ELI5: Explain Like I'm 5

Nonstandard calculus

Okay kiddo, you know how in math class we learn all about different kinds of numbers like whole numbers, fractions and decimals, right? Well, nonstandard calculus is a type of math that uses really different numbers than we're used to working with. These different numbers are called "infinitesimals" and "infinities".

An infinitesimal is a number that's very, very, very small - so small that it's almost like it's zero. But the thing is, it's not exactly zero. Imagine if you had a cake, and you cut it into a million little pieces. Each of those pieces would be really small, right? But they'd still be bigger than an infinitesimal.

An infinity, on the other hand, is a number that's really, really big - so big that it's almost like it's infinite (hence the name). It's like if you took all the cookies in the world, and tried to count them. You could keep counting and counting, but you'd never get to infinity.

Now, in regular math, we can't really work with infinitesimals and infinities because they don't really fit into our number system. But in nonstandard calculus, we use them all the time! It's like a whole new way of doing math.

One thing that's really cool about nonstandard calculus is that we can use it to talk about things like curves and slopes. You know how when you draw a line on a piece of paper, you can describe how steep it is? That's called the "slope". Well, with nonstandard calculus, we can figure out the slope of a curve, even if it's really, really wiggly.

Another thing that's neat about nonstandard calculus is that we can use it to solve some really tough problems. For example, let's say you wanted to figure out how long it would take for a rocket to travel from Earth to the moon. That's a really complicated problem, right? But with nonstandard calculus, we can break it down into smaller pieces and figure out the answer.

So, that's nonstandard calculus in a nutshell. It's a type of math that uses different kinds of numbers to solve really tough problems. Pretty cool, huh?