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It's not a directly related demo,  but in our relativity show we do a  
demo with a speech delay kit:

get someone to read out a tongue-twister so that they can try it out.
Then get them to put on headphones and read it out through a  
microphone.  The mike doesn't amplify their voice,  but feeds it back  
through the headphones with about 1 second delay - this makes it very  
difficult to read out the tongue-twister as they are hearing their  
own voice delayed.

The point we make with it is that it takes time for the signals to  
travel from GPS satellites to your receiver on earth and back.  The  
satellites have to compensate for this delay.  The clocks on the  
satellites are also moving so fast that they suffer time dilation.   
The effects of special and general relativity mean that clocks on  
satellites gain 7ms per 24 hours.  (45 gain due to weaker  
gravitational field, minus 38 lost due to time dilation).

It's a good demo in that it shows how difficult it is to process a  
message when your clocks are not synchronised,  but it is something  
that only the volunteer really experiences.  It always gets a laugh  
though,  as they trip over their words!,

Best wishes,

Helen
On 26 Sep 2008, at 16:20, Lisa McIntosh wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology  
> Centers
> Incorporated, a worldwide network of science museums and related  
> institutions.
> ********************************************************************** 
> *******
>
> Hello
>
> We are developing a new 20 minute program that highlights the role  
> of remote
> sensing (satellites) in monitoring changes on Earth.  We’re looking  
> for
> ideas for demonstrations that involve volunteers.  Any suggestions?
>
> Thanks
>
> Lisa McIntosh
> Director of Learning
> HR MacMillan Space Centre
>
>
> ********************************************************************** 
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Helen Lloyd
Science Communicator
science made simple limited
Cardiff University School of Physics and Astronomy
14-17 The Parade
Cardiff
CF24 3AA
e:[log in to unmask]
t: 02920 876884
f: 02920 874056
www.sciencemadesimple.co.uk





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