Earth from space
Credit: NASA photo in the public domain.

This photo of Earth was taken by a NASA satellite in 2002.

Like all planets, Earth has an elliptical orbit

Each of the eight planets orbiting our sun follows a path that is not perfectly circular. The closest that any of them comes to being perfectly circular is Venus. The most elliptical orbit is that of Mercury.[1]

Since the Earth’s orbit varies from being a perfect circle, there is a time each year when it is closest to the sun, called perihelion, and furthest away, called aphelion.[1] Perihelion for Earth occurs each year in early January, most often on January 4th. Aphelion occurs every year in July, most often on July 4th.[2]

The difference might sound vast – the Earth is 3.1 million miles further away from the sun at aphelion, compared with perihelion.[2] The Earth however averages about 93 million miles, so this variance is less than 4% of the overall distance. At aphelion the Earth is about 94.4 million miles (152.1 million km) from our sun. At perihelion it is about 91.3 million miles (147.1 million km) away. [2]

Earth's orbit
Credit: Wikipedia photo, by Gothika, CC BY-SA 3.0.

This is an exaggerated representation of the shape of Earth's orbit. The actual path of Earth's orbit is not as eccentric as what is portrayed. "Periapsis" is the same thing as perihelion, and "Apoapsis" is the same thing as aphelion. In June and December are the soltices, and in March and September are the equinoxes.

Aphelion and perihelion effects on the Earth

The timing of aphelion and perihelion actually slightly moderates the seasons in the Northern Hemisphere, where most of the landmass of Earth is located.

The Earth is furthest away from the sun near the Northern Hemisphere's Summer Solstice, which is when the North Pole is pointed the most toward the sun. The first day of summer in the Northern Hemisphere always on or near June 21st. And the sun is nearest to the Earth close to the Winter Solstice, which is when the North Ple is pointed the furthest away from the sun, every year on or near December 21st.[2]

This has the opposite effect on the Southern Hemisphere, and slightly exaggerates the cold of Antarctica during the dark winter months.[2] Overall however, the Southern Hemisphere’s temperatures are moderated somewhat by the vast amount of ocean water located south of the equator.[3]

Earth as seen from the moon
Credit: Public domain photo, by NASA.

In this photo is every human being alive - with the exception of the crew located on the moon.

Direction of the Earth's orbit and rotation

The Earth takes about 365 1/4 days to orbit the sun, covering a distance of about 585,000,000 miles (940,000,000 km). The math shows that the Earth is traveling upon its orbital path at a speed of about 67,100 miles per hour (108,000 km per hour).[2] This means that a distance equivalent to the diameter of the Earth is covered every seven minutes.

If you were to look down upon the solar system from above Earth’s North Pole, all of the planets would be orbiting at varying speeds in the same direction, counter-clockwise around the sun.[1] However, the planets don’t all rotate or spin in the same direction.[4]

Six of the planets, including Earth, rotate counter-clockwise – again, if looking down on the solar system from above Earth’s North Pole. This causes us to see the sun rise in the east and set in the west.[4]

Venus spins the completely opposite direction, although very slowly. It rotates clockwise, and there is a theory that a few billion years ago it was struck by a large object such as a giant asteroid or comet, and this reversed its spin. On the surface of Venus, the daytime is murky and dark, because of a very thick cloudy atmosphere. But if the sun could be seen, it would rise in the west and set in the east, opposite of Earth.[5]

The planet Uranus doesn't spin either direction, clockwise or counter-clockwise, but is tilted very close to 90 degrees, on its side, and thus rolls sideways. During the course of its orbit each pole faces the sun for more than four decades, creating planetary seasons far different from those of all other planets.[6]