Wisconsin, who pointed out that most PCs are often idle and pi'opo~ peIOlli'lg th~:lf spare processing capacity using Internet software. The first well- known application was for the SETI (search for extraterrestrial intelligenceJ project. Home- computer users could download a screen-saver, SETI@home, which sifted through the
plethora of radio signals received from space by the Arecibo telescope in Puerto Rico. Other '@homes' soon followed enabling various medical
projects such as cancer and
AIDS research.
This was just the beginning.
In 1995 Ian Foster at Argonne National Laboratory and Car! Kesselman of the University of Southern California took. the concept in a new direction.
They realised that research communities, which are becoming increasingly international and multi- disciplinary, could link all their computers so as to share data, applications, instruments and
other resources in a coordinated and controlled way to create a single virtual laboratory. The concept of the Grid was born.
Foster envisages that to solve particular problems, groups of people would come together
to form 'virtual organisations' supported by the Grid infrastructure. These could be particle physicists working with
a new collider, a company consortium designing a new jet, or a crisis-management team dealing with an environmental problem.
Creating a large-scale computing infrastructure, of course, requires not only the right hardware - sets of computer clusters and high- speed connections - but also standard protocols and services
to knit the system together - 'middleware'. The system has
to '00 secure and intertace flexibly with different operating platforms. It has to recognise who is allowed access, what kinds of programs or data are being requested and how to allocate the computer resources. A set of Grid tedlnologies is slowly emerging, the first being provided by the Globus Toolkit developed by teams headed by Foster and Kesselrnan. However, other researd\ groups are
also working on providing middleware components.
Microsoft and Sun are also gearing up to participate in creatIng the Infrastructure.
The ultimate aim will be eventually to provide an
intelligent global computing and data resource, that. like the present Internet. can be exploited by science, commerce
and individuals according to their needs.

Grids 'R' Us
Scientists, especially physicists. have been quici< to recognise
the potential of this new way of working. Grid projects abound. For example, in the US there
is the Grid Physics Network (GriphyN), the NASA Information Power Grid, the Department of Energy Science Grid, the Particle physics Data Grid and the National Science Foundation's Tera Grid, among others. Europeans have been equally active and are working on a range of initiatives including the CERN DataGrid, an EU-funded Eurogrid and the Virtual Observatory (see Box).
The UK Government has
also recognised the potential
of e-science, allocating £120M over 3 years for various Grid applications in all areas of science and engineering, for upgrading hardware and for developing generic middleware. Theoretical physicist and connputer scientist, Tony Hey, leads the initiative. A national network of Grid centres is being set up. Many of the projects will involve collaboration with industry as well as interfacing with international Grid projects. IT companies sum as IBM,
~

Astronomy offers an ideal testbed for e-science. Astronomers realised that ongoing and new sky surveys cataloguing stars and galaxies at all wavelengths were creating vast data sets. The idea of a Virtual Observatory
has emerged as a way of coordinating the
data from the different archives so they could be easily accessed. This approach will change the way astronomers work. They will be able
to explore a wide range of observations, across wavelengths for example, in a way that will lead to new astrophysical insights. Furthermore, researchers in developing countries, and students, will benefit as they
are given direct access to resources
otherwise unavailable to them. The sociological impact of the Grid approach to doing science will be enormous.

The VISTA telescope
GilMORE OF THE CAMBRIDGE
NSTITUTE OF ASTRONOMY FOR THEIR HELP WITH THIS PAPER