The launch of the Gravity Probe B has been delayed for 24 hours because of concerns about the accuracy of the weather profile uploaded to the onboard computers.

According to a statement on the NASA website a hold was called around three minutes before lift off. The launch team had noted what NASA describes as "marginal" wind conditions during the countdown, and wanted to double check the data against information from a final weather balloon.

Delay was impossible because of the extremely short launch window, and the launch was canned when it became clear that the data could not be cross-checked in time.

The probe has been designed to test two predictions of Einsteins's Theory of Relativity. It carries four of the most perect spheres ever made, which should be able to detect the Earth's influence on space-time.

The launch is now scheduled for 16:57:24 GMT today, Tuesday. ®

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