What is summer solstice?
The summer solstice is the longest day of the year.
That is true for the northern hemisphere on Jun 21. In the
southern hemisphere, their longest day of the year is on Dec
This is because the Earth is rotating around the sun at an
angle. That is the axis of rotation is not perpendicular to the
sun. In Jun, the north axis of the earth rotation is pointing
toward the sun and vice versa in Dec.