Another reader suggested that believing in an eternal universe is no different from believing in God: "Neither is provable and both defy physical law as we know it. Am I missing something?"
Yes, said physicist Lawrence Krauss of Arizona State University, you really can get something from nothing and stay within the bounds of physical law.
"There are lots of ways for nothing to produce something," said Krauss, who wrote The Physics of Star Trek and will speak Wednesday at Philadelphia's Ethical Humanist Society. Nothing can even give rise to a whole lot of something, as he described in A Universe From Nothing.
First, you have to clearly define nothing, since it isn't an official scientific term. Scientists talk about empty space as well as a state in which space and time themselves don't exist. Either type of nothing can spontaneously produce stuff.
Empty space, as it turns out, can't be perfectly empty. Every type of matter has an equal and opposite counterpart, and pairs of particles and their anti-particles can spontaneously emerge from empty space and then disappear again.
One consequence of quantum mechanics' uncertainty principle is that a vacuum cannot remain perfectly empty forever. Not only will particles pop in and out of existence without violating the laws of physics, they have to.
How to get a whole universe to burst out of nothing is harder to explain. Scientists have multiple lines of evidence showing that our universe is expanding out of a so-called big bang. There's still disagreement on the details, but the big bang theory made specific predictions about the proportions of hydrogen, helium and lithium in the universe, which we can measure, and the presence of radiation known as the cosmic microwave background, which is also measurable.
It's not a matter of faith.
