When it comes to Earth’s orbit around the Sun, the more things change – well, the more things change. Over the course of a year, our distance from the Sun varies by about three million miles. But that’s changing. And we’re farthest from the Sun in early July – but that’s changing, too.

The farthest point from the Sun is known as aphelion – from Greek words that mean “far from the Sun.” And we’ll reach that point on Thursday. Earth will receive about seven percent less sunlight than it does when we’re closest to the Sun, in early January.

Earth’s orbit around the Sun is elliptical – like a slightly flattened circle. But the exact shape changes over a period of about a hundred thousand years. Right now, the orbit is getting a little more circular, so there’ll be a smaller change in the distance to the Sun. After that, it’ll get a lot more stretched out. That will cause much bigger changes in Earth’s climate between the closest and farthest points.

The timing of those points also changes. About 800 years ago, aphelion happened around the time of the summer solstice in the northern hemisphere.

Now, it’s shifted a couple of weeks later. And the shift is continuing. So, about 4400 years from now, aphelion will happen at the fall equinox, in September. It’ll return to its current spot on the calendar more than 20,000 years from now.

Tomorrow: A bright star that looks like an egg.

Script by Damond Benningfield