On Thursday, everyone in the northern half of the planet will mark the summer solstice, the longest day of the year north of the equator and the scientific start of summer.
Earth has solstices every six months, in June and December. Leading up to the summer solstice, the Sun appears higher in the sky at the same time each day, reaching its maximum point.
After the summer solstice, the days get shorter and the sun appears lower in the sky every day until the winter solstice on December 21st.
When is the summer solstice this year?
According to the National Weather Service, the summer solstice will occur at 4:51 p.m. ET on Thursday, the moment during the day when the sun reaches its northernmost point in the sky at any given time of the year.
Why are there solstices?
Because the Earth rotates on an axis tilted 23.5 degrees from vertical, the Sun’s height in the sky changes each day, meaning that each hemisphere moves closer to or further from the Sun depending on the season.
This gives Earth its seasons: when the northern half of the Earth tilts towards the Sun, it’s summer, and at the same time, when the southern half of the Earth moves away from the Sun, it’s winter. Why Earth is tilted this way is a mystery, but some astronomers think that Earth’s tilt paved the way for life to exist.
In the Northern Hemisphere, the summer solstice occurs when the Earth is most tilted towards the Sun. Nevertheless, the warmest temperature of the year usually occurs a few weeks later, in July or August, because it takes longer for the Sun’s rays to warm the Earth.
Do other planets in the solar system also have solstices?
Every tilted planet has a solstice. According to NASA, every planet in the solar system has an axial tilt, but the tilt varies greatly from planet to planet.
Venus and Jupiter are tilted by only about 3 degrees, while Mercury is barely tilted at 0.03 degrees. Uranus, on the other hand, is tilted a whopping 97.8 degrees from vertical, with one of its poles sometimes pointing directly at the Sun. This extreme tilt causes Uranus to experience some of the most dramatic seasons in the solar system.
Both Saturn and Neptune have tilts similar to Earth’s, and Mars is also close to Earth at 25.2 degrees, but the Red Planet’s tilt has changed dramatically over millions of years.
How do people celebrate the summer solstice?
Every year people all over the world mark the summer solstice with bonfires, festivals and, for those living north of the Arctic Circle, festivals celebrating the midnight sun. Meanwhile, on the other side of the world, scientists living in Antarctica hold their annual midwinter feast to mark the continent’s longest, darkest night.
Some people visit ancient ruins, such as Stonehenge in England or the Temple of the Sun in Peru, to welcome the sun on the summer solstice, just as the ancients did.
