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Nahle, N. 2006. Didactic Article: The Concept of Symmetry in Biology. Biology Cabinet Organization. New Braunfels, TX. http://www.biocab.org/Symmetry_Asymmetry.html. No. 260.
Published: 29th October 2006. Last Update: 9th February 2009.
The Concept of Symmetry in Biology.
C1-L by Harvard University in Scientific ICAM Research.
(Additional editing of this English text by TS)
Symmetry refers to the homogeneity of a system.
All living beings and all their thermal states are asymmetric.
We say that a system is symmetric when each of its parts offers identical effects, characteristics and conditions through the rest of its parts, anywhere and every time that the system exists or produces its influences.
The transition from a state where the most minimum value in which the symmetric system resides on the point of zero toward a state of asymmetry with a value from almost zero to one -or close to one- is called “Symmetry Breaking". (Barrow; 2000). 1
The laws of Nature are symmetrical because they produce their effects in the same way, at every place and every moment in the Universe; however, the results of the symmetrical laws are asymmetrical systems (states and/or structures).
There is no special place in the Universe where the laws of Nature behave differently, that is to say, where the laws behave asymmetrically. Nature’s laws operate generating a vast range of systems and states which are complicatedly asymmetrical.
Consequently, the Universe started out from a symmetric state, that is to say, in a minimum zero value. (Randall et al; 1996) 2. Time has never been symmetric because it has always been different from zero.
In this Universe, time would always adopt a value distinct from zero. If we could go back in time, splitting it into smaller and smaller parts of time, we would always be left with a minimal fraction of time, but we would never arrive at an absolute zero of time. So, the mathematical concept of time is infinite if we implement it en route for processes presently occurring in the Universe and before it started off, as long as we understand that time is the trajectory of the entropy of the Universe. (Hivon & Kamionkowski; 2002). 3
The idea of a Universe beginning from a Big Bang or from a series of Big-Bangs is mathematically possible, but unfeasible in Nature. It is not rare to find this kind of inconsistency between the procedures created by the human mind and Nature in the real. Our observations of the Universe indicate that the Universe began an expansion of indefinite duration once it had started off from a bubble of false vacuum (false void).
That there could be a prior Universe from which our Universe emerged, and another Universe earlier than the universe that brought about our Universe, is only a hypothesis, but it has a bulk of evidence. (See figure 2)
There are no symmetric structures or states in the real Universe. To exist, a state or a system must be asymmetric in relation to the symmetry of Nature’s laws. (See figure 1)
Living beings are not systems stretched out from the field of action of those symmetrical laws. All states and structures in the Universe are subject to the laws of Nature, even when they are asymmetrical systems.
Our Universe grew out from a black hole produced in an older and bigger Universe. The history goes something like this:
1. A black hole is an asymmetric connection between two bubbles of false vacuum (false void).
2. When the temperature of the black hole increased to more than 10^34 K, the particles with mass (hadrons) comprised by the system, separated into elementary particles without mass (gluons, quarks and photons).
3. The particles formed together a symmetric gluon-quark-plasma into the horizon of the black hole and a bubble of false vacuum (false void) formed that extended “out” from the Mother Universe through a highly unstable wormhole.
4. The highly unstable wormhole disappeared after a few microseconds of existence, separating the bubble of quark gluon plasma from the ancient Universe to form another asymmetric system.
5. The temperature of the quark-gluon plasma decreased and adopted an asymmetric liquid-like phase whose enormous internal pressures drove the whole system into an accelerated expansion.
6. Then a new asymmetric structure (our Universe) began to exist. Quarks and gluons gathered to form asymmetries which are those familiar particles with mass, such as protons, neutrons, electrons, neutrinos, positrons, etc.
7. As the system speedily expanded, the temperature decreased and the formation of more asymmetric structures (galaxies) with billions of more asymmetric structures (stars) was possible.
8. The laws that generated those asymmetric structures remain symmetrical at present.
9. Perhaps many of the stellar systems inside galaxies are hospitable to living beings and, perhaps, many of the worlds forming part of those stellar systems hold living beings.
10. At least, one planet in one stellar system has living beings, the Earth.
11. Many universes will breed from our Universe; perhaps many young universes have already arisen from our Universe in the past. Who knows?
That “who knows?” refers to our inability to see or detect universes beyond the horizon of our own Universe, or the universe that engendered our Universe, as the bend of the horizon of our Universe renders it unobservable from our place in the cosmos.
SYMMETRY ASYMMETRY IN LIVING BEINGS
When we talk about thermodynamics, which is the branch of physics that examines the correlations and transformations between heat and other forms of energy, we think that we are asymmetric Biosystems (living beings). In biology, the symmetric term may refer to three different States:
1. Anatomical Symmetry which refers to the arrangement of organs or organelles in an individual that is isotropic from any angle of the observed biosystem.
2. Dynamical symmetry, which refers to the absence of rotational variance. This means that there are no observable differences at the molecular level even if the biosystem is in motion.
3. Energetic symmetry, which says that the flow and the density of the internal energy of a biosystem is indistinguishable from the flow and the density of the energy of the environment.
On the first state or the state of anatomical symmetry, we could assure that there are not absolutely spatially symmetrical biosystems. Differences of the dimensions and arrangement of organs and organelles of a Biosystems always exist. For example, human beings have a liver at the upper right side of the abdomen which is not at the left side; in addition, when we look at bilateral organs, a body is different in size and functionality with the homologous organ; e.g. a kidney will work with greater capacity than the other, or will be smaller than the other, etc.
Regarding the state of dynamic symmetry, we find that this kind of symmetry does not exist in living beings since the differences between the angles and between the dimensions of the structures allow the display of any rotational movement of the biosystem.
Focusing on the third type of symmetry, or energetic symmetry, we also notice a rotating variance of the flow and internal energy densities of any living being. The rotating variance is anisotropic because it always occurs on a preferred directionality of flux of energy and a specific density of energy that permits us to maintain our internal energy in a quasi-stable state, i.e. with minimal variations.
Scientists believe that life is the result of a rupture of the symmetry of molecular conglomerates with peculiar characteristics; for example, the acquisition, storage, and autonomous manipulation of the energy taken from the environment. By means of the rupture of the thermal symmetry, the living beings were not more abiotic particles squeezed together inside small globules that we call microspheres, which lacked rotational variance and were indistinguishable one from the other.
At some point of the cooling process of the environment, the biomolecules met into asymmetric sets. Some of those sets could resist returning to the symmetry through the control of the energy obtained from their environment for maintaining their internal energy density in a quasi-stable and asymmetrical state relative to the universe.
If we gradually increase the temperature of a biosystem, we could reach the point at which the biosystem would lose its functionality and it would die. This is because we altered the state produced by the rupture of the symmetry. If we continue increasing the temperature yet after the biosystem had died, it will disintegrate and will constitute spatially-symmetric portions. If we continue increasing the temperature until reaching a point at which ionization happens, the original symmetry of the system will be reacquired. Thus, increasing the temperature of any system causes the recovery of its symmetry, while the cooling of a system causes the symmetry rupture, i.e. the system becomes asymmetric with respect to the universe.
REFERENCES
1. Barrow, John D. The Book of Nothing. Pantheon Books; 2000, New York, New York.
2. Randall Lisa, Soljacic, Marin, and Guth, Alan H. (MIT). Supernatural Inflation: Inflation from Supersymmetry with No (Very) Small Parameters. 1996, Nuclear Physics B472, 377-408.
3. Hivon, E. and Kamionkowski, M. A New Window to the Early Universe. Science; 15 November 2002: Vol. 298. No. 5597, pp. 1349 - 1350.
