From P. MARCHESE
One question about general relativity/time dilation has intrigued me
for 50 years but my mathematics is inadequate to answer it (‘A special theory
of relativity’, Inside Science, 21 September).
When a body is accelerated to near the speed of light and then its direction
of travel is reversed and it returns to whence it came it has aged less
than companion bodies that have remained stationary. This process, of course,
requires energy. How much? How many joules are needed to make 1 kilogram
of matter one second less old? Does growing old create energy?
P. Marchese Maidstone, Kent
