50 Fun Facts About The Big Bang

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

The figure is 13.787 billion years give or take 20 million, and it agrees with the ages of the oldest stars.

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

He backed the rival steady-state model and later denied he meant the phrase as a put-down.

Hoyle coined the phrase during a 1949 radio broadcast on which broadcaster?

It was the Third Programme; the name did not really catch on until the 1970s.

What was Hoyle's rival theory, with matter created as space expands, called?

In that picture the universe looks roughly the same at any point in time, with no beginning.

Which Belgian priest-physicist proposed the 'primeval atom' in 1931?

Critics complained that a beginning in time smuggled religion into physics, not helped by his being a priest.

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

Friedmann in 1922 and Lemaître in 1927 had predicted the relation from general relativity before Hubble measured it.

Who accidentally discovered the cosmic microwave background in 1964?

The omnidirectional microwave hiss matched predictions made by Alpher, Herman and Gamow around 1950.

The CMB's discoverers received the Nobel Prize in Physics in which year?

By then the radiation had been shown to match a blackbody spectrum in every direction.

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

COBE pinned it at 2.726 K in 1990; newer measurements give 2.7255 K.

Recombination, when atoms formed and the universe turned transparent, came about when?

The photons that last scattered then are what we now see as the microwave background.

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

Most protons stayed single as hydrogen; the temperature was about a billion kelvin at the time.

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

It resolved the horizon, flatness and monopole problems, though some of its own founders now doubt it.

During inflation the universe doubled in size more than how many times?

That happened in a span a billion trillion times shorter than a trillionth of a second.

Inflation fixes the flatness puzzle and which other puzzle about the CMB's uniformity?

Without inflation, regions more than about two degrees apart on the sky could never have shared a temperature.

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

None has ever been found; inflation sweeps such point defects out of the observable universe.

Dark energy makes up roughly what share of the universe's mass-energy density?

Dark matter is about 27 per cent and everything luminous less than 5.

Luminous matter such as stars makes up less than what share of the universe's density?

The rest is dark matter and dark energy, neither of which has been detected directly.

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

His result contradicted the static universe Einstein favoured at the time.

Who measured the first Doppler shift of a 'spiral nebula' in 1912?

He found almost all of them receding but did not grasp what that meant for cosmology.

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

His 1924 measurements showed the spiral nebulae were separate galaxies, not part of the Milky Way.

Who assisted Hubble in the 1929 work that produced Hubble's law?

Most of the redshifts they used had been measured earlier by Vesto Slipher.

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

Their prediction dated from around 1950, fourteen years before the radiation was stumbled upon.

What did George Gamow call the primordial material of the early universe?

Lemaître preferred 'primeval atom' for the same hot, dense starting state.

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

The anisotropies, found in 1992, were at the level of about one part in 100,000.

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

John Mather and George Smoot led the two key results from the satellite.

WMAP measured the Hubble constant at roughly what value?

Its figure was 70.4 km/s/Mpc; CMB-based and supernova-based values still disagree slightly.

What is the mismatch between CMB-based and supernova-based expansion rates called?

The CMB route gives a lower number than the local measurements do.

The puzzle of why the universe holds far more matter than antimatter is called what?

The early excess was tiny, of the order of one part in tens of millions, but it is everything we see.

The requirements for baryogenesis to create a matter excess are known as whose conditions?

They demand baryon-number violation, C and CP violation, and a departure from equilibrium.

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

Their redshift-magnitude relation showed the speed-up began when the universe was about half its present age.

The expansion has been accelerating since the universe was what fraction of its age?

Earlier, with everything closer together, gravity won and the expansion was slowing.

In its simplest form, dark energy is modelled as which term in Einstein's field equations?

The mismatch between its measured value and the naive Planck-scale prediction has been called physics' most embarrassing problem.

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

They measured the typical angular size of CMB anisotropies on the sky.

What is the standard model pairing dark energy with cold dark matter called?

It uses quantum mechanics and general relativity to describe everything after the inflationary epoch.

What alternative name stresses that expansion happens at every point, not from one spot?

Critics note the usual name wrongly evokes an explosion into surrounding space, and a sound.

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

No entry was judged good enough, so the name Hoyle tossed off in 1949 stuck.

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

A theory of quantum gravity may yet remove the singularity, which comes from extrapolating general relativity.

The Planck epoch, when the four forces may have been unified, lasted until about when?

Temperatures were near 10³² K and even the concept of a particle breaks down.

The electromagnetic and weak forces separated at roughly what time after the Big Bang?

After about 10⁻¹¹ seconds the physics becomes testable, since particle accelerators can reach those energies.

Quarks and gluons combined into protons and neutrons at roughly what time?

Electrons and positrons annihilated about a second in, leaving a universe dominated by photons.

In which scenario does phantom dark energy eventually tear apart even atoms?

It requires dark energy whose density grows with time rather than staying constant.

If density exceeded the critical value, the universe could recollapse in what scenario?

Before dark energy was found this and an endless slow expansion were the two options on the table.

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

Even carbon, oxygen and silicon were absent, so the clouds likely date from the first minutes.

Predicted and observed abundances of which light isotope differ by a factor of about two?

Deuterium matches beautifully, which is why the mismatch is called a 'problem' rather than a refutation.

The cosmological principle says that on large scales the universe is homogeneous and what?

It has been checked to one part in 100,000 using the temperature of the CMB.

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

Lemaître replied that space and time would only start to mean anything once the first quantum had divided.

Friedmann's 1922 result contradicted which physicist's static model of the universe?

Einstein later advocated an oscillating universe with Richard Tolman instead.

Which astronomer proposed the 'tired light' alternative to cosmic expansion in the 1930s?

He also coined 'dark matter' and 'supernova'; tired light never explained the data as well.

What event turned inflation's energy into a hot plasma, starting the hot Big Bang?

Its temperature is unknown but must have been somewhere between 10¹¹ and 10²⁹ kelvin.

Which of these is one of the 'four pillars' of observational evidence for the Big Bang?

The others are Hubble's law, the microwave background, and the growth of galaxies and large-scale structure.