A Brief History Of Time: Journal Entry 2

Chapter 2 (Pg 15-35) Today, I started a new chapter about Space & Time. He talked about the theories of Galileo, Aristotle, & Newton.  He said that each of them either disproved the other’s theories or added on to it (Galileo on Aristotle, Newton on Galileo & Aristotle). He stated that “The big difference between the ideas of Aristotle and those of Galileo & Newton is that Aristotle believed in a preferred state of rest, in which any body would take up if it were not driven by some force or impulse.” It also talked about the lack of absolute space and Newton on lack of absolute space and Newton & Aristotle on absolute time. And he talks about the speed of light, ether, and how Einstein disagreed with the idea of ether and that it is unnecessary. I read about Einstein’s theory of relativity, how the speed of light is measured, and four coordinates of an event that specify its position in the four dimensional space. I read about how the speed of light should be the same as the speed of the source. I also read about how Einstein’s general theory of relativity came to be and what it is. I also learned what a geodesic is. I learned about the twins paradox on how if one twin leaves on top of a mountain and the other lives at sea level, one twin will age faster than the other. Also, I read about light rays & light deflection. I also learned that with this knowledge on space and time we can have a better understanding of the universe. And I read that Einstein’s general theory of relativity implies that our universe has a beginning and, unfortunately, an end.