Scientists say dark matter doesn't exist

[sol invictus]

Michael Disney, September-October 2007 issue, Volume 95, American Scientist

Sounds like a classic curmudgeon (see my definition above).

The logic is incomprehensible. First of all, it's completely false to claim that there are more free parameters than observations. There are an enormous number of observations, all consistent with the model. The fact that not all parameters have been determined so far is an invalid reason to reject the model.

Let me give an example. Suppose you went to sleep one night, and upon waking the next morning you noticed a bucket in your yard (which had been empty the night before) was half full of water. One theory is that it rained during the night. That rain theory makes many predictions, such as that all buckets in all yards will be full to the same height, no matter how big they are, and that the grass will be wet, etc.

But then Mr. Disney comes along and says, even though all the buckets are full to the same level and the grass is wet etc. the theory is garbage, because it can't differentiate between a heavy rain over a short time and a light rain over a long time (which both fill the bucket halfway).

It's a totally nonsensical objection. There are thousands of observations that agree with the predictions of the cosmological concordance model, and the fact that not all parameters have so far been determined is not a valid objection.

A valid objection would be if there is a competing theory that fits the data equally well but with fewer parameters. No such theory exists.

 

[jimgerrish]

What is not being taken into account is the effect of the expansion (or perhaps you prefer inflation) of space/time at the sub-atomic level. It requires a new math and that is not forthcoming until this becomes an accepted possibility. I know I will not live to see it happen.

 

[sol invictus]

What is not being taken into account is the effect of the expansion (or perhaps you prefer inflation) of space/time at the sub-atomic level. It requires a new math and that is not forthcoming until this becomes an accepted possibility. I know I will not live to see it happen.

Space/time does not have an atomic structure so far as we know, nor is there any need to posit one, so I'm not sure what you're talking about.

If you're thinking of quantum gravity, the only theory we have for that is string theory, and standard expanding universe cosmology is fully consistent with it.

 

[Hellbound]

Space/time does not have an atomic structure so far as we know, nor is there any need to posit one, so I'm not sure what you're talking about.

If you're thinking of quantum gravity, the only theory we have for that is string theory, and standard expanding universe cosmology is fully consistent with it.

Well, there's loop quantum gravity, but I admit to not being any more familiar with that than knowing it's name. My understanding, however, was that it isn't a traditional superstring theory?

 

[sol invictus]

I am familiar with it. You're correct that it's not a string theory.

It's not a theory of quantum gravity at all (at least as far as anyone knows). The definition of a quantum theory of something is, in part, that it contains a parameter (Planck's constant), and in the limit that parameter goes to zero, classical physics is recovered (in this case that would be the classical theory of gravity, general relativity). That guarantees among other things that the theory would correctly describe the motion of the planets, gravity on earth, the universe, etc.

The only quantum theory with that feature is string theory.

 

[Matt the Poet]

Thank matter for cosmic variance .

Top blog!

 

[Schneibster]

Nice, Matt; an important point: we are now aware of evidence that requires that a modified gravity theory cause a force pointing to where there is no matter we can see, to account for observations in hand. In other words, gravity from nothing is the only alternative to dark matter. Forces from nothing make me a LOT more nervous than matter I can't see; there's lots of matter I can't see, and no forces from nothing.

 

[Hellbound]

sol:

Thanks for the info...I keep meaning to look for some info on QLG, but I'm not a professional (which means when there's too much math I'm out) and it's hard to "weigh" layman-oriented sources for accuracy. Any suggestions that would cover current theories?

 

[jimgerrish]

Originally Posted by jimgerrish
What is not being taken into account is the effect of the expansion (or perhaps you prefer inflation) of space/time at the sub-atomic level. It requires a new math and that is not forthcoming until this becomes an accepted possibility. I know I will not live to see it happen.

Response by Sol_Invictus:
Space/time does not have an atomic structure so far as we know, nor is there any need to posit one, so I'm not sure what you're talking about.

What is in denial by most physicists, and your response by implication, is that the universal expansion of space/time has an EFFECT at the sub-atomic level. Not a structure, but an effect. A local effect, not just a "far off in a distant galaxy" effect. The most observable evidence of this expansion is what we refer to as "the passage of time," because we humans like to separate time from space as a more convenient way of thinking about it.

 

[sol invictus]

Thanks for the info...I keep meaning to look for some info on QLG, but I'm not a professional (which means when there's too much math I'm out) and it's hard to "weigh" layman-oriented sources for accuracy. Any suggestions that would cover current theories?

Unfortunately I don't know of a popular book or article that lays out the situation with any clarity. The group of people working on loop gravity is really quite small, largely for the reason I stated above - it has yet to demonstrate any significant success. If it ever does, there will be a sudden rush of people into the field (as happened with string theory in the 1980s). For the moment it remains a fringe idea.

What is in denial by most physicists, and your response by implication, is that the universal expansion of space/time has an EFFECT at the sub-atomic level. Not a structure, but an effect. A local effect, not just a "far off in a distant galaxy" effect. The most observable evidence of this expansion is what we refer to as "the passage of time," because we humans like to separate time from space as a more convenient way of thinking about it.

Well, we have a theory which fits all observations we've ever made, in which there is no such effect. Actually it's stronger than that - all fundamental theories we know of, including those of particle physics, respect an exact (as far as we can tell now) symmetry that prohibits the effect you believe in.

When you come up with a theory which exhibits that effect AND fits all observations from cosmology to the anomalous magnetic dipole moment of the electron to 12 decimal places, you'll have something to say.

 

[Dancing David]

What is in denial by most physicists, and your response by implication, is that the universal expansion of space/time has an EFFECT at the sub-atomic level. Not a structure, but an effect. A local effect, not just a "far off in a distant galaxy" effect. The most observable evidence of this expansion is what we refer to as "the passage of time," because we humans like to separate time from space as a more convenient way of thinking about it.

Um, what data are people in denial of. Even if space/time was not expanding we would have 'time'.

 

[jimgerrish]

Um, what data are people in denial of. Even if space/time was not expanding we would have 'time'.

No, we have 'time', it is true, but it is accepted as 'just there' with no explanation for our "passage through it from past to future." The theory of expansion of space/time gives us that explanation and shows why we pass through it in one direction only, among other things.

 

[jimgerrish]

Well, we have a theory which fits all observations we've ever made, in which there is no such effect. Actually it's stronger than that - all fundamental theories we know of, including those of particle physics, respect an exact (as far as we can tell now) symmetry that prohibits the effect you believe in.

When you come up with a theory which exhibits that effect AND fits all observations from cosmology to the anomalous magnetic dipole moment of the electron to 12 decimal places, you'll have something to say.

After stating "we have a theory which fits all observations we've ever made, in which there is no such effect" it is good of you to concede that we do not yet have a "Theory of Everything" which takes into account all observations from cosmology as well as all anomalies that have not yet been explained. To ask me to come up with such a theory of everything on my own FIRST before I will have something of value to say, denies the whole history of science in which most great theories spring from tiny breakthroughs rather than grand leaps of the imagination. I offer a tiny breakthrough. Tied to the Planck Constant, so it must be tiny.

 

[sol invictus]

...it is good of you to concede that we do not yet have a "Theory of Everything" which takes into account all observations from cosmology as well as all anomalies that have not yet been explained.

I'm sorry, but where did I concede that?

Before trying to revolutionize physics you might want to learn a few basic facts about it. The anomalous magnetic moment of the electron can be calculated to extreme accuracy - more than ten significant figures - and agrees precisely with experiment. It is one of the most accurate predictions in the history of science, and an extremely non-trivial one (the calculation is very difficult and requires carefully taking into account many, many corrections). An effect of the type you posit would destroy this result (which is based on Lorentz invariance).

FYI, the term "anomalous" in this context does not refer to an effect that can't be explained by the current theory, but rather an effect that couldn't be explained by its predecessor (non-relativistic quantum mechanics).

No, we have 'time', it is true, but it is accepted as 'just there' with no explanation for our "passage through it from past to future." The theory of expansion of space/time gives us that explanation and shows why we pass through it in one direction only, among other things.

Not so. Any system which begins in a state of low entropy has a direction of time, regardless of whether or not the spacetime it exists in is expanding. Our universe began (for some reason we don't know) in such a state; hence our existence and the arrow of time.

 

[jimgerrish]

Expansion of space/time is hardly a revolutionary theory and rather than destroying the magnetic dipole moment of the electron merely needs to be considered as another variable to be taken into account. Sorry if it makes the calculation even more difficult and adds one more correction, but this should be undertaken by someone with an open mind who does not feel threatened by new ideas. I had hoped that the reward for undertaking such a gargantuan effort would be an understanding of why dark matter does not need to exist, which is why I posted here in the first place, but I can see that this is not the forum to discuss it. Feel free to resume your discussions.