origen_universo_Txt_El origen del universo
The origin of the universe
Carlos Pérez and Héctor L. Mancini.
department of Physics, University of Navarra.
Slides from January 2003, text from January 2006.
The following paper is devoted to commenting on the slides presented by Prof. Carlos Pérez García in his two lectures at the seminar room "Science, Reason and Faith", which took place in the spring of 2005.
Carlos Pérez left this work unfinished, without text, due to the tragic accident he suffered on 31 July 2005 during an excursion to the mountains. Although I was not fortunate enough to attend attend to that course, the universal characteristics of contemporary science allow any other person, such as the writer of these texts, to imagine and fill in what this sequence of images is trying to narrate.
I have made no changes to the order of the photographs, trying to respect the line of argument that can be deduced from them. In only one case have I cited a slide in a different order, in order to achieve continuity and clarity in the text; the differences this introduces are didactic and do not affect the specific content, which I hope I have respected. Any differences, errors or omissions with respect to the content of the lectures are, of course, my sole responsibility and I apologise in advance for them.
As I see it, there are three slides where the line of argument is set. The first one presents the topic of the conference under the single title of "The origin of the universe", although later in his development he will have two clearly differentiated approaches, one purely scientific and the other from the perspective of faith. Then slide number 22 is empty and Carlos calls it "transitional". Finally, the last slide closes the lecture with the phrase "The end of the universe". Again without clarifying whether it is according to faith or according to science, which also suggests a common end for both conceptions, which, however, the transition slide tries to clearly separate.
It is not unusual for a scientist, a Catholic physicist, to have this way of thinking. As a scientist, the coherent search for truth prevents him from taking any shortcut that deviates from the path provided by the fundamentals and methodology of science. But as a Catholic, he knows very well by faith that behind that empirical truth God will always be present and that we will never achieve in this life the fullness of Truth. This duality generates a permanent tension of overcoming and searching and makes us see scientific thought as something incomplete and in continuous elaboration. Each reality scrutinised always refers us to higher planes of thought with the conviction that God is behind it, and that it is our obligation to analyse in what form it presents itself to us.
I think it is for this reason that Carlos has not mixed the speeches and has separated them with a neutral, content-free slide. In this way he separates two speeches, maintaining great respect and coherence in each of them, but simultaneously preserving their full identity. Many times mankind has tried to mix things up or to eliminate one of the approaches and usually, the result has never been too good.
Eight centuries ago St. Thomas Aquinas told us on the one hand, that there is nothing in our mind that has not first passed through the senses, which seems a complete adherence to the first speech, but he simultaneously maintains a dual speech , a double source on the level of knowledge when dealing with revelation. This position was confirmed on numerous occasions and remains alive in the Church to this day. As a Catholic, I also share this perspective and therefore do not like to mix it up either.
Before concluding, Carlos presents a famous old photograph taken in 1933, in which three famous scientists appear together: Robert Millikan, George Lemaître (creator of the Big-Bang model ) and Albert Einstein. As the latter is a priest, his presence next to Einstein has been considered significant and is sometimes presented as an example of the dialogue between science and faith. We should point out that this is only partially true.
To begin with, although one was a priest and both believed in God, in their relationship they both acted as scientists. According to some witnesses, it is known that they respected each other deeply and understood each other very well. However, without abandoning either the scientific perspective, they did not manage to understand each other until Degree to share their theories about the physical universe, despite cultivating the same scientific discipline.
This is why we believe that the so-called dialogue between science and faith should not be subjected to simplifications that undermine it. It is a highly complex task in which arguments should not be used without hard evidence, presented at the highest possible level. In the absence of experimental evidence, a dialogue of goodwill, while remaining within a purely scientific perspective, only allows for the respectful presentation of each point of view. Let us remember that behind many of the greatest scientific breakthroughs there were religious people such as Copernicus, Newton, Lemaître and Galileo himself, who did not mix their faith with their achievements as scientists. There were and are also scientists of other religions and atheists, and each one presents scientific truth from his or her own perspective.
It should come as no surprise, then, that in the so-called "dialogue between science and faith", there may be different and discordant opinions. Many opinions are just that, opinions, which, to make matters worse in today's society, are often vulgarised in the mass media. Most of the most notorious disagreements do not go beyond the level of sterile discussions between people who cannot confront evidence and who like to give their opinions on any area of science, faith or both. When there is an experimental demonstration, there is no more dissonance.
With this idea as directive, I hope I have not misrepresented the thought and memory of our dear friend Carlos Pérez García.
Hector L. Mancini
The rigorously scientific consideration of the origin of the universe is a relatively new problem. However, its incorporation into human thought can be regarded as very old. Although our knowledge of oral and written human history is less than 5,000 years old, it is clear from various archaeological evidence that man has been concerned with the world in which he lives, and has formed ideas about the universe as a whole, since much earlier. We can affirm that the traces are lost in time.
When man became a farmer, he needed to scrutinise the heavens in order to better regulate the sowing and harvesting periods and thus achieve greater efficiency in his new mode of survival. Observation of nature, and especially of the cyclical behaviour in the movements of the heavens, then became an important task. This occupation allowed him to collect over a couple of millennia a set of observations, which accumulated in parallel with the different theories he developed to explain them.
These theoretical descriptions can in no case be considered scientific, not even those that contain descriptive hits. They are not scientific because they lack several of the elements that today we consider basic to form such a speech. In any case, they provided man with an overview of what he observed and in some clearly recurring phenomena, they even allowed him to predict future consequences, a basic goal of today's science. It is not the case here to develop a detailed history of those initial steps. The first interpretations that analysed the observed regularities by considering the (homocentric) "celestial spheres" intended to locate the "fixed" stars, and the inclusion of epicycles and deferents to explain planetary motions, were an important advance in the construction of a primitive "science of the totality" or "cosmology". These early cosmologies developed and progressed into true schools of thought that are remembered today alongside the names of Hipparchus, Apollonius, Aristotle or Claudius Ptolemy.
The first relatively complete model used to predict celestial motions is the geocentric model which is remembered in association with the name of Claudius Ptolemy I, who compiled much data from previous centuries. This model presents the ancient conception of a universe with the Earth at its centre and the planets describing complicated orbits against a background of supposedly fixed stars. The most important problem he solved was the description of planetary motion, including the Moon. The word Planet, meaning "wanderer", gives us an idea of the Degree abstraction needed and the difficulty of the problem when observed from the Earth.
Despite this difficulty, the problem was solved and with these theories it was possible to understand and predict some phenomena such as eclipses, hitherto considered mysterious events by the uninitiated. Narrowing their scope to the then known planets, the theories explained or at least described quite correctly the motions of the stars. That of motion is the first problem to be solved, and can be considered as the foundation for a physical description of the universe. For almost two millennia, mankind maintained the idea of independence of causes for the motion of the stars and the motion here on Earth, an idea which, for example, can be found in Aristotle and other Ancient Greek thinkers.
Against this background, all theories of celestial motion invariably supported the conception of a globally static, stable and therefore immutable and eternal universe.
The theoretical reason for placing the "absolute" reference system for the study of motion at the centre of the Earth is the existence of the force of "gravity". The lack of explanation for the origin of this force using only "common sense", will maintain for 18 centuries the geocentric model as the most logical solution. The heliocentric model , which had also been proposed in ancient times, lacked an experimental database to motivate its preferential use and in this system, the Earth must be considered in motion. This preferred location for the "centre of the universe" had to wait for its general endorsement until the appearance of Nicolaus Copernicus' book in 1543, the extraordinary astronomical observations of Tycho Brahe (1546-1601) and its use by Johannes Kepler. Until then, the heliocentric model had no obvious advantages and instead had serious disadvantages.
In spite of the progress it meant in the calculation of orbits and fundamentally in the global understanding of planetary motion, the heliocentric model took many years to be accepted (probably because of the problems associated with the explanation of the existence of the force of gravity). But a few years later, with the first steps of the new experimental science, the heliocentric model was imposed by its own coherence among scientists. As is well known, this model had in Galileo Galilei one of its most active defenders. He famously recanted: "E pur si muove...". That is: ...nevertheless it (the Earth) moves... (the Earth).
The heliocentric model had rational support and adequate experimental observations, but it was not until the work of Isaac Newton (1642-1727) that these models could be considered a "scientific theory". It was Isaac Newton who unified celestial mechanics and mechanics on Earth by means of a common explanation. That is, something that is already a physical theory. In his work, for the first time, the old idea of the duality of causes is abandoned and astronomical observations are related to those of the earth's motion.
Newton first of all justifies why, near the surface of the Earth, all bodies fall with the same acceleration; knowledge which marks a fundamental milestone in the birth of modern science. This conclusion, derived from his audacity in postulating the equality between inertial mass and gravitational mass, allows him to anticipate a prediction that H. Cavendish would prove in 1798, almost 100 years later, when he measured the universal gravitational constant.
This now systematised knowledge signifies a scientific leap, which, qualitatively considered, is the most important change in theoretical thought in more than 20 centuries. And as is usually the case with such changes, these ideas are seminal and will immediately give rise to much more profound reflections on the concepts of space and time than those carried out until then. From this declaration of principles, Newton's laws of motion and a rational explanation for the force of gravity, the foundations of modern science will be laid instructions . Together with Galileo, Newton would demonstrate a new method for scientific reflection that would prevail in the future: first of all, the expression of any physical theory or isolated knowledge would be in mathematical language, a language that he himself helped to create. And then, that theory will have in experiment or quantitative observation the criterion for verifying its validity. In turn, each new experiment, in order to bear fruit, will have to be inserted into the general framework of the theory and find its justification there.
To present his new dynamics, Newton has introduced the old idea of space conceived by Euclid: an empty, isotropic and homogeneous place, in which the subject resides (or is aggregated). This idea replaces that of a space with a privileged place to locate a reference system, be it the centre of the Earth, the Sun or any other point in the universe. For Newton, space and time remain uncoupled and the universe remains infinite and unchanging, i.e. eternal. This universe has no need for an origin in space or time, although it could have one. A hypothetical traveller travelling in a given direction would constantly encounter new regions with new stars and galaxies. This idea, although it contains some paradoxes (e.g. the "Olbers' paradox"), seems very suitable to unify scientific theories in a few axioms.
But this conception of space would not last as long as the one used in the previous stage. New elements of judgement would modify these ideas.
In 1905, Albert Einstein (1879-1955) presented his theory of Special (or special) Relativity, the seed of which had already been maturing in physics, mainly with the work of Georges FitzGerald (1851-1901) and Heindrik Lorentz (1853-1928) and the analyses of the negative result of the Michelson-Morley experiment. These two scientists arrived independently and in the above-mentioned order at the conclusions about the contraction of space, the constancy of the speed of light in a vacuum and the dilation of time. Lorentz, in addition, obtained a law on the increase of mass with velocity. These effects are very noticeable at velocities close to the speed of light, and will later receive their explanation integrated in the framework of the theory of special relativity. However, both were left at the doorstep of the theory of relativity.
It is Albert Einstein who introduces in this theory the extremely novel ideas about space and time: a space that contracts and a time that expands when the velocity increases. In essence, the theory refers to the comparison between measurements made in different so-called inertial systems, which move in uniform rectilinear motion relative to each other. Until then, the conclusions derived from Galileo's and Newton's relativity were considered valid. They do not distinguish between a system at rest and a system moving with uniform velocity. If there is no external force, the system in both cases will remain indefinitely in the state it is in.
Einstein sample, however, that observing from a moving reference frame produces novel effects. In particular, when considering the propagation of electromagnetic waves such as light, radio waves or X-rays counter-intuitively, different observers will measure the same speed of propagation, even if they are in motion.
As anticipated, it was the great synthesis of electromagnetism developed by J. C. Maxwell (1831-1877) and carried by FitzGerald and Lorentz that introduced the new questions of space and time. That theory had unified electricity, magnetism and optics, creating the concept of electromagnetic waves: travelling electromagnetic fields. With all the above conclusions, Einstein postulated that the constancy of the speed of light holds even for emitters and observers in uniform relative motion. Working with this hypothesis, Einstein began the studies that led him to propose a complete transformation in the conception of space and time. At low velocities these effects are not important and the laws of classical physics remain valid, having been absorbed as a particular case within a more general theory.
Einstein's theory also posits the equivalence between mass and energy. In his most famous equation: E = mc2, the mass m and the energy E, are two sides of the same reality and can be passed from one form to the other simply by multiplying by a constant, the speed of light in a vacuum c squared.
A few years later, in 1916, Einstein himself completes his description by including accelerated reference systems, or "non-inertial" systems. This new theoretical advance is known as the "Theory of General Relativity" and is in fact a theory of gravitation. It is a much more complex theory, and unlike the previous, more limited theory, it has few situations in which it can be tested.
Based on it, it is no longer possible to conceive of a universe like Newton's, situated in an infinite space. The acceleration of gravity is just another acceleration, and the problems produced by its consideration in a Euclidean, isotropic and homogeneous space are now transferred to the properties of space. The presence of subject, whose property called mass is the cause of gravitational attraction, in this new conception has a new role: it "curves space". It is a curved space that causes the attraction of other nearby and distant masses (this curvature can be imagined as the curvature of a heavy person standing on an elastic mattress that is deformed by this presence and attracts other people or bodies nearby).
It took mankind almost 2000 years before Newton, in order to describe motion, could incorporate Euclid's idea of an isotropic and homogeneous space. In less than two hundred years, this idea was reduced to a limiting case of a more general space (Riemannian and Lobachevsky geometries). Again, the previous theory is absorbed as a limiting case. For example, the sum of the interior angles of a triangle in Euclid's geometry is always 180°. In a curved space this is no longer the case. This sum will be greater, but always, when the curvature is very small, the space can be considered flat and classical geometry regains its validity. This absorption of the previous theories into the new one is a constant in modern science. The previous theories are considered as valid readings of the real world, in turn, the new ones could be absorbed in the future, within another more general theory. But in all cases, the earlier ones retain their validity within their approximation.
It is hard for us to imagine a curved space. Although we are inside it and contribute to its curvature, it is not obvious to us at our scale and therefore escapes our "common sense". Considering space as this theory does, it is not possible to distinguish by experiment an acceleration from the curvature of space or "gravity". A homogeneous gravitational field is completely equivalent to an accelerated reference system. This is the so-called "Equivalence Principle" and in this space, the laws of physics are the same under gravitational attraction as under acceleration.
This idea has always been difficult for philosophers and even more so for ordinary people to grasp. That is why the theory of relativity is so often referred to and commented on, yet so little understood. But with it, Einstein explains first of all a phenomenon of very small amplitude and known since ancient times: the excess of the precession movement of the perihelion of Mercury, the closest planet to the sun, over the classical theory. The topic sounds strange, but astronomers knew its value perfectly well (Leverrier in 1840 explained it by imagining the existence of a planet closer to the sun, which of course was never observed). The value of this effect is approximately one Degree every 10,000 years, i.e. 0.01° every century. A great success for a new theory, which should build on Newton's enormous prestige.
The theory predicted other phenomena that were soon verified. For example, the value of the deflection of a beam of light passing close to a high-mass star, a measurement made by W. S. Adams at the suggestion of Arthur Eddington in 1919. This verification was widely publicised and brought Einstein enormous fame and resounding success. Another prediction of the theory is the dependence of the frequency of the periodic motions of an atomic clock on gravity. Today, all GPS systems are corrected for this effect.
After these predictions were verified, the confidence in the accuracy of the general theory of relativity was so great that it had to be included in any cosmological model , since gravitation is an essential component. Einstein himself, in 1916, proposed a universe model in which he included an isotropic and homogeneous mass distribution (considered on a large scale), a hypothesis he called the "Cosmological Principle".
In positing his model, since gravitational attraction always has the same sign (attraction), Einstein realises that at some point the universe will collapse due to gravity. That effect had to be balanced somehow in the equations to avoid it. Like all great scientists up to that time, Einstein believed in the existence of a stationary universe and to achieve this he included in his equations an appropriate term to produce the opposite effect, i.e. a repulsive term. He called this term the "cosmological constant" and adjusted its value exactly to obtain a stable universe. When after some years the expansion of the universe was astronomically proven, Einstein himself considered that introducing the cosmological constant had been "the biggest mistake of his life". But as will be seen below, it is no longer considered a mistake today.
With general relativity, instructions was firmly established on which new cosmological models should be built. Einstein, like all great scientists before him, continued to believe in a static and unchanging universe.
Soon, dynamical models of the universe began to appear, mainly by mathematicians. Willem de Sitter, who was apparently the first to take a serious interest in the theory of relativity and made it widely known in England, was not at agreement with Einstein's conception of the universe. For Einstein, the universe is static and in the new geometry introduced, its curvature should be constant. De Sitter in 1917 stated for the first time that the curvature should grow, although less and less, and that the universe should therefore expand like a soap bubble. At least in theory, this seems to be the first suggestion of a dynamic, expanding universe.
Still on the theoretical level, in 1922 and 1924, Alexander Friedmann published two articles considering dynamic solutions to Einstein's equations. Indeed, if one abandons the hypothesis of a static universe, the relativistic cosmological problem leads to infinite solutions in which space varies as a function of time. Thus, many possibilities arise for considering an evolving universe, and the scientific literature has been greatly enriched by these considerations.
Described in very thick strokes and according to these equations, the universe can take one of three possible alternatives: a closed universe, an open universe or a "flat" universe. A closed universe will have a radius of curvature that will behave in an oscillatory fashion with successive expansions and contractions in space. The expansion of the universe progresses to a point at which gravity begins to assert itself and will cause it to retract, or it will grow to a constant dimension, as in the case predicted by Einstein. If the universe is open, it will be in permanent expansion, which may or may not be accelerating.
In all three of these theoretical cases, a singularity in the origin of time is to be noted. Considering the backward flow of time, the currently expanding universe must have started from a very high density of mass and energy concentrated at a single point. With this idea, for the first time, science begins to consider with its method the problem of the existence of an "origin" for the universe; a problem that already had a long tradition in theological and philosophical thought. It should also be noted that this origin coincides with the origin of time and space, which are no longer separable.
In the first two decades of the 20th century the quality of astronomical data increased dramatically thanks to improvements in the design and construction of telescopes. During the 1920s to 1930s important observations were made. Telescopes, in particular the Mount Wilson telescope, made it possible to resolve images from the most distant nebulae and to analyse the redshift of the luminous radiation coming from them. These results were key and would later make a major contribution to the consolidation of the theory. Firstly, because the calculation of the distances to the distant nebulae was improved: for the first time they were placed correctly, far beyond the Milky Way. As a consequence, the known universe increased surprisingly in size and all theories had to correct for this.
The first observations of the redshift of light from the most distant nebulae were made by Vesto Slipher between 1920 and 1930, but he was not the only one. In 1923, Edwin Hubble concluded that these distant spiral nebulae, which were then observed at the limit of resolution, are actually clusters of stars, i.e. galaxies like our Milky Way. A fact that greatly clarified the landscape of astronomical experimental evidence.
Hubble himself, by means of observations obtained with the Mount Wilson telescope in 1929, calculated the mutual velocity of the galaxies moving away from each other using the Doppler effect, and proved that this displacement is proportional to the distance. This became known as the "escape of the Galaxies". By obtaining this law, in particular by observing the most distant stars, Hubble obtained nothing less than the speed at which the universe is expanding. But until then, no theoretical interpretation of this phenomenon was known. That speed seemed to increase with distance.
Continuing with the historical development of scientific ideas, we should note that the astronomical data of the "galaxy escape" was quickly regarded as one of the most obvious supports for the theory of the expansion of the universe. The Belgian scientist and priest George Lemaître took things further and anticipated that if the present universe is expanding, going backwards in time, like a movie backwards, the universe must have started at a singular point where all the subject and energy was concentrated. He called it the "primeval atom" and assumed a common origin for time as well as space.
From the point of view of science, to consider a simultaneous origin for time and space means to consider a time zero from which space is born, space expands, and the universe increases in size as time goes on. Depending on the different models, when the details are considered, this expansion will have different effects and durations. But above all of these, the concrete fact of expansion is already considered as experimental evidence, which can be determined from the redshift of luminous radiation from space. In particular, the radiation coming from the most remote places where this effect is greatest.
But what does this shift consist of?... If we study the white light emitted here on Earth or from very distant stars, we already know from Newton that it is made up of different colours, what we call the "light spectrum". If we shine a beam of white light through an element that scatters it, such as a prism or a diffraction grating, we observe that the white light is broken down into its fundamental colours (the colours of the rainbow).
We have also known scientifically since Maxwell that light is an electromagnetic wave and that the human eye is our detector. In the theory of electromagnetic waves, each colour corresponds to a frequency, and of all the frequencies that permanently cross space, the eye detects only a small region. A property of all electromagnetic waves travelling in a vacuum is that the product of their frequency and wavelength is a constant. This constant is the propagation speed of these light waves (approximately 300 000 km/s). Once the frequency is known, it is immediate to calculate the wavelength (or vice versa), and through optical experiments, it is relatively easy to determine the wavelength.
When the source of light is in motion, a shift of the received frequency occurs which depends on the speed of the source and is known as the "Doppler effect". An effect that is most easily understood with sound. It is common experience that an approaching source sound appears to increase in frequency while moving away a shift towards lower frequencies is heard. This shift towards lower frequencies is known in optics as: "red shift". Zooming in would produce the opposite effect, i.e. a shift towards the higher frequencies, which are the blue-violet frequencies of the spectrum.
Returning to the history of ideas, as already mentioned, it was George Lemaître who was the first to relate the displacement of galaxies to the solutions to Einstein's equations in the dynamical case. And he did so before the publication of Hubble's results. B mathematician, after studying at postgraduate program in England and the United States, he returned to Belgium and was appointed professor at the University of Louvain in 1927. He discovered, after Alexander Friedman and independently of him, that the equations of general relativity admit such dynamical cosmological solutions. As his status as a theoretical cosmologist was accompanied by a strong interest in the results of astronomical observations, he took into account the data from American observations on the velocity of displacement of galaxies, assigned them a physical significance in his theory, considered them as a clear indication of the expansion of the universe, and theoretically anticipated Hubble's Law.
When he formulated the bold evolutionary hypothesis of the "primitive atom" he introduced into science the most important idea we have today about the evolution of the universe. According to this theory, the universe must have started from a kind of small, extremely dense, elementary atom, which evolved in a gigantic explosion and whose successive splits and clusters constitute the universe we observe today.
Lemaître presented this idea in a paper he published in 1931 and was initially poorly received by the physicists of the time. Probably partly because he was a theoretical mathematician, but probably also because he was a religious man. Perhaps these are the reasons for the resistance that usually accompanies profound changes in thought. This evolutionary model was unattractive to some physicists, because it allowed philosophers to go back to a "First Cause" for the whole Universe, to a "Creation", which seemed to take the problem of origin out of physics. The theory was then presented as an unconvincing alternative to Einstein's stationary model , which was enriched by some later contributions.
In 1950 Lemaître presented a book condensing his thinking graduate "The hypothesis of the primitive atom: a essay of cosmogony", but a new edition of the steady state theory, mainly by Gold, Bondi and Fred Hoyle, had already become popular among scientists and the general public, and had been elaborated by basic studies on the formation of the elements.
It was a bad time for the "primeval atom" theory. At a congress in Pasadena, Fred Hoyle mocked Lemaître by introducing him with the words "this is the big bang man...". ("this is the big bang man"). But not everything turned out to be negative; from that moment on, Lemaître's theory was baptised as the "Big Bang" theory, a name that has now lost its pejorative character, has great popular acceptance and is the name by which the theory is known today. To regain its initial novelty and interest, the theory of expansion from an initial singularity had to wait for new experimental evidence.
A few years before the event in question, a former student of Friedmann's, George Gamow, had put Lemaître's theory back on the stage, specifying that that early universe, besides being denser, must have been much hotter and predicted in his calculations the existence of a remnant of cooled radiation, i.e. something similar to a "fossil" from the early stage of the universe, which should be present in all corners of the universe. This radiation is known today as "background radiation".
To clarify things a little, let us remember that the laws of black body radiation allow us to associate a temperature with the colour of the radiation emitted by a hot body. For example, an iron heated to just over 1000 ºC appears red; if it gets hotter, it turns white. The intensity distribution for these colours is known as Planck's Law and is represented by a curve whose maximum shifts with the temperature of the body (Wien's Law).
Given the time that has elapsed in the universe since the original big bang and its great expansion, this radiation predicted by Gamow should correspond to a very high temperature leave. At summary: Lemaître's model lacked thermodynamics and Gamow provided it.
When in 1965 two Bell scientists, Arno Penzias and Robert Wilson, were measuring a receiving antenna of a microwave telescope and found a persistent isotropic background noise, corresponding to a very high temperature leave (3 K), they did not suspect that this noise was related to the origin of the universe predicted by Gamow. But someone recalled hearing in 1964 in a lecture by J. Peebles, a Princeton cosmologist, that this radiation was predicted by Gamow and was compatible with dynamical models of the universe. Thus, almost by chance, the two concepts are associated and one of the strongest pieces of evidence in favour of the big bang theory appears.
Many more investigations were prepared to confirm these data. In 1992, the COBE satellite made measurements on the distribution of the background radiation of the universe and more recently, in the year 200l, the reconstruction of its complete map was achieved, which confirms even more, if possible, the validity of this model.
Meanwhile, the model was completed with studies of the formation of the subject from the radiation of the early universe. The processes of nuclear fusion and formation from hydrogen, helium and metals such as lithium had already been studied in 1948 by Alpher, H. Bethe and Gamow.
When we begin to understand the processes of formation of heavier nuclei, nuclei that are produced in the special conditions of temperature and pressure that exist in the interior of stars, the rest of the story begins to be reconstructed. These processes were studied by Burbidge, Burbidge, Fowler and also by Fred Hoyle, who, despite his irony in Pasadena, contributed with these works to fill in the Big Bang idea that he had previously opposed. The world of the smallest, elementary particles, and the world of the largest, astronomical objects, come together to form the current theory of the evolution of the universe. Evolution of which we have a fairly complete scientific description, almost from its origin.
Roughly speaking, today we can say that 99% of the visible subject of the universe is made up of hydrogen and helium. The remaining 1% is made up of the heavier elements which astronomers collectively refer to as "metals". Their relative abundance, formation temperature and the time at which they formed can be seen in the figure. With the present data and accepting the "inflation" hypothesis, we can summarise the history of the universe as follows:
In the initial instants, during the so-called "Planck time" (10-43 s), the universe was filled with very dense energy, at a temperature and pressure corresponding to that state. It then rapidly expanded and cooled, undergoing phase changes of the subject kind that occur during the condensation of a vapour, but involving elementary particles. At about 10-35 of the first second, the universe undergoes a phase change that triggers a stage of exponential expansion, known as "cosmic inflation". This stage of inflation produced as result a plasma of elementary particles called "quarks" and "gluons", with relativistic motion.
The increase in the size of space causes further cooling, which continues until another phase transition occurs and "baryogenesis" occurs, the genesis of the components of the atomic nucleus, about which still very little is known. It is estimated that at that time the "baryonic mass of the universe" was formed and the asymmetry between subject and antimatter observed today was produced. That is, at that time the quarks and gluons, which were free until then, combined to form baryons such as the proton and neutron, the building blocks of the atomic nucleus.
As the expansion continues, cooling continues and further phase changes continue to break the initial symmetry, giving the current shape to the forces of physics and elementary particles. From here, it is simpler to infer that the union of protons and neutrons will lead to the formation of deuterium and helium nuclei, a process called "primordial nucleosynthesis".
Then cooling causes the subject to stop moving relativistically and the energy density begins to gravitationally dominate the radiation. After about 300,000 years, electrons and nuclei combined to form atoms (mainly hydrogen). By this union, the radiation decoupled from the atoms and continued to travel freely through space, i.e. the universe became transparent. This radiation, cooled by the expansion, is the microwave background that we observe today, at final, a "fossil" of the universe at that time.
The description goes on to consider that, in those regions where the subject is slightly denser, it tends to gravitationally gather into clouds, stars, galaxies and the rest of the Structures currently observed. To describe in detail the formation processes of these Structures it is necessary to know the subject and the amount of subject in the universe. It is currently estimated that there are three types of subject which are: the cold dark subject , the hot dark subject and the observable "baryonic" subject , which is the one that interacts with electromagnetic fields.
The isotropy of the microwave background was thoroughly studied, trying to find traces of those initial anisotropies that gave rise to the training of the first condensation nuclei of subject. In 2003, the best available data from the WMAP satellite (Wilkinson Microwave Anisotropy Probe, at Spanish: Wilkinson Microwave Anisotropy Probe) were released. These data confirm that the most common form of subject is the dark cold subject . The remaining types would make up 20% of the universe's subject .
Cosmologists have been able to calculate many parameters of the universe with these data, with data from the Hubble Space Telescope and the 1989 COBE satellite. These data have established that the microwave background is isotropic to one part in 100,000 (1/105) with a residual temperature of 2.726 K).
Regarding the theory, dark energy takes the form of a cosmological constant as posited in Einstein's field equations and there are other models, but the details of this equation of state and its relation to the standard model are still being investigated.
In the early stages of the universe, the energies that particles had were higher than those that can be reached today in a laboratory (to reach them, assuming it were feasible, it would be necessary to build an accelerator of a length comparable to the distance to the sun). Therefore, no experimentation is possible and there is no convincing physical model for the first (10-33 s) of the universe, the time before the phase change that is part of the "Grand Unification" theory of forces (GUT).
For the first instant, Einstein's gravitational theory predicts a singularity where densities are infinite. To try to resolve this paradox, a quantum theory of gravity is needed. One of the biggest unsolved problems in physics.
Of course, we know nothing about what existed before the Big Bang, although theoretical speculation is never lacking. The possibility of the existence of parallel universes had already been anticipated by the German philosopher and mathematician I. Kant, today we would say "multiverses", each with its own big-bang, cosmological constants and laws of physics, but for now, and it seems that for a long time to come, all these theories are just that: speculations.
Experimental data have confirmed that the expansion exists, it is accelerating, and few scientists today think that a stationary model is possible for the universe. Therefore, the theory of a final regression (or "Big Crunch") is currently very little accepted.
The evolution of the universe as it has been described (with general relativity together with the "model standard" of elementary particles) is also accepted today by most scientists and specialists.
But this should not lead us to think that we know everything about the origin of the universe and its future. To estimate its future evolution, we work on analytical extensions of current theories. In these cases of such long-term projections, it is known that science usually describes very well the previous processes and their probable continuation. But science can say little about the possibility of new emerging phenomena, new discoveries or unexpected results in observation, a situation that has been normal in its history. For example, today it is thought that most of the subject that makes up the universe is "subject dark", about which nothing is known. Nothing is known about dark energy either, although there is no lack of theories for all these cases.
We do know, "for sure", that the visible universe is expanding and cooling, and that some stages of the initial big bang have very strong experimental verification. The rest, as stated above, is speculation for now.
The picture we have presented so far is derived from the scientific method. According to this method, theories are confirmed or abandoned if the results of experiments and observations on reality do not verify the anticipated conclusions. Occasionally, these same experiments provide novel data that do not fit into existing theories and require new formulations. As a whole, the development of this method implies an interactive process where theory and experience modify each other until advances are made in our worldview, which we consider to be secure only when the synthesis is achieved. A relative security, which is maintained within the framework of validity in which the ideas have been tested.
The concept of the Universe that we will analyse in this second part comes from sources very different from science. In this case, the concepts to be reasoned about (and which, as we shall see, call for action), come from a spiritual experience at the beginning of which is God himself. And God is not a philosophical idea. For all monotheists He is a Person. He is the Being par excellence, the only Necessary Being, as He has revealed Himself to us: God is the One Who Is, that is to say, the only Being Who Is by Himself. The rest of us are contingent beings, created by Him.
When we affirm that we are contingent beings, we do not introduce anything new with respect to the previous view: for science, this is also evidence. Man did not create the universe, nor did he create himself, and therefore, with respect to nature, we are also contingent. But in our religious conception there is a fundamental difference, God stands above nature, he is both the Creator of nature and our Creator. In this sense God is superior to fate, unlike other religions of antiquity which, like the Greeks, assumed that their gods were subject to fate.
The starting point, our first affirmation on this path is, then, our personal recognition and acceptance (at least) of the possibility of the existence of this Being. Without this step we can neither move forward nor understand the new conception of the universe that faith presents to us.
This step of affirmation is never complete, it is not without its doubts, nor is it the only one in a man's life. We can identify and observe in other human beings the progress and setbacks in the growth of their relationship with God. A relationship that is built through reflection, but fundamentally, through spiritual experiences in which each human being begins to consider, through different paths, that this physical universe of which he himself is a part, in which he develops and evolves, to which he looks out with his thoughts, has a meaning. A meaning that he as a human being can come to understand.
Thus, the image that man forms from faith is not that of a universe that is the product of chance or of blind and alien forces. It has an established purpose, a direction of evolution towards a certain end that justifies and transcends it. Man understands that although he himself is a creature, an almost insignificant part of creation, his Creator is concerned, freely, for his growth and development within that global sense that he gave to the universe.
The experience of faith is not an easy or massive experience. It is initiated personally, unfolds person to person, in average light and in voice leave. God manifests himself through "a whisper" (Psalm 18, verses 2-3), like a "light breeze" (Elijah) or hides "behind a cloud" (Moses). He comes to us through a book, the word of a friend, an illness,... through a thousand paths that we must learn to follow in order to recognise him. God does not force human freedom, man has at each stage of his personal growth the possibility of accepting or denying Him, of understanding or rejecting Him.
But the growth and maturation of the content of faith, the dogma, is not an individual task, the fruit of a solitary thinker, but derives from a communal experience unfolded over a history of millennia. Therefore, at the beginning of this second explanation of the origin of the universe, the human being does not only involve his reasoning; he needs to accept personally that God confers a marvellous meaning to that reality which he, as a human being, observes, suffers and modifies. He also assumes that this meaning is beyond his will and that it surpasses human reason and the human knowledge . Man is not the author of the project of creation, but he can scrutinise its traces and formulate theories, which will always depend on revelation. As his culture changes with the times, this sense of his destiny does not manifest itself to him immutably, once and for all. His interpretation develops in history and evolves as human knowledge progresses. His personal experience makes sense as an extension of the experience that many other people have of God: a whole people, the "people of God". A community of faith whom God chooses not by merit, but freely, out of love. The faith is not our faith, it is the faith of the whole Church.
Behind every scientific interpretation of the universe that we humans construct, each time in a more complex and perfect way, the meaning that God has given it will shine forth and will come to illuminate the knowledge that we forge for ourselves with reason. We only fully understand nature when, in addition to observing it with the eyes of science, we see its meaning in relation to God's plan. Then it becomes transparent and intelligible, an intelligibility that is not the work of man, but comes to us from God, from the fact that we share with the rest of creation the character of creatures.
We call the whole of this explanation in history Revelation, and it is the basis of the content of our faith. This faith will allow us to interpret what the universe means for man when it is given historical, transcendent and eschatological meaning. Revelation is to faith what knowledge is to reason.
This knowledge recognises two specific sources: Tradition and the Holy Scriptures. Oral Tradition is prior to the Holy Scriptures. The Sacred Scriptures gather together the revelation, first of all, that which God gives to the people of Abraham and Jacob through their prophets, and then, definitively, through his Word incarnate: the Logos, Jesus Christ our Lord. Through the disciples whom He chose, it reaches the people of God, and through them it must reach all the rest of the human race.
For Catholics, Tradition is expressed by the Magisterium of the Church, the repository of the content of this Logos and responsible for its adaptation to each historical moment, for its adaptation to "the signs of the times". These are the two inseparable sources that the Christian faith has for interpreting the origin of the universe: Sacred Scripture and the Magisterium of the Church.
If we want to begin the analysis of the sources coming from the Sacred Scripture, we must turn to the written tradition in the Old Testament that we received from the people of Israel. The references to the origin of the universe in the Sacred Scripture are at the beginning of its first book, "Genesis". In its chapter I, first verse, the Bible says: "Bereshit bara Elhoim...", i.e.: "In the beginning God created the Heaven and the Earth...".
God: the necessary Being, the One who is by Himself, as He will later tell Moses from the burning bush, created all that we know. No one on earth can assign God a human name; the best we can say about Him is revealed to us by Himself: I am who I am. He created us and we cannot bridge the gap, and it is He who takes the initiative.
He has created the "primeval atom". He has created the Earth that was before us, the Universe that was before the Earth, and He is before the Universe, time and space. This idea of God, transcendent to every idea, subject or energy we can think of, is scattered throughout the whole biblical Old Testament conception. God transcends all that is natural. The texts of revelation multiply: Genesis II, 5-25, The Psalms, 2 Maccabees VII, 28....
That conception passes complete into the New Testament. "In many ways God spoke to men, until he sent his own Son"..., his Word [St. Paul]. God sends his Word to earth. But his Word already existed before creation.
St. John the Evangelist tells us in the 2nd century (AD): In the beginning was the Word... [Jn. 1,1]. The word of God, the Christ, was before the universe and Christ is the prototype of the human being, the new Adam. This revelation reaches a dimension that transcends all thought: on the one hand, God takes on human form and assumes this nature, but on the other, man finds his origin as nature, before creation.
The possibility for us to understand the meaning of the natural world for us comes from the Word of God, which existed before creation. If there was evolution, God knew about it result before it began. Therefore we humans, ourselves, were thought by God before the existence of time and we are destined here on this earth to meeting with Him.
Naturally, Revelation does not tell us why procedure we were created, nor does it communicate scientific data, we are free to find out. Revelation gives meaning to our life and tells us how we should live it, because at the same time, the freedom that God has given us, forces us to choose at every moment: we can assume our destiny and fill our life with meaning or reject it and empty ourselves of it.
Later the Tradition of the Church, without the living presence of the Incarnate Word, but assisted by the Spirit of God, will recall, reinforce and purify the concept of creation that has been forged from Christ's own teaching. For example, we read in St. Justin (100-160 AD): ... "It is the doctrine which teaches us to worship the God of Christians, whom we hold to be the only God, who from the beginning is the maker and maker of all creation, visible and invisible".
This formula, now distilled, would eventually be incorporated in the Apostolic Creed or Symbol (3rd century): "I believe in God the Father... creator of heaven and earth"..., and would be perfected in the later Councils of Nicaea (a.325) and Constantinople (a.381), where it appears in the so-called "Nicene-Constantinopolitan" Symbol with the formula: "Creator of heaven and earth, of everything visible and invisible...".
In 1215, at the Fourth Lateran Council, the "Firmiter" decree was established, containing important principles such as: the unity of the creative principle (God is One and indivisible, He has no parts), the distinction between God and the world, the creation of the universe out of nothing (ex nihilo), the temporal nature of creation (God also creates time) and the extension of creation to all living beings, to the whole of nature.
St. Thomas Aquinas (1212-1274), in Summa Theol. q. 46, a. 2, comments that the temporal beginning of the world is a datum of faith. And that the creation out of nothing, ex-nihilo, can be proved by reason.
For centuries, the topic is thus accepted among Christians and ceases to occupy a central place in doctrinal discussions. It is not central, despite the discussion concerning the heliocentric system in the 17th century, because considered from the perspective of faith, it does not have much bearing on what we are dealing with here. In fact, the origin of the universe and creation were not discussed there.
More recently, during the First Vatican Council, topic was dealt with again in depth, and it was established, among other things, that: ... "the universe is the excellent work of a good and wise God, who made all things with an absolutely free will". In other words, God had no need to create it, creation is a free expression of Divine Love.
A new scientific vision had emerged that challenged the religious perspective on the creation of man, this time from a naturalist point of view, opposing it with the possibility of evolutionary continuity from simpler species, subject to processes of natural selection (Darwinism).
This new scientific proposal was quickly seen as a demonstration that the consideration of the existence of a creator was totally superfluous. Faced with the attempt to overturn the religious vision of the creation of man and the universe, the Church reaffirmed the contents of Revelation.
It is prudent to point out that, while evolutionism considers ideas about the origin of man, it is not really about the origin of the universe. Furthermore, much more than the origin of life on the planet, it is a theory about the transformation of elementary forms of life into more complex forms. But this topic deserves a particular, much more extensive and detailed consideration, for which reference is made to the relevant bibliography (which can be found on the above-mentioned website).
The First Vatican Council defines that: "God sustains and governs all creation through his Providence". This clarification was necessary in the face of the mechanistic reduction that was deployed in the physical sciences during the 19th century, starting with the development of "Rational Mechanics" (from Laplace to Mach) and Thermodynamics. According to these reductionist conceptions, one could come to admit, validly for scientific reason, the existence of a creator god, who sets in motion his creation of the universe and then abandons it to its fate. Or that of a natural pantheism, a universal "watchmaker" god who controls and participates in all the movements of the universe, i.e. what we call nature.
A Jew, a Christian or a Muslim would reply that it is impossible to pray to such a god. The idea that those of us who believe in God have of God is much more transcendent than this and at the same time, surprisingly, much closer. With the above-mentioned formula, the Magisterium clarifies the Christian conception of a personal and provident God.
Vatican I is prolific with regard to topic, in the "Dogmatic Constitution on the Catholic Faith" it clarifies that ... "this one true God, by virtue of his goodness and omnipotence, not for the sake of increasing his glory or acquiring it".... "made the world to communicate his goodness and perfections". He devotes a chapter to specifying the relationship between faith and reason, declaring that ... "there is a twofold order of knowledge, distinct not only in its principle but also in its object".... 35] He only confirms what St Thomas had already stated 600 years earlier.
But the great document of the 20th century is the Second Vatican Council. The number of topics discussed was so wide-ranging and so comprehensive that references to the creation of the universe could not be omitted. The secular doctrine of the Church as described above is reflected in numerous works discussed by the Council Fathers, which were later published in various special documents.
Examples are the Council Constitutions "Lumen Gentium", "Dei Verbum" and "Gaudium et Spes". They emphasise the mystery of creation, the Christocentric vision of creation, the collaboration of man, a unique creature of God, who acts as a continuator of the created work, and the relationship between creation and the end of time.
On the initiative of John XXIII, the pope who convened the Council, the topics dealt with in the Council documents were discussed in subsequent years in order to draw up a catechism that would make them available to all the faithful. In this way they were incorporated into general Catholic thought and the Catechism of the Catholic Church. The Catechism is a document whose drafting was initially recommended during the Council, finalised during the 1985 Synod of Bishops and which came into being under the Pontificate of John Paul II, 30 years after the Council's inauguration.
In its first part, the Catechism analyses the Profession of Faith or "Creed". In the first chapter it proclaims that man is "capable" of God and in the second that it is God who comes to man at meeting . Between points 279 and 301 it analyses the origins of the universe and stresses the importance of a good catechesis on these subjects.
The succession of popes since the Council: John XXIII, Paul VI or John Paul II, in several speeches to the Pontifical Academy of Sciences, specified the details of the doctrine of the Church as all previous popes had done.
Pope John Paul II also apologised for any mistakes that may have been made in the so-called "Galileo case", as an act of goodwill to the world of science, to reaffirm the importance that the Church has always given to this activity of human reason.
In 1998, John Paul II published the encyclical Fides et Ratio (Faith and Reason), where the double goal of dialogue and autonomy that we highlighted at the beginning of this article, which was clarified by St. Thomas and which reaffirms what was established at the First Vatican Council, is proposed for this relationship.
The following words of His Holiness J. Paul II underline these objectives:
"In expressing my admiration and encouragement to these pioneers of scientific research, to whom humanity owes so much of its present-day development , I feel it my duty to exhort them to continue in their efforts, always remaining within the sapiential horizon in which scientific and technological achievements are accompanied by philosophical and ethical values, which are a characteristic and indispensable manifestation of the human person. The scientist is well aware that the search for truth... never ends, it refers to something beyond the immediate object of study to the questions that open up access to the Mystery".
From the Catholic world, there has always been an openness to science, establishing the necessary bridges for a serene and profound communication of the truth cited by His Holiness John Paul II at section above. Despite some disagreements, such as the one that arose around the Galileo case, the normal attitude among Catholics was to try to understand science in its deepest details in order to encounter the Mystery. In tracing physical reality back to the transcendent.
The relationship between religion and science is very important for us Catholics and religious people in general. Some of the most significant advances in the understanding of the universe, such as heliocentrism or the Big Bang theory, are due to people who are known to be religious. Galileo himself, despite what is said in some circles or in the media, was a practical Catholic. There are also many encounters and dialogues between great scientists with different religious convictions or atheists and Catholic scientists. The normal thing has always been the personal meeting , beyond their religious convictions, and it should suffice to demonstrate this by looking together at the photo of Albert Einstein and Robert Millikan flanking the creator of the Big Bang model , George Lamaître, in 1933.
A few years before this photograph, Hubble's law had been established, Lemaître was convinced of the dynamic model , he had introduced the hypothesis of the primordial atom in 1931, and Einstein did not share this scientific view. Nevertheless, they are there together. Einstein, who often praised the mathematical talent of the priest, and the latter, who used Einstein's equations to develop his dynamic model . A model that includes the origin of time together with the universe, coinciding with the definition of St. Thomas Aquinas, 700 years earlier.
This relationship between science and faith, within Catholicism, goes much further: the Vatican itself has a Pontifical Academy of Sciences where many of the most important scientists are invited to present their theories. Pope Pius XII himself was one of the most enthusiastic supporters of the Big Bang model , even before its widespread acceptance by the scientific community. Nothing could be more alien or more unjust, then, than the accusation of obscurantism that rains down on the Church from certain atheistic circles.
We have reached the final slide and we ask ourselves: What is the end of the Universe? We could talk about some recent scientific opinions extrapolating "thermal death" for an expanding universe, make considerations about possible alternatives, analyse the possibility of the existence of simultaneous universes, each with its fundamental constants and its Big-Bang, subjects on which the theory also speculates.
This does not seem to be the idea sought by Carlos Pérez for the closing of an exposition such as the one prepared in the series of slides he presented. To my understanding, the final message that these two lectures try to leave us with is that the end of the Universe, whatever happens physically, will be the complete opening to transcendence. It is not an end, but a finality.
For a man of faith, the end will transcend everything material. It does not matter how. From the point of view of science, even if we speculate with beautiful mathematical constructions, we do not know what it will be like, much less why. However, from the perspective of Christian eschatology, we do know that the end of the universe will be the full realisation of that meaning that we can guess today, in which we believe and which allows us to act accordingly, for the good of all our brothers and sisters, mankind.
According to our conception, at the end of time our partial knowledge will come to an end and we will see God as He is (1 Cor. 13,12). God will then have brought his creation to the final rest and glory for which he created the Universe, with our Heaven, with the Earth and with all of us at the summit of creation, allowing us to understand it and to collaborate with it (Catechism, 314).
In science, to explain the evolution of the universe, it is necessary to unite our knowledge of the smallest, the elementary particles, and the largest, the bodies of astrophysics: planets, stars and galaxies. To explain the meaning of the evolution of intelligent life on Earth, we see here that we also need to unite the largest and the smallest: God and man. Man is meaningless without God; he is reduced to an unreasonable fluctuation in the universe.
We occupy a privileged place in the universe: planet Earth. Many scientists analyse the cause and justification of this privilege, trying to calculate the probability of the appearance of intelligent life in other corners of the universe. That probability, it seems, is quite high leave. The earth is a habitable planet, at the edge of an arm of a galaxy, part of a universe with its cosmological constants finely tuned for life. And it is, at the same time, a vantage point from which to observe its planetary system, the shape of its galaxy, and even "the edges" of the universe. That is to say, with the instructions to form in your intelligence, a scientific worldview. A rather tight vision of the totality.
But from the perspective we are analysing here, the reason for that privilege transcends the physical and the natural, because this place where we live is the place of man's meeting with his Creator. Here the Word became Flesh and dwelt among us. He establishes our dignity as creatures. For in the beginning, before Creation, the Word already was.
That is our faith.