[marginwalker777 (OP)]

Hi

First post & it was something I was thinking about whilst trying to pedal faster on my bike. Excuse me if it's already been asked or if I have misunderstood the fundamentals.

It is said that closer you get to the speed of light the slower time for you goes, relative to say your point of origin eg 3 months may have passed for me but like 80 years has passed for the people on Earth. My question is how fast do you have to be going before you first start to see the effects of relativity & this time distortion ? Hope I've explained that well enough........

[Soul Surfer]

Firstly time always passes perfectly normally for "you" and things moving slowly near you. It is only when you look at other things that are moving very fast or go on a fast journey and return with an accurate time reference that the differences become noticeable.

Relativistic corrections have to be applied to the GPS systems  These are earth satellites traveling at around 18,000 mph so if you are measuring time very accurately.  Gravitational and relativistic time effects have been measured using atomic clocks on aircraft travelling round the world.

Gravitational red shifts have been measured using Mossbauer spectrometry in the earth's gravitational field.

[marginwalker777 (OP)]

Thanks for the response Soul Surfer.

Didn't realise that GPS satellites have to have a correction due relativity ! At 18,000 mph I guess there would be noticable effect. Think I'm ok at my 20mph on my bike....... though my wife tells I've been out 2 hrs but I swear it's only 1 !