A Universe From Nothing

Theoretical physicist Lawrence M. Krauss argues that modern science can address one of the oldest questions in philosophy and theology: Why is there something rather than nothing? Drawing on discoveries in cosmology, particle physics, and gravitation, he contends that getting something from nothing is not only plausible but may have been required. He argues that in science, "why" questions are really "how" questions, since "why" implies purpose and leads to infinite regress. He traces the scientific revolutions of the past century and makes the case that these discoveries render the notion of a divine creator unnecessary.

Krauss begins by recounting how Albert Einstein's general theory of relativity, completed in 1916, provided the first framework capable of describing not just the motion of objects but the evolution of the universe itself. Einstein's equations seemed incompatible with the prevailing view of a static, eternal universe, so he introduced a "cosmological constant," a repulsive term to counterbalance gravity, which he later regretted. Belgian priest and physicist Georges Lemaître independently solved Einstein's equations in 1927, showing that the theory predicts an expanding universe. Lemaître further proposed that the expansion began from an infinitesimal point, an idea that became the foundation of Big Bang theory. Although Pope Pius XII seized on the Big Bang as evidence for the biblical creation account in 1951, Lemaître himself objected, recognizing that tying theology to a scientific theory risked embarrassment if the theory were disproved.

Astronomer Edwin Hubble, using a brightness-period relationship for Cepheid variable stars discovered by astronomer Henrietta Swan Leavitt, proved in 1925 that spiral nebulae like Andromeda were separate galaxies far beyond the Milky Way. By 1929, Hubble and colleague Milton Humason combined distance measurements with redshift data—measurements of how light from receding galaxies stretches toward longer, redder wavelengths—to establish Hubble's Law: Galaxies farther away are moving away faster, demonstrating that space itself is expanding. Traced backward, this expansion points to a hot, dense origin approximately 13.72 billion years ago, a timeline supported by Big Bang nucleosynthesis, the process by which light elements formed in the universe's first minutes, which correctly predicts the abundances of hydrogen, deuterium, helium, and lithium.

Beginning in the 1970s, astronomer Vera Rubin's measurements of galaxy rotation rates revealed that stars at the edges of galaxies move far faster than visible matter can account for, implying vast amounts of unseen "dark matter." Calculations showed that most dark matter cannot consist of ordinary protons and neutrons but must be some unknown type of particle. Krauss explains that general relativity links the total energy density of the universe to its geometry: A "closed" universe with enough mass will eventually recollapse, an "open" universe will expand forever, and a "flat" universe sits at the boundary. Measurements using gravitational lensing, in which gravity bends and magnifies light to reveal a cluster's total mass, showed that total matter in and around galaxy clusters accounts for only about 30 percent of the energy needed for a flat universe, apparently indicating an open geometry.

A more direct measurement came from the cosmic microwave background radiation (CMBR), the residual glow from when the universe was about 300,000 years old and first became transparent to light. Discovered accidentally at Bell Laboratories in 1965, the CMBR provides a snapshot of the infant universe. The angular size of density fluctuations on the last scattering surface, the shell of radiation released when the universe became transparent, depends on the curvature of space. The BOOMERANG balloon experiment, launched from Antarctica in 1997, and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001, both confirmed that the fluctuation pattern matches predictions for a flat universe. This created a contradiction: The universe is flat, requiring a certain total energy density, yet all matter accounts for only 30 percent. Seventy percent of the universe's energy was missing.

Krauss explains that quantum mechanics and relativity together reveal empty space to be far from empty. "Virtual particles," particle-antiparticle pairs, spontaneously pop into and out of existence on timescales too short to observe directly, but their indirect effects are measurable: Calculations of hydrogen's atomic energy levels that include virtual particles agree with experiment to about one part in a billion. When physicists try to calculate the total energy virtual particles contribute to empty space, the estimate exceeds the energy of all known matter by a factor of roughly 10 to the 120th power, a discrepancy known as the Cosmological Constant Problem. Theorists assumed some symmetry would cancel this energy to zero, but observations proved otherwise.

In 1998, two competing teams measuring distant Type Ia supernovae, a class of exploding stars whose brightness makes them useful as standard candles for distance measurement, independently discovered that the universe's expansion is accelerating. The best-fit model corresponded to a flat universe with 30 percent matter and 70 percent "dark energy" in empty space, precisely the ratio Krauss and cosmologist Michael Turner had proposed in a 1995 paper. Over the following decade, multiple lines of evidence confirmed this picture, including precision WMAP measurements and the detection of the "cosmic jerk," the transition from deceleration to acceleration.

Krauss introduces inflation, a brief period of exponential expansion in the early universe proposed by physicist Alan Guth in 1981, to explain why the universe is flat and uniform. If energy stored in a "false vacuum," a metastable state of empty space, drove this expansion, the universe could have grown by a factor of more than 10 to the 28th power in a fraction of a second. Inflation solves the Flatness Problem by driving any curvature toward zero and the Horizon Problem by showing that the entire observable universe was once compressed into a region small enough for thermal equilibrium. Inflation also predicts that quantum fluctuations, the random temporary variations in energy that quantum mechanics permits in otherwise empty space, get frozen during expansion and emerge as the density variations observed in the CMBR, meaning all cosmic structure originated from quantum fluctuations in essentially nothing. Krauss highlights what Guth called the "ultimate free lunch": Because gravitational energy is negative, the positive energy of matter can be exactly balanced by negative gravitational energy, making the total energy of a flat universe precisely zero.

The book then turns to the bleak long-term future. Because the expansion is accelerating, galaxies beyond our local gravitational group, the Milky Way's cluster of gravitationally bound neighbors, will eventually recede faster than light and vanish. By about two trillion years from now, all evidence of the Big Bang will have disappeared. Future scientists will observe what scientists believed in 1915: a single galaxy in a static, empty universe.

Krauss considers whether fundamental constants might be environmental accidents rather than deep necessities. If many universes exist with different values for the cosmological constant, as physicist Steven Weinberg proposed, only those with values small enough to allow galaxy formation would contain observers. Inflation naturally produces such a "multiverse" through eternal inflation: Quantum fluctuations cause some regions to stop inflating while others continue, creating an infinite number of causally disconnected universe-regions. String theory, a framework in which elementary particles arise from vibrating strings in extra dimensions, compounds this picture by allowing perhaps 10 to the 500th power different universes, each with different physical laws.

The book's final chapters present three escalating versions of "something from nothing." First, empty space endowed with energy can, through inflation, produce all the matter and radiation we observe at zero net energy cost. Second, extending quantum mechanics to gravity suggests that space and time themselves can arise spontaneously: A closed universe with zero total energy could appear without violating energy conservation, and if it undergoes inflation, it can expand to enormous size and persist far longer than the current age of the universe. Cosmologist Alex Vilenkin proposed in the early 1980s that quantum gravity could create an inflating universe from no preexisting space or time. Third, in a multiverse the laws of physics themselves may be random, arising along with the universes they govern, so no external agent is needed to fix them. Krauss contends that the metaphysical rule "out of nothing nothing comes" has no foundation in science.

In the epilogue, Krauss affirms that the case for a universe arising from nothing is the most compelling intellectual alternative currently available. He stresses that the distinction between "something" and "nothing" has begun to dissolve as science reveals that transitions between the two are common and even required. Returning to Einstein's question of whether God had any choice in creating the universe, Krauss argues that the constraints of physical consistency may leave no freedom in creating a universe that supports beings capable of asking the question, making a creator, in his view, "unnecessary" or "at best redundant" (185).