10 How the World Began
199
time, the matter/energy density becomes infinite at a finite point in the past.
When he first proposed his theory, he considered such an infinite density to
be unphysical.
In order to achieve a steady-state universe, and avoid this expansion or
contraction, Einstein introduced an additional arbitrary term into his equations, known as the cosmological constant, Λ. For a stationary solution of
the equations to exist, this new constant had to be fine-tuned , i.e. it had
to have a very precise value. The new term is perfectly compatible with
General Relativity and mathematically consistent. However, any arbitrarily
small perturbation of the density of matter in the universe, or of the value of
the cosmological constant, produces an irreversible switch to an expanding or
contracting universe. It is a little like trying to balance a pencil on its point:
although theoretically possible to do, it is in practice impossible. Einstein,
according to a later testimony by George Gamow, called the cosmological
constant the biggest blunder of his life [2].
In a letter to Georges LeMaître in 1947, Einstein wrote [3]: “I found it
distasteful having to accept that the equation for the gravitational field must be
put together out of two logically independent terms which are connected by addition. It is difficult to give arguments justifying such feelings, as I feel them in terms
of logical simplicity. But I cannot fight against feeling them with all my strength,
and I am not in a position to believe that such a repugnant thing could be realised
in nature.”
It may seem strange to a non-scientist to encounter concepts such as ugliness, and its antithesis, beauty, when dealing with works of science. However,
as we have seen in Chap. 3, scientists are often attracted by beauty or repelled
by ugliness in their theories and equations. We will examine further farreaching implications of this tendency in Chap. 12. Einstein’s dissatisfaction
with his introduction of the cosmological constant may well have resided with
its arbitrariness. In selecting a value to achieve a desired result, he is “tuning” his equations. The tuning of models by adjusting arbitrary parameters
is a common enough practice in some areas of science, but is not generally
regarded as good scientific practice.
Einstein, may have—or may not have, as there is some controversy about
what he actually said to Gamow—described the cosmological constant as his
greatest blunder, but that hasn’t prevented his successors reintroducing it to
account for dark energy, which we will come to in the next Chapter. Not
everybody is repelled by ugliness. Einstein was very modest about his achievements and freely admitted that he had committed other blunders. In a letter
to his friend and colleague, Max Born, Einstein wrote: “I too committed a
monumental blunder some time ago (my experiment on the emission of light with
199
time, the matter/energy density becomes infinite at a finite point in the past.
When he first proposed his theory, he considered such an infinite density to
be unphysical.
In order to achieve a steady-state universe, and avoid this expansion or
contraction, Einstein introduced an additional arbitrary term into his equations, known as the cosmological constant, Λ. For a stationary solution of
the equations to exist, this new constant had to be fine-tuned , i.e. it had
to have a very precise value. The new term is perfectly compatible with
General Relativity and mathematically consistent. However, any arbitrarily
small perturbation of the density of matter in the universe, or of the value of
the cosmological constant, produces an irreversible switch to an expanding or
contracting universe. It is a little like trying to balance a pencil on its point:
although theoretically possible to do, it is in practice impossible. Einstein,
according to a later testimony by George Gamow, called the cosmological
constant the biggest blunder of his life [2].
In a letter to Georges LeMaître in 1947, Einstein wrote [3]: “I found it
distasteful having to accept that the equation for the gravitational field must be
put together out of two logically independent terms which are connected by addition. It is difficult to give arguments justifying such feelings, as I feel them in terms
of logical simplicity. But I cannot fight against feeling them with all my strength,
and I am not in a position to believe that such a repugnant thing could be realised
in nature.”
It may seem strange to a non-scientist to encounter concepts such as ugliness, and its antithesis, beauty, when dealing with works of science. However,
as we have seen in Chap. 3, scientists are often attracted by beauty or repelled
by ugliness in their theories and equations. We will examine further farreaching implications of this tendency in Chap. 12. Einstein’s dissatisfaction
with his introduction of the cosmological constant may well have resided with
its arbitrariness. In selecting a value to achieve a desired result, he is “tuning” his equations. The tuning of models by adjusting arbitrary parameters
is a common enough practice in some areas of science, but is not generally
regarded as good scientific practice.
Einstein, may have—or may not have, as there is some controversy about
what he actually said to Gamow—described the cosmological constant as his
greatest blunder, but that hasn’t prevented his successors reintroducing it to
account for dark energy, which we will come to in the next Chapter. Not
everybody is repelled by ugliness. Einstein was very modest about his achievements and freely admitted that he had committed other blunders. In a letter
to his friend and colleague, Max Born, Einstein wrote: “I too committed a
monumental blunder some time ago (my experiment on the emission of light with