle at only one point is a tangent line, a plane that touches a sphere at only one point is a tangent plane.

A circle is always the result when a plane intersects a sphere.

Concur with this.
[Insert Acts Pun Here]
Posts: 13654
10/20/20 7:50 pm


View user's profile Send private message
Reply with quote
Post Dave...I agree, but Aaron Scott
Dave Dorsey wrote:
There are not three distinct entities -- the sphere, the plane, and the point of contact. There are only two. The sphere is touching a point on the plane.

The plane itself is made up of an infinite number of points existing in two dimensions, giving it both width and height. If it is touching the plane, the sphere is touching one or more of those points.



That the plane is touching the sphere. But if we cannot define how large (or small) that point of contact is, then are we just saying it's touching as a matter of definition only?
Hon. Dr. in Acts-celeratology
Posts: 6027
10/21/20 6:47 am


View user's profile Send private message Visit poster's website
Reply with quote
Post Cojak
This is tough. But the logic BB uses seems correct here. But then I am in NC! Smile
_________________
Some facts but mostly just my opinion!
jacsher@aol.com
http://shipslog-jack.blogspot.com/
01000001 01100011 01110100 01110011
Posts: 24269
10/21/20 7:49 pm


View user's profile Send private message
Reply with quote
Display posts from previous:   
Actscelerate.com Forum Index -> Acts-Celerate Post new topic   Reply to topic
All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum




Acts-celerate Terms of Use | Acts-celerate Policy
Contact the Administrator.


Powered by phpBB © 2001, 2005 phpBB Group :: Spelling by SpellingCow.