ELI5: Explain Like I'm 5

Continuous linear extension

Imagine you have a row of toys arranged in a straight line. You can pick up one toy and move it slightly to the left or right, but you can't change the order of the toys or add new ones.

Now, imagine you have a grown-up's job and you're trying to solve a really complicated math problem that involves a bunch of rules about how numbers can be combined. Maybe one of those rules says that if you add two numbers together, the result has to be between 0 and 1.

But what if you have two numbers that don't quite fit that rule? Maybe one is -0.5 and the other is 0.8. You can't just add them together and get a result between 0 and 1, so what do you do?

This is where continuous linear extension comes in. It's a way of "stretching" the rules to include all of the numbers you need, even if they don't fit perfectly at first.

Going back to our toy example, imagine you have a ruler and you can measure the distance between each toy. Maybe the first toy is 1 inch from the edge, and the second toy is 2 inches from the edge. You can use this information to create a "map" of where each toy belongs in the line.

In math terms, this map is called a function. It takes each number (or "input") and tells you where it belongs in relation to the other numbers (or "output").

Now, let's say you have two numbers that don't fit the rule we talked about earlier. Maybe -0.5 is too far to the left and 0.8 is too far to the right. Instead of trying to force them into the existing line, you can use the function to "extend" the line so that they fit.

This means that you might have to add some new numbers to the line in order to make everything work out. You'll still keep the same order as before, but you might have to "squeeze" some of the other numbers closer together so that -0.5 and 0.8 can fit where they need to.

The important thing is that the function stays "continuous" throughout the process. That means that if you pick any two numbers that are really close together (like 1 and 1.0001), the function won't suddenly jump or break in the middle. It will still give you a smooth, consistent result.

Overall, continuous linear extension is a way of adapting the rules to fit the situation at hand, without sacrificing mathematical rigor or clarity. It involves creating a flexible "map" of the numbers involved and using that map to find creative solutions to challenging problems.