Summer officially begins in the Northern Hemisphere today (June 20), marking the longest day of the year.
During the summer solstice, also known as the June solstice, the sun reaches its highest and northernmost point in the sky. It marks the beginning of the summer season in the Northern Hemisphere and winter in the Southern Hemisphere, with the Northern Hemisphere receiving the most daylight hours of the year, and the Southern Hemisphere receiving the least.
You can calculate how many hours of daylight you'll receive during the June solstice using The Farmer's Almanac Sunrise and Sunset Calculator. Those located above the Arctic Circle will experience the longest day. There, the sun doesn't set below the horizon for several weeks or even months over the summer due to the phenomenon known as the midnight sun.
Related: The sun's magnetic field is about to flip. Here's what to expect.
This year the summer solstice officially occurs at 4:51 p.m. EDT (2051 GMT,) it will be followed by a full Strawberry Moon one day later on June 21. The moon will reach its full phase at 9:08 p.m. EDT (or 01:08 GMT on Saturday, June 22), but will still appear full the night before and after its peak to the casual stargazer. It will shine near the stars of the constellation Sagittarius, the Archer.
What causes the June solstice?
We owe the June solstice, along with the seasons to Earth's tilt as it orbits the sun. Without it, both the Northern and Southern Hemispheres would receive equal light throughout the year.
As Earth orbits the sun, the axial tilt of 23.44° causes one hemisphere to be tilted toward the sun for half of the year and the other for the second half. During the June solstice the Northern Hemisphere is most tilted towards the sun whereas the Southern Hemisphere is tilted away.
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—When is the Winter Solstice and what happens?
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— Stonehenge's summer solstice orientation is seen in monuments all over the UK in amazing photos
The solstices also do not occur on the same day every year because the astronomical year is 365.25 days long. As such, the summer solstice for the Northern Hemisphere currently shifts between June 20, 21 and 22. The summer solstice does, however, occur at the same time for every country. This means the exact moment of summer solstice can occur in the middle of the night for some people and the middle of the day for others.
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Daisy Dobrijevic
Reference Editor
Daisy Dobrijevic joined Space.com in February 2022 having previously worked for our sister publication All About Space magazine as a staff writer. Before joining us, Daisy completed an editorial internship with the BBC Sky at Night Magazine and worked at the National Space Centre in Leicester, U.K., where she enjoyed communicating space science to the public. In 2021, Daisy completed a PhD in plant physiology and also holds a Master's in Environmental Science, she is currently based in Nottingham, U.K. Daisy is passionate about all things space, with a penchant for solar activity and space weather. She has a strong interest in astrotourism and loves nothing more than a good northern lights chase!
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2 CommentsComment from the forums
LBJay Did days get longer than 24hrs?
I think she means the longest period of daylight.
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Unclear Engineer Yes, she means the longest period of daylight.
But, Earth's actual solar day length is not set at exactly 24 hours. Because the Earth has a slightly elliptical orbit, it moves faster when closer to the Sun and slower when farther away. But, it rotates at a pretty constant rate. So, the extra amount of rotation that the Earth needs to do to get back to solar noon on the same point on its surface varies between Earth's perihelion and aphelion. On the other hand, a sidereal day, which measures the amount of Earth's rotation against distant stars, remains the same over the year, and is shorter than 24 hours.
See https://lco.global/spacebook/sky/sidereal-time/
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