The Apple Does Not Fall Far From The Tree…Even In Other Solar Systems

In the year 1666, Isaac Newton had a realization about the universe. By observing an apple fall from a tree, he realized that there must be a force driving the apple towards the Earth. He called this force gravity, and with this realization came other important discoveries theorizing how mass and gravity interact with one another.

Newton’s universal law of gravitation can be described as follows:

  1. Every mass attracts every other mass through its gravity.
  2. The strength of the gravitational force attracting any two objects is directly proportional to the product of their masses.
  3. The strength of gravity between two objects decrease with the square of the distance between their centers (inverse square law.)

These statements can be described mathematically as follows:

F(g) = G * ( (M1 * M2) / d^2 )

where F(g) is the force of gravitational attraction, M1 and M2 are the masses of two objects, and d is the distance between their centers. G represents the gravitational constant, which is 6.67 * 10^-11 m^3 / (kg * s^2).

Additionally, Newton stated that every object in the universe has a gravitational attraction to each other. Some attractions are larger than others due to the masses of the objects and their distances from each other. The term “weight” is a term used to describe the amount of gravitational pull that the Earth has on an object. An object on the moon would weigh less than it does on Earth because the moon is smaller and has less gravitational attraction.

Newton’s theory of gravitation quickly gained respect because it helped to explain both Galileo’s and Kepler’s discoveries. In addition to his discoveries about gravity, he also made several theories relating to motion, which are as follows:

  1. An object in motion tends to stay in motion.
  2. Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration.
  3. Every action has an equal and opposite reaction.

Newton claimed that his theories were universal, and therefore would apply not only to our solar system but to each and every galaxy across space and time. In an article I found on entitled, “Gravitational constant appears universally constant, pulsar study suggests,” astronomers in West Virginia studied a supernova outside of our solar system for 21 years. The supernova orbits a white dwarf and seems to obey Newton’s laws of gravitation and motion. The scientists have concluded from their study of this other solar system that the gravity constant and laws of gravity apply not only to our solar system, but to other solar systems as well, proving Newton’s original idea correct. This connects to what we learned in class because it proves that Newton’s laws have an application in the real world; not only here on Earth but everywhere else in space as well!

Reflection: I thought the article was cool and interesting to read because it mentioned that some scientists theorize that gravity does not behave consistently throughout the universe. The study from the article shows that, as far as we know, it IS consistent throughout the universe. I think it’s remarkable and unbelievable that Newton was able to make these discoveries four hundred years ago with barely any modern technology at all, and the fact that he has yet to be proven wrong is simply awe-inspiring.


Gravity Elsewhere


The sixth conceptual objective, I can apply Newton’s laws of motion and Newton’s law of universal gravitation, has been recently discussed in class. The universally accepted idea of gravity came from Isaac Newton. His inspiration came to him when he saw an apple fall to the ground. He suddenly related this concept to astronomy. The force that holds the moon in orbit around the Earth is gravity. This concept is known as a fact now, but was once a theory. To summarize Newton’s universal law of gravitation, three statements are commonly ¬†used:¬†1.) Every mass attracts every other mass. 2.) The strength of the gravitational force attracting any two objects is directly proportional to the product of their masses. 3.) The strength of gravity between two objects decreases with the square of the distance between their centers. These three statements can be expressed mathematically with the equation: Fg=G(M1M2)/d^2. Newton’s theory explained many other prior discoveries. In order to fully understand Newton’s universal law of gravitation, in class we exercised this concept in the Lecture-Tutorial book. The article I chose, ” How Can Two Moons of Saturn Share the Same Orbit”, discusses the similar orbits of two of Saturn’s moons, Janus and Epimetheus. These two moons share the same orbit. However, these two moons never collide. The speed of a moon in its orbit is mainly determined by its distance from the planet. As discussed in class and in my chosen article, any orbit is a balance between two competing forces, gravity. This concept relates to what we discussed in class, Newton’s law of universal gravitation. Gravity pulls two masses together and the speed of the masses makes them move away from one another. The article then continues to discuss gravity’s role in this scenario. Gravity makes things go faster as they fall. As these two moons approach each other, their speeds begin to change due to gravity, causing the moons to avoid a collision. Gravity ultimately causes the moons to reverse their directions. This phenomenon is rare. Not many instances are known where two large objects share the same orbital path. This article relates to the sixth conceptual objective because it demonstrates Newton’s universal law of gravitation in a real world situation. Newton’s law can even be applied on a different planet. His law is universal and can be displayed all over the universe in many different situations. This article is very comparable to what we exercised in class. The concept of gravity is thoroughly demonstrated and expressed in the article. The article clearly demonstrates Newton’s universal law of gravity and relates it to the orbits of Saturn’s moons. This article and conceptual objective has taught me the universal law of gravitation as well as being able to apply it to real situations. Gravity exists all around us and even in places far away in space. The article I chose was very informative and interesting. After reading this article, my understanding on the sixth conceptual objective was clearified.