Theory of Relativity: Space-time

In 1915, Albert Einstein first proposed his theory of special relativity. Essentially, this theory proposes the universe we live in includes 4 dimensions, the first three being what we know as space, and the fourth being space-time, which is a dimension where time and space are inextricably linked. According to Einstein, two people observing the same event in the same way could perceive the singular event occurring at two different times, depending upon their distance from the event in question. The theory of relativity was revolutionary because it showed how the speed at which time happens is subject
to change, that space and time are not separate entities: time, space, and motion (ie, movement through space) collapse into a fourth dimension, in which all act on each other.

Put it another way, imagine you have a twin. You stay on earth, your twin goes into space, traveling at the speed of light, for 10 years. When your twin returns, she's a couple of years younger than you are.

Another example of Einstein's "Twin Paradox" is, a 25 year old twin stays on earth while the other sets off on a space voyage, traveling almost at the speed of light. After 10 years in space, she heads back to Earth. By the time she lands, her on-board clock shows that 20 years as passed and she is 45 years of age. Because of relativity, her twin sister is now, 71 years old. Space travel, at 186,000 miles per second, is also time travel. Therefore, the twin who went on the space voyage actually travelled into the future without getting that much older. Time is only relevant in this earthly dimension.

It even works with airplanes, circle the earth, flying low, when you return to your starting point, your watch will be slightly behind. If you were actually moving at the speed of light (which you couldn't do, but suppose you could), your watch would stop altogether.

It's called the "Theory of Relativity" because time and length are no longer absolutes. You’ve got your digital watch on your wrist and a meter ruler on your desk. These seem like absolutes: a second and a centimeter for you, must be the same as they are for me, and the same as they are on Alpha Centauri. But they’re not.

Einstein's Theory of Relativity has been proven to be a physical law of the universe. Although spacecraft are still too slow for astronauts to notice the effects of relativity, research into the behavior of subatomic particles gives clear support to the theory. A Swiss laboratory watches what happens to subatomic particles as they whiz through a circular tunnel attaining speeds close to that of light. The results, such as unstable particles staying alive a lot longer than they normally would, explain the theory of relativity.

The cornerstone of Einstein’s Relativity was, of course, E = mc2 — that is, energy equals mass times the speed of light squared. It is actually a simple equation, but its ramifications are monumental and universal. It means that there is an incredible amount of energy in any object, if we could just get at it in the nucleus of its atoms. If this could be verified, it would seem to mean that Relativity’s basic tenants of space and energy and time being continuous would be one step closer to fact.

It would be by the nuclear detonations at Alamogordo, New Mexico, July 16, 1945, that E = mc2 would be proved. A chain reaction in the uranium atom caused the greatest explosion man had ever known. The atomic age had dawned.

As the space age dawned, further proof came of Einstein’s concept of the continuity of time and space. Atomic clocks placed at orbital heights recorded time passing just slightly faster than those at sea level. Where gravity, and hence a curvature of space, was greatest time moved more slowly; where it was not, more quickly. The passage of time as we record and experience it here was actually slower than in space.

Mass— such as this planet— did seem to bend space before it, and with this it did seem to slow time. Fractionally, granted. But it finally opened the labyrinth of time to logical conquest. Theoretically, it was proposed the greater the curvature of space, the greater time would be slowed. But if the Earth could only slow time fractionally by its massive size and speed through space, what on earth, or anywhere else, could bend space even more to significantly affect the progression of time?

The examples of speeding cars clearly indicates they cannot go fast enough to truly bend space and lock one into a different progression of time. But would it really require huge mass and speed to do it? The planet was indeed doing it slightly. But if time’s pathway lay along energy, could not bending or changing its electromagnetic frequencies also bring this about? There must be other methods to bend electromagnetic wavelengths.

Gravitational Time Dilation

An important aspect of Einstein's theory of relativity to note is that he proposed matter causes space to curve. If we pretend that "space" is a two-dimensional sheet, a planet place on this "sheet" would cause it to curve. This curvature of space results in what we perceive as gravity. Smaller objects are attracted to larger ones because they "roll" through the curved space towards the most massive objects, which cause the greatest degree of curvature. In relation to time, this curvature causes the gravitational time dilation effect. Under normal circumstances, this effect is impossible to observe. However, in the presence of the extremes of our universe (such as black holes, where a huge amount of matter is compressed into an extremely small volume), this effect becomes much more obvious. To a distant observer, an object falling into a black hole would appear to never reach it, due to time dilation causing time to "progress" extremely slower, at least relative to the distant observer (the object in question, however, would very rapidly be destroyed by the black hole).

A second aspect to the gravitational time dilation postulate is that the faster an object is moving, the slower time progresses for that object in relation to a stationary observer. While in everyday circumstances, this effect goes entirely unnoticed, it has proven to be true. An atomic clock placed on a jet airplane was shown to "tick" more slowly than an atomic clock at rest. However, even with the speeds achieved by a jet aircraft, the time dilation effect was minimal. A more solid example can be seen through an experiment performed on the International Space Station (ISS). After the first 6 months in space, the crew of the ISS aged .007 seconds less than the rest of us on earth (the relatively stationary observers). The station moves at approximately 18,000 miles per hour, much faster than the range of normal human speeds. Even with such speeds, however, time dilation is minimal unless you approach speeds close to the speed of light (300,000 kilometers per second; 1,080 million kilometers per hour; 186,000 miles per second; 671 million miles per second).

Time as a Fourth Dimension

To understand time as a fourth dimension, it is necessary to recognize that any human attempt to "draw" or "represent" time beyond our immediate perception of it (basic, linear progression), is inherently flawed, because our mental capacity is limited to three dimensions. However, time, like space, is a dimension in itself, and objects can transverse it in a similar way as they do through the third dimension. A popular way of viewing time is using a coordinate set of axes, except instead of using a plane with simple x and y axes, a z axes can be added. The graphic to the left represents a possible way of viewing time. As a person walks forward, he is traveling though the three dimensions of space, and a fourth as he progresses forward through time. Thus, for humans, time travel (or traveling through the fourth dimension) is entirely possible, however, only in one direction. Relativity has shown us that it is possible to change our perception of time based on distance, gravitational dilation, or speed, but the direction of time has remained constant and singular.

Consequences of Einstein's Scientific Revolution

The changes Einstein ushered in with his radical theories of relativity resulted in the now ubiquitous E = mc2 equation, which essentially states that matter and energy are interchangeable (this discovery eventually led to the creation of the first nuclear fission bomb). However, Einstein's equations also predicted the presence of black holes and gravitational waves, and were initially excused as inconsequential aberrations, however there is now substantial evidence to support the existence of black holes. Just as importantly, Einstein ushered in an entirely new age of theoretical physics, helping to tremendously advance our perception of the universe and directly contributing to today's modern string theory, an attempt to unify the theories of relativity and since-discovered quantum mechanics into a unified explanation of the universe.