ELI5: Explain Like I'm 5

Doubling the cube

Okay, so imagine you have a block of ice. You want to make another block that is twice the size of the first block. That's kind of what it means to double the cube.

But here's the tricky part: you can't just double the length of each side of the cube to make it twice as big. If the original cube had sides that were 1 unit long, doubling the length of each side would give you a cube with sides that are 2 units long. But the volume of the new cube would be 2 x 2 x 2 = 8 units cubed. That's not twice the volume of the original cube, which is 1 x 1 x 1 = 1 unit cubed.

So how do we actually double the cube? Well, there's a math problem that has been around for thousands of years that tries to solve this problem. It's called the "doubling the cube" problem.

There are a few steps involved, but basically what you need to do is find the side length of a cube that has twice the volume of the original cube. This involves some pretty complicated math, but the basic idea is to use something called the cube root.

Think of the cube root like this: if you take a number and cube it (multiply it by itself three times), the cube root is the number you started with. So if you cube 2 (2 x 2 x 2 = 8), the cube root is 2.

Now, to double the cube, we need to find the cube root of 2 (because we want to find the side length of a cube that has twice the volume of the original cube). But here's the problem: the cube root of 2 is a number that can't be expressed as a simple fraction or decimal. It's an irrational number, which means it goes on forever without repeating.

Because of this, it's impossible to exactly double the cube using just a ruler and compass (the tools that were available to ancient mathematicians). However, we can get pretty close by approximating the cube root of 2 using some clever math tricks.

In the end, while we can't exactly double the cube, we can get pretty close by using some advanced math. And that's the basic idea behind the "doubling the cube" problem.