Padmanabhan, T.Seshadri, T. R.2012-03-022012-03-021987-12-16http://hdl.handle.net/11007/110It is shown that uncertainty principle prevents simultaneous, exact measurement of the expansion factor S(t) and its time derivative Ṡ(t) in a FRW universe. We compute the uncertainties in these parameters in the semiclassical limit. It is shown that (i) there is a minimum uncertainty ΔlH in the Hubble distance lH(t)=(Ṡ/S)−1 in a semiclassical universe. (ii) this uncertainty is amplified to an unacceptably large value if there was an inflationary phase in the early universe.enQuantum uncertaintyInflationary universeArticle