atomic clock / radio-receiver chip

[Arne Kristian Jansen]

Federico Lorenzi skrev:
> On Sun, Jun 1, 2008 at 9:33 PM, Ilja O. <vrghost at gmail.com> wrote:
>   
>> On Sun, Jun 1, 2008 at 9:26 PM, cdr <_ at whats-your.name> wrote:
>>     
>>>> And portable thermonuclear bomb. Just in case. (Well, phone is already
>>>> hand interface to several orbital atomic clocks, isn't it?)
>>>>         
>>> the atomic clock(s) arent orbiting the earth,
>>>
>>>       
>> But why there are no clocks at the orbit? They could be useful enough.
>> E.g. if there are several of them each on predefined geostationary
>> orbit we could do lots of useful things with them! For example, we
>> could prove that general relativity indeed exists (although ionosphere
>> would likely to spoil party at some degree).
>>     
> Huh, I'm a little confused about whats being spoken about here, but
> the GPS satellites are effectively giant orbiting atomic clocks, its
> the basis of GPS.
>
> Cheers,
> Federico
>
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>   
Indeed they are:
http://en.wikipedia.org/wiki/Global_Positioning_System
(under Simplified method of operation).

And if the satellites did not take the relativity theory into account, 
they would be useless. The accuracy would be awful.
http://en.wikipedia.org/wiki/Global_Positioning_System#Relativity

Arne K