What Caused the Singularity & Is There Anything Before the Universe?

[Astralos]

Stephen Hawking gave me a clear timeline of the universe, from the expansion of the singularity to its current (and still expanding) state. I understand that the singularity was one point of infinite density (correct me if I'm wrong). My question is, what had happened before the singularity? Better yet, what caused the singularity? What is the singularity? What is the real reason why there is a universe instead of nothing?

 

[phinds]

Stephen Hawking gave me a clear timeline of the universe, from the expansion of the singularity to its current (and still expanding) state. I understand that the singularity was one point of infinite density (correct me if I'm wrong). My question is, what had happened before the singularity? Better yet, what caused the singularity? What is the singularity? What is the real reason why there is a universe instead of nothing?

Basically, there is nothing that modern science can determine about the singularity. Physics totally breaks down at t=0 and "before the universe" is a theological discussion, not a scientific one, because no matter WHAT you say it is not subject to falsification.

One of the things I've heard that I very much like, to describe the singularity is that the singularity is a point where physics gets answers that are infinite and that is a clear sign, NOT that the answer is infinity but that the model has broken down at that point and needs refinement before you can say anything meaningful.

Science is really getting very good at describing things from the Plank time forward, but before that all bets are off.

 

[bapowell]

The mathematical singularity that marks the beginning of time is not considered to be of physical significance -- it indicates instead that our theories are not applicable here. I don't agree that "pre-big bang" physics is fundamentally outside the epistemological purview of science -- why should it be? Consider a bouncing universe, in which what we perceive to be a Big Bang event is really the bounce from a contracting phase to an expanding phase. There are such models, and such models do make predictions. As such, these models can be tested using modern cosmological observations. That's science.

 

[phinds]

There are such models, and such models do make predictions. As such, these models can be tested using modern cosmological observations. That's science.

I was not aware that any of those models made falseibiable predictions. I stand corrected.

 

[George Jones]

A few months ago, there was a BBC Horizon program titled "What Happened Before the Big Bang". This is on YouTube in six parts.

All the ideas (some of which might be mutually exclusive) in this Horizon are highly speculative, and maybe this thread is the wrong forum (Should be in the Beyond the standard Model Forum?). Before we can determine which of the ideas in this program are correct, we probably need a quantum theory of gravity with which we can calculate and make predictions. In my opinion, this could take anywhere from 5 to 500 years or more.

The building featured in this Horizon is the Perimeter Institute in Waterloo, and is a couple of kilometres from my brother's house.

 

[marcus]

The mathematical singularity that marks the beginning of time is not considered to be of physical significance -- it indicates instead that our theories are not applicable here. I don't agree that "pre-big bang" physics is fundamentally outside the epistemological purview of science -- why should it be? Consider a bouncing universe, in which what we perceive to be a Big Bang event is really the bounce from a contracting phase to an expanding phase. There are such models, and such models do make predictions. As such, these models can be tested using modern cosmological observations. That's science.

For people not already familiar, here's a link to some papers that have appeared since 2009 and are concerned with testing one of the bounce models.

http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28PRIMORDIAL%2C+FLUCTUATION+OR+INFLATION+OR+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29

I agree with Brian Powell. It's true that many of the ideas that have been proposed are merely speculative (not definite models on which testable predictions can be based). But in at least one case there is a definite quantum cosmology model which (not only the theorists themselves, but) early-universe phenomenologists are now beginning to examine with a view to testing. One of the papers delivered at the Madrid conference last week was titled "How to falsify loop quantum cosmology." (Ambitious title )

 

[phinds]

Very cool. Thanks Marcus and George for this information.

 

[marcus]

Hi All,
There is a careful distinction to be made, which could even be instructive to point out.

There is the research area of early universe phenomenology.
Phenomenologists are professional theory-testers. They are normally not committed to anyone particular model. They play the field, so to speak. Think of ways to test whatever well-defined model gets their interest. Just as happy whether it passes or fails. That is their job.

There are some highly (even notoriously I would say) speculative pre-bang scenarios that are floating around. They have imaginative and entertainment value, and maybe eventually will develop into testable versions that the E.U. phenom'ists take on.

There is also the Loop QC model which, for better or for worse, has already gotten phenom'ists attention. So that model has, so to speak, crossed the line. It quite possibly could be falsified (if the predicted imprints of a bounce are not seen in CMB polarization.)

From what I've read I suspect this is being used to motivate and push for the design/funding of a space mission to do CMB polarization mapping (analogous to the temperature mapping already in progress). That is, the phenom'ists have a practical motive, besides disinterested science. They are, in effect, making a case for a mission like the proposed "CMB-pol".

Anyway the model has crossed the line, and can be considered part of real cosmology. Currently that link gets 33 phenom. papers, substantial in other words. It's an interesting development to check out.
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28PRIMORDIAL%2C+FLUCTUATION+OR+INFLATION+OR+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29

I have also seen indications that some other models may be getting to the stage of entering the phenomenology arena. But I don't want to count a mere one or two papers. Wait and see, on that.

 

[Cosmo Novice]

One of the things I've heard that I very much like, to describe the singularity is that the singularity is a point where physics gets answers that are infinite and that is a clear sign, NOT that the answer is infinity but that the model has broken down at that point and needs refinement before you can say anything meaningful.

Yes but on the other hand, maybe it is infinite and we just don't understand it yet, or maybe we will never understand it.

Are you refuting infinities?

 

[Astralos]

As far as I know however, there doesn't need to be anything before the Big Bang, because time itself was not present, and as such, nothing would require a beginning or an end--both qualities that are attributed to our fourth dimension.

 

[marcus]

... because time itself was not present,...

?

It has not been demonstrated that time was not present.
All we know is that a certain model breaks down as you go back in time.
And other models do not. So those go back before and, with them, ordinary time extends back before.

Now it's up to the observational people to test which is right. We *don't know* yet whether time extends back before, or not.

You might want to read an essay about this put up by a German research outfit, the Albert Einstein Institute (a branch of Max Planck Institute).

The essay is called A Tale of Two Big Bangs. It's for wide audience, non-technical, at their outreach website:
http://www.einstein-online.info/spotlights/big_bangs

It helps to clarify some of the confusion about this.

They've got a bunch of other stuff on their public outreach site as well:
http://www.einstein-online.info/spotlights/cosmology/?set_language=en
===================

If you are more versed, have a look at some of these papers:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE%29+AND+%28PRIMORDIAL%2C+FLUCTUATION+OR+INFLATION+OR+COSMIC+BACKGROUND+RADIATION%29+AND+DATE+%3E+2008&FORMAT=www&SEQUENCE=citecount%28d%29

They are all about ways to observationally test models where time extends on back before where vintage 1915 Gen Rel breaks down and develops a "singularity" (jargon for mathematical failure).

Some of the popularization in the media (as you probably are well aware) is out of date or oversimplified to the point of being misleading.

I would agree that it will probably be very hard to ultimately resolve these issues but the point is that they so far are unresolved, and part of the job goes to the observationalists.
If, say, Loop QC is ruled out by observations in the next 10 years, there will still almost certainly be other cosmology models proposed that eliminate the singularity and run back in time.

 

[twofish-quant]

Basically, there is nothing that modern science can determine about the singularity. Physics totally breaks down at t=0 and "before the universe" is a theological discussion, not a scientific one, because no matter WHAT you say it is not subject to falsification.

Our current models break down at t=0. Our current theories also break down in a lot of other places. There are people that are trying to come up with new models.

Science is really getting very good at describing things from the Planck time forward, but before that all bets are off.

People are making guesses.

Let me add about a big misconception about what theorists do. People assume that theorists just sit around and try to figure out the universe from pure thought. The idea is that if you are super-smart, you can go into a room and figure out how the universe works.

That's not what happens.

Theorists are people that ask "what-if". Let's *assume* that the universe before the big bang was like such and such. At that point, you think a lot, and figure out that *if* things were this way, then you ought to see such and such. They you ask the observers if they see such and such. If they don't then, you cross one idea off the list.

This is one of the big differences between science and religion (not to say that religion is bad, but it's different). If you are a Catholic priest that doesn't believe in Catholic dogma, you aren't going to be a good Catholic priest. On the other hand, one thing that you have to learn as a theorist is not to fall in love with your ideas, since much of your job is coming up with ideas that later turn out to be totally wrong.

It takes a ton of work to come up with a wrong idea. Also physicists get excited when it turns out that a basic idea is wrong. I remember in 1995, when COBE came out with the first results, and there was a bit of disappointment that because the results were pretty much exactly what CDM said they would be. Then in 1998, people showed that the universe was accelerating and all the theorists went nuts because there was now a mystery to be explained.

 

[twofish-quant]

If, say, Loop QC is ruled out by observations in the next 10 years, there will still almost certainly be other cosmology models proposed that eliminate the singularity and run back in time.

Also the reason that people are excited about LQC is that there is a very good chance that in 10 years we can rule it out. If we can show that LQC is *wrong*, that's progress.

One of the big problems with string theory is that it's been around for 20 years, and they haven't coming up with a smoking gun observation that can *disprove* string theory.

 

[Chalnoth]

Stephen Hawking gave me a clear timeline of the universe, from the expansion of the singularity to its current (and still expanding) state. I understand that the singularity was one point of infinite density (correct me if I'm wrong). My question is, what had happened before the singularity? Better yet, what caused the singularity? What is the singularity?

There was never a singularity. A singularity is mathematical nonsense and cannot possibly exist in reality. It can be thought of as merely a placeholder for stuff that our current theories are insufficient to predict.

What is the real reason why there is a universe instead of nothing?

Well, nobody knows exactly, but quantum mechanics provides a significant hint. Within quantum mechanics, if you write down a theory where some particles can exist, then quantum mechanics says that these particles must exist: they pop in and out of the vacuum in any theory where they can possibly exist.

If, with quantum gravity, this aspect is retained, then it may potentially be the case that if regions of space-time can exist, then it is conceivable that they must exist in a similar manner. Now, we don't know the correct theory of quantum gravity yet, but because of the way quantum mechanics works, it seems pretty likely that this sort of thing probably has to be the case.

 

[Astralos]

There was never a singularity. A singularity is mathematical nonsense and cannot possibly exist in reality. It can be thought of as merely a placeholder for stuff that our current theories are insufficient to predict.


Well, nobody knows exactly, but quantum mechanics provides a significant hint. Within quantum mechanics, if you write down a theory where some particles can exist, then quantum mechanics says that these particles must exist: they pop in and out of the vacuum in any theory where they can possibly exist.

If, with quantum gravity, this aspect is retained, then it may potentially be the case that if regions of space-time can exist, then it is conceivable that they must exist in a similar manner. Now, we don't know the correct theory of quantum gravity yet, but because of the way quantum mechanics works, it seems pretty likely that this sort of thing probably has to be the case.

Exactly what I was looking for. Thank you everyone so much.

 

[Cosmo Novice]

There was never a singularity. A singularity is mathematical nonsense and cannot possibly exist in reality. It can be thought of as merely a placeholder for stuff that our current theories are insufficient to predict.

How do we know that in truth the singularity did not exist? because we cannot understand it?

I am in no way criticising just looking for more of an explanation.

If out current laws of physics are determined by GR, which wasnt always applicable (I think this is where quantum theory gravity unification is required in the early stages of U), then how can we expect the singularity to make mathemtical sense utilising physical laws that didnt yet exist?

Im completely boggled and just looking for more information.

Thankyou

 

[phinds]

How do we know that in truth the singularity did not exist? because we cannot understand it?

Personally, I thing that the description " ... merely a placeholder for stuff that our current theories are insufficient to predict" is EXACTLY what the term "singularity" means, so saying that it doesn't exist is just semantics. SOMETHING happened and we call that the singularity.

 

[marcus]

How do we know that in truth the singularity did not exist?

I agree with Chalnoth and PHinds. Your question does not make sense. You ask "how do we know the singularity in GR does not exist?"
But in fact, as everybody knows, the singularity in GR DOES exist.

It exists in the only way a singularity (properly understood) can exist, within the context of a man-made mathematical model.

And this is one of the reasons that so many people are now working on improving/replacing the model.

There have been singularities in other theories, in past history, in other branches of physics. Always it is seen as a sign of something wrong with the theory and people have gotten rid of the sing'ty by improving the theory.

Please, we need to talk using words that mean something. Not just pop-sci fantasy or something you see on some Cable Media. Please read "A Tale of Two Big Bangs" which tries to combat some of the confusion in popular language. The link is in my sig. If you can't find it, ask.

The rigorous meaning of "singularity" is a breakdown in a man-made theoretical model. So the tempoary "placeholder" idea is a good one. It is a well-defined something in a man-made theory. We do not project it on to Nature.

The "Einstein-Online" essay will explain to you that a singularity is a SYMPTOM of something wrong with the theory in which the singularity appears. The scientists involved would be surprised if Nature actually suffered from the breakdown experienced in GR. The symptom merely indicates that GR has limits of applicability. Every theory has some domain of applicability and other places where it does not apply. This is normal.

 

[Chalnoth]

How do we know that in truth the singularity did not exist? because we cannot understand it?

Because it's mathematical nonsense: if you allow a singularity in your theories, you can basically prove anything you want. The way we fix this is we sort of "hide" the singularities so that the rest of the theory remains well-behaved. In this situation, we just say, "Okay, before a certain time, our current theories can no longer tell us what was going on." By doing this, we can prevent the nastiness of the singularity (which is basically a division by zero) from completely destroying the predictive power of the theory.

If out current laws of physics are determined by GR, which wasnt always applicable (I think this is where quantum theory gravity unification is required in the early stages of U), then how can we expect the singularity to make mathemtical sense utilising physical laws that didnt yet exist?

Well, I think the point here is that we expect the real world to make sense. We may not know perfectly the laws that describe the real world as yet, but whatever laws do describe the real world must make sense in the same way.

 

[Cosmo Novice]

So the singularity is not an actual state or environment of the U, just the point in space/time where our theories (which currently hold true) no longer make sense. Complete breakdown of any current applicable model.

Thanks a lot, I was almost trying to imagine a singularity as an actual state of existence when essentially we are saying that t=0 with current physics understanding is a singularity where all known physical sciences become irrelevant.

Thanks very much for the help. Apologies for the pop sci fi language, much of my interest is derived from being a fan of sci-fi books, although I do prefer the hard sci fi of asimov and clarke a little more than the modern softer stuff!

Thanks again for your responses

 

[DavidMcC]

?

If, say, Loop QC is ruled out by observations in the next 10 years, there will still almost certainly be other cosmology models proposed that eliminate the singularity and run back in time.

I still haven't found out by how much the "singularity is avoided in the so-called "big bounce". Does it have to become a black hole during the bounce, or not? I predict that it would, for what I hope by now are obvious reasons.

 

[DavidMcC]

Also the reason that people are excited about LQC is that there is a very good chance that in 10 years we can rule it out. If we can show that LQC is *wrong*, that's progress.

Actually there are various versions of LQC. The most popular one seems to be Ashtekar's, that predicts the "big bounce", which already seems doomed, as the universe does not seem to be heading for a big crunch anytime soon, quite the contrary. However, small bits of it have and will crunch - they're called black holes.

 

[marcus]

I still haven't found out by how much the "singularity is avoided in the so-called "big bounce". Does it have to become a black hole during the bounce, or not? I predict that it would, for what I hope by now are obvious reasons.

?

In the case of black hole models e.g. Schwarzschild, there is space outside the BH and a horizon which persists in time. The contraction of the entire universe (nothing outside) is a radically different picture. Not like a BH.

A better analogy (though not precise) to the contracting phase would probably be the "big crunch" that we used to hear about before 1998 as one of the possible ways the U could end.

We don't know that the way Loop quantum version of GR and the resulting quantum version of Friedmann model (FRW) cosmology are right---ways to test the latter are being explored---but according to it gravity becomes repellent at uniformly high densities (beginning roughly around one percent Planck) due to quantum corrections, which then become important. This would naturally tend to dissipate any condensed structures including any black holes that happen to be present in the collapsing classical phase.

I would urge that you read a direct primary source on Loop cosmology and not rely on any secondhand interpretation, such as mine. A good recent one would be Ashtekar "The Big Bang and the Quantum" a short 2010 review written for cosmologists.

Anyway the answer to your question AFAICS would be "no". The entire collapsing phase prior to bounce could not form a black hole. I have a hard time picturing that, since it is the entire universive with nothing outside it. And moreover at bounce time any black holes would be dissipating together with other types of inhomogeneity.

Please check by consulting a recent primary source.

 

[marcus]

... The most popular one seems to be Ashtekar's, that predicts the "big bounce", which already seems doomed, as the universe does not seem to be heading for a big crunch anytime soon,...

You are mistaken. Ashtekar's Loop cosmo does not predict a future big bounce. It is hardly "doomed" by such a comment.

The research effort now is focused on fitting the bounce cosmology to data, like the 7-year WMAP.
You should read about it. It's quite interesting.

However, small bits of it have and will crunch - they're called black holes.

David, your tone in responding to twofish quant seemed oddly condescending. He made a good point, which you seemed to dismiss in a rather airy fashion. If you don't WANT to understand, there is not much we can do to help you.

If you do, you may find these links helpful. I'm not suggesting stuff to study. In some cases, if you haven't already, you might want to simply glance at the abstract to get a sense of the kind of work currently being done. The first, if you haven't already looked at it, might be worth taking a longer look at---it's a survey aimed at wider audience.
http://arxiv.org/abs/1005.5491
The Big Bang and the Quantum
http://arxiv.org/abs/1103.2475
Probability of Inflation in Loop Quantum Cosmology
http://arxiv.org/abs/1011.1811
Observing the Big Bounce with Tensor Modes in the Cosmic Microwave Background: Phenomenology and Fundamental LQC Parameters
http://arxiv.org/abs/1003.4660
Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves
http://arxiv.org/abs/0902.0145
Cosmological footprints of loop quantum gravity

The first gives an overview (you may have looked at it already?). The others are technical and included just as a way to glance over and sample the current work on fitting model to observational data, checking compatibility with inflation, and eventually testing.

 

[bcrowell]

It's popular among physicists to say that singularities in GR are not physical singularities, and they just indicate a place where the theory breaks down and needs to be replaced with some more general theory. These are really three separate statements:

(1) Singularities in GR are not physical singularities.
(2) Singularities indicate a place where GR breaks down.
(3) When the theory breaks down at a singularity, it needs to be replaced with some more general theory that won't break down at the singularity.

The most popular point of view, then, seems to be that 1 is true, 2 is true, and 3 is true.

Personally, what pleases my aesthetic sense the most is the idea that 1 is false, 2 is true, and 3 is only partially true. Here's the scenario: Singularities in GR are indeed physical singularities. At a singularity, GR breaks down, in the sense that you can't pose a Cauchy problem there and get a uniquely defined prediction. In addition, every theory breaks down at the singularity, because the singularity is physical, not a mathematical artifact. That is, in this scenario, even if we could find a theory of quantum gravity and verify it by observations, that theory would still turn out to break down at the singularity. When a theory breaks down at a singularity, we can hope to find a new theory that can describe what happens closer to the singularity, but in this scenario the new theory will still not get to the singularity.

Note that although the paragraph above is all written in affirmative sentences, I'm not saying that I can prove that it's true. I'm just saying this is the scenario that appeals to me the most. One thing that appeals to me about it is that it gives a very clean separation between the things that science can explain and the things that it can't explain. This scenario can be disproved (if we get a theory that doesn't break down at singularities, makes predictions, and passes empirical tests of those predictions). It can't be proved (because it makes statements about all possible theories).

What seems to me most unappealing about the prevalent view (1, 2, and 3 all true) is that it posits the existence of something that is knowable in principle (a theory that extends physics back to the Big Bang singularity), but that in practice I am convinced human minds will never know (because I suspect that there is no technology that could ever provide empirical tests of a theory of quantum gravity, even thousands of years in the future). The reason I find this so unappealing is that it smells like theism, in the sense that hypothetical intelligent beings can know things that humans can never know.

-Ben

 

[Shenstar]

What evidence currently suggests that there was a big bang from a singularity. Why can't the steady state universe be adapted slightly to take away the singularity. Maybe have a bing bang to cause expansion, but not from a singularity.

Also, I have a question about singularities. Is it equal to nothing, meaning zero mass zero time or is it infinite mass And infinite time? Stephen hawking is quoted as saying universe came from nothing.

 

[Ryan_m_b]

What evidence currently suggests that there was a big bang from a singularity. Why can't the steady state universe be adapted slightly to take away the singularity. Maybe have a bing bang to cause expansion, but not from a singularity.

Also, I have a question about singularities. Is it equal to nothing, meaning zero mass zero time or is it infinite mass And infinite time? Stephen hawking is quoted as saying universe came from nothing.

We cannot simply modify existing understanding, current evidence points to a singularity. Where is Stephen Hawking quoted as saying that? I would propose that such a quote is most likely taken out of the context it was given in.

A singularity is not infinite mass but infinite density (as a singularity has finite mass but zero volume).

 

[Shenstar]

The quote I read from hiS wiKIpediA page and I heard hiM say it on Hawking universe documentary. Maybe zero volume infinite density he would describe as nothing? Many theorists used to say time before the universe could not exists and the question itself was incorrect by definition, as everything including time only existed after the big bang. So maybe this 'nothing' idea comes from that

 

[Ryan_m_b]

The quote I read from hiS wiKIpediA page and I heard hiM say it on Hawking universe documentary. Maybe zero volume infinite density he would describe as nothing? Many theorists used to say time before the universe could not exists and the question itself was incorrect by definition, as everything including time only existed after the big bang. So maybe this 'nothing' idea comes from that

How could an object with infinite density that exerts a gravitational pull be defined as nothing

I agree that it is probably in answer to the question "before" to which he may have replied "nothing" to mean "there was nothing 'before' because 'before time' makes no sense" rather than implying that before the big bang there was a void.

 

[bcrowell]

What evidence currently suggests that there was a big bang from a singularity. Why can't the steady state universe be adapted slightly to take away the singularity. Maybe have a bing bang to cause expansion, but not from a singularity.

http://en.wikipedia.org/wiki/Penrose–Hawking_singularity_theorems

Also, I have a question about singularities. Is it equal to nothing, meaning zero mass zero time or is it infinite mass And infinite time? Stephen hawking is quoted as saying universe came from nothing.

You might want to take a look at the following two entries in the FAQ at the top of the cosmology forum.

FAQ: How does conservation of energy work in general relativity, and how does this apply to cosmology? What is the total mass-energy of the universe?

FAQ: Is the universe finite, or is it infinite?

The quote I read from hiS wiKIpediA page and I heard hiM say it on Hawking universe documentary. Maybe zero volume infinite density he would describe as nothing? Many theorists used to say time before the universe could not exists and the question itself was incorrect by definition, as everything including time only existed after the big bang. So maybe this 'nothing' idea comes from that

It's hard to have much of a discussion based on a second-hand description of what an authority might have said on TV. There really isn't any substitute for the written word.

 

[Cosmo Novice]

It's popular among physicists to say that singularities in GR are not physical singularities, and they just indicate a place where the theory breaks down and needs to be replaced with some more general theory. These are really three separate statements:

(1) Singularities in GR are not physical singularities.
(2) Singularities indicate a place where GR breaks down.
(3) When the theory breaks down at a singularity, it needs to be replaced with some more general theory that won't break down at the singularity.

The most popular point of view, then, seems to be that 1 is true, 2 is true, and 3 is true.

Personally, what pleases my aesthetic sense the most is the idea that 1 is false, 2 is true, and 3 is only partially true. Here's the scenario: Singularities in GR are indeed physical singularities. At a singularity, GR breaks down, in the sense that you can't pose a Cauchy problem there and get a uniquely defined prediction. In addition, every theory breaks down at the singularity, because the singularity is physical, not a mathematical artifact. That is, in this scenario, even if we could find a theory of quantum gravity and verify it by observations, that theory would still turn out to break down at the singularity. When a theory breaks down at a singularity, we can hope to find a new theory that can describe what happens closer to the singularity, but in this scenario the new theory will still not get to the singularity.

Note that although the paragraph above is all written in affirmative sentences, I'm not saying that I can prove that it's true. I'm just saying this is the scenario that appeals to me the most. One thing that appeals to me about it is that it gives a very clean separation between the things that science can explain and the things that it can't explain. This scenario can be disproved (if we get a theory that doesn't break down at singularities, makes predictions, and passes empirical tests of those predictions). It can't be proved (because it makes statements about all possible theories).

What seems to me most unappealing about the prevalent view (1, 2, and 3 all true) is that it posits the existence of something that is knowable in principle (a theory that extends physics back to the Big Bang singularity), but that in practice I am convinced human minds will never know (because I suspect that there is no technology that could ever provide empirical tests of a theory of quantum gravity, even thousands of years in the future). The reason I find this so unappealing is that it smells like theism, in the sense that hypothetical intelligent beings can know things that humans can never know.

-Ben

Thankyou very much,

This is essentially what I have been thinking and one of the main reasons I have been questioning the "singularity acts as a placeholder" comments; I feel this view assumes eventual understanding and fails to take into account the possibility that their may be no way to understand a singularity mathematically - if the singularity was physical.

I am in no way stating this is the case, I am no mathemetician or physicist, I just think it may be a possibility. Wouldn't Occams Razor suggest it is physical?

Obvisously this is all speculative but I find it very interesting

 

[phinds]

Thankyou very much,

This is essentially what I have been thinking and one of the main reasons I have been questioning the "singularity acts as a placeholder" comments; I feel this view assumes eventual understanding and fails to take into account the possibility that their may be no way to understand a singularity mathematically - if the singularity was physical.

I am in no way stating this is the case, I am no mathemetician or physicist, I just think it may be a possibility. Wouldn't Occams Razor suggest it is physical?

Obvisously this is all speculative but I find it very interesting

And what is wrong with using the term "singularity" as a placeholder for the physical event (I doubt it was a philosophical event ) that started it all? SOMETHING happened prior to the plank time, and we don't have a clue what it is. Why not use the term "singularity" instead of all the time having to say we don't know what happened? I don't get what's wrong with that.

 

[bcrowell]

SOMETHING happened prior to the plank time

I'm not convinced that that has to be true.

 

[Shenstar]

And what is wrong with using the term "singularity" as a placeholder for the physical event (I doubt it was a philosophical event ) that started it all? SOMETHING happened prior to the plank time, and we don't have a clue what it is. Why not use the term "singularity" instead of all the time having to say we don't know what happened? I don't get what's wrong with that.

Singularity gives certain impression in people's minds, especially the layman.

Also, most of cosmology are mathematical models based on data from what we cuurently understand. Most of which are probably not complete or not fully understood. In fact many which maybe completely wrong - we really don't know what happened but we now know a lot more than we used to.

 

[Cosmo Novice]

And what is wrong with using the term "singularity" as a placeholder for the physical event (I doubt it was a philosophical event ) that started it all? SOMETHING happened prior to the plank time, and we don't have a clue what it is. Why not use the term "singularity" instead of all the time having to say we don't know what happened? I don't get what's wrong with that.

My objection is you are assuming eventual understanding, if something is a "placeholder" by definition something needs to take its place - I am refuting that point.

I don't think we can assume SOMETHING happened pre Planck time, the idea the U came from nothing has to be considered, as if we assume it came from SOMETHING then where did that something come from - the question can be pushed back ad infinitum.

Yes we don't have a clue what happens at the singularity in space/time and I am happy with the term singularity as a statement of fact of the breakdown of theory at a certain point, what I am arguing is that the singularity may be physical, and therefore theoretically a singularity and the early stages of U may be forever beyond our understanding.

To clarify my refutation is the implied assumption of eventual scientific understanding of a singularity in space/time.