I always recommend that Christians who want to make a positive case for Christian theism begin with the evidence that caused scientists to accept that the universe had a beginning. I don’t recommend stating the kalam argument, or any Bible verses, or any philosophical arguments. Instead, I recommend that they tell the story of how the evidence that led up to the discovery of the Big Bang cosmology was discovered. Who made the discoveries of the evidence, what was the evidence, when was it discovered, and how was it discovered.

Here’s Wallace’s post on it.

Excerpt:

The Second Law of Thermodynamics

This law (also known as the Law of Increased Entropy) recognizes the following: While the quantity of energy within a closed, isolated system (like the Universe) remains the same, the amount of usable energy deteriorates gradually over time. “Usable energy is inevitably used for productivity, growth and repair. In the process, usable energy is converted into unusable energy. Thus, usable energy is irretrievably lost in the form of unusable energy.”

Many of us have played with wind-up toys over the years. After toys of this nature are wound, there is a limited period of time in which we can enjoy them. Within a few seconds, wind-up toys slow down and stop; they run out of energy. Imagine walking into an empty room and discovering a wind-up toy sitting on the floor, still operating (unwinding). The discovery of this toy (and the fact it is still in the process of unwinding), would raise two reasonable inferences: (1) the toy was recently wound at a fixed point in the not-too-distant past, and (2) there was an adequate cause responsible for the initial winding. In other words, you would start looking for the “winder” somewhere in the room, given the fact the toy was still in the process of unwinding. We happen to be living in a “wind-up” universe slowly losing its usable energy. If the universe had no beginning and was infinitely old, why would there be any usable energy still available to us? The fact there is still usable energy in the universe points to a beginning in which the universe was tightly wound, and causes us to look for the cause responsible for such winding.

The Expansion of the Universe
Over the years, a number of scientists have calculated or observed the expansion of the universe. In 1905, Albert Einstein developed the Special Theory of Relativity involving measurements of length, velocity and time from moving observers. These equations led to the now famous E = mc2 equation, which describes how matter and energy can be converted from one form to another. In 1915, by applying relativity to Newtonian physics, Einstein derived the equations of general relativity which describe the relationships between gravity, the speed of light, mass, and other factors in regard to the universe as a whole. His work was consistent with an expanding universe. While this conclusion was initially troubling to Einstein, other mathematicians and scientists were coming to the same conclusion.

Alexander Friedman, a Russian mathematician working in the 1920’s with Einstein’s theories, used the mathematics to prove the universe is expanding. His work was being paralleled at the time by astronomers in Belgium who independently came to the same conclusion. An astronomer named Vesto Slipher presented findings at an obscure astronomy meeting in 1914 which showed that several ‘nebulae’ were receding away from the earth. A graduate student named Edwin Hubble was in attendance and realized the implications. Hubble later proved that these nebulae were actually galaxies, composed of billions of stars. In 1929 he proposed the law of red shifts. Galaxies which are moving away from the earth demonstrate emission spectra with bands shifted toward the red end of the spectrum, and Hubble observed these distant galaxies demonstrated this red shift phenomena. In essence, he proved by observation the universe is indeed expanding.

Our universe is expanding like a balloon. Imagine individual galaxies drawn on the balloon’s surface. As the edge of the balloon expands, the edge galaxies move away from center and away from each other. This is what we are seeing in our universe today. If we could go back in time and reverse the process (“deflate the balloon”), we would eventually arrive at an initial point of convergence. Once again, the science demonstrates our universe had a beginning.

The Radiation Echo
In 1964, two American physicists and radio astronomers, Arno Allan Penzias and Robert Woodrow Wilson, happened upon an important discovery. They were unable to eliminate the radio signal “noise” from their large antenna at the Bell Telephone Laboratories in New Jersey, regardless of where in the universe they tried to point their instrument. As a result, they began to consult with colleagues to determine the cause of this background noise. Phillip James Edwin Peebles, a physicist and theoretical cosmologist at Princeton University, suggested the noise might not be from the antenna at all. Instead, he proposed they might be detecting the residual “background radiation” caused when the universe first came into being. Penzias and Wilson pursued this line of investigation and confirmed Peebles’ suspicions. Numerous additional experiments and observations have since established the existence of cosmic background radiation (culminating in data from the Cosmic Background Explorer satellite launched in 1989). For many scientists, this discovery solidified their belief the universe had a beginning at a fixed point in the past.

Wallace gets these evidences from a book by famous agnostic astornomer Robert Jastrow, former head of the NASA Goddard Space Institute. The book is called “God and the Astronomers”. I have the second edition.

Wallace is working on a new book. Not much is known about it, but based on photos of the books he is reading, it’s something to do with cosmology. If he can write a book for Christians that’s as easy to read as his “Cold Case Christianity”, then we are really going to gain some ground in the culture. The more Christians understand the science of cosmology, the more likely the culture as a whole is going to be to respect the Creator and Designer of the universe.