They say that the Big Bang gave birth to the entire universe. So you might think that the Big Bang must have been one hell of an explosion. But technically speaking, the Big Bang wasn’t actually an explosion at all. It couldn’t have been.
The Big Bang theory is the prevailing theory about the “birth” of the universe. It posits a singularity, or super high density state from which the entire universe expanded and continues to expand. But what exactly is the Big Bang, and what’s the evidence that it took place? How do we account for the “Big Bang state”? Was there something before the Big Bang? What does the theory posit about the future of the universe? And what role does philosophy play in answering these mysteries? John and Ken have a singular conversation with Katherine Freese from the University of Michigan, author of The Cosmic Cocktail: Three Parts Dark Matter.
Part of our series A Philosophical Guide to the Cosmos.
The Big Bang must have been one hell of an explosion, John remarks! But Ken says that it likely wasn’t an explosion. An explosion would require matter being thrown out in all directions, and it could not have happened that way – notions like outward or centered only apply to things that happen in a place, and the Big Bang didn’t happen in a place. John is befuddled. The Big Bang happened…nowhere? How could that be, when everything happens somewhere? It’s the very notion of a priori. Ken says this applies only to things after the Big Bang. The Big Bang itself is what created space in the first place. John is still puzzled – so what’s on the other side of space, then? Furthermore, he adds, modern cosmology says the universe is expanding, so it has to be expanding into something, that something being pre-existing empty space. And what caused the Big Bang? Causes precede their effects in time! If nothing preceded the Big Bang, where did it come from? The two discuss these questions and more in the upcoming segments.
John and Ken welcome guest Katherine Freese, Professor of Physics at the University of Michigan and author of The Cosmic Cocktail: Three Parts Dark Matter. John asks Katherine what got her interested in studying the hard, deep, esoteric questions about the origins of the universe. She explains that she went to an all-girls high school that didn’t offer physics, so she took a summer school class, and by the time they got to Einstein’s theory of relativity, she was sold. She majored in physics in college, and the rest unfolded. John follows up on his opening statements: if the Big Bang wasn’t an explosion, then just what was it? Katherine explains that the very earliest times of the universe were basically a primordial soup of densely packed particles – of quarks, electrons, dark matter particles, and so forth. These interacted with each other constantly, and as the universe began to cool down, some of these particles began to merge. What it comes down to, Katherine says, is: the universe started off as really hot, then began cooling down and expanding to create the structures – stars, galaxies – that we now recognize. The expansion wasn’t sudden, it wasn’t an explosion, per se. Ken then wonders about how much space there really was at the beginning. Katherine explains that if the universe is infinite, as scientists now believe, then even if you squeeze all the things in the universe tightly together, you still have some degree of things you cannot condense.
Ken asks Katherine about the pillars of the Big Bang. This includes wondering what the role of background microwave radiation plays in the Big Bang. Microwave radiation is everywhere, Katherine explains, and the hot early phase needed to happen to give rise to the photons that we have today. Ken also asks Katherine: what does dark matter have to do with the Big Bang? Katherine responds by adding another question to the mix: what is the universe made of? Everything – from our bodies to the stars – only adds up to 5% of the universe. So what is the other 95%? The trio discuss.
Katherine, John, and Ken welcome questions from the audience, and they continue the discussion by tackling questions such as: was there an order to the creation of the elements? What’s the origin of the nomenclature “Dark Matter?” Is it because we don’t understand it, or is it due to something else?
• Roving Philosophical Reporter (Seek to 7:58): Shuka Kalantari tracks down the ultimate origins of the universe with Lawrence Krauss, from Arizona State University. He discusses two theories for what came before the Big Bang: either nothing or a multiverse. He discusses how we cannot seek a cause for the Big Bang, because the notion of cause and effect is tied to space and time, which did not exist pre-Big Bang.
• 60-Second Philosopher (Seek to 48:30): Ian Shoales starts from the beginning and speeds through the role of faith in understanding the beginning of the universe.