1. What is the Universe according to the chaotic inflation scenario?
2. What problems does the chaotic hypothesis remove and why?
3. What does each domain of the Universe look like?
4. How does this hypothesis explain the dimensionality of our system?
5. How does the author account for the first instants of the origin of the Universe?
6. What really fantastic science-fiction figures do scientists have to realize in developing a complete theory of the Universe?
7. Which of the facts impress your imagination most?
1 Г.. И. Куршпии.-н
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CLASSWORK
READING (8B)
Before reading the passage below, let us remember Scenarios 1 and 2 of a finite small and large Universes.
Scenario 1
Scenario 2
Condition
Enough matter for the Universe to close on itself.
The density of energy in the Universe is slightly larger than needed for the Universe to close.
Scenario 1
Scenario 2
Consequences
1. Middle-aged Universe.
2. Expansion —> stop —» contraction —> Big Crunch.
3. Protons will not have time to decay.
1. The Universe is in its infancy.
2. Very long expansion —> stop —> contraction —> Big Crunch.
3. Decay of protons into lighter particles, spontaneous collapse of matter into black holes. Annihilations of neutrinos and anti-neutrinos. I nstability of galaxies.
• Now, read the passage and give your opinion on the fate of the Universe according to Scenario 3.
SCENARIO3. AN INFINITE UNIVERSE
*If the density of matter were less than a critical amount, corresponding to about 10 29 grams per cubic centimeter — about ten milligrams in a region the size of the Earth — then the Universe is infinite, and will expand for ever. "■Objects in the Universe will, on the average, get farther and farther apart, except for those such as the contents ofthe solar system, which are held together by forces such as gravity. As in Scenario 2, the contents of the Universe will change, and their eventualform will depend on presently unknown properties of subatomic particles and on the end state of black holes. On the whole, the future ofthe Universe in Scenario 3 is about the same as in Scenario 2, except that the expansion never slows to zero and reverses. The Universe of Scenario 3 becomes one in which protons, electrons, neutrinos and their antiparticles are spread ever more thinly through larger and larger regions of space. *Once again, however, we do not know whether gravity and elcctromagnetism would allow these objects to form complex structures able to persist indefinitely.
However, there is a missing piece in our puzzle, one that might apply to the large finite Universe. Most cosmological models have assumed that the Universe is homogeneous — that all parts of it are the same, including those beyond the reach of our telescopes and hence unknown. The assumption of homogeneity has been made in order to simplify the mathematical description that physicists give to the Universe.
*Recently, this assumption has been questioned. We have seen that physicists believe that some features of the present Universe depend on the broken symmetry that occurred in the early Universe. Yet this symmetry breaking need not have occurred uniformly over the whole of spacetime. Just as a lake in winter can be liquid in some regions and solid in others, so might different regions of space be in different phases, which would imply different physical properties for the matter in it. For example, the surplus of what we call matter in our visible Universe might be replaced by equal amounts of matter and ant imatter or a surplus of antimatter in parts of space-time beyond our present horizon. But now let us return to the view that the properties of particles will change slowly as the Universe expands. Some scientists have predicted that rapid phase transitions similar to those that took place in the early Universe will occur in the future. This could happen if the present configuration of quantum fields in our region of space has more energy than another configuration, and is therefore unstable against transformation into the lower energy configuration.
*lf such phase transitions occur, they are expected to begin in one place, perhaps as the result of a random fluctuation, and then spread outward at the speed of light, eventually encompassing every point in space. *As the transition passes through any point, those properties of matter that depend on the background quantum fields present there, would have to change suddenly because of the new conditions. *A sudden change in the properties of subatomic particles would lead to tremendous changes in any structures composed of Ihcm, and it is unlikely that these structures would persist. It has even been suggested that such a phase change has begun in anothersection ofthe Universe, and is now approaching us at the speed of light. But there is no evidence forthis possibility, and we need to analyse it further before adding it to the list of environmental catastrophes that we need to worry about.
If the Universe continues to expand long enough for the matter to change its form drastically, then intelligent creatures may have agreater role to play in the distant future than they would in a Universe that eventually contracts. They would have to grapple with two problems: the disappearance of the protons and bound neutrons that form the material bases for most structures in the present Universe, and the ever smaller amounts of free energy that would be available to preserve order in whatever structures might replace them. *No good solutions to these problems have yet emerged, but since we have been studying them for only a few years, and will not need the answers for 10J0yearsorso, wc need not despair.
• 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 arc needed for our Universe to be infinite?