  An important aspect of a Euclidean network is its link length distribution,
studied in a few real networks so far. We compute the distribution of the link
lengths between collaborators whose papers appear in the PhysicalReview Letters
(PRL) in several years within a range of four decades. The distribution is
non-monotonic; there is a peak at nearest neighbour distances followed by a
sharp fall and a subsequent rise at larger distances. The behaviour of the
statistical properties of the distribution with time indicates that
collaborations might become distance independent in about thirty to forty
years.
