# Circular Math in Physics

1. Oct 5, 2014

### Physics_Kid

so, i am wondering, the math equation for a circle, we can prove it has infinte number of points, thus no sides, but thats on paper. is there anything in observable universe that shows us this math??

2. Oct 5, 2014

### phinds

You seem to be confusing math with reality. I'm not even sure what your question is, really.

3. Oct 5, 2014

### bistan

I think he's asking if there's a physical basis for the idea that a circle is an infinite number of points at radius R from the origin. Whether or not idealized models of physical reality exist outside of the mind is more of a philosophical question than a physical one I think.

4. Oct 6, 2014

### Staff: Mentor

If the orbit of a planet comprised a series of straight line segments it would make for a very shuddering ride!

5. Oct 6, 2014

### SteamKing

Staff Emeritus
Why limit yourself to just circles? You could make a similar argument about the number of points in an ellipse, or a rectangle, or just about any geometric figure.

6. Oct 6, 2014

### CWatters

and give us problems explaining how the sun modulated gravity to make the planet move like that.

7. Oct 6, 2014

### A.T.

What's the difference between infinite number of points and infinite number of sides ? Or even a finite number of sides? A square has an infinite number of points but finite number of sides.

8. Oct 7, 2014

### BobG

No. Assuming you had a circle made of matter, there would be a finite number of atoms making up the circle. Of course, keep in mind your circle would also have more empty space than occupied space.

Your circle with an infinite number of points is more a thought than something you can observe.

But, that doesn't mean the two are irrelevant to each other. For a long time, there was a rather large conflict between those that said a circle was a continuous entity which could be divided infinitely many times. And then there were those that believed that geometric shapes have to be composed of infinitesimals, similar to the smallest building blocks of matter. Very different starting points in the two trains of thought - starting from the whole and dividing forever smaller without end or starting from an infinitesimal that's so small it takes an infinite number of them to build a circle.

Math often describes reality and reality often provides ideas for mathematical theories, but the two are seldom quite the same as each other.