Summer Solstice 2024: Why It's the Longest Day of the Year

19 Jun 2024

The New York Times

Science|Get Ready for the Longest Day of the Year in the Northern Hemisphere

https://www.nytimes.com/article/summer-solstice-2024.html

Summer solstice 2024 - Figure 1 — Photo The New York Times

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Get Ready for the Longest Day of the Year in the Northern Hemisphere

We have Earth’s off-kilter tilt to thank for the summer solstice, as well as the different seasons.

A gathering at Stonehenge to celebrate the summer solstice near Salisbury, England, on June 21, 2023.Credit...Kin Cheung/Associated Press

June 19, 2024, 5:04 a.m. ET

On Thursday, everyone in the northern half of our planet will experience the summer solstice. It’ll be the longest day of the year north of the Equator, and it is the scientific start of summer.

Earth has a solstice every six months, in June and in December. Leading up to the summer solstice, the sun appears in a higher spot in the sky at the same time each day until it reaches its maximum point.

After the summer solstice, the days will get shorter. The sun will appear lower in the sky each day until the winter solstice, on Dec. 21.

What time is the summer solstice this year?

According to the National Weather Service, the summer solstice will occur on Thursday at 4:51 p.m. Eastern time. This is moment during the day when the sun reaches its most northern point in the sky during the year.

Why do we have solstices?

The sun’s height in the sky each day changes because Earth spins on an axis that is tilted 23.5 degrees away from vertical. This means that depending on the time of year the hemispheres lean either toward or away from the sun.

This is what gives Earth its seasons: When the northern half of the planet leans toward the sun, it experiences summer; at the same time, the southern half of the planet leans away from the sun, and is in winter. It is a mystery why Earth is angled this way, though some astronomers believe that its tilt paved the way for life to exist.

In the Northern Hemisphere, the summer solstice happens when Earth’s tilt toward the sun is greatest. Despite this, the hottest temperatures of the year usually occur a few weeks later, in July or August, because it takes time for the sun’s rays to warm our planet.

Do other planets in our solar system have solstices?

Any planet that is tilted will have solstices. According to NASA, every planet in our solar system has an axial tilt, but some are more pronounced than others.

Venus and Jupiter have only slight leans, around 3 degrees, while Mercury, at 0.03 degrees, is barely slanted at all. On the other hand, Uranus is oriented a whopping 97.8 degrees from vertical, causing one of its poles to point directly at the sun at times. That extreme tilt causes it to have some of the most dramatic seasons in our solar system.

Saturn and Neptune both have tilts close to Earth’s. So does Mars, at 25.2 degrees, although the red planet’s tilt has shifted dramatically over millions of years.

How do people celebrate the summer solstice?

Every year, people around the world ring in the June solstice with midsummer bonfires, festivals and — for those living above the Arctic Circle — midnight sun celebrations. At the other end of the world, scientists living in Antarctica throw their annual midwinter feast to commemorate the longest, darkest night on the continent.

Others travel to ancient ruins, like Stonehenge in England or the Temple of the Sun in Peru, to greet the solstice sun the way ancient peoples once did.

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