Earth makes two simultaneous rotation.The first - a movement around its axis, and the second - in its orbit around the sun.Axis in science is called an imaginary line passing through the center of the globe.Earth's orbit is not circular, but elliptical.
day and night is due to the fact that the Earth rotates on its axis.This one turn and is considered to be for days.Day occurs on the part of the globe which is directly opposite the light, and on the opposite side at this time, as you might guess, night.
It should be noted that the Earth has the ability to orbit at different speeds.The scientists found that the approach to the sun, the speed increases and decreases with the remote.However, the difference is so small that introduced the concept of "mean solar day", which means familiar to us
Turning around its axis 365 full time and the Earth makes a full rotation around the sun in its orbit.It is this turnover is considered to be for "a solar year."The plane in which the earth revolves around the sun, called the ecliptic.
The change of seasons is happening because of the different inclination of the orbit along which moves the earth.The elliptical shape causes the planet to tilt toward the sun at different angles.Consequently, portions of the earth receive different amounts of heat.Most sunlight gets the equator.
summer when the sun reaches the highest point of the ecliptic in the northern hemisphere begins the longest day of the year.In winter, the opposite situation happens, the sun's rays fall on the Earth is not at a right angle, and the most oblique, and then comes the shortest day.
on other planets, time moves differently.For example, Mercury year lasts 178 Earth days, while Pluto - 248 Earth years.