Lambda-CDM theory - Woo or not?

[ben m]

The "beef" is that you can't demonstrate it exists in nature before you started trying to stuff it into a math formula and pointing to the sky and claiming "inflation did it". That's the beef.

Your beef, sir, is with the scientific method. You're *supposed* to discuss hypotheses in detail. You're *supposed* to compare them to experiments. The general pattern is that a good hypothesis agrees more and more closely with better and better experiments, and slowly becomes better-regarded ... and remains so until something better comes up.

That's where inflation is. For a decade people talked about the (rather outlandish) inflationary hypothesis, then for a decade or so its predictions started being verified one by one, then for another decade the data got better and better and nobody suggested an alternative, so you get to where we are today where maybe half or 3/4 of the papers call it "inflation" and the other 1/2 or 1/4 call it "the inflationary model".

General relativity, black holes? Same thing. Lots of theoretical work in the decades before x-ray astronomy. Then a few decades of people saying, "Cyg X-1, which has many of the properties of the hypothetical 'black hole' ...", then a few decades of "Cyg X-1, a candidate for being a'black hole ...", until today you get "Cyg X-1, a black hole of about nine solar masses ...". You're still welcome to present an alternative hypothesis for what SagA* is---and people do. (What was that shell-of-modified-vacuum theory a few years back?)

 

[sol invictus]

Such as?

There was a very similar claim some years ago. It was wrong.
I'd have to dig around to find it though - I don't recall the authors.

And? How do you know it's wrong just because it's "hard"?

Nice strawman. I said nothing of the kind.

And of course the "correct" method would necessarily be in alignment with inflation theory, is that it?

Probably that's the answer, but I hope not.

Inflation has *ZERO* (NO, NONE, NADA) experimental (with real control mechanisms) support! That is pure baloney! It's purely "theoretical" in nature and completely shy around a real lab.

That's it - keep plugging your ears and screaming at the top of your lungs.

Does that mean you want to create a more exotic version if the current one is falsified even by your own standards?

It means people would look for a new theory. It might be similar to the old one, or it might not, or more likely there would be many different ones.

People like what they know and what they are used to and they tend to resist change.

If you had any sense, you'd realize that tried and true theories that have stood the test of time are probably correct, or at least close to correct.

You can't falsify something that was never verified to exist in nature in the first place! Inflation's only claim to fame is the presumed homogeneous nature of the universe and even that is in hot dispute at the moment.

Keep screaming...

No known vector or scalar field will retain near constant density throughout several exponential increases in volume. Only inflation does that supernatural trick.

That's a lie. I just gave you an example - the Higgs condensate. Would you like me to prove mathematically that the Higgs condensate does not change its density as the universe expands?

 

[Michael Mozina]

That's it - keep plugging your ears and screaming at the top of your lungs.

It's you that keep plugging your ears here and ignoring fact. The *fact* of the matter is that inflation is shy around the lab and there has *never* been a "controlled" test of concept. Period.

It means people would look for a new theory. It might be similar to the old one, or it might not, or more likely there would be many different ones.

In other words it will simply "morph" into a variation on the same theme, irrespective of the fact the original concept was falsified.

If you had any sense, you'd realize that tried and true theories that have stood the test of time are probably correct, or at least close to correct.

For starters, Guth's inflation theory hasn't been around that long in the overall scheme of things. The worst part of this statement is it's more or less an appeal to popularity fallacy.

Keep screaming...

Keep burying your head in the sand....

That's a lie. I just gave you an example - the Higgs condensate. Would you like me to prove mathematically that the Higgs condensate does not change its density as the universe expands?

Please, by all means, show me how *ANY* condensate can increase it's volume exponentially several times over and retain a near constant density. You're whistling Dixie on that one. If you increase the volume by a factor of 10 and add no more particles to the condensate, it cannot possibly maintain a constant density.

 

[tsig]

http://en.wikipedia.org/wiki/Cosmic_inflation

Read the "observational status" area. CMB among other things.

If the only proof that you will accept, is making 2 tennis balls move away from each other in a lab due to cosmic inflation, then you are going to be impossible to argue with.

As was also pointed out however, we cannot create a star here on earth either. So everything that we know about them must be made up?

Also your ruler will be inflating a the same rate so you still couldn't measure the distance between the balls'

 

[Michael Mozina]

Your beef, sir, is with the scientific method.

No. The scientific method involves empirical testing. You skipped that part entirely evidently. You went right to the math, and started pointing at the sky. You failed to demonstrate that inflation even exists in nature or has any affect on nature *before* stuffing the idea into a math formula.

You're *supposed* to discuss hypotheses in detail. You're *supposed* to compare them to experiments.

What "experiment" are you talking about in the case of inflation? At best case you're comparing it to a *pure observation*, not doing a real "experiment" with real control mechanisms.

The general pattern is that a good hypothesis agrees more and more closely with better and better experiments, and slowly becomes better-regarded ... and remains so until something better comes up.

Sure, but an "experiment" has a "control mechanism", it is not a pure "observation".

That's where inflation is. For a decade people talked about the (rather outlandish) inflationary hypothesis, then for a decade or so its predictions started being verified one by one, then for another decade the data got better and better and nobody suggested an alternative, so you get to where we are today where maybe half or 3/4 of the papers call it "inflation" and the other 1/2 or 1/4 call it "the inflationary model".

Whatever you would like to call it, it has never been "verified" by "experimentation". None of it's "properties" (near constant density over multiple exponential increases in volume) have ever been verified. They are simply "assumed" as part of the theory itself. They have not been "demonstrated", they must be "taken on faith".

The fact a theory gains acceptance and becomes "popular" for awhile is irrelevant. Epicycle theories were popular for awhile as well. So what? Chapman's theories remained more "popular" then Birkeland's ideas and yet Birkeland's ideas won out in with advent of the space age. Popularity is not a reasonable barometer or "truth". Popular theories come and go all the time.

What you lack here is an empirical demonstration that inflation has any influence on anything. What you have is a math formula that can't be falsified or verified in any conceivable way. Even when the evidence suggests the the universe is not homogeneously distributed, inflation theory lives on. Nevermind the "holes" in the universe. Nevermind the "dark flows" that somehow never were "predicted" in Lambda-CDM theory, Lambda theory has to be correct anyway, and any and all observations that don't jive with the theory are simply ignored.

 

[Michael Mozina]

Also your ruler will be inflating a the same rate so you still couldn't measure the distance between the balls'

I don't suppose you can actually empirically demonstrate that an ordinary ruler can "inflate"? Is that something I have to have "faith" in as well, or is there any real experimental basis for this claim?

 

[Michael Mozina]

As previously mentioned, I agree that a comparison with gravity is not reasonable; consequently, in my view, inflation does not have the same kind of standing as gravity. I agree that inflation does appear to have a lot of "ad hoc" aspects, but, as I said, it's the best model we currently have.

Fair enough. Even still, the term "best" seems highly subjective to me, especially when talking about an idea that cannot be empirically verified in any conceivable way. It's a bit akin to calling a theory based on "magic" the "best" theory we have at the moment. If one puts no faith in magic, the whole idea of calling a magic theory the "best" theory we have sounds positively silly. If the theory was based upon a force of nature that could be physically verified, I could relate to your claim. As it stands, I "lack belief" in inflation, and there seems to be no empirical way to validate the concept before we start trying to apply the idea to astronomy. That's not encouraging if you're a skeptic.

 

[Ziggurat]

Gee, I don't know, but if we throw the apple at a 45 degree angle, it doesn't fall directly back to earth, instead it sort of follows a curved arching pattern. If we pick it up and throw it harder, it goes further before it hits the earth. Do you figure Newton might have been smart enough to put two and two together?

And yet, it doesn't fall like an apple. An apple falls at 9.8 m/s², but the moon doesn't. So how can they be the same?

No, his equations did not come from pure speculation, but from actual tests that worked on Earth and could also be applied to objects in space.

I've told you already that this is completely wrong. Newton did not (and could not) test the 1/r² here on earth. So for you to contend that his equation came from tests on earth is a complete fiction. And after being called out on this specific point multiple times, I have to conclude that either you're a liar, or you're just clueless ahout what 1/r² means.

Inflation is a "process" because you say so

No, because that's what the model is: a model of a process, not a force. The force is just gravity.

The physics is not irrelevant.

The name is. Calling physics magic doesn't make it less real.

If you can't physically distinguish between magic and inflation

Oh, but we're not talking about real magic: we're talking about a model which you decided you would label "magic". You can label Newtons laws as magic too, won't make them any less valid.

 

[tsig]

I don't suppose you can actually empirically demonstrate that an ordinary ruler can "inflate"? Is that something I have to have "faith" in as well, or is there any real experimental basis for this claim?

No, if you want to do some studying and gain some knowledge you could understand these things instead of having faith.

"Inflation is a general term for models of the very early Universe which involve a short period of extremely rapid (exponential) expansion, blowing the size of what is now the observable Universe up from a region far smaller than a proton to about the size of a grapefruit (or even bigger) in a small fraction of a second. This process would smooth out spacetime to make the Universe flat, and would also resolve the horizon problem by taking regions of space that were once close enough to have got to know each other well and spreading them far apart, on opposite sides of the visible Universe today.

Inflation became established as the standard model of the very early Universe in the 1980s. It achieved this success not only because it resolves many puzzles about the nature of the Universe, but because it did so using the grand unified theories (GUTs) and understanding of quantum theory developed by particle physicists completely independently of any cosmological studies. "

http://www.lifesci.sussex.ac.uk/home/John_Gribbin/cosmo.htm

 

[Perpetual Student]

Fair enough. Even still, the term "best" seems highly subjective to me, especially when talking about an idea that cannot be empirically verified in any conceivable way. It's a bit akin to calling a theory based on "magic" the "best" theory we have at the moment. If one puts no faith in magic, the whole idea of calling a magic theory the "best" theory we have sounds positively silly. If the theory was based upon a force of nature that could be physically verified, I could relate to your claim. As it stands, I "lack belief" in inflation, and there seems to be no empirical way to validate the concept before we start trying to apply the idea to astronomy. That's not encouraging if you're a skeptic.

Magic? It's a theory that fits a multitude of observations, and as you have pointed out has been modified with a few ad hoc adjustments in recent years. I have followed inflation and its development from the time it first emerged in the eighties -- and for me it does take a great leap to accept it since it is so foreign to my everyday experiences and my limited knowledge of the physics involved. The bottom line is: there is no better model and there does not appear to be one on the horizon. With all the creative theorists in the world, if there is ultimately a better answer, it will likely emerge some day.
Unfortunately, There are many aspects of prevailing cosmological theories that are counter-intuitive -- I struggle with this reality often, but flailing away with no alternative theory is a useless exercise.

 

[ben m]

No. The scientific method involves empirical testing. You skipped that part entirely evidently. You went right to the math, and started pointing at the sky. You failed to demonstrate that inflation even exists in nature or has any affect on nature *before* stuffing the idea into a math formula..

We also failed to demonstrate that black holes exist before writing formulas about their entropy.

We failed to demonstrate that the W and Z boson exist before writing formulas predicting their masses and couplings.

We failed to demonstrate the existence of quantum computers before writing algorithms for them.

And we've said it a dozen times: inflation is our *best* model for describing the observed isotropy and curvature of the Universe. We're studying that model mathematically, and studying the isotropy and curvature and so on experimentally. No one claims to have the final answer, so the whole premise of your "scientists think they know everything" complaint is bunk.

Your stated attitude amounts to either "Humans are forbidden from thinking scientifically about exotic states of matter" or "Nature is forbidden from including phenomena that aren't reproducible on Earth".

But I don't think that's your real attitude---I think your real attitude is "I don't like standard cosmology and I want to find ways to call its practitioners wrong". You invented an objection before thinking about it very hard, and you're defending it only evasively. You're welcome to drop it whenever you feel up to it.

 

[Reality Check]

Well, in fairness, MACHO version of "dark matter" theory are in fact "real" in every conceivable way, even by my own standards.
No. You have observed what you believe to be acceleration which you *interpret* to be related to "dark energy". You may also have observed "missing mass", but not "dark matter".

Astronomers (not me) have measured the acceleration in the expansion of the universe. That is an actual confirmed observation.
Dark energy is a label for the cause of the observed acceleration.

Sure and and long as you stick to MACHO variations of DM theory I have no complaint.

Why MACHO? What is the difference between dark matter being

• A big thing like an astronomical body) or
• A small thing such as another elementary particle like electronsa, neutrinos, etc.?

Again, you didn't observe either of these things. Astronomers simply proposed these things as "gap fillers" in an otherwise failed theory of cosmology.

They are "fillers" as in labels for the causes of actual observed phenonomena. There are however no gaps to fill.
What is this "otherwise failed theory of cosmology" that you refer to?

It is not the Lambda-CMB model as it is a completely successful model.

As ben m told you:

• The Lambda-CDM model exactly matches the following data:
  • the CMB power spectrum;
  • all CMB polarization spectra and bispectra;
  • all known CMB non-Gaussianity tests;
  • the distribution of galaxy cluster sizes (and its time evolution),
  • velocity dispersions,
  • x-ray virial temperatures,
  • weak lensing masses,
  • and strong lensing masses;
  • the rotation-curve evidence for dark matter in galaxies;
  • the Hubble constant and its time evolution;
  • the lyman-Alpha forest angular size spectrum;
  • the ratio of H/D/He/Li in unevolved gas clouds;
  • the Gunn-Peterson trough in quasar spectra.
• The Lambda-CDM model fails to match the following data:
  • nothing whatsoever.

Why do you believe it to be "likely" that we will observe something in solar system in the future that we can't observe right now?

Dark matter exists in the Solar System. We are smart and technology always advances. Thus it is likely that we will observe it in the future.

FYI, there are "dark energy" theories out there that are directly related to, and attributed to EM Fields.

http://arxiv.org/abs/0812.1970

Even mainstream theory may *depend upon* EU Theory in the final analysis.

That paper needs someone with more expertise to comment (sol?).

 

[Reality Check]

You can change the words to "unicorn", "pixie" and "fairy" if you want. The words do not matter. The science and mathematics do matter. Changing the words does not change the model and its match to the measurements.

So, in other words you can't *physically* differentiate between inflation and magic. As long as the math is good, the physics doesn't even matter, is that it?

What if I used "a", "b" and "c" for "dark matter", "dark energy" and "inflation". Does that make them into "magic"?

An example: I hereby rename gravity as "fairy dust" and "Newtons theory of gravity" becomes "Newton's theory of fairy dust". So what has changed? The theory still gives the same results.

I'm afraid that the *physics* involved is also just as important as the *MATH*.

That is right. It is a pity that you are ignoring the physics.

 

[Tubbythin]

I believe that the inverse square law [ 1/r² ] discovered by Newton was verifiable in his time by the orbits of the moon and planets.

That is precisely the point. Newton's law of gravitation was verifiable if we look outside the Earth based labs. But MM was saying that inflation cannot be taken seriously because we cannot verify it on Earth. So by MM's logic, Newton shouldn't have been taken seriously at the time.

He explained the observation of Kepler that planets travel in orbital ellipses and Kepler's equal areas law. The hypothesis that gravity was universal and extended to falling objects on earth followed and was consistent with Galileo's observations. I have no ax to grind in this discussion; however I do believe any comparison of Guth's theory of inflation and Newton's universal law of gravitation is a stretch.

The point is not so much whether NG and inflation are in someway analogous, but whether a demand that science has to be tested in a controlled lab environment is reasonable or not.

 

[Tubbythin]

If you had any sense, you'd realize that tried and true theories that have stood the test of time are probably correct, or at least close to correct.

For starters, Guth's inflation theory hasn't been around that long in the overall scheme of things. The worst part of this statement is it's more or less an appeal to popularity fallacy.

I'm sorry, where's the appeal to popular authority in Sol's sentence?

 

[Reality Check]

Hi Michael Mozina
Controlled lab environments are nice to have.

But it sounds like you are suggesting that no useful science can be done by observation of the universe because the universe is not a controlled environment.

The fact that the universe is big, varied, full of stuff and uncontrolled gives plenty of useful science. A large number of uncontrolled experiments where the universe sets the parameters can be as useful as a large number of controlled experiments where a scientist sets the parameters. The universe may miss some parameter sets - on the other hand the universe may apply a set of parameters that a scientist might not think of.

Here is an example of a useful observation (uncontrolled experiment): Total eclipses of the Sun allow testing of General Relativity.
For some reason we cannot control total eclipses .

I am quite sure that there are scientists that are glad the universe contains a great variety of plasmas - including some plasmas that cannot be created here on Earth.

We can do fusion here on Earth but we cannot (yet) do sustained fusion as in the Sun. This is the fusion process that creates the elements like carbon which allow us to exist. Should we ignore the science that observing the Sun and other stars reveals just because we do not have a pet star in a lab?

Perhaps you can suggest how we can study the formation of stars without looking at stars?

Should we ignore pulsars and magnetars just beacuse we cannot build big enough magnets in labs to match the strength of their magnetic fields? (We are getting close to the magnetic field strength of pulsars though - only out by a factor of 10 or 100).

What about the Lyman-Alpha forest? We would need a pet universe in a lab to do controlled experiments on that.

 

[sol invictus]

Please, by all means, show me how *ANY* condensate can increase it's volume exponentially several times over and retain a near constant density. You're whistling Dixie on that one. If you increase the volume by a factor of 10 and add no more particles to the condensate, it cannot possibly maintain a constant density.

Very well.

First, this is the most basic fact about inflation. If you don't know it, you know nothing about the topic. Odd that someone so totally ignorant would start a thread ridiculing the experts in the field, isn't it?

Now for the math: take a scalar field and couple it to gravity.

[latex]${\cal L} = -(1/2) \grad_\mu \phi \grad^\mu \phi - V(\phi) + R$[/latex], where R is the Ricci scalar curvature for the expanding metric [latex]$ds^2 = -dt^2 + a(t)^2 d \vec x^2$[/latex]. You can immediately verify that if [latex]$V'(\phi_0) = 0$[/latex] for some \phi_0, then \phi(t,x) = \phi_0 is a solution to the equations of motion. If there are no other sources of energy around, one then immediately gets a solution where a(t) grows exponentially with time.

Now, the proper energy density on this solution is simply [latex]$T^0_0 = V(\phi_0)$[/latex] (you can derive this by varying the scalar field part of the lagrangian with respect to the metric). And that's it - we're done. The energy is constant.

This analysis is completely general - it applies to the Higgs (which is obvious, by the way - if the energy in the Higgs condensate redshifted, the expansion history of the universe over the last 10 billion years or so would be completely and totally different than it is) and to every other scalar field.

So, you now have three choices:

1) find a mistake in the math (good luck with that)

2) admit you were wrong, and explain to us why you came in with guns blazing mocking a topic you're so totally ignorant of, or

3) run away and hide.

Which will it be?

 

[sol invictus]

Please, by all means, show me how *ANY* condensate can increase it's volume exponentially several times over and retain a near constant density. You're whistling Dixie on that one. If you increase the volume by a factor of 10 and add no more particles to the condensate, it cannot possibly maintain a constant density.

Very well.

First, this is the most basic fact about inflation. If you don't know it, you know nothing about the topic. Odd that someone so totally ignorant would start a thread ridiculing the experts in the field, isn't it?

Now for the math: take a scalar field and couple it to gravity.

[latex]${\cal L} = -(1/2) \partial_\mu \phi \partial^\mu \phi - V(\phi) + R$[/latex], where R is the Ricci scalar curvature for the expanding metric [latex]$ds^2 = -dt^2 + a(t)^2 d \vec x^2$[/latex]. You can immediately verify that if [latex]$V'(\phi_0) = 0$[/latex] for some \phi_0, then [latex]$\phi(t,x) = \phi_0$[/latex] is a solution to the equations of motion. If there are no other sources of energy around, one then immediately gets a solution [latex]$a(t)=e^{H t}$[/latex] where the space grows exponentially with time ([latex]$H^2=(8 \pi G_N/3) V(\phi_0)$[/latex]).

Now, the proper energy density on this solution is simply [latex]$T^0_0 = V(\phi_0)$[/latex] (you can derive this by varying the scalar field part of the lagrangian with respect to the metric). And that's it - we're done. The energy is constant.

This analysis is completely general - it applies to the Higgs (which is obvious, by the way - if the energy in the Higgs condensate redshifted, the expansion history of the universe over the last 10 billion years or so would be completely and totally different than it is) and to every other scalar field.

So, you now have three choices:

1) find a mistake in the math (good luck with that)

2) admit you were wrong, and explain to us why you came in with guns blazing mocking a topic you're so totally ignorant of, or

3) run away and hide.

Which will it be?

 

[Tubbythin]

So, you now have three choices:

1) find a mistake in the math (good luck with that)

2) admit you were wrong, and explain to us why you came in with guns blazing mocking a topic you're so totally ignorant of, or

3) run away and hide.

Which will it be?

You forgot 4:
Ask the same question again and pretend you never answered it.

There's a precedent for 4 already.

 

[Perpetual Student]

Very well.

...

[latex]${\cal L} = -(1/2) \partial_\mu \phi \partial^\mu \phi - V(\phi) + R$[/latex], where R is the Ricci scalar curvature for the expanding metric [latex]$ds^2 = -dt^2 + a(t)^2 d \vec x^2$[/latex]. You can immediately verify that if [latex]$V'(\phi_0) = 0$[/latex] for some \phi_0, then [latex]$\phi(t,x) = \phi_0$[/latex] is a solution to the equations of motion. If there are no other sources of energy around, one then immediately gets a solution [latex]$a(t)=e^{H t}$[/latex] where the space grows exponentially with time ([latex]$H^2=(8 \pi G_N/3) V(\phi_0)$[/latex]).

Now, the proper energy density on this solution is simply [latex]$T^0_0 = V(\phi_0)$[/latex] (you can derive this by varying the scalar field part of the lagrangian with respect to the metric). And that's it - we're done. The energy is constant.

This analysis is completely general - it applies to the Higgs (which is obvious, by the way - if the energy in the Higgs condensate redshifted, the expansion history of the universe over the last 10 billion years or so would be completely and totally different than it is) and to every other scalar field.

...

OK, is there a way you can provide a verbal description of how "you increase the volume by a factor of 10 and add no more particles to the condensate," and you "maintain a constant density."? Is there some analogy that a non-physicist might grasp? I'm not doubting the validity of your demonstration (I have no way to do so); I am merely interested.