Chapter 6: Quantum Gravity

This chapter is the largest chapter in the book so identifying and describing my favorite idea from this chapter was quite difficult. I chose to focus solely on the properties of gravity and how it applies in various different situations like when the fourth dimension, time, is introduced. But first I found it quite interesting that Hammond went against what most theorized when looking at gravity. As he described it, many physicists consider gravity to be the weakest of all the forces but he thinks it is one, of if not the strongest of them all. For instance Hammond describes how the nuclear force of electro repletion between particles can be overpowered by gravity if an object has enough mass. More specifically, if I were to sit in a chair, the gravitational force would equal that of the electro repulsion forces between the chair and my body. If a gorilla were to sit on the same chair however, the chair may break, meaning the increased gravitational force (resulting from the increased weight) was able to overcome that of the electro repulsion forces. I can understand what Hammond is saying in this case but there are still some minor details that need to be clarified to fully know what is actually happening. Personally, the way I interpret it is the electro repulsion forces pushing up should essentially be the same force that we talk about in class, the normal force. Because Hammond does not outline this, I am not sure if my interpretation is correct, but if so then it is a very interesting way to use such a simple example to over rule many great theories relating to the strengths of various forces.

Like I said before, the forth dimension of time can be introduced when referring to relativity. This is where things become very interesting and a lot more abstract in terms of thinking. The example that Hammond uses to explain it best is that time slows down in a gravitational field. Hammond explains it by saying “atoms near the surface of the sun, being in a stronger gravitational field than those of the same atoms here on Earth will emit longer wavelengths of light”. This essentially means that relative to a specific point, the more gravitational force an object is exposed to, the slower time will travel for that object. It is a difficult concept to understand and I was not able to visualize much more than those simple examples. However, I can take this theory and understand why astronauts are seconds younger when they come back from long space missions than if they were to stay on earth. This is because they were exposed to less of Earth’s gravity and thus time passed slower for them while in space. Next time I need more time to do a lab I know where to go.