NASA testing Einstein theory

Nasa hopes Gravity Probe B will lift off from California on 17 April.

Since it was first proposed in 1959, the project has been aborted and delayed because of technical hiccups many times.

Now it is ready to test two of Einstein's theories about the nature of space and time, and how the Earth distorts them.

The unmanned satellite will orbit 640km (400 miles) above Earth, measuring any slight changes in gravity.

A satellite that will put Albert Einstein's Theory of Relativity to the test is ready to be launched.

The satellite will carry four ping-pong-sized balls made from quartz and sealed in a vacuum. The scientists behind the project say they are the most perfect spheres ever made.

To ensure accuracy, the balls must be kept chilled to near absolute zero, inside the largest vacuum flask ever flown in space, and isolated from any disturbances in the quietest environment ever produced, said Anne Kinney, director Nasa's division of astronomy and physics.

Once in space the balls will be sent spinning. If Einstein is correct, there should be slight changes to the balls' orientation, or 'spin axis'.

Einstein proposed in 1916 that space and time form a structure that can be curved by the presence of a body.

Gravity Probe B will test how space and time are warped by the presence of the Earth, and how the Earth's rotation twists and drags space-time around with it, report BBC.

The $700 million Gravity Probe B spacecraft will be launched April 17 from California atop an unmanned Boeing Delta II rocket to test the German physicist's 88-year-old theory of general relativity.

"Einstein predicts that space and time are both warped and dragged by the presence of our own massive and rotating Earth, and Gravity Probe B will test this prediction," Anne Kinney, director of NASA's astronomy-physics division, said Friday in a televised question and answer session with reporters from NASA headquarters in Washington. "This will be the most accurate test of Einstein's theory."

Before the 20th century, many scientists believed space-time was a void unaffected by planets and other bodies that spun around inside it. But in Einstein's widely accepted theory, space-time is a structure that's not only warped by such cosmic activity but also helps direct the movement of those bodies.

It's kind of like what happens when a bowling ball (the planet) is placed on a bed sheet (space-time), according to one NASA analogy.

From its 400-mile-high polar orbit over Earth, the Gravity Probe B experiment will attempt to confirm or debunk two predicted effects of Einstein's theories, NASA says. One is that a gyroscope - a guidance device used in things like airplanes and missiles - without any outside interference should move slightly off kilter when it's near a massive object like the Earth, inform al.com

The project has been hailed as a marvel for its work with cryogenics and engineering. The gyroscopes' four spherical rotors, each the size of a ping-pong ball, are considered the roundest manmade objects in the world. Scientists can also detect a change of angle equal to the width of a human hair as seen from 10 miles away. To ensure the experiment's success, scientists had to create almost unheard-of conditions inside the satellite, where the instruments will be kept chilled at minus 455 degrees Fahrenheit with liquid helium.

The probe can even boast its own spinoff technologies. Graduate students who worked on the project helped develop better GPS systems that are now used in aircraft landings. They also created a type of superglue that can stand up to the pressures of space, according to boston.com