Originally posted by
Chris
Originally posted by
Aragorn
Originally posted by
Chris
[...] (such as the idea that the speed of light is a universal constant that never changes - not actually true if you look at the evidence) [...]
Um, yes, that is very, very true. The speed of light
in a vacuum — denoted by the symbol
c — is
always the same in every direction and for every observer, and this has been empirically proven. However, light can be slowed down when passing through a medium, and to such an extent even that other particles such as electrons might travel faster through said medium than light itself, albeit that these particles themselves, too, will then be traveling slower than
c.
The phenomenon of non-light particles passing faster through a medium than light itself (in said medium) is what gives rise to
Cherenkov radiation, the bluish light visible in nuclear reactors.
That's exactly the thing, Sheldrake found (and this has actually been confirmed by the official in charge), that the speed of light has been changing, not to a huge, but still quite a significant degree since the 1960s. Eventually the scientific community just decided to set the exact value in stone and ignore the phenomenon. I read this book (the Science Delusion) half a decade ago, so I don't remember the exact details, but you can check out his banned Ted talk for a summary, I think it's really interesting:
I've watched the video, but he mentions that the inconsistencies in the measurement of the speed of light date back to between the 1920s and 1945. At that point in time, measuring techniques and units had not been properly standardized yet, and as I've alluded to higher up already, we
must be talking of the speed of light in a vacuum in order to come to the constant
c.
It's not easy to explain all of this in a single post, because there are various influences involved with those measurements, as well as with the reference frames against which
c was calculated, so I'm going to defer to
the Wikipedia article on the subject, which is far more elaborate.
Addendum: I'm just thinking out loud now, but what could also play a role here, is if the density of spacetime were to change. We do after all know that the universe as we know it is still expanding — and it is doing so at a speed greater than the speed of light. That's why galaxies that are moving away from us are redshifted.
Somehow, the speed of light (in a vacuum) seems to be linked to the fabric of spacetime itself, because it is also the speed at which gravity waves propagate. Gravity waves themselves are distortions of spacetime, and even though Einstein dismissed the outdated theory that space would have been permeated by something called "the luminiferous aether", Einstein himself pondered that the idea in itself was not so crazy, but that this "aether" would then merely have been the fabric of spacetime itself, rather than some invisible and intangible form of matter.
There is either way still much that we know next to nothing about. That's a given.