Chapter 1, The Universe
Innumerable suns exist, innumerable earths revolve around these suns in a manner similar to the way the seven planets revolve around our sun. These worlds are inhabited by living beings.
From On the Infinite Universe and Worlds, Giordano Bruno, 1584.
The universe is full of mysterious things patiently waiting that our spirit becomes eager.
Optimistic words by an anonymous philosopher.
1. Astronomy, Cosmology and Astrophysics
It is about certain that astronomy is the eldest of all sciences. Since 3,000 years B.C., the Chinese, Assyrians, Babylonians and Egyptians already observed the sky having in mind practical objectives, for instance, time measurement, to determine the best time to plant and to crop the grains or even with the objective to foresee the future and determine the astronomical objects influences over the human beings (astrology). One of the most ancient discoveries was the determination, relatively precise, of the duration of the year (including in the Aztec culture), the moon phases and of the four seasons of the year. It is not our purpose to present an historical report of the human culture, but it is valid to remember that the apex of this science in the ancient cultures developed in the ancient Greece (600–400 B. C.), only surpassed in the 16th century.
Presently, astronomy is a technologically very sophisticated science having as object the study of the constitution, relative position, mapping and movement of all astronomical objects existing in the whole universe. This sophistication consists of two large branches: cosmology and astronomy, both on the frontiers of the universe knowledge, operating in an interface not always so clear. (1, 2)
Cosmology has as object the study of the structure and origin of the universe, and beyond that, the discovery of the laws that rules it in a broader sense. The cosmologists developed and follow developing the most different theories and laws in an effort to reveal the enigma of the universe, basing on the resources of modern physics. (3)
Astrophysics, by its turn, is the branch of astronomy that takes care of the physical and chemical constitution of the astronomical objects scattered throughout the space and that, as a whole, fills up the universe. It makes use of radio telescopes, the Hubble’s telescope, the Chandra’s telescope (X rays), spectrophotogrametry, spectral deviations, etc. (4)
On the other hand, modern physics is involved in searching for answers to the big questions about the structure of existing matter and particles (matter and energy) which exist inside the atomic nucleus (strong nuclear force and radioactive decay). Also, physics studies the several forms of energy acting outside the nucleus (weak nuclear force and magnetism), as well as, the gravity force and the laws that rule it among themselves and as whole. Since the 1950´s, physicists are theorizing on the unification of these forces with the objective of defining a possible Theory of Everything, thus making peace between The Quantum Theory that takes care of the microcosm and The General Theory of Relativity, which rules the macrocosm.
2. Theories about the Formation of the Universe
Along the times, since the most remote eras, man not only contemplated the sky a numberless of times, but also, he should have questioned about the form and extension of space and the astronomical objects existing on it, or say, about the cosmos.
They were the Greeks, from whom we have inherited so much culture, be it in the literature, arts and philosophy or in the field of the natural sciences, who transmitted to us the first ideas about the universe. About the year 600 B.C., Anaximandro admitted that the Cosmos had been emerged from water. Very strange idea, but it was not contested during 200 years!
Still in Greece, around the year 400 B.C., Eudoxo from Cnido, using a Pythagoras´ idea, created the Geocentric Model, placing the Earth in the center of the universe. By the year 200 B. C., Ptolemy and Aristotle adopted and propagated this model, which prevailed during 2000 years.
Only in the 16th century appeared the first movements having in view to alter this model. Nicola Copernicus (1473–1543) was the first scientist to suggest that the Sun was the center of the universe and not the Earth, theory which received the name of heliocentric model. Giordano Bruno (1548–1600) added that the universe had no limits, was infinite and, due to contradict the Catholic Church teachings, he was judged and burned by the Inquisition. Galileo Galilee (1564–1642) sponsored this theory and was forced to deny it, under confession, so as to not have the same death as Giordano Bruno.
In the 20th century, it appeared The Finite Model Theory of the universe in constant expansion, proposed by George Lemaître and Alexander Friedman. In 1950, Fred Hoyle laughed at their faces, naming it the Big Bang Theory, model according to which the universe was created from a gigantic explosion of one point, name which came to be adopted by this theory, which also establishes the existence of four dimensions in the universe. Presently, this is the most accepted theory.
In 1960, it appeared the Multiverse Theory, which establishes the existence of more than one universe in the infinite space, since that the Big Bang Theory did not answered two questions, namely, first: what existed before it; and second, what exists beyond the universe space.
In the beginning of the 21st century (2001), it was proposed by Paul J. Steinhardt the Cyclic Theory, which embraces the idea that the universe has emerged from the impact between two cosmic membranes, – the branes, originated from a fourth dimension of space and that this shock had been recognized as the Big Bang. If the Relativity Theory and The Quantum Theory were correct, say a group of physicists, this is a theory which makes sense.
3. A little Bit more About the Big Bang Theory
Presently, as it was told before, this is the most accepted theory about the origin of the universe, proposed by the Russian scientist, naturalized American, George Gamow, in 1948. He theorized that the universe originated between the past 13 to 20 billions of years and came from a unique point (point zero – not dimension zero). At this initial moment, the size of the universe would be near-zero. In it, it was contained all the matter in a so concentrated way that its temperature would be almost infinite. According to this theory, this point would be the beginning of time, and from it, it began the formation and expansion of the galaxies. Physicists present a speculative and detailed description of the events, since the instant zero, or say, from the exact moment of the explosion or Big Bang, but we shall not go worrying about it here. One of the evidences of certainty of this theory is that galaxies are moving apart one from each other, as it is common with the remains of an explosion, as verified by astrophysicists. It is still lacking two great questions to be answered by the scientific community: what is the reason why our universe was structured like it is, and why was it created.
According to this theory, the universe, since its formation, is expanding and getting colder. Physicists and cosmologists admit that, in the first thousandth of one second of creation, it had been formed only a mixture of subatomic particles composed of quarks and electrons, which are the most fundamental forms of matter (particles) known by science.
In this first step of formation, with the resultant cooling due to expansion, the quarks that were initially moving at a velocity near that of light, slowed down in function of the reduction of the temperature and, due to that, gradually disappeared as free particles. This is the moment when they associate themselves to form protons and neutrons, which took place within the first ten minutes of the birth of the universe, there forming the simplest nuclei in the form of hydrogen, consisted of only one proton. At the same time, nuclei of Helium were formed, the second element in the atomic scale, consisted of one proton and one neutron. At this point, all the matter that existed in the universe was in the form of plasma, composed of these two types of nuclei, still without their electrons, in the proportion of 75% Hydrogen and 25% Helium. Even today, these are the two main more abundant chemical elements in the universe, representing more than 90% of all known matter.
The third step of this fantastic history started at about 300 thousands years after the beginning of the great explosion, when the electrons came to attach to the atomic nuclei of the elements in order to form the first complete atoms. Due to the strong gravity force prevailing at that moment, light could not escape from the mass in expansion, until a critical point was reached and the light was born. Up to then, it was part of the mass in expansion in the same rhythm that this was occurring together with the matter, and all was dark.
Thenceforth, the universe becomes transparent and luminous and the photons, which are particles of light, get free and start interacting in a lesser degree with the atoms. These photons leave signs or “fossils”, actually captured by our best telescopes, inclusive the Hubble, of which we will talk later on. After almost one billion years past since the Big Bang, the atoms aggregate and start forming the first stars and galaxies.
4. The Space and Its Content
To have an idea of the greatness of the universe, we present here a short description of the principal astronomical objects, without extending on the subject, because this is not the main object of this book.
A galaxy is formed by a vast amount of stars, nebulae and interstellar matter. Galaxies are of three types or forms: elliptical, spiral and irregular. By their turn, the galaxies are grouped as clusters. Our galaxy, the Milk Way, has the spiral form and it is said to belong to the Local Cluster, one of the smaller clusters, which contains about 40 galaxies. Despite of belonging to a small cluster, it possesses the form of a disc with a diameter of 130,000 light years and a maximum thickness in its center of about 12,000 light years. One of the largest clusters, the Virgo Cluster, possesses 2,500 galaxies. Clusters of medium size contain about 100 to 500 galaxies. Inside our cluster of galaxies, the Milk Way is the largest, which is of elliptical type. (6)
Our Sun, with its solar system, is situated in one of the spiral arms of our galaxy, at two thirds of the center. To turn one time around the nucleus of the galaxy, the Sun takes 225 millions of light years! (6)
To estimate the number of galaxies, scientists pointed the Hubble telescope in direction of a very small celestial point of the size of a grain of sand as if it was observed at the distance of one meter. The light that came from the stars in that point was so weak that it was necessary ten consecutive days of exposition to obtain a good image. Then, the examination of only that point revealed the existence of 620 galaxies, having different distances, sizes and forms. Based on this and many other information and studies, researchers extrapolated the results and arrived at an incredible estimate that in the whole universe there are about 125 billions of galaxies! This cipher is 50% greater than one previous estimate. Each one of these galaxies possesses between 100 millions and 1 billion stars, similar to our Sun. Some of these stars are located at more than 12 billions of light years, or say, about one billion of years after the formation of the universe. (5)
One star may be defined as an astronomical object, generally in the form of a sphere, in the interior of which the temperature and pressure are very high, mainly in its center. In the stars occur thermonuclear reactions with the liberation of considerable amount of energy, which propagates from the center to the surface. From this, the energy is transmitted through the interstellar space in the form of electromagnetic radiations, from which the heat and light are modalities.
Stars are assembled in groups or clusters of the open or globular type. Only in our galaxy there are about 100,000 open groups, from which only about 1,100 are known. Globular clusters are about 10,000 to 1,000,000. (6, 7) As a whole, it is estimated that, only in the Milk Way, there are about 400 billions of stars! (7)
How a star is born? (8) By the action of the gravitational force occurs the agglomeration of the material contained in a nebula, mainly represented by clouds of Hydrogen, Helium and dusts. This process, which takes the gases to contract themselves, also increases the temperature of the agglomerated material, up to a point in which a thermonuclear fusion starts and, since that there is enough gas, a star will be formed. In the case there is not sufficient gas (less than 50 times the size of the planet Jupiter), it is then formed a brown dwarf star. (8)
And how does a star die? The result from the star “death” depends on its mass. (8) If its mass is less than eight times the mass of our Sun, when its nuclear fuel (Hydrogen) is exhausted, a white dwarf star is born, around which may exist or not a planetary nebula, passing before through a phase known as red giant, in which the gases expansion increases considerably the diameter of the star. That is what can happen with our Sun that has already 4.5 billions of years of existence and, from now to more 4 billions of years, its diameter will be arriving near the orbit of the planet Mars! If the mass of the star is more than 8 times heavier than our Sun the process of the nuclear fuel exhaustion may become catastrophic. This happens because, at a certain moment of its existence, it begins the formation of iron and other heavier elements that cool into solid form, taking the star to collapses. The remains impact into the core and are thrown through the space, as well as the gases, to form a new nebula. One of the following situations may occur with the remaining core: if its mass is 2 to 3 times greater than the mass of the Sun, a black hole is formed; if it is less, a neutron star is formed. An uncontrolled explosion of a massive star (mass above 8 times the solar mass) can give place to a supernova, which reflects an intense brightness that may last for months. The last detected supernova was the SN1987 belonging to the Large Magellan Cloud, by the observatory Las Campanas – Chile, on February 24, 1987. Its charge of neutrinos reached the Earth two hours later after being seen. (11)
White Dwarf Stars
When the mass of a dying star turns to less than 2 or 3 solar masses, it becomes a white dwarf. (7) To have an idea, the Sun has a diameter of 1,400,000 km and it may transform, after 3 to 4 billion of years, into a white dwarf of about 10,000 km diameter, or say, approximately the size of the Earth, but with a massive density.
Black holes are black astronomical massive objects with high density and, therefore, with a very great gravitational field, with conditions to sucking all and any matter that comes near the event horizon (near to its edge) and surpass the limit of singularity, not even escaping the light. Black holes are formed from the death of a star with mass eight times or greater above the mass of the Sun and when all the nuclear fuel has been exhausted and of it liberated, only letting its solid core containing iron and heavier elements. Black holes were detected by the Hubble and Chandra telescopes, both operating in satellites in space, which capture its emissions of X-rays. Black holes have a very strong gravitational field; they rotate at very high speed and follow the process of the universe expansion. One example of black hole is the stellar object Cygnus XR-1. (7)
Neutron stars are strongly massive astronomical bodies. We know that stars evolve themselves during millions and millions of years. With the stars that have their initial mass ten times above the mass of the Sun, something of special happens. After they explode as supernova, the core remains extremely massive creating conditions to compress the electrons against the protons, forming neutrons. The result will be a neutron star, in which it could compress the mass of one and half Sun in an area of 20 km diameter. (9)
They are stars that failed in their formation. For that reason, the brown dwarves do not match the idea of a perfect universe. In general, they are considered stars that went wrong, because they had not sufficient mass to start the process of nuclear fusion in their cores. Therefore, they do not emit either their own heat or light: they are cold and dark. Some of them remain isolated; others are part of a binary system in which a brown star rotates around a larger star. Eccentric and rare, they still need to be better studied and explained.
Quasars are sources of strong electromagnetic emission (radio waves) looking like the stars, bluish in their colors. Their names come from the initials of Quasi Radio Sources. The first quasar was discovered in 1961. They are also known as black holes existing in the center of some galaxies, and despite of being very compact (very high density) and very bright, some of them show brightness up to one trillion times more intense than the Sun. Quasars masses go from 1 billion to 1 trillion of times the mass of the Sun. They follow the expansion process of the universe in a speed that reaches to one tenth of the speed of the light. (7)
Pulsars are neutron stars with radio-pulse (9). It is estimated that there are about 1 billion pulsars only in the Milk Way, from which about 1,000 are already known. The first pulsar was discovered by Anthony Wewish, in 1967 (Nobel Prize, in 1974). When the mass of a dying star reaches values lesser than 3.2 solar mass, it will transform itself in a neutron star. (7) A pulsar has a period of pulsation of 1.337 seconds with a rotational period of 4.4 seconds when very long and of 0.0016 seconds when very short, for example, one of them turning around with a velocity of 625 turns/second! (7, 10)
Our Solar System
The Sun is our star, being responsible for the temperature, evaporation and heating, besides the several biological processes that takes place with the plants and animals of all species on the Earth.
The solar system is formed by nine planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto – besides the sixty-one satellites which turn around the planets and a great number of small objects known as asteroids and comets. A tenth planet, with the name of Sedna and located far from Pluto, was discovered in 2005, being in the process of verification or confirmation. From these planets, Jupiter, Saturn, Uranus and Neptune are gaseous. The orbits of all these planets are elliptical, being that the comets have extremely eccentric orbits. After the year 2007, Pluto was disregarded as planet and it was introduced, in its place, the planet Sedna.
Scientific studies indicate that the Sun should have been formed at approximately 4.5 billion of years. Its mass is about three hundred thousand times heavier than that of the Earth, and its diameter is approximately 1,400,000 kilometers. The distance between the Earth and the Sun is about 150 millions kilometers. The average temperature in the core of the Sun reaches 15 millions degrees Celsius. In this star, in its inner part, it occurs nuclear reactions as, for instance, the fusion of the Hydrogen atoms. In the photosphere or surface, the Sun gives off light, and heat, and other energy forms, as the cosmic rays. The Sun is still composed of a layer of gas that involves the star.
At each cycle of eleven years, the Sun goes by a period of extreme agitation, sending to the Earth solar storms. Thus, the so-called “solar wind”, electrically charged (ionized particles) when arrives at the Earth starts to interfere in the electronic systems, networks of energy, computers, electronic apparatus, communication systems among airplanes, ships and satellites. These same waves of energy and electricity come to create the so-called Aurora Borealis and Aurora Australis, phenomena in which the air shines in the areas close to the magnetic poles of the Earth, generating a marvelous show of lights and colors in the sky.
Under the chemical point of view, the Sun is formed by the following elements: 73% of Hydrogen, 25% of Helium and 2% of other elements.