The Earth circles the sun while revolving on its axis. The Earth takes little more than 365 days to complete its orbit around the sun. Other planets' orbital times differ. Mercury takes only 87 days to round the sun, but Jupiter takes 12 years. Saturn takes 30 years, and Uranus takes 84 years.
Earth's average distance from the sun is about 150 million km (93 million miles). At this distance, a planet travels around the sun in approximately 678 days. But because of gravitational interactions with other objects, the amount of time it takes for a planet to travel through its orbit varies.
For example, if Earth had no other companions except for the moon, then its year would be about 365 days long. But because of tidal forces, the water of the oceans pulls on Earth's surface, causing it to bulge. This extra load of water presses against Earth's core, which causes it to contract, thus releasing some of that loaded water back into the ocean. This process, known as oceanic tides, occurs every day and night for all oceans across Earth. Tides affect what we can see from space; they are responsible for generating clouds, providing wind energy, and even creating climate conditions such as ice shelves and sea marshes.
When a planet reaches perihelion, or the closest point to the sun, more solar radiation strikes it.
This is due to Mercury's spin around its axis lasting 59 days and its orbit around the Sun taking 88 days. Surprisingly, 59 is precisely two-thirds of 88. This is not by coincidence; it is a result of Mercury's gravitational field being affected by the Sun's gravitational field. The closer together they are, the more their individual fields influence each other.
If Mercury were in exactly circular orbit around the Sun, then its axis would also be fixed in direction, so that we could say that it has no rotation. But because its orbit is slightly elliptical, its axis does rotate about its center of mass once every 52 days or so. This means that at any given time, half of Mercury is facing away from the Sun, while the other half is darkened over.
This is why Mercury takes 87.9 days to orbit the Sun; this is also why it appears to move across the sky from east to west; this is also why it never gets brighter than the moon during part of its orbit.
Mercury is actually orbiting the Sun twice for every single orbit it makes around it, once when viewing it from above Earth's atmosphere and again when viewed from within it. Because of this orbital double-pass, only parts of Mercury's surface are ever illuminated when seen from Earth.
Due to this reason, only certain parts of Mercury can be seen from Earth.
One point to ponder One full rotation of the Earth around the sun takes 365 days and 5 hours. The plane on which the Earth circles the Sun is known as the ecliptic. The Earth's orbit around the Sun is not a complete circle. Instead, it is an ellipse with one major axis of about 4040 miles (6440 km) and one minor axis of about 6260 miles (9800 km). The average distance between the Earth and the Sun is about 150 million miles (240 million km), so approximately half the time the Earth is away from the Sun, it is dark and cold, and half the time it is light and hot.
Why does the Earth go around the Sun? It is called "solar system dynamics". Our planet is going through a natural process called "orbital decay", which means that its speed decreases due to gravitational forces from Jupiter, Venus, the Earth, and Uranus. If this decay is not counteracted by some other force, then eventually the Earth would be destroyed. This has not happened yet because of the Earth's high mass relative to the rest of the solar system.
When you look up at the night sky, you are seeing everything that has ever been seen on Earth at any given moment. Because the Earth goes around the Sun, we get a new view every day!
It takes 940 million kilometers to travel once around Earth's orbit in a route around the Sun. [+] This is why our day is longer than the time necessary to spin a full 360 degrees, which is 23 hours and 56 minutes. Because that extra spin takes 235.91 seconds, our solar day is usually 24 hours long. However, due to certain factors such as the presence of other planets or stars, this day can be longer or shorter.
Earth's orbit is not exactly circular, but rather elliptical, with its major axis pointing towards the center of the Solar System out to about 95% of Earth's orbital radius. Therefore, if we were looking down on Earth from beyond planet Mars, we would see it pass through the disk of sunlight each day, with parts of the planet illuminated by morning sunlight and other parts illuminated by sunset. But because no part of Earth is directly facing the Sun at any given moment, all points on the surface experience an equal amount of darkness during the night.
It takes 365.25 days for Earth to complete one rotation on its axis. But because Earth's orbit is not perfectly circular, but rather elliptical, with its major axis pointing towards the center of the Solar System out to about 95% of Earth's orbital radius, there are times when Earth is closer to the Sun and experiences more sunlight than others.