From JOHN GRIBBIN
An experimenter who carries out measurements in a room (or spaceship)
in a rotating reference frame will measure a force, outward from the centre
of rotation. This is centrifugal force, and you can feel it any time you
are in a car that goes round a corner (it also makes you lighter than you
would be if the Earth were not rotating, assuming you do not live at a pole).
Although sometimes referred to by physicists as a ‘fictitious force’, they
mean by this that it exists only because of rotation.
In the story referred to, the centrifugal force does not act on the
spaceship, but on objects inside the spaceship – so in the special orbit,
people inside the spaceship are weightless, whatever the speed at which
the spaceship moves around the orbit. The whole point of this discussion
is that the spaceship is firing its motors to maintain various circular
orbits without being in free fall. Within the critical orbit, occupants
of the spacecraft will be pressed against the inside wall by centrifugal
force.
It was not, incidentally, New Scientist that introduced the term ‘centrifugal
force’ into the discussion – it is the one favoured by the relativists.
I would be interested to know if, indeed, there is any recognised alternative
term for this force.
John Gribbin Piddinghoe Sussex
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