A Brief History Of Time

Table Of Contents

1. Book review (Stephen Hawking's A Brief History Of Time)
2. Seven fun facts about the Cosmos
3. To infinity, and beyond

1. Book Review

To say that this was an easy read would be a lie... but to say that it was an interesting read couldn't be further from the truth. Stephen Hawking's 1988 best-selling science book is one of the most mind blowing things I have ever experienced. In it, he covers topics ranging from space and time, to the uncertainty principle, to black holes, and the origin and fate of the universe. The introduction by another legendary scientist, Carl Sagan, whets your appetite for the pages ahead.

If you want to read this book (and if you are at all interested in the cosmos I highly recommend it), I suggest reading it when you have the least amount of distractions such as noise and fatigue. This is because every page contains so much information that if you blink you'll miss something, an event I found myself doing throughout reading this book. My first attempt at it (yes it's one of those) was last year, and I got half way through it only to lose interest and start something else. So in many ways a level of commitment is needed to get through it; and when you do the rewards will be great.

On my second attempt I had a little more time on my hands, and so took my time. I kept notes on interesting facts (7 of those I will share with you in chapter 2 of this blog), as it was not only a way of keeping track of where I was at, it also solidified my knowledge of often super confusing ideas such as the uncertainty principle and wormholes. This book is meant for someone who has no knowledge of science at all (a 'layman') and even though I know bits and pieces, I've never actually studied physics beyond high school, and even then Mr. Fernside's year 10 science class wasn't the right environment for me to grasp these concepts.

I guess that Hawking does a good job at explaining these concepts to a layman, however I felt that I needed to stop and go on Wikipedia to learn more as I went along, and in that respect (since this book was published in the 80s and the layman back then wouldn't have had their own encyclopaedia in their pocket) the book is a little confusing, and hard to read at times. But that's what I liked about it, he doesn't dumb any of the concepts down at all. Hawking explains a concept once, and if you don't understand it, I think the best thing to do is to just keep reading. An excerpt from the book states, "If you remember every word in this book, your memory will have recorded about two million pieces of information" - and that's if you remember every word.

So my advice is to jump into it with a fresh and open mind, knowing that it's not going to be an easy read, and to keep a piece of paper and pencil handy so you can grasp the universe we live in just that little bit better. In the next chapter, I will share with you 7 of the most interesting things that I came across whilst reading this phenomenal book by a very intelligent man.


2. Seven fun facts about the cosmos

1. The Big Bang: Approximately 13.7 billion years ago the universe exploded from a singularity (under the the Big Bang Theory) in which the density of the universe and the curvature of space-time would have been infinite (a breakdown of Einstein's General Theory of Relativity). The universe was originally in an extremely hot and dense state, and expanded rapidly before slowing and cooling. In chapter 8, Hawking explains exactly how the big bang created stars through a cloud of materials such as hydrogen which clump together by gravity and through the process of nuclear fusion, create helium. Large stars eventually explode in what is known as a Supernova, with their debris going on to form other stars and planets such as our own Sun and Earth.
2. Expanding Universe: The theory that the universe is expanding was confirmed in 1929 by Edwin Hubble, when after nearly a decade of observations he proved that the velocity at which galaxies are moving away from the Earth is proportional to us. To understand this they used the Doppler effect, which basically says that if an object is moving towards us (say a fire engine), the sirens will sound relatively louder when approaching and softer when receding. The same applies to electromagnetic waves such as light, with the approaching waves appearing blue, and the receding waves of light appearing red. Hubble observed that galaxies were red-shifted, and therefore must be moving away from us - thus the expanding universe. 
3. Light Cones: A light cone explains the path that light travels through in spacetime. If you go to the Wikipedia page, it explains what it is. I like this idea because as a kid I heard that when I look at stars in the sky, they are not as they are now, but since light takes so long to get to us they could be images thousands of years old. An example is that if the sun ceased to shine at this moment, it would take eight minutes (since the sun is eight light minutes away) for the event to enter our future light cone.
4. String Theory: The first incarnation of string theories arose in the 1980s as a result of the age old quest for a Grand Unified Theory and ultimately a Theory of Everything. In these theories the basic objects are not particles, which occupy a single point of space, but things that have a length but no other dimensions, like an infinitely thin piece of string. There are about 5 different string theories (all available on Wikipedia for your reading pleasure), so in the interest of time (and the fact I don't understand them), I will try and wrap it up. Basically, string theory postulates that there are in fact 10 dimensions, 6 more than the 4 dimensions that we are aware of (being height, length, width and time). To visualise even 4 dimensions is hard - so I'll leave it up to Carl Sagan to explain: 4th Dimension Explanation. Once you grasp 4 dimensions, watch this to (try and) understand 10 dimensions.  
5. Anthropic Principle: Of all the concepts in Hawking's book, I found this one to be the most interesting. The basic idea is that we, as humans, see the universe the way it is because we exist in it. There are two versions of the anthropic principle, the weak and the strong. The weak principle states that as intelligent beings living in this point in space-time, in this location of the universe, we see things we want to see to make our experiments work and that are necessary for us to exist (a bit like a rich person living in a wealthy neighbourhood and not seeing any poverty). However go further into a strong anthropic principle, and to quote Hawking, "there are either many different universes or many different regions of a single universe, each with its own initial configuration and, perhaps, with its own set of laws of science. In most of these universes the conditions would not be right for the development of complicated organisms; only in the few universes that are like ours would intelligent beings develop and ask the question: "Why is the universe the way we see it?".
6. Black Holes: In 1928 an Indian graduate student, Subrahmanyan Chandrasekhar calculated that a cold star of more than about one and a half times the mass of the sun would not be able to support itself against its own gravity (this mass is now known as the Chandrasekhar limit). If a star's mass is less than the Chandrasekahar limit, it can eventually stop contracting and settle down to a possible final state as a "white dwarf". Stars with masses above the Chandrasekhar limit will shrink until the gravitational field at the surface becomes so strong that the light cones are bent inward so much that light can no longer escape. According to the theory of relativity, nothing can travel faster than light - and since light cannot escape, neither can anything else; everything is dragged back by the gravitational field. This event causes a black hole. To once again quote Hawking, "Its boundary is called the event horizon and it coincides with the paths of light rays that just fail to escape from a black hole".
7. Time Travel: Hawking doesn't discuss time travel a whole lot in the book, however I recently saw a three part series that Hawking did for the Discovery channel that came out this year, entitled Into The Universe with Stephen Hawking - and the second episode was on time travel (you can see a snippet of the episode here). In the episode, Hawking believes that time travel is possible, using a few different methods. The first is to create a wormhole - a portal through spacetime. If humans could create such a thing, we could theoretically travel back through time, and into the future (such wormholes are thought to exist inside black holes). However, he explains that travelling into the past creates a paradox, since if you were to alter an event that has already occurred, it would have drastic consequences on events today (like when Homer creates a time-machine-toaster in the Simpsons). He does however believe that we can travel into the future. This is possible using one of two methods. The first is the concept that time slows down when close to a large mass - the example in the show is that time devices on satellites orbiting the Earth are very slightly running faster than clocks down here, and an in-built device is used to correct them. He stipulates that if we could get a spaceship into the orbit of a black hole (very large mass) that time will travel twice as fast on Earth than on the space-ship - effectively travelling through time. The other possibility is to travel at near the speed of light (only light, or other waves that have no intrinsic mass can move at the speed of light). He gave the example of a train track that went around the whole surface of the Earth; and to travel at the speed of light would mean the train going around the Earth 7 times in a second... very fast. One day though it may be possible to build a spaceship that can gain enough energy to travel that fast, and time travel into the future will be a reality.

3. To infinity, and beyond


Reading this book has opened my eyes to the wonders of the cosmos. Concepts such as black holes, the big bang, and time travel all make more sense. There is one concept though that I can't seem to grasp - infinity. I know that infinity by its very nature cannot be understood, and so I've accepted that; however it is fun to think about. Going back to the singularity that existed before the big bang, in which there was infinite density and curvature of space-time blows my mind. It brings up the question of God, or some other higher power that may have had the ability to exist before the big bang. And then there's the concept of the big bang itself, even though there is a lot of scientific evidence proving that it happened, I'm always sceptical of anything - even if it is proven. I'd like to think that there are multiple universes, all with different laws of science (akin to the strong anthropic principle), and beings such as us wouldn't be able to comprehend them - we wouldn't even be able to exist to have this discussion... it just blows my puny human brain to pieces. Then there's the question of Alien life, what would it look like? Would they be friendly? Hawking address these questions in the first part of the Discovery channel series, very interesting indeed.

I guess in the end though, in this day and age, no single person can know everything about the universe (not even Stephen Hawking), as people devote their entire lives to single fields of science. However, I think that compared with 100 years ago, the average layman today knows a lot more about the universe than back then - this is due to evolution, the only truth that I know exists for sure, since I have experienced it's force while meditating (sorry if that sounds pompous). The flow of nature will continue to exist I know that - the collective spirit that is within every living being will continue to flow, whether we are dead or alive, in this universe or in another, within me or without you.

- Russell