Thermodynamics and the Universe
Here we will apply thermodynamics to the universe as a whole. We now know that the universe had a beginning. We will find the thermodynamic prerequisites for creation.
The Universe and Information Theory
Josiah Willard Gibbs (American mathematical physicist, 1839-1903) developed a way of calculating entropy even in situations so far from equilibrium that the concept of temperature is not valid. Shannon took over the Gibbs formulation of entropy and put a significant minus sign in front of it. The double negative Shannon created should really be considered in a sense opposite to that of the historical development of the theory. Information is primary and should be regarded as “positive” in the sense of the presence of something good. Entropy is the destruction of information.
In the flow of history of the universe, information came first. Somehow, at the beginning of the universe, an agent injected information into the universe in a way that designed and arranged the universe. That moment is therefore called the moment of creation. Since creation the universe is running down. The growth of entropy represents the gradual destruction of the universe.
In the flow of history of the universe, information came first. Somehow, at the beginning of the universe, an agent injected information into the universe in a way that designed and arranged the universe. That moment is therefore called the moment of creation. Since creation the universe is running down. The growth of entropy represents the gradual destruction of the universe.
Increasing Entropy and the End of the Universe
Thermodynamics played a decisive role in the dialogue we examined in The First Three Days of the Earth, whether the universe had a beginning or not. However, we did not mention thermodynamics explicitly then, because we hadn’t yet explained its concepts. We talked about the stars exhausting their fuel and about all processes running down to a “heat death” of the universe. Now we can say that the second law of thermodynamics makes this inevitable. Stars burn to ashes. The first stars burned hydrogen and made ashes of helium and heavier elements. Crushing the first ashes hard enough can make helium burn into more heavy elements. These ashes can be crushed a third time to become the fuel for a third kind of burning. But there is no way to continue these cycles indefinitely, always crushing ashes to make new fuel for new kinds of burning. Entropy is always increasing because of irreversible processes. But the entropy of the universe has not yet reached its maximum.[i] The fact that stars still have fuel to burn shows that entropy can still increase some more. The universe was clearly prepared in a state of low entropy.
A “hot primordial fireball” would have had high entropy, not low. That is why we rejected the popular but misleading “fireball” description of the initial state of the universe. The universe must have begun with its energy concentrated in quanta of very high order, which we suggest were cosmic rays of very high energy.
All nuclear reactions and all chemical reactions go in the direction of increasing entropy. Chemical reactions started when there were atoms. Previously, nuclear reactions started when there were nuclei. Prior to that, in the first instants of the universe, there were collisions of cosmic rays in the darkness. Rays of high energy have lower entropy than low energy rays, because they concentrate energy at a high frequency. When they split up into weaker rays and materialize as particles, their energy scatters into several forms. This scattered arrangement is the highly probable result of collisions between high-energy rays. It is very improbable that many low-energy rays and particles would come together simultaneously and concentrate themselves into a pair of high-energy rays. That is, the scattering of energy into many rays and particles is theoretically but not practically reversible. The least probable arrangement, the one with the fewest rays, has the lowest entropy. It also carries the most information, because one would have to specify the frequency to great precision, instead of saying that the energy was spread around in a range of frequencies. Therefore a single photon of very high energy can be much more complex even than a uranium atom with 92 electrons, 92 protons, and 143 or 146 neutrons.
The Sun became a source of low-entropy energy because gravity concentrated a low-entropy cold gas in a region of space. The universe had to start in a state of low entropy for this to occur.
The universe will dissipate its energy as heat of maximum entropy. Even if everything ends up in a black hole, the entropy will be enormous. The universe is not reversible and not cyclic.
[i] Lebowitz, Joel L., “Boltzmann’s Entropy and Time’s Arrow,” Physics Today, 46 (Number 9, September 1993), pp. 32–38.
A “hot primordial fireball” would have had high entropy, not low. That is why we rejected the popular but misleading “fireball” description of the initial state of the universe. The universe must have begun with its energy concentrated in quanta of very high order, which we suggest were cosmic rays of very high energy.
All nuclear reactions and all chemical reactions go in the direction of increasing entropy. Chemical reactions started when there were atoms. Previously, nuclear reactions started when there were nuclei. Prior to that, in the first instants of the universe, there were collisions of cosmic rays in the darkness. Rays of high energy have lower entropy than low energy rays, because they concentrate energy at a high frequency. When they split up into weaker rays and materialize as particles, their energy scatters into several forms. This scattered arrangement is the highly probable result of collisions between high-energy rays. It is very improbable that many low-energy rays and particles would come together simultaneously and concentrate themselves into a pair of high-energy rays. That is, the scattering of energy into many rays and particles is theoretically but not practically reversible. The least probable arrangement, the one with the fewest rays, has the lowest entropy. It also carries the most information, because one would have to specify the frequency to great precision, instead of saying that the energy was spread around in a range of frequencies. Therefore a single photon of very high energy can be much more complex even than a uranium atom with 92 electrons, 92 protons, and 143 or 146 neutrons.
The Sun became a source of low-entropy energy because gravity concentrated a low-entropy cold gas in a region of space. The universe had to start in a state of low entropy for this to occur.
The universe will dissipate its energy as heat of maximum entropy. Even if everything ends up in a black hole, the entropy will be enormous. The universe is not reversible and not cyclic.
[i] Lebowitz, Joel L., “Boltzmann’s Entropy and Time’s Arrow,” Physics Today, 46 (Number 9, September 1993), pp. 32–38.