Time has a beginning?

[Vorpal]

One of the earliest thoughts I recall having about Christianity that just made it seem a bit odd was that if, as I was told, God was eternal and had "always" been there, that meant he had already waited "forever" before creating us and this world! What was going on for an eternity before that?

Historical Christian note: St. Augustine's conclusion was that time and space were both created as part of the universe. This would have no particularly meaningful "before" that.

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

We had this discussion before. You never did define your criteria for for what causality means, and the very general "the physical state at some particular time is determined by the physical states at prior times" can be trivially satisfied even if time is not infinitely extensible into the past. There is no contradiction there at all, unless you have some other sort of causality in mind.

 

[Frankenstyle]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

Oh, I so didn't want to get into this.

You are basically correct here. Prior (although "prior" isn't exactly applicable) to the separation of time and space, the concept of cause and effect was irrelevant. Essentially all points in space and time occupied the same place. There is no answer to "What happened before time started", because there is no "before". We can't know, because the universe as it exists now, gives us no frame of reference from which we can ask that question.

The laws that govern the universe weren't in effect at that time, so we can't even get the syntax down for a "before" time situation, even on a purely mathematical level. Is not simply that we can't answer the question, we can't even effectively ask the question in any meaningful context. This should not be viewed as a shortcoming of science however, it's a "design flaw" of the universe that's to blame.

Unfortunately, some enthusiastic folks see this as a "knowledge gap", and they get carried away with what they believe to be a shortcoming of the scientific method, as they start tossing Gods, and aliens, and Unicorns into the gap as they try and make sense of it all.

What they don't understand, is that what they perceive as a knowledge gap, is also a magical fairy unicorn gap. But, that's the really cool thing about science...it doesn't require anyone to believe in it for it to work just fine.

 

[athon]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

Time is intimately related to how things work according to the laws we experience in today's universe. There is no particular property called 'time', as far as anybody can deduce. It seems to simply be a way of relating observations, akin to space.

In a singularity, all bets are off. The laws don't work in the same way. It'd make as much sense to speak of spatial coordinates in a singularity as it would to speak of how two events are related in time. That doesn't mean there is no 'causation' at all - it means we can't use the same laws to describe how events are related.

Space and time seem to be qualities we can't picture not existing. It's hard not picturing a universe expanding inside a larger void, just as it's hard not thinking of a seed of a universe waiting for inflation. Time and space aren't thought of as just being universal - they're superuniversal. Unfortunately, there is nothing indicating this to be true, and a whole lot indicating that space and time are laws that relate to a given state of the universe.

Is it mind-bending? Hell yeah - our brains function in an environment based on such laws. Yet counter-intuitive doesn't equal wrong. We're always needing to find clever ways of using the mush between our ears to overcome counter-intuitiveness in the face of logic.

Athon

 

[Perpetual Student]

Oh, I so didn't want to get into this.

Sorry! In my view this question about time having a beginning is the most fundamental and counter-intuitive aspect of the big bang theory. As a layman, I can accept that all other aspects of the big bang are a matter of the laws of physics and observational evidence.

You are basically correct here. Prior (although "prior" isn't exactly applicable) to the separation of time and space, the concept of cause and effect was irrelevant. Essentially all points in space and time occupied the same place. There is no answer to "What happened before time started", because there is no "before". We can't know, because the universe as it exists now, gives us no frame of reference from which we can ask that question.

Fair enough. So there could be no causality when the universe was in this state since "all points in space and time occupied the same place."

The laws that govern the universe weren't in effect at that time, so we can't even get the syntax down for a "before" time situation, even on a purely mathematical level. Is not simply that we can't answer the question, we can't even effectively ask the question in any meaningful context. This should not be viewed as a shortcoming of science however, it's a "design flaw" of the universe that's to blame.

Hence, no causality.

Unfortunately, some enthusiastic folks see this as a "knowledge gap", and they get carried away with what they believe to be a shortcoming of the scientific method, as they start tossing Gods, and aliens, and Unicorns into the gap as they try and make sense of it all.
What they don't understand, is that what they perceive as a knowledge gap, is also a magical fairy unicorn gap. But, that's the really cool thing about science...it doesn't require anyone to believe in it for it to work just fine.

That sort of thing is the furthest from my mind.
My thoughts on the matter of this question have to do with the big bang vs. other cosmological theories that incorporate an infinitely historical universe.

 

[I Ratant]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

.
Ask Aquinas... He went on and on about that.

 

[arthwollipot]

Here's an idea, and I'm sure someone will correct me if I'm totally off-base with this.

Okay. We know that time slows down in an intense gravitational field, like near a black hole. Surely it also slows down near the big bang singularity?

If we work backwards in time, from some hypothetical "external" viewpoint, as the universe gets smaller and smaller towards the big bang, time also gets slower and slower. As the universe approaches infinite density, time also approaches infinite slowness.

So can it really be said that there was a beginning to time at all?

 

[sol invictus]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

As Vorpal says we already went over this - and established that you're wrong. If causality means to you "for every moment there was an earlier moment", there's no problem. If causality means every event has a future and past cone of influence, there's no problem. If causality means you can impose a time-ordering, there's no problem.

So why do you say there can be no causality?

 

[MattusMaximus]

Okay. We know that time slows down in an intense gravitational field, like near a black hole. Surely it also slows down near the big bang singularity?

Correction: you must have two observers in two different frames of reference to notice this effect. Time deeper towards the black hole as measured by an observer further outside of the black hole is slowed down. The observer deeper inside the black hole observes their time flowing at a "normal" rate. This effect is called gravitational time dilation.

I'm also not too sure you can equate the two singularities either. A black hole singularity is due to a seemingly infinitely steep gravity well, out of which nothing (except for Hawking radiation) can escape. It was pretty clear that, for whatever reason, plenty of stuff (the known universe) "escaped" out of the big bang singularity, so I'm not sure they qualify as the same thing.

But your question is an interesting one - one which I have never considered before. Another problem with it is if the universe were all contained within the singularity, then how could there be any external frame of reference from which to make a measurement of time? Remember, in order to make such a comparison of time, there must be observers in two separate frames, one of them being the "external" frame. So, in that sense, it seems like a paradoxical question to me.

However, I would have to defer to someone here who is more of an expert than me on this particular point of big bang cosmology. Anyone?

If we work backwards in time, from some hypothetical "external" viewpoint, as the universe gets smaller and smaller towards the big bang, time also gets slower and slower. As the universe approaches infinite density, time also approaches infinite slowness.

So can it really be said that there was a beginning to time at all?

See my previous criticism. It's like asking "what does the universe expand into?" When understood within the full context of our knowledge of big bang cosmology, it becomes clear why such a question really has no meaning. At least, no meaning that I can surmise.

 

[Perpetual Student]

As Vorpal says we already went over this - and established that you're wrong.

Yes we did, but no such thing was "established."

If causality means to you "for every moment there was an earlier moment", there's no problem. If causality means every event has a future and past cone of influence, there's no problem. If causality means you can impose a time-ordering, there's no problem.

So why do you say there can be no causality?

Can you give me and example of causality without time?

 

[arthwollipot]

I'm also not too sure you can equate the two singularities either. A black hole singularity is due to a seemingly infinitely steep gravity well, out of which nothing (except for Hawking radiation) can escape. It was pretty clear that, for whatever reason, plenty of stuff (the known universe) "escaped" out of the big bang singularity, so I'm not sure they qualify as the same thing.

I see the event horizon of a black hole as analogous to the universal horizon. There is a point some 15 billion or so light years away where the apparent expansion of the universe is faster than light. That means that light cannot cross that horizon - just like the event horizon of a black hole.

But man, it takes a pretty bizarre twisting of thoughts in order to visualise the analogy. It would imply that the visible universe (which is for all intents and purposes a sphere centered upon our arbitrary observing position) is analogous to the area outside the event horizon of a black hole. For the analogy to be visualised, I basically have to turn the universe inside-out!

 

[Aitch]

But man, it takes a pretty bizarre twisting of thoughts in order to visualise the analogy. It would imply that the visible universe (which is for all intents and purposes a sphere centered upon our arbitrary observing position) is analogous to the area outside the event horizon of a black hole. For the analogy to be visualised, I basically have to turn the universe inside-out!

But if the universe is finite but unbounded, ie curves back on itself in however many dimensions are necessary, then there is no inside/outside. I think.

ETA: Unless you consider the bigger part to be the outside and the smaller the inside. Possibly.

 

[Tubbythin]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

I'd prefer to be confused by this than have the Universe ignoring the second (or first) law of thermodynamics.

 

[Vorpal]

A black hole singularity is due to a seemingly infinitely steep gravity well, out of which nothing (except for Hawking radiation) can escape.

Hawking radiation doesn't really do that, though--it's a horizon effect, rather than a singularity effect. But your overall point stands.

However, I would have to defer to someone here who is more of an expert than me on this particular point of big bang cosmology. Anyone?

I'm not an expert on cosmology of any sort, so I have a question of my own: inflation is frequently described as exponential, so if the universe is essentially de Sitter in the past, there shouldn't be the first place. So what gives with the quote in the OP? Doesn't inflation actually provide the only remotely reasonable "out" in regards to avoiding the past singularity? Also, what's the general acceptance of infinite-past inflation vs. non among cosmologists?

Can you give me and example of causality without time?

Perhaps we've a misunderstanding. No one disputed that causality requires time; what's disputed is that non-infinite time violates causality. That's the real issue--in terms of whether various cosmological models are actually contradictory (per OP) , this particular subthread (Tubbythin's comment), and regarding which of your past arguments were considered silly (again, per OP).

Of that, it's straightforward to give a concrete example. Let dS² be isometric to Euclidean 3-space. Then
[1] ds² = -dt² + t^4/3dS², 0 < t < inf
describes a homogeneous, expanding, spatially-flat universe in which there is a positive energy density proportional to 1/t² and vanishing pressure. As t→0⁺, there is a curvature singularity; that's frequently described as beginning of time, although properly speaking, it's not part of this manifold. However, there is nothing acausal about it. It satisfies all the energy conditions; nothing flows outside its lightcone; every instant has prior and subsequent instants; the state at every spacelike slice is determined by those prior to it.

 

[Skwinty]

Here is some more about the OP (From Inflation versus Cyclic Model thread)
I have read “The Endless Universe” as well as the papers below.
http://arxiv.org/abs/astro-ph/0404480v1
http://www.physics.princeton.edu/~steinh/cyclicFAQS/index.html
http://arxiv.org/PS_cache/hep-th/pdf/0408/0408083v1.pdf
http://arxiv.org/abs/astro-ph/0204479v1
The points I would like to raise are as follows.
1.I agree that earlier models of a cyclic universe had loads of problems as indicated by Tolman and others.
2.I agree that string and M-theory are still in their infancy and are not complete as yet, as far as a theory of everything.
3.However, the cyclic model as posited by Steinhardt and Turok seems to overcome or explain away the problems experienced by earlier models.
4.The cyclic model agrees with the predictions of the inflation model: these being near scale invariance of temperature (COBE), the flatness of space through numerous ground based experiments and WMAP, matter and dark matter distribution in CBMR (Adiabaticity) and the random noise characteristics of this distribution (Gaussianity). The jury is still out on the gravitational wave predictions, hopefully the Planck mission will produce the goods one way or the other.
5.The cyclic model does away with inflationary energy and replaces it with dark energy, it is parsimonious with no ad hoc additions and seems to be the only serious contender to inflation.

 

[Delvo]

There is a point some 15 billion or so light years away where the apparent expansion of the universe is faster than light.

No, there's no such point. The universe's expansion is not in distance per time such as X miles per second. It's in a fraction per time, like X% per year. Thus, the more original miles you start with, the greater the increase in miles is; it's cumulative. The multi-billion-light-year mark you're talking about is simply the distance that's long enough for the tiny percentage of increase per year, added up over all that huge distance, to equate to a total change of one light year. But there's no reason to think that what's happening out there would be any different from what's happening here and everywhere else: just a distance/length growth rate of a fifteenth of a billionth of any linear unit per year.

 

[Vorpal]

It's true that the expansion of the universe is described by inverse-time (i.e., a fraction per time), but since the expansion increases distances, the inverse-time parameter you describe also defines a sphere at which a comoving particle will recede at lightspeed. Specifically, it's just c/H, where H is the current Hubble parameter. That part isn't the problem.

Edit:

I see the event horizon of a black hole as analogous to the universal horizon. There is a point some 15 billion or so light years away where the apparent expansion of the universe is faster than light. That means that light cannot cross that horizon - just like the event horizon of a black hole.

Due to these quantities being dynamic, it's generally not the case that the Hubble distance (to objects receding at lightspeed) is the same as the cosmological horizon. It's quite possible in general to observe objects that are receding superluminally.

 

[Frankenstyle]

That sort of thing is the furthest from my mind.

Sorry, I didn't mean to seem to suggest that you specifically were "filling in the gaps with magic". That was more a case of me lamenting the fact that a lot of people tend to go there. What I was going for was more "Just because it seems counter intuitive, doesn't mean it's wrong".

 

[sol invictus]

Yes we did, but no such thing was "established."

All of the types of causality I mentioned in my post above were established. Let me ask again: if none of those are what you meant, what did you mean?

I'm not an expert on cosmology of any sort, so I have a question of my own: inflation is frequently described as exponential, so if the universe is essentially de Sitter in the past, there shouldn't be the first place. So what gives with the quote in the OP? Doesn't inflation actually provide the only remotely reasonable "out" in regards to avoiding the past singularity? Also, what's the general acceptance of infinite-past inflation vs. non among cosmologists?

I think most cosmologists believe that inflation cannot be past-eternal (i.e. there must be a singularity in the past), but I'll agree with that it's not obvious. What is clear is that inflation shields us from whatever (if anything) came before it, whether it was a singularity or something else. The reason is that it expands the universe to such an extent that we can now only see a tiny piece of it, and so we have very little information about what it looks like in total, or on larger scales. By the same token, any traces left behind by the singularity get inflated away - their density decreases to a tiny fraction of its initial value, making them very hard to detect.

 

[theprestige]

Without time, there can be no causality. So, if time had a beginning, how was the beginning caused?

Look, you're confusing time itself (whatever it actually is) with our understanding of time.

Our understanding of time is in the form of a complex mathematical model. It is internally consistent--all parts of the model agree with all other parts of the model. It is also a consistent explanation of various observations we have made about the world around us. And it is also succesful at accurately predicting phenomena that had not yet been observed when the predictions were made.

So it's a pretty good model. We use it for a lot of things. For a lot of things, it does a really good job. But it does have some flaws.

One of the most notable flaws is that if we run the model "backwards", we reach a point in the past where the mathematics become singular, and the solution to the mathematical formula becomes undefined.

This is not, as you seem to think, a flaw in time itself (whatever it actually is). It is merely a flaw in our understanding of time. All it means is that before this point, our model is incapable of describing what time might do. Whatever it is, you can be assured that it does something--we just don't know what.

To demand a solution to a mathematical singularity, and to complain that one is not forthcoming, is somewhat naive. The singularity is the part of the math for which there is no solution. For all the other parts of the math, we have very good solutions indeed.

 

[MattusMaximus]

But if the universe is finite but unbounded, ie curves back on itself in however many dimensions are necessary, then there is no inside/outside. I think.

ETA: Unless you consider the bigger part to be the outside and the smaller the inside. Possibly.

Be careful on that point, as it is often misunderstood. I assume you're speaking of the inflating-balloon analogy, right? If so, then take care to note that the universe in that analogy is the surface of the balloon, not the inside or outside of the balloon.