To date, no single theory has been agreed upon that would explain what was before the Big Bang. Experts love to talk about peas
To date, no single theory has been agreed upon that would explain what was before the Big Bang. Experts love to talk about peas. This is the image behind which the following assumption is hidden: before the bang, the entire universe known to us today was locked in one point for an infinite time. This is the pea. Then, suddenly, he undressed. The moment of expansion is called the 'big bang'. In another theory, it is about the oscillating universe: it is an endless, repeating series of bang, expansion, slowing down, stopping, retreating, collapsing into one point - then banging again, and God forbid. This theory is less accepted today, to the point of being denied. Most theories are content with the explanation that time began with the big bang. Therefore, the question of what came first has no meaning. If there is no time, there is no first.
inflation
Prof. Jacob Bekenstein, from the Rakah Institute of Physics at the Hebrew University, explains that, although it is interpreted that way, the new theory developed by Hawking and Neil Turok, does not deal with what happened before the Big Bang, but only with formulating the conditions that brought the universe to be the way it is today. According to the popular theory today, the current universe is the result of one tremendous expansion, which lasted only fractions of a second, immediately after the big bang - and then, of continued expansion at the current, relatively slow rate. The assumption that there was such a rapid expansion - inflation - should solve several problems in cosmology: one of them is the question of how the universe could have maintained a degree of uniformity in expansion, even though billions of years have passed since the big bang. If we accept the assumption that most of the expansion was actually all at once, in a fraction of a second, it is much easier to understand this uniformity.
In recent times, two scientists, Stephen Hawking and Neil Turok, have devoted themselves to a new theory. Hawking, a figure of public weight, mainly thanks to the bestseller 'A Brief History of Time', receives a lot of attention for every scientific step he takes, and the current wave of publications surrounding his new theory precedes a scientific conference in California in a month, where he will present the article he wrote accompanied by explanations. Beckenstein explains that Hawking and Turok's article contains two fundamental assumptions. The first is a mathematical assumption: the space-time sheet is infinite and has no boundaries. The second assumption, easier to clarify, states that a universe that will develop from a state of inflation must be friendly to life. That is, the chemical elements necessary for the development of life can be formed in it - carbon, oxygen, etc. Not every universe has exactly the amount of time necessary to produce these elements. That is, according to Hawking and Turok: life requires an inflationary universe - and one that continues to expand forever.
One of the problems with this argument is that the end determines the beginning. Since there is life, we assume that there was inflation to the appropriate degree. 'It seems very strange,' says Beckenstein, 'that in order to understand how the universe began, you have to make sure that it is friendly to life. This is an anthropocentric argument, with man at its core. Not all scientists take such an argument seriously.'
omega
And now for the problem. Prof. Zvi Piren, also from the Rakah Institute, explains that the accepted inflationary universe theory contradicts observations. There is a certain parameter called omega - a parameter that answers the question of whether the universe is open (that is, continues to expand) or closed (that is, at some point it will stop or even begin to contract). If this parameter is greater than one, it means that the universe is closed. If it is less than one - the universe is open. Assuming that the universe is closed, for example, if we take a spaceship and travel all the time, straight ahead, we will eventually return to the same place we came from. I mean, it's a finite universe. In an open universe - if we travel straight all the time - we will continue to move away forever. And if it is open, it is also infinite.
'These possibilities are related, for very deep reasons, to the future of the universe. If the universe is infinite in its spatial dimensions, it will also continue to expand forever. On the other hand, if it is finite in its spatial dimensions, its expansion will stop at some point and it will begin to shrink back, and within 20 billion years it will reach something opposite to the big bang - and the whole universe will be concentrated in one point. These two options have been known for years.
Piren explains that according to the theories that exist to this day, a situation of inflation can happen when omega is equal to one or very close to this value. However, from observations of the density of the universe, one of the values that define omega, it appears that the value of omega is .0.4 and here, in fact, lies the mine. On the one hand, a reasonable theory of inflation, the omega contract of about one. On the other hand, observations describing an omega of .0.4 is also the mystery that Hawking and Turok tried to solve.
Firn: 'In recent years, Neil Turok has developed several theories of inflation that solve the problem of omega smaller than 1, but they were all artificial and very strange. Now he found, together with Hawking, a variation that comes from a completely different direction - inflation that really gives an omega smaller than 1, and on the other hand gives inflation like it must exist to explain the current universe.
Theory
Piren explains that this is an article that has a speculative dimension. This is not an article that you read and immediately agree that it is not possible otherwise. There are many assumptions that lie in many places, and this is not a theory that will be accepted overnight as the main theory. I assume that it will be treated with the utmost seriousness because it is Hawking, although based on not much different considerations, Hawking believed in the past that the universe must be closed.'
Prof. Avishai Dekel, head of the Institute of Physics at the Hebrew University, claims that 'Hawking's work is just one of many works around the subject of the early universe. When dealing with cosmology there are the speculative fields but the beginning is with observations from telescopes. It starts with us getting evidence that the universe is open. This is not related to Hawking at all, but a figure that we get from observations using all kinds of methods. Our group in Jerusalem is one of the leaders in the field.
Other critics argued that the resonance that Hawking's complex article received in the popular press was merely a kind of publicity gimmick. A new edition of his book is about to be published, and the renowned scientist is promoting it. And how did Hawking and Turok solve the contradiction between inflation and omega?
Piren: 'In the known theory so far there was a moment of the big bang, which we do not know how to describe what happened in it. The universe was at an infinite density that constitutes the beginning of time, and then, after the moment, came that period of inflation that lasted a few fractions of a second. What is beautiful about Hawking and Turok's theory is that they eliminate the need for the Big Bang in the currently accepted way, and talk about a universe that starts with a small starting point and suddenly bursts into inflationary expansion. As long as you are inside this point, time has no meaning. The universe starts from a four-dimensional sphere, with the fourth dimension inside the sphere being the dimension of time. But only as soon as you leave that tiny point and inflation begins - time begins to have meaning.' That is, in the previous theory we talked about a bang followed by an inflationary expansion. In the new theory it is only an expansion - which is, in fact, the moment of the bang.
Then, so the main theory states, the matter expanded, and as it cooled, as a result of the expansion, the subatomic particles were formed, and much later the hydrogen and helium atoms were formed. At some point, as a result of the collisions between the particles, a strong radiation was also created, the echo of which can still be found today. This radiation is known as background radiation, and a number of satellites are trying to locate in which direction in space there are differences in its intensity, although in observations it appears to be the same everywhere.
Today the universe is expanding at a moderate rate. This can be proven by observations that show that all galaxies appear to be moving away from us, and the distant ones are moving away at a very fast rate. Observations towards the beginning of the universe - towards galaxies located at a distance of ten billion light years from the earth, show a universe much different from the current one - although it is also closer to the one of today than to the one after the big bang. That is, even then stars and galaxies existed. In a recent lecture given by Prof. Mario Livio (formerly from the Physics Faculty at the Technion) from the Space Telescope Science Center, who conducts research using the Hubble Telescope, he presented demonstrations of observations made by the Hubble when it was pointed at empty points in the sky with a very long exposure, while photographing in several orbits. To the scientists' surprise, hundreds of 'primitive' galaxies were found in each such field of view. A collection of stars that has not yet been disrupted by collisions between galaxies and neighboring galaxies - these are the collisions that created super galaxies and clusters as they are known today.
As for the end of the universe: according to the situation today, where omega is equal to 0.4, the universe will expand forever. Hawking and Turok's article allows us to assume that this is the correct figure, more or less. The galaxies will keep the stars contained by gravity, and when the energy of the stars is used up they will die and the universe will be dark.
By Avi Blizovsky. Appeared in 'Haaretz', 24/02/1998
