A Brief History Of Time: Journal Entry 6

Chapter 6 (Pg 83-101) Today, I read about two theories on light: one that states that light is composed of particles and the other states that light is composed of waves. I also read about the life cycle of stars, which is needed to understand in order to how black holes are formed. I read about how a black hole is formed. A black hole is formed due to the gravitational collapse of star in which it shrinks to critical radius where the gravitational field becomes so strong that nothing escapes. Today, I read about how Stephan Hawking & Roger Penrose’s they did in 1965 & 1970 inspired Penrose to create the cosmic censorship hypothesis, a theory that suggests singularities made by a gravitational collapse occur only in places like a black hole. I learned that the event horizon is a path in space-time where nothing can escape; it’s also like a gate to the black hole. Hawking then talks about how in 1967 a Canadian scientist Werner Israel revolutionized the study of black holes by showing that according to general relativity non rotating black holes must be very simple in that they were perfectly spherical, their size depended on their mass, and any two black holes with the same mass were identical. And I learned that to find the number of “primordial” black holes depends on the conditions in the early universe and that if we find that number and how much the number has decreased since then, we can learn about how the universe was in its early stages.