Before the Big Bang

According to a recent theory, the origin of the universe was not an explosion that created everything out of nothing but might instead be the result of a “bounce” from a previous universe: the so-called Big Bounce. We live in a universe that began around 13.8 billion years ago with the Big Bang: since then, space has been expanding and galaxies have been moving away from one another. In the 1990s it was discovered that this expansion is not slowing down but accelerating: something we call “dark energy” seems to be pushing space outwards. On this basis, theorists such as Professor Henry Tye have suggested that what we call the “beginning” may in fact be just the expanding phase of a complete cycle. Before the expansion, they argue, there would have been a phase of contraction. When the universe became extremely dense, gravity would have reversed the trend and triggered a bounce: this, in turn, would give rise to a new expanding universe. In this picture, the Big Bang would not be an absolute beginning, but the central point in a much larger cycle. Our current universe could therefore be just the latest “restart”. Some models suggest that dark energy changes over time and that one day the expansion will stop, followed by a final contraction – a “Big Crunch” – and then a new bounce.

The most intriguing part is that this cycle could happen many times over: the universe collapses… then bounces… then collapses again… and so on. Our universe might be just one in a very long series. For now, we do not know whether this theory is correct. It is extremely difficult to study something that happened so long ago. Scientists are looking for clues by observing very distant stars and the ancient light left over from the Big Bang. One day they might discover whether our universe really did have a “before”. To make progress, more precise observations are needed, such as detailed studies of distant galaxies and of the relic radiation that fills the universe, which might reveal traces of the era preceding the bounce. In any case, this theory overturns the idea of a single, unique beginning for time and space, and opens the door to a cyclic or “eternal” universe. Even if we cannot yet say with certainty what happened “before”, the very fact that we can ask the question is already a major step towards a deeper understanding of the cosmos.