ELI5: Explain Like I'm 5

Dirac delta

Alright kiddo, imagine you are playing with a bunch of building blocks. You can stack them on top of each other to make a tall tower. Now, sometimes you might knock over the tower and all the blocks fall down. But what if you want to imagine that the tower never really fell down, and that it's still standing tall and proud?

Well, the Dirac Delta is kind of like that. It's a mathematical idea that helps us imagine that something very small, or even non-existent, can have a big effect on something else.

You see, in math we use something called a function to describe how one thing, like the height of a tower, depends on something else, like the number of blocks you use to build it. But sometimes we want to describe a situation where the thing we're looking at suddenly changes a lot, for example if the tower suddenly gets knocked over.

The Dirac Delta is a special type of function that jumps up really high at one particular value, let's call it "a". But it quickly drops down to zero again at all other values. This means that we can imagine the function as being almost zero, except when we're at the value "a".

So why is this useful? Well, imagine we have a function that describes how something changes over time, like the height of the sun in the sky. Let's say this function is zero when the sun is below the horizon, and it slowly increases as the sun rises.

Now, what if we suddenly put a big wall in front of the sun, so that it's completely hidden from our view? This would mean that the height of the sun suddenly drops to zero.

Using the Dirac Delta, we can imagine that the height of the sun actually jumps to a very high value, and then quickly drops down to zero again, all in the space of a single moment. This makes it easier for us to do calculations and make predictions about what might happen next.

So, in short, the Dirac Delta is a special type of function that helps us imagine that something very small or non-existent can have a big effect on something else. It's like imagining that the tower never really fell down, or that the sun suddenly disappeared behind a big wall.
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