Unified Field Theory and String Theory

Unified Field Theory and String Theory

This essay was assigned to us by our esteemed physics teacher. Before the assignment none of us understood anything about the unified theory, but now we have a greater grasp of these constantly developing theories. The authors of this essay attened Parsippany High School in Parsippany, New Jersey. Their names are: Patrick McGowan, Tom Grasso, and Nicole Henke; feel free to contact them with any questions or comments.

The greatest physicist, Albert A. Einstein, attempted to compile the numerous great theories of all time into a single equation to be known as The Unified Field Theory. According to Einstein, all energy comes from a single source. The speed of light, a universal constant, is equivalent to the frequency of light. At this point during Einstein's life, he wished to combine the theories of electromagnetism and gravitation, which were only two of the many components of the theory.

The four components that must be related in order to solve the Unified Field Theory are Gravity, Electromagnetism, Strong Nuclear Force, and Weak Nuclear Force. First, gravity is the most perplexing of the four components and the most difficult to analyze. The smallest unit of gravity is the graviton, which can only be seen at high speed collisions. The speed of this collision needs to be so great that it has not yet been reached, and therefore the graviton is not a definite particle.

Second, electromagnetic forces is found in matter and always resists displacement of atoms or electrons from their equilibrium position in the material. Oppositely charged particles attract while like charges repel. The particle that carries the electromagnetic force is the proton and are commonly called: gamma rays, light, microwaves, and radio waves.

Finally, Strong and Nuclear Forces also play a pivotal role. Strong Nuclear Force is concerned with the smallest known particles found in protons, neutrons, and electrons - the quarks. Quarks are constantly pushing against one another, yet are held very closely together. In comparison, the Weak Nuclear Force is the compliment of the Strong Nuclear Force. The Weak Nuclear Force holds together the quarks within the nucleus of an atom.

Einstein wished to combine electromagnetic and gravitational forces into one equation that somehow related to the velocity of light. His first problem in creating the Unified Field Theory was his lack of knowledge on the subject. Back in the 1920's, Einstein had not been exposed to the strong and weak nuclear forces and therefore could not ponder such a common solution as he intended. In addition, Einstein thought that the forces of electromagnetism and gravity were two non-related forces. However, physicists today have bridged the gap between the two forces and are better able to relate their similarities.

Many physicists still remain skeptical that the Unified Field Theory can be created. To Einstein's credit, gravity and magnetism are difficult to comprehend because they are invisible energy. Today, this concept is still difficult to comprehend because energy cannot be reduced to weights and measurements. The universe is beyond observation and requires some theory. Skeptics ask how all the equations can be related to light, but light itself still holds many mysteries. Physicists like Einstein argue that light is the key to understanding the various forms of energy. Although there is no present solution to the theory, modern day physicists feel that the answer will surface in the near future.

The Unified Field Theory could not be solved, but it surfaced other advancements. Einstein's thinking on this topic led other physicists to question the observable universe. No longer did observation account as the only backing for a theory, for now the cloud around the impossible and uncomprehendible slowly seemed to dissipate. Out of the Unified Field Theory came a "mixed blessing" which led to further progress. One of these advancements is the String Theory.

According to the String Theory, the elementary particles which compose the string are always stretched, allowing them to be excited. To get an idea of just how small these strings are, they are related Planck's length, or 10-33 cm. (In other words, the strings are about one millionth of a billionth of a billionth of a billionth of a centimeter in length.) There are two theories which explain the nature of these strings. Either they can be closed loops which break open or they can be closed loops which remain closed. Because these strings are floating in space time, they have tension. This value is designated by the following quantity:

1/[ 2 (pi) (alpha prime) ]
alpha prime = square root of Planck's length

The String Theory exists to explain the smallest particle scale using a mathematical model. But in order to understand this theory, a few terms need to be identified and explained. It has become common knowledge that in the String Theory there exists two types of tiny particles. First is the fermion, or the smallest amount of matter known. Second is the boson, or the smallest component of forces known.

It is impossible for two fermions to exist in the same position because fermions are tiny components of matter. However, since bosons are the smallest components of force, it is possible for more than one to exist in the same position.

There are four different types of strings: there are the aforementioned open and closed looped strings, each of which is further divided into two types. First, a string can contain bosons. According to the Bosonic String Theory, only bosons exist within the string. Second is a string which contains bosons and fermions. According to "Supersymmetry," for every fermion there exists a corresponding boson. This one to one ratio between the two particles causes a balance within a string.

For every different type of string there exists a separate theory. According to the previously mentioned Bosonic String Theory, there are no masses that the forces can act on. Thus an imaginary mass, called the tachyon, is introduced for the practical purposes of calculating the value of force. In the second theory, Supersymmetry between forces and matter contains no imaginary mass and has both open and closed looped strings. In the third theory, which is titled Supersymmetry between forces and matter, tachyon is not present and it contains only closed strings. The difference between this and the second theory is the presence of a fermion spin; there are two types of fermion spins, nonchiral or chiral. A nonchiral fermion spin turns in both direction while a chiral only turns in one direction. The fourth string theory concerns closed strings without the presence of tachyon. This fourth type of Supersymmetry strings are also referred to as heterotic, meaning they move differently in the right direction then they do in the left direction. There are variations among the fourth theory, including the symmetrical layout of the strings. Every theory only has ten dimensions, except for the Bosonic theory which has twenty-six.

It has been established that the universe is ten dimensional, but unfortunately for theorists, we can only measure and observe three crude dimensions. The fourth has been established as time, leaving us six to account for. Thus the process of "compactification" begins. Compactification is the folding of the extra dimensions, in this case six, into the four fundamental dimensions: length, width ,height, and time.

The latest form of the String Theory, the Matrix Theory, has eleven dimensions -- the eleventh being supergravity. This recent theory lacks precise equations of motion. However, it is similar to the String Theory in all but the way it utilizes compactification. Eleven dimensions are compactified into four. However, the matrix equation is so recent that there are many unanswered questions.

What Albert Einstein valued as important information in his day was quickly replaced as new leads developed. Physics and the development of the Unified Field Theory are only as valid as the ideas that support them. Even while progress was made in supporting this theory, other advancements were made in other areas, like the String Theory. The key to unlocking the secrets of the universe will be found one day. With technology constantly improving, new and improved probes may allow for the viewing of the finest particles which we can now only dream of seeing. But then again, physics reaches beyond the realm of the observable world and into the unexplored.

For those of you who don't understand it here is a really neat poem that we are sure will help allow the not so science inclined to understand.

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[To Pat |To Tom | To Nicole ]

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