What Is Symmetry?
Physicists usually define symmetry as the invariance under transformation. Simply put: Remaining unchanged after a change. The basic example is time“translation invariance, which states that the homogeneity of time symmetry leads to the invariance principle that nature's laws always remain the same Thus, they are independent of when we measure them.
Let's assume that we measure and record a pendulum's movement today. If we do this tomorrow or even next week under the same conditions, we always will obtain the same result. Without symmetry's principles, for instance the time“translation invariance, a computer built today most probably would not work tomorrow. We could not even build a computer, a calculator, or a watch, for nature's laws would be in a state of random change at every moment. Nor could we guarantee that gravity would not turn into a repulsive force in the next moment.
Another basic example is the space“translation invariance. Space has the symmetries of homogeneity (being the same at every location) and isotropy (being the same in every direction). As a result, laws are independent of where we measure them, for whether we are in America or China, we use the same formulae: F= m.a, S= k.log W, E= m.c ...
Why Does the Universe Behave the Same at Every Instant and at Every Point in Space“Time?
Materialists reply: Because laws under space“ time translations are invariable. This will bring another why, answered by: Because of homogeneity and isotropy. Such a pattern will continue, for each question is no more than an effect ready to be explained by a cause, and each answer (cause) will appear to be another cause's effect.
Followers of Aristotle, Plato, Ibn-i Sina (Avicenna), al-Farabi (Al-Pharabius), or the Illuminist philosophers will urge you to keep asking why. The point at which you stop asking will be your destination, where you reach the initiator: God. All answers to your previous questions, when taken together, turn out to be attempts to attribute intermediaries or partners to God. If you ask those who believe in God's Oneness and give causes no share in His Dominion, you will hear: The same laws, being seen at every point and at every instant, can be explained only if there is one God governing every point at every instant with His universal Will, absolute Power, and all-encompassing Knowledge. Thus all causes, bound to each other so that they can be understood, are bound directly to God, Who is not bound by space“time.
Why Is the Universe Accessible to Us through Laws?
While new symmetries were being revealed, skeptical scientists were wondering whether symmetry in nature's laws on a macroscopic scale is valid on a microscopic scale.
Every symmetry is associated with a conservation law, the most important one being energy conservation. This implies a symmetry in time-translation. The validity of energy conservation has been proven on the microscopic level. One of the latest verifications is that in a perfect vacuum, particle and antiparticle pairs are created and annihilated constantly. In other words, microsized Big Bangs occur all the time out of the vacuum. This does not violate energy conservation or the laws of quantum mechanics. If they were somehow violated, and if we did not see the same concepts as the result of symmetries, the similar formalism, and the same techniques from micro- to macroscales, we could not comprehend the universe.
Consider Einstein's amazement at this: The most incomprehensible thing about the universe is that it is comprehensible. Even the most atheistic scientist accepts that the universe is not absurd. But why is universe comprehensible and accessible to us?
Atheists and materialists believe that we come into being from nothing, by nothing, and for nothing, and so consider such questions meaningless. However, people who unify everything in God's name can assert: God cannot be comprehended fully by humans, and so wills to be comprehended and known through His art and the system and order apparent in the form of laws. We are here to comprehend, and the universe lies open. In the words of Paul Davies, author of The Mind of God, we are meant to be here.
What Is the Consequence of the Matter“Antimatter Asymmetry?
Existing theory says that every particle has a corresponding antiparticle. Physicists believe that particle“antiparticle pairs behave symmetrically, like mirror reflections of each other (mirror-reflection symmetry). In 1964 at Doe's Brookhaven Laboratory, when a slight but definite asymmetry between a subatomic particle and its antiparticle was noted, physicists saw the breaking of symmetry in nature. It was time to ask why.
It is now thought that this asymmetry may be responsible for matter's dominance in the universe. Our universe appears to be made entirely of matter. If there were substantial amounts of antimatter on Earth, we would be annihilated as we react with our antiparticles, for particle“antiparticle pairs annihilate each other when reacting and leave behind electromagnetic radiation.
Any explanation offered for this asymmetry must account for the asymmetry in the universe's earlier periods, beginning with the Big Bang. Astrophysicists think that certain massive particles, formed soon after the Big Bang, decayed in such a way that slightly more particles than antiparticles were created. Even though this asymmetry's exact origin is unknown, we do know that if symmetry were not broken, we would not be alive. Amazingly, the laws of physics allow life to exist.
Does Time Flow from the Past to the Future?
Time-asymmetry is perhaps the most fascinating. Even though all successful physics equations are symmetric with respect to time, we perceive time as flowing from the past to the future: Newton sees the apple fall down, people grow old, we throw the stone and the window is broken. Newton used a time arrow to distinguish between time's forward and backward directions. Einstein preferred a time river that meanders as it passes massive objects. But this sounded unscientific: past, present, and future are only illusions.(1)
Roger Penrose, a prominent mathematician and quantum theorist, suggests that our perception of time as flowing irreversibly from the past to the future should have something to do with quantum mechanics and consciousness. This is quite similar to Einstein”but more scientific. Along with many others, Penrose and Hawking have discussed the issue at great length. Hawking says that the observed difference between past and future must come from the universe's boundary conditions. Since the Big Bang was the beginning of creation of matter and energy, and space and time, the reason should lie there. They disagree on the underlying reason for time-asymmetry, but agree that the quantum theory of gravity is needed to describe the complete nature of space-time.
What Is Supersymmetry?
Einstein spent his last days trying to synthesize quantum theory and gravity to find a quantum theory of gravity. Despite great advances, such a theory remains elusive. This has guided them to the so-called theory of everything, which combines the four fundamental forces: nuclear, electromagnetic, weak, and gravitational. Theories describing the unification of the nuclear, electromagnetic, and weak forces are called grand unified theories (GUTs). The unification of these forces require the unification of symmetries, known as supersymmetry.
However, a large problem arises when trying to add gravity. This is because gravity is located in the field of general relativity, the theory of galaxies, quasars, and black holes, while the other three fundamental forces are described by quantum theory, the theory of the very small, which accepts subatomic particles as point-like particles. Nevertheless, this theory of everything should combine general relativity and quantum mechanics.
Unfortunately, it is not that simple. Right now, the most elegant idea for such a theory is supersymmetric string theory, in which point-like particles in quantum mechanics are replaced with string-like entities. Different vibratory resonances on these strings correspond to different particles in the same way as different frequencies correspond to different notes on a violin string. These strings, however, are not connected to the ends of a cosmic violin, but float in space“time. When they float, they warp space“time as predicted by general relativity. Thus strings unify the quantum theory of particles and general relativity.
Once the theory of everything is completed with its supersymmetry, we might be able to explain many mysteries, among them the existence of atoms, molecules, and dark matter,2 and the asymmetry between matter and antimatter. If we succeed, one more step will have been taken toward time travel. Even DNA, whose double-helix structure is interpreted under X-ray crystallography, which is a fruit of crystal lattice symmetries, may reach a full description with sypersymmetric string theory.
In the near future, if supersymmetric string theory is completed both experimentally and theoretically, we will be able to express bravely that all forces in nature are different aspects of the same thing. Scientists and believers in God's Oneness will adopt this theory, for such a comprehensive unification takes us to God's Unity.
Symmetry, which is displayed in art, music, inorganic and organic nature, always has been fascinating to the human mind. Space“time, upon which all laws are displayed, also is constructed on the basis of symmetry. This construction brings an amazing result: the universe behaves the same at every instant and at every pont. Through symmetry, we witness unity, harmony, and perfection. Ironically, the breaking of symmetry (asymetery) is not the braking of prefection, for the universe's perfection is completed with asymmetry, the outcome of which is human life. Today, we human beings are looking for a supersymmetic string theory that will reveal the underlying unity beneath the diverse creation.
1 Escape from the Quantum Whirlpool, New Scientist (April 1997). Included in Robert B. Leighton (contributor), et al., The Feymann Lectures in Physics, Symmetry in Physical Laws (Addison- Wesley: 1964).
2 Astronomers calculate the mass and velocity of galaxies or distant stars by detecting their spectrums and redshifts. However, they discovered that the high velocities of galaxy clusters cannot be explained fully by their calculated masses. As a result, they posit the existence of dark matter surrounding galaxies. As this dark matter does not radiate, it is not detected in the electromagnetic spectrum. It is expected that one of the supersymmetric particles (the neutralino) might make up the missing dark matter in the universe.
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