Hi Another take of the uncertanty about death.
The Uncertainty of Life or Death--Theories about the Future of the Universe
How will it end?
Asking for an ending without knowing the beginning may seem queer, but this is indeed the case in the field of cosmology. Although much controversy still surrounds the beginning of the Universe, man has already embarked on the search for its end. Discontented with living in uncertainty, man has embarked on the search for the ultimate fate of the world, hoping to catch a glimpse of what future holds in store for him and his successors. Through the years, many hypotheses regarding the fate of the Universe have been formulated. In this essay, a few of the more popular theories will be highlighted to introduce the reader to the possible futures that lie ahead for our Universe.
The term "Heat Death" was conjured in the 1860s to describe the doomed fate of the Universe as the world tends towards thermal equilibrium. Without prior knowledge of whether the Universe was static or dynamic, this prediction of the end of the Universe made by Hermann von Helmholtz was purely based on the physical laws of thermodynamics.
The laws of thermodynamics can be briefly summarised by Rudolf Clausius's statement "Die Energie der Welt bleibt konstant; die Entropie strebt einem Maximum zu." Translated, it states that the energy of the world remains constant (first law); the entropy strives to a maximum (second law). Simply put, the second law of thermodynamics means that the total entropy for a thermally closed system cannot be less than zero.
This statement then implies that the total entropy for the thermally closed Universe would always increase until it reached a maximum value, where the world would be in a state of total disorder. Eventually, the Universe would be of uniform temperature and density. All physical, chemical and biological processes then cease in a state of perfect disorder where no energy could be available for work. This is the gloomy picture of the Universe as it "suffers" from its "Heat Death".
Since the theory of the Universe ending in a "Heat Death" was based upon the fundamental laws of physics (second law of thermodynamics), this theory that the Universe would eventually reach thermal equilibrium would hold true regardless of which model the Universe belongs to, as physical laws are believed to be constant in this Universe. However, the "Heat Death" theory would have to be modified slightly in order to fit in with the present knowledge of a non-static Universe, such as in the case of the "Big Chill" theory mentioned later.
The significant contributions of the "Heat Death" model are not just its prediction of how the Universe would end, but also its implication that we live in a finite world. Since there exists an ultimate end for the world (based on the model), there must have come a time for its beginning, for a world with an end can no longer be claimed to be infinite. In a way, the prediction of the "Heat Death" sparked off the search for more scientific explanations of the "whys" and "how" of the beginning and the end of the Universe.
The realisation that we live in a non-static world only came about in the 1920s with the work of Alexander Friedmann and later the observational confirmations by Edwin Hubble. Embracing the idea of an expanding Universe, alternative models for the future of the Universe were proposed based on the struggle between the momentum of expansion (from the Big Bang) and the pull of gravity. The new models mainly dealt with the geometry of the Universe as well as its implications on the fate of the Universe.
The most important number that determines the future of the Universe is omega: the ratio of the actual density of the Universe to its critical density. Combining Einstein's General Theory of Relativity with Friedmann's assumptions of the homogeneity and isotropy of the Universe, there exist three possible scenarios for the end of the Universe.
In the case of omega being greater than one (momentum of expansion from the "Big Bang" would overcome the gravitational pull) then the geometry of space is open and negatively curved. The Universe would experience infinite expansion, and end up in what is known as the "Big Chill'. The end would come in a state of ultimate coldness and darkness, with a background radiation of near absolute zero (temperature drops as the universe expands). Even the black holes formed as the world expanded would have radiated away, leaving behind a diffused sea of particles and sub-particles. The Universe would have reached maximum disorder in a revised model of the "Heat Death" whereby all thermodynamic activities would come to a halt, and all remaining energy in the universe would be attenuated without limit.
As for an omega value of less than one, (gravitational force wins over momentum) the geometry of space is closed and positively curved. This model predicts that the expansion of the Universe would come to a halt, followed by the reverse process of contraction. The Universe would then end in a "Big Crunch", whereby it reaches a state of infinite density and extreme temperature of at least 10 000K, with all matter being consumed by numerous black holes. Finally, the Universe would become an infinitely small point containing highly condensed matter, a singularity similar to the state it was in prior to the "Big Bang", but with maximum entropy instead of the highly ordered state in which it existed just before the "Big Bang".
"What happens next?" one may ask. Indeed, the step succeeding the "Big Crunch" has led to much controversy among cosmologists. The most appealing scenario is that the Universe would "bounce" after shrinking to a very small size and be reborn in another "Big Bang". This would create a pulsating Universe that oscillates between the "Big Bang" and the "Big Crunch". This would result in an endless cycle for the Universe, thus avoiding its impending doom. However, it is not possible for the cosmological cycles to be identical. They would grow in size due to irreversible processes, such as the formation of black holes, and the increase in heat energy due to heat contribution from starlight. As a consequence, each cycle grows larger in size and lasts longer than the previous one. Eventually, future cycles become so large that they would expand without limit (similar to the infinite expansion Universe of the "Big Chill" model). The degenerative influences of the second law of thermodynamics would still operate, and the "Heat Death" of the Universe seems inevitable once again.
A more pessimistic view proposes that the infinitely small Universe would just pinch itself out and disappear into nothingness in a reversal of the original quantum fluctuation, which is believed to be an explanation of how the Universe came into existence before the "Big Bang" took place. Hence, this means effectively, that the end of the Universe would be its disappearance into nothingness, and there would be no more future for the Universe, so to speak.
If omega is exactly equal to one, the space geometry is flat, and the expansion of the Universe would ultimately stop, and the world would remain static--neither expanding nor contracting. However, the expansion would come to a halt in an infinite period of time, and for all practical discussions, the future of a flat Universe would be similar to that of an open Universe experiencing infinite expansion.
So which of the above three models would apply to our Universe? Both the Inflationary Theory and quantum fluctuation predict omega of value exactly equal to one, thus supporting a flat universe. Stephen Hawking and Jim Hartle's proposal of a "no-boundary" universe on the other hand, predicts that a closed and uniform universe, with no boundary in time and space, is the only type of universe that can occur. Recent measurements have calculated the value of omega to 0.9 with an uncertainty of 0.5. Based on current figures, the Universe could either be closed or open, or even flat. It seems therefore, that further research is needed to provide for more accurate information before predictions of greater precision as to the future of the Universe could be made. Up till now, the future seems rather open-ended.
Another possible scenario for the Universe (also a more emotionally appealing one), based on the redefined Inflationary Theory by Andrei Linde in 1983, proposes that the quantum state of the early universe might have varied in a chaotic manner from place to place in varying degrees of excitement. In the excited regions, inflation might have occurred, with the highly inflated states inflating fastest and decaying slowest. The regions with greatest inflation would thus occupy the most amount of the total space.
As a result of chaotic inflation, the universe would be divided into clusters of mini-universes of varying sizes. The Universe that we live in would be only one of many mini-universes, but occupying a large area in space due its initial rapid inflation. As inflation is a continuous process in this model, mini-universes would undergo endless cycles of birth and death at any point in time. In a way, this model describes a sort of eternal universe where even the existence of a beginning is questionable.
Similar to the theory of eternal universe is the theory of baby universes. In the case where a false vacuum is surrounded by true vacuum, the false vacuum would expand, but not at the expense of the true vacuum. In this model, the Universe we live in would actually be a baby universe (an expanded false vacuum) formed out of its mother universe. The baby universe was once connected to the mother universe by a wormhole. From the viewpoint of the true vacuum (mother universe), the region of space occupied by the inflated false vacuum would only look like a black hole. Once the baby universe has formed (in a very short period of time according to the Inflationary Theory), the connecting wormhole would evaporate away by Hawking's radiation. The baby universe would therefore be disconnected from the mother universe and exist on its own, creating its own space without threatening the existence of the mother universe. It would then seem possible to achieve genuine immortality should man be able to "create" baby universes from our own Universe and "migrate" into these baby universes before the death of our Universe.
The two models mentioned above are highly theoretical, and are not very likely to come true, unless new evidence can be found to support them. However, these theories predict infinite birth and death cycles of universes, and are highly appealing to scientists (and many others) who would rather believe in an ever-existing world than the impending death of the Universe that other theories postulate.
From the "Heat Death" theory to the baby universe model, the development of cosmological science in the search of the future of the Universe has indeed come a long way. Numerous models have since been put forward, some with more supporting evidence, some more theoretically based, and a few others more emotionally appealing to the human race. Though initially set out to dispel the mysteries of the Universe, man has found that his search for the end of the Universe has left him with greater uncertainties instead. However, one thing is certain--the search for the ultimate fate of the Universe would continue, until we can declare with confidence, "this is how it will end".
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