# Why are the formulas for the sphere so weird? (major upgrade of Archimedes' greatest discoveries) | Summary and Q&A

166.1K views
November 25, 2023
by
Mathologer
Why are the formulas for the sphere so weird? (major upgrade of Archimedes' greatest discoveries)

## TL;DR

This video explores the mathematical history and discoveries surrounding the volume and surface area formulas of the sphere, using creative visualizations and demonstrations.

## Key Insights

• 💠 Turning a hemisphere inside out reveals a shape similar to a cylinder minus a cone, leading to a breakthrough in understanding the volume of a sphere.
• 🥳 Archimedes discovered that the ratio of the volume and surface area of a sphere compared to a cylinder is 3:2, a relationship that fascinated him to the extent of engraving it on his tombstone.
• 🛟 By unfolding the surface of a sphere using various techniques, mathematicians can demonstrate the area-preserving property of transformations, providing insights into the formulas and properties of the sphere.

## Transcript

Welcome to an extra-extra-extra-special  Mathologer video. Why extra-extra-extra-special,   three extras? Well, first extra, it's the 100th  Mathologer video. There, the thumbnails for the   first 99 videos. It's been quite a journey :)  Second extra: it's my first crossover episode.   For the first time, I'm collaborating with  another channel. Ma... Read More

### Q: What is the significance of turning the hemisphere inside out into a shape resembling a cylinder minus a cone?

By turning the hemisphere inside out, mathematicians can derive the volume formula for a sphere by subtracting the volume of the cone from the volume of the cylinder, providing a new perspective on an ancient mathematical problem.

### Q: How does the volume formula for a sphere relate to Archimedes' achievements?

Archimedes established the volume and area formulas of the sphere, but Cavalieri, a mathematician 400 years later, refined the understanding by comparing the shapes of a cylinder and a cone.

### Q: How is the area-preserving property of transforming the sphere into a circle demonstrated?

The video showcases a folding technique using crescent moon shapes to unfold the surface of the sphere onto a circle, preserving the area. This property is visually demonstrated by the smooth transition of the moons without leaving gaps.

### Q: How are the volume and area formulas of the sphere related to each other?

The video explains that the volume formula, 4/3πr^3, and the area formula, 4πr^2, share a common aesthetic appeal, with the area formula being derived from the derivative of the volume formula.

## Summary & Key Takeaways

• The video celebrates the 100th Mathologer episode and features a crossover collaboration with mathematician and 3D printing artist Henry Segerman.

• The first discovery showcased involves turning a hemisphere inside out to reveal a new shape, which is approximately a cylinder minus a cone.

• The video then explores how the volume formula of a sphere can be derived by subtracting the volume of the cone from the volume of the cylinder.

• Additionally, the video delves into the surface area of the sphere, explaining its relationship to the area of its shadow circle and showcasing an area-preserving transformation.