Catch the Perihelion, a Once-a-Year Sky Event Happening Tomorrow

Tomorrow (January 4), the earth will reach its perihelion, which is just a fancy term for when this spinning rock of ours is the closest it will get to the sun over the course of the year. Here is everything you should know.

On January 4, the earth will be about 91.4 million miles from the sun, compared to our average distance of about 93 million miles. The earth will also be moving fastest in orbit tomorrow at about 19 miles per hour, which is about 0.6 miles per second faster than when the planet is the furthest from the sun.

Now you may be asking yourself: how exactly does the earth get closer to the sun if it moves around the giant fireball in a circle? The answer is that the earth doesn’t actually move around the sun in a circle; it moves in an ellipse. So in early January, it is at its closest point to the sun (called the perihelion), while it is at its furthest point from the sun (called the aphelion) in early July.

So does this mean anything in terms of your day-to-day life? Not really. While the earth is the closest it gets to the sun, it won’t be very noticeable to any of us. And you almost certainly won’t notice the earth rotating slightly faster either. You don’t need to make any plans to see anything cool in the sky, as it’s mainly just a cool fact to know about the earth’s rotation around the sun.

While it might not make for excellent stargazing, it does, however, have a slight effect on the two hemispheres. Since the northern hemisphere is currently experiencing winter right now, the summer is about five days longer, while the southern hemisphere (which is currently in summer) has the opposite experience, with winter lasting about five days longer due to the perihelion.