(These terms were defined in the chapter on Orbits and Gravity.) The gravitational effects (perturbations) of the other planets on Mercury produce a calculable advance of Mercury’s perihelion. Mercury has a highly elliptical orbit, so that it is only about two-thirds as far from the Sun at perihelion as it is at aphelion. Most importantly, it had already been measured.
It turned out that the difference was subtle, but it was definitely there. Einstein wondered if the distortion might produce a noticeable difference in the motion of Mercury that was not predicted by Newton’s law. Of the planets in our solar system, Mercury orbits closest to the Sun and is thus most affected by the distortion of spacetime produced by the Sun’s mass. The change from orbit to orbit has been significantly exaggerated on this diagram. Mercury, being the planet closest to the Sun, has its orbit most affected by the warping of spacetime near the Sun. In Mercury’s case, the amount of rotation (or orbital precession) is a bit larger than can be accounted for by the gravitational forces exerted by other planets this difference is precisely explained by the general theory of relativity. Mercury’s Wobble: The major axis of the orbit of a planet, such as Mercury, rotates in space slightly because of various perturbations. Nevertheless, Einstein was able to demonstrate one proof of his theory that could be found in existing data and to suggest another one that would be tested just a few years later.įigure 1. In familiar territory, therefore, the differences between the predictions of the two models are subtle and difficult to detect. When the distorting mass is small, the predictions of general relativity must agree with those resulting from Newton’s law of universal gravitation, which, after all, has served us admirably in our technology and in guiding space probes to the other planets. (For smaller masses, it required measuring techniques that would not become available until decades later.) This was quite a challenge because the effects of the new theory were apparent only when the mass was quite large. Like all new ideas in science, no matter who advances them, Einstein’s theory had to be tested by comparing its predictions against the experimental evidence. It was a new theory of gravity, in which mass determines the curvature of spacetime and that curvature, in turn, controls how objects move. What Einstein proposed was nothing less than a major revolution in our understanding of space and time. Provide examples of evidence for light rays being bent by massive objects, as predicted by general relativity’s theory about the warping of spacetime.
Describe unusual motion of Mercury around the Sun and explain how general relativity explains the observed behavior.By the end of this section, you will be able to:
0 kommentar(er)
