ELI5: Explain Like I'm 5

Orders of magnitude (probability)

Ok kiddo, think of orders of magnitude as a way to measure how big or small things are. Imagine you have a bunch of marbles, and you want to know how many you have. If you count them one by one, that will take a long time if you have a lot of marbles, right? So people came up with orders of magnitude to help them measure things quickly.

Let's say you have 10 marbles, that's an easy number to count, right? Now imagine you have 100 marbles. That's 10 times more than 10, so we say it's an order of magnitude bigger. And if you have 1,000 marbles, that's 10 times bigger than 100 marbles, so now we're talking about two orders of magnitude.

Now, let's talk about probability. Probability is a way to measure how likely something is to happen. For example, if you flip a coin, there are two possible outcomes: heads or tails. If you want to know the probability of getting heads, you divide the number of ways to get heads (1) by the total number of possible outcomes (2), which equals 0.5 or 50%.

But what if you want to measure something really, really, REALLY unlikely to happen? Like winning the lottery or getting struck by lightning? This is where orders of magnitude come in handy again. We use them to measure the probability of rare events that are many, many times less likely to happen than something more common, like flipping a coin.

When we talk about orders of magnitude in probability, we're talking about multiples of 10. Imagine you have a probability of winning the lottery that's 1 in 1,000,000. That's 6 zeros after the 1, right? So we say the probability is on the order of 10 to the power of minus 6 (10^-6). This means the probability is 1 divided by 1,000,000. Now, if we talk about getting struck by lightning, the probability is about 1 in 700,000. That's still an incredibly small probability, but it's on the order of 10 to the power of minus 5 (10^-5), which is one order of magnitude higher than the lottery probability.

So, in short, orders of magnitude in probability tell us how much bigger or smaller a very unlikely event is compared to something more common. But remember, just because something is really unlikely, it doesn't mean it can't happen!