Dark Energy and Dark Matter in Question


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http://www.physorg.com/news/2011-10-supernovae-universe-expansion-understood-dark.html

"While the concept of light’s least-time path seems to be capable

of explaining the supernovae data in agreement with the rest of

our observations of the universe, Annila notes that it would be

even more appealing if this one theoretical concept could solve

a few problems at the same time. And it may – Annila shows

that, when gravitational lensing is analyzed with this concept,

it does not require dark matter to explain the results.

Einstein’s general theory of relativity predicts that massive objects,

such as galaxies, cause light to bend due to the way their gravity

distorts spacetime, and scientists have observed that this is exactly

what happens. The problem is that the deflection seems to be larger

than what all of the known (luminous) matter can account for,

prompting researchers to investigate the possibility of dark

(nonluminous) matter.

However, when Annila used Maupertuis’ principle of least action

to analyze how much a galaxy of a certain mass should deflect

passing light, he calculated the total deflection to be about five

times larger than the value given by general relativity. In other

words, the observed deflections require less mass than previously

thought, and it can be entirely accounted for by the known matter

in galaxies."

Dennis May

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It's safer to go with informed common sense when physicists go into wacky territory. Another example was this alleged "faster than light neutrino" thing that came out a while back.

Shayne

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It's safer to go with informed common sense when physicists go into wacky territory. Another example was this alleged "faster than light neutrino" thing that came out a while back.

Shayne

There was nothing "wacky": about what the OPERA group did. It was proper experimental physics, but even so an error in the timing may have crept in. The OPERA people did the proper thing and invited the physics community to either replicate their results or find the error in their experiment. It was good science, but possibly mistaken.

The developments in physics show that "commons sense" is a poor guide. According to common sense quantum physics cannot be right, but quantum electrodynamics predicts correctly to 12 decimal places. So much for "common sense". Einsteins theory of relativity was very much in opposition to common sense. The idea that the measure speed of light is independent of the speed of the observer or the source is very anti-intuitive. The consequence of Einstein's theory is that velocities do not add. In everyday life velocities are so close to adding we cannot readily see that this is not the case.

Most of Aristotle's physics is based on common sense and it is mostly dead wrong, as was found out much later on.

It was common sense to assume the earth stood still and the celestial bodies revolve around the earth. We cannot feel the motion of the earth and it is very difficult to measure the motion of the earth except indirectly with instruments. So the "common sense" idea that the earth stands still is quite mistaken.

Ba'al Chatzaf

Ba'al Chatzaf

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There's nothing in the predictions of QM or relativity that are contrary to informed common sense. Dark matter and faster than light interactions on the other hand do defy informed common sense, because they go into territory where they are just patching a problem with the most convenient fix, without a wider integration with other things.

Shayne

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It's safer to go with informed common sense when physicists go into wacky territory. Another example was this alleged "faster than light neutrino" thing that came out a while back.

http://www.wired.com/wiredscience/2011/10/mundane-explanations-neutrinos/

Among the most recent ideas is a paper invoking Einstein’s supposedly challenged theory of relativity. The OPERA team used GPS satellites to accurately measure the 730-km distance between their detector and the CERN beam where the neutrinos were produced. Yet, according to special relativity, calculations will be slightly different when two observers are moving relative to one another.

Since the satellites were zipping around the Earth, the positions of the neutrino source and the detector changed. According to the paper, the movement would account for a 64 nanoseconds discrepancy, nearly exactly what the OPERA team observes.

http://arxiv.org/abs/1110.2685

Michelson and Morley showed that an interference pattern is reference-frame independent. However, the distance between a particle's production and detection site is reference-frame dependent due to Lorentz contraction and detector movement. For the OPERA experiment detector movement in the satellite reference frame leads to corrections which can account for most of the $\pm 60$ ns discrepancy between expected and observed time of flight.

______

J.S. Bell once posed a Special Relativity puzzler to this colleagues at CERN. Virtually all of them got the wrong answer.

Dennis May

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There's nothing in the predictions of QM or relativity that are contrary to informed common sense. Dark matter and faster than light interactions on the other hand do defy informed common sense, because they go into territory where they are just patching a problem with the most convenient fix, without a wider integration with other things.

Shayne

The dark matter hypothesis responds to the anomalous motion curves of stars at the periphery of galaxies. They move much faster than they would if their motion was governed by the gravitational interaction with visible bodies (stars and gas).

Either there is something like dark matter or our gravitational theories are really badly mistaken. That is a possibility. But both Einstein's theory and Newton's theory are well supported by observation (which is not proof that they are correct). So the question comes down to which is the better way to account for the strange motion of stars at the periphery of galaxies. More needs to be known. There are several candidates for matter that exerts a gravitational influence but cannot be "seen" (by way of electromagnetic radiation). Perhaps "super particles", maybe. We already have an instance of matter that is very difficult to detect. The neutrino. Neutrinos were postulated to save the conservation laws. It took something like thirty years to actually observe them and even that by very sophisticate and indirect means.

Dark Energy is a place holder for ignorance. No one knows why the expansion of the cosmos has sped up. More needs to be found out. Stay tuned. Mysteries like the accelerated expansion of the cosmos is what makes physics interesting. Never a dull moment and never has the Last Word been uttered.

Ba'al Chatzaf

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...faster than light interactions on the other hand do defy informed common sense...

Shayne

In quantum mechanics you have to give up the speed of light or you

have to give up causality in one form or another. I say keep causality.

Dennis May

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...faster than light interactions on the other hand do defy informed common sense...

Shayne

In quantum mechanics you have to give up the speed of light or you

have to give up causality in one form or another. I say keep causality.

Dennis May

Some day we may have a drop dead causal theory. But that day has not yet arrived. Bohm Debroigle collides with relativity. Not good.

In physics, experience has taught us philosophical purity is worth jack-shit. The most one can ask for is internal consistency and conformity to observed fact. Aristotle was philosophically pure. His physics was either dead wrong or worse, not even wrong.

Ba'al Chatzaf

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...faster than light interactions on the other hand do defy informed common sense...

Shayne

In quantum mechanics you have to give up the speed of light or you

have to give up causality in one form or another. I say keep causality.

Dennis May

I think you may be pushing the theories too hard. Under Newtonian physics, gravity travels instantaneously, but that's merely an artifact of abstraction, not a metaphysical statement, or at least that's how I view it.

Shayne

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...faster than light interactions on the other hand do defy informed common sense...

Shayne

In quantum mechanics you have to give up the speed of light or you

have to give up causality in one form or another. I say keep causality.

Dennis May

Bohm Debroigle collides with relativity. Not good.

Ba'al Chatzaf

Special and General relativity collide with indeterministic QM. Not good.

de Broglie-Bohm QM can be reconciled with a form of LET relativity which

is mathematically indistinquishable from Einstein's Special Relativity. There

is no reconciling deterministic relativity with indeterministic QM.

Dennis May

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de Broglie-Bohm QM can be reconciled with a form of LET relativity which

is mathematically indistinquishable from Einstein's Special Relativity. There

is no reconciling deterministic relativity with indeterministic QM.

Dennis May

Do you lust after aether? My goodness!

ruveyn

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