Finite Big Bang, Infinite universe?

[Cuetek]

What I'm saying is you are basically misinterpreting how astrophysicists think.

1) The cosmological principle is not some sort of dogma, but a guess and a rough rule that allows people to make calculations
2) Without data, it's impossible to make firm statements about whether it is globally true or not. It *is* possible with the current data to say that assuming the cosmological principle allows us to make predictions about the universe that seem to accord with observations.

You are being very circumspect with the above characterization. However, when I hear cosmologist being interviewed, they say without qualification things like "if the universe is convext it will expand forever, if it is flat it will reach a steady state (or something like that) and if it's concave it will recollapse." These are reflexive predictions typical yet presumptuous beyond your above characterization. I say the reflex runs deeper than you think and that it is counter productive to a more realistic view of the proper extent and configuration of the universe.

It's no big deal. The data will tell the tale. But it may take longer.

Right, because you can then take the model and make predictions about the universe. The point that I'm making is that just because an astrophysicist makes an assumption in a model, doesn't mean that they think that assumption is true. If you want to *disprove* the cosmological principle, then what you need to do is to create a model that *assumes* that the principle is true, show that that model inherently creates results that don't match observations.

In essense, that's what I've done. I show a statistical probability that the universe will not conform to the cosmological principle and I make a prediction that the CMB will show evidence of inhomogeneity.

The highly developed math is because it is a really, really painful and difficult thing to go from theory to observational test. Suppose you were to assert that the density of the universe falls off very strongly an 2x the observational horizon. Going from that assumption to COBE power spectrum measurements is extremely painful.

Which is exactly the approach you need to take if you doubt that it is true. Let's assume that the cosmological principle is false. You predict X. You see X. That tells you absolutely nothing. So let's assume that the cosmological principle is true. You predict X. You see not-X. At this point the cosmological principle is proven wrong.

If you were seeing increases in the power spectrum at higher and higher scales, then we'd have a big problem. If there were systematic differences in the CMB in different parts of the sky, we'd have a big problem. You *assume* something is true, so that you have some idea what to look for in order to prove that it is false.

I'm assuming that the universe is more likely hierarchical than homogeous. I predict very slight variations on opposite sides of the sky due to my prediction that they big bang is finite in extent causing a slightly higher CMB temp and material density in the direction of it's "center". That we don't have the data yet is not being debated. My predictions, like many, will have to wait to be confirmed or refuted.

Why? I make statements about what the world looks like 10^6 times the particle horizon and that see if it makes any difference.

It will make no difference to your idealized model, But the farther away you make your characterizations the less coroborable they are. I probably don't really see what you are saying here.

Why? What you really need to do is to make a million different hypothesis and then throw them against the wall to see what sticks.

Well, I've made one, we'll see if it sticks. May take a while.

Which is what people have done.

I predict they will find what they are looking for. But only a few people are trying very hard to find something contratry to the CP. Most people are trying to confirm it.

What I'm saying is that I think you are misinterpreting what theorists are doing. Most papers in cosmology have nothing to do with the ultra-large scale structure of the universe, so there people assume the cosmological principle because the math is simpler, and if what you are doing isn't impacted by the ultra-large scale structure of the universe, you want to assume spherical cows and flat Earth's. Most papers in astrophysics outside of very narrow fields use Newtonian gravity because GR is just a pain to calculate.

If you are *expecting inhomogenity* then you assume homogenity. At that point you write papers invoking the cosmological principle, figure out the implications, and the look for deviations from observations. The problem with create models of inhomogenity is that once you've done that, you've restricted yourself to a particular model, which causes problems if both the CP and the inhomogenous model is wrong.

If you want to kill the CP, you need to absolutely avoid presenting an alternative model, and you need to focus on writing papers that assume the CP is true.

Also you be careful not to extrapolate someone's beliefs from the papers that they write. I don't know whether the CP is correct or not, but I'd certainly be depressed if it where.

I don't think I am overestimating how strongly most cosmologists believe that it is perfectly plausible that the universe is intirely homogeneous at the largest visible scales. I know that all good scientists will say that they don't know, but the what they look for in their work is a better indication of what they believe and that is confirmation of the CP for the most part.

I say that there is a strong tendency for all of us to prefer a presumption that makes the whole universe comprehensible under the current data set and assumptions. By making whatever is out there conform to the same disposition as what we can see of it, we have inadvertently limited our conception of the universe in a way that I feel is counter productive to discovering the wider truth.

It'm not refuting anything. I'm only trying to reveal the conceptual downside of CP. It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth. Some people find that more depressing than you find the ultimate implication of the CP.

 

[twofish-quant]

However, when I hear cosmologist being interviewed, they say without qualification things like "if the universe is convext it will expand forever, if it is flat it will reach a steady state (or something like that) and if it's concave it will recollapse." These are reflexive predictions typical yet presumptuous beyond your above characterization.

Those statements have nothing to do with the cosmological principle. If it's open, then it will expand forever. If it's closed, it will recollapse. If the universe isn't homogenous, then different parts of it will do different things. It's quite possible for a part of the universe to collapse while the rest expands. It's called a black hole.

I show a statistical probability that the universe will not conform to the cosmological principle and I make a prediction that the CMB will show evidence of inhomogeneity.

But you haven't mentioned what that inhomogeneity will look like. Yes if half the sky is black and the other half is white, then yes its homogenous. But it's also possible for the universe to be wildly inhomogenous, but that fact may not be obvious. In order to find inhomogenity you have to first assume homogenity, make a lot of predictions and then find deviations from that.

I'm assuming that the universe is more likely hierarchical than homogeous.

That's a problem. There are thousands of ways that the CP could be wrong, and if you propose an alternative model, you miss the main point of looking thinking about the CP.

I predict very slight variations on opposite sides of the sky due to my predction that they big bang is finite in extent causing a slightly higher CMB temp and material density in the direction of it's "center". That we don't have the data yet is not being debated.

Actually we do have lots of data, and other than dipoles, there is no measurable difference in CMB temp or material density. You could say that the amount is too small to currently see, but even with the data we have, we can exclude a lot.

And you could be missing the point. It's not hard to come up with inhomogenous models or hierarchical models which *don't* have differences in CMB and material density. We could by share chance be in the middle of the explosion. There could be some big dust cloud that is hiding things. The universe could be inhomogenous at scales much larger than the particle horizon.

My predictions, like many, will have to wait to be confirmed or refuted.

The whole point of a theorist is to come up with predictions that can be confirmed or refuted within a reasonable amount of time. If you can't think of one, then think harder. What detection levels will kill your model? The problem with things is that saying that "there is some hierarchy somewhere" isn't an interesting or useful statement. If we can't see it, you can always push things off to the future, and without perfect knowledge, which we we never have, you can't firm statements.

Now if you have a model that predicts a dropoff in density at 3x the particle horizon then it's dead already. If you have a model that predicts a dropoff in density at 8000x the particle horizon then it's interesting since we'll know within a decade if that's right or not. If you are predicting 10**6x particle horizon, then it's pretty useless.

I remember around 1995, when COBE first started sending out results, when there was a bit of excitement because it was showing that the CMB was smooth. Too smooth. There was a conversation in which someone mentioned that if they don't see any anisotropies in the next two or three months, then we are going to have some serious, serious explaining. But COBE finally saw anisotropies... Bummer.

Well, I've made one, we'll see if it sticks. May take a while.

Anything you can to so that you learn something in the next 5 to 10 years? Also suppose we do CMB measurements and find no global deviations to a factor of 10^-5, will that convince you that you are wrong? What about 10^-6, 10^-10, 10^-100000?

I predict they will find what they are looking for. But only a few people are trying very hard to find something contratry to the CP. Most people are trying to confirm it.

What about going in without too many expectations about what you are going to find?

The problem with the cosmological principle is that it can't be confirmed as a universal fact. The only thing that you can say is that the cosmological principle is correct to some limit.

I don't think I am overestimating how strongly most cosmologists believe that it is perfectly plausible that the universe is intirely homogeneous at the largest visible scales.

There is an observations fact that as far as we can tell the universe is homogenous at the largest scales that we can observe, and there aren't any observations that would suggest any deviation from global homogenity. That's just fact. It's *plausible* that the universe is globally homogenous. But there are lots of things that are plausible that aren't true.

I know that all good scientists will say that they don't know, but the what they look for in their work is a better indication of what they believe and that is confirmation of the CP for the most part.

No. You can't confirm the cosmological principle. It's impossible for the reasons that I mentioned above. The only thing that you can do is to refute it. So you work out that the CP says that some number ought to be 4. You do the measurement. If its 3.98, then you work on something else. If its 10, then it's interesting.

The other thing is that astrophysicists have often seen wild things that they didn't expect. No one in 1998 expected the universe to be accelerating.

I say that there is a strong tendency for all of us to prefer a presumption that makes the whole universe comprehensible under the current data set and assumptions.

None of the physicists I know have this point of view. If we understood everything, it would be really, really depressing. There wouldn't be any point in doing theory or observations if we had any clue what was really going on.

It'm not refuting anything.

You should be. The whole point of science is to come up with ideas, and then bash them to pieces.

It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

 

[DevilsAvocado]

It'm not refuting anything.

You should be. The whole point of science is to come up with ideas, and then bash them to pieces.

It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

Sorry, can’t help it – but this make me laugh!

 

[DevilsAvocado]

In Bayes theorem the variables you mention above are necessarily probabilities, not Boolean variables. The allowable values of these varables range inclusively between 0 and 1. If you like you can fudge them all around however you like to make the results come out however you see fit. That's the subjective nature of Bayes probability theorem. The assignment of the variables is the whole deal. I will be glad to debate why I chose the values I did, but you need to bone up on probability theorms first.

On this point, you are right and I’m dead wrong. I apologize and the laughs now are free and all on me.

(Silly ) Attempt to save my intellectual a*s.

I thought of this as:
p(E|Fm) = 1
Not(p(E|Fm)) = 0

This is clearly wrong. In this case it is correct though:
p(Fm) = 1
p(~Fm) = 0

or

p(Fm) = 1
Not(p(Fm)) = 0

Since we in this case only have 1 (or 100%) to play with... or what ever...​

But, I still say you are cheating. In your paper you write:

On the left hand side of the full equation, the term p(H|E) stands for the probability of hypothesis H being true given the existence of evidence E.

And you do the following assignments:

Probability ( A object being finite, multiply manifest constituent of a larger object | Current object is collectively assembled from smaller objects )​

Objection: Where is the evidence proving that if an object is "collectively assembled from smaller objects", it must also be finite??

In your paper you write:

Structural Analysis
Taking the material structure of the universe from quarks to galactic clusters as the evidentiary field we can calculate the probability of both rules of discovery being true for Big Bang as follows:
...
So we take one of the smallest object we can currently detect (the neutron) that we know contains yet smaller objects (quarks)
...

Objection: This is obvious cheating. In your analysis you claim to go all the way from quarks to clusters to prove your theory. But when the calculation starts you skip the quark (since it doesn’t fit your theory) and jump ahead to the neutron!?

When we protests about this, you make up your own world.

To think that we have a good idea of what all is happening in the material world at the scale of the quark is overzealous at best.

Thus dismissing a great part of the scientific establishment and billion dollar budgets:

It becomes ridicules when you at the same time claim to found the proof that "the Big Bang phenomenon is constituent to a larger, yet similar finite, structure", and yet admit:

Probability theorems by definition cannot be proof of anything.

Where is your proof??

How many billions of dollars are spent on this overzealous theory??

 

[Cuetek]

But you haven't mentioned what that inhomogeneity will look like. Yes if half the sky is black and the other half is white, then yes its homogenous. But it's also possible for the universe to be wildly inhomogenous, but that fact may not be obvious. In order to find inhomogenity you have to first assume homogenity, make a lot of predictions and then find deviations from that.

Like I've said before, the CP is not generally assumed the way you say it is. It is not assumed in order to refute it so much as confirm it. It is widely assumed to be quite true, and most studies by far attempt vigorously to confirm it with all manner of liberal projections of the data using math that is itself derivative of the CP. Only very few accepted studies search for limits on the CP using the data at hand (I site examples of both types of studies in post #19 of this thread).

You defend the presumption of the CP like some kind of essential straw man devised as a foil against the greater truth. That's human nature, not scientific method. The scientific method is to make presumptions that are best supported by the data, and that would be the hierarchical principle.

You can still use the observable homogeneity at large scales as a property to facilitate scientific investigation without having to improbably claim that it prevails absolutely as does the CP. I don't care how many ways you can find to distort some localized relevance in support of the CP, the greater context of the data shows unequivocally from quarks to galaxy clusters that the universe is far more probably hierarchical than homogeneous. Presuming a hierarchical universe does not inhibit the scientific examination the WAMP or group distribution data for adherence or divergence from some baseline homogeneity.

In following the tenets of the scientific method, one should let the predominant data guide the investigation. We are running out of hard data at these distant scales and must rely more and more on inductive reasoning. Theorizing, by definition demands inductive reasoning, and the CP lives only in the narrow confines of deductive thinking.

Mark my words, the homogeneity of the universe will not prevail. It will not be seen in the future as a valuable tool. Rather it will be seen as a philosophical relic that long overstayed it's utility.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

So true. So I guess you better get out of astrophysics, huh? Because only the CP allows humans to believe they can know the whole truth, by allowing the whole universe everywhere to be just like it is here. Conversely the HP would assure us to never know the whole truth of the universe beyond our view. All the best.

-Mike