Nasa grounds its 'Einstein' probe

A satellite that will put Albert Einstein's Theory of Relativity to the test has had its launch delayed until Tuesday. The US space agency's $700m (£387m) probe was due to launch on a Boeing Delta 2 rocket from Vandenberg Air Base in California at 1701 GMT. The probe will now wait until 1657 GMT on Tuesday for another launch attempt. Ground controllers could not verify the rocket had all its correct flight software loaded, and halted the launch. Gravity Probe B will test Einstein's ideas about space and time and how the Earth distorts them. It will carry four near-perfect spheres in gyroscopes to help verify two key elements of Einstein's theory. The probe will align itself with its "guide star" IM Pegasi, so that the spin axes of the spheres point to this star. Over the course of the year their spin axes will be monitored for tiny changes that could be caused by the effects Einstein described.