A Universe from Nothing: Why There Is Something Rather than Nothing

by Lawrence Krauss

The fact that we need to refine what we mean by “common sense” in order to accommodate our understanding of nature is, to me, one of the most remarkable and liberating aspects of science.

1. In quantum gravity, universes can, and indeed always will, spontaneously appear from nothing. Such universes need not be empty, but can have matter and radiation in them, as long as the total energy, including the negative energy associated with gravity, is zero. 2. In order for the closed universes that might be created through such mechanisms to last for longer than infinitesimal times, something like inflation is necessary. As a result, the only long-lived universe one might expect to live in as a result of such a scenario is one that today appears flat, just as the universe in which we live appears.

I don’t make any claims to answer any questions that science cannot answer,

don’t discount the remarkable human adventure that is modern science because it doesn’t console you.

A world without God or purpose may seem harsh or pointless, but that alone doesn’t require God to actually exist.

The Initial Mystery that attends any journey is: how did the traveler reach his starting point in the first place? —LOUISE BOGAN, Journey Around My Room

Since the universe has a finite age (recall it is 13.72 billion years old),

Moving Einstein’s term from the left-hand side of his equations to the right-hand side is a small step for a mathematician but a giant leap for a physicist.

The particles that appear and disappear in timescales too short to measure are called virtual particles.

This is what makes a flat universe so special. In such a universe the positive energy of motion is exactly canceled by the negative energy of gravitational attraction.

we need to have some cosmic humility in our claims, even if such a thing is difficult for cosmologists.

Once you assume a creator and a plan, it makes humans objects in a cruel experiment whereby we are created to be sick and commanded to be well. —CHRISTOPHER HITCHENS

A number of central ideas that drive much of the current activity in particle theory today appear to require a multiverse.

A truly open mind means forcing our imaginations to conform to the evidence of reality, and not vice versa, whether or not we like the implications.

I don’t mind not knowing. It doesn’t scare me. —RICHARD FEYNMAN

Indeed, I have challenged several theologians to provide evidence contradicting the premise that theology has made no contribution to knowledge in the past five hundred years at least, since the dawn of science. So far no one has provided a counterexample. The most I have ever gotten back was the query, “What do you mean by knowledge?” From an epistemological perspective this may be a thorny issue, but I maintain that, if there were a better alternative, someone would have presented it. Had I presented the same challenge to biologists, or psychologists, or historians, or astronomers, none of them would have been so flummoxed.

in a flat universe, and only in a flat universe, the average Newtonian gravitational energy of every object participating in the expansion is precisely zero.

The Newtonian gravitational energy of galaxies moving along with the Hubble expansion is zero—like it or not.

General relativity tells us that space will expand exponentially, so that even the tiniest region at early times could quickly encompass a size more than large enough to contain our whole visible universe today.

Science simply forces us to revise what is sensible to accommodate the universe, rather than vice versa.

Virtual particles are manifestations of a basic property of quantum systems. At the heart of quantum mechanics is a rule that sometimes governs politicians or CEOs—as long as no one is watching, anything goes. Systems continue to move, if just momentarily, between all possible states, including states that would not be allowed if the system were actually being measured. These “quantum fluctuations” imply something essential about the quantum world: nothing always produces something, if only for an instant.

under the right conditions, not only can nothing become something, it is required to.

there are roughly 1 billion photons in the cosmic microwave background for every proton in the universe.

Having a quantum theory of gravity would therefore mean that the rules of quantum mechanics would apply to the properties of space and not just to the properties of objects existing in space, as in conventional quantum mechanics.

1. In quantum gravity, universes can, and indeed always will, spontaneously appear from nothing. Such universes need not be empty, but can have matter and radiation in them, as long as the total energy, including the negative energy associated with gravity, is zero. 2. In order for the closed universes that might be created through such mechanisms to last for longer than infinitesimal times, something like inflation is necessary. As a result, the only long-lived universe one might expect to live in as a result of such a scenario is one that today appears flat, just as the universe in which we live appears.

“out of nothing nothing comes,” has no foundation in science.

Jacob Bronowski: Dream or nightmare, we have to live our experience as it is, and we have to live it awake. We live in a world which is penetrated through and through by science and which is both whole and real. We cannot turn it into a game simply by taking sides.

Without science, everything is a miracle. With science, there remains the possibility that nothing is.

Biology was always the favorite hunting ground for natural theologians until Darwin—not deliberately, for he was the kindest and gentlest of men—chased them off. They fled to the rarefied pastures of physics and the origins of the universe, only to find Lawrence Krauss and his predecessors waiting for them.

combining quantum mechanics with gravity allows stuff to arise from no-stuff.

There are questions we can address effectively via empirical methods and questions we can ask that don’t lead to physical insights and predictions. The trick is to tell the difference between the two.

What do you mean by “flat”? Is the universe flat as a pancake? I wish I had described this a little more carefully in the hardcover edition, and I have expanded the discussion in this edition. A flat three-dimensional space is just the kind of space you already thought you lived in, where light rays travel in straight lines, and perpendicular axes (x,y, and z) remain perpendicular. In curved three-dimensional spaces neither statement is true. Since mass and energy can curve space locally (i.e., around the sun and earth for example), the big question is what about the global structure of space on the largest scales: Is it curved or not? And it turns out on the largest observable scales, it isn’t. And that fact is very telling, as I describe in the book, because it is what one would expect from a universe that arose from nothing.

the greatest thing about science is that our faith is shakable. At any moment we can give up believing in anything we once believed in, if nature suggests otherwise.