Many of those who do not practice any religion and see no merit in traditional God-beliefs still find it hard to be full-fledged atheists. Although not religious in the usual sense, these nonbelievers have not yet completely freed themselves from all religious or metaphysical notions, most of which have no rational foundation. They will tell you that they intuitively feel that something still must be "out there," some power that is responsible for the universe and the laws that govern it. After all, they ask, "How can something come from nothing?"
One such religious notion is the story of creation: Once upon a time there was nothing and then, miraculously, there was something. But, is that the only possibility? Why couldn't there always have been something? If there never was a transition nothing-to-something, it follows there was no creation and, therefore, no creator, personal or otherwise.
Of course, creation ex nihilo, the creation of the universe out of nothing, is a major component of virtually all religious belief. On the other hand, modern cosmology suggests that the universe was not created, that it is eternal in time.
Theologians, theist authors, and debaters have developed several arguments that they maintain proves that the universe can't be eternal, that it had to have a beginning. I will start with the frequently heard claim that an eternal universe can't exist for mathematical reasons. The argument made is that in an infinite universe it would take an infinite time to reach from the beginning to the present.
However, this is a strawman that exploits the fact that most scientists as well as laypeople improperly use the term "infinity" when they really mean endless or unlimited. An eternal universe is not the same as an infinite universe. Time is the number of ticks on a clock. In the eternal universe that number is endless, not infinite. Counting backwards in time, the eternal universe has no beginning -- not a beginning an infinite time ago. The time interval from any moment in the past to the present is finite. So an eternal universe is mathematically possible.
The second argument for a cosmic creation that theologians and Christian apologists have been using for decades now is that the universe, and time itself, began with a singularity identified with the big bang. This singularity is a point in space-time of unlimited density. This claim is based on a theorem derived from Einstein's general relativity and published by Stephen Hawking and Roger Penrose in 1970, which concluded that the universe began with a singularity.
Over 20 years ago now, Hawking and Penrose admitted that there was no singularity because their calculation, while not wrong as far as it went, had not taken into account quantum mechanics. See page 50 of Hawking's 1988 bestseller A Brief History of Time. I do not know of a single working cosmologist today who says the universe began with a singularity.
Some Christian authors and debaters also refer to other more recent calculations claiming these require the universe to have a beginning. To give the shortest possible rebuttal, I will just quote the Cal Tech cosmologist Sean Carroll, who wrote me in an email: "No result derived on the basis of classical general relativity can be used to derive anything truly fundamental, since classical general relativity isn't right. You need to quantize gravity."
So the universe need not have had a beginning. But let's suppose for a moment that it did. That fact alone would not prove it was purposefully created. Another premise must be made to show that. The assumption must be added that everything that begins has a cause. Once again, this ignores quantum mechanics, where events commonly occur without cause. This is the case for the atomic transitions that give us light and the nuclear decays that give us nuclear radiation. They all happen spontaneously, without cause. In short, all attempts to prove that the universe had to have a beginning caused by God fail on several fronts.
The third creationist argument called the anthropic cosmological principle, made by a whole army of Christian theologians and authors, is that the universe is fine-tuned for life, in particular, human life. Here the story is even more complicated because several notable physicists think such fine-tuning does exist, although they attribute it to natural causes rather than a creator God. I identify with an opposition group of physicists who see no need to invoke the anthropic principle at all. We can offer natural explanations for all the values of all parameters claimed to be fine-tuned (see The Fallacy of Fine-Tuning, in press).
The claims that evidence for a cosmic creation can be found in physical observations are based on a gross misunderstanding of basic physics. Several theist authors have carelessly lifted out of context a quotation from Hawking's A Brief History of Time:
If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, the universe would have collapsed before it ever reached its present size. (pp, 121-122)
This is presented as an example of the incredible fine-tuning of the universe. However, those making that claim ignore Hawking's explanation seven pages later for why no fine-tuning was needed. There he describes the inflationary cosmological model, in which the universe began with a tiny period of very rapid, exponential expansion. While still new in 1988, inflationary cosmology is now well-established. Hawking says,
[In the inflationary model] the rate of expansion of the universe would automatically become very close to the critical rate determined by the energy density of the universe. This could then explain why the rate of expansion is still so close to the critical rate, without having to assume that the initial rate of expansion of the universe was very carefully chosen. (p. 128)
So the rate of expansion of the universe is not fine-tuned at all. Its value is exactly what it should be.
This is only one of the thirty or so other parameters that theists claim were fine-tuned by God. Reasonable explanations based on known physics and cosmology can be given for them all. Computer simulations show that some kind of life is possible in universes over a wide range of parameters.
The erroneous claims I have discussed here are widely disseminated in Christian literature and appear frequently in debates and discussions on religion and science. They are rarely challenged by scientists who have the necessary technical knowledge required to discern the validity of arguments based on mathematics, physics, or cosmology. Instead these scientists choose to remain outside the fray. The unwillingness of most scientists to engage in the very real war between science and religion is handing victory to religion by default.