Moving Through Space and Time
In this particular article, I will be detailing some rather abstract concepts. My intention is not to confuse you of course, but to highlight some ramifications of the theory of special relativity, which was developed by Albert Einstein and published in 1905 as “On the Electrodynamics of Moving Bodies.” I will not explain the entire theory here, but I wish to simply illustrate a point on the nature of time and space which I think I can easily explain and will offer you a new way to think about “moving through space and time.”
A primary tenet of the theory is that our universe consists of 4 dimensions: 3 spatial dimensions and 1 time dimension (although the newer string theories developed in the past 20 years say there actually may be 10 or 11 dimensions, though string theory cannot be proven in a scientific sense). The concept of this 4-dimensional space-time continuum is relatively new to the 20th century, although fascinatingly, the concept was first described by H.G. Wells, explained in the first chapter of his classic, “The Time Machine”: “’Clearly,’ the Time Traveller proceeded, `any real body must have extension in four directions: it must have Length, Breadth, Thickness, and--Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, because it happens that our consciousness moves intermittently in one direction along the latter from the beginning to the end of our lives.'“ This book was actually written 10 years before Einstein published his theory of special relativity, quite amazing for a novelist!
Although I will not explain all of the theory of special relativity at this time, it is important to know a few concepts. Einstein said that there was a relationship between space, time, and the motion of objects. This was based on the constancy of light within a vacuum, which was only confirmed several years before Einstein developed his theory. Einstein imagined what it would be like to be a particle of light, and how simultaneity of events would differ if a light source were moving. The classic example of this is a moving train.
I will not go into details here as they are pretty complex (I will devote a whole blog to these concepts later), but Einstein basically said that as objects move, relative time slows down. As objects in motion approach the speed of light, their “internal clocks" get slower and slower, with time completely stopping if the speed of light is reached (although the speed of light can never be reached because it requires an infinite amount of energy to do so, thus, the universe has it’s own “speed limit”). In the same vein, distances also shrink as an object is in motion. Thus, motion has an effect on relative time and space. You can think of each object or particle having their own “internal clock,” and thus his theory abolished the concept of a “universal time” which applies to every object. This basically shattered thousands of years of thinking about how time worked, as events which at first appeared to occur simultaneously, no longer occurred at the same “time.” 10 years later, in 1915, Einstein published his general theory of relativity, which among other things described that gravity had the same effect on time and space as did motion.
This concept is relatively difficult to grasp for some, and I have only begun to scratch the surface of this amazing theory. However, I will try here to explain a unique tool for visualizing how this works. Imagine a graph with an X and Y axis. On the X axis we will plot Time, and on the Y axis we will plot Space. Now we will play around a bit with objects at rest, objects moving at the speed of light, and objects in motion at a velocity somewhere in between these two.
How would you describe an object at rest on this graph? First, we must simplify things, because really there is no such thing as an object at absolute rest. We must speak of relative rest and relative motion. I am sitting at what appears to be at rest at my computer desk, although I am only in relative rest to the earth. Relative to the sun, for example, I am actually in motion, since the earth is rotating, and revolving around the sun, and I am located on the surface of the earth (as well, the solar system is moving, galaxies are moving away from each other, and the universe itself is expanding, so we can never really be at absolute rest).
So imagine I am at relative rest to the earth. How would a line plotted on our graph look? Well, we are always moving through the time dimension (except in one special circumstance which we will get to shortly!), which is the X axis of our graph. But in this case we would say that if I am at rest I am not moving at all through the space dimensions. Thus, a plotted line representing an object at rest will appear as a horizontal line on the graph, because it is only moving through the dimension of time, and not moving through the dimensions of space.
Now let us imagine that I am an object moving at the speed of light (ignore the fact that this is impossible, for illustrative purposes). According to Einstein’s theories, if an object indeed could travel at the speed of light, it would be moving only through the space dimensions, and not through time at all, since relative time stops for objects moving at the speed of light. Now how would this scenario look on our graph? A plotted line representing an object moving at the speed of light will appear as a vertical line on the graph, because it is only moving through the dimensions of space, and not moving at all through the dimension of time.
Given these two scenarios (a vertical line for objects moving at the speed of light, and a horizontal line for objects at rest), any object which is in motion at a velocity somewhere in between rest and the speed of light will appear as a diagonal line on our graph, with the slope increasing as we move faster and faster towards the speed of light (imagine the appearance of this like an arm of a clock moving from 3 to 12). The slope of a horizontal line (object at rest) is 0, whereas the slope of a vertical line (object moving at the speed of light) is 1. Thus our graph can be used to easily illustrate the concepts of special relativity.
Now imagine I start at rest (the horizontal line on our graph), and then I start to move. Our line will begin to shift upwards at increasing slopes as I move faster and faster. Can you see what is happening? As an object’s velocity increases faster and faster, it is actually traveling more and more through the space dimensions, and less and less through the time dimension. It is as if in order to move through space, we must give up some of our time! At the speed of light, we cannot move through time at all, and at rest, we cannot move through space at all! As you can see, I find this pretty amazing. It illustrates that time and space are inextricably linked. The more we travel through space, the less we travel through time, and vice versa. In the future, I will explain more about this amazing theory, but for now, this explanation will hopefully suffice to help you begin thinking about the nature of our universe, and the implications of special relativity. It completely changed how we view the universe.
A primary tenet of the theory is that our universe consists of 4 dimensions: 3 spatial dimensions and 1 time dimension (although the newer string theories developed in the past 20 years say there actually may be 10 or 11 dimensions, though string theory cannot be proven in a scientific sense). The concept of this 4-dimensional space-time continuum is relatively new to the 20th century, although fascinatingly, the concept was first described by H.G. Wells, explained in the first chapter of his classic, “The Time Machine”: “’Clearly,’ the Time Traveller proceeded, `any real body must have extension in four directions: it must have Length, Breadth, Thickness, and--Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, because it happens that our consciousness moves intermittently in one direction along the latter from the beginning to the end of our lives.'“ This book was actually written 10 years before Einstein published his theory of special relativity, quite amazing for a novelist!
Although I will not explain all of the theory of special relativity at this time, it is important to know a few concepts. Einstein said that there was a relationship between space, time, and the motion of objects. This was based on the constancy of light within a vacuum, which was only confirmed several years before Einstein developed his theory. Einstein imagined what it would be like to be a particle of light, and how simultaneity of events would differ if a light source were moving. The classic example of this is a moving train.
I will not go into details here as they are pretty complex (I will devote a whole blog to these concepts later), but Einstein basically said that as objects move, relative time slows down. As objects in motion approach the speed of light, their “internal clocks" get slower and slower, with time completely stopping if the speed of light is reached (although the speed of light can never be reached because it requires an infinite amount of energy to do so, thus, the universe has it’s own “speed limit”). In the same vein, distances also shrink as an object is in motion. Thus, motion has an effect on relative time and space. You can think of each object or particle having their own “internal clock,” and thus his theory abolished the concept of a “universal time” which applies to every object. This basically shattered thousands of years of thinking about how time worked, as events which at first appeared to occur simultaneously, no longer occurred at the same “time.” 10 years later, in 1915, Einstein published his general theory of relativity, which among other things described that gravity had the same effect on time and space as did motion.
This concept is relatively difficult to grasp for some, and I have only begun to scratch the surface of this amazing theory. However, I will try here to explain a unique tool for visualizing how this works. Imagine a graph with an X and Y axis. On the X axis we will plot Time, and on the Y axis we will plot Space. Now we will play around a bit with objects at rest, objects moving at the speed of light, and objects in motion at a velocity somewhere in between these two.
How would you describe an object at rest on this graph? First, we must simplify things, because really there is no such thing as an object at absolute rest. We must speak of relative rest and relative motion. I am sitting at what appears to be at rest at my computer desk, although I am only in relative rest to the earth. Relative to the sun, for example, I am actually in motion, since the earth is rotating, and revolving around the sun, and I am located on the surface of the earth (as well, the solar system is moving, galaxies are moving away from each other, and the universe itself is expanding, so we can never really be at absolute rest).
So imagine I am at relative rest to the earth. How would a line plotted on our graph look? Well, we are always moving through the time dimension (except in one special circumstance which we will get to shortly!), which is the X axis of our graph. But in this case we would say that if I am at rest I am not moving at all through the space dimensions. Thus, a plotted line representing an object at rest will appear as a horizontal line on the graph, because it is only moving through the dimension of time, and not moving through the dimensions of space.
Now let us imagine that I am an object moving at the speed of light (ignore the fact that this is impossible, for illustrative purposes). According to Einstein’s theories, if an object indeed could travel at the speed of light, it would be moving only through the space dimensions, and not through time at all, since relative time stops for objects moving at the speed of light. Now how would this scenario look on our graph? A plotted line representing an object moving at the speed of light will appear as a vertical line on the graph, because it is only moving through the dimensions of space, and not moving at all through the dimension of time.
Given these two scenarios (a vertical line for objects moving at the speed of light, and a horizontal line for objects at rest), any object which is in motion at a velocity somewhere in between rest and the speed of light will appear as a diagonal line on our graph, with the slope increasing as we move faster and faster towards the speed of light (imagine the appearance of this like an arm of a clock moving from 3 to 12). The slope of a horizontal line (object at rest) is 0, whereas the slope of a vertical line (object moving at the speed of light) is 1. Thus our graph can be used to easily illustrate the concepts of special relativity.
Now imagine I start at rest (the horizontal line on our graph), and then I start to move. Our line will begin to shift upwards at increasing slopes as I move faster and faster. Can you see what is happening? As an object’s velocity increases faster and faster, it is actually traveling more and more through the space dimensions, and less and less through the time dimension. It is as if in order to move through space, we must give up some of our time! At the speed of light, we cannot move through time at all, and at rest, we cannot move through space at all! As you can see, I find this pretty amazing. It illustrates that time and space are inextricably linked. The more we travel through space, the less we travel through time, and vice versa. In the future, I will explain more about this amazing theory, but for now, this explanation will hopefully suffice to help you begin thinking about the nature of our universe, and the implications of special relativity. It completely changed how we view the universe.
posted by J-Mart @ 6:57 PM
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