One BOINC project that you can connect your computer to is LHC@home.
This is the worlds largest particle accelerator and it is in Geneva, Switzerland.
It is a 27KM ring under the ground where they are planning to accelerate particles up to the speed of light and smash them together to see what happens.
The results of what we learn from the experiments at CERN will teach us a lot about how the universe works. It will teach us many new things about particle physics.
And by the way, this thing only cost 30 billion dollars to build!. They are due to start the main testing on it by the end of 2007.
Here is a video giving a tour of the LHC (underground accelerator) at CERN. Measuring 27km in circumference, it will become the world's largest particle accelerator when it inaugurates in November 2007. (more)
5 min 42 sec
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Here is an areal view that maps the 27KM ring where it runs under the ground.
A view down through the tunnel
A view of the inside of the Atlas Detector
Look at the size of the man standing inside the detector!
And this thing is 100 metres under the ground!
