In the mathematical area called Topology. A sphere (a geometric solid like a ball) is homologous or similar to a Torus (another geometric 3 dimensional solid shape like the shape of a ring doughnut).
Obviously, there is a difference between the shape of the ball and a doughnut. A ball is perfectly round, while the doughnut has a hole in the middle like the floaters we use when we swim. But in topology, they say that "There's not much a difference."
Another one. In topology, a coffee cup is the same shape as the doughnut. The explanation they give is: Because they both have a hole. The coffee cup's hole is the space between the handle. And then, just do some transformation etc...etc... and there you have it, your mug turned into a doughnut!
By using the logic of math if a=b, and b=c, then a=c, substituting the ball for a, doughnut for b and mug for c, then , that implies, that the ball is the same as the coffee cup! Okay, then.
Now, isn't it that basically, the world is the shape of a sphere, or a ball? I mean. Yes, I know that it is not perfectly round. But it has no hole or puncture whatsoever anywhere as the doughnut, a mug, or a floater has, right? But again, topology has something to say: If we can transform the ball into a doughnut and a coffee cup, we can transform the world into a doughnut.
The world can be transformed into a doughnut (sphere becoming a torus, to be more generic) by the mathematics of what topologists now call: Surgery, invented by Mr. G. Perelman.
Topology is really awesome, and I adore topologists alot. And before I close this, I just want to add the quote of the Fields Medal recipient on 2007 (but declined to), Mathematician and topologist Grigory Perelman: "I do not need a prize,cash, or even fame. I could shrink the world into a single point, what more can I ask for?"