How do 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):
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(00:27):
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, weighs about point
one eight grams. If you weigh a one leader bottle
filled with air and then weigh the same bottle filled

(00:48):
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,
a balloon has to be several leaders in size before

(01:08):
that one gram per lead or weight difference of helium
versus air is enough to overcome the way to 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
perfect vacuum ways zero grams, and that's point one eight

(01:31):
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 whores of
vacuum sums it up nicely. If you could figure out
a way to do it, however, you could be set
your vacuum balloon would float even better than a helium balloon.

(01:55):
Now 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. For
more on this and thousands of other topics, visit how
stuff works dot com. Your photos, music and documents are irreplaceable.

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