MICHAEL SZOENYI / SCIENCE PHOTO LIBRARY MICHAEL SZOENYI / SCIENCE PHOTO LIBRARY
Timelapse footage of the inflation and take-off of several hot air balloons during the Chateau d'Oex Balloon Festival in Vaud, Switzerland, in January 2017. This festival has taken place annually since 1979. Hot air balloons are filled with hot air from a burner. Hot air is less dense than cool air and hence rises, lifting the balloons into the air.
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