![]() By Jasper Chen Have you ever wondered about the mechanisms that govern the behavior of the world around you? Theory has it that about 13.8 billion years ago, an infinitely dense and unimaginably small entity expanded into an extremely hot state (10,000 million degrees, 1,000 times the temperature of the center of the sun) that grew unimaginably fast: a few light years across in one second of time (this rate is continually increasing). This is known as the Big Bang, and it marks the start of time. Current theories cannot handle the infinite density of the entity, a mathematical singularity (or simply an undefined object), and the theories are therefore unable to “predict” certain properties of the era before the Big Bang. It also gave rise to the four fundamental forces that act as the basis of virtually every single phenomenon that human kinds have managed to discover: the weak force, the strong force, the electromagnetic force, and the gravitational force. They all have crucial roles in shaping the world around us. During the first 10^(-43) seconds, or one ten-million-trillion-trillion-trillionth of a second of a second after the Big Bang, the four fundamental forces of nature were united into a single, grand force. This period of time is known as the Planck Epoch, named after the German scientist Max Planck. However, as time moves past this miniscule amount of period in time, the gravitational force separated from the grand force, then from the Strong Force and lastly from the electromagnetic force. The four fundamental forces started to take forms in the way we experience them today as the universe starts to cool from the blazing state. The Gravitational ForceThe gravitational force (the weakest of all four) will be discussed first, as it is the most familiar to the average person. In 1687, Newton presented his universal law of gravitation in his Philosophiae Naturalis Principia Mathematica. It states that there is a mutual force of attraction between any two bodies, proportional to their masses and inversely proportional to the distance between them, and that gravity has an infinite range, which can be shown mathematically as Fg=G(M1)(M2)/r^2, where G is the gravitational constant (an experimentally determined number), M1 and M2 are the masses of the bodies, and r is the distance between them. Nevertheless, Newton did not know precisely how gravity worked, though he came up with an mostly accurate description of it. Problems arose as phenomenons that Newtonian gravity failed to predict, such as gravitational lensing (bending of light near massive celestial bodies). It was not until about two centuries later in 1915 did Albert Einstein publish his papers on the theory of general relativity, which revealed the mechanism behind gravity. Paul Dirac, a fundamental figure in the development of quantum mechanics, described general relativity as “the greatest scientific discovery that was ever made”. Improving on Newton’s universal law of gravitation, general relativity stated that gravity was caused by curvatures in space-time created by bodies where the sizes of the curvatures are proportional to the masses of the bodies. Think of space-time as a piece of stretchable fabric with immense area. When you drop a marble (represents a mass in spacetime) onto the fabric, it creates a curvature, and whatever is around it will fall towards it. This theory explains the phenomenons such as gravitational lensing, where light rays are bent when passing through the curvatures created by celestial bodies. Gravity is responsible for the forming of celestial bodies. If gravity did not exist, then humankind would not exist. THe Weak ForceDespite its name, the weak force (also called weak interaction) is much stronger than the Gravitational Force, but is only effective in short distances, thus receiving its name. This interaction is extremely crucial to the structure of the universe in that most of the stars (such as the sun) and heavy atoms would not exist if weak interactions were nonexistent. The reason for this is the weak interaction is the only mean by which quarks (the particles that make up protons, neutrons and more) can change flavors (this is a randomly decided name given to the set of characteristics of quarks that decide what particles they would make up, they have nothing to do with actual flavors). The weak force thus has an important role in transmutation of atoms (simply the transformations of an atom of one kind to another). One of the most common weak Interactions is beta decay, the process by which a neutron transmutates into a proton by changing a down (a flavor) quark to an up (another flavor) quark; for example, when a phosphorus atom (atomic number 15) undergoes beta decay, it becomes a sulfur atom (atomic number 16). It is crucial in the mechanism of the sun as well; in the process of fusing two deuteriums (isotopes of hydrogen) together to make a helium atom and releasing energy, a transmutation of hydrogen to deuterium under weak interaction is necessary. Otherwise, the sun would not shine and release heat, and humans would not exist. The Strong ForceThen comes the strong force (also called strong interaction). As its name suggests, it is the strongest force among the four forces, being one million times stronger than weak force and roughly 1039 times stronger than Gravitational Force, but with the shortest effective range—the distance roughly equal to diameter of a proton. The strong force is rather straightforward, it is the force the holds subatomic particles together. Given that like charges repel and atom nuclei are made up of protons and neutrons, then the positively charged protons should logically exert a force of repulsion on each other and be unable to make an atom nuclei, but the strong force prevents the particles from flying apart. The strong force is mediated by the exchange of massless particles called gluons between subatomic particles. In addition, on a smaller scale, the strong force is also the force that holds quarks together to make protons and neutrons, specifically called the color force. Again, if this force did not exist, then humans would not exist, since virtually no atoms would exist either. The ELectromagnetic ForceLastly, the electromagnetic force (or electromagnetism) is the force resulting from combined electric and magnetic fields, and is responsible for every single phenomenon one would encounter above a nuclear scale with the exception of gravity. Visible light is a prime example of electromagnetism: it is a type of electromagnetic radiation (ER) that is a portion of the electromagnetic spectrum. ER is caused by oscillations (or waves) in electric and magnetic fields that propagate throughout all space at the speed of light, and visible light only occupies a relatively small portion of the electromagnetic spectrum. Like gravity, electromagnetism has an infinite range—if a proton exists in space, then every single electron must feel some attraction and just like gravity, the magnitude of the force falls off quickly as distance increases. Electromagnetism accounts for your ability to hold things, all forms of chemical reactions and many more phenomenons, again playing an important role in human lives, just like every other fundamental force. Scientists today have managed to achieve unification of all the forces except for Gravitational Force in the Grand Unified Theory. They aim to develop a theory of quantum gravity, which allows the unification of all four forces—the theory of everything, which Einstein spent most of his life attempting to find. CITATIONSEinstein, Albert, et al. “Foundation of General Relativity.” The Collected Papers of Albert Einstein. English Translation: The Berlin Years: Writings, 1914-1917, translated by Alfred Engel, Princeton Univ. Press, 1989, pp. 146–199. “Essay: Newton vs. Einstein vs. the Next Wave.” AMNH, www.amnh.org/explore/science-bulletins/astro/documentaries/gravity-making-waves/essay-newton-vs.-einstein-vs.-the-next-wave/. Fundamental Forces, hyperphysics.phy-astr.gsu.edu/hbase/Forces/funfor.html. “General Relativity.” Wikipedia, Wikimedia Foundation, 10 Nov. 2017, en.wikipedia.org/wiki/General_relativity. “Newton's Law of Universal Gravitation.” Wikipedia, Wikimedia Foundation, 4 Nov. 2017, en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation. The Strong Nuclear Force, aether.lbl.gov/elements/stellar/strong/strong.html. Hawking, Stephen. A Brief History of Time. Bantam Books, 2017. Tyson, Neil deGrasse. “The Greatest Story Ever Told.” Astrophysics for People in a Hurry, W.W. Norton & Company, 2017, pp. 17–33. ALL IMAGES BELONG TO THEIR RESPECTIVE OWNERS. SUGGESTED READING“Grand Unification: An Elusive Trail.” Grand Unification: An Elusive Trail, www.mosaicsciencemagazine.org/pdf/m10_05_79_01.pdf
Boer, W. de. Grand Unified Theories and Supersymmetry in Particle Physics and Cosmology. Mar. 1994, www-ekp.physik.uni-karlsruhe.de/~deboer/html/Lehre/Susy/deboer_review3.pdf
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