There could never have been a time at which nothing existed. If there was never a time at which nothing existed, then it's not the case that "once there was nothing, and then there was something". Atheists are not forced to explain how something can come from nothing, because nothing never existed.
"From Eternity to Here" offers an expertly thorough exploration of the nature of time, covering a wide range of concepts in theoretical physics in exquisite detail. The major focus is on time's relation to thermodynamics and entropy, but Carroll goes above and beyond the basic considerations and takes the reader on a journey touching upon a plethora of mysteries in modern physics.
Carroll explores what our intuitive understanding of time is, and how physics in the form of relativity and thermodynamics offer a deeper understanding of how time's arrow arises. Beginning with the simple observation that eggs can be made into omelettes but omelettes can't easily be made into eggs, Carroll takes us on a scientific roller-coaster all the way to the multiverse.
One of the most common headlines I see in popular science articles is "Was Einstein Wrong?". While it is certainly true that relativity is going to be replaced by some more advanced theory of physics at some stage, the basis of Einstein's theory is unlikely to change.
This is why I say that the universe must contain time. The universe is best thought of as a static 4-dimensional shape of which slices are all we can perceive. What really bites is that we all perceive different slices of this 4-dimensional shape, and how would that be possible if the universe were only 3D?
While I can find no fault with the deductive validity of this argument - the conclusion certainly seems to follow from the premises - I'm afraid this is as successful as the argument gets. Not just one, but both of the premises commit logical fallacies which they hide in the vagueness of their formulation.
To anyone who is confused about what it is exactly that theoretical physicists do, here is a brief yet broad summary of what we're trying to achieve.
It is not difficult to find online forums and blog posts that proclaim facts and arguments as if they were certain. People of all philosophical alignments will do this. Theists will proclaim what they believe to be indisputable facts like: "Something must have caused the Big Bang", and atheists are often guilty of prophetically declaring their favourite origin story for the universe: "Quantum fluctuations produced the universe" or "Many-worlds explains fine-tuning".
There is a split in the philosophical community with regards to this issue. By and large, the majority of philosophers of physics claim that space and time are real and important entities, but there is a small faction who maintain that space and time are just useful theoretical constructs that don't have the independent existence we sometimes attribute to them.