Two of my favorite subjects in high school were, ironically, Physics and Geometry. This is ironic because since high school, I have not pursued those subjects at all. Quite the opposite. But, my love of Science Fiction I think has always kept my interest in those subjects piqued, especially lately since I’ve been reading a lot more SF than in years past.
I decided to read Stephen Hawking’s book because I am doing research for my own writing, and because I generally want to understand the universe better. Well, let me clarify that a little: I want to understand a little more about what others THINK they know about the knowable universe. I will admit that reading this book, despite Hawking’s clear attempt to make everything palatable for the layman, it is still difficult to wrap my brain around. But, that’s the point of this blog: to read it, to write about it, and hopefully to understand it better as a result of that process. So, here goes. I’m going to do a little summarizing, a little analyzing and referencing, and probably a lot of questioning. A reminder that the point of this reading blog is for digestion, not necessarily for pontification.
For all posts on this book, I am referencing the page numbers, where applicable, in order to avoid any semblance of plagiarism, etc. The bibliographic reference for the version of the book I’m using is this and it applies to all posts related to A Brief History of Time:
Hawking, Stephen W. A Brief History of Time: From the Big Bang to Black Holes. Intro. Carl Sagan. New York: Bantam, 1988.
In the first chapter, entitled “Our Picture of the Universe,” Hawking starts out slow with a little history. I learned that we see some stars and not others because the others’ light hasn’t reached us yet. He continues this further in chapter 2 by going into detail about the bending of light from distant stars around the sun, whereby stars look as if they are in different positions than they really are because of how their light is bent around our sun. He brings up Immanuel Kant’s Critique of Pure Reason (which, interestingly enough, I bought when I was in high school, no joke) and the concept of ANTINOMIES, which are contradictions like the “THESIS that the universe had a beginning, and the ANTITHESIS that it had existed forever” (8). Apparently the thesis and antithesis are based on the same assumption: “that time continues back forever, whether or not the universe had existed forever,” though according to St. Augustine, time didn’t exist before God created the universe (8). To me, this says that God is therefore outside of time AND the universe. Interesting.
Chapter One ends with a discussion of a unified theory of the universe, which is a goal of scientists: to unite the GENERAL THEORY OF RELATIVITY (gravity and the large-scale structure of the universe (11)), and the THEORY OF QUANTUM MECHANICS (phenomena on a small scale (11)) in order to make sense of the big and the small, and therefore the whole lot. Hawking also points out that theories aren’t provable but that a good theory “ACCURATELY DESCRIBE[S] a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must MAKE DEFINITE PREDICTIONS about the results of future observations” (9) [EMPHASIS MINE]. I think this is a good point because if we go on Herr Kant’s concept of antinomies (i.e. embrace the possibilistic in terms of explaining the how, why, when and where of the universe), I feel much safer knowing that (at least some of) those scientists aren’t out there assuming their difficult-to-comprehend theories are actually provable.
Chapter Two, entitled “Space and Time” gets a little more difficult. In this chapter, ABSOLUTE SPACE and ABSOLUTE TIME are disproved. Absolute space cannot be validated because the earth is in constant motion, and you are never where you were a second ago due to this; therefore, there is no absolute, stationary position in space. Absolute time cannot be validated because time “depends on where [you are] and how [you are] moving” (33). Hawking gives the example of the TWINS PARADOX: one twin living on the top of a mountain will age faster than one closer to sea level, or the twin that leaves on a spaceship going near the speed of light will age less than the one on earth; or the example of two highly accurate clocks: one placed at the bottom of a water tower, which ran slower than the one placed at the top of the water tower (32). The observation I make here is that many-a-SF-plot has been based on these ideas of the slowness of time from different vantage points. The example I can think of right now is Arthur C. Clarke’s Odyssey quadrilogy, where Dr. Heywood Floyd lives well beyond the natural earth-bound life expectancy–so long, in fact, that he gets to go on another mission to Jupiter. Awesome!
So, apparently time runs slower around a massive body (32), and this is one of the reasons navigation systems work today: because they are based on time signals from satellites (33). Coincidentally, I saw a Discovery-Channel show the other day about the importance of the accuracy of the multiple clocks used to triangulate positions using GPS–that the satellite-bound clocks had to be programmed to make up for the slower clocks on earth. According to Hawking, this relates back to the theory of GENERAL RELATIVITY (33).
I suppose the most difficult aspect of Chapter Two is the talk about time, space, and space-time. I learned that distance is measured by time; that time is more accurately measured than length; that a POSITION in SPACE can be described by three coordinates (e.g. latitude, longitude, and height above sea level); that an EVENT, which is something that happens at a particular POSITION/point in SPACE and at a particular TIME, can be described by four coordinates (3 for position, 1 for time); that where & when an EVENT happens is called SPACE-TIME, which is a 4-dimensional space: in other words, if the EVENT occurs at a particular POSITION in SPACE (i.e. needs 3 coordinates to describe its location), at a particular TIME (i.e. needs 1 coordinate to designate time), then it is 4-dimensional.
I also learned that there are such things as FUTURE LIGHT CONES and PAST LIGHT CONES. When an EVENT takes place in the present (Hawking uses the example of our sun dying, on earth we will not see the loss of the sun’s light for 8 minutes), there is a three-dimensional cone (i.e. 3 coordinates to designate POSITION) that expands out from the event in an ever-increasing conical shape (i.e. smallest at the point of the EVENT, and getting bigger as it progresses out into space and time). This three-dimensional cone also exists in the 4-dimensional space of SPACE-TIME because time is always progressing forward. Okay, so imagine the sun dying as the EVENT; if it takes 8 minutes for the loss of light to reach the earth, then for 8 minutes, we will not be in the FUTURE LIGHT CONE of the EVENT called the Death of the Sun. But, at the 8+ minute mark, we will be within the FUTURE LIGHT CONE of the Death of the Sun because eventually that loss of light will be reaching us. I would like to point out that I wrote very briefly about a film called Sunshine, in which this was a concept presented: if their mission succeeded, the sun would shine brighter in 8 minutes….)
The thing called the PAST LIGHT CONE is merely all the possibilities of light (or, I suppose, other things) that will reach the Present time after some EVENT has happened in the past. For instance, there are stars in the sky that burned out millions of years ago, whose light is just reaching earth. By the time we see their light, we are witnessing a PAST LIGHT CONE. I was confused about this because the PAST and FUTURE LIGHT CONES seem to be the same thing on first thought because it would seem like all EVENTS are technically in the past relative to us in the present so why distinguish between PAST and FUTURE LIGHT CONES? But what I realize now is that, if we take the Death of the Sun scenario and how 8 minutes after the EVENT (in the past) we see the loss of light because we are in the FUTURE LIGHT CONE of the EVENT, at the “Present” moment of the EVENT (that technically occured in our past), we are in the FUTURE LIGHT CONE, but at our own “Present,” we see the PAST LIGHT CONE’s past EVENTS. Anyway, I think that’s how it works out.
The way I am trying to conceptualize these PAST and FUTURE LIGHT CONES is by imagining William Butler Yeats’ “perne in a gyre” concept (especially from his poem, “Sailing to Byzantium”), which very exactly matches the diagram in Hawking’s book of two cones, touching each other at the tiny base points, with the big ends radiating up and down (or out). All of this cone discussion comes from pages 22-28.
The last thing I want to bring up is the concept of the GEODESIC which is basically the “shortest (or longest) path between two nearby points” (29). Rather than GRAVITY being the reason that the earth moves in a curved orbit around the sun, Einstein theorized that it was rather a GEODESIC that the earth was following: “the nearest thing to a straight path in curved space” (29). Einstein theorized that space-time was not flat, but curved or warped (29), and this curvature of space-time causes large bodies to follow these GEODESICS, rather than the attraction of GRAVITY to pull or repulse the large bodies and keep them in the same space. So apparently the earth merely moves forward in space-time in a circularly-straight line along a GEODESIC, rather than being in a GRAVITY-related orbit around the sun (30). Interesting.
That’s about it for now. Throughout this process I have actually clarified a few points, hopefully correctly, for myself. So far, mission accomplished.