Light, and time, today

London from space -- all lit up -- but this evening, between 8.30 and 9.30, is Earth Hour, aiming for all non-essential lights to be turned off ... imaging that brightness at the centre somewhat diminished as the floodlit buildings are quelled for a few moments...

And a few hours later, at 1am, the clocks spring forward.

(photo citymetric.com; more info on Earth Hour in London at londonist.com)