Newton stated that objects that have mass also have gravity and the greater the mass, the more is the gravity. The magnitude of this gravitational force depends on the distance between the objects. The further apart the objects get, the weaker the gravitational force. The magnitude of this force also depends on the masses of the two objects which gives it weight. Greater mass means a greater force. Einstein’s theory of general relativity and gravity explains that mass warps space and time. The greater an object’s mass, the stronger is its gravitational pull. As we know that “There is a force of attraction between any two objects which is directly proportional to the product of their mass of the object and inversely proportional to the distance between them”.
In the equation given by Newton for gravity, the masses are described by the variables m1 and m2 and the distance between the objects in the variable r. The G is the universal gravitational constant with a value of 6.67 x 10-11 Nm2/kg2. Hence, the equation proves that two objects with masses attract each other. The force is exerted on two bodies with definite mass and depends upon the distance between them. The statement is evident when the object is falling towards the Earth. But is it possible for any two bodies with mass lying beside each other?
As we know that the body with higher mass tends to attract the body with lower mass. Now the question is why we don’t feel this gravitational attraction with other objects. Suppose a person (m1) is working on the computer (m1). Since the objects both have mass, there is a gravitational force pulling them together. Using rough approximation for distance and mass, an attractive force of 3 x 10-7 Newtons. But both the objects are placed on the earth’s surface and the earth is having its own gravitational force acting on both bodies. The gravitational force on two bodies lying beside each other is less than the gravitational force between the body and earth. Therefore we do not feel the attraction towards each other. Therefore, this force on both the bodies is fairly close to the force one would feel if a grain of salt on the head. So, the gravitational force acting on these bodies is super tiny.
The planets and gravity in space
Gravity causes every object to pull every other object toward it. Some people think that there is no gravity in space. In fact, a small amount of gravity can be found everywhere in space and it is the same gravity that holds the moon in its orbit around Earth. And not only the moon but all the planets in the universe are revolving around the sun in orbit due to gravity. It is possible for a spacecraft to go far enough from Earth that a person inside would feel very little gravity. But this is not why things float on a spacecraft in orbit. The only difference is the distance between the object and the center of the Earth (the r). So as the distance increases, the gravitational force decreases. The International Space Station orbits Earth at an altitude between 200 and 250 miles have about 90 percent of what it is on the planet’s surface. But, the question is why do astronauts float around in space? They float around when in orbit the “weightless” environment is caused by the orbital motion of the people inside a spacecraft or space station. If the only force acting on a human is the gravitational force, that human feels weightless. Therefore we can say that gravitational force is acting upon the body in the universe. But Newton’s view of gravity didn’t work for some things, like Mercury’s peculiar orbit around the sun. The orbits of planets shift over time, and Mercury’s orbit shifted faster than Newton predicted. so whats the answer for this and how it can be expressed?
Blackhole and universal law of gravitational force
In Newton’s view, all objects exert a force that attracts other objects. The universal law of gravitation worked for predicting the motion of planets as well as objects on Earth. Newton showed that his laws of gravity can explain the observed motions of the moons and planets in the Solar System.
Einstein offered a different view of gravity, instead of exerting an attractive force, he reasoned that each object curves the fabric of space and time around them, forming a well that other objects and even beams of light fall into. This new model showed that the sun curves the space that it distorts the orbits of nearby bodies, including Mercury. In Einstein’s view, Mercury might look like a marble forever circling the bottom of a drain. Einstein’s theory has been confirmed by more than a century of experiments in which the path of light from distant stars was shifted by the sun’s intense gravitation by just the amount he had predicted.
Black holes obey all laws of physics, including the laws of gravity. Their remarkable properties are in fact a direct consequence of gravity. Albert Einstein refined the knowledge of gravity through his theory of general relativity. He first showed, based on the fact that light moves at a fixed speed (671 million miles per hour), that space and time must be connected. Then in 1915, he showed that massive objects distort the four-dimensional space-time continuum and that it is this distortion that we perceive as gravity. Einstein’s and Newton’s theories are nearly identical but for very strong gravitational fields, such as those encountered near black holes, Einstein’s theory predicts many fascinating new phenomena.
At a distance, a black hole is just another body, and Newton’s laws of gravity apply. Objects will feel the gravitational attraction of a black hole and objects can orbit around the black hole. Closer to a black hole Newton’s laws of gravity break down as relativistic effects come into action. Objects orbiting closer to the black hole will be traveling fast enough that relativistic effects such as time dilation will be experienced. Objects getting close to the black hole will experience the effects of General Relativity. Time will slow down and gravitational tidal effects will occur.
So it can be said that the universal law of gravity by Newton is not 100 percent true for all universal objects but yes it does exist. What’s your call on these statements?