The Earth revolves around the sun at a speed of about 67,100 miles per hour. One whole orbit or revolution around the sun takes approximately 365.25 days, which comes out to a year. The extra 0.25 day is accounted in the extra day on leap years every 4 years.
The Earth's axis is tilted slightly, meaning part of the planet is closer to the sun and part of it is farther away at any given time. The actual distance to the sun also changes throughout the year, from a high of 94,509,130 miles around July 4th to a low of 91,402,505 miles around January 3rd. Because the Earth tilts towards the Southern Hemisphere in January , it means that the Southern Hemisphere gets slightly more solar energy than the Northern Hemisphere over the whole year.
The Earth's rotation around the sun and its tilt also produce the seasonal variations in the weather. As the Northern Hemisphere tilts towards the sun, it experiences the warmer temperatures of summer. At the same time, the Southern Hemisphere is tilted away from the sun and experiences winter.Learn more about Earth Science