Continuing on with the discussion of G, Kestenbaum wrote an
article in Science that is of direct
importance.
It has all really come down to the precision of the tools
that are being used to measure the value for G. The value being calculated is
so small that any tool has to have precision or reliability in such a way that
it is almost a competition of sorts. Where there was original just the method
of Cavendish to calculate the value for G, scientists have come up with
numerous other methods that can always be used.
This is important to point out to students. One of the
beautiful truths about physics in my mind is that there is more than one way to
come about a conclusion. If a full understanding exists of what you are
researching as far as your methodology is concerned, you can develop multiple
experiments that differ in execution but prove the same point.
In the article, the talk about the different methods that
they have been using. One group is using the Cavendish method, but they
replaced one of the components to allow for more massive objects. Another group
has forgone using the torsion balance and is instead dropping an object and
using precision timers to detect small fluctuations. Yet another is using
massive vats of mercury to influence weights sitting on scales.
All of these different methods will still allow calculation
of G. The real beauty is in the agreement that they were having. The error bars
are quite large on some of them, but that is also relative to the size of the
axis in question. All told, the values were close.
David Kerstenbaum, "Gravity Measurements Close in on Big G," Science, Vol. 282, pages 2080-2081 (1998)
