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PHVSICS OF THE IMPOSSIBLE
This problem is actually an old one, dating back to 1916 when Einstein first introduced the cosmological constant. Soon after proposing
general relativity the previous year, he worked out the cosmological
implications of his own theory. Much to his surprise, he found that the
universe was dynamic, that it either expanded or contracted. But this
idea seemed to contradict the data.
Einstein was encountering the Bentley paradox, which had bedeviled even Newton. Back in 1692 the Reverend Richard Bentley wrote
Newton an innocent letter with a devastating question. If Newton's
gravity was always attractive, Bentley asked, then why doesn't the universe collapse? If the universe consists of a finite collection of stars that
mutually attract each other, then the stars should come together and
the universe should collapse into a fireball! Newton was deeply troubled by this letter, since it pointed out a key flaw in his theory of gravity: any theory of gravity that is attractive is inherently unstable. Any
finite collection of stars will inevitably collapse under gravity.
Newton wrote back that the only way to create a stable universe
was to have an infinite and uniform collection of stars, with each star
being pulled in all directions, so that all the forces cancel out. It was a
clever solution, but Newton was smart enough to realize that such stability was deceptive. Like a house of cards, the tiniest of vibrations
would cause the whole thing to collapse. It was "metastable"; that is,
it was temporarily stable until the slightest perturbations caused it
to crash. Newton concluded that God was necessary to periodically
nudge the stars a bit so the universe did not collapse.
In other words, Newton saw the universe as a gigantic clock,
wound up by God at the beginning of time and obeying Newton's laws.
It has been ticking automatically ever since, without divine intervention. However, according to Newton, God was necessary to tweak the
stars once in a while so the universe did not collapse into a fireball.
When Einstein stumbled on the Bentley paradox in 1916, his equations correctly told him that the universe was dynamic-either expanding or contracting-and that a static universe was unstable and would
collapse due to gravity. But the astronomers insisted at that time that
PHVSICS OF THE IMPOSSIBLE
This problem is actually an old one, dating back to 1916 when Einstein first introduced the cosmological constant. Soon after proposing
general relativity the previous year, he worked out the cosmological
implications of his own theory. Much to his surprise, he found that the
universe was dynamic, that it either expanded or contracted. But this
idea seemed to contradict the data.
Einstein was encountering the Bentley paradox, which had bedeviled even Newton. Back in 1692 the Reverend Richard Bentley wrote
Newton an innocent letter with a devastating question. If Newton's
gravity was always attractive, Bentley asked, then why doesn't the universe collapse? If the universe consists of a finite collection of stars that
mutually attract each other, then the stars should come together and
the universe should collapse into a fireball! Newton was deeply troubled by this letter, since it pointed out a key flaw in his theory of gravity: any theory of gravity that is attractive is inherently unstable. Any
finite collection of stars will inevitably collapse under gravity.
Newton wrote back that the only way to create a stable universe
was to have an infinite and uniform collection of stars, with each star
being pulled in all directions, so that all the forces cancel out. It was a
clever solution, but Newton was smart enough to realize that such stability was deceptive. Like a house of cards, the tiniest of vibrations
would cause the whole thing to collapse. It was "metastable"; that is,
it was temporarily stable until the slightest perturbations caused it
to crash. Newton concluded that God was necessary to periodically
nudge the stars a bit so the universe did not collapse.
In other words, Newton saw the universe as a gigantic clock,
wound up by God at the beginning of time and obeying Newton's laws.
It has been ticking automatically ever since, without divine intervention. However, according to Newton, God was necessary to tweak the
stars once in a while so the universe did not collapse into a fireball.
When Einstein stumbled on the Bentley paradox in 1916, his equations correctly told him that the universe was dynamic-either expanding or contracting-and that a static universe was unstable and would
collapse due to gravity. But the astronomers insisted at that time that