A Universe from Nothing

By Lawrence M. Krauss & Richard Dawkins

11 min read

Why does it matter? Because the question 'why is there something rather than nothing?' has already been answered — just not by theology.

For most of human history, the question

The Universe You Think You Understand Is 99% Invisible

Everything you've ever seen — every star, planet, ocean, and face — adds up to roughly 1% of what the universe actually contains. The other 99% is invisible, and figuring out what it is has become the defining obsession of modern cosmology.

The first crack in the comfortable picture came from Vera Rubin in the 1970s. Rubin measured the rotation speeds of stars at the outer edges of galaxies and found something that flatly contradicted what physics predicted. If a galaxy's gravity comes from the matter you can see, stars at the rim should orbit slowly, the way Neptune crawls around the Sun compared to Mercury. Instead, Rubin's stars were moving far too fast, as if pulled by ten times more mass than the visible stars and gas could account for. Something massive and invisible was doing most of the gravitational work. She called it dark matter. It doesn't emit light, doesn't absorb it — it only makes itself known by tugging on things we can see.

That was already unsettling enough. Then geometry made it worse. A balloon experiment called BOOMERANG circumnavigated Antarctica in 1997, measuring the faint temperature ripples in the oldest light in the universe — the microwave afterglow of the Big Bang. Comparing those ripple sizes to predictions for different cosmic shapes, the team found something unambiguous: the universe is geometrically flat. Flat, in the language of general relativity, means the total energy density hits a very specific number. Matter — all of it, dark and visible combined — supplies only about 30% of that required total.

1% visible matter, 29% dark matter, 70% something else entirely: a mysterious energy threaded through empty space that no one had predicted and that even now resists explanation. The universe we thought we understood turns out to be a thin crust on top of an enormous unknown.

Stars Died So You Could Exist — And That's Not a Metaphor

Stand in front of a mirror for a moment. The carbon in your skin, the oxygen cycling through your lungs, the iron threading through your blood — none of it was here at the beginning. When the universe was about one second old and the temperature had dropped to roughly 10 billion degrees, the only elements that formed were hydrogen, helium, and a whisper of lithium. The math is precise and merciless: everything heavier than that third element on the periodic table simply couldn't be built in the few minutes before the cosmos cooled too far for nuclear fusion to continue. The Big Bang left behind a universe chemically too simple for life, or for chemistry at all in any interesting sense.

So where did you come from? Stars built you, and then they had to die to deliver the materials. Deep inside stellar cores, where temperatures and pressures become almost incomprehensible, nuclear fusion assembles heavier elements — carbon, nitrogen, oxygen — from the lighter ones the Big Bang left behind. But those elements stay locked inside the star until it exhausts its fuel and violently explodes as a supernova, flinging its contents outward across light-years of space. Over the history of our galaxy, roughly 200 million such explosions have occurred, seeding the interstellar medium with the atomic building blocks of everything complex. Eventually some of that scattered debris found its way into clouds that collapsed into new solar systems — into planets, into oceans, into you.

The atoms in your left hand almost certainly came from a different stellar explosion than the atoms in your right. You are not the product of one star. You are an assembly of debris from hundreds of them, united temporarily in one body, on one small planet, aware enough to trace the journey back.

The Best and Worst Calculation in All of Physics Come From the Same Theory

Imagine a ledger that balances so perfectly that every auditor who checks it stands in quiet awe — then imagine turning the page to find an entry so catastrophically wrong that it makes the entire firm look like a joke. That is, roughly, what quantum mechanics did to physics in the twentieth century.

The same theoretical machinery that produces physics' most precise prediction immediately generates its most embarrassing one. Here is how both happen.

Quantum mechanics says that empty space is never truly empty. The Heisenberg Uncertainty Principle allows particles to borrow energy from nothing, pop briefly into existence as particle-antiparticle pairs, and vanish before the debt comes due. In 1947, a physicist named Willis Lamb measured the energy levels of hydrogen with enough precision to catch them in the act. According to Paul Dirac's earlier quantum theory, two particular energy states in hydrogen should be identical. They weren't — they differed by about 100 parts per billion. That tiny discrepancy, now called the Lamb Shift, is caused by virtual electron-positron pairs flickering in the space around the hydrogen nucleus and nudging its electron's energy. When physicists calculated the effect of those virtual particles, they matched the measurement to 100 parts per billion. It is the most accurate prediction ever made by any scientific theory.

Now ask the obvious follow-up question: if virtual particles measurably affect the space inside atoms, what do they do to space itself — to genuinely empty vacuum? When physicists run the same calculation, summing up the energy contributed by all possible virtual particles churning through the void, they arrive at a number. That number is 10 to the power of 120 times larger than the total energy of everything observable in the universe — all matter, all radiation, all of it.

The same framework. The same particles. The best prediction in physics and the worst, separated by nothing but the question you ask.

Empty space, according to the very theory that passes every experimental test, should be seething with energy enormous enough to instantly rip the universe apart. It isn't — and no one has explained it since.

A Heretical Prediction About Empty Space Turned Out to Be Right — Despite Everyone's Best Efforts

In 1996, Saul Perlmutter — a physicist at Lawrence Berkeley Laboratory hunting distant supernovae — walked up to Lawrence Krauss after a lecture and delivered a confident promise: 'We will prove you wrong.' Krauss had just spent an hour arguing that 70 percent of the universe's energy lives not in matter of any kind but in empty space itself. The idea had appeared in a 1995 paper Krauss wrote with University of Chicago cosmologist Michael Turner, and for two years almost nobody cited it except its own authors. It was that kind of idea.

The case for it was theoretically awkward but observationally forced. Measurements of how galaxies cluster showed that dark matter — already the strange invisible scaffolding Vera Rubin had inferred — made up only 30 percent of the energy density a flat universe requires. The other 70 percent had to come from somewhere. Krauss and Turner pointed at the one candidate that could account for it: the energy of the vacuum itself, Einstein's old cosmological constant, producing a repulsive force spread uniformly through all of space. This would mean the universe's expansion was accelerating — less like physics, more like a dare.

Perlmutter's supernova project was built to settle exactly this question. Type Ia supernovae burn with a consistent peak brightness, making them reliable distance markers: measure how faint one appears, and you know how far away it is. Pair that with its redshift — how fast it's receding — and you can track how the expansion rate has changed over billions of years. If gravity dominates, distant supernovae should be closer than a naive extrapolation predicts. If vacuum energy dominates and expansion is accelerating, they should be farther — appearing fainter.

By early 1998, both Perlmutter's team and a rival group led by Brian Schmidt had their answer. The supernovae were fainter than expected. The universe is accelerating. Perlmutter, who had promised to prove Krauss wrong, had instead handed him the evidence he needed. The idea Krauss himself called 'cockamamie' — the one that sat uncited for two years — was correct.

Inflation Explains Why the Universe Exists at All — and Why You Are Made of Quantum Noise

Where does the energy for an entire universe come from? It sounds unanswerable — the kind of question philosophers wave at theologians and theologians wave back. But it has a precise, almost embarrassingly tidy answer: nowhere, because the total energy of a flat universe is exactly zero.

In a flat universe, matter's positive energy and gravity's negative energy cancel to exactly zero — inflation built everything from a balanced ledger. Alan Guth called it the ultimate free lunch: a universe full of matter that costs nothing to create because, by the accounting of physics, nothing is exactly what it is.

That raises the harder question: what gets the whole machine started? Guth proposed that the very early universe got stuck in what physicists call a false vacuum — a high-energy state that looked stable but wasn't, the way a beer can be supercooled below freezing and stay liquid until you tap it, whereupon it snaps violently into ice. The universe's false vacuum behaved like a cosmological constant, driving space to expand exponentially. In a fraction of a second, a region far smaller than a proton inflated by a factor of ten to the twenty-eighth power. Whatever curvature existed beforehand got stretched away — the same way blowing up a balloon makes its surface look flat — which is why the universe we measure today is geometrically flat to the precision our instruments can detect.

Then comes the detail that should stop you cold. During that exponential expansion, quantum fluctuations — the unavoidable, subatomic jitter the uncertainty principle guarantees even in empty space — got caught and frozen by inflation. What would otherwise have been microscopic ripples, invisible and fleeting, were stretched to cosmic scales and imprinted on the fabric of space as slight density variations. Those variations are the seeds of everything. Regions slightly denser than average pulled in more matter under gravity and eventually became galaxies. Every structure in the observable universe — every cluster, every filament, every star that forged the atoms in your body — traces back to a quantum fluctuation smaller than anything you can imagine.

You are, in the most literal sense available to physics, made of quantum noise that inflation decided to keep.

Future Astronomers Will Use Perfect Logic to Reach Completely Wrong Conclusions

Here is a prediction: future astronomers will use impeccable logic, careful measurement, and the full power of general relativity to conclude that the universe is static, eternal, and exactly as large as their own galaxy. They will be completely, catastrophically wrong — and they will have no way of knowing it.

In roughly 2 trillion years, dark energy will have expanded space so thoroughly that all 400 billion galaxies currently visible to us will have redshifted past the point of detectability. Their light won't switch off — it will stretch, sliding from visible wavelengths to infrared to radio waves to wavelengths longer than the observable universe itself, then vanish below any possible threshold. Whatever astronomer is still around will see a single galaxy surrounded by an empty, static void. The evidence for the Big Bang — the Hubble expansion, the faint microwave afterglow from the early universe, the telltale elemental ratios forged in the first few minutes — will all have been systematically erased by the same dark energy whose discovery we're still celebrating. The force that reveals the universe's dynamic history to us will, eventually, bury it.

Those future scientists won't be stupid or credulous. They'll simply be working with the evidence available to them, and that evidence will point, without ambiguity, to the wrong picture. Krauss and a colleague put it this way: we live at "the only time when we can observationally verify that we live at a very special time." That sentence should hit harder than it sounds. Our entire understanding of cosmic history — the Big Bang, inflation, dark energy, the 13.72-billion-year story — rests on evidence that exists only in this narrow window of the universe's timeline. The cosmos is not keeping records for future investigators. It is erasing them.

The universe doesn't owe us the means to understand it. That we currently have them is the accident worth taking seriously.

The Cosmological Constant Looks Suspiciously Life-Friendly — and the Least Crazy Explanation Is a Trillion Universes

Why is the energy of empty space — the cosmological constant — set to the precise value it has, rather than something vastly larger or smaller? The honest answer requires swallowing something genuinely uncomfortable.

Physicists can calculate what the vacuum energy ought to be from first principles, and the answer is 10^120 times larger than what we measure. Something is canceling it down to almost nothing, but not quite nothing — and that leftover sliver turns out to be almost exactly what's needed for a universe capable of producing life. If that sounds suspicious, it should. It looks, from almost any angle, like a dial was turned with enormous care.

The alternative to a divine dial-turner is this: vastly many universes exist, each with a different value of the cosmological constant drawn from some distribution of possibilities. Steven Weinberg worked out the constraint before dark energy was even discovered. If the vacuum energy were much larger — he calculated the threshold at roughly 50 times the value we measure — it would have dominated the cosmos before gravity had time to pull matter into galaxies. No galaxies means no stars, no planets, no physicists puzzling over constants. Weinberg's point was almost tautological: we couldn't observe a universe where the vacuum energy was too large to permit observers. So regardless of how many such universes exist, we will always find ourselves in one where it's small enough for us to be here.

String theory supplies the mechanism that makes this more than a philosophical handwave. The theory requires six or seven dimensions of space beyond the three we inhabit, and those dimensions can be folded up in an almost unimaginable number of configurations — something in the neighborhood of 10^500. Each configuration produces different physical laws, different constants, a different vacuum energy. What we call 'the laws of nature' may simply be the local weather in our particular corner of this vast distribution of possible universes.

The fine-tuning that looks like evidence of purpose dissolves into anthropic tautology: we live in a life-friendly universe because we couldn't live in any other kind. That logic, uncomfortable as it is, will matter when we turn to what else it might explain. No designer required — just enough universes to sample the possibilities.

Nothing Is Unstable — Which Is Why There's Something

The vacuum instability we saw in the Lamb Shift runs deeper than atomic nudges. Empty space is constantly running a borrowing scheme — particle-antiparticle pairs flash into existence and vanish before the debt comes due. Usually, nothing escapes. Usually.

Near the event horizon of a black hole, the usual breaks down. When a virtual pair appears just outside that boundary, one partner can fall inward, losing enough gravitational energy that the outer partner escapes to infinity as a real, measurable particle — without violating conservation of energy. The black hole pays the bill by losing mass. Hawking worked this out in 1974 and realized that given enough time, a black hole could radiate itself entirely away. The vacuum, under the right conditions, is not a stable floor. It is a trapdoor.

The deeper version of the 'nothing' problem is not empty space but the absence of space and time altogether. Here is where the accounting gets dizzying in the best possible way. A closed universe — one curved tightly enough that space loops back on itself — has a total energy of exactly zero. Every joule of positive energy stored in the mass of its particles is perfectly cancelled by the negative gravitational potential those particles generate in each other. The books balance to the penny. And because quantum mechanics, via Feynman's sum-over-paths formalism, requires exploring every possible configuration of space and time — not just the ones classical physics permits — a compact, zero-energy closed universe can simply appear, spontaneously, from no prior space and no prior time. There is nothing to borrow and nothing to return.

The one remaining snag is duration. A tiny closed universe would ordinarily expand to some maximum radius and then immediately collapse, lasting perhaps 10⁻⁴⁴ seconds. But if the fields inside it happen to produce a brief period of inflation before that collapse arrives, the universe gets stretched exponentially, driven toward flatness, and survives long enough to become the kind of place where matter cools into galaxies, stars forge heavy elements, and someone eventually wonders where everything came from. What we observe around us — the flat geometry, the microwave afterglow, the large-scale structure — is exactly what this scenario predicts. Nothing, it turns out, is unstable. Given quantum mechanics and gravity, it had no choice but to become something.

'Why Is There Something?' Is the Wrong Question — and Asking the Right One Changes Everything

The question 'why is there something rather than nothing?' feels profound precisely because it smuggles in the assumption that the universe owes you a purposeful answer. Swap one word — replace 'why' with 'how' — and watch what happens. The question doesn't shrink. It becomes answerable.

Johannes Kepler thought he had the ultimate why. In 1595 he worked out that the six known planets corresponded exactly to the five Platonic solids nested inside each other, their orbital distances matching the spheres that could be drawn around each shape. The geometry was exquisite. The implication was clear: God was a mathematician, and the architecture of the solar system was His proof. Kepler wept with the beauty of it. Then the telescope improved, Uranus and Neptune turned up, spacecraft found thousands of planetary systems orbiting other stars, and the question 'why six planets?' dissolved into incoherence. Not because science defeated it — but because the question had been pointing at a non-existent target. The real inquiry turned out to be 'how do solar systems form?' — and that question has a mechanism, testable predictions, and an answer. The satellite that found most of those exoplanets is named Kepler. The universe has a sense of irony.

That is the template. Newton showed that planets don't need angels nudging them forward; they need only a force aimed at the Sun. Every 'why' that seemed to demand purpose has eventually cashed out as a 'how' that required only physics.

Even granting an omnipotent creator, only a vanishingly narrow set of physical laws can produce beings capable of asking questions at all. A god would have had no room to maneuver — constrained by the same mathematics as everything else. That doesn't just make the concept unnecessary. It makes it structurally inert: a cause with nothing left to cause.

Replace 'why' with 'how,' and you don't get a smaller answer. You get an honest one.

The Most Honest Answer to the Oldest Question

Here is what you're left with: a universe that began as a quantum accident, will end in cold and silence, and in between produced you — briefly, improbably, aware enough to reconstruct the whole story. Krauss isn't arguing that nothing matters. He's arguing that meaning isn't installed at the factory. It's what you do with the window. And the window is genuinely narrow — 2 trillion years sounds generous until you remember the evidence is already dissolving at the edges, light from distant galaxies stretching itself into permanent silence while you're reading this sentence. The cosmos didn't need a reason to make you, and it doesn't owe you one. What it gave you instead is stranger and more valuable: a brief, unrepeatable vantage point on a universe that arrived uninvited and stayed. The how, it turns out, is more than enough.