![]() 24.5: Black Holes Theory suggests that stars with stellar cores more massive than three times the mass of the Sun at the time they exhaust their nuclear fuel will collapse to become black holes.When light or other radiation emerges from a compact smaller remnant, such as a white dwarf or neutron star, it shows a gravitational redshift due to the slowing of time. Experiments on Earth and with spacecraft have confirmed this prediction with remarkable accuracy. 24.4: Time in General Relativity General relativity predicts that the stronger the gravity, the more slowly time must run.For example, general relativity predicts that light or radio waves will be deflected when they pass near the Sun, and that the position where Mercury is at perihelion would change by 43 arcsec per century even if there were no other planets However, in the stronger gravity of the Sun, general relativity makes predictions that differ from Newtonian physics and can be tested. 24.3: Tests of General Relativity In weak gravitational fields, the predictions of general relativity agree with the predictions of Newton’s law of gravity.Light must change its path near a massive object not because light is bent by gravity, but because spacetime is. The distribution of matter determines the curvature of spacetime other objects (and even light) entering a region of spacetime must follow its curvature. 24.2: Spacetime and Gravity By considering the consequences of the equivalence principle, Einstein concluded that we live in a curved spacetime.According to this principle, there is no way that anyone or any experiment in a sealed environment can distinguish between free fall and the absence of gravity. 24.1: Introducing General Relativity Einstein proposed the equivalence principle as the foundation of the theory of general relativity.As we continue our voyage into the universe, we will discover that black holes are the key to explaining many mysterious and remarkable objects-including collapsed stars and the active centers of giant galaxies. But the truth about black holes is almost stranger than fiction. \( \newcommand\)įor most of the twentieth century, black holes seemed the stuff of science fiction, portrayed either as monster vacuum cleaners consuming all the matter around them or as tunnels from one universe to another.
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