Introduction
You naturally assume that nothingness is empty and that something must have created existence. You wonder why anything exists at all and whether purpose governs the cosmos. Lawrence Maxwell Krauss explains that modern physics completely transforms this traditional puzzle.
Modern physics demonstrates that everything, including space and time itself, can spontaneously emerge from nothing without supernatural intervention.
This book takes you through the discoveries of modern cosmology and quantum mechanics. You explore the expansion of the universe, invisible dark matter, and the thermal afterglow of the Big Bang. You discover how empty space teems with virtual particles and how dark energy drives an accelerating cosmic future.
The book answers specific questions about existence:
- How can a universe arise from nothing without a creator?
- What do galactic rotation curves reveal about hidden matter?
- Why does the cosmic microwave background prove spatial flatness?
- How does quantum mechanics redefine empty space?
- What does an accelerating universe mean for your future?
1. A Cosmic Mystery Story
Science replaces teleological why questions with operational how questions, mapping cosmic distances and establishing that the universe expands from a hot primeval atom.
From Purpose to Mechanism
When you ask why the physical world exists, you risk falling into an endless regress. Teleological questions of purpose often lead to a dead end where the only logical response is because. Science progresses by shifting focus toward operational mechanisms and historical processes.
Johannes Kepler in 1595 believed he answered why there were six planets by linking them to the five Platonic solids and the mind of God. Modern discoveries of thousands of planets orbiting other stars rendered that question meaningless.
Mapping Cosmic Distances
Henrietta Swan Leavitt discovered the period-luminosity relation for Cepheid variable stars in Harvard College Observatory. Working as a computer, she found a regular relationship between stellar brightness and variation period. Edwin Hubble used this relation in the Andromeda nebula to prove it was an independent galaxy far outside the Milky Way.
The Expanding Universe
Edwin Hubble and Milton Humason announced in 1929 that galaxies twice as far away are moving away twice as fast. They combined distance measurements with Vesto Slipher's spectral Doppler shifts showing light stretched toward longer wavelengths. This Hubble's law proved the universe is expanding uniformly.
Belgian priest and physicist Georges Lemaître solved Einstein's equations in 1927 for a nonstatic universe. He proposed the Primeval Atom and Day with No Yesterday in 1930. Pope Pius XII cited Lemaître's theory in 1951 as scientific proof of Genesis and creation, a theological interpretation Lemaître later publicly objected to.
Calculations of primordial nucleosynthesis in a 10-billion-degree early universe correctly predict the cosmic abundances of light elements. Essentially every atom in the human body was once inside a star that exploded, and roughly 200 million stars have exploded over the history of our galaxy when the universe was 1 second old.
2. Weighing the Universe
Visible stars and glowing gas make up only a fraction of the cosmos. When you add up every luminous source, the visible totals fall short of what keeps galaxies intact.
Vera Rubin's galactic rotation curves and Einstein's gravitational lensing prove that invisible dark matter constitutes the vast majority of matter in the cosmos.
Dark Matter Discovery
In the early 1970s, Vera Rubin measured galactic rotation rates to test how mass distributes in space. By observing stars and hot gas far from the galactic center, Rubin proved they move too fast for visible gravity alone, pointing to the existence of unseen dark matter.
Calculations based on these dynamics revealed a 10 to 1 ratio of total matter to visible matter. Rubin graduated with a doctorate from Georgetown and became the second woman awarded the Gold Medal of the Royal Astronomical Society.
Gravitational Lensing
Albert Einstein demonstrated that space can curve and act as a gravitational lens, bending and magnifying light from distant objects. Although Einstein initially believed the effect of lensing by stars was too small to measure, astronomers like Fritz Zwicky later realized that lensing by massive galaxy clusters could weigh the universe.
In 1936, Einstein published his paper on gravitational lensing in Science. In 1933, Zwicky analyzed the Coma cluster to examine these hidden masses.
In 1998, Tony Tyson and colleagues used Hubble Space Telescope images of cluster CL 0024 + 1654 to trace distorted background galaxies and map invisible mass. The cluster CL 0024 + 1654 sits at a distance of 5 billion light-years.
These measurements help determine open, closed, or flat geometries for superclusters. Total mass in and around galaxies reaches only 30 percent compared to what is needed for a flat universe.
3. Light from the Beginning of Time
The cosmic microwave background radiation provides the thermal afterglow of the Big Bang, confirming through geometric triangles that the universe is spatially flat.
Cosmic Microwave Background
When the universe was 300,000 years old, it cooled to 3,000 degrees Kelvin. Protons and electrons combined into neutral hydrogen during this transition.
This created the last scattering surface from which ancient photons travel freely to you today. Expansion cooled this thermal afterglow to 3 degrees above absolute zero.
About 1 percent of the static seen on old analog television channels before cable television came from radiation left over from the Big Bang. Two scientists in New Jersey discovered this signal in 1965.
Measuring Flatness
The three-dimensional geometry of the universe can be measured directly using cosmic triangles formed by the afterglow of the Big Bang, just as two-dimensional curvature can be found by measuring angles on a sphere.
Carl Friedrich Gauss measured large triangles between mountain peaks in the 1820s and 1830s to detect space curvature. Nikolai Ivanovich Lobachevsky later suggested using stellar triangles with Sirius, establishing a lower limit for universe curvature at 166,000 times the radius of the Earth's orbit.
On a flat Euclidean surface, triangle angles sum to 180 degrees, but on curved surfaces they differ. In cosmology, the characteristic scale of hot and cold spots in the cosmic microwave background radiation acts as a standard ruler to test whether the universe is flat, open, or closed.
The physical size of the largest lumps of matter that had time to collapse under gravity at the last scattering surface creates a characteristic angular scale of about 1 degree. Comparing this scale with computer simulations of closed, flat, and open universes revealed that our universe is flat.
The BOOMERANG experiment launched a microwave radiometer on a high-altitude balloon in Antarctica in 1997 that circled the continent in two weeks, followed later by the Wilkinson Microwave Anisotropy Probe or WMAP satellite launched in 2001. Data from WMAP confirmed the flat universe with 1 percent accuracy, supporting a universe with an age of 13.72 billion years.
4. Much Ado About Nothing
Quantum mechanics reveals that empty space teems with virtual particles, whose vacuum energy predictions clash wildly with astronomical observations.
Virtual Particles and the Vacuum
Quantum mechanics and relativity combine to dictate that empty space is constantly filled with virtual particles popping in and out of existence. Because the Heisenberg Uncertainty Principle prevents exact measurement of energy over extremely short time intervals, particles can momentarily travel faster than light and move backward in time. This time reversal corresponds mathematically to the creation of virtual particle-antiparticle pairs.
Richard Feynman used wartime diagrams of bombardiers viewing roads to illustrate how an electron emitting and reabsorbing a positron-three-particle intermediate state represents a single particle tracing a switchback path.
The physical effects of virtual particles are verified by extremely precise atomic measurements and account for the vast majority of visible mass in the universe. When calculating energy level spacings in hydrogen atoms or the internal rest mass of protons and neutrons, standard particle contributions alone are insufficient. Virtual particle fluctuations surrounding quarks and electric charges contribute most of the rest energy and mass.
In April 1947, Willis Lamb and Robert C. Retherford measured hydrogen energy levels with an accuracy of 1 part in 100 million, revealing fine structure discrepancies resolved only by including virtual particles.
The Worst Prediction in Physics
Naïve calculations of the energy of empty space driven by virtual particles yield a value that is 120 orders of magnitude larger than all known matter in the universe, constituting the worst prediction in physics. When summing all possible virtual particle energies up to the Planck-time cutoff without subtracting matter terms, the predicted vacuum energy is vastly too large. If correct, this repulsive force would have instantly blown the universe apart and prevented any structure formation.
Yakov Zel'dovich made this profound discrepancy explicit around 1967, establishing the cosmological constant problem that remains unsolved.
5. The Runaway Universe
Supernova observations reveal that dark energy drives an accelerating expansion, making the universe flat and pointing toward a lonely future.
Astronomers expected gravity to slow down the cosmic expansion. However, measurements of distant Type Ia supernovae showed that they appeared fainter than expected in a decelerating universe, indicating an accelerating expansion driven by a repulsive cosmological constant.
Saul Perlmutter's Supernova Cosmology Project and Brian Schmidt's High-Z Supernova Search Team competed in measuring distant supernovae, initially publishing conflicting results before both groups confirmed cosmic acceleration.
This discovery requires 70 percent of the total energy residing in empty space. Another 30 percent of the energy resides in dark matter.
Computations of stellar evolution in globular clusters and precision measurements of the cosmic microwave background confirmed that the universe is 13.72 billion years old, an age impossible without dark energy. Lawrence Krauss and Brian Chaboyer modeled millions of stars on computers to put lower limits on stellar ages, which were later refined by WMAP satellite measurements.
Cosmic Acceleration
The universe shifted from a period of deceleration to acceleration when matter density dropped below vacuum energy density, an inflection point in mechanics known as a jerk. In the early universe, matter was denser and its attractive gravity caused deceleration. As the universe expanded and matter diluted, the constant energy density of empty space took over, causing the expansion to accelerate.
Adam Riess reported the discovery of the cosmic jerk at a conference organized by Lawrence Krauss in 2003, leading to a New York Times headline.
Cosmic inflation solves the horizon and flatness problems by proposing an exponential expansion phase driven by false vacuum energy in the very early universe. As the universe cooled, it may have gotten stuck in a metastable false vacuum state. The latent heat of this vacuum acted like a cosmological constant, causing superluminal expansion that flattened the universe and brought disconnected regions into thermal contact.
Alan Guth formulated inflation in 1981. During this inflationary period, the universe could have expanded by a factor of 10 to the 28th power.
Quantum fluctuations in empty space during inflation were frozen and amplified into density fluctuations, creating the seeds for all galaxies, stars, and people. Microscopic quantum fluctuations in the false vacuum ended at slightly different times across different regions, creating the tiny temperature variations observed in the cosmic microwave background and driving gravitational collapse.
The Ultimate Free Lunch
In a flat universe, the positive energy of matter and radiation is exactly canceled by the negative energy of gravitational attraction, resulting in a total energy of zero. General relativity allows gravitational energy to be negative, matching the positive kinetic and rest-mass energy of objects. This means a universe filled with matter can be created from absolute nothingness without violating energy conservation.
Throwing a ball into the air demonstrates how kinetic and gravitational potential energies balance, leading to an escape velocity of 7 miles per second from Earth's surface.
6. Brave New Worlds
The Multiverse Landscape
Quantum fluctuations cause some regions to exit inflation while others continue expanding exponentially forever. Andrei Linde and Alex Vilenkin developed and explored scenarios of chaotic eternal inflation.
Eternal inflation naturally generates a multiverse where different regions cease inflating to become causally disconnected bubble universes with diverse physical properties.
String theory requires twenty-six original dimensions in string theory. Mathematical symmetries like supersymmetry reduced this to ten dimensions. Different ways of curling up the remaining six spatial dimensions lead to estimates of immensely varied consistent four-dimensional vacuum states.
Frank Wilczek compared string theorists' methodology to throwing a dart at a blank wall and drawing a bull's-eye around where it landed. This massive potential yields $10^{500}$ possible consistent four-dimensional universes.
The extremely small value of vacuum energy may be explained anthropically, because a slightly larger value would have caused repulsive forces to prevent galaxy formation and life. If the energy of empty space were merely 50 times greater than observed, repulsive forces would have dominated before galaxies could form a billion years after the Big Bang, leaving no astronomers to measure it. This value remains 120 orders of magnitude smaller than naive particle physics estimates.
Science Versus Theology
You can observe how physics makes predictions verified with stupefying accuracy. Quantum theory predictions are verified to decimal places equivalent to measuring the distance between New York and Los Angeles within a hairsbreadth.
Richard Feynman pointed out the extreme accuracy of quantum theory predictions. Thomas Jefferson founded the University of Virginia without a professorship of theology.
Science provides accurate, testable results, whereas theology relies on untestable speculations disconnected from reality.
Theology lacks any connection to the real world and relies on vague abstractions or uncritical appeals to design and first causes. You find the scale of precision in counting quanta and quarks compared to medieval theological debates reaching 10 billion.
10 Key Ideas
- Science replaces teleological why questions with operational how questions, mapping cosmic distances and establishing that the universe expands from a hot primeval atom.
- Vera Rubin's galactic rotation curves and Einstein's gravitational lensing prove that invisible dark matter constitutes the vast majority of matter in the cosmos.
- The cosmic microwave background radiation provides the thermal afterglow of the Big Bang, confirming through geometric triangles that the universe is spatially flat.
- Quantum mechanics reveals that empty space teems with virtual particles, whose vacuum energy predictions clash wildly with astronomical observations.
- Supernova observations reveal that dark energy drives an accelerating expansion, making the universe flat and pointing toward a lonely future.
- In a flat universe, the positive energy of matter and radiation is exactly canceled by the negative energy of gravitational attraction, resulting in a total energy of zero.
- Eternal inflation naturally generates a multiverse where different regions cease inflating to become causally disconnected bubble universes with diverse physical properties.
- Science provides accurate, testable results, whereas theology relies on untestable speculations disconnected from reality.