The probe was launched at 9:57 am (1657 GMT) from Vandenberg Air Force Base in California aboard a Boeing-built Delta II rocket, according to NASA spokesman George Diller.

NASA is "testing for truth in the physics of our universe," said Diller.

The probe will seek to prove German-born Einstein's theory of relativity, that time and space are distorted by the presence of massive objects. The Earth distorts space-time around itself, producing the effect of gravity.

Developed by California's Stanford University, and built by Lockheed Martin, the probe is transporting four sophisticated gyroscopes, each the size of a ping-pong ball, to provide an almost perfect space-time reference system.

The 16-month mission comes as part of a project that began 45 years ago.

To test the theory of general relativity, the probe will assess all infinite movement on the gyroscopes' orientation axis via a telescope turned toward the point of reference -- a star known as IM Pegasi.

Once the instruments are perfectly calibrated, within 60 days, the measurements will begin.

Einstein's theory has already been proven indirectly, but due to lack of sufficiently sensitive instruments, never before directly.

SPACE.WIRE