Metro

Dave Epstein

Good news: 8 p.m. sunsets begin this week

A view of Fisherman's Beach in Swampscott earlier this month.
Katherine Taylor for The Boston Globe
A view of Fisherman's Beach in Swampscott earlier this month.

For many, childhood summer memories revolve around being outside late into the evening after a warm summer day. It’s those late sunsets that make any of that possible. This week the sun will start setting at 8 p.m. and later, and those 8 p.m. sunsets continue all the way until Aug. 4.

In this part of the world, the amount of daylight we receive changes dramatically from December through June and then again from June to December. It’s not quite as crazy as it would be if you lived at the top of the planet, where they gain 24 hours of daylight and then lose 24 hours of daylight each year. Here, we go from about 9 hours of daylight to about 15½ hours of daylight over the course of the seasons.

The reason for the changing amount of light is, of course, because the Earth is tilted on an axis and revolves around the sun. During the warmer months, this allows the northern hemisphere to be tilted towards the sun, and in the colder months, the northern hemisphere is tilted away from it. The opposite is true if you are from Australia and other points south of the equator.

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The amount of daylight is the same no matter what time zone you are in, as long as you are along the same line of latitude. This time of the year, the farther north you go, the more daylight you receive, and the farther south, the less. Folks in Miami have well over an hour less daylight than we do around here. Interestingly, most of their daylight loss occurs in the morning because they’re in the western part of the Eastern time zone.

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Places like Burlington, Vt., and Montreal already have their sunset occurring after 8, and they will get later too. On the first day of summer, you can expect those areas to see the sun sink below the horizon at 8:40 p.m. and 8:47 p.m., respectively. The later time is due to the fact that they are farther north and farther west in the Eastern time zone.

If you want a real treat, you could head up to Barrow, Alaska, where the sun is now staying up all day. Or for a more international flair, head to Paris on the first day of summer, where the sun will set at two minutes before 10 p.m. This is due to the city’s position on the planet as well as its time zone location.

The later daylight, of course, means less time for stargazing. Civil twilight and nautical twilight are those times when the sun has set but it’s not completely dark yet, which leads us into full night. This time of the year, that category of darkness is quite small and continues to shrink. In parts of the world like Paris there is no official night around the summer solstice.

Locally, the gap between sunrise and sunset will continue to grow for the next four weeks, but again because of the tilt of the Earth, the earliest sunrise is actually going to be on June 14, with the latest sunset not occurring until June 26 and 27. The maximum amount of daylight is of course the first day of summer, and after that, the daylight slowly shrinks, which nobody likes to think about because some of the kids won’t even be out of school yet.