The World Wide Web provides important infrastructure for scientific and engineering computation. The distributed computing hardware of the Web has remarkable potential compute performance--1,000 times that of the largest supercomputer. This ratio largely reflects the ratio of monetary investment in the two fields. Of course, the Web does not support the low latency and high bandwidth required by most parallel simulations. However, we believe that an attractive scientific computing environment can be built on top of Web software by adding to the basic Web loosely coupled distributed computing model, the necessary added functionality for computational science. We analyze, in Section 2, the various forms of concurrency seen in applications, and then in the last three sections, discuss three major areas where Java can be effectively used. We conclude that Java could well become a dominant language in science and engineering.