Summer will officially arrive in the Northern Hemisphere on Thursday, June 20 at 4:51 PM EDT (2051 GMT) – the June Solstice.
At that moment, Sun It will reach the northernmost point of the celestial equator. To be more precise, when the solstice occurs, the sun will appear to shine directly overhead at a point on the Tropic of Cancer (23.5 degrees north latitude) in the eastern Pacific Ocean, roughly 1,100 statute miles (1,800 kilometers) southwest of Los. Angeles.
From mid-northern latitudes we can never see the sun directly overhead, but (as an example) as seen from Boston at 12:46 a.m. EDT on the day of the solstice, the sun will reach its highest point in the sky for the entire year. It stands 71 degrees above the southern horizon. To gauge how high this is, the fist you hold at arm’s length is about 10 degrees; hence, from the city known locally as “The Hub,” the sun will appear to climb more than seven fists above the southern horizon. And since the sun will seem to arc in such a high arc skyThe duration of daylight will be at its extreme, lasting 15 hours and 17 minutes.
twilight zones
However, this does not mean that we will be able to observe the stars for the remaining approximately nine hours of the solstice, because we also need to take twilight into account. On the June solstice, morning and evening twilight last two hours each at 40 degrees north latitude, meaning the sky is completely dark for only five hours.
Further north, twilight lasts even longer. At 45 degrees it lasts 2.5 hours, at 50 degrees twilight lasts all night; The sky never gets completely dark. On the contrary, the twilight period is shorter as you move south. While it takes 96 minutes at 30 degrees latitude, it takes only 80 minutes at the latitude of San Juan, Puerto Rico. That’s why northern U.S. travelers who visit the Caribbean this time of year are often surprised to see how quickly it gets dark after sunset compared to their home country.
By the way, the earliest sunrise and latest sunset do not coincide with the summer solstice. The first took place on June 14, while the second will not arrive until June 27.
Relating to: The brightest planets in the June night sky: How (and when) to see them
So far, so good
Most people are probably under the impression that: Soil At this time of year it is closest to the sun in its orbit, but in reality the opposite is the case. In fact, on July 5, at 1:06 a.m. EDT (0506 GMT), we will be at the farthest point in our orbit from the sun (called aphelion), at a distance of 94,510,539 miles (152,099,969 km). Conversely, on January 2, the Earth was at perihelion, its closest point to the sun. The distance difference between these two extreme points is 3,106,444 miles (4,999,337 km) or 3.3%; This creates about a 7% difference in the radiant heat the Earth receives. Therefore, for the Northern Hemisphere, the difference should warm our winters and cool our summers.
But in reality, the superiority of large landmasses in the Northern Hemisphere works just the opposite; It generally makes our winters colder and our summers hotter than in the Southern Hemisphere.
Interestingly enough, if it were us it would be a much different story. Anthem. Compared to our nearly circular orbit, the Red Planet’s orbit is noticeably more eccentric (elliptical). When Mars reaches aphelion, it receives only 69% as much sunlight as at perihelion. This creates a seasonal asymmetry; The southern hemisphere of Mars always experiences greater extremes between summer and winter than the northern hemisphere.
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After August 6, ‘late becomes early’
After the sun reaches the solstice, it will begin to migrate southward and the amount of daylight in the Northern Hemisphere will begin to decrease. Consider this: After June 20, day length will not start increasing again until three days before Christmas. But actually, if you think about it, the sun arcs high in the sky and the length of daylight has been quite long since mid-May. And in the coming days and weeks, the lowering of the sun’s path across the sky and the reduction of daylight hours will be quite mild, at least initially.
August 1 is marked as Lammas Day in some Christian calendars; Its name derives from the Old English word “loaf mass”, as this date was once celebrated as a harvest festival and was traditionally considered the middle of summer. But in reality, the midpoint of summer (exactly the moment between the summer solstice and the autumnal equinox in 2024) won’t occur until August 6 at 12:47 a.m. EDT (1647 GMT). That day, as seen from Boston, the sun will set at 19:56, and the loss of daylight since June 21 will be only 63 minutes.
However, the effects of the sun’s direct rays shifting southwards become much more evident in the second half of summer. In fact, when fall officially arrives on September 22, the sun will set well before 7 p.m. for Bostonians (6:41 p.m.), while the length of daylight will have been shortened by more than two hours (two hours and 6:41 p.m.). Exactly 6 minutes since August 6th.
Baseball Hall of Famer Yogi Berra played mostly as a catcher for the Yankees. However, he occasionally played left field and said he did not care about the outfield except in August and September. This time of year, the shadows on the ballpark in the afternoons grew longer, making it increasingly difficult to see a baseball coming toward him. The Yogi might not have been able to explain the science of why the sun’s altitude decreases so noticeably in the second half of summer, but he managed – as only the Yogi can – to sum it all up in a simple Yogicism: “It gets late and early there.”
Joe Rao is an instructor and visiting professor in New York Hayden Planetarium. writes about astronomy Natural History magazine, Farmer’s Almanac and other publications.