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This forum is about wrong numbers in science, politics and the media. It respects good science and good English.

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Re: 100,000,000

On the subject of the speed of light changing with time, I haven't heard of the idea of it increasing with time, I thought that the speculated general trend was that it has been higher in the past, that is decreasing with time. As I remember it, there was a Horizon documentary broadcast about ten years ago about the speed of light possibly having being higher in the past.

One thing many people may not realise is that the science establishment re-defined the SI unit of distance, the metre, back in 1983 to be based on the speed of light, c, as mentioned in the Usenet Physics FAQ for the question "Is The Speed of Light Constant?"


The 'new' definition is: "The metre is the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second" where the 299792458 number is the speed of light in m/s. This definition reflects the fact that it has now become more convenient to measure distances using lasers, and laser based distance measuring gadgets are now even in domestic use. But implicit in that definition is that c does not change with time at all, and it also assumes that special relativity is correct. So anybody who wanted to carry out experiments to investigate whether c changes with time, or carry out experiments which aim to disprove special relativity, assuming they could get such experiments funded, would have to use a non-standard definition of distance.

On the idea of autism being a time dependent function, I think most of the time dependence is probably coming from 'broadening definition syndrome'. In the last few decades the idea of being autistic seems to have been broadened out to include people who might previously have just been regarded as 'social misfits' or maybe just eccentric. So Newton and Einstein are now regarded as having being mildly autistic, and there are some contemporary famous people regarded as being mildly autistic like singer Susan Boyle and Gary McKinnon (the hacker who got into Pentagon computers supposedly looking for government cover-ups of UFOs and free energy devices).

Re: 100,000,000

I guess c doesn't change over time fast enough for us to be able to detect it so the SI definition remains useful. Using a single physical standard has its problems as well. What if we find out the size of fundamental particles is also changing slowly over time? What if we find out, as we did, that the mass of the standard kilograms is changing over time, and indeed they are diverging, slightly. Even bigger problem if someone drops one of them.

With length, I think an earlier definition was based on the circumference of the earth at the equator, which changes detectably from one year to the next. It didn't when defined, because that was before satellites could measure sea level rise to the millimetre, or variations in bulging due to tectonic effects on the rotational velocity of the planet.

So trying to find a better standard is good science, while expecting a perfect standard is not. I know that will rile the physicists here, but as a "soft" clinical biologist, I couldn't care less about the finer points of SI standards - any femtoAngstrom differences from the previous definition don't affect my work. I guess the only one we can't change is the mole (is that even an SI unit?), which is really just a big integer, thus could be replaced (if less conveniently) with a prefix, if we had a prefix for 10^23. It's really convenient because it bridges atomic weights to the SI system, but why does it deserve to be a base unit?

It seems likely that the SI units will be useful approximations to reality at all meaningful scales for the remainder of human civilisation (and we can put a plausible one billion year maximum on that, probably it wlll be rather less), which is as long as we need them.