The inflationary theory suggests that the universe sprang into existence from absolute nothingness around 15 billion years ago, starting from a particle trillions of times smaller than a proton. It also hints at the possibility that our cosmos may eventually return to an icy, barren wasteland.
The sheer enormity of the universe is truly mystifying. Constant revelations are made through the most powerful telescope – the Hubble, positioned 300 kilometers away from Earth. A multitude of galaxies housing billions of stars (with our Milky Way alone accommodating 100 billion stars), enigmatic black holes with a gravitational force so potent it devours light, celestial bodies situated at inconceivable distances, with only light's speed of 300,000 kilometers per second topping them, have all been in existence for 11 billion years. This astronomical spectacle also includes drifting asteroids and gas clouds.
The observable universe's scope is massive, yet physicist and cosmologist equations validate that what we see is just about 5% of its mass. The cosmic sphere is predominantly composed of what is referred to as dark matter, an unseen substance pervading space, and dark energy, a theory currently only corroborated by the mathematical computations of astrophysicists, based on certain phenomena within the intergalactic space.
Faced with such an intriguing spectacle, it's only natural to contemplate where it all originated. What primal force brought everything into existence? If your immediate response is the "Big Bang", it's time to update your knowledge.
The theory that the universe was born from a massive explosion, termed the Big Bang, was proposed in the early 20th century. This theory, bolstered by Edwin Hubble's 1922 discovery of galaxies drifting apart, implied that they must have originally been confined to a point of extreme density and high temperature. The ensuing explosion continues pushing the fragments into infinity. Still, this model, while broadly accepted, has its shortcomings. As physicist Alan Guth from MIT, USA, clarifies, "The Big Bang is simply the expansion from an initially dense and hot state. The theory doesn't explain what exploded, why it exploded, or what happened before the explosion."
In essence, the Big Bang theory explains the aftermath of the explosion. It presumes that all matter was already present in the universe, albeit in a highly condensed state different from its current form. But what was the source of this primordial matter? Alan Guth proposed a theory to address this, attempting to clarify what exactly detonated in the Big Bang.
Alan Guth's answer to the question, "where did the universe originate?" is simple: from nothing. The first particles are believed to have emerged from a basic vacuum fluctuation, a variation in an electric field that traditional physics doesn't accommodate, but quantum mechanics, a field of study born in the last century, does. According to this hypothesis – known as the inflationary universe theory – the original particles sprouted from nothingness and expanded at an unbelievable speed within billionths of a second, forming the mass which would later disintegrate in the massive explosion. This theory neither disputes nor supersedes the traditional Big Bang explanation; it complements it. Essentially, it provides the starting point from which the Big Bang model functions, contributing to its wide acceptance among physicists and cosmologists.
from emptiness to spacetime
“Guth's theory solves, at a single stroke, the mechanism of creation and the energy balance in the universe”, says astrophysicist Francisco Jablonski, from the National Institute for Special Research, Inpe, in São José dos Campos, SP. "It makes room for scientific and philosophical reflections." Among the hypotheses about the past and future of the cosmos under consideration in scientific circles, this is the one that best explains the data collected by telescopes and space probes in recent decades.
When he claims that the universe was born out of nothing, Guth doesn't mean that matter took shape from something that didn't exist. For a quantum physicist, emptiness is always something. It is a situation where there is no space or matter, only high frequency energy. By the laws of relativity and quantum mechanics, this energy can be converted into matter under uncertain and uncontrollable conditions, such as the sudden variation of an electric field or vacuum fluctuation. This is exactly what would have happened in the circumstance that preceded the appearance of the universe, some 15 billion years ago. In a sea of energy full of virtual particles, which preceded space and time, the first particles probably materialized through quantum tunneling, a process in which the collapse of the energy wave causes the formation of particles, of matter.
In theory, anything could emerge from a vacuum fluctuation. Calculations and experiments in particle accelerators suggest, however, that only very small subatomic units can be generated in this way and for an infinitesimal lifetime, around 10-21 seconds (a decimal point followed by 20 zeros and then 1 ). The situation is different when the matter generated is of a special type of vacuum fluctuation endowed with negative gravity, a force predicted in most theories of modern physics that, unlike normal gravitation, expels rather than attracts the particles present in its field. In this case, it would be enough to form a part of only one billionth the size of a proton (one of the nuclear particles of the atom), for the expansion of matter to start due to the internal gravitational repulsion.
In the genesis of the universe, this would have happened in the period between 10-37 seconds and 10-34 seconds, just enough time for the initial piece to reach the size of a marble. From then on, the Big Bang would have happened and the expansion would have continued at another pace.
This is the detectable zero point with the current resources of deduction and scientific experimentation, which does not mean, according to Guth, the final word on the alpha of creation or even the discarding of the hypothesis that the universe had no beginning, sustained, among others , by Albert Einstein. The idea of inflation and the concept of negative gravity have an irrevocable impact on all other cosmological hypotheses.
the matter factory
The Big Bang theory is limited to justify the estimated mass of the universe and its thermal equilibrium. It would be necessary to fine-tune the equations that demonstrate the theory, to reconcile it with what is observed today in the cosmos.” This disagreement is overcome when the inflationary model is taken into account, which, according to Reis, explains the creation of matter without contradicting the laws of physics.
Guth's theory states that, in the early universe, repulsive gravity material expanded without losing density, generating during inflation a colossal mass of quarks, tiny particles with an electrical charge less than that of an electron. At first glance, it seems that the phenomenon collides with the principle of energy conservation, which presupposes the balance of total energy in all transformations in the physical world, but that is not what happened. In the inflationary process, the positive energy of matter was balanced by the negative energy of the gravitational field, so that the total energy was always zero. When the negative gravity material began to decay, halting the rate of inflation, then the primordial soup (gas at very high temperature) was formed, considered to be the initial condition of the Big Bang.
At that time, 10-6 seconds into the cosmos's conception, there were still no atoms and molecules, just a boiling plasma made up of electrons, protons, positrons, neutrinos, and a whole range of polarized subatomic particles. Ordinary matter would only appear about 300,000 years later, when the universe had cooled down enough to allow free electrons to combine with atomic nuclei and form the hydrogen and helium that burn inside stars. It was then that dark matter circles would have helped to compress huge volumes of the two gases, promoting the formation of stars. But the stars and galaxies we see today are not the same as those back then, says cosmologist Volker Bromm of the Harvard-Smithsonian Center for Astrophysics in Cam-bridge. The first stars had enormous mass, glowed intensely, but exploded before completing 3 million years, which turned out to be fundamental for the continuation of creation.
When they exploded, these stars propelled the condensed gas around them into space, in addition to scattering atoms heavier than those of hydrogen and helium, enabling the birth of the second generation of stars. The first galaxies ended up colliding and merging into large clusters of stars.
Martin Rees believes that without this interruption in the chain of creation, the cosmos would not have consolidated in its current form, nor would there be the necessary conditions for life. If all the initial gas had remained inside the first stars, the raw material of the celestial bodies would have been consumed and today the universe would exhibit a set of red stars, gathered in dwarf galaxies. Agglomerations like the Milky Way, rich in gas, would be exceptions to the rule.
In the bowels of nature, Rees says, this difference in favor of life happened with surprising precision. For example: in the combustion process of stars, when hydrogen and helium fuse, only 0.007 of the helium's mass is transformed into energy – and it is exactly this number, according to Rees, that guarantees the chemistry of life. If it were a little smaller - 0.006 - the two protons and two neutrons that make up the nucleus of the helium atom would not join and the universe would have only hydrogen. If the number were higher (0.008), the fusion would be so fast that no hydrogen atom would have survived an event like the Big Bang. Therefore, the existence of solar systems and living beings would be made impossible by the absence of one or another element.
permanent creation
The inflationary model raised lessons that go beyond the traditional concept of the cosmos and reinforce unconventional theories developed from the 1930s onwards. One of them is that of parallel universes or pocket universes, which would operate in other dimensions of space and time, being, therefore, invisible to our eyes and to current electronic sensors. “Such parallel universes would be the result of topological defects due to the diversity of electric field variations and inflation levels in the first moments of the cosmos”, says Reis. Their number would be enormous, but it becomes even greater when considering the possibility of the eternal inflation of matter. In this case, according to Guth, the repulsive gravity material would continue to grow without limit and without end, producing more matter, in an infinite succession of universes.
The history of the cosmos in this scenario would have numerous versions, as physicist Richard Feynman proposes, and may not have started with our own universe. Some even admit that the Big Bang may have been caused by the collision of two universes.
The accelerated expansion casts a bleak picture for the distant future, when galaxies are lost in a dusty and frigid space, with a temperature much lower than the current minus 273 degrees of space. Of the billions of galaxies observable today, only two will remain visible from Earth: our Milky Way and Andromeda, the only one moving towards us.
a theory of everything
There are dozens of theories designed to explain the origin and dynamics of the cosmos, and with each discovery of astronomical observatories, many gain new versions. Guth's own inflationary model derives from earlier deductions, such as those of Russian-American physicist Andrei Linde of Stanford University, who in the 1980s conceived of the existence of different quantum fields in the universe before the Big Bang. The second half of the 20th century, however, was marked by the effort of physicists and cosmologists to arrive at a unified theory that would bring together valid elements from different models and clarify the enigmas of the universe.
One of the best known models is that of Albert Einstein. The physicist who elaborated the Theory of Relativity thought that time should be infinite in both directions and, therefore, defended the hypothesis that the universe has always existed. According to the mathematician and doctor in cosmology Stephen Hawking, from the University of Cambridge, in
England, Einstein did so to avoid embarrassing questions about the creation of the universe outside the realm of science, but the calculations of Hawking and his colleague Roger Penrose, based on Einstein's own concept of general relativity (which presupposes the curvature of spacetime ), led to another conclusion. “Time would have to start at the Big Bang,” says Hawking. "And an end when stars or galaxies collapse under their own gravity to form black holes."
Einstein's model, not yet discarded, leads to an oscillating universe scenario, which would alternate periods of expansion, from bangs, and contraction to the singularity of black holes - points at which matter returns to the condition of concentration, energy and infinite temperature, like before the start of everything. It is reminiscent of the assertion of the Stoic philosophers in ancient Greece that the world is destined to be infinitely destroyed and reconstructed. And also the notion of cycles of destruction and construction of the mystical doctrines of the East, such as Taoism and Hinduism.
The point is that the current assessment of the radiations from the stars, which signal the accelerated departure of the galaxies, suggests a flat universe, in the process of eternal expansion, which strengthens other cosmological hypotheses.
When the so-called superstring theory was developed in the 1980s, it was thought that a Theory of Everything had finally been achieved. The model proposes the existence of 11 dimensions (strings), which would involve the existence of similar universes and others totally different from ours, where there could be even more than one time dimension or no stars or galaxies. The theory doesn't rule out events like the Big Bang, it just doesn't consider them as episodes of a unique story for the cosmos.
Today, the hope of obtaining a single theory is represented, for Hawking, in Theory M (for “matrix”), which connects five versions of string theory. “What has convinced a lot of people to take models with extra dimensions seriously is the web of unexpected relationships between them,” says Hawking. "This shows that all models are different aspects of the same basic theory."
on the edge of science
Cosmology is not a static science and has constantly surpassed ideas that seemed unshakable in the past, a fact that is justified, in part, by the very object of its study – the immensity of the universe – and the limitation to test its theories in the laboratory. It is in the mathematics of scientists that the models assert themselves, waiting for future confirmation by new astronomical discoveries or experimental proofs in particle accelerators. At the moment, the limit of cosmology is the vacuum fluctuation, cited in this article. To understand what existed before this stage, recalls Francisco Jablonski, it would be necessary to advance further in the knowledge of quantum gravity. “From that point on, you can only speculate outside the realm of science”, says Hugo Reis.
However, theoretical and mathematical physicists have been trying, in the last four decades, to break this barrier with audacious hypotheses that bring physics and cosmology closer to philosophical and even religious inferences (the concept of matter formation by vacuum fluctuation, incidentally, recalls the Buddhists' emptiness, the transcendental womb where everything is generated and where everything returns). This is the case of the American physicist John Archibald Wheeler, a colleague of Einstein and Niels Bohr and mentor of several exponents of modern physics, who coined the expression “black hole”. At 90, Wheeler strives to demonstrate that the universe is real, in part, because we observe it. Maybe the cosmos doesn't exist when we don't look at it. Just like this magazine would only exist because you are looking at it.
His arguments are based on the laws (and laboratory experiments) of quantum physics, which demonstrate, for example, that the behavior and trajectory of an electron are always influenced by the observer. In an experiment, the electron can behave like a particle or like a wave and follow this or that path in its journey from one point to another: the decisive factor in any of the possibilities will always be the eye of the experimenter. In quantum mechanics the universe seems to emerge as an extremely interactive place, at least at its fundamental levels.
Wheeler supposes a cosmos where not only the future is indeterminate, but the past as well. When we immerse ourselves in time in search of our origin – in the Big Bang or primordial fluctuation – our current observations would select one of the many possible quantum histories for the universe. Wheeler is not alone. Renowned physicists, such as Andrei Linde, even consider that a Theory of Everything will never be successfully established without taking into account the interaction between reality and the observer and even the presence of a consciousness as a factor in the construction of the universe.
The adventure of deciphering the cosmos is far from over and it may never end. The consolation is that it is one of the most fascinating in science – research delights even when the answers are far away.
inflationary universe
How quantum gravity saved us from absolute zero.
Zero
Quantum Gravity: Energy Containing Virtual Particles
10-37 seconds
After vacuum fluctuation, sudden change in electric field, photons turn into tiny particles. Gravitational repulsion initiates the inflation process, expanding the area and creating matter
10-6 seconds
The first protons and neutrons appear. The particles collide with each other. The gas heats up, the particle soup explodes in the Big Bang
300 000 years
Cooling allows the appearance of the first atoms and the first stars are born
1 billion years
The first galaxies with few stars collided with each other, giving rise to the clusters we know today
10-34 seconds
End of accelerated inflation. The universe is the size of a marble
15 billion years
Today, galaxies continue to expand
150 billion years
In an even cooler cosmos than today, the galaxies will be so far apart that from Earth we will only see the Milky Way and Andromeda.
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