A problem with Mathematica

[hitfq]

I want to make an animation of a moving point using the command below, but the point doesn't move, how can I make it move using Manipulate? Thank you.

Manipulate[ Graphics[Point[{t , - t^2/2}] /. {t -> a}], {{a, 1}, 0, 10}]

[DaleSpam]

The point does move. There is just nothing else in the image to let you see the motion. Try

Manipulate[ Graphics[Point[{t, -t^2/2}] /. {t -> a}, Frame -> True], {{a, 1}, 0, 10}]

in order to see that the point does actually move.

[Hepth]

or, in addition to, add some fixed axis:
Manipulate[
Graphics[Point[{t, -t^2/2}] /. {t -> a}, Frame -> True,
PlotRange -> {{-10, 10}, {-20, 10}}], {{a, 1}, 0, 10}]