# Einstein was wrong?

1. Jun 17, 2007

### jonegil

what y'all think about that portuguese guy (joão magueijo) and his colleagues who have proposed that the speed of light has varied since the big bang (it has slowed down according to this new stream)...do you agree with this?

2. Jun 17, 2007

### Janus

Staff Emeritus
Even if c has varied over time, this would not make Einstein wrong. Special Relativity only requires that all observers measure the same relative speed for light regardless of their own relative motions, it doesn't matter whether that value has changed over time or not.

3. Jun 17, 2007

### G01

I don't think it means that Einstein was wrong. The universal speed limit is and always was the speed of light. It's just that the speed limit has changed since then.

4. Jun 17, 2007

### turbo

Einstein said that the speed of light in a vacuum can only be considered to be constant if you can ignore the effects of gravitation imposed by the matter embedded in the space under question. This is the thought experiment model that gave rise to Special Relativity. In his 1920 book on (S and G) relativity, he said that the speed of light in a vacuum must be variable in general relativity, to allow for the refractive effects predicted by that theory.

Look at Chapter 22 here:

http://www.bartleby.com/173/

Einstein may have been disastrously wrong on this point and if so, we may have to cede the mathematicians the field and agree that somehow the Universe knows how to obey his field equations. It's going to take a pretty big effort to press that point. Penrose says that GR and QT are both going to take some pretty big hits before a theory of quantum gravity can be formulated. I think that QT will skin by and GR will take some huge hits. If there is anybody here who feels that GR would have emerged in its present form if Einstein had been aware of the flat rotation curves of spiral galaxies or the excess lensing and binding forces of clusters, I ask you if such a pragmatic man would have postulated that the discrepancy was caused by invisible, unseeable, undetectable particles that only interacted gravitationally, instead of exploring the idea that Newton's gravitational constant might be a variable and not a constant?

Last edited: Jun 17, 2007
5. Jun 17, 2007

### pervect

Staff Emeritus
I agree that Joao has proposed theories with a "variable speed of light". They also meet PF guidelines for discussion, being published in peer reviewed journals.

However, these theories have not found any experimental confirmation (at least not any reproducible experimental confirmation) that I'm aware of.

The main benefit I see of Joao's theories is that his theories has prompted us to experimentally look at the possibility of the fine structure constant varying. (I must add that I may not be giving credit to other authors - I don't know if Joao is the first person to propose such a variation or not).

In any event, the current status as far as I'm aware is that experiment does not find any reproducible evidence for such a variation (i.e. for Joao's theories). See for instance

http://prola.aps.org/abstract/PRD/v64/i10/e103505

The thing that I dislike about Joao is his attempts at self promotion. In my personal opinion, here's no reason that a theory with no experimental support should be popularized in the lay press.

6. Jun 17, 2007

### pervect

Staff Emeritus
I should point out to readers who may not know any better that any local observer, using local clocks and rulers, will still measure the speed of light to be equal to 'c'. The above remarks only apply to the coordinate speed of light, something that was more popular to stress in Einstein's day than it is with the modern approach.

Ant this brings up a Pet peve: Einstein is not the only person doing physics, or even relativty. If relativity turns out to be wrong, it's not a case of "Einstein" being wrong, it's a case of Einstein, the National Bureau of standards, NIST, Clifford Will, Bradley, Airy, Michelson and Morley, Kennedy and Thorndike, Cialdea, Krisher, Champeny, Turner & Hill, DeSitter, Brecher, Alvaeger, Sadeh, Hughes-Drever, Prestage, Lamoreaux, Chupp, Phillips, Brillet and Hall, Haefle and Keating, Vessot, Alley, Bailey, Fizeau, Sagnac, Michelson and Gale, and many others being wrong too.

Furthermore, relativity has developed since Einstein's day, it's a mistake to stick one's head in the sand and ignore the more modern ways of looking at things because Einstein didn't happen to be the one who thought of looking at them that way.

7. Jun 17, 2007

### G01

Good Point....

I see. This is interesting stuff. I'm going to look into it.

Last edited by a moderator: Jun 17, 2007
8. Jun 17, 2007

### rbj

i agree with John Barrow http://en.wikipedia.org/wiki/Planck_units#Planck_units_and_the_invariant_scaling_of_nature and Michael Duff ( http://www.arxiv.org/abs/hep-th/0208093 and http://xxx.lanl.gov/abs/physics/0110060 ) and, i think, John Baez (can't find the link here) about it.

9. Jun 18, 2007

### jonegil

Michael Duff is related to string theory...the other two idk

10. Jun 18, 2007

### rewebster

'Is Einstein wrong?' is, to me, the same as asking, 'Is Newton wrong?'.

I don't know if Newton expressed any self-doubts, but even Einstein was humble enough to do so.

11. Jun 18, 2007

### pmb_phy

Einstein's speed of light postulate states that the speed of light is invariant. Einstein never said it was a constant in time, although he might have assumed it.

Pete

12. Jun 19, 2007

### rbj

John Barrow writes books. one book (where the quote in the Wikipedia article is taken) is called The Constants of Nature; from Alpha to Omega, the numbers that encode the deepest secrets of the universe. John Baez, besides being a cousin of the more well known singer Joan Baez, is a pretty well known physicist and prof at U.C. Riverside. all of these guys have biographies on the web, including at Wikipedia.

Duff doesn't use a spit of string theory to take issue with the VSL claims. it's much more fundamental than that. it's essentially that whatever Magueijo or Davis or Davies claim, the speed of light (or whatever ostensibly instantaneous action) is always 1 Planck length per Planck time and when we measure or perceive anything, any physical quantity, we are measuring a dimensionless quantity, like counting tick marks on a ruler. all we really know are the dimensionless quantities and those are the only quantities that matter, in the final analysis.

if you say, "see here, the number of meter sticks that light travels in a second has changed." (assuming we have reverted back to the pre-1960 definition of the meter), then i would say that either or both the number of Planck lengths per meter stick has changed and/or the number of Planck times per clock tick has changed. and it's those two dimensionless numbers that are the salient values. it all boils down to dimensionless parameters, and c nor G nor $\hbar$ nor $\epsilon_0$ are dimensionless numbers, so i can choose my units of length, time, mass, and charge so that those four constants can come out to be anything (real and positive) that i want. and nature does not give a rat's ass what system of units i choose to use.

it's not that the variation in dimensionful constants is wrong, it's not even wrong. the variation of dimensionful constants is not operationally meaningful. you may think that you have measured or perceived a change in some dimensionful parameter, but what really has changed is some dimensionless ratio of like dimensioned quantities. it's these dimensionless values that are perceivable and meaningful.

Last edited: Jun 19, 2007
13. Jun 19, 2007

### Voltage

For the record, turbo means this:

"In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)...."

14. Jun 19, 2007

### G01

History does tell us that eventually every theory is going to be replaced by one which is more "correct" in the sense that it covers more phenomena and more situations. I don't think this means the original theory was wrong, it just means that there is a range of validity to the theory.

15. Jun 19, 2007

### rewebster

Sort of....

Some (the main idea) are (may be)/were entirely wrong, and the newer one may just use 'some' of the info of the 'old' one---

Last edited: Jun 19, 2007
16. Jun 19, 2007

### jonegil

Popper expresses this very well on his books...a theory must be falsified...there are no "True and Permanent" theories...look at the example of earth...geocentric model...

17. Jun 19, 2007

### rewebster

I think there are some facets of some theories that will remain as permanent and will have some validity (adjusted for specific variables/new info).

18. Jun 19, 2007

### jonegil

Yes, the progress of science is based on that but it is like an asymptote..it will never reach the prefection

19. Jun 19, 2007

### rewebster

I guess that depends on your ideas of 'perfection' and the application that the specific facet is being used to calculate was is needed.

e.g.--And some think that Einstein is the one holding the dice.

Last edited: Jun 19, 2007
20. Jul 25, 2007

### Ruian

a theory is based on a postulates... that postulate probably be wrong or right... But we have to consider a theory to be true for a moment... and yes it might be replaced by another theory which is true or more true or more technically explained...