Meet the people behind the experiments searching for answers to how our universe began

Reported by Giles Sparrow

© Tobias Roetsch

The universe he universe almost seems to have come out of nowhere. A concoction of high temperatures T and a thick gloop of exotic particles that would go into an overdrive of expansion through several phases of varying conditions to create the universe as we see it today some 13.8 billion years later: the Big Bang, creator of time and space – or at least that’s what our current understanding of how our universe sprang into existence leads us to believe.

But what we have come to learn about the cosmos’ somewhat mysterious past wasn’t always as tacked down, going back to the days of Georges Lemaître, who would later be dubbed the father of the Big Bang theory. What the Belgian priest, astronomer and professor of physics did suspect back in 1927, based on his solutions to Albert Einstein’s equations, was that the universe must have sparked into life from a single point at the beginning of time before driving headlong into an expansion.

“The evolution of the world can be compared to a display of fireworks that has just ended; some few red wisps, ashes and smoke,” Lemaître said of how we were thrown into existence. “Standing on a cooled cinder, we see the slow fading of the suns and we try to recall the vanishing brilliance of the origin of the worlds.”

However, Lemaître wasn’t recognised as the genius he was until later; he published his work in an obscure Belgian scientific journal where few scientists saw it. As such, his chance to go down in history was lost. Instead, an American astronomer was gathering data that would strongly support Lemaître’s theory. Edwin Hubble and his assistant Milton Humason were busy at the eyepiece of a telescope at Mount Wilson Observatory in California, surveying so-called spiral nebulae. These used to be thought of as part of our Milky Way, but Hubble showed that they were island universes in their own right – galaxies like our own millions of light years away. He did this by measuring their redshift. This is just like the pitch of a police siren racing past you. As the police car speeds towards you, the Doppler effect causes the sound waves to bunch up, making the pitch go up. As the police car moves away the sound waves become more stretched and the pitch of the siren falls. In space, objects moving towards us have the wavelength of their light rays compressed into bluer wavelengths, which astronomers term blueshift, while objects moving away have their light stretched into redder wavelengths, hence redshift. Hubble found that almost all the galaxies had redshift, meaning they were all moving away from us according to what became known as Hubble’s law. But if the galaxies are all moving apart, could they once have been much closer together?

In 1931 Lemaître’s work was brought to people’s attention when Arthur Eddington discovered it, but by then Hubble had already made his discoveries. At first Einstein didn’t believe it, but later changed his mind when he saw Hubble’s evidence. A more vocal critic was astronomer Fred Hoyle at Cambridge University, who came up with the name ‘Big Bang’ in derision of the idea, favouring his own steady-state model which described an eternal universe. The Big Bang name stuck, however.

Today the Big Bang is a widely accepted theory. However, we don’t have a photo album of how the universe grew up from an infant, transforming into the veteran of cosmic evolution it is today. Astronomers realised that they had to be resourceful, grabbing hold of any tantalising evidence that our universe was willing to give and combining them with mathematical models. Of course, these clues are communicated to us in the cosmos’ own way, ranging from the crackling of its background noise – the cosmic microwave background (CMB) – to gravitational waves that ripple between its many galaxies.