Gravity is precisely defined as a pulling force; it pulls objects (matter) towards it. The intensity of force is directly proportional to the quantity of matter, so the things composed of more matter tend to be pulled with greater intensity of force. The mass of any object is the fundamental unit being used to measure the quantity of matter it that object. Therefore, the more heavy and matter in the object is, the higher gravitational pull will it put forth. Earth exerts a pulling force on the objects (Human beings) that move on its surface and as a result it pulls them back. As a matter of fact, the mass of earth is many times more than that of human beings so the pull from any walking individual is not significant enough to mobilize the Earth .On the other hand, the pulling impact of earth is strong enough to fall any walking individual flat. Gravity not only depends on the mass but it also largely depends on the distance, means how far an individual is from something. This is the reason why human beings are stuck to earth, rather being pulled away by Sun which is many times larger than the gravitational pull of the earth .
Gravity is considered as one of primary forces and helps in determining the weight of any object. The concept of gravity can be elaborated as, if an individual tries to examine his weight on a weighing machine than the scale reading indicates the amount of gravity being applied on his body. The universal formula for finding weight is: W=mg (w stands for weight, m for mass and g for gravity). The value of gravity is constant on the surface of Earth and it precisely taken as 9.8m/s2 .
Previously, scientists were of the view that massive objects tend to accelerate faster toward the ground. Recent researches and experiments have openly negated this assumption. The reason behind slow fall of a feather compared to a ball is due to the impact of resistance caused by air. The air resistance imposes its affect in direction opposite to that of gravitational pull. The renowned physicians, Isaac Newton put forwarded his famous Universal Law of Gravitation in 1680’s, and he stated in this theory that gravity exerts it pull on matters and it depends on mass as well as distance. Every entity on this universe exerts a pull on other entity, and this pull is proportional to product of masses (of both the entities) and inversely proportional to the square distance between both the entities
. Fg = G (m1 ∙ m2) / r2
- Fg stands for gravitational force
- m1 and m2 are the masses of both entities
- r stands for the distance between the entities
- G stands for universal gravitational constant
Newton’s equation has been proved to be very instrumental in finding and predicting the behavior of the solar system. The Newton’s work got published in the year 1687, and it was considered as the best possible elaboration and explanation. Later on, Einstein put forth the theory of relativity in the year 1915, he narrated that gravity is not merely a force; instead it is the outcome of the matter warps space –time. One of the assumption given by his theory is that light tend to bend around heavy object .
Technically, it is believed that gravity exists everywhere; it is gravity that provides the path to the orbits of the revolving planets of solar systems and also to galaxies. The source of gravity for the entire solar system is sun, it reaches everywhere and it is so powerful that it goes beyond the solar system. Gravity plays a pivotal role in ensuring the correct orbital shape and rotation of planets. The artificial satellite and the moon are under the influence of the gravity of earth and it keeps them in their designated orbits. It is an established fact that the influence or intensity of gravity decreases as the distance increases, so it is quite likely to have lesser influence of gravity at some far away point . The weightlessness experienced by the astronauts is not backed by the fact that they are at some far point. The fact is, astronauts tend to feel weightlessness is due to their location in contrast to that of spaceship. On the surface of earth humans feel weight because of the pulling gravitational effect that pulls them down, whereas ground prevents them from falling. Humans are being pressed against the ground so therefore don’t feel weightlessness. Any spaceship orbiting around the earth is slowly and gradually falling to earth. Therefore, astronauts and the spaceship are falling at almost the same speed. The astronauts don’t face any kind of pressing so they subject to weightlessness phenomena .
Among all other forces that naturally exist, gravity has been considered as the only universal one. Gravity affects and is being affected by all energy carrying objects and is in close contact with the shape of space time. The universal facet of gravity is clearly understood by the fundamental equation used for gravity, as it establishes very intimate resemblance with that of hydrodynamics and thermodynamics laws. A justified explanation of this fact has not been provided so far by the scientists. Gravity governs at very larger distances on the other hand it is weak at smaller readings. In reality, the fundamental laws of gravity have been experimented up to distance of millimeters. Scientists have revealed this fact that it is very difficult to combine gravity with the mechanism of quantum as compared to any other force that naturally exists. The struggle to combine gravity at microscopic scale with other natural forces is not practically possible. This approach may tend to causes many problems and will lead to uncountable puzzles and unsolved paradoxes. String theory has been successful in solving these to a certain limit, but not completely. It is still in process to learn about the solutions given by string theory .Many of the physicians strongly believed that the geometry of space time and gravity are at the emerging end. The developments related to string theory have shown numerous indications in solving all the problems. The most important clues come from ads/CFT and in more general term the open or close correspondence. This connection may lead to a certain level of duality between theories encompassing gravity and also those without gravity. Moreover, it proves that gravity can come out from as small as microscopic explanation that even have no idea about its presence .The universal nature of gravity strongly supports the idea that its presence needs be to understood with the help of general set of principle. These principles should be completely independent of any peculiar detail of the basic microscopic theory .
Despite large number of attempts in modern physics through theoretical models as well as practical experiments, the physicists are unable to give any final conclusion on the nature of gravity. There are seven major mysteries about gravity that need further research. The present models of physics including quantum mechanics and sting theories are not sufficient to describe the exact behavior of gravity. The major seven mysteries of gravity which are still unsolved are mentioned in subsequent paragraphs .
The first and the primary unresolved issue is regarding the nature of gravity. Gravity is considered among the four fundamental natures; however, it is undefined by any theoretical of practical model unlike other four fundamental forces. Gravity was initially defined by Newton which was considered final until Einstein changed it and its still not final. The second unresolved issue with the gravity is that the gravity has only one direction. The other forces and natural phenomena have two sides/directions. Like magnetic poles but gravity can only pull and never pushes. Scientists and physicists are unable to detect any object in the vastness of universe that could prove existence of gravitational push phenomena.
The third mystery about gravity is that the gravity is a very weak force when compared to other three fundamental forces in relation to the object size; however, this weak level of gravity can be easily detected in the vastness of universe. Gravity is undetected at small objects even at little distances but can be observed at larger distances for large objects. The fourth unresolved issue with gravity is that it has such a fine tuned value that even a slight change in the value of gravity would disrupt the systematic existence of the universe and all the objects within it including galaxies, stars, and planets.
The fifth mystery about gravity is that it is a basic necessity for existence of life. Although humans have gone to space and experienced zero gravity but it is not possible to live a healthy life without gravity. Humans and animals suffer from various medical problems including weakness of bones in absence of gravity. The sixth mystery of gravity is that despite high level of technologies, humans are still unable to make any antigravity material. Antigravity is a dream to be achieved by humans and there is still no clear indication that humans would be able to achieve it in future or not.
The seventh and final mystery of gravity is that, when gravity is explained through modern theories including relativity and quantum mechanics, a number of issues and paradoxes start to appear which remain unresolved. All these mysteries of gravity make the concept of gravity a much complex one as compared to what is presented through classical physics.
Gravity is experienced by everyone and is considered a simple force occurring in nature. However, it is not at all as simple as it seems. The classical concept of gravity as defined by Isaac Newton has been successful in the past but after various advancements including introduction of theory of relativity and quantum mechanics, gravity has become a serious topic of debate among physicists. Once gravity has been fully understood by physicists, it may become possible for us to make antigravity material and overcome or generate gravity wherever needed.
Works Cited
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Verlinde, Erik. On the Origin of Gravity and the Laws of Newton. Thesis. Amsterdam: Institute for Theoretical Physics University of Amsterdam, 2010.
