Soon after 9/11 an email began to circulate urging people to light a candle and stand outside their home with it at a specified date and time (the date varied between versions of the email). Supposedly a NASA satellite would then take a photograph of the entire nation illuminated by candlelight in order to demonstrate the solidarity of the American people in the face of terrorist aggression. The photo would appear on NASA's website the following day.
NASA never planned to take such a photograph. The light of even 200 million candles spread out over the entire nation would be invisible from space. Therefore, a photo of the nation illuminated by candlelight would be dark. Nevertheless, at the specified time numerous people dutifully stepped outside their homes and held a candle up to the sky.
It is not known who started this email hoax. It might have been started by someone who thought it would be a good idea if
NASA would take such a photo, not realizing that such a photo would show nothing.