Since time out of mind the universe has beckoned to man as a tantalizing enigma. First with the naked eye and then aided by every sort of eyepieces, our forefathers watched all the various cosmic bodies and phenomena, emissions and that sort of thing. These observations spawned many theories concerning the origin of the universe. A real breakthrough came only in the last three or four decades of the twentieth century owing to space exploration, piloted space vehicles in particular, and ever more sophisticated research technology. Cosmology and space exploration was the subject discussed by Dr. Igor Novikov, Corresponding Member of the Russian Academy of Sciences. Dr. Novikov is the chief researcher of the Astronomical Center at FIAN, or the Physics Institute of the Academy of Sciences; he is also director of the Theoretical

Astrophysics Center based in Copenhagen, Denmark. Here's the gist of his article.

Way back in 1922 to 1924 the Russian scientist Alexander Fried- man, proceeding from equations evolved by Albert Einstein, a Nobel prize winner and honorary member of the USSR Academy of Sciences, postulated: the universe keeps expanding; and a few years after that, in 1929, the American astronomer Edwin Hubble confirmed this prediction and proved that the divergence, or drifting apart, of galaxies is a law.

Speaking about the expanding universe, one usually illustrates this phenomenon by the following analogy. Now take a rubber ball and imagine that galaxies are so many tags on its surface. The distances between these tags will increase once you blow up the ball. Such two-dimensionality fits well in a system of coordinates devised by Joseph Louis Lagrange (1736-1813), a French mechanic and mathematician, member of the St. Petersburg Academy of Sciences; besides, it is very convenient for machine computations.

With the rate of the mutual divergence of galaxies now determined quite well, we can calculate the rate of the expansion of the universe. It all began about 15 billion years ago.

The primary, zero-cycle matter was very dense, well-nigh homogeneous and awfully hot. In the course of its expansion the temperature started falling - it fell to 1 billion degrees on the Kelvin scale (representing absolute zero, -273.15 ⁰ centigrade, as zero degree) within just a few minutes. Light chemical elements were synthesized at that time; heavy elements appeared much later, in stars.

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In about 300 thousand years, when the temperature of matter was down to 3-4 thousand degrees on the Kelvin scale, the hot plasma converted to neutral gas - that's what we call plasma recombination. At that stage there were none of the stars and galaxies, they came to be much later, at a time much closer to our epoch, due to the inhomogeneity of cosmic matter caused by gravitational instability in the course of evolution.

Now what caused the universe to expand? What was the primary pulse to impart matter the initial velocities? The plasma was very hot, yes, and the pressure within it enormous. Yet this does not explain anything. To touch off the process there should be a differential between the internal state of matter and the ambient environment. But there was no differential like that. Say, in a bomb blast hot gases - extremely dense! - have a much higher pressure than the surrounding atmosphere. This difference generates a hydrodynamic force which scatters bomb fragments (fragments of matter).

With matter persisting homogeneous, there could be no space outside the primary universe. So pressure differentials were out of the question. As such, high temperature does not impart initial velocities to scatter matter.

Dr. Erast dinner, a physicist and mathematician, expressed some surmises on this score in the 1960s. This is what he hypothesized: at first matter persisted in what he called a vacuum state - it had an immense pressure, but a negative one only. This phenomenon may be compared to simple tension which we come to deal with, say, in a piece of stretched rubber.

The negative pressure was distributed evenly throughout the universe, and it could not give rise to any hydrodynamic force. However, the vacuum state of matter can produce mutual (gravitational) repulsion, the way it happens to electrical particles of identical charge. Such kind of repulsion, according to Dr. Glinner, was the cause of the first, initiating pulse.

Although this idea looked absurd at first, further studies showed its relevancy, and now it is commonly accepted.

In time, Dr. Novikov goes on to say, the universe kept expanding ever faster by dint of gravitational repulsion. Originally, just as it came into being, the universe was infinitesimal in size - a mere 10 ^-33 cm; well, the atomic nucleus is 20 orders of magnitude as large (that is by a factor of 10 ²⁰ ). However, the density of the primary universe was enormous, as much as 10 ⁹³ g/cm; yet the total mass of matter was equal to just 10 ^-5 to 10 ^-6 g. But then its volume started expanding at a very fast rate, while its density changed but little, if any; which means that the mass of matter kept increasing.

But the vacuum matter (or inflatron in specialist lingo) was quite unstable and, just in a negligible fraction of a second (10 ^-36 s), it broke down into quanta to become a hot plasma, or ordinary matter. That was the natural birth of our hot universe. In an instant, so short as to beat our imagination, it blew up by what might appear an infinite number of times - 10 ⁽¹⁰⁾⁹ (imagine the figure one with a billion naughts) - and became far larger than the discernible part of the universe today.

Such are the conclusions which scientists have made on the basis of the present and much sophisticated physical and mathematical theory. Yet corresponding experimental studies are necessary to prove the point. Are they possible at all? Yes, they are.

In nature nothing vanishes without leaving a trace. The universe retains visible traces of its earliest evolution. We can learn a good deal from a phenomenon discovered in 1965; this is a weak electromagnetic radiation otherwise known as relict radiation (yet another name for it is the cosmic microwave background). It can tell us about the first moments of the expanding universe. And by deciphering these data, we shall confirm or refute the theoretical constructions.

Relict radiation is reaching the earth all around, and the intensity of this radiation is nearly identical-its variations are very small, making up a 100,000th part of the temperature equal to 3 ⁰ K (three degrees on the Kelvin scale).

In the 1980s our researchers were the first who tried to measure relict radiation fluctuations (variations) with the aid of the artificial earth satellite Relict. In 1989 an American space vehicle identified this radiation. The results of these experiments were published in 1992, considered to be a year when relict radiation fluctuations were discovered.

In spite of the very fact - that the phenomenon was discovered-the data obtained during observations happened to be rather incomplete because the instruments employed had a resolution of only 7 ⁰ . But thereupon radio telescopes came to be used, both ground-based and "flying" ones, carried aloft by balloons into the upper strata of the atmosphere. Finally, in 2000, one managed to obtain new data on relict radiation by means of instruments having a better angular resolution than previously; this information confirmed the tentative theoretical conclusions. The first successful experiment in this series was the Boomerang project (Italy), with a balloon-launched radio telescope. There came other experiments too.

Looking into research trends, Dr. Novikov also dwelled on the Russian experiment dubbed Kosmologicheski gen ("Cosmological Gene") which will involve the world's most powerful reflecting radio telescope, RATAN-600, equipped with a mirror of 600 meters in diameter. This project, if realized, would give us a large body of relevant information even well before the international space project Plank due in 2003, the largest so far.

Dr. Novikov described certain physical parameters of relict radiation, those that could be measured and compared with theoretical pre-

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dictions. One such parameter (let's designate it with the omega symbol,  ) characterizes the general curvature of the three-dimensional space of the universe and is a function of the density of matter and the rate of its expansion. In this case the theoretical and the experimental data concur, with  = 1 and  =1.08+/-0.06, respectively.

Another parameter (n) denotes a dependence between the dimensions of minor inhomogeneities that appeared in the universe soon after its birth, and their amplitude. In this particular case the theory predicts: the relative amplitude of these inhomogeneities should not depend on their dimensions and stay invariable at every scale, that is with n=1, which is within measurement error and confirmed by experimental studies.

Such kind of concord of theoretical calculations and direct astronomical observations enables us to say that at the initial stage of its existence the universe did experience an inflationary period, a time of violent expansion. This period must have set in 10 ^-43 seconds after the very birth. But what came next?

There is no hard and fast answer to this question yet, though certain suggestions are uttered. Say, by contemporary notions the inflation (blow-up) of the universe was preceded by its quantum state (time, less than 10 ^-43 s and size, on the order of 10 ^-33 cm), when space and time could not be regarded as analogue quantities (continuities) but rather as separate quanta; and all that was in a state of boiling vacuum, so to speak, with its density being enormous, 10 ^-93 g/cm. Besides, space - its dimensionality and topology - kept up in a most sophisticated quantum flux.

Today most up-to-date and powerful computers assist the studies of the universe. Dr. Novikov cites just one example of computations made in a coordinate system that inflates together with matter. As shown by such computations, due to quantum fluctuations a "boiling vacuum" may convert at odd moments into bubbles of inflating universes (this is a random process, mind you). Some of these universes are like ours, while others may have absolutely different physical characteristics and obey just as different laws. Such is the computer simulation of the process shown on the display. The "bubble universes" are on and off, blowing up all of a sudden and reverting to the quantum state of a "boiling vacuum". This is an open-ended process which knows no boundaries and no limits. It is perpetual boiling whereby new galaxies are born and die. That's how our contemporary science visualizes the origin and evolution of the infinite Cosmos.

I. Novikov, "An Inflationary Model of the Early Universe". - Vestnik RAN (RAS Bulletin), Vol. 71, No. 10, 2001

Prepared by Arkady MALTSEV

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