We went to walk through the under the Thames tunnel from the aisle of dogs to Greenwich but sadly its closed for renovations to the stairs. So we got back on the light rail to go across instead.
There is a good information building with models and interactive presentations. After a quick history on the area Greenwich area we proceeded toward the royal observatory on top of the hill. About half way up I got out my got and went looking for the 0.00000 longitude line. After finding what I thought was it we continued to the top of the hill to the observatory buildings. I started searching again and found the GPS reading 0 about 30 - 40 meters east of where it should be. Sharon also had a similar reading. I discussed the finding with one of the observatory workers and he informed us that it was due to the earth not being a perfect sphere and also the USA introduces a margin of error into it. So basically the GPS is reasonably accurate but due to fear and imperfections in the creation of the earth its not exact.
After the nerd episode with the GPS's we had a look through and saw the actual line and many clocks including the ones built to try to solve the problem of finding longitude at sea.
The 0 line
The red observatory ball which was dropped at (i think) 1pm so the boats in the harbour could set their clocks.
The gate clock and measure standards.
Part of the cutter head used for cutting the Thames rail tunnel.
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