Gravitation, or gravity, is a property possessed by all bodies and objects, because gravity is an inherent property of matter (what it is). The essence of the phenomenon of gravitation is that all bodies attract other bodies. For example, the Earth attracts everything that it is and that is why any item that does not have support, falls to the Ground. Thanks to gravity, we can walk on the Ground and not fly off into space. If there was no gravity, then all the water splashed out would be out of the oceans and the air would fly away into space.
The earth attracts and the moon, which otherwise has long since flown away.
Why the Moon does not fall to the Ground? And she would have fallen if she stood on the spot! The moon does not fall to Earth because constantly moving - revolves around the Earth.
Why we do not notice the force of gravity in everyday life, if all bodies attract each other? And the fact that gravity is a very weak interaction. It depends on two factors: the mass of the objects and the distance between them. The smaller the mass of the object, the weaker its gravitational force. Therefore, for bodies with small mass, it's just invisible. Even the attraction of such a large object as mount Everest is only 0.001% of the earth's gravitational pull. Mutual attraction between two people of average weight when the distance between them is 1 meter less than 0.03 milligrams.
Now when talking about planets and stars, their force of gravity is already very high, because they are in the millions and billions of times more than we are and what surrounds us. That is why the button, cut off from the coat, is attracted to a man, and falls to the ground, although it is closer to the button than the earth because the mass of the Earth is much greater than the mass of the person.
The dependence of the gravitational forces from a distance is that the farther the objects from each other, the weaker they are attracted to each other.
The law of gravitation discovered by sir Isaac Newton, English physicist, mathematician and astronomer. He first thought, and then proved that the reason that causes the fall of a stone to the Ground, the movement of the moon around the Earth and the planets around the Sun, the same is the gravitational force acting between any two bodies in the Universe.
Newton told that to the discovery of the law of universal gravitation pushed his observation of the Apple that fell from the branch, when he walked through the garden. And in this time he worked on the laws of motion, and already knew that Apple fell under the influence of Earth's gravity. He also knew that the Moon is not just hanging in the sky, and revolves in its orbit around the Earth, and therefore, it affects some force that keeps her from, so that it fell from orbit and flew into outer space. Then he came to me that perhaps this is one and the same force that makes an Apple fall to the ground, and the moon to stay in earth orbit.
The significance of this discovery for mankind is enormous. With this law astronomers with great accuracy determine the position of celestial bodies in the sky for many decades and calculate their trajectories. The law of gravity is used in the calculations of the motion of artificial satellites and interplanetary robotic spacecraft. Using the law of universal gravitation is possible to calculate the mass of the planets and their satellites. The law of universal gravitation explains phenomena such as the tides.
But the most striking example of the role of law for science is the history of the discovery of the planet Neptune. In 1781, the English astronomer William Herschel discovered the planet Uranus. Was calculated its orbit and made a table of the provisions of this planet for many years to come. However, inspection of this table showed that the Uranium is not moving exactly as it was designed. Scientists have suggested that the deviation in the motion of Uranus caused by the attraction of the unknown planets are from the Sun even further than Uranium. Knowing deviations from the calculated trajectory, the Englishman Adams and the French Laverie, using the law of universal gravitation, calculated the position of this planet in the sky. Adams had finished the calculations, but the observers, which he reported their results, do not hurry to check. Meanwhile, Laverie, after calculation, pointed to the German astronomer Galle place where you should look for an unknown planet. On the first evening, September 28, 1846, Galle, pointing the telescope at a specified location, discovered a new planet! It was called Neptune. It was the first planet that was not discovered during observations of the sky, and as a result of mathematical calculations (as they say, "tip"). Similarly, in 1930, Pluto was discovered.