El universo en su infancia
The universe in its infancy
Author: Carlos A. Marmelada
Published in: Enlargement of article subject dark and dark energy, enigmas of cosmology. Childhood photo of the universe published in Aceprensa 038/03
Date of publication: 12 March 2003
A NASA probe, WMAP, has produced the most detailed "snapshot" yet of the early universe, at 380,000 years old. The new data helps to better explain how the present cosmos was formed from the Big Bang; but at the same time it reinforces the importance of the subject dark and dark energy, without revealing the nature of these entities. And, of course, they still don't say where the Big Bang came from.
1. Childhood photo of the Universe
Today, the vast majority of the members of academic community roughly consider the big bang theory to be the most correct cosmological conception we have of the origin of the universe. subject According to this theory, the universe would have arisen about 15 billion years ago (as it was estimated during the 1970s and 1980s) from the big bang in a singularity that would have given rise to space-time and all the energy that exists until now.
Our scientific theories have no way of knowing what happened between the moment of the big bang (t = 0) and the so-called Planck time (t = 10 raised to -43 seconds). The physicist James S. Trefil calls the period between these two instants the Dragon Age, to express in a sympathetic way the lack of knowledge that cosmologists have of this crucial time span. Anything we say about what happened in the Dragon Age is pure speculation. In many cases it will be a truly admirable intellectual display thanks to the grandiose mathematical apparatus that accompanies it, but speculation nonetheless. Why? Because there is no humanly possible way to carry out experiments that reproduce the physical conditions that must have existed in that period of time. To do so, we would need to build a particle accelerator the size of the solar system and, in addition, we would need to use amounts of energy absolutely beyond our reach. These are two insurmountable practical difficulties. These two handicaps are too great to be overcome in the short or medium term deadline, and it is even unthinkable to solve these issues in the long term deadline. Of course, other, more modest experiments can be designed, but they will not be able to reproduce the exact conditions of the Dragon Age. They will be experiments whose results can only be extrapolated, with all the limitations that this implies. Thus, all explanations given by the theories that want to describe the events of the Dragon Age will be purely theoretical speculations.
Once the Planck time has passed, things change substantially. Physical theories can explain with an admittedly high degree of plausibility Degree what most probably must have happened in reality. To be on the safe side, many of the predictions made by these theories have been tested in particle accelerators.
However, it is one thing to have a theoretical knowledge of the universe in its infancy through mathematical calculations or particle accelerator experiments extrapolating their conclusions, and quite another to have an empirical observation of the universe in its earliest infancy.
The technological development has allowed us to launch into space a probe capable of taking the "childhood photo" of the universe, the oldest and highest resolution photo ever taken, although we hope that the European Planck probe will be able to surpass it in 2007.
NASA's WMAP probe has made it possible to compose by computer the most detailed picture ever obtained of the early universe, when it was "only" 380,000 years old, i.e. when it was just a "baby" compared to the 13.7 billion years it is today. The data provided by WMAP has given us a better understanding of how the universe has been formed since the big bang, especially with regard to the large Structures such as stars and galaxies. However, as is almost always the case in science, the answers provided by new knowledge are accompanied by new questions. Thus, the data obtained by WMAP confirms the importance of the subject dark and dark energy in shaping the universe as we know it today, although, unfortunately, WMAP has not been able to reveal anything about the nature of these two entities, which are the two great enigmas facing cosmology today. Two fascinating challenges that have cosmology in check and that are absorbing the most notorious efforts of theoretical physicists and astronomers.
Despite this lack of information on dark energy and subject , the contributions of the WMAP probe are very important. When analysing its data, scientists could not help but be surprised. Cosmologists and astrophysicists alike agree that our knowledge of the origins and evolution of the universe, the birth of the first stars and the training of the first galaxies will have to be revised in the light of the new data.
training Until recently, cosmologists believed that the first stars had formed almost a billion years after the big bang; that the dark subject had not played a relevant role in the formation of these stars; that the universe was between 10 and 20 billion years old; and that its expansion was slowed down by the action of gravity. These were the basic elements of our view of the cosmos until the early 1990s. During that decade, numerous anomalies in this paradigm raised suspicions that things could not be exactly like that. The data provided by WMAP confirms these suspicions and forces us to review our knowledge of these issues.
The Microwave Anisotropy Probe (MAP) satellite was launched into space on 30 June 2001. It was later renamed: WMAP in honour of the report of David Wilkinson, NASA cosmologist and one of the first directors of project until his death in September 2002. The probe took three months to reach its orbit 1.5 million kilometres from Earth. During each revolution it makes a complete scan of the sky every six months.
3. The age of the universe
In the early 1930s, thanks to the work of Edwing Hubble, it became indirectly "observationally" evident that the universe was not static but dynamic and that it was expanding, so that galaxies were moving away from each other. Thus became popular the evidence, suggested theoretically by George Lemaîttre in the late 1920s, that if we ran the film backwards there would come a time when all the subject and energy would be united in a space-time singularity. But how much time would have elapsed from the big bang to the present day? Or, in other words, what is the age of the universe?
The first calculations, made by Hubble himself in the 1930s, produced a disconcerting figure, which gave the universe as being about 2.5 billion years old. This was absolutely impossible because the age of the Earth was already known to be more than 4 billion years old. There had certainly been some error in the calculation. This paradoxical status has, in one way or another, continued to hold until very recently, as there was the disturbing status that new calculations for the age of the universe often gave figures where the universe was younger than the oldest stars .1which is impossible. Although new calculations increased the age of the universe, it was not enough and, above all, these hesitations and ad hoc modifications served the critics of the big bang as an argument for the weakness of this theory. In the 1970s and 1980s it was normal to claim that the universe was about 15 billion years old, an almost standard, somewhat conventionally accepted figure. However, in the 1990s, with the commissioning of satellites such as Hipparcos2or the Hubble space telescope, an attempt was made to solve the problem of the age of the universe. In fact, one of the main reasons why Hubble was built was to be able to determine once and for all the true value of the Hubble constant (Ho), a fundamental constant for determining many of the essential parameters of our universe. knowledge .
The European Hipparcos satellite was launched into orbit on 8 August 1989 by an Ariane 4 rocket. It remained in service until 1994. The final data of the mission statement was ready in 1996, on the seventh anniversary of the satellite's launch. It was a true three-dimensional map of the universe. Hipparcos measured the brightness and distance of more than one hundred thousand stars with unprecedented precision. As a result, it was possible to establish that: "the age of the oldest stars has been rejuvenated by about 4 billion years; the age of the universe is now estimated to be between 10 and 20 billion years".3.
We have already said that finding the value of Ho, the Hubble constant, is crucial to determine our knowledge about many aspects of the universe. Experts in the study of the evolution of the universe need to know its exact value in order to determine the fate of the universe. Experts in the training of galaxies need to know its exact value to be able to pinpoint how much time elapsed from the big bang to the training of the first galaxies. Those who delve into the theory of relativity need to know its value in order to be able to determine whether or not the introduction of the cosmological constant is necessary. The cosmological constant is one of the most feasible possibilities to explain the current accelerated expansion of the universe. It would represent an anti-gravitational repulsive force from the energy of the quantum vacuum that would cause the universe to be currently expanding at an accelerating rate, rather than decelerating, as the logic of the classical big bang concept would dictate. We will return to this later.
The programs of study from the data provided by Hipparcos determined that the Hubble constant had an approximate value of 60 plus-minus (+/-) 10 km/s/Mpc. That is: a galaxy would move away from us at a rate of 60 km per second for every megaparsec4 distance from us. This means that: galaxies that are 3.3 million light years away will move away at a speed of 60 km/s; those that are two megaparsecs away from Earth (i.e. 6.6 million light years away) will move away at 120 km/s, those that are three megaparsecs away will move away at 180 km/s... and so on and so forth. If the value of Ho were really 60 km/s/Mpc, then the universe would be about 12 billion years old.5.
programs of study of Cepheids6 The Hubble Space Telescope's variable values determined that the Hubble constant had a value of 70 +/- 10 km/s/Mpc, so that the minimum age of the universe could not be less than 12 billion years, and, for its higher values, it should be around 13 billion years. These data were made official during the annual congress of the American Astronomical Society, held in the first week of June 1999.
However, data provided by the WMAP probe is much more precise... and reassuring. Indeed, according to this NASA satellite, the age of the universe must be 13.7 billion years old, with a margin of error of only 1%.
These are reassuring results because in the mid-1990s it was said that "recent measurements of the speed of cosmic expansion, the Hubble constant, suggest that the universe may be younger than previously thought. Some of the observations suggest that it may be less than 10 billion years old, although stars have been seen in our Milky Way galaxy that are thought to be far older than that. If both the data of the Hubble constant and the ages of the stars are correct, then there is a contradiction, an impossibility! If we have to admit that the elliptical galaxies close to 3C234, with a redshift of 1.2, already had advanced ages, the problems become even more acute ."7.
As we have seen, WMAP has shed light on the value of Ho, and its data seems to gain the confidence of scientists since "measurements (of small fluctuations of the cosmic microwave background radiation by) the WAMP satellite, combined with other analyses, have yielded a Ho very similar to that of the Key Project: the central value, within a margin of experimental error, is 71."8.
One of the main reasons why the Hubble Space Telescope (HST) was built was to be able to measure Ho more accurately. The Key Project (or project core topic ) is one of the TEH programmes aimed at achieving this goal. It was the largest project undertaken by the telescope in its first decade of service and was completed in 2001, after eight years of work. The Key Project combined the results of several Ho measurement methods and obtained "a weighted average of these values [which] gives a result for Ho of 72 +/- 8".9.
4. The training of the first stars and the first galaxies
For decades it was thought that the first stars must have formed about a billion years after the big bang. However, data provided by WMAP suggests that they formed much earlier, around 200 million years after the big bang. This confirms what has been suspected recently, that "according to cosmological models, the first small systems capable of forming stars appeared 100 million to 250 million years after the big bang ".10.
The WMAP probe was not able to directly observe the light emitted by the first stars, but identified a polarised signal that is an unambiguous trace of the energy released by the first stars in the universe. On the other hand, the WMAP map of the early universe, when it was only 380 000 years old, sample is not perfectly homogeneous. If it had been, we would not exist today. At that time there were small temperature fluctuations (known as inhomogeneities or anisotropies of the Cosmic Background Radiation or the Cosmic Microwave Background; CBR or CMB respectively) that indicate the presence of tiny aggregates of subject which, over time (about two hundred million years) would give rise to the first stars and, later, to the first galaxies, thus generating the immense galactic macrostructures that today make up our universe. These Structures, today, in addition to stars and galaxies, comprise galaxy clusters and galaxy superclusters. For example: our planet, and the star around which it revolves, is located in the Milky Way, specifically at the outer edge of one end of one of its arms. Our galaxy, in turn, belongs to the group Local cluster of galaxies, which is made up of about 30 galaxies. In turn, this cluster, together with others, forms a supercluster of galaxies called the Virgo Supercluster. Superclusters appear to be the largest megastructures that the universe allows. Until now, no macrostructures larger than superclusters of galaxies have been detected, for example: clusters of superclusters of galaxies. But have we not detected them because we have not developed the technology or the mathematical apparatus to do so, or because they cannot exist? From programs of study very recently, we know that it is the latter; the geometry, density and, at final, the parameters of our universe do not allow it.
But how did WMAP know that the stars had formed five times earlier than was widely assumed? Because "after the emission of the FCM radiation, some 380,000 years after the big bang, most of the photons travelled through the universe without scattering. But some were scattered by charged particles, which polarised the radiation across wide swathes of the sky. Observations of this large-scale polarisation by the WMAP satellite show that a fine mist of ionised gas scattered about 17 per cent of the FCM photons a few hundred million years after the big bang. This high percentage is perhaps one of the biggest surprises of the WMAP data . It was assumed that the radiation from the first stars, of very large mass and brightness, ionised most of the hydrogen and helium in the universe. This process is known as reionisation, because it returns the gas to the plasma state it was in before the emission of the FCM. But it was estimated to have occurred almost a billion years after the big bang; in that case, only 5 per cent of the photons would have been scattered. That WMAP observed a higher percentage indicates that reionisation happened earlier. This finding puts the training models of the first stars in trouble".11.
Thus, the high percentage of photons that were reionised (and scattered) after the emission of the microwave background radiation indicates that stars formed much earlier than previously imagined. Therefore, dating the training of the first stars is possible thanks to WMAP's ability to make measurements of the polarisation of the RCF. As mentioned above, cosmologists used to think that the first stars formed much later and this was explained by models that incorporated the hot dark subject . The new data provided by WMAP suggests that the dark subject is cool dark matter (CDM or Cool Dark Matter).
5. Anisotropies and inhomogeneities of the RCF
Cosmologists estimate that the universe started to become transparent (i.e. subject and radiation separated) about 300 000 years after the big bang. The WMAP satellite was able to detect the characteristics of this radiation when it was 380 000 years old. Therefore, the images obtained by WMAP would correspond, practically, to the first moments of the visible universe. Stars did not even exist then. What WMAP has captured is the famous cosmic background radiation (the CBR) predicted by the big bang theory; something like the echo of the big bang with which, according to the current paradigm, the universe began to exist. mission statement WMAP was launched into space with the aim of obtaining more detailed images of the RCF than those obtained by COBE (Cosmic Background Explorer), a satellite that in 1992 caused quite a stir by providing images of this radiation. The resolution of the instruments carried by COBE showed that there were certain inhomogeneities (irregularities in the distribution of the subject and energy in the space of the nascent universe) that could account for the training of the superclusters of galaxies (the largest macrostructures known to date). WMAP was launched into space with the appropriate technology to find inhomogeneities or anisotropies that could explain the training of galaxy clusters (the component elements of galaxy superclusters). WMAP has managed to capture the highest resolution and highest definition images of the RCF to date (which is further support for the big bang theory); showing us that although the RCF is very homogeneous, fortunately it is not absolutely homogeneous, as there are small irregularities in its isotropy or distribution of the subject-energy in space.
Distribution of the cosmic background radiation in the universe according to the COBE probe.
Distribution of the cosmic background radiation in the universe 380 000 years after the Big Bang, according to the WMAP probe. The brightest spots, representing areas where the radiation had the most energy, are the 'seeds' of galactic clusters and superclusters. (Image: NASA/WMAP Science Team)
WMAP has been able to determine that when the universe was 380,000 years old, there were some places where the temperature of the cosmic background radiation was 2.7251 Degrees Kelvin (i.e. just over 2.7° above absolute zero, which is -273° Celsius or 0° Kelvin); while in other places the radiation had a temperature of 2.7249° K. As can be seen, this is a difference of millionths of Degree, but it is large enough to be able to determine the presence of anisotropies or irregularities in the spatial distribution of the cosmic background radiation. It is thanks to these inhomogeneities that we can be here today living our lives. The areas of spacetime with the highest temperature would be precisely the seeds that would give rise to the first stars. However, on a large scale, the cosmic background radiation is very homogeneous, even in the infancy of the universe, which is consistent with the inflationary state theory, postulated in the 1980s by Alan Guth and Andrei Linde, according to which immediately after the big bang the acceleration with which the universe was expanding suddenly increased and it entered a phase of accelerated expansion, after which it re-entered a phase of "normal" expansion.
The RCF is a fossil remnant of the big bang with which we assume the universe began. It was predicted theoretically by George Gamow and discovered in nature in 1964, quite by chance, by engineers Arno Penzias and Robert Wilson. The RCF was first photographed in 1992 by the COBE satellite.
A millionth of a second after the big explosion, the first material particles and antiparticles formed and annihilated each other. On this aspect, it is worth commenting, albeit very briefly, since its detailed study would take us too far away from topic , that it is still a real mystery for cosmologists why there is subject instead of antimatter in the universe; in fact, "the existence of subject is an unfinished chapter of the big bang theory of the origin of the universe, which otherwise explains almost everything we observe".12. A few seconds later the temperature dropped to about three billion Degrees and the radiation energy lost the ability to create particle pairs of subject and antimatter in significant quantity.
We have already said that when a homologous pair of subject and antimatter particles meet, they annihilate each other by releasing energy. Such annihilations left photons (the particles that carry light, also called electromagnetic interaction quanta) as the most numerous particles; the universe was in the era of radiation. Photons, neutrons and protons kept colliding with each other as the universe expanded and cooled. In theory subject and antimatter should have destroyed each other, but something from subject prevailed over antimatter. The existence of inhomogeneities is a good test proof of this. But this is precisely one of the big questions of cosmology today: to explain why the subject prevailed over the antimatter.13. The Greatest Unification Theories (GUT's) propose that there must have been a violation of charge-parity symmetry (CP-violation), two quasi-symmetric properties of particles. Still, the question remains core topic : How could such a CP-violation occur?
Three minutes after the big bang the temperature of the universe, of its "cosmic soup", dropped to one billion Degrees, the same temperature that can be found in the core of many stars today. In these circumstances the numerous collisions of photons with protons and neutrons could no longer prevent the latter from occasionally coming together to form the nuclei of future atoms. But photons still had the ability to prevent electrons from binding to nuclei formed by protons and neutrons, called nucleons because they are the particles that form the nuclei of atoms. However, for thousands of years atoms could not form because radiation dominated over subject.
Now, some 300,000 years after the big bang, the temperature had dropped to 3,000 Degrees. Long before that date, the temperature had dropped so low that photons could no longer prevent the bonding between electrons and atomic nuclei, and the first atoms of hydrogen, helium, deuterium, etc. could begin to form. Around this time, subject and radiation separated and radiation began to dominate the evolution of the universe. It is said that the universe then became transparent, as photons could travel without colliding with any particles from subject. Thus, from that moment on, radiation no longer collided with subject and began to travel along with it throughout the evolution of the universe. So, the cosmic background radiation is nothing more than the photons that were free to travel through the universe some 300,000 years after the big bang, and which we capture today with satellites like WAMP, COBE or BOOMERANG and MAXIMA, at the time, and in a few years' time with the European Planck probe.
6. The subject and dark energy
The data confirmed by WMAP seem to confirm that the universe is made up of 4% ordinary baryonic subject (the atoms and subatomic particles that form natural bodies such as stars or human beings); 23% dark matter (cold and hot, although the latter is losing prominence in current cosmology leaving the field clear for the Cool Dark Matter (CDM), an entity that is not known exactly what it is, although it is assumed that it must be formed by heavy elements of baryonic subject as MACHOS (massive astrophysical compact halo objects; in : massive astrophysical compact halo objects; in : massive astrophysical compact halo objects; in : massive astrophysical compact halo objects; in subject : massive astrophysical compact halo objects; in : massive astrophysical compact halo objects; in : massive astrophysical compact halo objects; in : massive astrophysical compact halo objects): massive astrophysical compact halo objects; at Spanish: OHCM, i.e. massive compact halo objects), such as black holes or brown dwarfs; or exotic particles such as neutrinos, hypothetical axions, photinos or WIMPs (weakly interacting massive particles). The remaining 73% must be made up of an exotic form of energy: the energy dark energy, a mysterious vacuum energy associated with the vacuum.14a mysterious vacuum energy associated with spacetime, considered to be one of its properties, with the ability to dilate or expand spacetime, causing galaxies to move away from each other, like a series of dots drawn on the surface of a balloon as it swells. According to this, the escape velocity of galaxies would exceed the recession velocity due to gravitational attraction, so that the expansion of the universe would be indefinite; ending its existence in thermal death. The universe would irrevocably cool down. Space would expand more and more and the universe would become a cold and dark place.
However, it has to be confirmed that the amount of subject in the universe does not exceed a certain critical mass density that would cause the expansion to stop and an implosion process to start. The latter, although not what is currently believed to happen, since the repulsive energy is positive, i.e. it exists and acts, cannot be definitively ruled out until we know the exact role played by the dark subject , since we do not yet know what it consists of, nor what its physical properties are. When we know what the properties and behaviour of the dark subject are, we will be able to better predict the evolution of the universe. The same applies to dark energy, which seems to be clearly beating gravity, expanding the universe indefinitely.
7. Planck. The third generation satellite
If COBE was the first major step in the study and measurement of the fluctuations of the Cosmic Microwave Background and WMAP is the present, the European Space Agency's Planck probe is the more immediate future. This is mission statement , which has been programmed by the European Space Agency (ESA) for several years and will be launched into space in 2007, if there are no delays. The main purpose of this mission statement is to map the temperature fluctuations of the Microwave Background Radiation over the entire sky.
The Planck satellite is the result of the combination of two projects: SAMBA (Satellite for Measurament of Background Anisotropies) and COBRAS (Cosmic Backgroun Radiation Anisotropy Satellite). After being selected, the two projects were merged into a single project named Planck in honour of the famous German scientist who laid the theoretical foundations of quantum mechanics and the study of blackbody radiation. The Cosmic Microwave Background emits radiation with the characteristics of a black body. If we compare the emission graph of the CMB radiation and the one that the theory predicts for a black body, they coincide completely, something that supports the big bang hypothesis, since this theory predicts the existence of that subject of microwave radiation.
The Planck probe will be sent into space to make even more accurate measurements of the Cosmic Background Radiation than WMAP has made. Planck has a wider frequency range than WMAP, as well as superior angular perception (an ability to determine images), so Planck's measurements should far exceed those of WMAP. If nothing goes wrong, Planck's information about the universe in its infancy, when the radiation separated from the subject, the measurement of the temperature of the Cosmic Background Radiation, the study of the training of the first Structures, the possible geometry of the universe, and other questions, should be much more complete and precise than that provided so far by any other probe, including WMAP.
The project Planck was accepted just a couple of weeks after NASA approved the project WMAP. This might have seemed to establish a strong skill between the two agencies, but this was not the case. Planck is a much more ambitious and expensive project than WMAP. It is a more powerful project ; in fact, one of the reasons NASA selected WMAP was because of its simplicity and immediacy, i.e. its simplicity and speed of implementation. It was an inexpensive and quick to implement mission statement . Although it suffered several delays, it was implemented fairly quickly; Planck, on the other hand, has taken much longer to come to fruition because it is a much more complicated mission statement with many technological problems that have had to be progressively overcome. One example of these difficulties is the active cooling of the detectors of the scientific instruments carried by the spacecraft. These detectors, being extremely sensitive, need to operate at much lower temperatures than those of WMAP. In fact, the complexity of the mission statement Planck can also be gauged by the length of time it has been in preparation: it was first considered in the early 1990s.
Another fundamental difference between WMAP and Planck is that the former project needs to use data from other experiments in order to obtain important cosmological information, something that generates some uncertainty, since they are experiments carried out in other contexts, with other frequencies, and an extrapolation of their results must be made. Planck, on the other hand, is designed in such a way that it alone can obtain the information that is being sought with this experiment, so that no extrapolations have to be made from other experiments data. The two projects are therefore not comparable, except in the object of research: the Cosmic Background Radiation.
Beyond Planck, the European Space Agency is already preparing new missions. At the moment they are only in the initial phase of design as ESA's firm schedule only goes up to 2010. The next decade is just starting to be planned now and is still in a very embryonic phase. Something similar is happening at NASA. They are preparing the Einstein probes: these are long-term projects deadline within a single programme. One of these probes is mission statement to study the Microwave Background Radiation, specifically its polarisation. It is expected to provide interesting information related to the possible inflation that the universe may have undergone shortly after the big bang. The Planck probe will also measure the polarisation of the RCF, but it is not known at what level it will do so, although it is optimistic that it will do so thoroughly. However, ESA is also interested in a specific mission statement to determine the polarisation of the RCF, although these are still only ideas that have not yet been realised. Of course, the budgetary constraints faced by the space agencies could lead them to collaborate on a joint mission statement in this field.
8. Cosmology and ideology
From an ideological point of view, it is interesting to note that there are still those who try to resurrect the old big crunch theory, according to which the universe would not need a Creator since it would be eternal, since it would be in a continuous process of expansion and implosion. A resurrection that would, however, incorporate the new discoveries relating to dark energy and dark subject , as well as the latest version of the theory of inflation. In this line goes the proposal of Paul J. Steinhardt, of Princeton University, and Neil Turok, of Cambridge University, who in their work: A Cyclic Model of the Universe15They claim that time has no beginning and no end, but an infinite series of loops of expansion and contraction.
Despite the great achievements being made in the field of cosmology, we still do not know exactly how the universe originated. Furthermore, the physics of the first instants of existence of subject and energy remain unknown to us. A theory of quantum gravity (which would explain what happened between t=0 and the Planck time, t=10 raised to -43 seconds) that is sufficiently convincing to achieve a minimum of consensus among the academic community has not yet been achieved. In this respect, the words of the famous cosmologist Martin Rees serve as an example: "It is necessary to distinguish between what happened in the first moments of the first second of the universe and the rest of cosmic evolution. The data at our disposal allow us to describe the history of the universe from second one to the present (...) In the course of the first second, on the other hand, the laws of physics currently in force lose their meaning, the hypotheses cease to be verifiable and we enter the realm of speculation (...) We have no proof of what might have happened in the first instants of second one. The hypothesis of the initial explosion - i.e. of a zero instant of infinite energy - is an extrapolation of the laws of physics to a status where these laws no longer apply. It is therefore perfectly likely that the extrapolation is incorrect and that the big bang never occurred."16.
(1) "The calculation of the expansion rate of the universe (expressed by the Hubble constant) has more than once given cosmologists a hard time. It has suggested that the universe is younger than some stars in our galaxy!" (Joseph Silk: Birth and History of the Universe; in Scientific World: The Birth of the Cosmos; p. 9).
(2) Named after the famous Greek astronomer who, together with Apollonius, proposed, between the 3rd and 2nd century BC, the system of epicycles and eccentric spheres which was later popularised by Claudius Ptolemy, with the aim of replacing the system of homocentric spheres. Roughly speaking, the astronomical model of these characters lasted until the Copernican revolution of the 16th century ..... Almost eighteen centuries!
(3) Michel Froeschlé: Hipparcos retouches the age of the universe; Scientific World, no. 182, September 1997; p. 716.
(4) One megaparsec is equivalent to a distance of one million parsecs, i.e. 3.3 million light years. One kiloparsec equals one thousand parsecs, i.e. 3.3 thousand light years. So one parsec is 3.3 light years.
(5) Cf. Gilles Theureau: The Universe Finally Reveals Its Age; Scientific World Extra: The Birth of the Cosmos, pp. 70-74.
(6) Cepheids are stars of variable luminosity. As there is a relationship between their absolute luminosity and their period, by measuring the period of a Cepheid and its apparent brightness, its distance can be determined.
(7) F. Ducci Macchetto and Mark Dickinson: The Galaxies of the Young Universe; research and Science, July 1997, p. 56.
(8) Wendy Freedman: The Hubble Constant and the Expanding Universe; research and Science, June 2004, no. 333, p 45.
(9) Ibidem, p. 42.
(10) Richard B. Larson and Volker Bromm: Primordial Stars; research and Science, February 2002, p. 52.
(11) Wayne Hu and Martin White: The Cosmic Symphony; research and Science, no. 331, April 2004, p. 48.
(12) James M. Cline: The Origin of subject; research and Science, no. 345, June 2005, p. 48. The author of this article adds that: "For a cosmologist, the existence of subject is puzzling, a problem that has not been solved since theoretical physics had to consider it almost forty years ago". Ibid.
(13) Cf. Helen R. Quin and Michael S. Witherell: Asymmetry between subject and antimatter; research and Science, No. 267, December 1998; pp. 42-47.
(14) Cf. Carlos A. Marmelada: El misterio de la energía oscura; Aceprensa Service 101/04, 21 July 2004.
(15) Science, Vol. 296, pp. 1436-1439; 24 May 2002.
(16) La Vanguardia, interview with Martín Ree; Science and Technology supplement, Saturday 7 November 1992, p. 11.
- Aceprensa, services 79/95 (Mariano Artigas,"Georges Lemaître, el padre del Big Bang"), 154/00 (Carlos A. Marmelada, "Teorías sobre el Big Bang, con Dios al fondo") and 103/01 (Carlos A. Marmelada, "¿Qué había antes del Big Bang?"). These services are available on Aceprensa's CD-ROM.
- There is ample informative information on the subjects dealt with in this article in a monographic issue of IAC Noticias (special 2002), magazine of the high school de Astrofísica de Canarias, graduate "subject oscura y energía oscura en el Universo". It can be accessed from the web page of the high school de Astrofísica de Canarias (PDF document, 1.540 Kb).
- On the RCF: J.L. Sanz and E. Martínez-González, "Radiación cósmica de fondo de microondas", research y Ciencia (April 1993). The journal, the Spanish edition of Scientific American, is available for a fee from Investigacion y ciencia.
- On the training of the first stars, see: Ron Cowen, "Galaxy Hunters. In Search of the Cosmic Dawn", National Geographic (February 2003); Richard B. Larson and Volker Bromm, "Primordial Stars", research and Science (February 2002).
- On the dark subject : Mordehai Milgrom, "Does the dark subject really exist?", research and Science (October 2002).
- On dark energy: Lawrence M. Krauss: "Cosmological Antigravity", research and Science (March 1999).