Subsequent conversations with people of all ages have shown me that many individuals (1) don't really understand what the Big Bang is, (2) don't know the scientific evidence for the Big Bang, and (3) don't comprehend the theistic significance of the Big Bang. So let's explore these ideas a little bit. The ultimate conclusion for me is that the Big Bang is among the very best objective evidence available for the existence of God, and is consistent with the biblical record. Many of you readers probably already know much of what follows, but maybe you will find something of interest anyway.
About a hundred years ago, there was no scientific evidence suggesting anything about the origin of the universe. Most scientists believed that the universe was eternal and infinite, it has always existed and spatially had no boundary. But in 1929, Edwin Hubble discovered that all galaxies were moving away from each other, and galaxies farthest apart were moving away from each other at a faster rate. This suggests that the universe is expanding, and if you were able to run the film of the history of the universe backward, you would find that at one point in time the entire visible universe must have been compressed into a very small size and must have started to expand. That is, it must have had a beginning. Most scientists were reluctant to accept that the universe had a beginning. In fact the term "Big Bang" was initially a derogatory term, invented by the physicist Fred Hoyle in 1955 because he thought the universe had always existed. He seemed to believe that if the name for the beginning of the universe was so ludicrous then maybe no one would accept either the name or the event. It seems that Fred Hoyle was trying to say to fellow scientists that, to him, the Big Bang should be disdained.
But scientist eventually came to accept the Big Bang model for the origin of the universe. The reason that this repugnant idea was accepted is because the evidence is overwhelming and indisputable. There are three primary observations that are best explained by the Big Bang. First, the universe is expanding so that it must have had a beginning of expansion in the past. Second, because the universe was once very hot, we can still see the remnants of that heat in the Cosmic Microwave Background (CMB) radiation. The latest measurements of the CMB spectrum made by the Planck satellite (shown above) agrees almost perfectly with theoretical calculations using the standard Big Bang cosmological model (see the plot at the end of this post). Third, the theory predicts the amount of primordial light elements that should have been created in the first few minutes of the Big Bang, like hydrogen and helium. Again the observations and the theoretical calculations align almost exactly. A few other observations are supported by Big Bang predictions, like the distribution of galaxies and primordial gas. The agreement between what we measure and what is expected from a Big Bang is so remarkable that just about all scientists accept the Big Bang as the origin of our universe, despite its implication that the universe had a beginning.
Now, I haven't been totally honest with you about the Big Bang because scientists actually use the term to mean different things depending on who you talk with. There are basically two alternatives. Some scientists refer to the Big Bang only from the moment of time that we actually have a good idea of what happened in the universe. That could be some time from about 10-35 to 10-12 seconds after the "origin" of the universe. With this definition, there is little controversy about the events surrounding the Big Bang. Other scientists, however, use the term to mean the actual moment the universe came into existence, what is sometimes referred to as a "singularity." With such a definition of the Big Bang, there is a huge controversy since no one has any observational evidence about what occurred in the first trillionth of a trillionth of a trillionth of a second of the universe. When you hear scientists debating whether or not the Big Bang actually occurred they are only questioning what happened in the first 10-35 seconds or so and whether or not there was an actual beginning. They are not questioning whether the visible universe was very small, hot, and dense about 13.8 billion years ago and has been expanding ever since. But many scientists still don't like the theological and philosophical implication of a universe that had an actual beginning and continue to look for loopholes.
Because we don't have any observations that tell us exactly what happened "in the beginning" of our universe, we can only speculate. But let me point out the obvious. All of the observations we do have, and all the theoretical calculations, and even some projective calculations like the Borde-Guth-Vilenkin theorem (which I should probably blog about at some time) give credence to the conclusion that all of the space, time, matter, and energy of this universe had a beginning. The Big Bang is a misnomer for it is not some kind of explosion since there was nothing that existed to explode. It is the origin of the universe. So if this universe had a beginning, then the cause of the universe can not be a part of the universe. The cause must be transcendent, like the Christian idea of God. Is the fact that all the evidence points to our universe having a transcendent cause proof for God? No, but it is extremely powerful evidence. If one hundred years ago you had predicted that scientists would obtain unambiguous evidence about the history of the universe for 13.8 billion years, all of its lifetime except the first fraction of a second, and that all of the evidence would point to an actual beginning consistent with a transcendent cause, I don't think anyone would have taken you seriously. But that is exactly what has happened. Theists could not have outlined a better scenario to support theism. The scientific facts are completely consistent with the statement, "In the beginning God created the heavens and the earth."
Arno Penzias, one of the two astronomers who discovered the CMB said, "The best data we have are exactly what I would have predicted, had I had nothing to go on but the five books of Moses, the Psalms, the Bible as a whole." The Big Bang really is a theistic theory to be understood and embraced, not disdained. In future blogs I'll discuss the remarkable agreement between scientific discoveries and the account of creation in Genesis.
Below, I've attached a couple figures from the Planck satellite showing their measurement of the CMB.
This is a picture of the entire sky taken by the Planck satellite and tells us what the universe was like about 380,000 years after it began. The different colors are slight variations in temperature of about 1 part in 100,000. These minor temperature fluctuations eventually led to the large scale galactic structure we see.
This is a fit to the temperature fluctuations in the sky at different angular scales. The points are the data and the curve is the prediction from the theory based on the standard Big Bang model. Note how well they agree.