The Greenwich Observatory in London, England is a very famous observatory built on the Prime Meridian and it has one of the most accurate clocks in the world. This building was the origin of Greenwich Mean Time, but, how much time does it have without people?
2 days after people: The power fails in England, sending the observatory into an eternal darkness. The famous clock, however, still ticks.
1 week after people: The backup batteries powering the clock finally die. The red glow of the display slowly fades away into the blackness.
6 months after people: Smaller plants, grass, and vines are slowly creeping their way up the walls and through the broken windows. Birds and insects soon follow, pollinating flowers and spreading seeds throughout the complex.
5 years after people: England is known for the amount of rain they get and leaves have clogged the gutters at the observatory. A rainstorm is forming over London. It pours rain and the leaves in the gutters soak up the water like a sponge, holding the water against the structure which causes it to corrode even faster.
25 years after people: Most of the windows in the building have broken, allowing water and debris inside. The time ball on top of the building that guided ships down the Thames is becoming loose. suddenly the thin cables holding up the ball snap, sending the ball crashing through the roof of the Octagon Building.
50 years after people: The hole made by the time ball 25 years ago has caused problems. The wooden beams protected by lead roofing are now exposed. Dry rot takes hold and causes the roof to collapse, destroying the Octagon Building in the process. The iron sphere shielding the telescope is weakening. Another strong thunderstorm brings down the telescope. The observatory is no more.