On last 8 October, the Royal Swedish Academy of Sciences announced the winners of the Nobel Prize in Physics “for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos” (see HERE). It was awarded to James Peebles “for theoretical discoveries in physical cosmology”, shared with Michel Mayor and Didier Queloz “for the discovery of an exoplanet orbiting a solar-type star”.
The first impression is of some surprise because—being in both cases scientists with ample merit— this acknowledgment seems late in coming. In saying that, we have the recent case of Peter Higgs, who had to wait half a century to achieve recognition for his theory on the boson that bears his name (Higgs boson) and which was crucial to validate the Standard Model of Particle Physics. Apparently, the latter case was pending verification of the actual existence of the particle. In both of the present cases, however, things are very different.
James Peebles is a scientist whose most important contributions took place in the 1970s and 1980s, and who had widespread international recognition. Today, he is 84 years old. Mayor and Queloz’s achievement is relative to their discovery in 1995 of the first known exoplanet. The recognition of the scientific community was immediate and the best proof of their success has been the subsequent explosion of research in this field, which has led to the discovery of many other exoplanets. Thus, it gives the impression that the Academy has looked back and awarded the prize to something that had been left behind along the way.
The achievements of James Peebles
In 1931, in a little-known letter addressed to the journal Nature, Georges Lemaître introduced the bold hypothesis that the whole universe had originated a finite time ago from a “primeval atom” (see HERE).
The development of this idea through the contributions of different scientists—among them James Peebles himself—led us to the knowledge of the genesis and evolution of the Universe through the model known as the Big Bang.
The Universe came into being 13,500 million years ago as a tremendously hot and energetic point. The first physically meaningful unit of time relates to Planck time (10-43 s), which is the minimum value that calculations allow. It corresponds to a temperature of 1032 K and the size of a sphere 1.6 x 10-33 cm in diameter.
The history of the Universe is a thermal one. As it expanded and cooled, the conditions for the gradual transition from one stage to the next occurred. After only 10-35 s—and for a spectacularly short time (1034 s)—the Universe endured an expansion (1060) comparable to what an object would undergo from a size smaller than a proton to the size of a galaxy. This growth occurred at an enormous rate, millions of times faster than the speed of light. In the final stage of the inflation process, all the matter in the Universe was created, so that at time 10-10 s, the cosmos was composed of a dense plasma mixture of radiation and particles.
In modern particle colliders, phenomena can be tested up to energies of the order of 1 TeV. This means that our physical image of the evolution of the Universe is reliable since the expanded plasma had that kind of energy, i.e. at 10-10 s of the existence of the universe.
At around three minutes of existence, the protons and neutrons had cooled down sufficiently so that bound systems could be formed from them, resulting in the appearance of the lighter elements of the periodic table, leaving a balance of 75% hydrogen nuclei (protons) and 25% helium nuclei. At the beginning of his career, James Peebles devoted himself to understanding this stage, known as “nucleosynthesis”.
When it reached 300,000 years, the Universe had cooled enough for neutral atoms to survive; radiation could move throughout the Universe with little chance of being absorbed, and it became clear, bright. The radiation emitted at that time—known as cosmic microwave background, since it reaches us today cooled to 2.3 K—is the one that gives us information on the early universe and allows its study. The prediction of the existence of this radiation, discovered by chance in 1964, is one of Peebles’s major achievements.
After a billion years, gravity caused the hydrogen and helium to clump together to form giant clouds that would become galaxies; smaller masses of gas were compressed to form the first stars. The formation of structures has also been one of the research areas in which Peebles has been prominent. Inside these hydrogen masses, the pressure and temperature increase until nuclear reactions occur with the release of heat. The temperature rises and the stars begin to shine.
In the first generation of stars, there were no heavy elements. These were formed in the nuclear reactions produced inside them. The most massive stars ended their lives due to the explosion caused by the pressure of gravity against the inside, where energy is produced by nuclear reactions. The materials scattered by the explosion became part of the interstellar material that eventually clumped together again to form new stars. As the stellar generations followed one another, the cosmos became more enriched with heavy elements.
Around 9,500 million years later, and after many generations of stars had formed and disappeared, our Sun formed, and, after a few thousand years, the Earth and other planets.
Another field in which Peebles was a pioneer was the study of dark matter, whose composition continues to be an enigma for science. As we have seen, his initiative led him to undertake very different lines of research work, which prompted Ann Finkbeiner to say in 1992 that: “Peebles is famous in his field because for a long time the field has tracked the direction of his work” (see more).
Importance of Mayor and Queloz’s discovery
The importance of the discovery of the first exoplanet is framed within the search for an explanation for the appearance of life on our planet. The emergence of life on Earth and its evolution in early periods includes gaps and unknowns that research into life on the outside could help to resolve. Our own lives may not have started on Earth, but elsewhere in the universe. But this discovery also ties in with the curiosity that humanity has always had regarding the possibility of the existence of other worlds and the presence of life on them. More than 2000 years ago, Epicurus argued the existence of other “worlds” based on an infinite expansion of the Universe. More recently, our ancestors dreamed of the discovery of selenites, the hypothetical inhabitants of the Moon. In 1820, the mathematician Karl Gauss proposed the construction of giant geometric patterns on the surface of the Earth by planting trees, so that they could be seen by these beings. The advance of scientific knowledge has ruled out the likelihood of intelligent life on the Moon, Mars and the rest of our solar system, although the possibility of organisms with a simple structure has not been discarded.
Hopes of finding life, even evolved, are focused on the vastness of the spaces outside our solar system, particularly on planets that have conditions similar to our own.
For this reason, the detection—announced on 6 October 1995 by Michel Mayor and Didier Queloz—of the planet Dimidio (51 Peg b) orbiting the Sun-like star Helvetios (51 Pegasi) spurred the rapid development of this new cosmological research line.
Using the backward and forwards motion of the star 51 Pegasi (radial velocity), they discovered an alteration that could only be explained by the presence of a planetary companion. The idea was developed some time ago but lacked a spectrograph with sufficient precision to measure those weak signals.
The path initiated by Mayor and Queloz has helped to increase our knowledge, while revealing new mysteries, broadening the scope of what we do not know. The first surprise comes from 51 Peg, the award-winning discovery because the object orbiting it is a gas planet somewhat larger than Jupiter, but in an orbit 20 times smaller than Mercury’s, with an orbital period of 4.23 days. Until then, it was thought that such a system was not possible for reasons of stability.
In 2009, the Kepler satellite was launched into orbit, able to observe 155,000 stars at 30-minute intervals for three years. During its useful life, it identified 3,564 planets. Last year saw the launch of the TESS satellite, which aims to analyze seven million stars and discover around 20,000 new planets. The study of the existence and analysis of atmospheres on exoplanets has also begun. In 2017, scientists announced the detection of the first exoplanet similar to Earth in size and with the presence of atmosphere, albeit with a surface temperature of 370°C, which is located 39 light-years away.
From what has been observed so far, it can be inferred that, in the Universe, diversity seems to be the rule, and that finding the conditions of our planetary system and the Earth in order to allow evolved life is more difficult than expected.
Scientists express their views
By chance, the announcement of the Nobel Prize occurred when one of the winners, Michel Mayor, was visiting Spain. Consequently, the main Spanish media rushed to interview him. In response to the most popular question about the existence of life, which actually refers to complex life, he alluded to the difference of opinion between physicists and biologists. Indeed, in the vastness of the Universe, we expect to find planets with conditions similar to ours, but biologists also recognize the very tiny probability of finding complex life even with the proper atmospheric conditions to support it. It is an equation that has no mathematical solution since we are starting from a single reality and therefore it cannot be extrapolated as a statistical fact. The answer could only be: “You may have your own impression, but that’s not science” (see HERE).
More disconcerting is the answer that one of the media highlighted in the headlines: “There is no room for God in the Universe”, emulating the famous phrase of Laplace: “I had no need of that hypothesis” when he was asked about the intervention of God in the cosmos. Laplace believed in an eternal Universe and hence his response. The same statement was included not many years ago by Hawking and Mlodinov in their book The Grand Design, causing a great stir. In that case, it was proposed that the Universe was “created” from “nothing” through a vacuum fluctuation (see more), which amounts to a false creation. The vacuum defined by science is not a space containing nothing, a “real vacuum”; rather, the vacuum contains a gravitational field, a sea of virtual particles, fluctuations of space-time, etc. Thus, the “spontaneous creation” spoken of is not a true creation, but only a mutation. Mayor does not explain his statement in the interview; he associates it with the idea that life is a natural process. Certainly, the evolution of the whole Universe is a natural process. It is the outcome of the laws that govern it and does not preclude the existence of God, but quite the opposite.
In the face of these claims, it is more reliable to follow the criterion of James Peebles: “Our universe may be viewed in many lights: by mystics, theologians, philosophers or scientists. In science we adopt the plodding route: we accept only what is tested by experiment or observation”.
What science says is that the Universe had a beginning, as indicated by the Big Bang model. Furthermore, Bodes, Vilenkin, and Guth have shown that any expanding universe model (as are the multiverse or cyclical universe models) necessarily has a beginning in time (see HERE). This premise allows philosophy to provide a decisive argument for the existence of a Creator.
Bioethics Observatory – Institute of Life Sciences
Catholic University of Valencia