Universe
Introduction to Universe
The universe is a huge collection of all the heavenly bodies including galaxies, stars, constellations, planets, satellites, asteroids, comets, etc., including matter, heat, and light around us.
The branch of science dealing with the study of the universe and its components is called astronomy.
Our Earth is a part of the Universe. It is one of the eight planets in the Solar System, which lies in the Milky Way galaxy.
Importance of Gravitational Force in the Universe
As discussed in the chapter Force and Motion, any two bodies possessing mass attract each other with a force of gravitation. Both bodies attract each other with equal force. However, the effect is dominant on bodies with comparatively smaller masses.
Let us consider Earth, the Sun, and the Moon. The Sun is comparatively very much heavier than the Earth. The same applies to the Earth and the Moon. Due to the heavier masses of the Sun and the Earth, the resultant effect is dominant in the Earth (Sun-Earth) and Moon (Earth-Moon) systems, respectively.
The Earth rotates about its axis and revolves around the Sun in a fixed orbit due to the Sun’s gravitational attraction on the Earth. Similarly, the Moon rotates about its axis and revolves around the Earth in a fixed orbit due to the Earth’s gravitational attraction on the Moon. This idea applies to every body in the universe. Hence, the gravitational force plays a significant role in the existence and sustainability of the universe.
Study of the Universe
Big-bang theory
The Big-bang theory explains the formation and expansion of the universe. According to this theory, around 13.7 billion years ago the entire universe was condensed at a single point of infinite denseness and heat. This highly dense and extremely hot mass exploded and scattered all over. Thus galaxies, stars, planets, etc were formed.
Hubble’s study
Our universe is constantly expanding. Its end cannot be determined. This suggests that either new bodies are being created in regular duration or the existing bodies are moving farther apart.