Longest day today, shorter nights to follow

New Delhi, June 21: It is the longest day today! Today is summer solstice -- the day when the sun is directly overhead the Tropic of Cancer at noon -- officially marking the first day of the season of summer.

It's the longest "day" of the year, in that we have the most hours of sunlight. That is because the Earth's axis tilts the most towards the Sun at noon, at 1406 hrs to be precise.

A solstice occurs twice a year, whenever the Earth's axis tilts the most toward or away from the sun, causing the sun to be farthest North or South at noon.

During summer, days feel longer because the sun rises early in the morning and sets late at night. When the North Pole of the Earth is tilted toward the sun, those in the Northern hemisphere receive more sunlight and it is summer. As the Earth moves in its orbit, the tilt of the North Pole changes.

When it is tilted away from the sun, it is winter in the Northern hemisphere. In between, we have Autumn and Spring.

So while the day when the Earth's North Pole is tilted closest to the sun is called the summer solstice, occuring on June 21, which is also the longest day (most daylight hours) of the year for people living in the northern hemisphere, the day when the Earth's axis tilts the farthest away from the sun is called the winter solstice that occurs around December 21.

UNI