The Battle for the Cosmos!

by Nicholas Mee on August 20, 2017

An illustration from one of Gamow’s popular science classics showing Mr Tompkins travelling at relativistic speeds on his bicycle.

Following the Second World War, a battle for the origin of the universe was waged by two teams of nuclear physicists; one led by George Gamow, the other by Fred Hoyle. Both would be incredibly successful, but not quite in the ways they expected.

Gamow was a brilliant physicist from Russia who gained international acclaim at a young age for using the new quantum theory to understand radioactive decay. Gamow had an irrepressible sense of humour and was a great promoter of science, explaining the latest scientific ideas through the adventures of a certain Mr Tompkins.

Hoyle was a leading British astrophysicist who, like Gamow, was an avid science communicator, writing science fiction novels and television series, as well as presenting BBC radio programmes. Hoyle was arch critic of the view that the universe began in the relatively recent past. Speaking on BBC Radio in 1950 he dismissed the idea of its eruption and expansion from an incredibly hot, dense fireball as simply The Big Bang Theory.

The Steady State Theory

Hoyle considered fundamental biochemistry to be so complex that the origin of life was almost inconceivably improbable; so improbable that even billions of years were insufficient for it to arise naturally. He believed that life could only exist in an eternal universe, spreading to infect the entire cosmos from one star system to the next – a notion known as panspermia.

Hoyle imagined the universe to be everlasting and spatially infinite. He thought it should look pretty much the same when viewed from any point and at any time. Along with two colleagues, Thomas Gold and Hermann Bondi, Hoyle developed a highly original model of the universe based on this assumption and published it in 1948 as The Steady State Theory.

The biggest challenge for the Steady Statesmen was to explain how an expanding universe might appear unchanging, as the expansion should thin out the matter it contains. Their solution was to postulate the continuous creation of matter at a rate that would compensate for this dissipation and maintain the universe’s observed average density. Most of the universe is very empty space, so the required rate of matter creation is tiny. They argued that, if we are prepared to allow the appearance of huge quantities of matter at one point in time – the Big Bang – why shy away from continuous creation of matter in quantities so tiny that it could not be detected? Afterall, if the laws of physics are presumed to be constant, it is more reasonable that matter should be created continuously rather than in a single miraculous event.

So which is correct Big Bang or Steady State? There appeared to be one way to settle the debate. The universe contains a diverse array of different atoms. According to Gamow they must have been synthesised during the Big Bang. According to Hoyle they were forged in the stars. But who was right? The battle lines were drawn, the whole universe was at stake.

The A, B, C of Cosmology

Many physicists in the United States spent the war years developing nuclear weapons in the Manhattan Project. Gamow would have been ideally suited for a role in the project, but did not have the security clearance. Throughout the 1940s he led a team researching nuclear physics at George Washington University in the American capital.

Gamow gave the task of working out the details of how atoms were created in the Big Bang to his research student Ralph Alpher for his PhD thesis. When Alpher was preparing his dissertation for publication in 1948, Gamow insisted they must ask the nuclear physicist Hans Bethe to contribute to the paper. He explained that Bethe was such a great physicist he would certainly have important insights to add and it would be wonderful if their account of the origin of the universe was authored by Alpher, Bethe and Gamow. (Alpha, beta and gamma are the first three letters of the Greek alphabet used by physicists every day in their mathematical notation.) So the paper The Origin of the Chemical Elements duly appeared with the three alphabetical authors. Unfortunately, the main thrust of the paper is incorrect. During the Big Bang, the extreme temperatures required for nuclear fusion did not last long enough for the creation of atoms beyond the lightest: hydrogen, helium and lithium.

Gamow later joked that when physicist Robert Herman joined the team, he stubbornly refused to change his name to Delter (delta being the fourth letter of the Greek alphabet).

Robert Hermann (left) and Ralph Alpher (right) opening a bottle of ylem.

The Genie in the Bottle

Gamow and Alpher named the original material of the universe ylem from an obscure Middle English theological term derived from the Greek hule or hyle – the primordial substance from which matter is formed in Aristotelian philosophy. The genie Gamow is emerging from a bottle of ylem in the photograph on the right.

The Hot Big Bang

When not joking around, Gamow’s team did some serious cosmology.

Alpher and Herman realised the Big Bang had a consequence that could be tested. If the theory was correct, the universe was originally filled with photons scattering off charged particles such as electrons and protons. It would have cooled as it expanded until after a few hundred thousand years the protons and electrons combined into hydrogen atoms. As hydrogen gas is transparent, the photons would no longer interact with the matter. So, if the Big Bang really happened, it should be possible to detect this left over radiation from the early universe.

Each photon last interacted with a charged particle soon after the Big Bang when the average matter temperature was 3100 degrees, so the spectrum of the radiation would be characteristic of that produced by matter at this temperature. The dramatic expansion of the universe since then would produce an extreme red shift of the radiation. Alpher and Herman estimated that it would now be in the microwave range with the signature of radiation emitted by matter at a temperature of just 5 degrees above absolute zero.

Forging Atoms in the Stars

Meanwhile Gamow’s intellectual adversary Hoyle worked out the physics of nuclear fusion in stars. Hoyle’s earliest papers were written in the late 1940s and early 1950s. Like all science, nuclear physics is a collaborative enterprise, so Hoyle built on critical ideas developed by Gamow, Bethe and others. The details of the forging of atoms in stars were presented in a big review paper published in 1957 known as B²FH after its authors Burbage, Burbage, Fowler and Hoyle, where Burbage and Burbage are the husband and wife team Geoffrey and Margaret Burbage, and Fowler is Willy Fowler. Although Hoyle is recognised as the architect of the theory of stellar nucleosynthesis, Fowler was the only member of the B²FH collaboration to receive the Nobel Prize.

Butterfly Nebula Credit: ESA/Hubble

Hoyle and his collaborators were correct. Apart from a few of the very lightest elements, all the atoms of the Periodic Table were created in stars or supernova explosions. The outer layers of ageing stars swell and eventually drift away into space producing planetary nebulae. The image above shows a particularly beautiful example. Much of the material created in stars is released back into space where it merges into the gas clouds from which subsequent generations of stars condense.

So does this mean we live in a steady state universe? No, Hoyle had won the battle of the chemical elements, but he would ultimately lose the war for the cosmos.

The Background Noise of the Universe

Penzias and Wilson in front of their horn antenna.

In 1964, Arno Penzias and Robert Wilson built a sensitive horn antenna for Bell Labs in New Jersey. Their receiver was plagued with noise which they assumed to be due to a fault in their equipment. They tried everything to eradicate the noise, but without success. Eventually, the explanation was provided by the Princeton astrophysicists Robert Dicke, Jim Peebles and David Wilkinson.

Penzias and Wilson had discovered the cosmic microwave background, the relic radiation from the Big Bang predicted by Alpher and Herman.

Measurements show it is identical to electromagnetic radiation emitted by matter at a temperature of 2.7 degrees above zero. This is 1100th of the temperature when it last interacted with matter in the early universe and somewhat lower than the estimate of Alpher and Herman because the age of universe and other relevant cosmic parameters were not known with great accuracy at the time of their writing.

Map of the tiny variations in temperature of the cosmic microwave background across the whole sky as mapped by the probe WMAP (Wilkinson Microwave Anisotropy Probe). Credit: NASA.

The cosmic microwave background has been studied in detail by a series of space probes. When local effects due to our motion are taken into account, it is almost perfectly uniform across the entire sky. There are tiny variations in temperature due to the clumping of matter in the early universe. The regions of higher density are the seeds from which super clusters of galaxies will grow. They have been mapped with great precision and are the best source of information we have about the structure and evolution of the universe. This has given us the most precise age for the universe and has confirmed that most of the mass in the universe is in an unknown form known as dark matter. The only explanation that accounts for the data is that the universe began 13.8 billion years ago in a hot Big Bang.


Further Information

There is more about Fred Hoyle, nuclear fusion and the creation of the elements in stars in my book: Higgs Force: Cosmic Symmetry Shattered.


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