An Overview of Gravity

Many phenomenon in our lives involves gravity. From the simplest example say, keeping stick on the ground to the more complicated ones like the mechanism of global positioning system (GPS) which is link to satellite orbiting the earth. But do you know actually what gravity is? Does it have a physical form? How does gravity work? What are the applications? There are many questions that can be propose and the answers are interesting.

First of all, we all know Newton’s Law, right? The one I am gonna talk about is Newton’s second law which states that the force acting on an object is the product of its acceleration and mass. Sounds simple and straightforward but the fact that there are many implications of this what makes it special. If we observe say a falling object, we know that as the object reaches the ground, it becomes faster and faster. That is because the object is accelerated to the ground making its velocity increase gradually. Now this acceleration is no other than the effect of a force called gravity. So gravity is simply a force that pulls object to the ground. But how about the satellites orbiting the earth? Shouldn’t they fall to the earth too? Yes, they are but since they carry sideways momentum they are constantly falling and missing thus they orbit the earth. This is the classical definition of gravity.

It turns out there are many astronomical phenomenon where this definition of gravity doesn’t hold like the precision of mercury’s orbit that back then can’t be explain. Einstein knew this flaw so he came up with a more general definition of gravity. Imagine that you are to fall off a ladder leaning to a tenths of story building. What would you feel? you would feel weightless meaning not feeling gravity. There is a link between motion and gravity that somehow Einstein manage to link them both and state that gravity is a property of space. Imagine setting a large body in the center of a trampoline. The body would press down into the fabric, causing it to dimple. A marble rolled around the edge would spiral inward toward the body, pulled in much the same way that the gravity of a planet pulls at rocks in space. That is gravity and the predictions it made are pretty accurate with observations.