What was the Universe like before the Big Bang?

Unfortunately, there is no tool developed by science that allows us to look back in time with absolute clarity. If there was, then deciphering all the mysteries of the universe would be a much easier task! But, because of this, the best researchers can do is to create formulas and models to predict past events. The Big Bang Theory is currently the best and most widely accepted scientific model for universal creation that we have. It tries to determine how the universe was in its earliest moments, broadly arguing that all of spacetime expanded out of one singularity in almost an instant. Space and time as we know it came into existence with this inflationary event. And we can see, by measuring that other galaxies are still receding away from us (and at an increasing rate!), that the expansion at the heart of it all is still happening today… a phenomenon first noticed by the iconic astronomer, Edwin Hubble, in the 1920s. What’s surprising is that while the name “big bang” was first used by the astronomer Fred Hoyle, he himself firmly rejected the entire theory - with it said that he coined the term to show what he believed to be the absurdity of the model. 

Whatever Hoyle’s reason for coming up with one of the most recognisable scientific terms of the modern world, however, contrary to popular misconception the Big Bang almost certainly wasn’t an explosion. Rather than it all being as though a cosmic bomb just detonated into nothingness, NASA more readily offers a different explanation for what the Big Bang actually was - usually using the metaphor of raisin bread expanding in an oven. As the bread expands, the galaxies, or raisins, spread further and further apart. And, in fact, because expansion is still happening, the raisin bread is still baking. We also have Cosmic Microwave Background Radiation to help us understand what’s going on. It’s the leftover radiation and heat from the big bang, so we can map to where and how far the universe has reached. It’s visualised in splotchy blue-to-red maps, detailing the faint glow of the oldest radiation we know of. And it, along with the Big Bang theory as a whole, provides us with nearly everything we know about the beginning of our universe. Before all of that, though… before all the expansion, radiation and acceleration, there’s a general consensus that the universe was focused on a single point, about the size of a grapefruit. All of the matter that we now know about was housed inside this point, and it was hotter than anything we’ve since seen in the cosmos at multiple quadrillions of degrees. For contrast, the hottest temperature we’ve ever clocked is at least 7.2 trillion degrees Fahrenheit (or around 4 trillion degrees Celsius), achieved by smashing together particles in the Large Hadron Collider. But, at a time before the Big Bang, temperatures were far, far greater than even this. So, we have a vaguely mind-blowing idea of how hot it was. But, otherwise, we run into various problems when going this far back. Scientists are only really comfortable travelling to about a second after the big bang, because any further - any closer to the event itself - and most of our equations stop making sense. That’s because classical physics begins to fall apart when it encounters the world of the very small, in general. It’s no secret that quantum physics and quantum mechanics can at times make a mockery of the laws of nature that are otherwise irrefutable on the macro scale. But, in the first second post-big-bang, we’re imagining literally everything - the entire universe - governed by quantum rules. And that’s just a cosmic jumble that so far no one can decipher! 

What we can still say is that at the very beginning what would have existed is an infinitely dense and infinitely small singularity, with it commonly suggested that just nothing existed before. But… that doesn’t really make sense. How can something come of nothing? It’s arguably the ultimate question in science… but some scientists argue that the question itself doesn’t make sense, either. According to Stephen Hawking, for example, time essentially began with the big bang, and so to ask what came before isn’t a real question… because the events before, without time to apply to them, are undefined and immeasurable. Hawking doesn’t necessarily speak for all scientists, however, and there are other theories as to what predated the universe’s creation. For one, some string theorists believe they have the answer. The Ekpyrotic, or conflagration, scenario, says that the cosmos is cyclical in nature and continues to shift from birth to rebirth. To understand this, we need to look at one of the possible ways our universe could end… called the Big Crunch. The Big Crunch is the idea that all matter eventually stops expanding and contracts back in on itself to a single point, like a reverse big bang. In the Ekpyrotic scenario, though, the universe does this and then rebounds out in another big bang, continuing on indefinitely. In the context of today’s question, this means that before the big bang… there was another universe contracting in upon itself. It could even have been filled with lifeforms just like us, or something very different. Or it could have been totally and universally strange to us, with a different makeup and different physics. 

Whatever the case, our current universe is just all of that ancient matter being randomly recycled after a fiery death - so the theory goes. In some other versions of this idea, however, the re-distribution of the universe actually isn’t random, but is instead precisely symmetrical. With time moving backwards in the period before the big bang happened. In general, physics can work just as well with time moving backwards as it does moving forwards… but now we have a proposed mirror world where any one spot in time corresponds to the same instance on our own 13.8-billion-year timeline. In this way, the mirror universe is our future and we are its past. As for how this is structured, there are some ideas that pre and post big bang exist on either side of a huge black hole. A cosmic enormity to account for our half of everything, as well as all of the other side. String theory isn’t the only place to find alternative creation models, however. And there are other ideas on how all of this started, which don’t necessitate linked-up universes to balance it out. The physicist Sean Carrol, for example, theorizes a universe that could have been the by-product of another, larger universe entirely. In this view, a region of spacetime gets ripped off from the hypothesized parent universe as a result of quantum randomness. And, in the case of one particular region of spacetime, it just so happens that it went on to account for everything we know to exist. If this were true, then it’s a process seemingly just as likely to occur in different regions of the parent dimension… to form different, some might say parallel, universes. And, for today’s video, we can say that before the big bang the universe wasn’t “like” anything… because it truly didn’t exist yet. But, also, that something did exist… out of which our universe was born. Were the same rules to apply to that higher plane, too, then it might’ve also been created in the same way… as may an even higher plane, still… and the same process could theoretically continue into infinity. Which really makes our universe feel like just a tiny cog in the cosmological machine… even if just the observable part of it is gigantic enough from our perspective, to the tune of ninety-three billion lightyears across! Unfortunately, our current understanding of physics simply isn’t enough to glean with certainty what reality was like before the big bang. We do, though, have a number of theories. One is that there was pure nothingness… and. then, a rush of matter and energy. Others argue that this universe is actually the latest in a chain of universes, and so those are what existed beforehand. Or that this universe is simply one of many, unconnected masses… like shells on a beach, or driftwood in the ocean. Until we can untangle the quantum chaos that existed in the first few seconds, we might never know for sure.