A physics experiment to be carried out on the International Space Station, which is in the planning stages, may help formulate a "Grand Unified Theory of Everything".
Patrick L. Barry, NASA Science News. Translated by Dikla Oren
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Sooner or later, the era of Einstein, like the era of Newton before him, will come to an end. Most scientists believe that a revolution in the world of physics, which will change our basic ideas about reality, is inevitable. Now we are in the middle of a race between several theories, competing among them who will inherit the throne.
Among these theories are some hard-to-grasp ideas, such as an eleven-dimensional universe; theories in which the global "constants" (such as the global gravitational constant) change from place to place and from time to time and remain truly constant only in an invisible fifth dimension; Extremely tiny oscillating strings, which constitute the fundamental components of the universe and theories in which the fabric of space-time is not smooth and continuous, as Einstein believed, but is divided into discrete and tiny portions of extremely small size. Experiments will ultimately determine who is the winner.
Scientists at NASA's Jet Propulsion Laboratory (JPL) are working on developing a new idea for an experiment that will test the predictions of Einstein's theory of relativity with greater precision than ever before. Their mission, which essentially uses the solar system as a giant laboratory, will help narrow down the field of competing theories and bring us one step closer. for the next great revolution in physics.
This may not mean much to most people, but a deep rift has long accompanied our basic understanding of the universe. There are two ways of explaining the nature and behavior of space, time, matter and energy. One is Einstein's theory of relativity, and the other is the "standard model" of quantum mechanics. Both of these ways are successful. The GPS system (Global Positioning system), for example, relies on the theory of relativity. Computers, long-distance electronic communication technologies and the Internet, on the other hand, are derived from quantum mechanics.
Deflection of starlight by the Sun's gravity
The problem is that these two theories are like two different languages, and no one knows how to translate one into the other. Relativity explains gravity and the movement of bodies by uniting space and time into an elastic and dynamic four-dimensional fabric of space-time, which is warped by its energy content (mass is a form of energy, therefore it creates gravity by warping space-time). Quantum mechanics, on the other hand, assumes that space and time create a flat and eternal "stage" on which the plots of several families of particles unfold. These particles can move back and forth in time (which relativity does not allow), and the interactions between these particles provide an explanation for the fundamental forces of nature - apart from the extraordinary gravity.
This equal struggle between the two theories has been going on for decades. Most scientists assume that somehow in the end a unifying theory will be developed, which will include the two and show how the truth in each of them fits into one framework of reality. Such a comprehensive theory will have a profound effect on our knowledge of the birth, development and fate of the universe.
Slava Torishev, a scientist at JPL, and his colleagues came up with the idea of using the International Space Station and two mini-satellites, orbiting on the far side of the Sun, to test the theory of relativity with greater precision than ever before. Their idea, developed in part with funding from NASA's Office of Biological and Physical Research, will be so sensitive that it will be able to reveal flaws in Einstein's theory, providing for the first time the information needed to distinguish between proposed theories that have some connection with reality and those that are nothing more than theories.
The experiment, called the Laser Astrometric Test of Relativity (LATOR - Laser Astrometric Test Of Relativity), will test how gravity from the Sun deflects laser beams that will be emitted by the two satellites. Gravity deflects the path of light, because it distorts the space through which the light passes. To understand the distortion of space and time by gravity, try to imagine a flat sheet of rubber, stretching under the weight of objects placed on it, similar to the sun. The hole that will be created in the sheet will cause the object, passing near the sun, to deviate slightly from its path (also for objects with mass such as light).
In fact, Sir Arthur Eddington's measurement of the offset of a star's light by the Sun during a solar eclipse in 1919 was the first test of general relativity. In cosmic terms, the Sun's gravity is relatively weak; The path of a beam of light, approaching the sun, will only deviate by about 1.75 seconds of arc (a second of arc is 1/3600 of a degree). Within the limits of the accuracy of his measuring equipment, Eddington showed that light was indeed deflected in this way - thereby disproving Newton's theory.
LATOR will measure this offset with a precision a billion times higher than the Eddington experiment and 30,000 times higher than the most precise measurement to date: the random measurement using signals from the Cassini spacecraft on its way to Saturn.
"I think LATOR will be an important advance for the physics of the fundamentals of the universe," says Clifford Will, a professor of physics at the University of Washington who has made several major contributions to post-Newtonian physics and is not directly involved in the LATOR project. "We must continue to strive for more accurate measurements of the predictions of general relativity, simply because any deviation from them will inform us of the existence of new physics, of which we were previously unaware."
The experiment will be conducted as follows: two small satellites, each about one meter wide, will be launched into orbit around the sun at approximately the same distance as the Earth. The pair of satellites will orbit the Sun more slowly than the Earth, so that after about seventeen months the Earth and the two satellites will be on opposite sides of the Sun. Although the distance between the two satellites will be about five million kilometers, the angle between them, as seen from Earth, will be tiny, about one degree. Together, the two satellites and the Earth formed a triangle, whose sides are laser beams, one of which will pass close to the Sun.
Torishev intends to measure the angle between the two satellites using an interferometer (interference meter), which is on the International Space Station. An interferometer is a device that combines two beams of light. By measuring the interference between the two satellites, the interferometer can measure the angle between the two satellites with great precision: about ten billionths of a second of arc, or 0.01 microseconds of arc. When the accuracy capabilities of the other devices are also taken into account, the overall accuracy obtained for measuring the curvature of the laser beam's trajectory is about 0.02 microseconds per arc.
"Using the International Space Station gives us several advantages," Turishev explains. "First of all, it is outside the disturbances of the Earth's atmosphere, and it is also large enough that we can put the two interferometer lenses far apart (each lens at the far end of the solar panel beams), which contributes to the resolution and accuracy of the measurements."
A precision of 0.02 microarcseconds will allow us to reveal deviations from Einstein's relativity predicted by the ambitious unified theories. The predictions offered by these theories include deviations ranging from 0.5 microarcseconds to 35 microarcseconds. A match between the LATOR results and the predictions of one of the theories will advance each of them. If no deviation from Einstein's theory is found, most of the contending theories - along with their eleven dimensions, discrete space, and impermanent constants - will suffer a severe blow and "move out of the world" into the great library storeroom in the sky.
Since the mission only requires existing technologies, Turishev says that the LATOR will be ready for operation as early as 2009 or 2010. It is possible, therefore, that it will not take long until the close race in physics is decided, and a new theory of gravity, space and time will inherit the throne.
Link to the article on the NASA news website
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