• Ahmed Emad Hassab Elnabi

Gravitational Force

“’You may hate gravity, but gravity doesn’t care.’ Clayton Christensen”. This Harvard teacher was directing this quotation to students like me because it is a force that cannot be viewed. Gravity is a field force exerted by an object to attract another object towards its center. In a simplified manner, it is an intangible, non-contact force that cannot be seen, but is existent between all objects. Gravitational force in a mathematical perspective is the mass of an object multiplied by gravitational acceleration. It is one of the fundamental forces of the universe that maintains planets, solar systems and galaxies. In the last couple of centuries, gravity became understood through Galileo, Brahe, Kepler, Newton and Einstein.

Before the last 300 years, some only superficially understood gravity and others neglected the concept of having a field. In ancient times, civilizations believed that the skies and systems were held by divine power. Over they years, loads of scientists and philosophers tried to explain such a ‘magical’ phenomenon. In 1610, Galileo created a modern telescope. He used it to observe different planets’ behaviors. He focused on Earth and Venus; consequently he realized that they both revolve around the sun in a similar pattern. Therefore, he concluded that there’s a force that causes this spectacle. In the same time existed Kepler and Brahe. Kepler used Brahe’s astronomical data to conclude that planets revolve around the sun in an elliptical motion and that Earth has the same orbits around the sun; thus, he discovered that gravity creates seasons. Then, came the father of physics and creator of laws of motion, Isaac Newton. He was one of the first to explain the theory of mutual interaction, through his law of Universal Gravitation. It states that any and every two bodies in the universe attract each other with a force directly proportional to their masses and inversely proportion to the square of the distance between them. Thus objects like Newton’s apple is pulled to the earth and vice versa; the earth and planets are pulled towards the sun and vice versa. Finally, Albert Einstein, who is the most renounced genius, proposed a new theory. He said that gravity is the result of space and time being bent, general theory of relativity. He also theorized that enormous masses alter space and time because they deflect light, thus creating gravity. Skeptics denounced his theory, but time proved this theory right when astronauts went to space and found out that a clock is quicker away from earth.

There are many misconceptions about gravity because there are many different explanations to it. First, people think that gravitational force doesn’t exist between humans, but it does exist between every object in the universe. However, the gravitational pull by earth is much stronger than the force exerted by humans because of its huge mass. Second, some thinks that gravity occurs through a mixture of gases, the air. However, gravity occurs between planets and suns, where there is no air, vacuum. Third some think that gravitational acceleration (a=f/m) in free-fall decreases because of the force of gravity of other objects. However, air pressure causes this occurrence but gravitational acceleration is constant at 9.81 m/s. Fourth, people claim that we are supposed to be pulled to mars or the moon also. On the other hand, they don’t take into consideration the factor of distance and that earth is we are too far from the moon or mars. Fifth, some say that there is no gravitational force between Pluto and Earth. This is not true because gravitational force exists between all the objects in the universe. No matter how minute it can be, it is never zero. Sixth, a person might claim that his mass changes on the moon, but mass is constant; it is weight that changes depending on the gravitational pull. Seventh, one would think that we must be pulled to the Earth’s core since that is stated in Newton’s law of universal gravity. However, Newton also said in his third law that the Earth’s floor has an equal and opposing force to the gravitational force. Finally, one could claim that there is no gravitational force exerted on bacteria since they float. This statement is false because its mass is insignificant, gravitational force exerted by Earth on them is very small that it seemingly doesn’t affect them.

Gravity has a very strange nature since Isaac Newton and Albert Einstien explained it in different ways. They both agreed on some fundamentals. First of all, Gravity is a field force because it is a contact force that occurs without objects physically touching. For example, the Earth pulls a ball towards the ground without touching it. Moreover, they both agreed that gravity is of extreme importance, in which it holds planets in solar systems and solar systems in galaxies. Isaac Newton theorized that gravity is the tendency of an object to be pulled towards the center of another object. Newton proposed the equation that the force of gravity equates to the mass of an object multiplied by the gravitational acceleration. On the other hand, Albert Einstein explained gravity as the bend in space and time created by a huge mass, so other objects that come near, fall in the dip or orbit in one of the levels of the dip. He proposed the equation of the gravitational force equates to the gravitational constant multiplied by mass of object one times the mass of object two, all divided by the square of the radius.

One other point that all scientists that understood gravity agreed on is that the range of gravity is infinite. There are many misconceptions about its range because the thought of infinite is tough for all humans. However, there is a force of gravity between any two masses. For example gravity exists on an atomic level and on a intergalactic level.

There is an infinite amount of uses of gravity. On Earth, it keeps humans, animals and plants in the atmosphere stuck to the Earth’s surface. Also, gravity plays an important role in maintaining our spine’s shape because its God given strength is just right to neither make the spine neither rough nor soft. Furthermore, gravity keeps the Earth at a certain distance form the sun, so we would have suitable weather conditions to survive. Also, it pulls rain and flowing water downwards for us to drink water. Finally, it has a huge effect on the macro-organisms. Gravity keeps moons around their planets, planets around their stars; it keeps all systems in their galaxies and keeps galaxies in their clusters.

Therefore, we have passed through many stages to understand such a strange phenomenon. Many scientists and thinkers had their say like Newton and Einstein. They proposed different theories but all had the same fundamental, which is that gravity observed everywhere we look; it can be clearly seen on a macro-level, but it is existent between everything in the universe. Finally, there are many applications and misconceptions of gravity because of its unbounded nature. As Albert Einstein once said, “Learn from yesterday, live for today, hope for tomorrow. The important thing is not to stop questioning.” This is the scientist’s code, which explains the constant advancements in science, chemistry and physics, and it will infinitely continue as people continue trying to ask the right questions.

Works cited

“Chapter 5.” Cohen Physics 131. N.p.: Cohen, n.d. N. pag. Print. <http://www.esu.edu/physics/cohen/phys131/textbook/cohen_ch5.pdf>

“Gravitational Force.” Gravitational Force. PHY, n.d. Web. 19 Nov.2013. <http://www.phy.syr.edu/courses/tutorials/FreeBody/Gravity/Gravitational.Force.html>.

“History of Gravity.” History of Gravity. WISC, n.d. Web. 19 Nov. 2013. <http://www.physics.wisc.edu/museum/Exhibits-1/Mechanics/GravPit/index_HistGrav-2.html>.

Thompson, Hobbie, and Sarah Havern. “Gravity.” Gravity. Stanford, n.d. Web. 18 Nov. 2013. <http://www.stanford