The Theory of Everything

A Briefer History of Time by Stephen Hawking

Book Name: A Briefer History of Time
Author: Stephen Hawking

Finding answers to how the universe works has been the focus of scientists for millennia. In the book A Briefer History of Time, world-renowned theoretical physicist Stephen Hawking searches for a single,  complete theory of physics that explains everything in the universe.

In the book, Stephen Hawking stops along the way to introduce us to the great discoveries of time, those including the concept of curved space, the expanding universe, dark matter, black holes, the Big Bang, wormholes, and more.  In the process he clarifies and explains gravity, relativity, and quantum mechanics. He covers amazing discoveries regarding the nature and size of the known universe and discusses important observations based on our effort to peer into distant galaxies. What a journey, done with humor (we learn, for example, how "Isaac Newton was not a pleasant man"), and Stephen Hawking does it "Briefer" that his prior "Brief" history.

Arriving at a complete theory of everything, we learn, requires an understanding of smaller theories, which when pieced together, explain the magic of the universe.  These component theories, though smaller than the whole, are each extraordinarily significant in their own right. Among these, are the Doppler effect, the theory of relativity, and time travel.

Everyone has heard of Einstein's general theory of relativity, but Hawking puts it into context for the reader. This theory explains that gravity, the special force that keeps our feet on the ground, exists because   "space-time" is curved.  Hawking clears-up many misconceptions. For example, the earth does not move in a curved orbit because of gravity; rather, the earth moves in a curved orbit because it follows "the nearest thing to a straight path in curved space". This is called a geodesic. A geodesic can be understood as the shortest path between two places. A good example of a geodesic is when flying to Hong Kong from New York City, you wouldn't travel around the earth; instead, the pilot would travel towards the North Pole and down to Hong Kong because the Earth is a sphere.

The Doppler effect shown by the wailing sirens of a police car.

Hawking also clarifies the Doppler effect. One example of the Doppler effect is when a train honks its horn as it passes by. At first, the horn sounds higher pitched and then, as it passes, the pitch gets lower. As the train approaches, the distance between the wave crest or wavelengths grows increasingly smaller.  The smaller the wave crest, the more sound waves we hear, causing a high pitched sound. Afterwards, when the train is moving away, as Hawking explains, "the wavelength will be greater and the waves will reach our ear with a lower pitch".

A diagram of a wormhole.

Near the end of the book, another nearly incredible theory emerges. Hawking proposes that time travel is theoretically possible (but, don't get your hopes too high because you will need to travel faster than the speed of light, as I explain later). How would this work?  As Hawking explains: suppose there an event on Earth, event A, and event B is an event on Proxima Centauri (the closest star to Earth besides the sun, which is approximately 4 light years away). Suppose that event B happened a year later according to Earth's time. Since the two bodies in space are a few light years apart, and because A happens before B, you would have to travel faster than light to get to B from A. Then, according to the book, "to an observer on Proxima Centauri moving away from the Earth at nearly the speed of light, it would appear that the order of  events is reversed: it appears that event B occurred before event A". Thus the observer on Proxima Centauri would think that if you traveled faster than the speed of light, you could travel from event B to event A. There is one problem though. How would you travel faster than the speed of light, if it is (right now) the fastest thing in the universe? Stephen Hawking explains that there is one possibility for overcoming the difficulty of traveling at such an immense speed, the idea of the wormhole. The concept of wormholes actually originated in a paper published by Einstein and another scientist in 1935, but they thought of it more in terms of a brief bridge connecting space and time. Modern theorists have surmised that time travel is possible if we could learn how to warp space and create a negative density in space (thing of it as bending space to create the shape of saddle) and then creating a shortcut, sort of like a tube, connecting two different areas of space and time (think of the outer ridges of the saddle). However, as Stephen Hawking points out, "One question is this: if it's possible to travel into the past why hasn't anyone com back from the future and told us how to do it?".

 

In all, for those interested in understanding the ultimate mystery of how the universe works, this is an enjoyable and captivating read. So much information is packed into this rather small but significant book. The main idea of the book was to try to find one complete theory of physics that explains everything in the universe.  Stephen Hawking shows us many of the theories that must be understood before it will be possible to arrive at a complete theory of physics. Every theory described was concise but full of information that was necessary to understand that particular theory. Personally, I feel like the ending of the book is a cliff-hanger though, as Stephen Hawking concedes that it might not be possible to find one complete theory of physics because there would need to be so many theories proposed in that one theory. He also suggests that if we discover the complete theory of physics, it may (relatively speaking) be a very long time before we discover a truly complete theory of physics, as it is necessary first to find a theory for every single aspect in the universe and then combine them into one theory. I highly recommend for those interested in physics, quantum physics, space, and time. It is well written, intelligent and highly informative. And maybe one day in the future, scientists will uncover the complete theory of physics that explains everything in the universe.  If so, Stephen Hawking will have helped to clear the path for this great discovery