The summer solstice is today: What you need to know about the longest day of the year

Today is the longest day of the year, also known as the summer solstice.

The summer solstice, which can also be called, midsummer, occurs when a planet's rotational axis or geographical pole on either its Northern or its Southern Hemisphere is most greatly inclined toward the star that it orbits.

The term ‘solstice’ comes from the fact that the Sun appears to stand still. On this day, the Sun's position in the sky at noon does not change much during the solstice and its surrounding days. In 2018, the summer solstice arrived on Thursday, June 21, at 6:07AM EDT, marking the first day of summer in the Northern Hemisphere.

During this time, the North Pole is tilted closest to the sun. In the Southern Hemisphere, it is the opposite, so, the South Pole is tilted farthest from the sun. That is why when it is the summer solstice in the North, it is the winter solstice in the South.

The solstice is also a time for shenanigans at the Stonehenge. On this day, the sun rises behind the Heel Stone, the ancient entrance to the stone circle, and sunlight is channeled into the centre of the monument. Reports suggest that solstices have been celebrated at Stonehenge for thousands of years.

All the planets in our solar system have summer solstices. For example, Mars has a solstice which will occur a few days after Earth’s summer solstice this month. On Uranus, the summer solstice happens once every 84 years. The next one will occur on October 9, 2069.

The shortest day of the year is known as the winter solstice, and occurs between December 20 and 22. In 2018, it will occur on Friday, December 21 respectively.