50 Fun Facts About The Big Bang

How old do expansion-rate measurements say the universe is?

About 13.8 billion years. At times in the 20th century the sums made the universe look younger than its own oldest stars, a clash settled only by better measurements and the discovery of dark energy.

Which astronomer is credited with coining the term 'Big Bang' in 1949?

Fred Hoyle. He never accepted the theory he had named, and later insisted the phrase was no insult, just a vivid image to help radio listeners tell two rival cosmologies apart.

The name 'Big Bang' was first spoken in a 1949 radio talk on which broadcaster?

BBC. The talk went out on its Third Programme and was printed days later in its magazine The Listener, yet scientists largely ignored the catchy name until the 1970s.

Which rival theory to the Big Bang had new matter continually created as the universe expands?

Steady-state model. It gave the universe no beginning and no end, looking much the same forever; counts of faint radio galaxies and then the 1964 microwave hiss showed the cosmos had changed.

Which priest-physicist proposed in 1931 that the universe began as a 'primeval atom'?

Georges Lemaître. He lived just long enough to see it confirmed: news that the theory's predicted afterglow had been detected reached him when he was already gravely ill, and he died in 1966.

Hubble's law says a galaxy's recession speed rises in proportion to what?

Its distance. Think of raisin bread rising: as the dough swells, every raisin sees all the others move away, the far ones fastest, so the law is simply what a uniform stretching of space looks like.

Who accidentally discovered the cosmic microwave background in 1964?

Penzias and Wilson. They were trying to get rid of the hiss, not find it, while a team at nearby Princeton was preparing to hunt for exactly that signal; its leader told colleagues, "We've been scooped."

The discoverers of the cosmic microwave background suspected its hiss came from which birds' droppings?

Pigeons. The birds were nesting inside the horn antenna, so the two men evicted them and swept out the droppings; the hiss stayed, and it won the pair the 1978 Nobel Prize in Physics.

The cosmic microwave background today corresponds to a temperature of roughly what?

2.7 K. That is about minus 270 degrees Celsius; the same light was some 3,000 K when it was released, and the expansion of space has been stretching and cooling it ever since.

About how long after the Big Bang did the first atoms form, leaving the universe transparent to light?

380,000 years. Until then free electrons scattered light like a fog; once atoms captured them, light could cross space unhindered, and that first free light is still arriving today.

Minutes after the Big Bang, neutrons and protons fused into nuclei of which element?

Helium. About a quarter of all normal matter by mass became helium in roughly five minutes; then the universe grew too cool and thin for fusion, and most of today's supply dates from that burst.

Who introduced the idea of an early epoch of rapid expansion, 'inflation', in 1981?

Alan Guth. He was a 32-year-old postdoc on his fourth temporary post, unable to land a permanent job, when the idea came to him late one night in December 1979.

Which space telescope, launched in 2021, was built to see the first galaxies that formed after the Big Bang?

Webb. Its gold-coated mirror, 6.5 metres across, was too wide for any rocket, so it was launched folded like origami and opened itself in space, 1.5 million kilometres from Earth.

Opposite sides of the sky share one temperature though seemingly never in contact, a puzzle called what?

Horizon problem. Light has not had time to cross between opposite sides of the sky, so they should never have evened out; inflation says they were close neighbours before being flung apart.

Grand unified theories predicted a glut of which objects that inflation dilutes away?

Magnetic monopoles. Cut a bar magnet in two and each piece still has a north and a south pole; a lone pole would be a new kind of particle, and as of 2025 no search had confirmed one.

Dark matter and dark energy aside, what makes up 5% of the universe?

Ordinary atoms. Every star, planet and person is built from them, yet they are only about a twentieth of the cosmic budget; dark energy takes roughly 68% and dark matter about 27%.

Which element, left over from the Big Bang, still makes up about three-quarters of all normal matter by mass?

Hydrogen. Its nucleus is a single proton, and most protons never fused with anything in the first few minutes, so the simplest element still outweighs all the others put together.

Which mathematician derived the expanding-universe equations from general relativity in 1922?

Alexander Friedmann. He had flown bombing raids in the First World War, and in July 1925 he rode a balloon to a record 7,400 metres, only to die of typhoid two months later at 37.

Before Hubble, who first measured the speed of a 'spiral nebula' in 1912?

Vesto Slipher. His first target, Andromeda, turned out to be rushing toward us at about 300 km a second; only as he added more spirals did nearly all the rest prove to be racing away.

Hubble measured galaxies' remoteness with the 100-inch Hooker reflector at which observatory?

Mount Wilson. There in California in 1923 he photographed a single flickering star in Andromeda that proved the 'nebula' lay far outside the Milky Way, a whole other galaxy.

Which former mule driver and janitor helped Hubble gather the data behind Hubble's law?

Milton Humason. He quit school at 14 and never went back, yet he grew so skilled at the telescope that Hubble relied on him to capture the faint spectra of the remotest galaxies.

Which two associates of George Gamow predicted the cosmic background radiation?

Alpher and Herman. In 1948 they predicted a leftover glow about 5 degrees above absolute zero, but the forecast was overlooked, and the Nobel Prize later went to the men who stumbled on it.

George Gamow added which physicist's name to a 1948 Big Bang paper purely to make the author list a Greek-alphabet pun?

Hans Bethe. He had contributed almost nothing to the work; Gamow added him for the joke, dismaying the student co-author, who feared the famous name would eclipse his own.

Which NASA satellite, launched in 1989, found tiny fluctuations in the CMB temperature?

COBE. Its map showed patches only a hundred-thousandth of a degree warmer or cooler than average, the first faint clumping from which galaxies, stars and eventually people would grow.

Who shared the 2006 physics Nobel for mapping the CMB's spectrum and anisotropies?

Mather and Smoot. Their satellite needed only nine minutes of data to trace a perfect heat-glow curve, and when it was shown at an astronomy meeting the audience gave it a standing ovation.

A universe with a beginning helps resolve which old puzzle about why the night sky is dark?

Olbers' paradox. In an endless, ageless universe every line of sight would end on a star and the whole sky would blaze; ours is dark because distant light has not had time to arrive and the oldest light is stretched out of sight.

What is the mismatch between expansion rates measured nearby and inferred from the afterglow called?

Hubble tension. The universe today is expanding faster than its early conditions predict; as of 2024 repeated checks had not closed the gap, leaving open whether it is a measuring error or a sign of new physics.

In theory the Big Bang made matter in equal amounts with what else, so that neither should have survived?

Antimatter. The two destroy each other on contact, and nearly all of both did; a tiny unexplained surplus of matter was left over, and that remnant is every galaxy, star and person.

Whose three conditions, set out in 1967, let the infant universe end up with a surplus of matter?

Sakharov. The father of the Soviet H-bomb wrote them down in 1967, eight years before his campaigning for human rights at home won him the Nobel Peace Prize.

Observations of which objects revealed that the expansion of the universe is accelerating?

Type Ia supernovae. Two rival teams set out to measure how fast the expansion was slowing; both found the far-off explosions dimmer than expected, which meant it was speeding up instead.

Light from galaxies racing away from us is stretched toward which colour?

Red. It is called redshift; a rare galaxy heading our way, like our neighbour Andromeda, shows the opposite, a blueshift, its light squeezed rather than stretched.

Dark energy is most simply modelled by which term, which Einstein added to his equations and later abandoned?

The cosmological constant. Einstein invented it in 1917 to hold the universe still and dropped it once the expansion was discovered; it came back decades later to describe a cosmos that is speeding up.

Experiments such as BOOMERanG in 2000–01 found the universe's spatial geometry to be what?

Almost flat. The telescope hung from a balloon that polar winds carried in a two-week circle around the South Pole and back to its launch site, which is how BOOMERanG earned its name.

What is the standard model pairing dark energy with slow-moving dark matter called?

Lambda-CDM. Lambda stands for dark energy and CDM for cold dark matter; it became the 'concordance' model in the late 1990s, when measurements that had clashed for years finally fitted one recipe.

Where do cosmologists say the Big Bang, often pictured as a central explosion, happened?

Everywhere at once. It was the appearance and stretching of space itself, not a blast into a waiting void, so there is no centre of expansion anywhere to point a telescope at.

Which magazine ran a 1993 competition to find a better name for the Big Bang?

Sky & Telescope. Its judges turned down every suggestion sent in, so a phrase first tossed out in a 1949 radio talk outlasted an organised attempt to replace it.

In 1968–70 Penrose, Hawking and Ellis showed Big Bang models must contain what?

An initial singularity. Hawking took the idea from Penrose's proof that a collapsing star must end in one: run the film backwards, he argued in his doctoral thesis, and an expanding universe must begin in one.

The first 10⁻⁴³ seconds after the Big Bang form an epoch named after which physicist?

Max Planck. He derived the unit in 1899 from nature's constants alone and it was long treated as a curiosity; it now marks the edge of known physics, where gravity and quantum theory collide.

Until a trillionth of a second after the Big Bang, electromagnetism was merged with which force?

The weak force. Above a certain temperature the two act as a single 'electroweak' force; the W and Z particles that carry the weak half were finally caught at CERN in 1983.

About a millionth of a second after the Big Bang, which particles bound together to form the first protons and neutrons?

Quarks. Until then the universe was too hot for them to stick together, a free-flowing soup that physicists recreate for an instant by smashing heavy nuclei together at CERN.

In 2014 a South Pole telescope seemed to catch ripples from cosmic inflation; what had it mostly detected instead?

Dust in the Milky Way. The BICEP2 team's announcement made headlines worldwide, but a joint study with a European space telescope in 2015 found that glowing galactic dust could account for the pattern.

The 1998 discovery that cosmic expansion is speeding up made which proposed ending of the universe unlikely?

Big Crunch. It needs gravity to halt the expansion and haul everything back together, and until 1998 most astronomers assumed the expansion was at least slowing; it turned out to be doing the opposite.

In 2011 astronomers found pristine gas clouds with no heavy elements in the light of what?

Distant quasars. Gas clouds lying in front of them leave dark lines in the quasars' light; two clouds showed no trace of any element forged in stars, only what the first few minutes had made.

The Big Bang theory predicts about three times more of which light element than astronomers find in the oldest stars?

Lithium. The theory's forecasts for the other light elements match what is observed, which is why this one stubborn shortfall is called the cosmological lithium problem rather than a refutation.

Which principle says the universe looks the same from every place, in every direction?

Cosmological principle. It holds only on the largest scales and began as a simplifying assumption; the Big Bang's afterglow later bore it out, matching across the sky to one part in 100,000.

Which astronomer found a beginning of time 'repugnant' and held matter to be eternal?

Arthur Eddington. He had taught the theory's author at Cambridge and in 1931 helped publish that pupil's expanding-universe paper in English, calling it brilliant, yet he could not stomach a first moment.

Which pope told scientists in 1951 that the Big Bang theory bore witness to the moment of creation?

Pius XII. He told the Pontifical Academy of Sciences that science had become 'a witness to that primordial Fiat Lux', Latin for 'Let there be light', while granting that this was not absolute proof of creation.

Which astronomer proposed the 'tired light' alternative to cosmic expansion in 1929?

Fritz Zwicky. He suggested light simply loses energy on its long journey; the idea fails because anything sapping the light would also blur far-off galaxies, and they look sharp.

What name is given to the event that refilled the universe with particles and radiation when inflation ended?

Reheating. Inflation had thinned the universe to almost nothing; when it ended, its stored energy poured into matter and light, and that fireball, not the instant before it, is what physicists call the hot Big Bang.

The horn antenna that first picked up the Big Bang's afterglow had been built to catch radio signals bounced off what?

Balloon satellites. NASA's Project Echo bounced radio signals off giant metal-coated balloons in orbit, so the New Jersey horn built to catch those faint echoes was sensitive enough to hear the sky itself.