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NASA Announces Results of a grand experiment on the space-time


http://ciencia.nasa.gov/ciencias-especiales/04may_epic


May 4, 2011: Einstein was right again. In fact, there is a vortex in space-time around the Earth and its form coincides precisely with the predictions of the theory of gravitation Einstein.
These facts were confirmed by investigators at a press conference held at the base of operations for NASA, which announced the much awaited results Gravity Probe B satellite (Gravity Probe B, in English), or GP-B, for its acronym in English.
"The space-time around the Earth is being distorted exactly as predicted by general relativity, says physicist Francis Everitt, Stanford University, who is principal investigator of the Gravity Probe B mission

artist's concept of GP-B probe measuring the curved spacetime around the Earth. [More information].
"This is a great result," says Clifford Will, Washington University in St. Louis. Expert in the theories of Einstein, Will chaired an independent panel of National Research Council, which was created by NASA in 1998 to monitor and review the results of Gravity Probe B. "Someday" predicts, "This is part of the textbooks as one of the classic experiments in the history of physics."
time and space, according to the theories of relativity of Einstein, are intertwined and form a four-dimensional fabric called "space-time." The mass of the earth creates a recess in this tissue, similar to what happens when a heavy person sitting in the middle of a trampoline. According to Einstein, gravity is simply the movement of objects that follow the curved lines cleavage.
If the Earth was kept stationary, that would be the end of the story. But Earth is not steady. Our planet revolves around itself, and the spin should twist slightly slit to form a vortex pulling in four dimensions. This is what GP-B went to investigate in 2004.
The idea behind the experiment is simple:
Place a gyroscope in orbit around Earth, with the spin axis pointed toward some distant star, to serve as fixed reference point. Because it is free of external forces, the gyroscope's axis should continue pointing at the star forever. But if space is twisted, the direction in which points the axis of the gyroscope should change over time. In recording this change of direction on the star, it would be possible to measure the twisting of space-time.
However, in practice, the experiment is quite difficult.

One super spherical gyroscopes Gravity Probe B. [More]
The four gyroscopes that are located on board the GP-B are the most perfect spheres created by man. These spheres of fused quartz and silicon measured 3.8 centimeters (1.5 inches) in diameter (the size of a ping-pong ball) and never be diverted from areas perfect in more than 40 layers of atoms. If the gyroscopes were not so spherical, their spin axes would wobble even without the intervention of the effects of relativity.
By some estimates, the twisting of spacetime around Earth should cause the axes of the gyroscopes to change just 0.041 seconds of arc per year. One arcsecond is 1/3600va of a degree. To measure this angle correctly, the GP-B needed a fantastic precision of 0.0005 arcseconds. This is as difficult as measuring the thickness of a sheet of paper side view from a distance of almost 161 kilometers (100 miles).
"Researchers by GP-B had to invent entirely new technologies to make this possible, "added Will.
They developed a satellite-free" drag "that could touch the outer layers of the Earth's atmosphere without disturbing the gyroscopes. solved the problem of preventing the Earth's magnetic field penetrates inside the ship. also invented a device capable of measuring the spin of a gyroscope without touching it. For more information about these technologies, please consult History of Science @ NASA: "A corner where everything is (almost) perfect."
Perform the experiment was an exceptional challenge. But after a year of capture data and almost five years of analysis, researchers from the GP-B appear to have succeeded.
"We measured a geodetic precession of 6.600 about 0.017 seconds of arc and a frame-dragging effect of 0.039 about 0.007 seconds of arc," says Everitt.
For readers who are not experts on relativity: the geodetic precession is the wobble caused by the static mass of the Earth (the slit in space-time) and the frame-dragging effect is the wobble due to rotation of the Earth (the twisting of space-time.) Both values \u200b\u200bcoincide precisely with the predictions of Einstein.
"In the opinion of the committee that I chair, this effort was truly heroic. We are left speechless, "says Will.

artist's concept of space-time around a black hole. Photo Credit: Joe Bergeron of Sky & Telescope magazine.
The results of the Gravity Probe B has given physicists a renewed confidence that the strange predictions of Einstein's theory is indeed correct, and that these predictions can therefore be applied in other cases. The kind of space-time vortex that exists around the Earth is duplicated and expanded elsewhere in the cosmos, such as around massive neutron stars, black holes and active galactic nuclei.
"If you try to spin a gyroscope in the severely distorted region of space-time around a black hole," says Will, "would not make a precession gently for a fraction of a degree. Would be shaken violently and could even turn around ".
In black hole binary systems, ie, where a black hole orbit to another, the same black holes are spinning and therefore behave as gyroscopes. Imagine a system of black holes orbiting each other, swaying and even continuously turning around! That's the kind of thing that general relativity predicts that the GP-B confirms that indeed may occur.
scientific legacy of the GP-B is not limited to general relativity. The project also touched the lives of hundreds of young scientists:
"Because the project was led by a university, many students could participate in it," says Everitt. "More than 86 doctoral dissertations at Stanford and 14 other universities were awarded to students who worked on the project of the GP-B. It also involved several hundred college students and 55 high school students and even an astronaut and physicist Sally Ride Eric Cornell, who won the Nobel Prize. "
Funding for NASA's Gravity Probe B began in the fall of 1963. That means say, Everitt and his colleagues have been planning, promoting, building, operating and analyzing data from the experiment for more than 47 years. It is undoubtedly a huge effort.
What's next?
Everitt remembers some advice he gave her thesis advisor Patrick MS Blackett, who won the Nobel Prize: "If you can not think of what physics research then invent a new technology and that will lead to new physics."
"Well," says Everitt, "invented 13 new technologies for Gravity Probe B. Who knows where they take us?"
After all, this could be just the beginning of this epic