Why do you hear a glugging sound when you pour a liquid out of a bottle by holding it upside down?
Asked by: Matt
Answer
That is just air rushing in to fill the space left above
the liquid. As the liquid leaves, the pressure above it
decreases until the larger atmospheric pressure outside
the bottle forces air in to equalize pressure.
You'll notice that if you pour out the liquid gently,
leaving an open space between it and the top of the bottle
opening, air can enter more gradually, without the
'glugging'.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor
'I beseech you to take interest in these sacred domains so expressively called laboratories. Ask that there be more and that they be adorned for these are the temples of the future, wealth and well-being. It is here that humanity will grow, strengthen and improve. Here, humanity will learn to read progress and individual harmony in the works of nature, while humanity's own works are all too often those of barbarism, fanaticism and destruction.'