The Greenwich Time Ball and one time for all

How do you know that your watch, clock or phone is telling exactly the right time?
At one time, the only way was to look to the roof of the Observatory.

Picture the scene, you are looking down from the Observatory to the Thames bustling with tall ships.
It’s the Victorian era and naval power and the British Empire are at their peak.
On the decks, officers stand ready, watch in hand waiting for the signal on the hill.
Setting the time will be a life and death matter for these mariners.

The bright red Time Ball on top of Flamsteed House is one of the world's earliest public time signals, distributing time to ships on the Thames and many Londoners.
It was first used in 1833 and still operates today.


What does the Time Ball do?

Each day, at 12.55, the time ball rises half way up its mast.
At 12.58 it rises all the way to the top.
At 13.00 exactly, the ball falls, and so provides a signal to anyone who happens to be looking.
The Time Ball drops at 13.00 GMT during the winter months and 13.00 BST during the summer.