Understanding String Theory - Physics-Astronomy.org

Understanding String Theory


Molecular structure (atoms).
Atom (protons, neutrons, electrons).
The fundamental particles of the Universe that physicists have identified (such as electrons, neutrinos, and quarks) are the building blocks of all matter. They appear to have no further internal structure, meaning that they cannot be subdivided into other objects. Nevertheless, according to a theory called String Theory, if we could examine these particles even more closely, with an amount of precision that might be beyond our current technological capabilities, we would discover that each particle is not like a point but rather a one-dimensional loop. To understand this more clearly, think of a rubber band that is nearly infinitely thin. A growing number of scientists now believe that all matter in the Universe is comprised of such a building block. Scientists call this very thin “rubber band” a string, a string (like a violin string) that oscillates and vibrates to form matter.

Admittedly, for even the most educated scientists, this is not an easy concept to grasp. However, the recent discoveries have led many scientists to adopt this string theory to explain the composition of all matter. But, its biggest significance is that it resolves one of the most vexing problems in science in the past century.
Until the present day, scientists were unable to reconcile the differences in behavior of extremely small objects (like electrons, neutrinos, and others) and extremely large objects (like planets and stars). They behave differently. They do not seem to follow the same laws of physics.
On the one hand, you have quantum mechanics, which is the study of subatomic particles.
Quantum mechanics has its own set of theories and laws. Our current knowledge about the subatomic composition of the Universe is contained in what is known as the Standard Model of Physics. The Standard Model describes the composition of both the fundamental building blocks out of which the world is made (particles), and the forces through which these building blocks interact. There are twelve basic building blocks. Six of these are quarks, and they have the following names: up, down, charm, strange, bottom, and top. (A proton, for instance, is made of two “up” quarks and one “down” quark.) The other six are leptons, and include the electron, the muon, and the tauon, as well as three types of neutrinos.
Physicists studying activity at this subatomic level noticed some unusual phenomena. For one thing, the particles that exist on this level have a way of taking different forms arbitrarily. For example, scientists have observed photons, which are tiny packets of light, acting as both particles and waves. Even a single photon exhibits this strange duality.

Therefore, on the one hand, you have this tiny world of quantum mechanics. However, on the other hand, you have the theory of relativity, which outlines how very large objects behave over very large distances traveling at high velocities. The problem, however, is this: the theory of relativity and the theories contained in the study of quantum mechanics contradict each other. In essence, it means that they both cannot be correct. String theory fixes this problem by proving a single set of principles to explain the behavior of matter. While this fix is monumental enough, it is only one of the reasons that String Theory has excited scientists enough to prompt them to call it potentially one of the most important discoveries in all of science.
Unified Field Theory
Albert Einstein developed the theory of relativity. During his lifetime, astronomers and scientists did not have the knowledge that they have today. For example, Einstein and other scientists were only aware of two distinct forces: gravity and electromagnetism. The “strong” and the “weak” nuclear forces had not yet been discovered. Nevertheless, Einstein was keenly aware of the difficulty of reconciling the laws of quantum mechanics and his newly formed theory of relativity. He devoted much of his lifetime to reconciling the two sets of laws and theories. He was searching for what he called the Unified Field Theory. He wanted to show that all matter behaved with one underlying set of principles and laws. History regards Einstein in a very high manner, but his quest to find this theory was quite radical in his day.

However, as we soon discovered, Einstein was certainly ahead of his time. It would not be an exaggeration to say that today the search for the Unified Field Theory is now the aim of most of the scientific community. An increasing number of mathematicians, scientists, and astronomers are now convinced that String Theory might provide the answer to this elusive Unified Field Theory. It is often called the “Theory of Everything.” From the single principle that all matter consists of vibrating strings, scientists can explain the behavior of all forces and the composition of all matter.
To more clearly understand the concepts behind String Theory, imagine a guitar’s strings. If a skilled musician vibrates the guitar’s strings in a certain way, a set of sounds will be emitted from the instrument to produce a recognizable song. However, there is a nearly an infinite combination of sounds that can be produced by the strings since there are so many combinations of notes, frequencies, and harmonies that can be produced from the vibration of the strings. This is the underlying principle of String Theory.The theory postulates that the properties of particles such as electrons, and all the other particles known to scientists at this time, are simply dependent on how the string contained within the particle is being vibrated. For example, one type of vibration might cause the particle to be an electron, while another type of vibration might cause it to be a neutrino. In short, the astounding discovery of some evidence leading to the concepts of String Theory means that we are much closer to understanding every feature of matter, which comprises the Universe.
Dwarf Planets

The IAU demoted Pluto from full fledged planet status. This created a sensational news story around the world, but the IAU’s decision was based partly on newly discovered evidence about some of the other celestial objects that orbit our Sun. Pluto was classified as a “dwarf planet,” which is an entirely new classification developed by the IAU to account for the discovery of objects that are too small to be planets but larger than asteroids.
In addition to Pluto being classified as a dwarf planet, the IAU also identified Eris as a dwarf planet as well. Eris was originally discovered in 2003 and its presence in our solar system had earned it the nickname “the 10th planet” until this new classification of a dwarf planet was invented.
Characteristics of Dwarf Planets
After much heated debate among IAU members (many of whom disagreed with the decision to demote Pluto), the term “dwarf planet” was invented to classify all of those objects which are not one of the eight dominant celestial bodies in the solar system (Mercury through Neptune) but yet still have some characteristics of planets.
The official definition of a dwarf planet is an object that has become large enough to become round due to its gravitational force, but not large enough to clear its neighborhood of nearby objects. Astronomers are concerned about the roundness of dwarf planets because an irregular shaped object, like an asteroid, will have many differences from planets. The fact that an object in the solar system is round means that there are (or were) planetary processes occurring within the object.
As of this writing, there are currently five officially named dwarf planets in our own solar system: Pluto, Eris, Ceres, Makemake, and Haumea. The IAU keeps this official list, but the list has been greeted with considerable controversy. Many astronomers argue that there are many round shaped objects in the solar system that are too small to be planets and too big to be considered asteroids.
The region of our solar system known as the Kuiper Belt is home to many of the dwarf planets. The Kuiper Belt is a disk shaped region along the outer edge of our solar system. It contains many icy bodies that orbit the area near Neptune’s orbit. Pluto and Eris are in the Kuiper Belt. The Oort Cloud is also a disk shaped region, but it lies out further past the Kuiper Belt. The Oort Cloud is considered by many astronomers to be the source of comets that exist in our solar system.
We cannot see objects in the Kuiper Belt or Oort Cloud clearly enough to determine exactly how many are round in shape. However, astronomers can estimate how large an object must become before it starts to acquire a round shape and, thus, they can estimate how many round objects are likely to be contained in this area. The dwarf planet Ceres is in the Asteroid Belt and it has a diameter of 900 kilometers. The best estimate for how big an icy body needs to be to become round comes from looking at the satellites (moons) of the giant planets. The smallest body that is generally round is Saturn’s moon Mimas, which has a diameter of only about 400 kilometers. Therefore, the consensus is that an object will become round when it reaches a diameter of approximately 400 kilometers. Therefore, the question that astronomers face now is, “How many objects in the Kuiper Belt have a diameter of 400 km?” As of today, we know of about 50 objects that meet this criterion. Therefore, even though the IAU only officially recognizes five dwarf planets, there could be potentially 50 in total, which leaves the possibility that more, likely, will be discovered in the near future.

The newly discovered dwarf planets in the solar system are very different from Earth. Most are so small that their diameters are shorter than the length of the California coastline. Approximately 30,000 dwarf planets could fit inside the Earth.
Dawn Mission
Dawn is the name given to a spacecraft launched by NASA in 2007 to explore the new dwarf planets and to look for new ones.
Vesta is the largest, and the brightest, asteroid of the Asteroid Belt. It is named for the ancient Roman goddess of the hearth. Vesta revolves around the Sun once in 3.6 Earth years in a nearly circular orbit. Its diameter is 526 kilometers, or about 15 percent of our Moon’s diameter.
Although Vesta is only about half the size of the dwarf planet Ceres, it is about four times as reflective, making it one of the brightest objects in the Asteroid Belt. Vesta is the only asteroid visible to the unaided eye.
Unlike other asteroids, Vesta actually is a protoplanet. A protoplanet is a body that began the planetary formation process but stalled due to a number of reasons. As such, a protoplanet is much smaller than Earth or any of the full fledged planets in our solar system. Vesta contains over 9 percent of the entire mass of the Asteroid Belt. The Dawn mission will continue to send back data to Earth about this important object that will give us a much clearer understanding of planetary formation, and it might lead to the discovery of other similar objects in the solar system.

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