Do universal constants change slightly over time? - Page 1
Forum section: electronics / general

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: July 30, 2017, 08:00:48 am
content: Perhaps should be in Metrology section but thought it was more of general interest:https://www.youtube.com/watch?v=1TerTgDEgUE&feature=youtu.be&t=590If this is correct then it's a bombshell for science. It would be interesting to see the historical data for c, G etc. and confirm these findings.When you think about it, the speed of light is not hard to measure accurately so why should there be such changes in the reported value?Air density has a small effect (if not measured in vacuum) but I imagine the metrologists would allow for that. As there have been laser reflectors on the Moon since the '70s it should not be hard to make a measurement over a longer distance which is mostly vacuum, anyway.

author: awallin
author_rank: Frequent Contributor
timestamp: July 30, 2017, 08:51:02 am
content: as far as people can measure, most papers report changes that are consistent with zero change over time.the recent experiments have relative errors in the 1e-17 per year range (roughly: 16 digits are the same, and there might be a change in the 17th digit of the number during one year).https://physics.aps.org/articles/v7/117this is for the fine-structure constant and the electron-to-proton mass ratio. Please do link to papers on c and G changes if you know about them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 30, 2017, 09:09:46 am
content: There are no constants, that have been known to enough decimal places, for long enough time, to be at all representative, say on cosmological scales.There is certainly no reason to believe anything should change rapidly (say over years or decades).Some speculate about billions of years. On cosmological scales, if constants might vary by time, or by space, we should be able to see gross changes at enormous distances (inferring constants from admittedly similarly gross processes, like stellar evolution). But there's no evidence of that either.Some constants have been historically very difficult to measure, being related to messy thermodynamic processes, or easily skewed by distributions of matter or energy. G and k_B have these downsides. Gravity is very difficult to measure accurately; the acceleration due to the Earth beneath your feet varies by parts per thousand as you go between hill and valley, between light ocean water or dense granite. That variation must be controlled first.Another thing about units might blow your mind. The speed of light cannot vary, because, by definition, it is fixed. It seems intuitively odd that a speed (which one might consider just another open variable) might be fixed! But suppose such a definition is made, yet the real value varies. What then must happen? The defined value of time or distance would change. This trick can be played with any number of constants; in Planck units, everything is normalized to 1.0 exactly! The downside is, any theoretical result within that unit system is imperfectly representable in customary units. The conversion factors -- the scale -- become the unknowns.Tim

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 30, 2017, 09:38:08 am
content: Quote from: IanMacdonald on July 30, 2017, 08:00:48 amPhysicists always search for changes in defined Constants of Nature, and also still do experiments to question their invariance over time.Even if many constants have now a fixed value (zero uncertainty), they can anyway experimentally checked for invariance.Long term changes, or small disagreements in this system would indicate new physical effects, which are not known up to date.That barefoot layman in this video is talking complete bullshit. Simply a horrible, pseudo - scientific video.The definitions of several constant have been changed over time, as experiments got more precise and the theoretical background got better.It's thedefinitiononly, which changed, not the unit itself! One illustrating example is the change of the Josephson Volt between 1970 and 1990, see graph below.This definition depends on constants of nature only, i.e. h, e and the time reference by Cs radiation. So that's the kind of change one can find in ancient literture, and misinterpret that with a change of constants, like this layman did on searching in old physics books.The speed of light c is defined in vacuum! In air or other media, light travels at a lower speed, which is very well understood and described.You should be aware of the correct definitions, at first!Therefore, the value c can be checked on earth w/o any problem, as also the length of the experiment can be determined very precisely. (e.g. the Michelson-Morley experiment)The distance to the moon continuously changes, and can not be measured other than laser ranging, which involves the speed of light by itself, which would be a circular reference when trying to to determine c.On Wikipediahttps://en.wikipedia.org/wiki/Speed_of_lightthere's a table of the experimental improvement of the determination of c during the years, and there you can easily find the variations of several meters which that layman mentioned, but that's caused by the experimental uncertainty only, and has nothing to do with the invariance of this unit itself.You can only detect changes in the units themselves in the limits of the momentary experimental uncertainty. The best uncertainty achieved in 1972, was about 3E-9, or about 1 m/s, before the value was fixed.Next year, additionally the elementary charge e, Planck h and Avogadro N(A) will also be fixed to zero uncertainty.Anyhow, the magical metrology triangle will allow for check of the invariance of Ohms law in the future, using 3 independent quantum experiment, i.e. Josephson effect for Volt, Klitzing Hall effect for Ohm, and Charge pump.Once again, the values of h, e, and N(A) will have different values in the upcoming SI-2018 than the current CODATA-2014 values.The experimental uncertainty for the determination of h and N(A) is on the order of 2E-8 in the moment, see Watt / Kibble Balance and Avogadro experiments.Frank

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: July 31, 2017, 06:31:36 am
content: "The speed of light c is defined in vacuum! In air or other media, light travels at a lower speed, which is very well understood and described. You should be aware of the correct definitions, at first!"No, Dr. Frank, you should read the original post fully before commenting, as in:"Air density has a small effect (if not measured in vacuum)"Anyway, more or less confirms that the talk was BS. Suspected as much, although the BS'ers usually give themselves away by saying things that patently don't make sense.

author: Syntax_Error
author_rank: Regular Contributor
timestamp: July 31, 2017, 11:52:45 pm
content: Alright, so I watched this talk just now, and I have to be honest. I would have banned it, too. It's not that the question is poor, but the sum of all of his "points", his monologue, amounts to nothing more than an anecdote at best.I can have thoughts and opinions on technical matters that I am unqualified to hold opinions of merit on, too. Should I do a TED talk?

author: Khendrask
author_rank: Contributor
timestamp: August 01, 2017, 11:24:56 am
content: Don't forget that literally ANYBODY can give a TEDx talk on ANYTHING. All they have to do is come up with funding for the venue. TEDx should always be treated like the "FBI X-files". Total BS.