How Vacuums Work

If a balloon was filled by a vacuum -- rather than helium or air -- would it float? Check out this HowStuffWorks podcast to learn the science behind balloons and vacuum.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how stuff works dot com
where smart Happens. Hi, I'm Marshall Brain with today's question,
what a balloon filled with vacuum instead of helium float?
At sea level? Air weighs about one point to five
grams per leader. A leader of helium, on the other hand,

(00:20):
weighs about point one eight grams. If you weigh a
one leader bottle filled with air and then weigh the
same bottle filled with helium, it will weigh about one
gram less. If the bottle itself weighed less than a gram,
you couldn't weigh it at all because it would float.
You would have to turn the scale upside down and
put it above the floating bottle to check its negative weight. Generally,

(00:44):
a balloon has to be several leaders in size before
that one gram per leader weight difference of helium versus
air is enough to overcome the weight of the balloon
itself and float. If you could somehow fill a one
leader bottle with a vacuum, it would float even better.
A perfect vacuum ways zero grams, so a leader of

(01:06):
perfect vacuum ways zero grams, and that's point one eight
grams less than a leader of helium. The problem, of course,
is that building a lightweight container that can hold a
vacuum is not nearly as easy as building a container
that can hold helium. The phrase nature of horrors of
vacuum sums it up nicely. If you could figure out

(01:26):
a way to do it, however, you could be set
your vacuum balloon would float even better than a helium balloon.
Not that you don't need to have a perfect vacuum
for this to work. Any air that you take out
of the container helps a vacuum balloon to float. Do
you have any ideas or suggestions for this podcast? If so,

(01:47):
please send me an email at podcast at how stuff
works dot com. For more on this and thousands of
other topics, go to how stuff works dot com.