  We discuss how compactified extra dimensions may have potentially observable
effects which grow as the compactification scale decreases. This arises because
of lightcone fluctuations in the uncompactified dimensions which can result in
the broadening of the spectral lines from distant sources. We analyze this
effect in a five dimensional model, and argue that data from gamma ray burst
sources require the compactification length to be greater than about $10^5$ cm
in this model.
