Canadian astronaut Commander Chris Hadfield, currently on board the International Space Station, has been tweeting images of major cities prior to Earth Hour.
He wrote, "New York City, lit up like a bulb. The Statue of Liberty is clearly visible in the night from above".
The commander also highlighted that "spiderwebs of light expanding out from the dark river border" could be seen of Detroit and Windsor.
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A headteacher has payed tribute to a seven-year-old boy who was killed in a bus crash in Coventry at the weekend.
The daughter of a woman killed when a double-decker bus crashed into a Sainsbury's has told ITV News she will be "sadly missed by all".
A group of disabled activists threw toys and balls at him as he entered the conference.