Expanding but Uncreated
If one makes a graph of the average distance between galaxies over time the line must be rising since the beginning. This is the expanding phase. Later, if the universe does not have sufficient expanding velocity for its density and gravity, the line must reach a maximum and then descend. The graph of such a universe will look like the trajectory of a ball after its first bounce and before its second bounce. But a ball can make a number of bounces. This gets many cosmologists thinking about what we may call the “bouncing universe.” The idea has a connection with the Hindu idea of universal cycles.
The Cyclic Universe
Hindu philosophy provides a cosmology that is both degenerative and cyclic. The universe was good when created in the first phase, the Krita Yuga. Then it degenerated through phases of less and less goodness until the present age, the Kali Yuga. We await floods and fire that will destroy the universe. Then it will be recreated and a new cycle will begin. Some people have seen here a prediction of the physical quantity called entropy as early as 2600 years before the present. However, they are confusing degeneration and decay with entropy.
The Hindu philosophy appeals to some people who do not like the philosophical implications of a single beginning. Hinduism, like most ancient religions, has a number of major and minor deities. There is no overarching Supreme Being who is uncreated but creates all other things, and perhaps settles all accounts before restoring the universe to its original pristine state.
Some modern cosmologists have sought to echo the Hindu cosmology and make the universe cyclic. But let’s note that they do not avoid the idea of creation. They substitute many epochs of regeneration for a single act of creation.
Quite apart from the philosophical attractions and theological conveniences of Hindu cosmology, what does scientific observation have to say about the possibility that the universe is cyclic and goes through a series of bounces?
When cosmologists knew that the universe might be destined eventually to expand or contract astronomers began making surveys of the distribution of galaxies. Measuring carefully the masses and distances of the galaxies, they concluded that the density is too low by a factor of ten to produce enough gravity to stop the expansion. All the evidence said that the universe must expand forever. There would never be even one cycle of expansion and contraction.
A fact like that should have ended the issue, but the proponents of eventual contraction were not put off. They pointed out that astronomers had only surveyed luminous matter. Additional gravity might come from dark matter. The search for dark matter we mentioned earlier actually started many years ago.
Data from the WMAP satellite recently ruled out future contraction but insisted there must be enough dark matter and dark energy to slow the expansion of the universe to the slowest possible rate.
The Cyclic Universe
Hindu philosophy provides a cosmology that is both degenerative and cyclic. The universe was good when created in the first phase, the Krita Yuga. Then it degenerated through phases of less and less goodness until the present age, the Kali Yuga. We await floods and fire that will destroy the universe. Then it will be recreated and a new cycle will begin. Some people have seen here a prediction of the physical quantity called entropy as early as 2600 years before the present. However, they are confusing degeneration and decay with entropy.
The Hindu philosophy appeals to some people who do not like the philosophical implications of a single beginning. Hinduism, like most ancient religions, has a number of major and minor deities. There is no overarching Supreme Being who is uncreated but creates all other things, and perhaps settles all accounts before restoring the universe to its original pristine state.
Some modern cosmologists have sought to echo the Hindu cosmology and make the universe cyclic. But let’s note that they do not avoid the idea of creation. They substitute many epochs of regeneration for a single act of creation.
Quite apart from the philosophical attractions and theological conveniences of Hindu cosmology, what does scientific observation have to say about the possibility that the universe is cyclic and goes through a series of bounces?
When cosmologists knew that the universe might be destined eventually to expand or contract astronomers began making surveys of the distribution of galaxies. Measuring carefully the masses and distances of the galaxies, they concluded that the density is too low by a factor of ten to produce enough gravity to stop the expansion. All the evidence said that the universe must expand forever. There would never be even one cycle of expansion and contraction.
A fact like that should have ended the issue, but the proponents of eventual contraction were not put off. They pointed out that astronomers had only surveyed luminous matter. Additional gravity might come from dark matter. The search for dark matter we mentioned earlier actually started many years ago.
Data from the WMAP satellite recently ruled out future contraction but insisted there must be enough dark matter and dark energy to slow the expansion of the universe to the slowest possible rate.