Guia Covid-19
Imprimir Republish

physics

Goodbye, Certainty

The variation in the value of the alpha constant - now no longer constant - rocks established concepts about the Universe and the origin of life on Earth

ESOUniformity has been broken: in other times, billions of galaxy stars, such as the NGC 1232, could have followed physics laws different from those of todayESO

Perhaps physicists have already become used to, from time to time, reviewing their concepts on the Universe. They suffered a setback with Quantum Mechanics at the beginning of the twentieth century because of the uncertainty principle, an essential ingredient of atomic particles, which were then before apparently predictable. At the end of August they took another hit: research presented in one of the most prestigious scientific publications, Physical Review Letters, demonstrates a variation of the so-called alpha constant, one of the fundamental values in the Universe, which regulates the intensity with which atomic particles interact among themselves and with light.

Six billion years ago, the value of alpha might have been slightly less, in the order of one part in one hundred thousand – only the final digit of a number with five decimal places after the zero. A minimal variation, but enough to indicate that the constant is no longer a constant. The result – seen as one of the major scientific discoveries of the past fifty years – confirms the preliminary measurements obtained by the researchers from Australia, England and the United States, who sign the article. They analyzed light emitted by quasars – stars similar to the nuclei of galaxies, situated some 8 to 10 billion light years away from the Earth – detected by the telescopes at the Keck Observatory in Hawaii.

Weeks afterwards, they already have a more clear idea of the implications of the alpha variation, also called fine structure constant. Firstly, one of the pillars upon which modern science is built, has been destroyed: the temporal uniformity of the Universe, which might have followed other laws, as yet unknown. The results obtained by the team led by John Webb, of the University of New South Wales in Australia, suggests a redesigning of the image of the atom, in which the electrons move about in orbits greater than those thought of today.

As a consequence, there might be other chemistry and physics rules for the formation of molecules – and therefore, of living organisms. In the extreme case, far-fetched idea: if the alpha were twice as large or twice as small, life on the Earth or the formation of the galaxies would become impractical, in accordance with the current theoretical models.

More changes?
The value of the alpha, equivalent to the number 1 divided by 137.04, is associated with another constant, the electrical charge – identified as e – , responsible for the attraction or repulsion between the electrons, atomic particles of negative charge, and the protons, positively charged. The variation of the alpha is worrying because it implies changes in our fundamental values on which Physics is molded.

Nevertheless, this perturbing idea is going to give sustenance to the conjectures of the English physicist Paul Adrien Maurice Dirac (1902-1984, Nobel Physics Prize winner of 1933). Dirac compared two forces acting on the same proton, the electrical force and the gravitational force. The intensity of the electrical force is determined by the electrical charge (e) and that of the gravitational force by the gravitational constant of Newton (G).

Impractical planet
Dirac noted that the electrical force was much greater than the gravitational force: equivalent to the number 1 followed by 36 zeros. In search of an explanation for this value, that seemed too high to him, he postulated that at some moment in the history of the Universe the difference between the constants e and G were not so large – or even that they had been equal. According to Dirac, the value of G could vary inversely with time – and therefore it would be lower today.

The scenario which is born from this reasoning is nebulous. If the force of gravity had been greater, the orbits of the planets would have been smaller: the earth would have been closer to the Sun, a smaller and more luminous star. Consequently, on the Earth of 500 million years ago, there would have been “bubbling oceans, making life uncomfortable for the trilobites”, the first more complex organisms of the planet – in accordance with the scenario imagined by the Hungarian physicist Edward Teller, one of the scientists involved in the Manhattan Project, which resulted in the atomic bomb.

A less strange alternative was formulated by the Russian physicist George Gamow (1904-1968), one of the authors of the Big Bang Theory: the electrical charge is the one that could have varied with the age of the universe – today established at 13.9 billion years, though there are supernovas that could be older. Gamow’s proposal brings up other questions. In the opinion of Rogério Rosenfeld, a professor at the Theoretical Physics Institute of the São Paulo State University (Unesp), the reduction in the value of the electrical force would lead to an even smaller difference between the masses of the proton and of the neutron, the particles which make up the atomic nucleus – today, the neutron is just slightly heavier (0.1 to 0.2%) than the proton.

It would be enough, nonetheless, to make an influence in the formation of the more simple chemical elements during the first three minutes of the Universe after the Big Bang. For example, there would be less helium than predicted. “Alterations in the Laws of Physics are always possible, but all of the implications must be analyzed with caution” says Rosenfeld.

Re-opened theory
At the least, the strong nuclear interaction, which controls the organization of the atomic nucleus, must have remained stable over the last two billion years. This is what was indicated by the measurements done during the 70’s by Russian researchers in a uranium mine in Uklo, in Gabon. “Our vision of the Universe depends a lot on these numbers”, comments Élcio Abdalla, of the Physics of the University of São Paulo. Besides the alpha constant, one does no know what else could have changed, since the result announced in the Physical Review is based on cosmological observations, in which it is not possible to separate the effect of one constant on another, reminds Carlos Escobar, a researcher with the Physics Institute of the São Paulo State University (Unicamp).

The next few years will possibly indicate which theories or concepts will come out scratched and torn or strengthened. Yet apparently the results of the new idea reaffirm the proposals of the Strings Theory, a way of perceiving atomic interactions through imaginary entities, the chords, which give origin to atomic particles – the strings would be like a bus in which the passengers get off in accordance with chance or their own desire. Formulated in the 70’s by the English physicist John Schwartz, currently at the California Institute of Technology (Caltech), in the United States, the model was perfected in the decade of the 80’s by another Englishman, Michael Green, of Cambridge University, and more recently by the North American Edward Witten, also of Caltech.

Abdalla, from USP, was one step away from dumping the Strings Theory (or Superstrings). This theoretical tool seemed to be useful to provide an explanation for the origin and the working of black holes, one of his study focuses, but it got stuck because of the difficulty of experimental proof. The article in the Physical Review made him reconsider, as it indicates that the strings model harmoniously harbors the elements that come from the work of the Australian researchers. This is the case with the possibility of the existence of atomic particles much smaller than the electrons and as yet not experimentally proven, and of other space dimensions, as yet not well explained by the theories in current use.

Bends in the tube
Other dimensions? “It is as if we were living in a pipe and the other dimensions were bends or branches of this pipe, which we cannot see”, compares Abdalla. He believes that both particles and folds in space, in order to be understood, require a dive into the essence of material such as that made possible by the Australian study. “Let’s now work to see if the ideas bloom”, he suggests.

If they bear fruit, the String Theory could carry out an old desire: to bring together two visions of physics as yet incompatible: General Relativity Theory and Quantum Mechanics, which forecasts the existence of new elementary material particles and suggests another way of understanding time. Incompatible to classical theory, there is no dialogue between them and there is divergence even in principles. However, in the Strings Theory, Relativity fits in with the principles of Quantum Mechanics and there is string behavior on certain occasions that can be explained according with one theory and others times with the other. “These two theories cannot continue without communicating between themselves”, observes Escobar, of Unicamp.

The coming together of the two concepts of the Universe, even though they explain the variation of the alpha constant, will imply other conceptual earthquakes. For Abdalla the greatest impact will be in the way of seeing the Big Bang, which will quit only being an explosion that originated the Universe and beyond which Relativity cannot advance, to turn itself into part of a wider story – a story which, in according to the proposals of the English physicist Martin Rees, from Cambridge University in his book Just Six Numbers, published at the end of last year, will even include other universes.

Republish