The History of the Universe and the Big Bang

A large oval speckled with small blue, green, yellow and red spots, like a multicoloured leopard skin. — All-sky map showing the oldest light in the Universe, produced from nine years of measurements by the WMAP probe: the colours show tiny differences in temperature, the seeds of future galaxies (NASA, 2012). NASA / WMAP Science Team, Public domain, source

The name “Big Bang” was first uttered on 28 March 1949, on British radio, by an astronomer who did not believe in the theory.¹

His name was Fred Hoyle. He detested the idea of a Big Bang, and he criticised it until his death, in 2001. This is where the usual story goes wrong.²

The usual story

Almost everywhere, one reads that Hoyle coined the expression in mockery: a ridiculous name, thrown out with contempt, which his opponents then supposedly adopted.³

It is an excellent story: a scientist derisively invents the name of the theory that will triumph over him. One could hardly ask for better.

The historian of science Helge Kragh finds no solid evidence that Hoyle meant to mock the theory. Hoyle himself always denied any such intention.⁴

What Kragh finds is more mundane. On the radio, Hoyle had only the spoken word, with no pictures or diagrams, and he was constantly searching for mental images: this is what he himself explained in 1989. He dropped the expression in passing, three times in a twenty-minute talk. Critics at the time barely noticed the word. Kragh returned to the question in the journal Nature in 2024, for the expression’s 75th anniversary.⁵

A clarification is needed: Hoyle did indeed oppose this theory. He called it “irrational” in that very talk, and he remained an opponent of it until his death in 2001. What is corrected here is the intention attributed to him at the moment he coined the word — not his opposition.⁶

He himself, in 1995, summed up what had happened to him with a neat phrase: words are like harpoons — once they go in, they are very hard to pull out.⁷

The word took a long time to catch on. Between 1950 and 1965, Hoyle no longer used it at all, and physicists were still writing it in quotation marks in the 1960s.⁸

A misleading name nonetheless

“Big Bang” means “a great boom”. The word evokes an explosion: something that bursts at one point, in a pre-existing space, and throws out debris.

That is not what the theory describes. There is no centre, no particular place where it happened, and nothing is scattering into the empty space around it.

What does the theory actually say?

It is not a theory of the origin. It describes how the Universe evolved from a very hot, very dense state. It does not say what triggered it, nor what came “before”.
It is space itself that grows. It is not an explosion in space. Nothing moves through space the way a fragment would.
There is no centre. On large scales, every galaxy sees the others moving away from it (except its immediate neighbours, which gravity holds back: Andromeda, for example, is approaching us). To the question “where did it happen?”, the answer is: everywhere — including the very spot where the reader is.
In short: in the past, the Universe was hotter and denser. Since then, space has expanded and the Universe has cooled. “Bigger” does not mean that matter is scattering: it is the container (space) that grows.

What physicists made of the word

Several major physics textbooks avoided it. In an encyclopaedic treatise on astrophysics, two Russian authors do without it entirely: they speak of a singular beginning of the universe, and use throughout the phrase “theory of the hot Universe”. The word only really spread in the 1970s, and only much later among the general public.⁹

Cosmologists have explained why. The astronomer George McVittie considered the term “loaded with inappropriate connotations” — that of an exploding bomb — and regretted that an expression introduced so casually had enjoyed such success.¹⁰

There have been attempts to replace it, serious and well resourced.

In 1993, a major science magazine launched a worldwide contest to rename the Big Bang. It received more than thirteen thousand entries from forty-one countries.¹¹

The jury chose none of them. It judged that none was as simple or as evocative as the name it was meant to replace, and declared that the contest had no winner.¹²

The word was too short, too striking. It prevailed everywhere, including among those who think it a poor one.

Two ways of measuring, two results

The age of the Universe is often given as an established fact: 13.8 billion years. But this figure depends on a measurement that is now under debate.¹³

The age of the Universe is not measured directly: what is measured is the speed at which galaxies are receding (the Hubble constant, written H₀), and from there one works back in time. The trouble is that the two main methods of measurement do not give the same result.

Method	Target observed	Expansion rate (H₀)*
Early Universe	Light of the cosmic microwave background	67.4
Nearby Universe	Variable stars and supernovae	~ 73

Sources for the table¹⁴

(Unit: km/s/Mpc. What matters is the gap between the two values.)

The gap is larger than the margins of error: the Planck team already put it at 3.6 times the uncertainty. The 13.8 billion years are calculated from the early-Universe value. If the local value prevails, either the age estimate or the model itself will have to be revised.¹⁵

An error sought in vain

Suspicion first fell on a bias in the local measurements: neighbouring stars confused with the Cepheids, for lack of sufficient resolution. The James Webb Space Telescope, far sharper than Hubble, observed more than a thousand Cepheids and ruled out this explanation — the team considers it rejected with greater confidence than that of the tension itself.¹⁶

Another team, however, using the same telescope and other types of stars, finds an intermediate value, 70.4, which it considers consistent with the standard model without new physics. The debate remains open.¹⁷

A recent review counts more than a dozen ways of measuring H₀, all of which should agree. Their values cluster into two camps, one around 68, the other around 73. That leaves only three possible outcomes, none of which commands a consensus:¹⁸

A systematic error still invisible in the data or in their interpretation;
A change to the physics of the very earliest times;
Or a global modification of the model, touching its most fundamental assumptions.¹⁹

What remains for us to discover

What remains unknown about the Universe is still immense. The disagreement over H₀ is one example: two ways of measuring, both careful, that refuse to agree. Researchers had been looking for a deviation from the standard model for twenty years; the one they may have found, three of them write, makes them wish they could put the genie back in the bottle.²⁰

This is not a weakness of science: it is precisely the frontier where it is at work today.

Note 1

On 28 March 1949 Hoyle gave a twenty-minute's talk on the new cosmological theory to BBC's Third Programme […] This is the origin of the cosmological term “big bang,” which Hoyle mentioned three times. At the end of his talk, Hoyle made it clear that he found this kind of theory unacceptable on both scientific and philosophical grounds

Kragh, Helge, “What’s in a Name: History and Meanings of the Term "Big Bang"”, preprint, 2013