THE ANSWER to the question, “Did the universe have a beginning?” is, “It probably did.” We have no viable models of an eternal universe. The BGV theorem gives us reason to believe that such models simply cannot be constructed. More.
He offers the Borde-Guth-Vilenkin (BGV) theorem by way of evidence:
Loosely speaking, our theorem states that if the universe is, on average, expanding, then its history cannot be indefinitely continued into the past. More precisely, if the average expansion rate is positive along a given world line, or geodesic, then this geodesic must terminate after a finite amount of time. Different geodesics, different times. The important point is that the past history of the universe cannot be complete.
An outline of a mathematical proof of BGV is appended to the article.
Vilenkin goes on to assert that
Modern physics can describe the emergence of the universe as a physical process that does not require a cause.
If all the conserved numbers of a closed universe are equal to zero, then there is nothing to prevent such a universe from being spontaneously created out of nothing. And according to quantum mechanics, any process which is not strictly forbidden by the conservation laws will happen with some probability.
A newly-born universe can have a variety of different shapes and sizes and can be filled with different kinds of matter. As is usual in quantum theory, we cannot tell which of these possibilities is actually realized, but we can calculate their probabilities. This suggests that there could be a multitude of other universes.
The theory of quantum creation is no more than a speculative hypothesis. It is unclear how, or whether, it can be tested observationally. It is nonetheless the first attempt to formulate the problem of cosmic origin and to address it in a quantitative way.
Apologist William Lane Craig takes issue with the argument (2017):
Grant the supposition that the positive energy associated with matter is exactly counter-balanced by the negative energy associated with gravity, so that on balance the energy is zero. Vilenkin’s key move comes with the claim that in such a case “there is nothing to prevent such a universe from being spontaneously created out of nothing.” Now this claim is a triviality. Necessarily, if there is nothing, then there is nothing to prevent the universe from coming into being. By the same token, if there is nothing, then there is nothing to permit the universe to come into being. If there were anything to prevent or to permit the universe’s coming into being, then there would be something, not nothing. If there is nothing, then there is nothing, period.
Vilenkin, however, infers that “no cause is needed” for the universe’s coming into being because the conservation laws would not prevent it and “according to quantum mechanics, any process which is not strictly forbidden by the conservation laws will happen.” (Vilenkin assumes that if there were nothing, then both the conservation laws and quantum physical laws would still hold. This is far from obvious, however, since in the absence of anything at all, it is not clear that the laws governing our universe would hold.) But even granted that the laws would still hold, why think that, given the laws of quantum mechanics, anything not strictly forbidden by the conservation laws will happen? … the conservation laws do not strictly forbid something’s coming into existence, but neither do they forbid nothing’s coming into existence, but both cannot happen. It is logically absurd to think that because something is not forbidden by the conservation laws, it will therefore happen.
Finally, Vilenkin’s inference that because the positive and negative energy in the universe sum to zero, therefore no cause of the universe’s coming into being is needed is hard to take seriously. This is like saying that if your debts balance your assets, then your net worth is zero, and so there is no cause of your financial situation! More.
We likely haven’t heard the last of this question but it is nice to see it debated outside of the three-ring circus of crackpot cosmology.
See also, other philosophical questions; Did the universe never have a chance?
Does the size of the universe sweep us toward atheism?
Philosopher: If there is something rather than nothing, questions around God cannot be ignored Waghorn: “Firstly, that on the most plausible demarcation criterion for science, science is constitutionally unable to show theism to be a redundant hypothesis; the debate must take place at the level of metaphysics. ”
Is zero even?
Absolute zero proven mathematically impossible?
Is celeb number pi a “normal” number? Not normal. And things get worse. Surely this oddity is related in some way to the unreasonable effectiveness of mathematics.
Durston and Craig on an infinite temporal past . . .
Physicist David Snoke thinks that Christians should not use the kalaam argument for God’s existence
Must we understand “nothing” to understand physics?
Why is space three dimensions anyway? Why not six? A new theory is offered. They want to test their theory? What a great idea! In an age of wars on falsifiability, that’s a refreshingly new/old idea.