  The energy flow of zero-point radiation is very great, but difficult to put
to use. However, the observations made by Sparnaay in 1958 and by Lamoureux in
1997 reveal the possibility of making use of a very small fraction of that
immense amount. This possibility is big enough for such a minute fraction to
have significant importance, but such a possibility requires miniaturisation to
a degree which may be unattainable. It is worth trying to achieve it, since it
would open the way to interstellar travel.
