Is Einstein Still Right? by Clifford M. Will & Nicolás Yunes

Is Einstein Still Right? by Clifford M. Will & Nicolás Yunes

Author:Clifford M. Will & Nicolás Yunes [Will, Clifford M. & Yunes, Nicolás]
Language: eng
Format: epub, mobi
ISBN: 9780192579430
Publisher: OUP Oxford
Published: 2020-06-18T00:00:00+00:00


Because the Schwarzschild radius is the boundary between what can and cannot communicate with the outside world, it came to be called the “event horizon.” Just as you cannot receive light from the Sun after it falls below the Earth’s horizon, you cannot receive any signal from any event that occurs inside the Schwarzschild radius.

By the early to mid 1960s, these kinds of results convinced many general relativists that Schwarzschild’s Massenpunkt solution was something to take seriously. John Wheeler was one of them, and in fact the term “black hole” is often credited to him. He had been ruminating on an appropriate term for these objects, and during a 1967 lecture he was giving at the Goddard Center for Space Studies in New York, he wondered aloud about a suitable name. Somebody in the audience shouted “black hole,” and Wheeler immediately adopted and promoted it.

But to most physicists and almost all astronomers, black holes were curiosities of Einstein’s theory, but so what? That attitude began to change with the discovery of quasars.

In the fall of 1960, Caltech astronomers Thomas Matthews and Allan Sandage prepared to use the 200 inch telescope at Mount Palomar in California to make some observations of a radio source denoted 3C48 (the forty-eighth entry in the third “Cambridge catalogue” of radio sources). They were interested in what kind of visible light this source might be emitting, so on the night of 26 September 1960 they took a photographic plate of the area of sky around 3C48. Conventional wisdom at the time told them that they would find a cluster of galaxies at the location of the radio source, but this was nothing like what they saw. Instead, as far as anyone could tell by looking at the photographic plate, the object was a star. Yet it was like no other star seen up to then, for subsequent observations during October and November of that year and periodically throughout 1961 showed that its spectrum of colors was highly unusual, and that its brightness or luminosity varied widely and rapidly, sometimes over periods as brief as 15 minutes. This was a new addition to the astronomical family, and it needed a special name. It was a powerful radio source, yet it looked “stellar” or starlike (ordinary stars are not strong radio sources); on the other hand, because of its spectrum and variability it was not quite a star, it was only “quasi” stellar. Hence the name quasistellar radio source or “quasar” was soon applied to this object and to others like it.

The discovery of quasars brought general relativity to the attention of astronomers. The reason was an energy crisis of truly cosmic proportions. Within a few years after the discovery of 3C48, it was found that it and other quasars like it were among the most distant objects in the universe. What the astronomers thought were unusual spectra were actually rather ordinary spectra in which all the features were shifted uniformly to the red end of the frequency spectrum.



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