The gravity and the weightlessness in the solar system
The solar system
the solar system consists of the Sun ( star ) , Eight planets ( revolving around the Sun in fixed orbits ) , the comets , the asteroids and the moons ( the satellites of the planets ) , It was considered as the center of the universe in the past but now we know that our system is a tiny spot compared to the rest of the universe .
The planets and the other bodies were originated in the solar system since 4600 million years ago , The astronomic system ( the solar system ) extends over 12000 million kilometers in the space .
The Sun is the center of the solar system and it is the dominant body ( star ) in this system as it represents more than 99 % of the total mass of the solar system .
The gravity in the solar system
The English scientist Isaac Newton was the first one who discovered the Earth’s gravitational force when he was sitting under a tree and he found an apple falling down to the ground .
Newton’s law of universal gravitation
There is attraction force between any two bodies , And it is directly proportional to the product of the masses of the two bodies , The attraction force between the two bodies is inversely proportional to the square of the distance between them .
Newton proved that the gravitational force makes the planets revolve around the Sun in fixed orbits , And the matter of each celestial body remains firm , The gravitational force is the force that keeps the continuity of the planets rotating in their orbits around the Sun .
If the gravitational force of a celestial body was strong enough , it will attract the gases towards itself forming an atmosphere around it ( even if it was a planet or a moon ) .
The law of universal gravitation is one of the basic laws of the universe , if there is no attraction force between the Sun and the Earth , The Earth will leave its orbit and float in a random fashion in the space and this leads to the destruction of the Earth .
The gravity keeps the planets in their orbits around the Sun and the moons in their orbits around the planets , when the distance increasing , the effect of gravity decreases ( when the planet moves away from the Sun , The gravity decreases and its movement becomes slower ) .
The continuous force of the Earth’s gravity on our bodies gives us the weight , But when you are inside a lift going downward fast , You feel that you are lighter in weight , If the lift falls ( when the wires are cut ) , you feel weightlessness .
The weightlessness occurs in the spacecraft as the astronauts fall down inside it with the same speed so that they get weightless .