Marcel Christ/Gallerystock By Jon Cartwright WE ARE told it was big, yet it was probably unimaginably small. We are told there was a bang, yet there was apparently no sound, and no space for anything to explode into. Some think it might have happened multiple times, so even its definite article is in doubt. Although everyone has heard of the big bang, no one can say confidently what it was like. After all, recounting the beginning of time is about finding not just the right words, but the right physics – and ever since the big bang entered the popular lexicon, that physics has been murky. Perhaps no longer, thanks to an unusual way of delving into our universe’s backstory that has emerged over the past few years. In this view, the essence of space and time can exist beyond the confines of the cosmos, but in a state of roiling chaos we would not recognise. The big bang is not a hard-and-fast beginning, but a moment of profound transformation – one quite different from anything most of us could have imagined. Though often misattributed to the US astronomer Edwin Hubble, the basic idea of the big bang dates back to the Belgian priest and astronomer Georges Lemaître, who observed in the late 1920s that the universe is expanding. Extrapolating backwards, Lemaître imagined a “primeval atom” that ballooned into everything we see today. What was this primeval atom, and where did it come from?