Energy is governed by the laws of thermodynamics, and is therefore not created or destroyed, merely transformed. Total energy is unvarying and originated with the birth of the Cosmos. Modern science now knows that fluctuations in the quantum vacuum gave rise to the great primordial explosion (humorously termed “the Big Bang” by Fred Hoyle).
The Book of Genesis tells us that “In the beginning the earth was without form and void, and darkness was over the face of the deep… Then there was light, and [God] separated the light from the darkness”. Both narratives have something in common. We don’t know why or how it happened, but that’s the way the Cosmos was born.
It is curious that in spite of the thousands of years that have elapsed between the Book of Genesis and modern physics, we are still unable to come up with a definitive explanation of these matters. The 20th century was a time of widespread scientific optimism, essentially thanks to the advances in the field of industrial mechanics and electricity (application of steam engines and industrial processes). Lord Kelvin, one of the leading physicists of the day, stated in 1904 that the field of physics was already perfectly delimited and that the only thing remaining to do was to improve the measuring methods. However by that time Max Planck had formulated his hypothesis on black-body radiation, which subsequently led to the development of quantum mechanics; and in 1905, Einstein published his theory of special relativity. Both these findings turned the world of physics on its head.
In fact in the early 20th century, the foundations were laid for two different and complementary types of physics which have so far proved impossible to combine: relativity or the physics of the extremely large (macrocosms); and quantum mechanics, or the physics of the extremely small (microcosms). Both have enabled a giant leap forward in explaining the world in we live in, although they have also raised a number of new questions. Lord Kelvin’s remark today looks arrogant and vain.
We still do not know the exact mechanism that led from the quantum vacuum to the primordial explosion. What is true and proven is that the cosmos, once created, has been rapidly expanding, propelling the galaxies away from each other through the effect of a type of anti-gravity, or “dark energy” of unknown origin. The primitive universe was extraordinarily hot, but as it gradually expanded and cooled, space became filled with clouds of gas, basically hydrogen –the simplest chemical element (a single positively-charged proton and a negatively-charged electron). However the gas did not spread through space in an entirely uniform way, and the effect of gravity began concentrating around particular nuclei, thereby giving rise to future stars and galaxies. Gravity is the weakest of the four forces of nature (gravity, electro-magnetism, strong nuclear force and weak nuclear force), but its effects are implacable.
The concentration and density of the hydrogen continued increasing without interruption until the nucleus was subjected to sufficient pressure (and thus temperature) to trigger a fusion process in the hydrogen and its transformation into helium (the principle on which the H-bomb is based). When the hydrogen ran out and the pressure and temperature rose even further, the helium began its own fusion, transforming itself into carbon and oxygen. The fusion process, if the mass is sufficiently large, continues through several stages until it creates iron. Iron is not susceptible to ulterior processes of nuclear fusion. The nucleus then shrinks due to the effects of gravity, the outer layers lose their support, and the star explodes in the form of a supernova. Supernovas are the origin of all the other chemical elements up to iron. Our planet is the result of materials from the explosions of various supernovas.
Under the pressure of gravity, a star in whose nucleus the processes of thermonuclear fusion have finished “dies out” and is transformed into a white dwarf, a neutron star or a black hole, depending on the size of the mass of the original star. The maximum critical frontier for producing a white dwarf seems to be about eight times the mass of our sun. Above this mass, a neutron star or a black hole is produced. Our sun will one day be transformed into a white dwarf, after undergoing a transitional stage as a red giant which will burn up the inner planets in our solar system, including our own.
White dwarfs and neutron stars are dead stars formed by degenerate matter. The first is made up of a plasma composed of rapid protons and electrons, and the second exclusively of neutrons. Both categories have an extremely high density and can be detected mainly by their gravitational effect on the surrounding mass. Black holes are genuine cosmic monsters that devour everything around them and from which –thanks to their powerful gravitational force– not even light can escape. Among other possible places, there is thought to be a black hole at the center of every spiral galaxy such as our Milky Way.
What happens to the mass swallowed up by the black holes? We don’t know. Does it reappear when the black hole “evaporates” due to the effect of what is known as Hawking’s radiation? Is it transferred to a parallel universe to our own? Is this the path by which matter is transformed integrally into energy? Nobody knows. There are many questions but no answers.
It is well-known that matter is composed of atoms, and that these are formed by protons, neutrons and electrons. Protons and neutrons form the nucleus of the atom. Around them the electrons move at a distance of tens of thousands of times the size of the nucleus; that is to say, the atoms are almost empty. This is the space that is occupied under the enormous pressures existing in the white dwarfs and the neutron stars mentioned earlier.
Just as electrons are simple or elementary particles, protons and neutrons are made up of smaller elements known as “quarks” that come in a variety of models which scientists have humorously named “flavors”. The most common are the “up” flavor and the “down” flavor. What’s more, each flavor comes in three different “colors”. Of course the terms “flavor” and “color” have nothing at all to do with their normal meaning. A proton is composed of two up quarks and one down quark. Neutrons, in contrast, are formed by two down quarks and one up quark. In both cases each quark must be a different color.
What is there beyond quarks? It is possible that experimental –not theoretical– physics may come up with an answer. The CERN (European Organization for Nuclear Research) particle accelerator in Geneva may provide some new information when in two years’ time it resumes its activities with twice as much power (from 7 to 14 tera-electron volts) as it had when it succeeded in discovering the famous Higgs boson in 2012. Some scientists believe that elementary particles are due to the vibration of minuscule strands of energy known as “strings”. The different frequencies of their vibration give rise to different types of particles. This could be the path by which energy is transformed into matter. For the time being this is pure theoretical speculation, and we have reached the limits of our knowledge, without shedding much light on the subject.
Physics is not a boring field governed by a dusty old set of formulas. Quite the reverse; it is a lively and modern discipline in which new generations can find ample space to exercise their intuition and imagination. But to do so we have to keep an open mind and not allow ourselves to be tied down by the routines of the past. Lord Kelvin, if he were alive today, would give anything to be young again in today’s scientific context.
Economist, Madrid (Spain)
Comments on this publication