Our Universe wasn’t empty, even before the Big Bang | Hacker News Reader

Our Universe wasn’t empty, even before the Big Bang

bigthink.com

64 pointsBrajeshwar40 comments

There's a lot of confusion in this thread about "before the big bang". I was also confused and did some googling and found this explanation from a professor of theoretical physics. It seems that it's actually pretty normal to refer to the big bang as happening after the initial inflationary epoch, but others refer to it as the moment before this.

>Do not allow yourself to be confused: The Hot Big Bang almost certainly did not begin at the earliest moments of the universe. Some people refer to the Hot Big Bang as “The Big Bang”. Others refer to the Big Bang as including earlier times as well. This issue of terminology is discussed at the end of this article on Inflation [https://profmattstrassler.com/articles-and-posts/relativity-...].

The article is talking about the "hot big bang", so it's using terminology that is accepted by other theoretical physicists.

https://profmattstrassler.com/articles-and-posts/relativity-...

Wouldn’t this be the result of some theoretical physicists moving the goalposts?

It sounds like they feel the commonly accepted understanding of the Big Bang is overbroad. Fine. Find new words to describe the subsets of the event. Redefining the word is just causing confusion.

Most of the stuff I have read on this presupposes that some kind of phase transition(think of the early universe being in a 'boiling' phase and then condensating) occurred that caused the field which drove inflation(with the force carrier called the inflaton) to decay and release all the energy in the field(that is, the inflatons decayed). This decay process is what we conceive of as 'the big bang', as in the start of the energy dense Universe we see a glimpse of in the CMB.

You are right that the goalposts have been moved. When analysis of the CMB began, it was noticed that it was far too uniform in distribution and temperature for what was previously thought to be possible. It was at this point that an inflationary period was tacked on before 'the big bang' because that was the only way to get the kind of 'big bang' we seem to have had.

If the universe is cyclical, like has been proposed as a possible theory, then "before the Big Bang" is a perfectly reasonable phrase. Sir Roger Penrose has helped bring attention to the idea, and more recently suggested it may be incorect. It's been around for a while (proposed in the 70's maybe, I think?). --- I'm disappointed by the ease at which people seem to dismiss the phrase as unreasonable. Is it being overly critical without actually knowing enough detail in the field? --- Normally I see very thoughtful responses, so I wonder if there's some collective exhaustion going on. Maybe give a think to some down-time or self-care today? I recommend a light ale or blonde lager with lunch. :)

This article doesn't make any sense. Skimming over it, I don't see that it's even about "before the Big Bang," which is a nonsense phrase. Nor do I see why it's arguing the point that our universe has even been empty, because nobody has ever argued that it was.

Ah, it's talking about the future, when it might be "empty", and explaining to the reader how it won't actually be empty. That's weird.

Ah, it's now circling back to "cosmic inflation... Before the hot Big Bang occurred." What? That is one of the most wrong things I've ever heard about the early universe.

The big bang has two meanings in common usage. Some people think it means "the beginning of time". But it can also refer to the time immediately after inflation. [1]

[1] https://profmattstrassler.com/articles-and-posts/relativity-...

Whoops. I've never heard of the "Hot Big Bang" as a period that began after inflation. Thanks.

Some physicists disagree with Hawking.

The assertions in the article don’t seem to make a strong case for talking about “before”, but that doesn’t make Hawking definitely right either.

>Even in the distant past, during the period of cosmic inflation that occurred before the Big Bang, that background radiation was present

What does "before the Big Bang" mean? Don't space and time break down at the Big Bang singularity? Didn't cosmic inflation happen 10^-36 seconds after the Big Bang?

Yeah, it's hard to understand what that means because the furthest point back in time that we know of could be looked at as the beginning of the big bang, even if there was a delay of some kind before the most significant expansion.

I really don’t think it’s hard and basically everyone knows what is meant by this. Physicists just like to be pedantic about the technicalities of what “before” means.

If we're talking about a singularity, it's not pedantic. If you reverse time and go back to the Big Bang, it's not possible to define what happens after you hit the singularity, at least according to current theories.

As another commenter pointed out, the article is referring to the "hot Big Bang era", not the Big Bang singularity, so that's what is causing the confusion. It is possible to talk about what happened during and after cosmic inflation.

Ex-physicist, which kind of muddies the water, but I'm not trying to be pedantic when I say "I don't know what this means".

Totally off-topic, but what made you leave the physics field? If you don't mind me asking.

I think they think the big bang means the moment the cosmic microwave background was created, and are confusing the big bang with recombination (which made the universe transparent). Why else would they suggest that inflation happened before the big bang?

The title is terrible and doesn’t refer to the actually interesting key point in the article!

The idea trying to be expressed is actually that the expansion of the universe is releasing energy, making the concept of “empty” space impossible as even the emptiest areas are still emitting energy.

Well, we knew that to be true already because of quantum foam, and the Higgs field having a nonzero rest energy.

Lots of complaints here about how "before" somehow "crosses a line" and this isn't science any more. I guess I think it's more gradient than that. We're mad because this is "before", but just the other day, we had headlines indicating that ... may be ... the universe is 2x older than what I've been told for years. At this point, I'm totally with Nate Bargatze on this stuff:

https://youtu.be/lkCvP4jttHI

The age of the universe seems to me to be completely irrelevant to the existence of time "prior" to the beginning of time. It's like asking what is "outside" an infinite universe.

Or a bounded but finite one with a topology that folds back in on itself. What confuses me is when physicists talk of spacetime (maybe) emerging from something more fundamental

Sure.

> What confuses me is when physicists talk of spacetime (maybe) emerging from something more fundamental

I also find this difficult to grok. But how is this relevant?

Reading about Big Bang, I'm wondering about this: doesn't the fact that the Big Bang happened imply that there was some kind of state-change: from Big Bang is not happening to Big Bang is happening, and any kind of state-change requires the existence of time. Doesn't this imply that time existed before the Big Bang?

Assuming you mean "Big Bang" in the sense of the beginning of the universe, not necessarily.

>doesn't the fact that the Big Bang happened imply that there was some kind of state-change: from Big Bang is not happening to Big Bang is happening

Language is incredibly bad at describing this because we did not develop it when such a concept as "outside of time" existed. The word "happened" is misleading you I think. If we define "something that happened" as an event with a before and after then the Big Bang did not, by that definition, "happen".

I've had it explained to me that asking "What happened before the big bang?" is akin to asking "What's north of the north pole?"

Short answer, no what we at least think of time and the other fundamental rules of physics didn't have to exist, or may have been different values from our universe now.

https://en.m.wikipedia.org/wiki/False_vacuum_decay

What is this article championing? An infinite universe? I thought that was already discarded, it certainly should be since it isn't logical. But aside from that, doesn't the theory put forward by this article violate the Second Law of Thermodynamics? It's just shifting the "nothing->something" equation from The Big Bang to "oh you know, whenever. a little bit now and again adds up you know". And seems to be doing it by saying that "Well see, the universe will never truly be empty, so before the Big Bang is wasn't empty either". Without ever really explaining how this isn't just kicking the can backwards down the road.

This makes sense if we don’t consider the Big Bang as the “creation” of our universe but rather just another event that happens in it.

Thermodynamic laws and how our universe is expanding are both fairly well understood. Is it too much of a stretch to think that our universe has gone through many expansion and contraction cycles?

It expands until heat death, then black holes take over. These black holes slowly swallow all matter and then finally merge with other black holes. Over an unthinkable amount of time I’d imagine all those black holes become one, bringing about the concentration of mass necessary for another big bang.

Problem with this is that blackholes will eventually evaporate due to radiating Hawking radiation. That and expansion is (probably) speeding. Evidence is against gravity slowing that down.

Roger Penrose has a cyclic theory that allows what you state. The universe stretches itself out so far over so much time it becomes effectively zero entropy, which it kind of how the big bang appears to be.

The Higgs field is and was a thing, right? In that sense, the universe has never been empty, but only in the sense of the scale and diversity of matter.

before

you keep using that word

i do not think it means what you think it means

Anything thing that talks about "Before the Big Bang" isn't science. It may be philosophy or mathematical speculation, but it is not science.

There is as yet insufficient data for a meaningful article.

Ok?

Not everything in the world has to be science. Some things are not science. It’s fine.

This article is explicitly claiming to be science.

"Anything that talks about 'the world is round' isn't science. It may be astrology or mathematical speculation but it is not science."

One can do experiments to empirically test the earth is round.

There are no experiments one can do to empirically test things asserted before the Big Bang.

While I agree with the sentiment here, Penrose has come up with a model that does make testable hypotheses about what happened before the big bang with his Conformal Cyclic Cosmology. Now, I think that as a matter of fact, the predictions he made have turned out to not be true, but at least he came up with a way to test them. If I recall correctly, the predictions had to do with patterns in the CMB that would have been left over from black holes in a universe before the big bang, and those patterns ended up not being there. It wasn't the right answer, but that's science.

"Dont hypothesize over anything that cannot be immediatly tested otherwise it isnt science" -rcouf1z4gsc

Yeah testable hypothesis are what separate science from other disciplines. If you don’t have a testable hypothesis, you don’t have science

It's sad to see this kind of pop-sci garbage. This isn't science, it isn't even philosophy. It's pure speculation.

And hey, speculation is fine - but as soon this kind of speculation is phrased in an authoritative "this is how it is" kind of way, it becomes absolute garbage IMO.

It's even worse when it comes from an actual scientist.

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