Sothic cycle

Okay kiddo, have you ever seen a clock? It goes tick-tock, tick-tock, right? Well, the ancient Egyptians also had a way to mark the passage of time. They used something called the "Sothic cycle."

The Sothic cycle is like a really big clock that takes 1,460 years to complete one full cycle. That's a looong time! The cycle started over 4,000 years ago, back when the ancient Egyptians were around.

Here's how it works: the ancient Egyptians noticed that a certain bright star in the sky, called Sirius, rose just before the sun on the first day of their calendar year. They called this day the "heliacal rising" of Sirius.

Then, they figured out that if they waited exactly 365.25 days (which is how long it takes the Earth to orbit around the sun), Sirius would rise again on that same day. They used this knowledge to make their calendar.

But here's the thing: because the Earth wobbles slightly as it spins, the heliacal rising of Sirius actually drifts backwards a tiny bit each year. Over time, this means that the heliacal rising of Sirius happens on different days of the year.

After about 1,460 years (which is roughly four times the length of a human lifespan), the heliacal rising of Sirius returns to the same day of their calendar year. And that's when a new Sothic cycle begins!

So the Sothic cycle is like a really big clock that tracks the movement of Sirius in the sky, helping the ancient Egyptians keep track of time for thousands of years. Neat, huh?