And now on with the shew.
Recently, I submitted a fairly lengthy comment to a creationist site in which I atempted to explain why most scientists accept the theory of the Big Bang. IMHO, my efforts need to be preserved for future reference, so here is an adaptation of that apologia.
Creationists and intelligent designists often object to the Big Bang theory as much as the theory of evolution. Both theories assume that the current state of life, the universe and everything resulted from a long series of random events over billions of years. Neither presupposes a Designer, since invoking supernatural causes is unscientific. Even Aristotle ages ago rejected the idea that gods pushed the sun, moon and planets around.
To understand the Big Bang theory requires some background into other, less all-encompassing scientific theories, as well as a willingness to visualize events that may be beyond our ability to visualize fully.
There are two major misunderstandings about the Big Bang, which are actually pretty common even among people who say they accept the theory.
Some object that the Big Bang implies that matter was created out of nothing, but they misunderstand what the theory states. Clearly, something had to be there in the beginning. I will explain this idea later.
Secondly, many people visualize the Big Bang as a titanic explosion that filled up an already extant space, as a firecracker explodes into the air. In fact, at the time of the Big Bang and shortly thereafter, the universe was incredibly small, incredibly compact, and highly energetic. There was nothing but the universe present. This concept is understandably hard to comprehend, as we are used to seeing things expand into a space that already exists. In the case of the Big Bang, it is the space itself that expanded into a void. Indeed, many scientists, including Stephen Hawking, contend both time and space began at the time of the Big Bang. The Big Bang theory does not speculate on what if anything might have existed other than the universe, since we have no way to observe those other things. Our observations are limited to the universe in which we live.
Here is the crux of the issue. The Big Bang, as with any scientific theory, depends on observational and experimental evidence. Without that evidence, a theory is mere speculation. As it is, a wide range of evidence in astronomy and particle physics supports the Big Bang. I will admit, however, that steady-state theorists contend the evidence supports their theory, though they are in the minority.
So what is that evidence? I will touch on only the most compelling, and at that only briefly. Entire books have been written about the Big Bang, after all.
Albert Einstein, 1905: The equivalence of mass and energy, E=mc-squared. This famous equation finally explained how stars could “burn” for millions, if not billions of years. Chemical and gravitational explanations predicted short stellar lifetimes. Einstein’s equation explains that the sun and stars convert mass into energy through nuclear fusion. The letter c in the equation is the speed of light — a huge number. So a tiny bit of mass goes a long way, and the sun has enough mass to shine for 10 billion years. We assume it is in its middle age now. The equation itself has been verified many, many times in earthbound experiments.
Albert Einstein, 1916: The theory of general relativity. One prediction of this theory is that matter warps space and time, creating gravity. Space is curved, in a sense. This concept has been verified observationally many times since 1919. Einstein’s original equations predicted an expanding universe. At the time, astronomers accepted the steady state universe, so Einstein famously “adjusted” his equations to match the current accepted cosmology. He later said it was the biggest blunder of his life.
Edwin Hubble, 1927: The expansion of the universe. Hubble was studying the light spectra of galaxies, and discovered their spectral lines (indicating elements) were shifted toward the red end of the spectrum (ROYGBIV). More distant galaxies had more pronounced redshifts. Thus, Einstein was in fact correct. The universe is expanding, presumably from a colossal explosion. Note that the galaxies are not expanding into an already existing volume. Rather, it is the space between them that is expanding.
Various, 19th to 20th century: The transmutation of elements. There are two kinds of atomic nuclear processes, fission and fusion. Each results in an entirely new nucleus, and thus element. In fission, a nucleus splits into lighter nuclei. For example, uranium decays into barium and krypton + energy. In fusion, two or more nuclei join (fuse) into heavier nuclei. For example, 4 hydrogen nuclei fuse into 1 helium nucleus + a lot of energy inside most stars. (Plutonium and the other transuranic elements are produced in just this way, artificially.) The Big Bang presumes the only elements around in the early universe were hydrogen and helium in roughly a 4 to 1 ratio, with trace amounts of lithium. The first generation of stars created the heavier elements through fusion and supernovae. Our sun is a second-generation star, since it contains other elements like calcium. (Stellar theory developed independently of the Big Bang theory, BTW.)
Arno Penzias and Robert Wilson, 1964: The cosmic background radiation (CBR). If the Big Bang happened, and if the space in the universe is expanding, then the original high energy radiation of the Big Bang should be now dramatically redshifted into microwave frequencies. That is what a group of Princeton astronomers had predicted in the early 1960s. Penzias and Wilson accidentally detected the CBR with a new, sensitive microwave receiver. Later observations have confirmed their observations and conclusions.
Our current theories of physics can take us back to a time just 10 to the -43 seconds after the Big Bang. We can essentially run the movie of the expanding universe backward. In that early universe, there was only energy, very high energy. As the universe expanded and cooled, energy “condensed” into protons, electrons and other particles. As it cooled further, those particles formed simple atoms, then molecules, then larger structures. So, it is not that matter just appeared from nothing. It arose from the energy of the early universe.
The Big Bang theory cannot answer what happened before that critical point in time, as our current physics is not up to the task. Superstring theories may provide some answers, but these theories are still immature.
The Bing Bang also does not attempt to answer why the universe began, an ultimate question that something other than science must address.
Part and parcel to the Big Bang theory is the Standard Model of Particles and Interactions. This model offers us four fundamental interactions (forces) between particles (matter). Each force is associated with a carrier particle; photons carry electromagnetism, for example. The early universe was so energetic that the four interactions were in fact only one. At this writing, physicists have been able to unify the two nuclear forces with electromagnetism into the electronuclear force. The particles responsible for carrying this force have been detected in particle accelerators, so we are sure this unification is a valid one.
The odd one out is gravity, the weakest of the interactions. Its carrier particle, the graviton, has not yet been detected. In addition, Einstein’s theory of general relativity, which conceptualizes gravity as a warping of space-time by matter, is inconsistent with the Standard Model, though it works exceedingly well. General relativity, for its part, predicts gravitational waves (which could have particle properties). These have not yet been detected, either.
So, the Standard Model is incomplete, and thus the Big Bang theory that depends on that model. Does that mean either is invalid? Not at all, since both work very well in explaining the past and current state of affairs and predicting later events, both hallmarks of solid scientific theories. In addition, there is ample corroborating evidence from other sciences that lead us to accept them. Unfortunately, to understand the Big Bang requires a reasonable understanding of those sciences, including chemistry, physics, geology, astronomy, and biology. It also requires a willingness to accept (1) that the evidence supports the theory and (2) that no theory is ever complete; there will always be questions to which there are no answers.
To accept these two simultaneously means you are in some sense a scientist. To reject them means you are a dogmatist.