Expansion Preserves Order
Both COBE and WMAP photographed the first light in all directions, making a sky map of the early universe. There is a serious scientific puzzle about the first light. It is of nearly uniform temperature, to within a few tens of parts per million. Something had to make it uniform. In particular, there are regions or spots with the same temperature.
We know that random collisions between gas molecules usually establish the temperature of the gas. Gas molecules move at random speeds. The average speed is comparable with the speed of sound in the gas. The speed of sound is much less than the speed of light. Therefore establishing thermal equilibrium in a region of gas takes much longer than the time light takes to pass across the region once.
The warm spots in the cosmic background are typically one degree across and the distance to them is 13 820 million light years. Therefore their diameters are about 240 million light years. It should have taken much longer than 240 million years for random collisions to establish a uniform temperature in the spots. But the postulated age of the universe at the time was only 380 thousand years. Even if there were some physical mechanism that could establish thermal equilibrium with one pass across the spots at the speed of light, it would have taken 240 million years to operate. But in a little more than the thousandth part of that time the job was done! The spots appear to defy physical causality, but there they are!
There is a related point. The temperature is very nearly uniform throughout the early sky. Suppose we look in any given direction and measure the sky temperature, compensating for the motion of the Earth. When we look in the exact opposite direction, the temperature is the same to within a part in 50 000. Yet it would take many times twice the age of the universe for the two opposite points to reach thermal equilibrium, because no physical effect can propagate faster than the speed of light.
Before discussing the simplest solution, we will explain a much more complicated solution that is part of the present climate of opinion among physicists.
Inflation Soon After the Beginning
Some theories say that the organization of dense and rarefied regions appeared the tiniest fraction of a second after the gamma rays collided. The theories say that a physical change in the hot material of the early universe produced the fluctuations and incidentally set the rate of expansion.
When water is put on to boil, bubbles of vapor appear in it. These drive a rapid expansion of the water as steam. Conversion from water to steam is called a phase change.
Alan Guth published an inflation theory[i] in 1981 to explain why the universe expands at a finely adjusted rate. Later he published popular versions.[ii]–[iii] Guth proposed that some sort of phase change could have driven rapid inflation when the universe was very new. The spots had already reached thermal equilibrium in very small regions, and then the regions suddenly inflated by a huge factor. He proposed that the age of the universe at the beginning of inflation was between 1 micro-micro-micro-microsecond and 10 micro-micro-microseconds old.
In Guth’s theory the rate of growth has to be much faster than the speed of light.
That in itself makes some scientists say that inflation theory violates causality. A few other theoreticians have proposed that the speed of light was much faster at the beginning. Until there were atoms, we have no way of determining the speed of light. Was the speed of light variable at the beginning, and did it settle down to a constant value just before people could begin to check up on it? The assumption seems gratuitous. Does light act like speeders when they enter the “halo zone” around a police car?
The photographs do not show how long the uniform regions took to grow to the sizes we see. Though the photographs seem like a confirmation of Guth’s inflation theory, we must remember that the idea that the universe was 380 000 years old when it emitted the first light is a deduction based on a certain model. A simpler idea is that the universe was much older than 240 million years at the time, and that the equilibrium came about without any inflation or expansion faster than the speed of light.
Whatever the age of the universe was when thermal processes established its equilibrium temperature, the subsequent expansion preserved that established order. This is another reason for avoiding the term “Big Bang.” The universe did not explode at the beginning. It expanded in an orderly way. The Bible says five times in Genesis 1:6‑8 that God put expansion in the heavens. The expansion preserved the order we see in the photographs of the first light.
The Expansion Rate is Finely Tuned
We now know that the rate of expansion was finely tuned to produce a habitable universe. Einstein’s theory of general relativity allows physicists to calculate the critical rate of expansion. The critical rate is the slowest possible rate that allows the galaxies to expand forever to infinite distances from one another.
[i] Guth, A. H., “Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems,” Physical Review D, 23 (Number 2, 15 January 1981), pp. 347–356.
[ii] Guth, A. H. and P. J. Steinhardt, “The Inflationary Universe,” Scientific American, 250 (Number 5, May 1984), pp. 116–127.
[iii] Guth, A. H., The Inflationary Universe (Reading, Massachusetts, Addison-Wesley, 1997).
We know that random collisions between gas molecules usually establish the temperature of the gas. Gas molecules move at random speeds. The average speed is comparable with the speed of sound in the gas. The speed of sound is much less than the speed of light. Therefore establishing thermal equilibrium in a region of gas takes much longer than the time light takes to pass across the region once.
The warm spots in the cosmic background are typically one degree across and the distance to them is 13 820 million light years. Therefore their diameters are about 240 million light years. It should have taken much longer than 240 million years for random collisions to establish a uniform temperature in the spots. But the postulated age of the universe at the time was only 380 thousand years. Even if there were some physical mechanism that could establish thermal equilibrium with one pass across the spots at the speed of light, it would have taken 240 million years to operate. But in a little more than the thousandth part of that time the job was done! The spots appear to defy physical causality, but there they are!
There is a related point. The temperature is very nearly uniform throughout the early sky. Suppose we look in any given direction and measure the sky temperature, compensating for the motion of the Earth. When we look in the exact opposite direction, the temperature is the same to within a part in 50 000. Yet it would take many times twice the age of the universe for the two opposite points to reach thermal equilibrium, because no physical effect can propagate faster than the speed of light.
Before discussing the simplest solution, we will explain a much more complicated solution that is part of the present climate of opinion among physicists.
Inflation Soon After the Beginning
Some theories say that the organization of dense and rarefied regions appeared the tiniest fraction of a second after the gamma rays collided. The theories say that a physical change in the hot material of the early universe produced the fluctuations and incidentally set the rate of expansion.
When water is put on to boil, bubbles of vapor appear in it. These drive a rapid expansion of the water as steam. Conversion from water to steam is called a phase change.
Alan Guth published an inflation theory[i] in 1981 to explain why the universe expands at a finely adjusted rate. Later he published popular versions.[ii]–[iii] Guth proposed that some sort of phase change could have driven rapid inflation when the universe was very new. The spots had already reached thermal equilibrium in very small regions, and then the regions suddenly inflated by a huge factor. He proposed that the age of the universe at the beginning of inflation was between 1 micro-micro-micro-microsecond and 10 micro-micro-microseconds old.
In Guth’s theory the rate of growth has to be much faster than the speed of light.
That in itself makes some scientists say that inflation theory violates causality. A few other theoreticians have proposed that the speed of light was much faster at the beginning. Until there were atoms, we have no way of determining the speed of light. Was the speed of light variable at the beginning, and did it settle down to a constant value just before people could begin to check up on it? The assumption seems gratuitous. Does light act like speeders when they enter the “halo zone” around a police car?
The photographs do not show how long the uniform regions took to grow to the sizes we see. Though the photographs seem like a confirmation of Guth’s inflation theory, we must remember that the idea that the universe was 380 000 years old when it emitted the first light is a deduction based on a certain model. A simpler idea is that the universe was much older than 240 million years at the time, and that the equilibrium came about without any inflation or expansion faster than the speed of light.
Whatever the age of the universe was when thermal processes established its equilibrium temperature, the subsequent expansion preserved that established order. This is another reason for avoiding the term “Big Bang.” The universe did not explode at the beginning. It expanded in an orderly way. The Bible says five times in Genesis 1:6‑8 that God put expansion in the heavens. The expansion preserved the order we see in the photographs of the first light.
The Expansion Rate is Finely Tuned
We now know that the rate of expansion was finely tuned to produce a habitable universe. Einstein’s theory of general relativity allows physicists to calculate the critical rate of expansion. The critical rate is the slowest possible rate that allows the galaxies to expand forever to infinite distances from one another.
[i] Guth, A. H., “Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems,” Physical Review D, 23 (Number 2, 15 January 1981), pp. 347–356.
[ii] Guth, A. H. and P. J. Steinhardt, “The Inflationary Universe,” Scientific American, 250 (Number 5, May 1984), pp. 116–127.
[iii] Guth, A. H., The Inflationary Universe (Reading, Massachusetts, Addison-Wesley, 1997).