Great Discoveries in Science: The Big Bang Theory

The horrors of World War I deeply impacted Georges Lemaître and shifted his career path from engineering to priesthood and theoretical physics.

Some discoveries, like Alexander Fleming’s 1928 discovery of penicillin, come from a single scientist. Others, like the big bang theory, are created by many scientists over time.

The big bang theory took enormous amounts of foundational science, as shown in the previous chapter, followed by theoretical proposals and tangible discoveries that helped create a narrative of the first few seconds of our universe and the billions of years that followed.

The first murmurs of an expanding universe, including a model that began with a big bang, came in the early twentieth century.

Albert Einstein’s theory of general relativity raised an enormous question of the future of the universe. Was it expanding, was it contracting, or was it staying the same? In 1927, Georges Lemaître proposed a theory of an expanding universe, but it was largely ignored at first. Two years later, Edwin Hubble’s groundbreaking work at Mount Wilson Observatory provided a clear answer: the universe was expanding over time.

In the 1920s, Einstein’s focus turned to finding a unified field theory that would bring all forces of the universe into one framework.

Albert Einstein was born in 1879 in Ulm, Germany, a city whose motto was “Ulmenses sunt mathematici” or “the people of Ulm are mathematicians.” His family moved to Munich when he was six weeks old.

Albert’s speech was slow to develop, but contrary to popular belief, he was an excellent student. He was also a rebellious student, however, and questioned authority and the teaching methods at his academy.

As a child, Albert became fascinated with science when he was home sick from school and his father brought him a compass. Albert was intrigued by the power of a hidden force field on the compass’s needle, later writing, “I can still remember—or at least I believe I can remember—that this experience made a deep and lasting impression on me … Something deeply hidden had to be behind things.”

Albert attended a high school, the Luitpold Gymnasium, that emphasized math and science. He got top marks in his courses and was far ahead of the school’s standards in math. In his adolescence, he devoured books on math and science and developed a strong aversion to religion. Yet his deep suspicion of authority created trouble for him at school.

When the family business went under, his family moved to northern Italy and left fifteen-year-old Albert behind to finish his studies in Munich. Albert left the school that Christmas, however, and joined his family in Italy, vowing to never go back to Germany. He later finished school in Aurau, Switzerland, before entering the Zurich Polytechnic.

Einstein graduated from university in 1900. He had trouble finding a professorship and ended up accepting a job at the patent office in Bern in 1902. The menial position afforded him both the spare time and the intellectual freedom to develop the ideas that would one day make him famous. In 1905, he made his first foray into fame. That year, Einstein published five papers that changed physics forever, including one with his famous equation, E=mc², and another with his special theory of relativity.

Another of these papers, on molecular measurements, finally earned Einstein his PhD. He became a lecturer at the University of Bern in 1908, a junior professor at the University of Zurich in 1909, a professor of theoretical physics in Prague in 1911, and a professor at the University of Berlin in 1914.

When Einstein published his general theory of relativity in 1915, Hubble had not yet discovered galaxies beyond the Milky Way. Most astronomers at this time, including Einstein, believed that the universe consisted of just our Milky Way and its approximately one hundred billion stars. Most, again including Einstein, also believed that the universe was in an overall stable state, neither expanding nor shrinking.

Edwin Hubble’s discoveries of the Andromeda galaxy and the direct correlation between the distance of a galaxy from Earth and its recession speed shook Einstein’s understanding of the universe. He dismissed his cosmological constant and embraced the expanding universe, and on his second visit to America, Einstein took a trip to Mount Wilson to pay a call on Hubble and the Hooker Telescope.

Einstein was in California when Adolf Hitler took power in 1933, and Einstein never went back to Germany. He stayed in America, where he became a professor of theoretical physics at the Institute for Advanced Study in Princeton, New Jersey. He held this post until his retirement in 1945. In addition to his contribution to physics, Einstein wrote significantly on pacifism, helped dozens of Jewish refugees enter the United States, and supported the foundation of a Jewish state. He was offered the presidency of Israel in 1952, but he declined.

Einstein enjoyed playing the violin, which helped him work through difficult problems, as well as sailing. During his life, he won numerous prizes including the 1921 Nobel Prize. He died in 1955.

The Hooker Telescope has received control systems and optics upgrades over the years and is still used today.

Edwin Hubble was born in Missouri in 1889 and moved to Chicago with his family at the age of nine. He attended the University of Chicago, where he obtained a degree in mathematics and astronomy in 1910. He earned a Rhodes scholarship to study at Oxford University, where he switched his studies to law to keep a promise to his father. After three years, he obtained a law degree and returned to the United States.

In 1914 Hubble switched back to astronomy, enrolling in a PhD program at Chicago University. “I knew that even if I were second or third rate, it was astronomy that mattered,” he said. He was offered a job at the Mount Wilson Observatory in 1917, but he postponed his acceptance to enlist in the military. After serving briefly in France, Hubble returned to the United States and began his post at the Mount Wilson Observatory in 1919.

Hubble worked for decades at the observatory. He served again in World War II as a supervisor at the Aberdeen Proving Ground in Maryland (a location for ordnance design and testing), for which he earned a Medal of Merit in 1946. He also helped design and construct the Hale Telescope, a 200-inch (5-meter) telescope on Palomar Mountain. Hubble died in 1953.

Georges Lemaître was born in Charleroi, Belgium, in 1894. Lemaître initially studied engineering before volunteering for the Belgian army and serving as an artillery officer during World War I. During the war, Lemaître witnessed the first poison gas attack in history and was decorated with the Croix de Guerre (Cross of War).

Post-war, Lemaître switched his scientific focus from engineering to mathematics and physics. He obtained a doctorate from the University of Louvain in 1920 and was ordained as a priest in 1923. Lemaître received a traveling scholarship from the Belgian government, awarded for a thesis he wrote on relativity and gravitation, that allowed him to spend the subsequent years studying at Cambridge University, the Harvard College Observatory, and the Massachusetts Institute of Technology. He returned to the University of Louvain in 1925 and became a full professor of astrophysics there in 1927.

That same year, Lemaître proposed that the universe had begun at a finite moment in a highly condensed state and had expanded ever since. He published his theory in the Annals of the Scientific Society of Brussels, which was not widely read outside of Belgium. Some who did read it dismissed his work as influenced by his theological studies, as the idea of a beginning could imply a divine creator. Lemaître disliked religious readings of his cosmology, however, arguing that his theory “remains entirely outside any metaphysical or religious question.”

Everything changed for Lemaître when his former Cambridge University professor Sir Arthur Eddington began to champion Lemaître’s work. Eddington, who had observed the 1919 eclipse, had seen the initial publication but forgot about it for some time. In 1930, three years after Lemaître first published his expansion theory and one year after Hubble released his data on the expanding universe, Eddington wrote a letter to the journal Nature drawing attention to Lemaître’s work. In hindsight, with Hubble’s data as evidence, Lemaître’s work was significantly easier to accept.

Einstein had read Lemaître’s 1927 paper and originally told him that his math was correct but his physics were abominable. After Hubble’s data was published, however, Einstein was much more interested in what Lemaître had to say about cosmology, and the two had many walks and talks together over the following years.

After publishing on his primeval atom theory, Lemaître’s academic work included cosmic rays, celestial mechanics, and pioneering work on using computers to solve astrophysical problems. He received numerous awards, including the Royal Astronomical Society’s first Eddington Medal in 1953. Lemaître died in 1966.

Einstein, Hubble, and Lemaître laid the foundation for modern cosmology. Einstein’s general theory of relativity raised curious questions about the universe, Lemaître published a theory of a universe with a finite beginning and original highly condensed state, and Hubble’s data provided evidence that the universe was indeed expanding over time.

Over the subsequent decades, numerous scientists would propose theories that built on that foundation and make discoveries that helped create the standard big bang model of cosmology. George Gamow and Ralph Alpher proposed a modification of Lemaître’s work in which all of the elements were formed in the big bang. Fred Hoyle opposed the big bang model, but his work on stellar nucleosynthesis helped fill in scientific gaps in the theory. Arno Penzias and Robert Wilson unintentionally discovered strong evidence of the big bang, and George Smoot designed a massive experiment to find whether that evidence could also explain the formation of stars and galaxies over time.

George Gamow was born in Odessa, Ukraine (it was part of the Russian Empire at the time), in 1904. He loved science from a young age, growing interested in astronomy when his father gave him a telescope for his thirteenth birthday.

Gamow graduated from the University of Leningrad in 1928 and moved to Göttingen, Germany, where he developed a theory of radioactive decay as a function of quantum mechanics. He was the first to successfully explain why some radioactive elements decay in seconds while others slowly decay over millennia.

Alexander Friedmann

Like Lemaître, Alexander Friedmann also solved Einstein’s equations of general relativity and proposed an expanding model of the universe in the 1920s. Friedmann and his theory received significantly less attention than Lemaître, however, due to Friedmann’s background as a mathematician (not a physicist) and his death in 1925, before Hubble had shown that the universe was indeed expanding.

Friedmann was born in 1888 in St. Petersburg, Russia. As a student, Friedmann showed a remarkable talent for mathematics and coauthored a paper published in Mathematicshe Annalen in 1905. During World War I, Friedmann joined the volunteer aviation detachment and flew in bombing raids.

After the war, Friedmann worked in various positions including as head of the Central Aeronautical Station in Kiev, as a professor at the University of Perm, and as director of the Main Geophysical Observatory in Leningrad. The cosmologist George Gamow briefly studied under Friedmann at the observatory.

Friedmann became interested in Einstein’s general theory of relativity and published an article, “On the Curvature of Space,” in 1922 that proposed a dynamic, expanding universe. Einstein quickly rejected Friedmann’s work in the same journal, Zeitschrift für Physik, though he retracted his rejection again in the journal in 1923.

Friedmann’s equations for the expansion of space, known as the Friedmann equations, show the fate of the universe as either expanding forever, expanding forever at a decreasing rate, or collapsing backward (dependent on its density).

Friedmann’s career in cosmology was cut short in 1925 when he died of typhus.

Gamow became a professor at the University of Colorado at Boulder in 1956 and worked there until his death.

The theoretical physicist Niels Bohr offered Gamow a fellowship at the Theoretical Physics Institute of the University of Copenhagen where, among other work, Gamow worked on calculations of stellar thermonuclear reactions. Gamow also convinced the experimental physicist Ernest Rutherford of the value in building a proton accelerator, which was later used to split a lithium nucleus into alpha particles.

As much of Europe faced the pressures of communism and fascism in the 1930s, many intellectuals fled the continent (including Einstein). Gamow made several attempts to escape the Soviet Union, including an attempted crossing of the Black Sea into Turkey via kayak in 1932. He finally got his chance to escape when he was invited to give a talk in Brussels on the properties of the atomic nuclei. Gamow arranged for his wife, Rho, also a physicist, to accompany him. From there, the Gamows traveled through Europe and then to America in pursuit of an academic career outside of the Soviet Union.

Though he hoped for a prestigious position at a school known for its physics program, Gamow ended up accepting a position at George Washington University, which at the time didn’t have a strong reputation in physics. Gamow quickly changed that, however, as his terms of acceptance involved expanding the physics department at GWU and establishing a theoretical physics conference series.

In addition to developing a theory of element formation in the big bang, Gamow’s research included stellar evolution, supernovas, and red giants. In later years, Gamow made contributions in biochemistry as well as a foray into what he called “the physics of living matter.” After reading about Watson and Crick’s work on the structure of DNA in the journal Nature, he wrote his own note to Nature proposing the existence of a genetic code within DNA that was determined by the “composition of its unique complement of proteins” made up of chains of amino acids. Gamow’s ideas inspired Watson, Crick, and many other researchers to begin researching how DNA coded proteins.

Gamow also wrote numerous popular books designed to give non-physicists access to complex topics, including the Mr. Tomkins series about a toy universe with properties different from our own and One, Two, Three…Infinity. Gamow died in 1968.

Ralph Alpher was born in 1921 in Washington, DC, to immigrant parents. He was accepted into the Massachusetts Institute of Technology but his scholarship was withdrawn after he met with an alumnus. Alpher always suspected the sudden change happened because he had told the alumnus of his Jewish heritage. Instead, Alpher enrolled at George Washington University, where he obtained his undergraduate, master’s, and doctoral degrees.

Alpher began his contributions to cosmology when he worked on the synthesis of elements in the big bang with his dissertation advisor George Gamow. The paper was published on April 1, 1948. As an April Fool’s joke, Gamow listed physicist Hans Bethe as a coauthor “in absentia” so that the byline would read “Alpher-Bethe-Gamow,” a play on the first three letters of the Greek alphabet. As a result of Gamow’s joke, Alpher’s contributions to the research were overlooked as many assumed the more senior Bethe had played a more significant role than young Alpher.

Alpher continued his work on nucleosynthesis with another physicist, Robert Herman, publishing numerous papers on nucleosynthesis and the early universe. They predicted that the radiation left over from the early universe should be about 5 degrees K in the present universe and encouraged scientists to look for this radiation.

The reception toward Alpher and Herman’s work was cool, and both left academia. Alpher accepted a job at General Electric, where he worked in research and development for thirty-two years.

Later in life, Alpher’s predictions were proven true when Arno Penzias and Robert Wilson found the relic radiation from the big bang at a temperature in accordance with Alpher and Herman’s predictions. Still, Alpher’s contributions to the big bang model of cosmology were largely overlooked in favor of Penzias, Wilson, and Gamow until recent decades. The continued slights and lack of inclusion in big bang science accolades haunted him. Alpher died in 2007.

Sir Fred Hoyle was one of the biggest opponents of the big bang theory but also the man who gave it its name and a contributor to its development.

Hoyle was born in Yorkshire, England, in 1915. He attended Emmanuel College and Cambridge University and worked on radar development for six years during World War II. He then returned to Cambridge, where he lectured in mathematics.

In 1948, Hoyle, the astronomer Thomas Gold, and the mathematician Hermann Bondi developed the steady state theory, which holds that the universe is expanding but that new matter is continuously being created such that the mean density of matter in space remains a constant. As galaxies move away, new galaxies emerge between them, such that the large-scale properties of the universe remain the same over time.

Hoyle’s work included more than a decade of research that demonstrated that all of the elements from carbon and up to iron could be synthesized inside of stars as a result of nuclear fusion. In 1957, Hoyle, along with Margaret Burbidge, Geoffrey Burbidge, and William Fowler, published a paper showing that even heavier elements could be produced by stars through supernovas.

Hoyle also appeared in a series of radio talks on astronomy in the 1940s, in which he used the term “big bang” to mock his rival physicists. The term stuck, just as the big bang theory itself did.

Hoyle also wrote on the possibility that life originated in space, as well as many science fiction books such as The Molecule Men and the Monster of Loch Ness; a television series, A for Andromeda; and a play, Rockets in Ursa Major. Hoyle was knighted in 1972 and died in 2001.

Arno Penzias was born in Munich, Germany, in 1933 to a Jewish family. His family was rounded up for deportation to Poland when he was a young boy, but they returned to Munich after a number of days. His parents, aware of the danger they faced, sent Arno and his younger brother on a train to England in 1939.

His parents were able to join the two boys in England and, after six months there, they moved to New York City. Penzias attended the City College of New York, a municipally funded college dedicated to educating the children of New York’s immigrants. After college, he spent two years in the Army Signal Corps, which develops and manages communication and information systems for the command and control of the military.

When he began his graduate studies in physics at Columbia University in 1956, that army experience helped Penzias gain research projects in the Columbia radiation laboratory. For his thesis, he built a maser amplifier, a device that amplifies electromagnetic radiation, for a radio astronomy experiment.

Penzias and Wilson made their discovery of the CMB on the Holmdel Horn Antenna, which detects radio waves.

After finishing his PhD, Penzias began working at Bell Labs in Holmdel, New Jersey. There, Penzias was able to continue his work in radio astronomy, which led to his work with fellow radio astronomer Robert Wilson. In an attempt to measure the radiation intensity of the Milky Way, the two accidentally discovered the cosmic microwave background (CMB) radiation, the relic radiation left over from the big bang.

Penzias rose through numerous levels of leadership at Bell Labs, eventually becoming vice president of research. As his own astrophysics research wound down, he wrote a book called Ideas and Information on the creation and use of technology in society. When he approached a mandatory retirement age, Penzias left the research and development world for Silicon Valley, where he became involved in the venture capital world.

Robert Wilson was born in Houston, Texas, in 1936. His father worked for an oil well service company, and while in high school Robert often accompanied his father into the oil fields. His parents were both “inveterate do-it-yourselfers,” Wilson wrote, and he gained a particular fondness for electronics from his father. As a high school student, Robert enjoyed repairing radios and television sets.

Wilson attended Rice University, where he majored in physics. He obtained his PhD in physics at Caltech, where he worked with radio astronomer John Bolton on expanding a radio map of the Milky Way. After graduation, he joined Bell Labs’ radio research department. Together, Wilson and Penzias made numerous discoveries using radio astronomy, including a surprising abundance of carbon monoxide in the Milky Way and their Nobel Prize–winning discovery of the CMB.

George Smoot grew up attending university biology courses with his mother. Both parents had resumed their college educations after World War II and two children, and watching his parents study, learn, and dedicate time to education had a strong influence on George. After some financial difficulties, the family moved to Alaska, where George spent his time outside exploring and studying the night sky.

George’s father worked for the United States Geological Survey, and as his reputation as a field scientist grew, he traveled around the world to gather data on the properties and water flow of rivers. George’s parents played a shaping role in his life through high school, as his father tutored him in trigonometry and calculus while his mother gave him lessons in science and history.

Smoot attended the Massachusetts Institute of Technology (MIT), where he majored in mathematics and physics. He stayed at MIT for his PhD and then moved to Berkeley to work on particle physics at the Lawrence Berkeley National Laboratory. There, he worked on the High-Altitude Particle Physics Experiment, in which Smoot and his colleagues searched for evidence of the big bang using balloon-borne detectors that would look for antimatter in cosmic rays.

Smoot eventually changed his focus to studying the CMB for more information about the early universe, which led to his Nobel Prize–winning discovery of fluctuations in the CMB.

Over the twentieth century, the big bang theory slowly fell into place. In the next chapter, we’ll discuss the initial versions of the theory and the current big bang model of cosmology.