EPILOGUE 293
the universe was static and unchanging. So Einstein, bowing to the observations of the astronomers, added the cosmological constant, an
antigravity force that pushed the stars apart to balance the gravitational pull causing the universe to collapse. (This antigravity force corresponded to the energy contained within the vacuum. In this picture
even the vast emptiness of space contains large quantities of invisible
energy.) This constant would have to be chosen very precisely in order
to cancel out the attractive force of gravity.
Later, when Edwin Hubble showed in 1929 that the universe was,
in fact, expanding, Einstein would say that the cosmological constant
was his "greatest blunder." Yet now, seventy years later, it appears as if
Einstein's "blunder," the cosmological constant, could in fact be the
largest source of energy in the universe, making up 73 percent of the
matter-energy content of the universe. (By contrast, the higher elements that make up our bodies constitute only .03 percent of the universe.) Einstein's blunder will likely determine the ultimate fate of the
universe.
But where does this cosmological constant come from? At present
no one knows. At the beginning of time, the antigravity force was perhaps large enough to cause the universe to inflate, creating the big
bang. Then it suddenly disappeared, for reasons that are unknown.
(The universe was still expanding during this period, but at a slower
pace.) And then, about eight billion years after the big bang, the antigravity force resurfaced again, causing the galaxies to push out and
causing the universe to accelerate once again.
So is it "impossible" to determine the ultimate fate of the universe?
Perhaps not. Most physicists believe that quantum effects ultimately
determine the size of the cosmological constant. A naïve calculation,
using a primitive version of the quantum theory, shows that the cosmological constant is off by a factor of 10
120 . This is the greatest mismatch in the history of science.
But there is also a consensus among physicists that this anomaly
simply means that we need a theory of quantum gravity. Since the cosmological constant arises via quantum corrections, it is necessary to
the universe was static and unchanging. So Einstein, bowing to the observations of the astronomers, added the cosmological constant, an
antigravity force that pushed the stars apart to balance the gravitational pull causing the universe to collapse. (This antigravity force corresponded to the energy contained within the vacuum. In this picture
even the vast emptiness of space contains large quantities of invisible
energy.) This constant would have to be chosen very precisely in order
to cancel out the attractive force of gravity.
Later, when Edwin Hubble showed in 1929 that the universe was,
in fact, expanding, Einstein would say that the cosmological constant
was his "greatest blunder." Yet now, seventy years later, it appears as if
Einstein's "blunder," the cosmological constant, could in fact be the
largest source of energy in the universe, making up 73 percent of the
matter-energy content of the universe. (By contrast, the higher elements that make up our bodies constitute only .03 percent of the universe.) Einstein's blunder will likely determine the ultimate fate of the
universe.
But where does this cosmological constant come from? At present
no one knows. At the beginning of time, the antigravity force was perhaps large enough to cause the universe to inflate, creating the big
bang. Then it suddenly disappeared, for reasons that are unknown.
(The universe was still expanding during this period, but at a slower
pace.) And then, about eight billion years after the big bang, the antigravity force resurfaced again, causing the galaxies to push out and
causing the universe to accelerate once again.
So is it "impossible" to determine the ultimate fate of the universe?
Perhaps not. Most physicists believe that quantum effects ultimately
determine the size of the cosmological constant. A naïve calculation,
using a primitive version of the quantum theory, shows that the cosmological constant is off by a factor of 10
120 . This is the greatest mismatch in the history of science.
But there is also a consensus among physicists that this anomaly
simply means that we need a theory of quantum gravity. Since the cosmological constant arises via quantum corrections, it is necessary to