  A long standing conjecture states that the ropelength of any alternating knot
is at least proportional to its crossing number. In this paper we prove that
this conjecture is true. That is, there exists a constant $b_0>0$ such that
$R(K)\ge b_0Cr(K)$ for any alternating knot $K$, where $R(K)$ is the ropelength
of $K$ and $Cr(K)$ is the crossing number of $K$. In this paper, we prove that
this conjecture is true.
