AAO Colloquium. Thursday, 13th September 2001 - 3:30pm AAO Conference Room DO THE LAWS OF NATURE CHANGE WITH TIME? John Webb University of New South Wales Theories unifying gravity with other interactions suggest there may be spatial and temporal variation of the fundamental "constants" in the Universe. Current interest is high because in superstring theories which have additional spatial dimensions, "compactified" on tiny scales, any cosmological change in the size of the extra dimensions results in changes of the 3-dimensional observed physical constants. Astronomical observations of distant quasars provide a highly sensitive way of investigating this. In particular, a change in the "fine structure constant" could be detected using high precision quasar spectroscopy. I will describe how this is done and show some very recent results which suggest that indeed some variation is seen. If correct, this will inevitably lead to fundamental revision of our understanding of the universe.