Finite Big Bang, Infinite universe?

[twofish-quant]

If you want to explain my philosophy of truth. Truth=survival. If you jump off a 100 story building, you aren't going to leave too many descendants. If you jump off a five story building, you break some bones and learn never to do that again. Over time (i.e. hundreds of millions of years), organisms become programmed to look for truth.

This matters with modeling, because in the last year the world just took an economic jump off a five story building, and so people have concluded that it's not a good idea to do that again. A lot of the problems involved taking models that were perfectly good for one domain and applying it where there was no data to support them. People took models of collaterialized default obligations that work beautifully with junk bonds and applied them to mortgage securities, which was a really really bad idea. (The basic problem is that when say an electronics factory goes bust, then the odds are that the concrete factory next to it still works. If one subprime mortgage goes bad, then chances are that all of the subprime mortgages in the world are also going bad at the same time.)

A lot of what I do involves thinking about probability and correlations, and there are some arguments that you use that get you punched in the gut by reality and some arguments that don't, and the probability arguments that the OP are using are a bit too much like the probability arguments that people used to justify a lot of the CDO non-sense. Certainty will get you killed in the markets. If you can model interest rates with 70% certainty, you are going to be a billionaire. The thing is that most people can't and the one's that seem to usually just got lucky.

It's actually curious but the mathematics of finance resemble a lot the mathematics of general relativity. There is a lot of modelling surfaces and curvative.

 

[Cuetek]

Agree again. On a quick look at the 'mathematical proof', it looks pretty 'serious' (especially to a layman like me).

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

But if you scrutinize what OP is really saying, the bottomline is:

I have looked at neutrons, atoms, planets, stars, galaxies, cluster and Big Bang. My theory works on these objects, and I know that the Bayesian Theorem (that just calculates probabilities) can help me to promote the idea that these relations also continues at the 'next level' – even if it has absolutely nothing to do with the physical reality.

Good lord, listen to yourself. You are saying that the rest of the examined universe has "absolutely nothing to do" with predicting the nature of the part of it that lies just beyond our view. Good luck with that philosophy.

-Cuetek

 

[Cuetek]

Absolutely. Then you do calculations, test that assumption against observations, and for the observations we can do, those assumptions seem to work.

I have. It's a high probability based on both the widely extant structure of the universe and the history of our discovery of it.

Since we have no data, saying whether something is regional or global is something that we can't say.

We have plenty of data. I use that data (the visible universe) to predict that we should look not for homogeneity but for differentiation (a dipole in the CMB for example).

You are making theological statements that are not supported by data.

Wrong. We are both projecting the visible data beyond our view. You with the cosmological principle and me with the hierachical principal. Mine is more extensive than yours is all.

As I mentioned there is nothing particularly wrong with that as long as you realize that you are going past the available data.

The cosmological principle goes past it as well. Apples and apples.

Ultimately, the problem is that you look at things, and you think "everything supports infinite hierarchy" whereas the astrophysical objects that I study tend not to have "infinite hierarchies."

Wrong. I only say that we should presume hierarchical diversity instead of homogeneity in the neear term. The new data will tell the tale (probably just like it has in the past showing us more and more of the hierarchy).

The problem is that if you try to create this sort of cosmology you end up with something that just doesn't fit the data. Any cosmology that assumes larger structures at this point just ends up being either irrelevant or inconsistent with the data. If you assume a self-similar fractal distribution of galaxies, you end up with galaxy distributions that just don't match what we see.

The homogeneity has only been measuered (WMAP) to a fine enough degree to assume a homogeneity for about 5000 times the diameter of the particle horizon (14 bil Lt Yr.) Anything beyond that, the distribution could begin to change up or down and we'd have no way of knowing.

Saying "I don't know" is not a bad habit. I think it's a good habit. If you can't see distant galaxies, you can't assume that anything is or is not there.

But the cosmological principle doesn't say that does it?

No it doesn't. The problem is that if you have something that is localized in space, then it's momentum becomes non-localized, and that means that any hierarchy gets washed out. Unless there is something basically wrong with our understanding of Heisenberg, then there are no new structures between the scales that we can see and Planck's length. Once you get to Planck's length, then quantum mechanics and GR become inconsistent, so there is new physics at smaller scales.

Also quantum mechanics imposes a lot of information limits. One electron is exactly the same as any other electron which means that there is no internal structure that you can use to mark an electron. The trouble with assuming structure is that you run into the Gibbs paradox. Basically the behavior of gases depends on the statistics of quantum mechanical structure. If there was structure, then gases would behave differently, because you could distribute energy across more states.

Translating what is giong on at infinitesimal levels seems to be very enigmatic. Nonetheless, quarks make nutrons make atoms make molecules, etc etc. hierarchy.

Actually, we *do* have a pretty good idea of what happens at the scale of quarks.

Sure we do.

(schnype) Ran out of time. Got to go to work.

House prices between 2001 and 2005 were going up radically. See a trend here?

Yes the trend went up. But the larger trend shows that house prices went up and down a lot. That's why I use all the scales of the universe rather than just one. See the trend here?

-Cuetek

 

[DevilsAvocado]

You need to run bayesian statistics using multiple assumptions to derive boundaries.

Agree. And most of all – you need not to exclude things that doesn’t fit the 'predefined' theory, like quarks.

 

[twofish-quant]

I have. It's a high probability based on both the widely extant structure of the universe and the history of our discovery of it.

However the fact that your arguments and probabilities seem to be unconvincing to people that work in cosmology and astrophysics should at least give you some cause for concern. In particular, unless you want to conclude that most astrophysicists are irrational, you do have to admit that rational people can at least debate and disagree with the principles that you suggest.

They may be self-evidently true to you, but they aren't to me, and they don't seem to be self-evidently true to most of the people in the field that have commented on this thread.

Part of the reason I don't want to go past the data, is that we are already making a ton of crazy assumptions and suppositions in our cosmological models of the universe. There's no point that I can see in adding anything that the data doesn't absolutely force you to make.

Wrong. We are both projecting the visible data beyond our view. You with the cosmological principle and me with the hierachical principal. Mine is more extensive than yours is all.

No I'm not. I'm saying that we can't make many statements about the ultra large scale structure of the universe. The assumption of a homogenous universe is something like a spherical cow or a flat earth. It's a guess that seems to give the right numbers, but it may be totally wrong for the problems I'm interested in, and it's obviously wrong for some of the one's that I'm not. The standard big bang model assumes that the Earth and sun do not exist, and that the whole universe is filled with a homogenous gas.

It's a workable model. Whether it's the ultimate truth or not is anyone's guess, but I'm a physicist. I'm in the numerical modeling business and not the ultimate truth business.

The big difference is that I'm at least willing to consider that the cosmological principle might will be wrong, and it's good for nothing more than "artistic inspiration." The other difference is that I can calculate helium and deuterium abundances, and you can't.

Wrong. I only say that we should presume hierarchical diversity instead of homogeneity in the near term.

Why? It just makes it more difficult to calculate deuterium abundances and galaxy clustering coefficients or think about galaxy formation.

The homogeneity has only been measuered (WMAP) to a fine enough degree to assume a homogeneity for about 5000 times the diameter of the particle horizon (14 bil Lt Yr.) Anything beyond that, the distribution could begin to change up or down and we'd have no way of knowing.

The point of a theorist is to come with observational tests. If you are convinced that the universe is hierarchical, then this is great for "artistic inspiration". Come up with some observational signature for that sort of model. There's a whole industry of people trying to do just that. It's a hard problem.

Suppose the density of the universe suddenly went up or down 6000 times the diameter of the particle horizon. What happens? Is it something we can detect? It is something that we can lobby Congress for to build some instrument that we can detect? What sort of statistics are we looking for?

But the cosmological principle doesn't say that does it?

What I'm trying to get across is what a "principle" means in physics. It's artistic inspiration. Invoking a principle is a start of a conversation and not a resolution to one. The reason for this is that people have invoked principles that turned out to be wrong. Two examples of this are the perfect cosmological principle in the steady-state universe or the static universe principle. You are not going to win an argument in physics by invoking any sort of principle, because so many of them have ended up being just wrong.

 

[DevilsAvocado]

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

Thanks for the advice and the very friendly attitude! Though I have not yet decided if I will accept your mentorship. It depends on if you can prove your own mathematical status, by explaining your choice of Boolean values in your own "numerical justification" of this very weird 'theory':

p(E|Fm) = 1 (true)
p(E|~Fm) = 0.5 ('half-true' !?)​

This is completely nutty and I haven’t decided if you do this on purpose to fit the 'theory' – or you just don’t know what you are doing, and don’t understand the rules of Bayes' Theorem.

The Boolean negation of true is not 'half-true', it’s false (0) and as a 'mathematical grand genius' you should know that.

If you avoid answering this mathematical question, https://www.physicsforums.com/showpost.php?p=2507923&postcount=50", I can only come to the conclusion that you are even more a layman than me, and then naturally the 'mentorship' is rejected. Sorry.

 

[DevilsAvocado]

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

Good lord, listen to yourself. You are saying that the rest of the examined universe has "absolutely nothing to do" with predicting the nature of the part of it that lies just beyond our view. Good luck with that philosophy.

-Cuetek

Maybe it’s a good idea you start listen to yourself. This is getting pretty close to the physics of Fawlty Towers.

Since when is science, physics and cosmology the art of statistically "predicting the nature"!? Running Bayes' Theorem to find a law of nature!? What would the world look like if Einstein worked for years on the solution for something like p(E|mc2)...!? OMG

The key to this is "the part of it that lies just beyond our view". When do you expect to get any data from that just beyond our view? Any measurements? Anything, besides homemade bayesian assumptions...?

This is a play with words and half-rotten math.

Let’s skip the math, and bring it down to (my) hillbilly-level, so we all can join the discussion. Now what you are saying is basically this:

1) A foreigner without maps visits Las Vegas for the first time.
2) He gets bored, and decides to visit Great Basin National Park, and rents a car.
3) After driving 40 km on the very straight U.S. Route 93 highway in Nevada, he gets extremely tired.

4) He’s a player and knows how to calculate probabilities. He runs Bayes' Theorem in his head and finds that the odds for the highway to continue like this are very good, 99.6%.
5) He activates the cruise control and falls asleep, feeling safe.
6) 10 km later he crashes at Pahranagat Valley.

Now, when we react on this behavior and don’t want to join the 'bayesian car', you act like a clown and don’t want to hear what we are saying...

"Probability theorems by definition *cannot* be proof of anything."

I absolutely agree.

 

[Cuetek]

However the fact that your arguments and probabilities seem to be unconvincing to people that work in cosmology and astrophysics should at least give you some cause for concern. In particular, unless you want to conclude that most astrophysicists are irrational, you do have to admit that rational people can at least debate and disagree with the principles that you suggest.

Well, as arrogant as it seems, I am saying that most astrophysicists are irrational on this one point. I'm saying that this irrationality is due to adherance to an old concept that is imminently understandable, but one that is by it nature is impossible to prove or disprove. I am saying that the more probable presumption is that the hierarchy of the universe will prevail. I am not saying that the cosmological principle is worthless. I am saying that it is only locally relavant.

They may be self-evidently true to you, but they aren't to me, and they don't seem to be self-evidently true to most of the people in the field that have commented on this thread.

Part of the reason I don't want to go past the data, is that we are already making a ton of crazy assumptions and suppositions in our cosmological models of the universe. There's no point that I can see in adding anything that the data doesn't absolutely force you to make.

I totally agree with the "we've already gone too far. But I think such trends are due to lack of data and prior insufficient assumptions that have led to us relying to completely on highly developed math models and not data. Many of those models are based on assumptions like the cosmological principle. It's not that scientists say that they believe the cosmological principle is true, but their research is predominantly based on how the cosmos would behave if it were true. Going back to the data, there is more data that says somewhere out there we will find that the cosmological principle will not longer be useful. If were are going to go too far, we should look at the widest possible interpretation of the data.

Bayes theorem is widely used in cosmology. The cosmological principle is, in fact, Bayesian. You look at the homogenety and imagine it goes much farther. But all Bayesian projections are limit at both ends of the scale. So too, in all probqability, will the hierarchical assumption be found wanting at some scale. But at our current point in history, it is more useful to guide our search for the nature of the universe beyond our instrumentation. More and more we will need to make wider assumptions as the data gets harder and harder to come by.

No I'm not. I'm saying that we can't make many statements about the ultra large scale structure of the universe. The assumption of a homogenous universe is something like a spherical cow or a flat earth. It's a guess that seems to give the right numbers, but it may be totally wrong for the problems I'm interested in, and it's obviously wrong for some of the one's that I'm not. The standard big bang model assumes that the Earth and sun do not exist, and that the whole universe is filled with a homogenous gas.

It's a workable model. Whether it's the ultimate truth or not is anyone's guess, but I'm a physicist. I'm in the numerical modeling business and not the ultimate truth business.

You are going to make an assumption one way or the other. Your models are fine, but should be formally limited to some 5000 times the particle horizon. The universe is strange. Think about the boson of gravity. While some bosons are bigger than others. No one in their right would think that a boson could be really big. But if the hierarchical principle is true, the forces that govern the structures at meta scales would have to be bigger and bigger as well.

The weak nuclear is very short range. The strong nuclear acts across a larger range. The electrical force, while theoretically infinite, acts mostly across molecular distances and some larger scales like lightning and even some theoretical cosmic scales. Gravity is clearly the farthest ranging, but near indetectable at molecular scales. So it would be prudent to imaging newer forces emerging at meta scales "above" the vis universe scale.

The boson for those meta scale forces might be huge by quantum standards. What if the graviton was the black hole? What if all matter derived gravity from by induction from being in the grip of a black hole field. If the big bang were a massive black hole most of the matter might still be on one side of us and we may be in an enroumous meta scale gravitational field. Perhaps it is ultimately that field alone which contributes the gravity ehibited by matter in it's grip.

I'm not saying this is how it is, just how a hierarchy might behave at larger scales. If the hierarchy prevails there will be larger forces of scale to organize the structures with additional meta scale explanations. Anything that moves us into such mindsets would be valuable if the hierarcy is true. And I feel the data we do have suggests the hierarchy is far more likely to prevail than is the homogeneity. Call it philosophical if you like, but it's a data-based philosophy and the theorist is going to have to make one or the other assumption. Assuming the CP is limited to 5000+ x the particle horizon makes both assumptions possible. (Actually, make it 50,000+ times the particle horizon, because it's absolutely homogenous out to 5000, so it will most probably remain roughly homogeneous much farther out.)

The big difference is that I'm at least willing to consider that the cosmological principle might will be wrong, and it's good for nothing more than "artistic inspiration." The other difference is that I can calculate helium and deuterium abundances, and you can't.

The CP is perfectly fine for local modeling, like curvature of the regions, just not for modeling the curvature of the "universe".

Why? It just makes it more difficult to calculate deuterium abundances and galaxy clustering coefficients or think about galaxy formation.

The CP is fine for local (5000+ times the particle horizon) calculation. The hierarchical principle should be used with hypothesizing beyond that limit.

The point of a theorist is to come with observational tests. If you are convinced that the universe is hierarchical, then this is great for "artistic inspiration". Come up with some observational signature for that sort of model. There's a whole industry of people trying to do just that. It's a hard problem.

The data will tell the tale sooner later no matter what. I'm just saying what the tale will more probably be in the long run. Such presumption will accelerate the process over waiting for the data to accurately limit the prior presumption.

Suppose the density of the universe suddenly went up or down 6000 times the diameter of the particle horizon. What happens? Is it something we can detect? It is something that we can lobby Congress for to build some instrument that we can detect? What sort of statistics are we looking for?

I've found numerous papers supporting the CP as fact (homogeneity inevitable) and only one paper defining it's limits (homogeneity currently reliable only out to 5000 x particle horizon). As I've suggested looking for a faint dipole in the CMB radiation is the first thing I'd do, or look for one side of the sky to have slightly larger voids etc. But it's what the expectation of inhomogeneity does to the thoerist's mindset that would have the most impact on research.

What I'm trying to get across is what a "principle" means in physics. It's artistic inspiration. Invoking a principle is a start of a conversation and not a resolution to one. The reason for this is that people have invoked principles that turned out to be wrong. Two examples of this are the perfect cosmological principle in the steady-state universe or the static universe principle. You are not going to win an argument in physics by invoking any sort of principle, because so many of them have ended up being just wrong.

I am gratified by the way you describe it above. You didn't sound so equivocal when we first started discussing this. My own grasp as to how to talk about it has improved as well. Peace. -Mike Harmon

 

[Cuetek]

p(E|Fm) = 1 (true)
p(E|~Fm) = 0.5 ('half-true' !?)​

This is completely nutty and I haven’t decided if you do this on purpose to fit the 'theory' – or you just don’t know what you are doing, and don’t understand the rules of Bayes' Theorem.

The Boolean negation of true is not 'half-true', it’s false (0) and as a 'mathematical grand genius' you should know that.

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.

 

[twofish-quant]

I am saying that the more probable presumption is that the hierarchy of the universe will prevail. I am not saying that the cosmological principle is worthless. I am saying that it is only locally relavant.

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.

But I think such trends are due to lack of data and prior insufficient assumptions that have led to us relying to completely on highly developed math models and not data. Many of those models are based on assumptions like the cosmological principle.

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.

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.

It's not that scientists say that they believe the cosmological principle is true, but their research is predominantly based on how the cosmos would behave if it were true.

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.

Your models are fine, but should be formally limited to some 5000 times the particle horizon.

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

The CP is fine for local (5000+ times the particle horizon) calculation. The hierarchical principle should be used with hypothesizing beyond that limit.

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.

As I've suggested looking for a faint dipole in the CMB radiation is the first thing I'd do, or look for one side of the sky to have slightly larger voids etc.

Which is what people have done.

But it's what the expectation of inhomogeneity does to the thoerist's mindset that would have the most impact on research.

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.

 

[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