According to the Nebular Hypothesis sun is a cooling and rotating nebula and our planet earth has been formed as a result of solidification of a ring along with eight other such rings thrown by it. Theory of nebular hypothesis was put forward by German philosopher, Kant and French mathematician, Laplace.
But according to the Jeans and Jeffery theory proposed in 1925 two nebulae are involved in the creation of earth. According to this theory a larger nebula came closer to the smaller nebula (sun) and due to gravitational pull a gaseous tide was raised on the surface of the sun. As the nebula came closer the tide increased in size and when the nebula moved away the gaseous tide detached and was like a spindle. When this spindle broke into pieces nine planets of solar system were formed after condensation. The matter detached from the smaller nebula (sun) had an inertial momentum of rotation, so after getting detached from the sun it conserved its momentum (according to the law of conservation of momentum); this explains the rotation of earth and other planets in our solar system.
The period of rotation of earth is 1 day that is 24 hours. The rotation of earth on its own axis is from west to east and it is due to this rotation of earth that all parts of it get sunlight otherwise the part of earth away from the sun would have frozen and the part facing it would have been super hot. Similarly half of earth would have no day and the other half no night.
Curious people have always looked up to astronomers to explain the rotation of all planets. According to astronomers the planets are molecular chunks formed as a result of shock waves sent by a supernova through a cold cloud of molecular hydrogen and have a momentum which they retained even after being detached from the nebula. This state of momentum is clearly supported by the law of conservation of momentum. Under the effects of gravity, over the period of time planets have come close to each other. Due to gravity the particles in momentum are kept restricted on planet surface thus making the planets bulkier and it also leads to gain in momentum of the planets. In this course of action change is to avoid collision.
Earth’s orbital path is not quite a perfect circle but instead is slightly elliptical (oval-shaped) .Its axis of rotation is inclined and makes an angle of 66 ½o with the plane of ecliptic i.e., the plane of orbit of the earth around the sun. Earth’s axis of rotation is inclined (tilted) 23.5° relative to its plane of revolution around the Sun. This inclination of the axis creates the seasons and causes the height of the Sun in the sky at noon to increase and decrease as the seasons change.