eli5: How do meteorologists determine when sunrise and sunset occur (down to the minute) if it’s still light or dark outside visually?

Question

I was looking at the weather app and, from where I live, sunset occurs exactly at 7:16 pm. Outside, the sky is a dark blue but still light enough to see and navigate the world. On the weather app it displays “Civil Twilight”, “Nautical Twilight”, and “Astronomical Twilight”. If these sunset periods occur after 7:16, then how do we know that sunset occurs exactly at 7:16 and not at these other time periods?

In: Planetary Science

Answer 1

Sunset happens when the sun drops below the horizon, not when the sky gets dark.

And for those sunset times, they just calculate it in an idealized scenario where theres no hills or big buildings, just flat land or water all the way out to the horizon.

So you basically just treat the earth like a ball and pick a spot on the ball for your city, and the calculate when they wont be able to see the sun anymore.