Seraphim
04-18-2004, 06:40 PM
By Broward Liston
CAPE CANAVERAL, Fla. (*******) - Almost a century after Albert Einstein began writing about relativity, NASA (news - web sites) is poised to launch a mission 45 years in the making to put a little known tenet of his general relativity theory to its first test.
The Gravity Probe B satellite is the bland name given to one of the most precise scientific instruments ever built. But the project's $700 million price-tag adds glamour, as does its long history, surviving the Congressional budget ax seven times.
Lift-off of the Boeing Co. Delta 2 rocket carrying the probe is scheduled for Monday at 1:01 p.m. EDT from the rocket range at California's Vandenberg Air Force Base.
With four near-perfect spheres -- the roundest objects ever made, according to NASA -- the probe will try to show whether the Earth, which is known to warp both time and space with its mass, also twists them like tornado winds as it rotates.
That was Einstein's prediction in his theory of general relativity. He had already, in 1905, answered many of the most important questions about mass, energy and the speed of light with his theory of special relativity.
INSIGHTS INTO TIME AND SPACE
By 1915, he was applying those insights to time and space. His theories showed how massive objects -- planets, stars, black holes -- warp time and space, slowing down clocks and sucking nearby objects toward them.
That is why an apple falls from a tree and speeding planets do not escape the sun.
Einstein also argued that the space-time continuum was twisted and dragged by the spinning of massive objects, an effect known as "frame dragging."
"We've seen two of the three aspects of warped space-time. We've seen the warping of space and the warping of time. We have never seen, in any clean way, the dragging of space into motion," said Kip Thorne, who holds the Richard Feynman chair in theoretical physics at the California Institute of Technology.
Scientists at Stanford University began discussing the idea of using a satellite to test this theory in 1959, just one year after the United States launched its first satellite. NASA signed on and funded the project in 1964.
"This test of relativity is very simple in concept, but when you get down to the technology of how to do it, it's a testimony to perseverance to say the least," said Stanford professor Brad Parkinson, who heads the engineering team.
As it turns out, the effect is dramatic around something as massive as a black hole, but rather minimal when measuring the space around something Earth-sized. So the measuring instruments had to be extremely precise, said Parkinson.
To an astronaut orbiting the Earth, the effect is undetectable, but Einstein's theory says that a small bit of space is actually lost as space is spun around on itself.
"You would find if you could measure the radius and the circumference (of that orbit) there would be a small defect which I like to call the missing inch," said Francis Everitt, a theoretical physicist from Stanford, the principal investigator on the NASA project.
Finding it takes precision. Not only do the Ping-Pong sized spheres have to be nearly perfect, they also have to be housed in a chamber that is the quietest ever produced, so sound waves will not effect them. They are chilled to almost absolute zero, so their own molecular activity will not jar them.
As for whether Einstein was right, Everitt offers no predictions: "We must be hard-headed experimentalists, making sure we do the experiment right. I believe this will be by far the most credible of any of the tests of general relativity."
CAPE CANAVERAL, Fla. (*******) - Almost a century after Albert Einstein began writing about relativity, NASA (news - web sites) is poised to launch a mission 45 years in the making to put a little known tenet of his general relativity theory to its first test.
The Gravity Probe B satellite is the bland name given to one of the most precise scientific instruments ever built. But the project's $700 million price-tag adds glamour, as does its long history, surviving the Congressional budget ax seven times.
Lift-off of the Boeing Co. Delta 2 rocket carrying the probe is scheduled for Monday at 1:01 p.m. EDT from the rocket range at California's Vandenberg Air Force Base.
With four near-perfect spheres -- the roundest objects ever made, according to NASA -- the probe will try to show whether the Earth, which is known to warp both time and space with its mass, also twists them like tornado winds as it rotates.
That was Einstein's prediction in his theory of general relativity. He had already, in 1905, answered many of the most important questions about mass, energy and the speed of light with his theory of special relativity.
INSIGHTS INTO TIME AND SPACE
By 1915, he was applying those insights to time and space. His theories showed how massive objects -- planets, stars, black holes -- warp time and space, slowing down clocks and sucking nearby objects toward them.
That is why an apple falls from a tree and speeding planets do not escape the sun.
Einstein also argued that the space-time continuum was twisted and dragged by the spinning of massive objects, an effect known as "frame dragging."
"We've seen two of the three aspects of warped space-time. We've seen the warping of space and the warping of time. We have never seen, in any clean way, the dragging of space into motion," said Kip Thorne, who holds the Richard Feynman chair in theoretical physics at the California Institute of Technology.
Scientists at Stanford University began discussing the idea of using a satellite to test this theory in 1959, just one year after the United States launched its first satellite. NASA signed on and funded the project in 1964.
"This test of relativity is very simple in concept, but when you get down to the technology of how to do it, it's a testimony to perseverance to say the least," said Stanford professor Brad Parkinson, who heads the engineering team.
As it turns out, the effect is dramatic around something as massive as a black hole, but rather minimal when measuring the space around something Earth-sized. So the measuring instruments had to be extremely precise, said Parkinson.
To an astronaut orbiting the Earth, the effect is undetectable, but Einstein's theory says that a small bit of space is actually lost as space is spun around on itself.
"You would find if you could measure the radius and the circumference (of that orbit) there would be a small defect which I like to call the missing inch," said Francis Everitt, a theoretical physicist from Stanford, the principal investigator on the NASA project.
Finding it takes precision. Not only do the Ping-Pong sized spheres have to be nearly perfect, they also have to be housed in a chamber that is the quietest ever produced, so sound waves will not effect them. They are chilled to almost absolute zero, so their own molecular activity will not jar them.
As for whether Einstein was right, Everitt offers no predictions: "We must be hard-headed experimentalists, making sure we do the experiment right. I believe this will be by far the most credible of any of the tests of general relativity."