How do scientists use Einstein's theory to show that space is curved?
Einstein's General Theory of Relativity *predicts* that space-time
is curved in the vicinity of mass. Scientists have performed
experiments to *measure* this curvature: one such experiment
measured the bending of light from distant stars as it passed
close to the Sun during a total solar eclipse.
Extra credit for the student: What's the difference between
Einstein's General Theory of Relativity and his Special Theory