PARIS: The summer solstice arrives Sunday June 21. Those of us in the Northern Hemisphere know it as the longest day of the year. But how exactly does that work?
Start by imagining the Earth circling around the sun. Now picture a vertical line running through the planet from the North Pole to the South Pole. That’s the Earth’s axis, the line we rotate around once each day.
Here’s the key: The axis doesn’t run straight up and down with respect to the sun. In fact, it’s oriented at a 23.5-degree angle. That means that as the Earth orbits around the sun, sometimes the North Pole is pointing a little away from it and sometimes it’s pointing kind of toward it.
