How long is the longest day? For the smart alecks (this is family friendly blog) out there, the answer is obviously 24 hours. For the true nerds (sorry if that’s most of you) the more correct answer is just a shade under 23 hours and 56 minutes. This slight discrepency is what drives the formula for leap years. Specifically, every year evenly divisible by 4, unless it’s also divisible by 100, but not 400. To clarify, 2000 was a leap year, but 2100 will not be one.
All right now that we’ve laid to rest that bit of silliness, back to our original question. Perhaps it’s best to rephrase it as, how much sunlight will you receive on the summer solstice? As a quick refresher, the Earth’s axis is tilted 23.44 degrees from it’s orbital plane. The tilt, not the actual distance from the sun is what creates our seasons. We define the summer solstice as the day when the Earth’s pole has it’s maximum tilt toward the sun. This event occurs twice per year once in the northern hemisphere and later in the southern hemisphere. In 2020, the solstice falls on 20 June in the northern hemisphere and 21 December in the southern hemisphere.
With science now satisfied, what about our answer. As you’ve come to expect, we have a map for that. This map comes courtesy of Brian Brettschneider.
A wee bit more
While that certainly answers the question about sunlight on the longest day (at least in the northern hemisphere), it’s not a very satisfying answer. That of course leads to another rephrasing of our question. At what time of day will the sun set on the longest day of the year?
To answer this question, you must also take the Earth’s rotation and the borders of our time zones into account. The maps to answer this question come courtesy of NOAA.
Sunset on the summer solstice in North America
Sunset on the summer solstice in Europe
As always thanks for reading.
Armen
Note to Pay the Bills: Borrowing from Celtic mythology the books in the Misaligned Series have a special connection to astronomical events such as the equinoxes, solstices, and the midpoints between them. How do these events fit into a Young Adult fantasy series about Arthurian legend in upstate NY? Learn more by reading a summary of the series here and find links to purchase books here.
Parev Armen:
Reading your very interesting piece, I was reminded that on Dec 21, 2010 (shortest day in the northern hemisphere), we drove very early to the town of Sogamoso in central Colombia to participate in an indigenous “healing” ceremony on the occasion of the solstice. The day coincided with a full lunar eclipse which made it doubly special. We removed our shoes and entered the Temple of the Sun, a place of worship for the Muisca Sun-god Zué. We joined indigenous people chanting to a mesmerizing drum beat and going in circles. At 3 AM sharp, and I mean sharp, I looked through a window and saw the rising sun. Through the only other window directly opposite, I saw the lunar eclipse. The temple is a replica built by an archaeologist in 1942 who obviously built it to spec and in the right spot. How else could the windows offer such a perfect sight?
In Armenia, our ancestors’ land, I’ve visited the “Armenian Stonehenge”. It’s comprised of 200 stones spread over a large field. Eighty of the stones have circular holes about 5″ in diameter. It’s believed to have been an astronomical observatory more than 7,000 years ago. Yes, that’s how far back Armenians go! If interested, this is the link: https://www.ancient-origins.net/ancient-places-asia/armenian-stonehenge-incredible-history-7500-year-old-observatory-zorats-karer-021027.
Best regards
Varouj
Varouj, I’m glad you enjoyed the post and thanks for the link to the “Armenian Stonehenge.” There’s quite a lot about ancient people and cultures that we will never understand. Best – Armen