After the sun begins to set, you always want to know just how much time you have before it really gets dark. Whether you’ve left the dog at home alone, or you’re wondering how long you’ll have to wait before you can get a good look at the night sky, it’s a good idea to know how much time you have before it gets dark. So, let’s look at just how long it takes to get dark after sunset.
After the sun sets, how long does it take to get dark?
The correct answer is that it’s going to be completely different for each different location on Earth. If you’re close to the equator, then it can take only 20 or 30 minutes for it to get dark. However, on average it takes around 70 minutes for it to get fully dark after sunset.
This is true for people located in the United States or in the majority of Europe. However, this can differ a lot as you move closer or further away from the equator.
Why does this differ so much?
Say for example, you’re located very far North on our planet. The further North you are, the more diagonal the path is that the Sun‘s route is to going beneath the horizon, so the Sun may never really progress into nighttime.
I think this is probably best explain by looking at the city Tromsø, which is located in the very North of Norway.
Tromsø’s Midnight Sun
As I mentioned, Tromsø is a country that’s right in the very North of Norway, and the North of the Earth too. During the summer months of May, June and July, Tromsø experiences something called the “midnight Sun”, also known as a polar day.
During these months, the city doesn’t have a proper nighttime – instead, it stays fairly light and visible 24/7. This occurrence happens because Earth’s axis is slightly tilted towards the Sun. So, we know that twilight is the period of time where the Sun is between 0° and 18° degrees beneath the horizon.
We go from civil twilight (0-6°) to nautical twilight (6-12°) all the way through to astronomical twilight (12-18°) – this is the amount of degrees beneath the horizon our Sun is in relevance to us. For us to progress into nighttime, the Sun needs to be more than 18° below the horizon.
However in Tromsø, this doesn’t happe during these months due to the Earth’s inclination. This means that whilst Tromsø does experience twilight, the Sun never goes beneath the 18° angle required for darkness. So, they can still see the Sun’s glow all through the night.
Tromsø’s Polar Night
At the other end of the spectrum, in the Winter time Tromsø has the complete opposite. Through November to January, the Sun never comes completely above the horizon. So whilst it does get into the twilight phase and things to become visible in Tromsø, there is no daylight during these times as the Sun doesn’t come up above the horizon.
It isn’t just Tromsø that experiences this of course, but it’s a good example because it’s above the Arctic circle and one of the more Northern cities on our planet. It’s a good example of what happens when you’re much further away from the equator.
So in conclusion, there are no strict answers to say just how long it takes to progress from daytime, into twilight, and then into nighttime. However, you can probably find this out, and there will be a different answer depending on your location.
If you want to work this out for your own location, then I’d advise checking out www.timeanddate.com. This site can help you work out just how long it’ll take for the sun to set in your town or city now. But in some cities, the Sun never sets!