Spacetime Singularities and the Origin of the Universe

singularity-greenThere’s been some fun down in the comments section, so I thought I’d bring a bit of it above the fold to make it easier to find and read.

Someone going by the ‘nym OnceAnAtheist objects to my claim that the universe has always existed. Unfortunately, this objection is based on a misunderstanding of spacetime singularities in general relativity.

(Of course, we know that general relativity can’t be the final story, because it doesn’t account for quantum effects; but it’s still a story worth considering. And it’s still the best story we’ve got a the moment.)

To recap, my point is that a spacetime singularity is (by standard definition) an incompleteness in that spacetime, such that some path cannot be extended indefinitely, but instead has some finite length. This is often thought of as an “edge” or a “tear” in spacetime.

What we’re interested in here are singular spacetimes that have paths with finite length in a temporal direction. Black holes are examples of regions of spacetime that have a limited amount of future time; if you fall into a black hole, you reach the temporal end of the universe very quickly. It’s geometrically impossible for the path you’re following to be any longer, so it just runs out. (And you run out with it.)

It’s the end of the universe (try the beef, you’ll find it quite friendly).

The initial big bang singularity is basically the same, except time runs out as you’re heading backwards in time rather than forward in time. You can run a clock backwards in time to 13.8 billion years ago, but you can’t go any further – because time just runs out. It’s the beginning of the universe, there’s to more time to go back into.

The important point here is that there is never a time when the universe doesn’t exist. Time and the universe (that is, the spacetime manifold of general relativity) go together. When the universe has an “edge” (a singularity), time does as well. Time never goes beyond the universe. It’s like asking what the shape of the green region below the point labeled “singularity” in the above diagram: there is no such region; all the green is above this point.

So this means that it makes no sense to speak of a “time before the big bang.” At absolutely every time, the universe exists. The universe is not infinitely old, but it also does not have a “beginning” in any ordinary sense. It never transitions from nonexistence to existence, because there was never a time that it didn’t exist.

So the universe has always existed.

Now, to answer OnceAnAtheist’s specific points:

1.”The universe has not always existed. It had a definite beginning. Background radiation and the increasing acceleration of the expansion of the universe prove this.

Big bang cosmology (expanding universe, background radiation, etc.) shows that the universe is not infinitely old, but rather has a finite age (of about 13.8 billion years). However, this is not the same thing as saying that it had “a definite beginning.”

To see this, consider a continuum that includes all points above zero cm. and below ten cm. This distance has a finite length (10 cm.), but there is no “definite beginning”: for any point, there will always be another between it and zero (which is not included in our interval).

But this is more a question of terminology than anything substantial. We can sensibly speak of the the first minutes or seconds of the universe, for example; so there is a beginning “period” if you like, even though there is no beginning point. The more important issues are the next ones:

2. “The question is, what caused the big bang? This certainly did not happen from nothing, by itself?”

It only makes sense to consider this possibility if there ever was nothing. But the whole point is that according to general relativity, there never was a time when there was nothing. At absolutely every actual time, the universe existed.

You seem to be assuming that 15 billion years ago there was “nothing” (except for gods, maybe). But, according to our best current science, that is just wrong. There’s no such thing as “15 billion years ago” in the actual history of the world.

It’s like assuming that there’s must be something north of the north pole (“After all, you just keep going north, there must be something there.”); it’s based on a conceptual confusion.

Given that there never was a time with “nothing” it’s a mistake to suppose that naturalists are saying that there was a transition from nothingness to the existence of the universe.

There never was such a transition, so asking for a cause of that transition is itself confused.

3. “When I say nothing, I mean literally nothing.

OK, but then you need to realize that such a nothing also means no time. So it makes no sense to suppose that the universe “came from” such a nothing, since “coming from” is an essentially temporal notion.

4. “So for them compare the ‘nothing’ before the big bang

Here again you’re using words in a way that just doesn’t work given general relativity. There is no “before the big bang.” You’re applying the concept of time to a context where time doesn’t exist.

You’re effectively saying, “At the time when there was no time . . . “

This is a contradiction. It is confused.

And there’s absolutely no reason why anyone who has a grasp of how modern physics deals with spatial and temporal properties would embrace an argument based on such a confusion.

If you actually want to confront these questions in an intellectually responsible way, you might want to look at Brian Pitts’ paper Why the Big Bang Singularity
Does Not Help the Kalam Cosmological Argument
“. (Can people without university affiliation bring up that pdf?)

5. Mathematicians have calculated the odds of this happening by chance and the answer was undeniably IMPOSSIBLE.

The fine-tuning argument is another topic, which I’ll address at some later date. For now, just a minor correction: anything that has a non-zero chance of occurring is (by definition) possible; so clearly the fine-tuning argument (even if successful) can’t show that a completely naturalistic universe is impossible.

5 responses to “Spacetime Singularities and the Origin of the Universe

  1. Someone going by the ‘nym OnceAnAtheist objects to my claim that the universe has always existed.

    Many people seem to have problems with that, and creationists are particularly vehement about it.

    If you argue “there is no smallest positive real number”, some folk will want to point to zero. But if you argue “there is no largest positive real number”, that is more readily accepted. I guess some people have problems conceiving of a singularity.

    Can people without university affiliation bring up that pdf?

    There’s no problem here, and there is nothing about my internet connection that would identify me as affiliated with a university. In particular, I do not have to use a campus proxy to access that pdf. I expect that other articles in that same journal would take me to a pay wall (unless I go through a campus proxy).

  2. “So the universe has always existed.”

    I think you know you’re just playing games with this statement. You might be trying to pawn it off as some kind of truth we all just cant grasp but anyone who has studied the history of this kind of thought would say you are just making incoherent claims.

    I think the whole problem with your line of reasoning is trying to use semantics to get rid of a nasty problem with your worldview. You cant use tricks to circumvent the facts. GR does lead to nothing.

    If the universe just came to be 1 second ago in a grand boltzman brain episode, and you were found to have all your past memories–even then you could never claim you always existed. There would be no way to form a logical statement claiming that –because there was no time before 1 second ago you have always existed.

    Take a second to think about it and forget the axe you have to grind to make some other point that is leading you to make this strange claim. If there is no way to logically claim this hypothetical boltzman brain universe always existed(even though you would have past memories) there is surely no way to attribute it to the real world. You are getting messed up because you are forcing the beginning to be observer independent. Sorry, but thats not the way language, logic, or science deals with truth. The universe has Not always existed.

    To be honest you sound like you’re using the same sophomoric philosophy as L Krauss. You have to understand that these topics have been touched on all throughout the history of thought by some of the greatest thinkers in history. This…”you dont understand physics” schtick –as if there is some secret knowledge we must attain to even grasp the awesomeness off your superior claims. Being such a person with higher math function I witnessed a lot of dweebs who could calculate but also couldn’t complete a coherent sentence. It is very clear to the well rounded higher functioning IQ’s in the world that there is steep price to pay, socially and in other areas of knowledge to the myopic almost autistic personalities of people like Krauss. Of course, he cant see how childish his reasoning is, but such is the nature of his dysfunction. Emulate him at the cost of embarrassing yourself.

    Face the topics honestly and accept the puzzle as it is. Honor the thinkers who have tackled these questions in the past. Dismiss them at your own peril.

    • Hi Michael, again wih the insults!

      Your Boltzmann Brain situation is a non sequitur. According to our best current physical theories, the universe has always existed (see OP). You could make up hypotheticals in which it hasn’t, obviously. So what?

  3. Pingback: The universe has always existed | Physicalism

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