3. What is the essence of this hypothesis?
4. Who was the first version of this hypothesis suggested by?
5. When was it suggested?
6. What were the inconsistencies of this version?
7. What was the last version of this hypothesis called?
8. What main idea was introduced into chaotic hypothesis?
9. How does the author explain the first instants of the origin of the Universe?
10. What consequences did the first phase of exponential expansion of a tiny seed of the Universe lead to?
• Think and say a few words about:
a) the historical aspect of scientific hypotheses on the origin of the Universe;
b) the hypothesis of inflationary Universe;
c) the essence of the hypothesis.
CLASS WO к к
READING (7H)
• Before reading the passage below, let us remember be*. ; :io « . iVx - v аГ
Universe.
Condition
CoaseqiiiiKi-
Enough matter to close on itself 1. Our Universe is niid< :-.-ageJ
2. Expansion —> stop ; с-.лШжо'.ч1. —> Big Crunch
3. Protons will not have ите to с сcay (10 4 years)
• Now, read the passage and find all the similarities and diticrciices with i>. >se 14 Scenario 2 (5 minutes are preferable).
SCENARIO2. A IARGE FINITE UNIVERSE
From what we presently know about cosmology, it is possible th. the Universe is finite but immensely larger than we can observe at this time, "'"his possibility would require that the density of energy in the Universe be si;g!,,.iv larger than the amount needed to cause the Universe to close.
If this is the actual situation, the Universe will continue to expand fo- very much longer than it has already existed. Although it will eventually sk.- \v' begin to contract, our current space-time is in its infancy. The long-term fir. г re ofthe Universe would then depend on the behaviour of matter, so that s.-:'i -Universe is of more interest to physicists than that of Scenario I.
In a large finite Universe, very slow processes that could change the char.ictc ofthe matter in the Universe would have time to act during the long period of expansion. *Physicists have identified a numberofsueh hypothetical processes, all of which act over time scales that are much greater than the present age or the Universe, but which could be considered short compared to its ultimate life span. One such process is the decay of protons into lighter particles, which, if it occurs, would require at least 10" years on the average. *Another possih, ity is that quantum mechanical effects will lead relatively small bits of matter to spontaneously collapse into black holes. It is difficult to make precise estimates of how much time such an event would take, but it is likely to take extremely long, much longer even than for protons to decay. Some matter will end up in black holes more quickly, as gravity makes some stars and galaxies collapse.
*Although the ultimate fate of the black holes is unknown, as they slowly evaporate, most of the matter that was caught in them will be transformed into radiation by the process conceived of by 1 Iawking. Therefore, whet her or not isolated protons decay into.lighter particles, ifthe Universe continues to expand lor long enough, much of the matter presently in it will ultimately be changed into photons and any other massless particles that may exist.
There is still another possibility, which is relevant ifthe Universe contains large numbers of neutrinos and antineutrinos, or other weakly interacting particles with small mass. Like electrons and positrons, these neutrinos and antineutrinos can, when they collide, convert into photons, a process known as annihilation. Although the rate at which this happens is low, if the Universe lives long enough, many neutrinos and antineutrinos will annihilate. There is a theory that the energy density of these weakly interacting particles produces the gravity that holds galaxies and clusters of galaxies together. *If this is true, then their annihilation could lead to the instability of galaxies, the most characteristic objects in our present Universe. It seems likely, then, that the most familiar objects in the present Universe, from atoms through galactic clusters, are not eternal. They will disappear in the future, ifthe Universe lives long enough.
This scenario should not surprise us. If the most important constituents of the present Universe are destined to disappear, they will surely be replaced by something new. From what we know of the past evolution of the Universe this has happened several times in the past as the Universe went from one dominated by many distinct particle species to one dominated by photons to one dominated by protons.
Some physicists have tried to describe the Universe that would develop after the protons have decayed or the black holes have swallowed up matter as we know it. These considerations would apply either to the large finite Universe of the present scenario (so long as it is still expanding) or to the next scenario, in which the Universe is finite and expands forever. The analysis is not complete, but it suggests that some forms of matter other than photons would persist (continue to act) in such a future Universe.
The protons that are present in our Universe would decay into positrons. These positrons can annihilate with the electrons already present to yield photons. *However, the extent to which this happens depends on the rate of expansion of the Universe, which by increasing the average distance between particles, decreases the chance of annihilation. The analyses that have been given suggest that many of the positrons will Find themselves too faraway from an electron to annihilate. Consequently, some positrons, and an equal number of electrons, will remain indefinitely. The same appears to be true for neutrinos of finite mass, if there are any such particles. In any event, these particles that remain could form more complex stable structures, bound together by gravity orelectromagnetism. These structures will be immensely largerthanthe familiar atoms, indeed, some maybe larger than the present observable Universe!
How complex these structures can become is an unsolved problem. It is difficult to analyse it in detail, because of the extreme disparity in scale between the structures that are familiar to us and anything that may evolve in the late
Universe. However, this change in scale is not unprecedented in the history of the Universe. *In its earliest moments, the whole region that eventually evolved into the present Universe was much smaller than an atom or even a subatomic particle. *If there could have been an intelligence that functioned in the early instants of the Universe, the familiar structures of our present Universe would seem as grossly extended as the supergalactic atoms of the late Universe would appear to us. *It is not beyond our ability to understand complexity in the late Universe, once we set our minds to it. 1 believe that understanding that complexity, and solving its related problems, will represent a novel branch of science in the future.
*No matter how large, ifthe Universe is finite, eventually the expansion will cease and contraction will take over. The details of what will happen during this contraction would be rather different from those in Scenario 1, because the contents of the Universe would be different in each case. *Yet, the outcome is no less mysterious, so poorly are the phases of turnover and contraction understood. *If we learn that the Universe is finite, unraveling what will take place during these phases will become one of the important endeavours of future science.
• Try to guess the meaning of the words given in italics in the text.
• Translate the sentences marked with an asterisk.
• Look through the text and try to answer the following questions.
1. What conditions are needed for the Universe to be larger than that in Scenario 1?