Can Pappus' Theorem Explain the Gaps on a Torus?

In summary, Pappus's centroid theorem originally comes from an integral proof, where the infinitesimally small width of each "slice" allows for the disregard of physical laws regarding gaps. This is similar to the concept of Riemann Sums, where taking infinitesimally small slices eliminates gaps in calculating the area under a curve. Therefore, when applied to a torus, Pappus's theorem also accounts for the infinitesimal width of each slice, resulting in no gaps between the discs on the outer edge.
  • #1
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http://en.wikipedia.org/wiki/Pappus's_centroid_theorem (the second one)

When we do this with a torus, wouldn't we gaps tiny gaps between the discs on the outer edge? The slices are closer together on the inner edge and this prevents them from getting any closer on the outer edge so shouldn't we have some gaps?
 
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  • #2
Note that Pappus theorem originally comes from an integral proof. With integration, each "slice" has an infinitesimally small width, a width at which you could completely disregard the physical laws of "having gaps because the slice has a uniform width". This is the difference between a summation and an integral.

To further illustrate things, imagine you have a curve and you want the area under it. If you take rectangular slices, you'll never be able to cover the entire area, and you're going to have gaps. However, if these rectangular slices are infinitesimally small, the gaps are going to grow smaller, until you reach a point where the width of the slice is 0, and the unaccounted gaps are therefore also 0.

Here's an image for further comprehension of the idea. Notice how gaps get smaller. It's the same way with applying Pappus theorem to a torus.
Riemann Sums GIF
 

What is Pappus' theorem intuition?

Pappus' theorem intuition is a geometric theorem that states that the volume of a solid generated by revolving a plane figure about an axis outside the figure is equal to the product of the area of the figure and the distance traveled by the center of mass of the figure.

Who is Pappus and why is this theorem named after him?

Pappus was a Greek mathematician who lived in the 4th century AD. He is known for his work in geometry and is believed to have discovered the theorem that now bears his name. The theorem was named after him in recognition of his contributions to mathematics.

What is the practical application of Pappus' theorem intuition?

Pappus' theorem intuition has practical applications in engineering, physics, and architecture. It can be used to calculate the volume of objects with complex shapes, such as gears and turbines, when they are rotated around an axis.

What is the difference between Pappus' theorem intuition and Pappus' centroid theorem?

Pappus' theorem intuition and Pappus' centroid theorem are closely related, but there is a key difference between them. Pappus' theorem intuition deals with the volume of a solid generated by revolving a plane figure, while Pappus' centroid theorem deals with the centroid (center of mass) of that figure.

Can Pappus' theorem intuition be extended to higher dimensions?

Yes, Pappus' theorem intuition can be extended to higher dimensions. In three dimensions, it is known as Pappus' centroid theorem, and in higher dimensions, it is known as the generalized Pappus theorem.

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