This is simply allowing for travel at speeds faster than the speed of “visible light”.
Regardless of physical impossibility, it is certainly an answerable question using math,
provided that additional variables are supplied.

Standard presumptions:
1) Visible light is used to identify “clock showing”.
2) Visible light from the place called “clock showing” is traveling in a straight line in the same direction ( or all directions ) at a constant speed of 300,000KPS since 7:30pm

Additional information needed:
1) "one sets of from london at 8pm on a friday"
is equivalent to
"what time the clock on westminster based on the visible light at your position".
( i.e., removing the time delay of visible light between
what is called "sets out from" and
what is called "clock showing".
2) The clock was always at the same “clock showing” place since 7:30pm
3) The clock continued to run accurately since 7:30pm

With this additional information, the “clock showing” is 7:30pm

BTW - this would be pseudo time travel, not real time travel.
You would be using time simply to travel to a place that contained visible light which originated at a different place at an early time.

It would be 9:00pm, God’s time, even though you were now at a place where visible light had taken 1.5 hours to reach.

• Can someone check my math ? - bible_believer3 - October 24, 2003 - 11:09 UTC