Meanwhile over at Conservapedia, a place where reality is a far and distant undiscovered country, we have the claim that Relativity is a myth. The page on that explains …
The theory of relativity is disproved by numerous counterexamples, but is promoted by liberals who like its encouragement of relativism and its tendency to pull people away from the Bible
… so there you go folks, avoid all that evil Relativity because it will pull you away from the bible (gasp!).
Meanwhile back in our reality you have some rather solid evidence that it really does work.
To work out exactly where on the planet you are there is the GPS system that consists of 24 satellites that have been positioned such that no matter what your location is on the surface, you can pickup a signal from at least four of them. OK yes, you only need Newtonian mechanics to get them up there and keep them there, but if you want to have a precise calculation of exactly where you are in realtime as you drive, then you need to be able to pickup the clock ticks from the GPS satellites in your line of sight to an accuracy of about 20 or perhaps 30 nanoseconds.
Now the problem is this, if you live in a world (as we do) where Relativity is a reality, and you only knew about Newtonian mechanics, then you would be stuffed because the system would simply not work and you would have no idea why.
Both Special and also General Relativity are in the mix here.
Because of their relative motion special relativity predicts that the clocks on the satellites will, due to the time dilation effect, fall behind the time of the clocks on the ground by about 7 microseconds per day, so unless you account for that effect in your calculations you have no way of achieving the required accuracy of 20 to 30 nanoseconds to work out where you are.
Is that it then?
Nope, that is still not enough.
The satellites are in high orbit and so are further away from the the curvature of spacetime caused by the mass of the earth. This is now where General relativity comes into play, it predicts that the closer you are to a massive object the slower time goes, and so the clocks in the satellites will actually be ticking away at the faster rate of about 45 microseconds per day.
So to sum that up …
45 microseconds per day faster due to General Relativity – 7 Microseconds slower per day due to Special Relativity = 38 microseconds faster
… and so once you introduce that calculation into your SatNav, it works … and if you don’t, then you will have no way of working out where the hell you are.
Is it really like this?
So there you go then, no Relativity means no SatNav, and so perhaps the Conservapedia dismissal of relativity explains why they are completely lost and have no idea that they are now living in the 21st century and not the 17th
- Wikipedia page on this rather daft Conservapedia claim
- Rational Wiki page on Conservapedia – confirms that Conservapedia is basically a vanity side run by a religious kook