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Lambda-CDM theory - Woo or not?

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[pedantic]

I'm sure you mean "the entire observable universe" ...

By definition, any part of the universe (should such a thing exist) which is not observable - even in principle - is unconstrained, empirically.

Of course, one can develop any manner of laws, theories, models, hypotheses, speculations, guesses, and so on, about parts of the universe which are not observable ...

[/pedantic]

Whatever. I'm still blown away by the notion that you think the whole universe has no energy or that gravity has "negative energy". What the hell *is* negative energy? You have a universe *full* of energy all around you. Wake up and smell the coffee. Guth's free lunch theory is pure baloney.

The laws of conservation of energy *insist* that the energy inside this universe was neither created nor destroyed in any event. Period. Gravity is not "negative energy" and it never will be. There is a direct correlation between mass and energy and the universe is full of both.
 
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I remember talking about gravity being negative energy a looong time ago in school, and not even in the context of GR!

Correct me if I'm wrong but isn't the equation U = -GMm/r?

Put the radius to infinity (for zero gravity when things are infinitely far away). Anything closer is negative.
 
I remember talking about gravity being negative energy a looong time ago in school, and not even in the context of GR!

Correct me if I'm wrong but isn't the equation U = -GMm/r?

Put the radius to infinity (for zero gravity when things are infinitely far away). Anything closer is negative.

E=MC^2. Gravity is something that is "caused by" the existence and/or presence of mass. Mass is "stored" *positive* energy. Gravity isn't "negative energy", it's just gravity, and it won't overcome or cancel out the energy inside that mass. An easy example is a universe composed of a single hydrogen bomb. When we set it off, the *stored energy* is "released" from the mass, and the little bit of "gravity' caused by the mass will in no way "cancel out' or stop that energy from releasing itself into our simplified universe. There is simply energy in the system that is stored in the mass that is released in the event. The energy was not created or destroyed, it always existed and simply changed forms. The gravity is simply a function of mass it does not "cancel out" the energy.

Even in sol's example all we have is positive "potential energy" between two objects and that is turned into positive "kinetic energy". There was always *positive energy* in the system. There is nothing "negative" about that energy either. It is just positive potential energy that is being turned into positive kinetic energy. You can see that process play out over and over in an ordinary pendulum.
 
DeiRenDopa said:
This may have been posted earlier, but in case it hasn't ...

TASI Lectures on Inflation, by William H. Kinney (link is to the arXiv preprint); I think the abstract is worth copying:

Have you read this, MM?
Can't say I have.

If so, what say you?

So far all I can say is that it looks "long". :)
Well, it's not even 10% as long as the Birkeland document! :p

Anyway, when you've read it - the key parts at least - I'd be curious to know if you still have objections to inflation and DE as fierce as those you've stridently asserted in so many posts.

If so, I'd be particularly interested to learn why, if cosmology = application of GR+MHD+other physics that's been demonstrated to work. You see, that document makes a pretty darn good case that both inflation and DE (of the lambda kind) are nothing more than precisely what your definition of cosmology is.

Oh, and BTW, from ref 6 (link is to arXiv preprint abstract) in that paper, I learned that Guth was by no means the first to come up with the concept of inflation, and that his initial idea ("scenario") "did not work". May I infer then that you regard Linde, Chibisov, Starobinsky, Mukhanov, ... in equally low regard as Guth? And that you reject 'inflation' at least in part because of their sinful/evil/bad/whatever* characters?

ETA: FWIW, your recent posts about negative energy are quite surreal, if one is to take you at your word about accepting GR ...

* you didn't answer my question on why inflation was unacceptable because of some character flaw of Guth's.
 
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Special relativity. Which ignores gravity.

Gravity isn't "negative energy", it's just gravity

That's like saying electricity isn't "positive energy", it's just electricity. Well, yes: but an electric field has an associated potential energy, which is positive. And gravity has an associated potential energy, which is negative. I've already explained why it makes the most sense to define it as negative.

Even in sol's example all we have is positive "potential energy" between two objects and that is turned into positive "kinetic energy".

Oh, you can define energy that way. But GR has a preference for NOT doing it that way, because you need to make your equations more complicated if you do. Classically, it makes no difference if you define gravitational potential as being positive or negative, but even there you will find that most physicists have a preference for defining it as always negative because it's actually simpler to do so (your zero reference is easier to determine). In GR, though, it does make a difference to the equations themselves, because gravity is affected by all forms of energy, including gravitational energy. Again, this is standard GR, and you're failing it badly.
 
E=MC^2. Gravity is something that is "caused by" the existence and/or presence of mass. Mass is "stored" *positive* energy. Gravity isn't "negative energy", it's just gravity, and it won't overcome or cancel out the energy inside that mass. An easy example is a universe composed of a single hydrogen bomb. When we set it off, the *stored energy* is "released" from the mass, and the little bit of "gravity' caused by the mass will in no way "cancel out' or stop that energy from releasing itself into our simplified universe. There is simply energy in the system that is stored in the mass that is released in the event. The energy was not created or destroyed, it always existed and simply changed forms. The gravity is simply a function of mass it does not "cancel out" the energy.

Even in sol's example all we have is positive "potential energy" between two objects and that is turned into positive "kinetic energy". There was always *positive energy* in the system. There is nothing "negative" about that energy either. It is just positive potential energy that is being turned into positive kinetic energy. You can see that process play out over and over in an ordinary pendulum.

You really have no idea what you're talking about.

First of all, in pre-GR physics the total energy of a system is a completely meaningless quantity. All that matters are energy differences - you can add or subtract any constant from all energies without affecting physics in any way, and since energy is conserved you can therefore always make the total energy of any closed system zero by simply adding the right constant.

There is nothing mysterious about negative energy in any pre-GR context - and in fact in any classical theory with point masses or point charges it is impossible to make all energies positive (because the gravitational or EM binding energy can be arbitrarily negative).

In GR there is a meaning to total energy. But because energy is conjugate to time, and because GR is reparametrization invariant, there is a constraint in GR (called the Hamiltonian constraint) which sets the total energy to zero on any solution to the equations of motion. As I said, there are ways of defining a non-zero energy (for example, to get E=Mc^2 for your hydrogen bomb) but the involve separating the positive "matter" piece of the energy from the negative gravitational piece.
 
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Correct me if I'm wrong but isn't the equation U = -GMm/r?

You are correct (classically, anyways). This takes the reference of infinite separation as being zero energy, which is really the most sensible choice. If you try to set the other end (r=0) as being zero potential, all non-zero r's have infinite potential, and any other choice of a reference depends upon a choice of a specific r, which is necessarily arbitrary and may not even be very useful. So classically, U is always negative for simplicity. In GR, the reasons run a little deeper. But it's absolutely wrong to conclude, as Michael apparently does, that gravitational potential energy must be positive.
 
[...]

Well, lets see what they have planned:
A. Prospective Additional Probes of Dark Energy

1. Galaxy Clusters (Number Density, Clustering and Their Evolution) The abundance and clustering of galaxy clusters is another promising technique, and has previously been considered by the DETF [12]. There are many means of identifying and measuring galaxy clusters; the main source of uncertainty in future applications of this method will be in determining the relation of the selection function and observables to the underlying mass of the clusters.

Nope. It sounds like another "point at the sky and add math" exercises and it sounds pretty darn wasteful IMO. Nobody can empirically verify any of the presumed properties of "dark energy" by looking at the sky anymore than this can be done with "inflation". You're just fudging the numbers of mythical entities to fit observation and not you'd like to waste my tax payer money on *another* point at the sky routine with *zip* in the way of a real *control mechanism*.
Just so that I don't misunderstand ...

You seem to be saying that it is impossible, under any circumstances whatsoever, for something to be discovered 'in nature' from astronomical observations which later - maybe even decades or centuries later - becomes testable/verifiable/whatever in labs in controlled experiments; are you? And irrespective of whether a direct line from the astronomical observations to the controlled experiments can be established or not?

To make this concrete: at least one element (helium) was first discovered in the spectrum of the Sun; later - ~a quarter of a century later - it was found in rocks here on Earth. By your criteria for assessing (astrophysics, in this case) scientific woo, helium did not exist until 1895, and all scientific work - by astronomers, chemists, geologists, etc - until then, on helium, should have received no MM-approved funding, as it would have been a clear-cut case of woo.

Did I get it right?

If you and a team had this much money at your disposal, how would you suggest it be spent, MM? Non-negotiable requirement: the money must be spent on research into "Dark Energy".

I'd invest my money in PC/EU theory research and help you explain solar wind acceleration and coronal loops and stuff that has an affect on us here on Earth. Once you finally "get it" that EM fields exist in space, it probably wouldn't be much of a leap of faith to assume that any "acceleration" of a mostly plasma universe would be due to EM fields rather than some mythical fudge factor you stuffed into inflation theory to keep it alive.

Honestly, that has to be the most pointless waste of money I can think of, and in this economy it irks me that you would *waste* my tax money like that and try to pass it off as an "experiment". There are no control mechanisms. How about doing something *USEFUL* with my money like explaining solar wind acceleration? Birkeland could set you straight of course, but then *you* would have to do some reading.
Okey, dokey, ...

Follow-on question then: do I understand that you are completely and totally convinced that the only possible explanation/accounting of the various "DE" observations is "EM fields" or "electricity" or "electrical discharges" (or some such thing)? That it is utterly impossible for the "DE" observations to turn out to be some subtle combination of selection effects, stellar evolution, misapplication of GR, and downright bad luck (to make up one example)?

Further, that, in the unlikely event that a full appreciation of the nature of DE, obtained by research such as that described in the paper, leads - directly or indirectly - to something really, really, really useful (a way to greatly improve the efficiency of fusion reactors perhaps), you will still declare the research to have been "the most pointless waste of money I can think of"?
 
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Well, it's not even 10% as long as the Birkeland document! :p

True. :) Then again, you folks have thrown a lot of papers my way this month.

Anyway, when you've read it - the key parts at least - I'd be curious to know if you still have objections to inflation and DE as fierce as those you've stridently asserted in so many posts.

It probably won't be today at work. :)

If so, I'd be particularly interested to learn why, if cosmology = application of GR+MHD+other physics that's been demonstrated to work. You see, that document makes a pretty darn good case that both inflation and DE (of the lambda kind) are nothing more than precisely what your definition of cosmology is.

That's not the case here. Inflation and DE have not been demonstrated. I have no logical objections to you stuffing MDH theory into Lambda because I know EM fields exist in nature. DE is not identified nor does it exist in nature. It's therefore pointless to stuff it into a GR formula.

Oh, and BTW, from ref 6 (link is to arXiv preprint abstract) in that paper, I learned that Guth was by no means the first to come up with the concept of inflation, and that his initial idea ("scenario") "did not work". May I infer then that you regard Linde, Chibisov, Starobinsky, Mukhanov, ... in equally low regard as Guth? And that you reject 'inflation' at least in part because of their sinful/evil/bad/whatever* characters?

I'll have to read your link on the other names related to inflation. I'm aware of Linde's work, and yes I'm still very unimpressed with inflation. The other authors I can't much speak for as I have not seen them try to justify their ideas.

ETA: FWIW, your recent posts about negative energy are quite surreal, if one is to take you at your word about accepting GR ...

What I've come to realize in these conversations is that what your side calls "GR" is often stuffed with all sorts of metaphysics like inflation. I've read the free lunch theory. It's nonsense.

* you didn't answer my question on why inflation was unacceptable because of some character flaw of Guth's.
I *absolutely* do not blame Guth (et. all) for having an imagination or for writing about his/their ideas. I blame your industry for being so damn gullible and so arrogant. There is no "free lunch". I have never met Alan Guth. I"m sure he's a very nice guy. It has nothing to do with Guth's character it's his *ideas* I don't much care for. What I ultimately resent most however is this attitude that it is "better than" any other cosmology theory. It's not "better than" EU/PC theory because Lambda theory is completely "fabricated". EU/PC theory made real "predictions" from real experiments with real control mechanisms starting with Birkeland. He understood things that your whole industry still hasn't figured out 100 years later because they spend all their time *not* doing actual *science* but instead they point at the sky with math and play "make believe" with inflation faeries and dark evil energy. I want my tax dollars to be spent on something related to actual "science" with real "experiments" and real "control mechanisms". I want you folks to figure out solar wind and coronal loops before you start wasting money postdicting a dark energy gnome.
 
Special relativity. Which ignores gravity.

It does not "ignore gravity".

That's like saying electricity isn't "positive energy", it's just electricity.

No, it's like saying "electricity isn't "negative energy" it's just positive energy.

And gravity has an associated potential energy, which is negative.

The term "negative' is purely arbitrary. There is "positive" potential energy at the top of the pendulum cycle that is converted into *positive* kinetic energy at the bottom and then turned back into POSITIVE potential energy again. There's nothing 'negative' about this energy at any point in the process. That kinetic energy in the pendulum at the bottom of the cycle is *positive kinetic energy*. Potential energy is *positive energy* that I can release and convert to kinetic energy by letting go of the pendulum.
 
You really have no idea what you're talking about.

You spend more time "posturing" than anyone I've ever met in cyberspace.

First of all, in pre-GR physics the total energy of a system is a completely meaningless quantity.

BS. This is how I know that you're making this all up. You can in fact add and subtract and play with constants and do anything you want with the math. In the real world however *physics* matters and that is how I know your are whistling dixie on this topic. The universe is *FILLED WITH* energy. It has always had a positive energy density. In the world of actual "physics", physical particles contain and convey energy, real *positive* energy. You can't tell math from empirical physics.
 
There's no empirical difference between inflation and invisible unicorns. I can't falsify either one, particularly based on a math formula you slapped to it's forehead. They don't empirically exist in nature, so stuffing either one of them into a math formula is utterly absurd.

Really how do Invisible Pink Unicorns offer an explanation for the distribution, density of matter as well as the curvature of the universe?

No theory exists emprically in nature, you are still that sophmoric, can you show me an electron?

No you can't. You can only show effects consistent with the model of an electron.
 
Whatever. I'm still blown away by the notion that you think the whole universe has no energy or that gravity has "negative energy". What the hell *is* negative energy? You have a universe *full* of energy all around you. Wake up and smell the coffee. Guth's free lunch theory is pure baloney.

The laws of conservation of energy *insist* that the energy inside this universe was neither created nor destroyed in any event. Period. Gravity is not "negative energy" and it never will be. There is a direct correlation between mass and energy and the universe is full of both.

So again you kust pick and choose the words you like and you refuse to learn.

Gravity is a negative energy, wether you agree or not that is the common idiom. But please since your theories are worthless keep pretending that you know something.

Answer the question, what makes two objects with inertial mass atracted to each other?
(I agree that the nomenclature of negative energy is counter intuitive.)
 
Hmm... "repayment terms". I'll have to think about how to answer that.

There isn't really any matter at the "start" of the universe. Go back far enough and everything is radiation

Shameless bump.:D
Looking forward to the result of your thought on this.

2nd bit.
What is the source of the radiation?
I thought radiation required unstable matter?
Perhaps I am taking the equivalence of energy and matter to far?
I really don't know, I have not studied the main or fringe stream.
 
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You spend more time "posturing" than anyone I've ever met in cyberspace.

Take a look in the mirror.

BS. This is how I know that you're making this all up. You can in fact add and subtract and play with constants and do anything you want with the math. In the real world however *physics* matters and that is how I know your are whistling dixie on this topic. The universe is *FILLED WITH* energy. It has always had a positive energy density. In the world of actual "physics", physical particles contain and convey energy, real *positive* energy. You can't tell math from empirical physics.

Like most cranks you use technical words incorrectly. "Energy" has a specific meaning in physics, one which doesn't correspond to your vague, quackulent notions.

This is really basic stuff. In most countries 16 year-olds learn why and how gravitational energy is negative.
 
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Shameless bump.:D
Looking forward to the result of your thought on this.

Well.... it's not really that the energy is "borrowed". When two things fall together from their gravitational attraction, they gain kinetic energy - and at the same the gravitational energy becomes larger in magnitude (more negative).

Inflation is kind of like that - if you want to think of the space as expanding, the gain in kinetic energy as the objects increase in speed is compensated for by an increasingly negative gravitational potential.

But all this is really very awkward language, and not the best way to think about it.

2nd bit.
What is the source of the radiation?

Heat.

I thought radiation required unstable matter?

You're thinking of radioactivity. All objects (at non-zero temperature) radiate EM radiation, unstable or not.
 
I hear ya.


There's no empirical difference between inflation and invisible unicorns. I can't falsify either one, particularly based on a math formula you slapped to it's forehead. They don't empirically exist in nature, so stuffing either one of them into a math formula is utterly absurd.

You obviously don't hear me since you are again saying it is me doing things I haven't done... again.
 
It does not "ignore gravity".

Yes it does. And rather explicitly so. That's rather the whole point of the distinction between special relativity and general relativity: special relativity is what you get in a gravity-free environment. If gravity is weak enough, you can work the mechanics as if it didn't exist, but special relativity does not deal with gravity. That's why it's special relativity and not general relativity: the gravity-free case is a special case.

No, it's like saying "electricity isn't "negative energy" it's just positive energy.

Not at all. When the volume integral of the electric field squared increases, our potential energy has increased. When the volume integral of the gravitational field squared increases, our potential energy has decreased. And that is true regardless of where you want to put your zero. Ergo, gravitational fields carry negative potential energy, and electric fields carry positive potential energy.

The term "negative' is purely arbitrary.

In Newtonian mechanics, yes. In GR, no.

There is "positive" potential energy at the top of the pendulum cycle that is converted into *positive* kinetic energy at the bottom and then turned back into POSITIVE potential energy again.

Your assignment of positive potential energy is itself arbitrary. What's wrong with having negative potentials? Nothing. In Newtonian mechanics, all that ever matters is the difference, and that's the same whether the absolute value of the potential is positive or negative. Your cluelessness apparently extends to Newtonian physics as well.

That kinetic energy in the pendulum at the bottom of the cycle is *positive kinetic energy*. Potential energy is *positive energy* that I can release and convert to kinetic energy by letting go of the pendulum.

The second statement doesn't follow from the first. There's no reason we can't go from negative potential to more negative potential to produce positive kinetic energy. This is freshman physics that you're now failing.
 
This is really basic stuff. In most countries 16 year-olds learn why and how gravitational energy is negative.
I guess you feel the need to brainwash them early on eh? The "real" universe (the physical one) is *full* of energy. In the real world of empirical physics, there is no "dark evil energy", or inflation. These are figments of your wild imagination, along with your belief that an accelerating galaxy has zero energy. Hoy, what a weird and self conflicted cult.
 
Really how do Invisible Pink Unicorns offer an explanation for the distribution, density of matter as well as the curvature of the universe?

They steal your inflation and dark energy math and laugh at your silly questions. :)

No theory exists emprically in nature, you are still that sophmoric, can you show me an electron?

http://www.sciencedaily.com/releases/2008/02/080222095358.htm

No you can't. You can only show effects consistent with the model of an electron.

The difference is that electrons are real, they exist today, and they show up in controlled experiments, unlike deceased hairy inflation.
tongue.gif
 
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