As winter gets underway here in North America, you may notice we don’t feel the sun’s rays for quite as many hours as we did in fall and summer.

Vivienne Baldassare.

To find out why this happens, I talked with my friend Vivienne Baldassare, an astronomer at Washington State University.

“Earth isn’t perfectly straight up and down,” Baldassare said. “It’s a bit tilted on its axis, more like a spinning top.”

The top half of the planet, which is known as the Northern Hemisphere, is tilted more toward the sun when it is summertime. But when it’s wintertime, that means Earth’s Northern Hemisphere is tilted away from the sun. This can make the days feel shorter, and the shortest day of the year is just around the corner.

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Ask Dr. Universe