What Really Put The ‘Bang’ In The Big Bang?
So what is it that put the “bang” in the hot Big Bang? It’s the end of inflation. There is a state prior to the start of the hot Big Bang that set it up and provided it with the initial conditions of being spatially flat, the same energy density everywhere, always below a certain threshold temperature, and uniform with quantum fluctuations superimposed atop it on all scales.
When this inflationary state ended, the process of cosmic reheating transformed that energy — which had previously been inherent to the fabric of space itself — into particles, antiparticles and radiation. That transition is what put the “bang” in the hot Big Bang, and led to the birth of the observable Universe as we know it. The details of this were first worked out in the 1980s, back when inflation was just a theoretical idea, and have been confirmed by observations taken in the 1990s, 2000s, and 2010s. For decades, scientists have known what put the “bang” in the Big Bang. At last, now the general public can share in that knowledge, too.
Last week, a story came out that claimed to discover what put the “bang” in the Big Bang. Only, the actual study talked about what occurs in a conflagration or an explosion, which is completely unrelated to anything that occurs in the earliest moments of the hot, dense state that kicked off our Universe as we know it. Fortunately, we don’t have to wonder about what put the “bang” in the Big Bang; this is something scientists have known for decades.
The answer? It’s the cosmic reheating that occurs at the end of inflation that gives rise to the first moments of the hot Big Bang. Come get the real, hype-free story today.
What Came First: Inflation Or The Big Bang?
“In fact, our entire observable Universe contains no signatures at all from almost all of its pre-hot-Big-Bang history; only the final 10^-32 seconds (or so) of inflation even leave observably imprinted signatures on our Universe. We do not know where the inflationary state came from, however. It might arise from a pre-existing state that does have a singularity, it might have existed in its inflationary form forever, or the Universe itself might even be cyclical in nature.
There are a lot of people who mean “the initial singularity” when they say “the Big Bang,” and to those people, I say it’s long past due for you to get with the times. The hot Big Bang cannot be extrapolated back to a singularity, but only to the end of an inflationary state that preceded it. We cannot state with any confidence, because there are no signatures of it even in principle, what preceded the very end-stages of inflation. Was there a singularity? Maybe, but even if so, it doesn’t have anything to do with the Big Bang.”
Have you heard that our Universe began some 13.8 billion years ago with the start of the Big Bang? There’s a good chance that some version of that story has made it to you, but it unfortunately has probably gotten to you the same way it got to me: with an error that’s many decades out of date.
What if I told you that you couldn’t extrapolate the Universe back to a singularity, where all the matter and energy was consolidated into a space so tiny that the laws of physics break down?
What if I told you that we have a verified, validated theory of what happened before the Big Bang, and it has (for decades, now) superseded and replaced the idea of an initial singularity as the earliest stages of the Universe?
Meet cosmic inflation, the pre-origin of our Universe that set up and gave rise to the Big Bang, and learn why the naysayers are out of legs to stand on.
Was Dark Matter Really Created Before The Big Bang?
“So if that’s what the observational data points towards, what can we say about where dark matter comes from? A recent headline that made quite a splash claimed that dark matter may have originated before the Big Bang, and many people were confused by this assertion.
It might seem counterintuitive, because the way most people conceive of the Big Bang is as a singular point of infinite density. If you say the Universe is expanding and cooling today, then you can extrapolate it back to a state where all the matter and energy was compressed into a single point in space: a singularity. This corresponds to an initial start time for our Universe — the beginning of our Universe — and that’s the Big Bang.
So how could something that exists in our Universe, like dark matter, have originated before the Big Bang? Because the Big Bang wasn’t actually the beginning of space and time.”
Last month, a paper came out claiming that dark matter may have been created before the Big Bang. Although it might sound implausible, it’s absolutely a possibility that we cannot rule out, although it might be an idea that’s extraordinarily difficult to test when we compare it up against the other options. We have to keep every scenario that hasn’t been ruled out in mind, and understand that despite all we don’t know about dark matter, there’s a ton of indirect evidence brought to us by the full suite of observations at our disposal.
Could dark matter have been created before the Big Bang? Yes, but three other possibilities are maybe even more viable. Come find out why today.
Ask Ethan: Can We Really Get A Universe From Nothing?
“One concept bothers me. Perhaps you can help. I see it in used many places, but never really explained. “A universe from Nothing” and the concept of negative gravity. As I learned my Newtonian physics, you could put the zero point of the gravitational potential anywhere, only differences mattered. However Newtonian physics never deals with situations where matter is created… Can you help solidify this for me, preferably on [a] conceptual level, maybe with a little calculation detail?”
You’ve very likely heard two counterintuitive things about the Universe before. One of them is that the Universe arose from nothing, and this defies our intuition about how it’s impossible to get something from nothing. The second is that we have four fundamental forces in the Universe: gravity, electromagnetism, and the strong and weak nuclear forces. So how, then, do we account for the fact that the Universe’s expansion is accelerating? Isn’t this clearly evidence for a fifth force, one with negative gravity?
Guess what? These two counterintuitive aspects of reality are related. If you understand them both, you’re one step closer to making sense of the Universe.
Could Parallel Universes Be Physically Real?
“Inflation may give us an enormously huge number of Universes that reside within a greater multiverse, but there simply aren’t enough of them to create an alternate, parallel you. The number of possible outcomes simply increases too fast for even an inflationary Universe to contain them all.
In all the multiverse, there is likely only one you. You must make this Universe count, as there is no alternate version of you. Take the dream job. Stand up for yourself. Navigate through the difficulties with no regrets, and go all-out every day of your life. There is no other Universe where this version of you exists, and no future awaiting you other than the one you live into reality. Make it count.”
Our observable Universe, as vast and enormous as it may be, is still finite. There are a finite number of galaxies containing a finite number of atoms and particles that have existed for a finite amount of time since the Big Bang. There’s an idea in quantum physics call the many-worlds interpretation, where all the various quantum outcomes that are possible actually do occur, but they simply occur in parallel Universes: where the Universe was identical to our own until a critical moment when a particular quantum decision occurred.
Does the existence of a multiverse mean there’s a Universe out there where you also exist, but made different decisions? The answer is probably no. Here’s why.
Ask Ethan: How Well Has Cosmic Inflation Been Verified?
“To what margin of error or what level of statistical significance would you say you say inflation has been verified?”
So, you’ve got an alternative theory to our best mainstream scientific ideas? Well, guess what: those are the same shoes that every scientific idea we accept today were wearing at one point in the distant past. The thing that separates them from the ideas that fell by the wayside were three remarkable feats:
1. They reproduced all the earlier successes of the previous prevailing model.
2. They resolved or explained puzzles or problems that the previous model had no sufficient answer for.
3. And, perhaps most importantly, they made new predictions that we could go out and test about the Universe, and those predictions were proven correct by the appropriate experimental or observational test.
Although most people don’t appreciate it, inflation has hurdled all three bars, and has no fewer than four spectacular predictions that have since been confirmed. Come learn how well cosmic inflation has been verified today!
This Is Why The Multiverse Must Exist
“This picture, of huge Universes, far bigger than the meager part that’s observable to us, constantly being created across this exponentially inflating space, is what the Multiverse is all about. It’s not a new, testable scientific prediction, but rather a theoretical consequence that’s unavoidable, based on the laws of physics as they’re understood today. Whether the laws of physics are identical to our own in those other Universes is unknown.
If you have an inflationary Universe that’s governed by quantum physics, a Multiverse is unavoidable. As always, we are collecting as much new, compelling evidence as we can on a continuous basis to better understand the entire cosmos. It may turn out that inflation is wrong, that quantum physics is wrong, or that applying these rules the way we do has some fundamental flaw. But so far, everything adds up. Unless we’ve got something wrong, the Multiverse is inevitable, and the Universe we inhabit is just a minuscule part of it.”
Skeptical about the Multiverse? You’re not alone. After all, how can you be confident that something must exist if the experimental, measurable, or observational evidence that’s required to validate its existence isn’t located within our observable Universe? It’s a reasonable thought, but there are ways to know something that go beyond verifying the exact phenomenon we’re looking for. This is why theoretical physics is so powerful: it not only allows you to draw conclusions about things you have not yet observed, but about things you cannot observe at all.
Come find out how, and learn why the Multiverse really must exist.
Ask Ethan: Are We Deceiving Ourselves By Searching For B-Modes From Inflation?
“I have a question about B-Modes. I’ve read Dr. Keating’s book, Losing the Nobel Prize. In the book, he details his team’s search for B-modes, and claims this would be smoking gun for inflation. Dr. Hossenfelder, in a blog post, says this isn’t true and there are other ways to produce B-modes. What is the correct view?”
Perhaps the greatest danger in science is to go out, look for a predicted effect, find it, and declare victory. Why is that such a danger? Because your idea for how the effect was generated might not be the only possibility, or even the most accurate one. If I have a wild new theory that predicts some far-distant star will have a habitable planet around it, the detection of that planet does not necessarily mean the wild new theory is correct. When it comes to the origin of the Universe, our leading theory is cosmic inflation, which predicts a B-mode polarization signature in the cosmic microwave background. Are there other ways to generate those B-mode signatures, though? And if we find them, does that mean that inflation is correct, or might that be a premature conclusion?
This is a key problem, and a hard problem, in theoretical physics. But we can say a whole lot that’s intelligent on this topic, and still be correct. Let’s find out.
One Universe Is Not Enough
“If you accept that inflation is a stage that occurred in the Universe’s past prior to the hot Big Bang, and that the Universe itself is inherently quantum in nature, the existence of a multiverse is unavoidable. Even though we cannot observe these other Universes, we can observe a huge amount of evidence for inflation, indirectly pointing to its inevitability. We can also observe a huge amount of evidence that the Universe itself is quantum, even though we have no proof that inflation itself behaves as a quantum field. If you put these pieces together, it unambiguously leads to the prediction that our Universe should be only one of countlessly many Universes, all embedded in an eternally inflating, expanding background. One Universe is not enough. Even though we cannot detect it, the prediction of a multiverse is unavoidable.”
When Carl Sagan’s Cosmos began, the first words you heard were, “The cosmos is all there is, or was, or will be.” Only… what if it weren’t? What if what we know as our cosmos, i.e., the entire Universe, were only one of countlessly many, all embedded in a strange spacetime that was continuously creating more of them? This sounds like some sort of strange speculation, but it’s actually an unavoidable consequence of two of our best theories put together: cosmic inflation and quantum physics. Combine them, and you get a multiverse.
This doesn’t mean the multiverse is the answer to all our problems; far from it. But it does mean that one Universe is not enough. Come find out why!
There Was No Big Bang Singularity
“Every time you see a diagram, an article, or a story talking about the “big bang singularity” or any sort of big bang/singularity existing before inflation, know that you’re dealing with an outdated method of thinking. The idea of a Big Bang singularity went out the window as soon as we realized we had a different state — that of cosmic inflation — preceding and setting up the early, hot-and-dense state of the Big Bang. There may have been a singularity at the very beginning of space and time, with inflation arising after that, but there’s no guarantee. In science, there are the things we can test, measure, predict, and confirm or refute, like an inflationary state giving rise to a hot Big Bang. Everything else? It’s nothing more than speculation.”
The Universe, as we observe it today, is expanding and cooling, with the overall density dropping as the volume of space increases. If we ran the clock backwards, however, instead of forwards, things would appear to contract, become denser, and grow hotter. If you go back farther and farther in time, you’d come to an epoch before there were stars and galaxies; before neutral atoms could stably form; before atomic nuclei could remain; etc. You’d go all the way back to hotter and denser states, eventually compressing all the matter and energy in the Universe into a single point: a singularity. This was the ultimate beginning of everything according to the original Big Bang: the birth of time and space.
But this picture is almost 40 years out of date, and known to be wrong. Why’s that? Come learn how we know that there was no Big Bang singularity.