# Einstein wrong? Speed of light not constant? **URL:** \ **Category:** Factual Questions\ **Created:** [August 9, 2002, 1:18am UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063 "2002-08-09T01:18:47Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Mr\_Salads](https://avatars.discourse-cdn.com/v4/letter/m/c2a13f/32.png) [@Mr\_Salads](https://boards.straightdope.com/u/Mr_Salads)\ **Post date:** [August 9, 2002, 1:18am UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063/1 "2002-08-09T01:18:47Z")
Here is an article from Reuters on AOL. If you don’t have AOL there’s no way for me to link this, so I’ll try to put as much critical info from it without pasting the whole thing. Post your thoughts! > [@](#): > > SYDNEY (Aug. 7) - A team of Australian scientists has proposed that the speed of light may not be a constant, a revolutionary idea that could unseat one of the most cherished laws of modern physics – Einstein’s theory of relativity. > > The team, led by theoretical physicist Paul Davies of Sydney’s Macquarie University, say it is possible that the speed of light has slowed over billions of years. > > If so, physicists will have to rethink many of their basic ideas about the laws of the universe. > > ‘‘That means giving up the theory of relativity and E-mc squared and all that sort of stuff,’’ Davies told Reuters. > > The suggestion that the speed of light can change is based on data collected by UNSW astronomer John Webb, who posed a conundrum when he found that light from a distant quasar, a star-like object, had absorbed the wrong type of photons from interstellar clouds on its 12 billion year journey to earth. > > Davies said fundamentally Webb’s observations meant that the structure of atoms emitting quasar light was slightly but ever so significantly different to the structure of atoms in humans. > > The discrepancy could only be explained if either the electron charge, or the speed of light, had changed. > > To establish which of the two constants might not be that constant after all, Davies’ team resorted to the study of black holes, mysterious astronomical bodies that suck in stars and other galactic features. > > After considering that a change in the electron charge over time would violate the sacrosanct second law of thermodynamics, they concluded that the only option was to challenge the constancy of the speed of light. > > It could be that the possible change in light speed will only matter in the study of the large scale structure of the universe, its origins and evolution. > > For example, varying light speed could explain why two distant and causally unconnected parts of the universe can be so similar even if, according to conventional thought, there has not been enough time for light or other forces to pass between them. > > It may only matter when scientists are studying effects over billions of years or billions of light years. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 9, 2002, 1:36am UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063/2 "2002-08-09T01:36:49Z")
Take a look at [Bye Bye, Speed of Light](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=129670) over in Great Debates. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 9, 2002, 1:46am UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063/3 "2002-08-09T01:46:31Z")
The thing that might be changing is something called the Fine Structure Constant. This is defined as the square of the charge of an electron, divided by two times Plank’s constant times the speed of light times the permissivity of the vacuum. They’ve decided that the part of the equation least unlikely to be variable is the speed of light, but that’s still a very controversial claim. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [August 9, 2002, 2:32am UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063/4 "2002-08-09T02:32:50Z")
> [@](#): > > The discrepancy could only be explained if either the electron charge, or the speed of light, had changed. The speed of light measured in meters per second is constant by definition. In October 1983 the meter was defined as the distance light travels in 1/229,792,548 second. This means that the speed of light is necessarily constant and equal to 229,792,548 meters per second. According to Relativity, this definition is equivalent to a definition using (idealized) rigid rods. If the two definitions are not equivalent, then we can ask if rigid rods change length, but the speed of light cannot change. I would have thought that the units of electric charge would be defined in terms of the electron’s charge, which would make the electron’s charge necessarily constant. I looked up the definition of charge in a physics book. My book said that the unit of electric charge is the Coulomb and it was defined in terms of the second and the ampere. It said that the ampere would be defined in later chapter. I look ahead for the definition of ampere and find that the ampere is defined as one Coulomb per second :rolleyes: ---
**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\ **Post date:** [August 9, 2002, 5:30pm UTC](https://boards.straightdope.com/t/einstein-wrong-speed-of-light-not-constant/123063/5 "2002-08-09T17:30:29Z")
Wrong kind of photon? How many kinds are there?