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Reblogged by kornel ("Kornel"):
futzle@old.mermaid.town ("Deborah Pickett") wrote:
If you live in a city with tall buildings, take a look at the night skyline. The buildings probably have flashing lights on them to help aircraft pilots to identify the shapes of buildings and not fly into them.
You might notice that the buildings flash in synchrony, even though they are hundreds of metres apart. What's going on?
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