Five Brilliant Ideas For New Physics That Need To Die, Already

[swansont]

Good summary of five popular physics hypotheses that just haven't panned out

https://www.forbes.com/sites/startswithabang/2017/10/06/five-brilliant-ideas-for-new-physics-that-need-to-die-already/#13d3f59357b7

 

Plus the kicker at the end

Quote

[T]he best thing a new scientific theory can do is make predictions about what you can expect to observe in this Universe. When you go out there and look for it, that should be where the answer lies. If it isn't, either you made a mistake somewhere, or you should abandon your theory.

 

[Sensei]

Quote

Plenty of people complain that science is too monolithic, that it's a victim of "groupthink" and that people who come up with new ideas are routinely labeled as crackpots

Majority of crackpots that we have seen here were not educated in quantum physics at all..

Often even saying "wow" after the first time in their life seeing videos showing Cloud Chamber, that I gave, presenting result of radioactive decay, result of unstable quantum particle decay, on their own eyes..

 

[J.C.MacSwell]

"2.) Modified gravity: When you look at rotating galaxies...

 

...When we add dark matter, they all match. When we modify gravity, the modifications we need to make to solve one problem fail to solve the others. "

The problem here is that of course it would match...you get to assume it is exactly where needed without basing it on any observation but the observation you are hoping to resolve. Until that changes modified gravity needs to stay in the game, even if it is the lesser likelyhood.

Edited October 8, 2017 by J.C.MacSwell

[Strange]

Huh? The same amount of dark matter explains both galaxy clusters and galaxy rotation curves. It is also consistent with models of large structure formation, patterns in the CMB and various other things that I don't fully understand. 

And the density distribution of dark matter around galaxies matches both simulations of how dark matter behaves and the observed effects. 

[J.C.MacSwell]

3 minutes ago, Strange said:

Huh? The same amount of dark matter explains both galaxy clusters and galaxy rotation curves. It is also consistent with models of large structure formation, patterns in the CMB and various other things that I don't fully understand. 

And the density distribution of dark matter around galaxies matches both simulations of how dark matter behaves and the observed effects. 

I don't think that is correct. I think the amount, and positioning, that is required varies in different Galaxies.

If I'm wrong and the amount and position is consistent wrt ordinary matter in some way...why would a modified gravity function not fit just as well?

[swansont]

14 minutes ago, J.C.MacSwell said:

I don't think that is correct. I think the amount, and positioning, that is required varies in different Galaxies.

If I'm wrong and the amount and position is consistent wrt ordinary matter in some way...why would a modified gravity function not fit just as well?

Modified gravity typically matches just one behavior that deviates from dark-matter-free predictions. Dark matter matches all of them. That's the point the article is making.

 

[J.C.MacSwell]

6 minutes ago, swansont said:

Modified gravity typically matches just one behavior that deviates from dark-matter-free predictions. Dark matter matches all of them. That's the point the article is making.

 

Right. As I said in my earlier post, isn't it just assumed to be where needed? If say, you assumed it was where not needed it would not fit at all...so nothing really special about the fact that it matches...

...or am I missing something?

[swansont]

1 hour ago, J.C.MacSwell said:

Right. As I said in my earlier post, isn't it just assumed to be where needed? If say, you assumed it was where not needed it would not fit at all...so nothing really special about the fact that it matches...

...or am I missing something?

There are eight listed observations that requires some fix to make a match. You are not making eight different assumptions. There are no conflicts between the observations with the addition of dark matter. That's not the case with modified gravity.

[J.C.MacSwell]

19 minutes ago, swansont said:

There are eight listed observations that requires some fix to make a match. You are not making eight different assumptions. There are no conflicts between the observations with the addition of dark matter. That's not the case with modified gravity.

I thought it was more complicated than that, and it could be tough to find a fit for the dark matter in many cases. Not that the theory/hypothesis was ever proven wrong, but assumptions of the details in particular cases were very much subject to change as more observations were made.

[LaurieAG]

7 hours ago, swansont said:

Modified gravity typically matches just one behavior that deviates from dark-matter-free predictions. Dark matter matches all of them. That's the point the article is making.

And the ratio between all universal matter and all normal matter is 2 * Pi +/- 1.1 % according to the latest PLANCK data. 

So ((2*Pi) - 1) * normal matter = (dark matter) matches all the dark matter predictions on a universal scale without requiring any dark matter.

[druS]

 

 

Love this bloke. Way beyond me, took him several years to be able to talk down to my level, still. Does this lecture talk through this issue?

[Ignore me, if "no".]

[Strange]

10 hours ago, swansont said:

Modified gravity typically matches just one behavior that deviates from dark-matter-free predictions. Dark matter matches all of them. That's the point the article is making.

I see what you mean. The exact proportion of dark matter is different in some galaxies (as are the number of stars, for example). Some of that is as expected (e.g. less in young galaxies). But it is the "same" dark matter: it behaves the same way. And the overall amount is consistent with other evidence. 

That seems a lot less ad-hoc than saying "the law of gravity for this galaxy is given by equation 1; the the law of gravity for that galaxy is given by equation 2; the law of gravity for this cluster is given by equation 3; here the equation for gravitational lensing needs to be adjusted by this much; there the equation for gravitational lensing needs to be adjusted by this much"  and so on. ("And, by the way, we can't explain large structure formation; maybe gravity behaved completely differently in the early universe.")

[swansont]

5 hours ago, LaurieAG said:

And the ratio between all universal matter and all normal matter is 2 * Pi +/- 1.1 % according to the latest PLANCK data. 

So ((2*Pi) - 1) * normal matter = (dark matter) matches all the dark matter predictions on a universal scale without requiring any dark matter.

So having dark matter means you don't need dark matter? That makes no sense.

[J.C.MacSwell]

2 hours ago, Strange said:

 

That seems a lot less ad-hoc than saying "the law of gravity for this galaxy is given by equation 1; the the law of gravity for that galaxy is given by equation 2; the law of gravity for this cluster is given by equation 3; here the equation for gravitational lensing needs to be adjusted by this much; there the equation for gravitational lensing needs to be adjusted by this much"  and so on. ("And, by the way, we can't explain large structure formation; maybe gravity behaved completely differently in the early universe.")

I agree. But seems less ad hoc is still far from proof. It just means it seems more plausible at this time.

Some form of modified gravity is the second most likely explanation.

Why should all of science completely abandon it? A shared explanation between the two ideas is also a possibility.

 

Edited October 9, 2017 by J.C.MacSwell

[Strange]

2 minutes ago, J.C.MacSwell said:

Why should all of science completely abandon it?

I guess the author's point is that at some point you have to decide some particular line of enquiry isn't going to work (this is why the adage "absence of evidence is not evidence of absence" is not always true - after spending 6 months looking for unicorns in my garden and finding no trace, I think it is safe to conclude that they are not there.)

On the other hand, because people are stubborn and imaginative and curious, there will always be people looking for alternative explanations (even after we have identified what dark matter is).

[swansont]

4 minutes ago, J.C.MacSwell said:

I agree. But seems less ad hoc is still far from proof. It just means it seems more plausible at this time.

Some form of modified gravity is the second most likely explanation.

Why should all of science completely abandon it?

Because it fails. That's why we abandoned the Bohr and plum pudding models of the atom (and several more lesser-known ones), and phlogiston. 

[J.C.MacSwell]

1 hour ago, swansont said:

Because it fails. That's why we abandoned the Bohr and plum pudding models of the atom (and several more lesser-known ones), and phlogiston. 

Those are specific models. I'm not suggesting every line of inquiry for modified gravity should be kept open.

Certain lines of thought have been more or less shown to be inadequate. Modified gravity as a concept has not IMO. Proof of dark matter may put it to bed, but in the mean time it will no doubt remain open.

1 hour ago, Strange said:

I guess the author's point is that at some point you have to decide some particular line of enquiry isn't going to work (this is why the adage "absence of evidence is not evidence of absence" is not always true - after spending 6 months looking for unicorns in my garden and finding no trace, I think it is safe to conclude that they are not there.)

On the other hand, because people are stubborn and imaginative and curious, there will always be people looking for alternative explanations (even after we have identified what dark matter is).

We are not at that point yet.

[Strange]

12 minutes ago, J.C.MacSwell said:

We are not at that point yet.

Maybe English does need a future tense, after all.

 

[J.C.MacSwell]

1 minute ago, Strange said:

Maybe English does need a future tense, after all.

 

I think I read it as you intended...my point was implying that since we are not at that point it would be premature to give up on all attempts at modifying gravity. Obviously there are judgement calls to be made. A researcher has to have strong reasons to believe in the plausibility of it, not simply "lets see if we can find an equation that fits all the observations" (much of which is "noisy")

[Strange]

Indeed. And while there will always be some saying, "come on guys, let it go" there will always be others saying, "hang on, I just want to try this ..."

[LaurieAG]

16 hours ago, swansont said:

So having dark matter means you don't need dark matter? That makes no sense.

That's only if you don't actually have any dark matter at all and have missed a 2*Pi translation.

I wonder if you know what the difference between the lambda used in the Schrodinger/Dirac equation, the lambda used in E = m * c^2 and the lambda used in Lambda CDM?

https://en.wikipedia.org/wiki/Compton_wavelength#Relationship_between_the_reduced_and_non-reduced_Compton_wavelength

[Mordred]

Lambda has nothing to do with dark matter.

Lambda is used for the cosmological constant which dark energy is a possible contributor.

Dark energy and dark matter are two completely different entities, with completely different dynamics.

Edited October 10, 2017 by Mordred

[swansont]

21 hours ago, J.C.MacSwell said:

I think I read it as you intended...my point was implying that since we are not at that point it would be premature to give up on all attempts at modifying gravity. Obviously there are judgement calls to be made. A researcher has to have strong reasons to believe in the plausibility of it, not simply "lets see if we can find an equation that fits all the observations" (much of which is "noisy")

But we don't even have an equation that fits all the observations, using only normal matter. That's the problem. Equations that fit for one observation fail for others. 

[Strange]

22 hours ago, J.C.MacSwell said:

A researcher has to have strong reasons to believe in the plausibility of it, not simply "lets see if we can find an equation that fits all the observations" (much of which is "noisy")

Very few alternative gravity theories have an underlying principle beyond "curve-fitting".

[J.C.MacSwell]

3 hours ago, swansont said:

But we don't even have an equation that fits all the observations, using only normal matter. That's the problem. Equations that fit for one observation fail for others. 

Observations of normal matter are far from precise, and much of he accuracy is questionable. I think we know that it has to be dark matter or modifications to gravity theory since the discrepancies are so high. As we get more and better data some genius may recognize a pattern amidst the noise and then plausibly come up with a modified gravity approach, with or without dark or extra-normal matter...or maybe someone figures out what dark matter is and modified gravity is not required.

I understand the idea...not working, give it up already...I think that time might have come for many or most, but to suggest that physics as a whole should give up on it completely is IMO premature.

"We haven't succeeded yet" was true of every concept at one point in time, including ones that lead to current theories.