From the Unity of Nature's Elements in Empedocles to a Unified Theory of Everything In

FROM THE UNITY OF NATURE’S ELEMENTS IN EMPEDOCLES TO A UNIFIED THEORY OF EVERYTHING IN MODERN PHYSICS

Panou, E. 1, Kalachanis, K. 1, Theodossiou, E. 1, Kostikas, I. 1, Manimanis. V.N.1 and Dimitrijević, M.2

1National and Kapodistrian University of Athens, School of Physics, Department of Astrophysics, Astronomy and Mechanics, Panepistimiopolis, Zographos 15784, Athens, Greece 2Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia

Abstract: Empedocles considered the four ‘classical’ elements of which the world consists as united. This unification creates the imaginary world of Sphere. This situation existed before the explicit presence of the four elements and was the cause for the creation of everything. Nowadays researchers in Particle Physics construct accelerators that can perform collisions of particles at high energies. Physicists believe that initially the four forces in nature were unified and due to the existence of a disorder were activated and created our Universe. So, both the philosophy of Empedocles and modern scientific research seek to uncover and explore the underlying unity of the natural world, which is not perceived by the human senses.

Key words: Empedocles, Sphaerus, Forces of Nature, Unified Theories

1. INTRODUCTION

Empedocles, one of the prime intellectuals of the pre-Socratic philosophical thought, was born in Agrigentum (Acragas), Sicily, in circa 495 BC to an upper-class family and he died in Peloponnese in circa 435 BC. His family was instrumental in preventing a group of aristocrats from overthrowing the regime. According to Diogenes Laërtius, Empedocles was a student of Pythagoras, from the School of whom he was expelled on the charge of plagiarism (Diogenes Laërtius, Vitae Philosophorum, VIΙI, 54). The Empedoclean philosophical system is based on combining pre-Socratic thought –especially of the Heraclitean view of the constant flux and movement of the beings– with the Eleatic views of the world as the expression of a static ‘being’ (είναι) ( Theodossiou 2007: 81). The main work by Empedocles consists of two texts totaling 5,000 verses, of which about 550 survive: 1) On Nature, where the theory of the four elements is exposed, and 2) Purifications, a work on the soul. Additionally, he authored a Medical Speech of 600 verses (Diogenes Laërtius, Vitae Philosophorum, VIΙI, 77). Empedocles is well-known for his theory that the world originated from four rhizōmata (Fire, Air, Water and Earth). The interesting point of his teaching is his belief in the existence of a unity among the fundamental elements of the world. Correspondingly, modern Quantum Physics and high-technology systems, such as particle accelerators, proved the existence of fundamental building blocks of matter, which interact through four fundamental forces or ‘interactions’. The great challenge for Modern Physics is the unification of these forces in order to approach the underlying unity of the natural world. In this work the Empedoclean theory on the fundamental elements of nature is examined first and then its unification, which creates the state of Sphere. Next, the 1 modern view of the elementary-particle world is described along with its fundamental interactions, whose unification would contribute to the formulation of the ‘Theory of Everything’. Finally, the common basis of the two views of the world is stressed, as the idea of the unity of the natural world seems to be described by both Philosophy and Modern Physics.

2.THE FUNDAMENTAL CLASSICAL ELEMENTS OF THE UNIVERSE: THE ‘ROOTS’

The important contribution of the pre-Socratic philosophers in both Science and Philosophy lies in their attempt to find the reasons for the existence of the beings by seeking the laws that cause the natural phenomena. The Greek thought during its early period (Orpheus, Hesiod) symbolized the cosmic forces through myth and later on proceeded to the stage of scientific thought with the Ionian Presocratic philosophers. According to A. Comte the human thought follows three evolutionary stages: the theological, the metaphysical and the positive one. In the last stage, in which begins the attempt to explain the natural phenomena in a scientific way, belongs the effort of the Presocratics for the determination of the origins of the world (Koutras 1995: 36). Aristotle writes about this topic that it is a necessity for one or more origins to exist (Aristotle, Physica: 184b, 15). One of the theories that support the existence of more than one origins is the one expressed by Empedocles. According to him, the origins of the world could be traced back to the four elements or (according to his own phrasing) rhizōmata (roots): Earth, Water, Air and Fire, which are, according to a modern evaluation of the Empedoclean philosophy, “the ultimate elements of matter, since they cannot be analyzed into simpler ones” (Makrygiannis 2000: 395). Friedrich Nieztche notes on this subject that in the thought of Empedocles there are influences by Anaxagoras, since things for him “are just a mixture of primal elements, but not anymore to an infinite degree, but of only four uniformities” (Nieztche, 1975: 135). This teaching is found in both the ancient Greek (‘gentile’) and the Christian philosophical thought, a fact that testifies to its importance as an influence for the subsequent European thought and culture. Aetius the doxographer mentions that Empedocles had corresponded the four elements to four deities in the following way (Aetius, De Plac. 1,3,14 (DK 31 [21] B6):

Fire Air Earth Water Zeus Juno Aïdoneus Nestis

However, the correspondence given by Diogenes Laërtius is different (Diogenes Laërtius, Vitae Philosophorum, VIΙI, 76, 6-7):

Fire Air Earth Water Zeus Aïdoneus Juno Nestis

Although in the writings of Empedocles the elements correspond to deities, Athenagoras of Athens (2nd century AD), suggests that the four elements are not gods, but rather “from matter separated into parts by God is their constitution and origin” (Athenagoras, Legatio and De Resurrectione, 22, 2, 4). Therefore, when Empedocles writes about the elements, in reality he is not meaning gods, but the structural elements of matter, which (probably for symbolic reasons) he connected with the

2 deities. Such a theory about the elements is supported by John Philoponus (490-570), according to whom Empedocles regarded their names as symbolic (Philoponus In Aristotelis De Anima, 74, 11). Similar is the view of Clement of Alexandria, according to whom the barbarians and the Greeks alike concealed the origins of matter and they used symbols, metaphors and riddles for them, just as Apollo the god did (under the epithet of Loxias) (Clement of Alexandria, Stromateis, V, 4, 21, 4, 1-5). Therefore, it seems most probable that Empedocles with his four elements refers symbolically to the powers of nature rather than literally to four material constituents that are readily perceivable through the human senses. Modern scholars Raven and Schofield proceed even further, to state that the correspondence of the elements with deities aims to indicate that in reality the four elements are indefinite forces of nature (Kirk, Raven and Schofield, 2001: 294). A prime position among the four elements is reserved for fire, a fact indicated in a reference by Aristotle to Empedocles, according to which the latter actually treated the elements as two, i.e. on the one side the fire and on the other side the rest three (Aristotle, Physica, 985a, 31-34). Several decades after Empedocles, Plato assigned a principal significance not only to Fire but to Earth as well, regarding them as fundamental elements, while in parallel Air and Water are regarded as factors of harmony between the Fire and the Earth (Kalachanis, 2011: 107), a harmony (in the sense of peaceful unity and concord) achieved through the right proportions in the mixing of the different elements. This right proportion can be phrased as follows: The ratio that exists between Fire and Air must exist between Air and Water, and correspondingly must be the same between Water and Earth.

F/Α =Α/W= W/E

This proportion contributes to the creation of a harmonic world/Universe, which cannot be destroyed by any other power except by its own Creator (Plato, Timaeus, 31b-32c). Such was the importance assigned by Empedocles to fire, that Hippolytus of Rome writes that the Presocratic philosopher described God as “intelligible fire of the monad, and that all things consist of fire and will be resolved into fire; with which opinion the Stoics likewise almost agree, expecting a conflagration” (Hippolytus, Refutatio omnium Haeresium, I 3). Therefore the element of fire is first of all divine as carrier of the divine energy, but on the other hand it forms the substrate of the changes of the cosmic system. According to the above passage by Hippolytus, the Stoics repeated the views of Empedocles on conflagrations. In summary, the central idea of the cosmic system proposed by Empedocles, is the presence of four basic structural elements of matter, symbolized by the four elements, whose mixing and separation contribute to the creation of the beings (Aetius, De Plac. Ι 30, 1 (Β8) )

3. THE UNITY OF THE ELEMENTS – THE SPHAERUS (SPHERE)

According to Empedocles the four elements are not static but they exist under the influence of a pair of antagonistic powers, namely the Amity (Greek: philotes, also referred to as Love) and the Strife (Greek: neikos). These powers are essentially the factors that cause the mixing, the variations and the combinations of the elements. Amity, which contributes to the unification of the four elements, produces a perfect world, as opposed to Strife, which disrupts this unity, producing the many out of the

3 one (Hippolytus, Refutatio omnium Haeresium, 7,29,8- 7,29,9,2). Empedocles clearly refers in his work to the interchange of unity and differentiation in nature (Simplicius, In Aristotelis Physicorum 158, 13-16), which is called ‘Empedocles’ cosmic cycle’ Kirk, Raven and Schofield, 2001: 296). Between these two states, the state of complete harmony and the state of complete differentiation, Empedocles places the origin of beings, speaking of two worlds, one ‘united and perceivable by the intellect’ and one ‘differentiated and perceivable by the senses’ (Georgoulis, 2000: 97). The stage during which Amity prevails and the elements of the world are united is called by Empedocles Sphaerus. The main properties of Sphaerus are the following: 1. It is a ‘quality without characteristics’, since inside it all elements lose their “own special character” (Philoponus, Ιn De Generatione et Corruptione, 19, 9-30). Simplicius moreover writes that, according to Eudemus, when “all join together, then nothing can be seen, neither the sun, nor the forest life on land or the sea. Thus the circular Sphaerus has got support in the dense bossom of Harmony, rejoicing in his solitude” [Simplicius, In Aristotelis Physicorum 1183, 28 (Β27)]. As Sphaerus has no qualities, it follows that his nature is different from the nature of the four elements. 2. Sphaerus is a ‘world that can be perceived with the intellect’ and an ‘archetype’ of the world that is perceivable through the senses (Ibid, 31, 18-19). It follows that Sphaerus is ‘superior’ to the material world as being its archetype and has a mental nature that cannot be approached through the five senses. 3. Sphaerus is ‘self-equal’ (Hippolytus, Refutatio omnium Haeresium 7, 29, 13.), a property certainly connected to the spherical shape; therefore, Sphaerus should be characterized by uniformity and symmetry in all aspects. 4. According to Simplicius, Empedocles exalts Sphaerus as god (Simplicius, In Libros Aristotelis De Anima 70, 17), a fact that contradicts with his destructible nature due to the disruption caused by the Strife. In another source (Ammonius) it is mentioned that, according to Empedocles, there is a reason ‘above the intellect’ called the ‘holy mind’. In this context, the destructibility of Sphaerus does not negate the presence of the divine element in the cosmic composition (Ammonius, in Aristotelis De Interpretatione Commentarius 249, 9). Since Sphaerus is not a god due to the damage caused by the Strife, he may well symbolize an intermediate state between the (Creator) God and the cosmic creation, a state characterized by symmetry, perfectness and transcending nature as compared with the four elements. Therefore, based on the Empedoclean theory, the Universe should pass from a state of perfectness and symmetry before assuming the from that can be sensed by the human senses. This phase or stage of perfectness of the Universe does not last forever, because eventually the Strife acts in a disrupting way, resulting in a state called ‘acosmia’ by Empedocles (Empedocles DK Β 27, 4). The alternation between the stages of Amity and Strife is based on an oath, a fact denoting the existence of an inviolable natural law, which regulates the disruption and the unification of the elements (Aristotle Metaphysics, 1000b, 14-15 (DK 31[21] B 30) ). When the Strife acts a movement takes place, which starts the separation of the elements. More specifically, “when the Strife reached the depth of the whirl and Amity appeared in the middle of the whirl, everything started to unite and becoming one, not suddenly, but by merging at will. From their merging, thousands of mortal nations sprouted. Yet, many which had not merged were alternating with the merging others: these were the ones held by Strife, because it had not retreated to the ultimate limits of the circle, but instead it stayed in other locations, while it had left other places. It was running away, chased by the immortal momentum of Amity. Then became mortal those beings which were

4 immortal before…” (Simplicius In Aristotelis De Caelo 529, 1-15). This passage suggests that a whirl contributed to the creation of an initial mixture characterized by an incessant movement. But mainly it signals the change of the state of beings from immortality to mortality, a shift that can be interpreted as the passage of the world from the state of the non-perceivable to a state perceivable by the senses. After the whirl formed, the air appeared first, then the fire and the earth after them. The earth element, because it was compressed by the continuous rotation, gushed up the water (Aetius De Plac. ΙΙ, 6, 3 (DK 31a 49). The second stage of the Empedoclean cosmogony corresponds to the creation of the sensed or visible world, in which the presence of the Sun stands out: the Sun is the first being separated from the mixture. After it, appeared “all the other visible entities, the land, the sea with its many waves, the moist air and the Titanic aether, which circularly clasps everything” (Clement of Alexandria Stromateis, V, 8, 43, 3, 3). Aetius offers another version for the creation of the sensed world, according to which “from the evaporation of water originated the air, the sun originated from the fire and the earthly bodies from the rest” [Aetius De Plac. II, 6, 3 (DK 31a 49)]. From this exposition it can be summarized that the basic elements of the world (Fire, Air, Water, Earth) originate from a state inaccessible by the senses (Sphaerus), which is disrupted and dissolved by the power of the Strife. However, in their creation contributes the whirling of the original mixture caused by the action of the Strife.

4.MODERN PHYSICS ON THE FUNDAMENTAL FORCES OF NATURE

Physicists, aided by the impressive technological progress and by the formulation of the scientific theories of Quantum Physics, study the fundamental structure of matter. The ultimate particles of matter that have been discovered up to now are the quarks (q) and the leptons, the elementary components of our world to the best of our knowledge. The elementary particles are further classified based on their quantum spin number, into bosons and fermions (Burcham and Jobes, 1995: 224). The particles, depending on their level of composite structure, are also classified into hadrons and leptons. The hadrons are composed from quarks held together by the strong nuclear force. Depending on the number of quarks they contain, hadrons are called baryons or mesons. The baryons (qqq) contain 3 quarks, while the mesons ( qq ) contain one quark and one anti-quark (the anti-quark has the same mass as the quark, but the opposite electric charge). The leptons are the lighter particles, while the baryons are the heaviest ones. The model of quarks was proposed independently by the physicists Murray Gell- Man and George Zweig in 1964 (Griffiths 2008: 37-43). George Zweig had called these particles aces, while Murray Gell-Man called them quarks, from the novel Finnegans Wake by James Joyce (‘Three quarks for Muster Mark!’, Book 2, episode 4).

5 Particle classification based on their elementary Particle classification structure based on quantum spin Particle Symbol Particles Photon γ Fermions Bosons Leptons Electron e-

Neutrino of the electron νe Muon μ-

Neutrino of the muon νμ Tau τ-

Neutrino of the tau ντ Hadrons Baryons Proton p Neutron n Lambda Λ0 Sigma Σ0, Σ± Xi Ξ0, Ξ- Omega Ω- Mesons Pions π±, π0 ± 0 0 Kaons Κ , Κ S, Κ L Eta η0 There are 6 kinds of quarks: u (up-quark), d (down-quark), s (strange-quark), c (charm-quark), t (top-quark) και b (bottom-quark). The structure of proton and neutron, the two kinds of particles that comprise the atomic nuclei, are (uud) and (udd), respectively. In other words, the proton is a baryon that contains 2 ‘up quarks’ and one ‘down quark’, while the neutron is a baryon containing 1 up quark and 2 down quarks (Burcham and Jobes, 1995: 232). Since two are three quarks of the same kind cannot coexist, one more quantum number was introduced: ‘color’ (no relation at all with the usual meaning of the word). There are only 3 such ‘colors’: red (R), green (G) and blue (B). Each baryon contains one R, one G and one B quark, so as a whole it is ‘colorless’ (Burcham and Jobes, 1995: 233). The effort to identify all the elementary particles as the sole constituents of all bodies in the Universe is quite significant. However, it is also important to determine which were the forces that led to the formation of the first simple structures and later, to the production of more complex entities: from protons and neutrons to nuclei, atoms and molecules, which compose the microscopic world. In subsequent stages, these structures combine to produce stars, planets and living creatures (Chrysis, 1996: 118). Since 1950 the structure and the phenomena of the world are described as the result of the existence of four fundamental interactions or forces: the gravity or gravitational force (G), the electromagnetic force (Ε), the strong [nuclear] force (S) and the weak [nuclear] force (W). Each force is manifested through the exchange of a particle called the carrier of that force, which completely determines the nature of the interaction (Panos 2000: 17). A short description of the four interactions in order of increasing strength: 1) Gravitational force (gravity): It is exerted on all particles and its magnitude is inversely proportional to the square of the distance (1/ r 2 ); this proportion is regarded as ‘infinite range’ by the physicists. The carrier of this interaction is graviton. There

6 are two mutually incompatible theories for the description of gravity: the General Relativity and Quantum Physics (or quantum mechanics). Their merging into a single Quantum Gravity theory has not yet been achieved. Moreover, neither the graviton nor the gravitational waves (a prediction of General Relativity) have been detected, although the scientists are certain for their existence in nature (Young 1994: 1305). 2) Weak force: Its range is of the order of magnitude of the proton radius (~0,001 fm). Carriers of this force is the electrically neutral Zo boson (mass 91.2 GeV/c2) and the charged bosons W (mass 80.4 GeV/c2). The weak force is exerted upon the quarks and leptons alike (Perkins, 2000). The weak interaction demonstrates itself in the phenomenon of radioactive beta-decay, when neutrons are converted into protons and electrons, while antineutrinos are also emitted. 3) Electromagnetic force: Its magnitude is inversely proportional to the square of the distance (1/ r 2 ), so it has an ‘infinite range’. Its carrier is the photon (γ), which has zero rest mass. The theory that describes the electromagnetic interaction is the Quantum ElectroDynamics (QED). It is exerted upon the electrically charged particles. 4) Strong force: It is exerted only upon hadrons and its range is of the order of magnitude of the atomic nucleus ( 1 fm). The carriers of the strong interaction are the 8 gluons and the theory that describes this force is known as Quantum ChromoDynamics (QCD) (Burcham and Jobes 1995: 234). The strong force do not discriminate between protons and neutrons, i.e. it is independent of the electric charge, and it can be attractive or repulsive depending on the distance between the nucleons (Panos, 2000: 30-31).

5.GRAND UNIFIED THEORY (GUT)

A further aim of Physics is to formulate a theory capable of fully describing the world by unifying the four fundamental forces. Actually, the unification trend in physics started one and a half century ago with considerable success. The Scottish theoretical physicist James Clerk Maxwell unified the mathematical equations that described the electric and magnetic phenomena (1861-1865), introducing the theory of the electromagnetic field, thus unifying electricity and magnetism with their respective forces. Moreover, through the ‘Maxwell equations’ the notion of electromagnetic waves was developed and light was understood as such a wave, thus uniting optics with the electromagnetism (Young 1994: 919-936). A few decades later, Albert Einstein also envisioned the unification of the natural forces. His views were expressed in 1950, in his article “On the Generalized Theory of Gravitation”, which was published in the Scientific American magazine – but he was not successful in this effort (Einstein 1950: 13-17).

7 A further significant contribution to the unification of the electromagnetic with the nuclear forces (the strong and weak interaction) was made by Julian Seymour Schwinger and Sheldon Lee Glashow. Schwinger won the Nobel Prize in Physics in 1965 for the QED theory, along with Richard Feynman. Schwinger understood that the weak and the electromagnetic forces were two manifestations of the same force, evident under high-energy conditions. Glashow on his side proposed as the carriers of the weak interaction two charged bosons, called by Schwinger W- and W+, and the neutral boson Ζο. When these bosons are in energies of the order of 100 GeV cannot be differentiated from photons (γ), a fact meaning that the unified electroweak interaction exists in these energies. In addition to Schwinger and Glashow, this issue was studied by Peter Ware Higgs, Jeffrey Goldstone and Steven Weinberg. Glashow, Goldstone and Higgs, formulated the mathematical background, which was used by Weinberg for the determination of the masses of W and Ζο bosons. Later on, in 1964, Abdus Salam developed a similar theory (Young 1994: 1306). The Nobel Prize in Physics of 1979, awarded to Glashow, Salam and Weinberg, sanctioned the existence of the W and Ζο bosons. In 1981 came the experimental discovery of these particles (Sundaresan, 2001: p. 58). a fact which led to the establishment of the so-called Standard Model; according to this theory, quarks and leptons interact through the exchange of the carriers of the strong and the electroweak interactions. Glashow, however, did not terminate his research. He attempted to unify the electroweak force with the strong nuclear force, based on the fact that in very high energies the electroweak force appears strengthened, while the strong nuclear force becomes less powerful. This would lead to the conclusion that in energies of the order of 1015 GeV all three forces are manifestations of one and only force. Glashow made the hypothesis that the quarks inside the nuclei obey to laws similar to the ones of Quantum Electrodynamics when strong forces apply (Chrysis 1996: 128). Howard M. Georgi created a suitable mathematical model of unification of the two nuclear forces

8 and in 1974 the two researchers published their work under the title “Unity of All Elementary Particle Forces”, a paper in which they formulated the “Grand Unified Theory” (GUT) (Sundaresan 2001: 51.). However, this theory requires the existence of extra undiscovered particles, which should be produced only in a very-high-energy environment.

In 2012 the Higgs boson was effectively discovered, a particle interacting with the elementary particles and gives them their inertial masses. Thus, the Standard Model was enriched with yet another boson behaving as a carrier of an interaction (ATLAS Collaboration 2012: 1-29). On March 14, 2013, the discovery was confirmed, as CERN announced that, based on new results, the particle that had been detected in July 2012 was indeed a Higgs boson (CERN Press Office 2013). The study of Particle Physics is intimately connected to the study of the creation and the evolution of the Universe. The Big Bang, the initial explosion that created the Universe, produced quarks, leptons and the quanta that carry the forces. Today’s Universe is expanding and cooling (Perkins, 2000) Therefore, the production of particles in high energies (which correspond to very high temperatures) approaches from the energy point of view the first moments of the history of the Universe, a period known as the ‘Planck era’, which lasted for 10-43 sec (the ‘Planck time’). Then the Quantum Gravity phenomena were eminent and the particles obeyed to forces described by a unified ‘Theory of Everything’ (ToE).

9 Although the simpler GUTs have been experimentally ruled out, the general idea linked with supersymmetry is considered by theoretical physicists as one of the most probable solutions. Other theories have also been proposed, mostly extensions to the Standard Model, which attempt to explain the structure of the natural world. These theories are to be tested by experiments, explaining their results; they also attempt to offer solutions to modern cosmological questions, such as the inflation and the dark matter and energy.

Kaluza-Klein theory and supersymmetry The first effort for a modern understanding of gravity was made in 1919, two years after the publication of the General Theory of Relativity, by the German mathematician and physicist Theodor Kaluza (1885-1954). The only forces known back then were the gravity and the electromagnetic force. Inspired by Einstein, Kaluza wanted to unify these two forces by proposing their ‘geometrization’. He suggested (and also proved theoretically) that the electromagnetic force could also be described as an effect of the curvature of space; yet, not of the 4-dimensional Einsteinian spacetime, but of a space with 5 dimensions, two spatial dimensions and one dimension of time (Kaluza 1921: 966-972). The question that arose naturally was whether there is indeed a fourth dimension of space, which is ‘hidden’. An answer came from the Swedish theorist Oskar B. Klein (1894-1977), who suggested that the fourth dimension appears to be absent because it has been ‘curled’ in such a small size that it cannot be sensed or detected (Klein, 1926: 895-906). What we perceive as a geometrical point in our three-dimensional space, in reality can be a circle within a fourth dimension of space. In spite of being a bright idea, the Kaluza-Klein theory was ignored for five decades. It was unearthed in the 1960s with the unification of the electromagnetic and the weak interaction, the attempt to unify the electroweak with the strong interaction (GUT) and the expectations for the unification of gravity with all the rest into a single Theory of Everything. However, if for the ‘geometrization’ of the electromagnetic force according to Kaluza and Klein one more spatial dimension was needed, the theorists of the 1960s proved that, in order to ‘geometrize’ the other forces, seven more dimensions are required, i.e. ten in total dimensions of space plus one for time. All these dimensions are supposedly curled around themselves If the Universe has eleven dimensions, of which 7 are ‘hidden’, then gravity can be described as unified with the other three forces into a ‘superforce’: Gravity results from the curvature of the four-dimensional spacetime (General Relativity), while the rest from the curvature of the space(s) of the seven hidden dimensions. In 1974 the Austrian theoretical physicist Julius Wess (1934-2007) along with his Italian colleague Bruno Zumino (b. 1923) conceived an even more ambitious program of unification: a model that would unify the particles with the forces (Wess and Zumino, 1974: 39). The underlying proposition was to look things quantum- mechanically and, without rejecting the 11 dimensions, to introduce the existence of fermions and bosons. The central idea was that, in order to unify fermions and bosons, a new symmetry should be used, one that would transform a fermion into a boson and vice-versa. This is supersymmetry (SUSY), which had been formulated almost simultaneously by J.L. Gervais and B. Sakita (in 1971), and Yu.A. Golfand with E.P. Likhtman (1971). Supersymmetry extends the Standard Model by incorporating additional kinds of symmetry. These symmetries exchange fermions with bosons. Such a symmetry

10 predicts the existence of supersymmetric particles (abbreviation: s-particles). The ‘superpartners’ of fermions are named by just adding the letter ‘s’, e.g. s-leptons and s-quarks, while the superpartners of bosons are named by adding the ending –ino, so there are the Higgsinos, the gluinos, the neutralinos and the charginos. Every particle of the Standard Model has a superpartner, whose spin differs by 1/2 from that of the usual particle. Because of the breaking of the supersymmetry, s-particles are much heavier than their usual corresponding particles. They are so ‘heavy’ that the existing particle accelerators are hardly capable of producing them (Aitchison 2007: 121).

String Theory The String Theory holds that the fundamental structural building blocks of the Universe are not point particles but rather one-dimensional strings, about 10-34 m long (Gubser 2010: 54) (Planck length). This way the String Theory avoids the problems and singularities resulting in theories of physics due to the point nature of the elementary particles. What we perceive as particles are discrete oscillation modes of these strings, which can be either open or closed (loops). String Theory started as an effort to describe the interactions between hadronic bosons. Since then it has evolved into something much more ambitious: the construction of a complete and unified theory of all the fundamental particles and forces. All previous attempts to unify the four forces faced problems in the incorporation of gravity. The String Theory not only includes gravity, it actually requires it. In low energies it formulates a theory of Quantum Gravity (a union of Quantum Mechanic field theory with General Relativity), which can equally well describe the electromagnetic and the other fundamental interactions. String Theory requires six or seven dimensions of space and provides ways to correlate the large extra dimensions with the curled ones. The elaboration on String Theory led to the concept of supersymmetry, which doubles the number of the elementary particles with the introduction of sparticles.

Interaction in the subatomic world: the cosmic lines of the point particles in the Standard Model and the cosmic sheets created from closed strings in string theory.

There are two main branches of String Theory versions: the Bosonic String Theory in 26 dimensions(Gubser 2010: 60-62) and the Supersymmetric String Theories in 10 dimensions (Gubser 2010: 62). Today the term ‘String Theory’ is applied usually to the second one, also known simply as Superstring Theories or just Superstrings. An important discovery in the 1990s was that the various Superstring Theories can be derived as limiting cases from one relatively unknown eleven-dimension theory, the Membrane Theory or M-theory.

11 The Μ-theory Before 1995 there were five known Superstring Theories (Type I String Theory, Type IIA String Theory, Type IIB String Theory, Heterotic SO(32) theory and Heterotic E8 × E8 theory (Robinson 2011: 302) ). All five were essentially based on oscillating, one-dimensional strings, with length of the order of the Planck length; however, when these theories are analyzed in detail, serious differences appear among them. The M-theory, whose mathematical description was presented for the first time in a conference held in 1995, is believed by many specialists to be capable of producing a Theory of Everything. It is supported by noted physicists, such as Brian Greene and Stephen Hawking. M-theory is a generalization of the 5 existing superstring theories. A significant part of our knowledge about M-theory originates from the low-energy limit, which is described from the 11-dimensional supergravity. M-theory provides a unifying frame, inside which superstring theories can be understood as different asymptotic limits of a unique parameter space (Witten, 1995:85). M-theory for some of its proponents leads naturally to 10500 ‘Universes’, each with its own natural laws.

From the theory of Empedocles to the Theory of Everything As it is evident from the previous discussion, the leading effort of modern scientific research in physics aims at the unification of the fundamental forces of nature. Therefore, it is important to note that the Greek pre-Socratic philosophers had intuitively suspected the underlying unity that exists in nature, despite the complexity of the natural phenomena. The common points of the modern theories with the theory of Empedocles can be summarized as follows: a) Both theories speak about a prior state of the Universe, at which its fundamental forces were unified. According to Modern Physics, there is one force, which in our evolved Universe appears in four manifestations, whose effects can be perceived by our senses. In analogy, Empedocles wrote about a state of perfectness that was once the state of our Universe (Sphaerus), which could not be grasped by the human senses. Sphaerus was disrupted or differentiated into the four ‘elements’ (Fire, Air, Water and Earth) that are the fundamental building blocks of the modern, ‘sensed’ Universe. The basic similarity in the essence of the two theories is that they suggest that everything started from a unity and proceed towards multiplicity; the Universe itself seems to evolve in the same direction. A grand vision for modern science is to unify the basic forces of nature; the difference is that now the experimental verification is the most important part, a fact that leads to the construction of expensive particle accelerators. b) The cause that leads to the breaking of the symmetry, the inflationary expansion of the Universe and the differentiation of the forces is a topic of research. Empedocles called this cause ‘Strife’, the factor that caused the disruption of Sphaerus. Consequently, the Strife causes the ‘appearance’ of the four ‘elements’. Therefore, in both the ancient and the modern theory there is a cause that disrupts the primal homogeneous state. c) Empedocles assigned to Sphearus properties that underline its symmetry, which prevailed during the Planck era, when the four interactions or forces were united and symmetric.

Conclusions Through centuries of intellectual history, the human mind continues to strive for the understanding of the natural world. Cosmology is a branch that still keeps researchers

12 busy and probably will do so even more in the future. However, the main path and tendencies of human thought has remained the same. Empedocles unified his four elements in the frame of the Sphaerus state. This state pre-existed the four Empedoclean elements and it was responsible for the creation of everything. The modern researchers in the experimental field of particle physics attempt essentially to re-create that primal state. They design detectors of elementary particles inside which interactions can be observed in a momentary high-energy-state environment. The four fundamental forces or interactions in nature were united at the moment of the creation of the Universe and, because of the existence of certain perturbation, their disruption was activated and the world as we know it was created. Thus, both the philosophy of Empedocles and the modern scientific research point to the exploration and understanding of the deeper unity that exists in the natural world and cannot be perceived by the human senses, only by the human intellect.

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