Split Thread Michael Mozina's thread on Dark Matter, Inflation and Cosmology

[DazzaD]

Is "God did it" (with blatantly pilfered math) a form of "empirical science"? if not, why not?

You are avoiding the question.

I never claimed "god did it". I never even claimed that I had a definition of "empirical science". But you seem to maintain it as a major part of your arguments so I thought it important enough to clarify once and for all.

Please.

 

[Michael Mozina]

You are avoiding the question.

Not really. I'm just trying to get you/others to consider the necessity of an "empirical demonstration of concept". The math in the GR formula doesn't make something physically "real". I could stuff any term in there, "magic energy", "Michael's fancy new form of energy", "God energy", whatever, and slap on some math but what have I actually demonstrated? If I cannot demonstrate that Michael's fancy new energy exists in nature in an empirical way, what's the point of stuffing it into a GR formula and pointing at the sky?

 

[ben m]

You're *assuming* that whatever is causing acceleration is related to "gravity".

I am not assuming. I have examined all of the candidates that have been presented. GR appears to work perfectly, as long as the vacuum has an energy density of 10^-27 g/cc (a totally plausible QFT behavior for the vacuum, although the value is a surprise.) E&M doesn't work at all. MHD doesn't work at all. Cosmic-ray-pressure doesn't work at all.

Gravity is the only candidate, MM, by process of elimination If you disagree, get to work on an alternative and find where the missing factor of 100000000000000000000 is hiding.

 

[Michael Mozina]

Thought of as an energy density, the CC fits perfectly into Einstein's equations.

Even I accept that notion.

The CC is a form of energy and pressure, and therefore it's an additive term that changes the diagonal elements of T. It can arise in many ways: from quantum vacuum energy as above, from a scalar field potential that's non-zero in a minimum, from a 4-form "electric" flux (don't go bananas MM, that's not a standard electromagnetic field energy, it's something much weirder involving significant new physics), or simply from a shift in the zero-point of potential energy.

Ah, it's Friday and everything. I was really looking forward to having a beer and going bananas.

 

[ben m]

. I could stuff any term in there, "magic energy", "Michael's fancy new form of energy", "God energy", whatever, and slap on some math but what have I actually demonstrated?

Sure your could. You would plug in a new made-up term, use it to calculate an equation of motion, and compare that equation of motion to the various observed ones.

If there is a motion somewhere which is impossible to explain without your term, but easy to explain with your term, then you may have a good hypothesis. That's what Mercury's perihelion advance was. That's what various scientists (and pseudoscientists) want the Pioneer Anomaly to be. That's what CP violation is. Make a hypothesis, compare it to the data.

 

[Michael Mozina]

I am not assuming. I have examined all of the candidates that have been presented.

So what? What about the ones that haven't been presented?

GR appears to work perfectly,

GR works perfectly to do what? Without something outside your mass thingy, "gravity" is going to crush your mass thingy instantly. That's why you needed inflation and dark energy.

as long as the vacuum has an energy density of 10^-27 g/cc (a totally plausible QFT behavior for the vacuum, although the value is a surprise.)

An "energy density" of "what"?

 

[Michael Mozina]

Sure your could. You would plug in a new made-up term, use it to calculate an equation of motion, and compare that equation of motion to the various observed ones.

If there is a motion somewhere which is impossible to explain without your term, but easy to explain with your term, then you may have a good hypothesis. That's what Mercury's perihelion advance was. That's what various scientists (and pseudoscientists) want the Pioneer Anomaly to be. That's what CP violation is. Make a hypothesis, compare it to the data.

Hey look, I can pilfer your math, add "Michael's make believe magic energy" and I can prove that my magic new form of energy causes the universe to accelerate away into the sunset!

 

[ben m]

I wouldn't object to using MHD formulas related to real physical processes in that term for instance.

I did. MHD processes contribute to the EFE term only via their net energy density. The average energy density of all of the EM waves, MHD waves, particle beams, etc., in the Universe gets plugged into the stress-energy tensor term, not the CC term. The resulting tensor (containing both the waves themselves and, e.g., the stars that emit them) has positive pressure, necessarily gets weaker as the Universe expands, and contributes to deceleration, not acceleration.

 

[ben m]

Hey look, I can pilfer your math, add "Michael's make believe magic energy" and I can prove that my magic new form of energy causes the universe to accelerate away into the sunset!

Does your "Michael's magic energy term" have the same gravitational-source properties as 10^-27 g/cc of vacuum energy? Then, yes, that's a stupidly-named hypothesis that indeed describes the data.

Likewise, I could take the currently-unnamed "Gauss's Law but for magnetism" law, div.B = 0, and say that it means that the Hoober-Bloob operator muffled with the Mickeymouse field is zero. Uh, sure, buddy, whatever. My equation may be correct, but I don't expect PRL to publish it.

 

[ben m]

So what? What about the ones that haven't been presented?

There aren't that many forces in Nature. EM, gravity, weak, strong. I ruled out three, leaving one.

By your logic I might as well throw out the top quark too. "You continue talking about this rare particle, and you say it's the only thing that fits the CDF data, but maybe someday another hypothesis will fit the CDF data just as well." And, y'know, everything else. Quantum mechanics is pretty weird, maybe we should throw it out in vague anticipation of a non-weird alternative coming along someday.

If another hypothesis does come along, science will look at it and self-correct. That's how it works.

GR works perfectly to do what? Without something outside your mass thingy, "gravity" is going to crush your mass thingy instantly. That's why you needed inflation and dark energy.

Inflation? Don't get inflation mixed up with dark energy again, Michael.

And: How do you know the vacuum energy density is zero? Did God whisper it into your ear? Is it an axiom of your religion? Seriously, how certain are you that it's zero? To how many digits of precision?

Back in the real world, quantum field theorists never thought it was obviously zero. String theorists aren't telling me it's obviously zero. The Casimir effect isn't telling me it's obviously zero (as you have repeatedly agreed.) Einstein, de Sitter, Eddington, Lemaitre, Friedmann, etc. sure didn't think it was obviously zero. They all said "I don't know what the vacuum energy density is, let's let the data decide". What do you think you know that's different?

 

[Tubbythin]

as far as I know the only source for Einstein having said that the CC was his biggest blunder is Gamow 40 years or so after the fact. So one might take that with a grain of salt.

Was it not the fact that he fine-tuned it to give a static Universe with an unstable equilibrium that was the blunder anyway? Not the fact that he gave a non-zero CC. As a non-expert the latter seems reasonable whilst the former seems pretty daft for one of the greatest minds in physics. Is it just hindsight that makes this seem so obvious? Or am I missing something?

 

[Tubbythin]

It seems to me that setting the CC to zero and eliminating it are pretty much the same thing.

Saying the best value for the CC from observational data is 0 and saying the CC has to be 0 based on the theory of GR are completely different things.

Those two actions certainly have the same result.

One is a best fit to the current data (at the time), the other is a claim that a CC is unphysical. These are completely different claims even if the results are the same.

Look, he called the CC his biggest blunder!

Did he? Or did he think his fine-tuned, unstable Universe was a blunder? Or did he just not say it? And what does it matter anyway?

I have no problem with using a value of the CC that is consistent with modern observations. But the claim that it is Einstein's GR that somehow requires the CC when he totally rejected seems to be a bit bogus.

I think ben m and sol have dealt with this better than I possibly could.

 

[Chucky]

I did. MHD processes contribute to the EFE term only via their net energy density. The average energy density of all of the EM waves, MHD waves, particle beams, etc., in the Universe gets plugged into the stress-energy tensor term, not the CC term. The resulting tensor (containing both the waves themselves and, e.g., the stars that emit them) has positive pressure, necessarily gets weaker as the Universe expands, and contributes to deceleration, not acceleration.

I don't want to start a derail, and I'm sure this is less than exact, but if we were actually floating around in a multiverse and having our universe pulled at by gravity forces outside of it, would the effect perhaps not be similar? I'm not trying to suggest that this is the case, I'm simply wondering if this would be analogous to what a strengthening negative pressure would look like. Certainly not exact and probably wrong altogether, but can you see what I'm asking and does it fit in at all with the acceleration scenario?

 

[ben m]

I don't want to start a derail, and I'm sure this is less than exact, but if we were actually floating around in a multiverse and having our universe pulled at by gravity forces outside of it, would the effect perhaps not be similar? I'm not trying to suggest that this is the case, I'm simply wondering if this would be analogous to what a strengthening negative pressure would look like. Certainly not exact and probably wrong altogether, but can you see what I'm asking and does it fit in at all with the acceleration scenario?

We discussed this a few pages ago; see http://www.internationalskeptics.com/forums/showpost.php?p=5557104&postcount=846. The "surrounding" overdensity needs to be extremely contrived in order to make the Earth see isotropic acceleration; observers in places other than Earth (i.e., most of the Universe) see a really badly non-isotropic universe.

More generally: the Cosmic Microwave Background is very sensitive to changes in the matter distribution of the Universe. Most things you can think of doing by moving matter around will affect the CMB in an obvious way. Dark energy, on the other hand, tends to leave the CMB alone and have larger effects at late times.

Even more generally: I don't think you can have any effect on our Universe by putting mass distributions outside of our light-cone. Perhaps Sol can correct me on this.

 

[sol invictus]

Was it not the fact that he fine-tuned it to give a static Universe with an unstable equilibrium that was the blunder anyway? Not the fact that he gave a non-zero CC. As a non-expert the latter seems reasonable whilst the former seems pretty daft for one of the greatest minds in physics. Is it just hindsight that makes this seem so obvious? Or am I missing something?

That hadn't occurred to me - it's an excellent point. About how obvious it is, I share your opinion. It really does seem obvious.

But even geniuses can make simple mistakes... and as you say, that mistake is quite probably the blunder he was referring to. I certainly can't think of anything else Einstein got wrong that was remotely close to that simple. Quantum mechanics is one famous example, but that's an extremely subtle issue that's not properly understood even today. Black holes are another example, but again, that was very difficult and took decades to get straight.

 

[edd]

Even more generally: I don't think you can have any effect on our Universe by putting mass distributions outside of our light-cone. Perhaps Sol can correct me on this.

I think there could be some small effect thanks to inflation? But I don't think MM would like that much.

edit: and it would be really teeny I think

 

[Zeuzzz]

I think anyone reading this thread will appreciate this revised publication:

http://journalofcosmology.com/Multiverse5.html

Cosmic Agnosticism, Revisited
Timothy E. Eastman, Ph.D.
Plasmas International, 1225 Edgevale Road Silver Spring, MD 20910
Abstract

The Big Bang (BB) research program has been highly successful in generating fruitful scientific hypotheses and tests, and has achieved a significant level of confirmation for many hypotheses. However, outstanding questions remain and substantial alternative cosmology models, which also have been fruitful, remain viable and continue to evolve. This paper reviews outstanding issues in cosmology, both those specific to BB and general limitations in developing a comprehensive cosmology. It is unknown how well the BB or any alternative approach will stand up to future tests using burgeoning new data sets and future critical tests and falsification instances. At the present time, there appear to be advantages and yet serious problems for all options – they may all be wrong – thus, the "agnosticism" in physical cosmology. Suggestions are provided for constructive dialogue in cosmology considered in both its philosophical and physical aspects.

Key Words: Cosmology, Big Bang, alternative cosmologies, plasma astrophysics, observational-inductive framework, scientific methodology

 

[Michael Mozina]

I think it's time you guys give us your "genesis" chapter that starts something like:

"In the beginning was the mass thingy that you're applying GR theory to. The mass thingy is A) about the size of an atom, B) a few centimeters, C) smaller than a breadbox, D) you don't know.

Outside the mass thing is A) nothing, B) a "false' (but positive) vacuum energy density, C) a "negative pressure in a vacuum" thing.

Where and why did this inflation thing do it's thing, from the inside out, the outside "sucking" it apart? Where does "dark energy" fit into all this? Was "dark matter" created before or after electrons?

Throw me a few bones here and give me some kind of genesis story I can sink my skeptical teeth into.

 

[Zeuzzz]

I think it's time you guys give us your "genesis" chapter that starts something like:

I very much doubt you'll get this. The people who have suffered explaining the process numerous times are now probably too embarressed to keep touting that nonsense so have given up.

I'll have a go though.

Nothing went bang.

Oh dear, the most basic princple of cause and effect broke down straight away.

Wouldn't it be crazy if a theory like that gained popularity eh?

 

[Reality Check]

They do exist which is what pushes your plates together.

They do not exist. There are no physical wavy lines in QM.

Then the article I cited must also be wrong too?
http://focus.aps.org/story/v2/st28

The article is right and has no wavy lines.

Replace "force" with "pressure" and I agree with you.

Thta is a problem because you cannot replace force with pressure.

The *NET* force is directional and geometrically driven. That's all your minus sign ultimately means.

The net force on the surface of the plate is away from the plate. That gives is a negative sign. That means that the pressure is negative.
But you can do this for yourself.

A high school physics assignment for you:

First asked 3 February 2010
Calculate the pressure caused by the big blue arrows on the left hand plate. Assume that the force is F₁.
Calculate the pressure caused by the small blue arrows on the left hand plate. Assume that the force is F₂.
Calculate the pressure caused by the big blue arrows on the right hand plate. Assume that the force is F₁.
Calculate the pressure caused by the small blue arrows on the right hand plate. Assume that the force is F₂.

Remember that a force that points in the opposite direction to another has an opposite magnitude, e.g. if the first force has a positive value then the second force has a negative value. So you will have to set a convention about how to determine this, e.g. forces pointing to the right are positive.
N.B. Apply the same convention to both plates.

Your math skills should be up to this as it just requires the basics.

Or you can looks ath the post where I showed that negative pressure exists from the very defintion of pressure in as simple a manner as possible. It is more complex in cosmolgy though because there are no surfaces and so you have to use the more general defintion of pressure as p = -dE/dV.

Higher pressure between the plates would move them further apart. Likewise a lower pressure between the plates causes them to be pushed together.

Wrong
The scientific defintion of pressure means that it cannot move anything. Pressure is a number. It has no direction. It is not a force. A difference in pressure is the subtraction of 2 numbers.
It is the force that that moves things.

No. It just turns out you personally (and a few others) can't tell the difference between directional force of the EM field (what your minus sign ultimately relates to) and "negative pressure" in a "vacuum".

No. It turns out thet you have no understanding of physics.
An EM field has nothing to do with the Casimir effect.

I was right whan I said you would ignore the physics:

MM has been told this before but I do mot remember actual values given to him. So here is more physics for him to ignore:
From Teaching the photon gas in introductory physics (PDF)

Photon pressure P = bT⁴/3 where b is a constant involving h, c and k. This is constant at constant temperature. In controlled empirical experiments*, the pressure between 2 parallel plates varies with their separation. A good review is Casimir force between real materials: experiment and theory (23 Feb 2009).

If you have an ideal gas of 1.00 mol of monatomic argon at P = 1.01 10⁵ Pa, V = 2.473 10²² m3, and T =300 K then the photon pressure is 2.04 10^-6 Pa.
The only way to get the gas pressure and photon pressure to comparable values it to increase the temperature. The controlled empirical experiments* on the Casimir effect are not done at the temperatures of ~10⁵ K needed for this.

* = MM speak.