Oliver Morton in More Intelligent Life:
In the far reaches of the sky there are sun-bright discs as wide as solar systems, their hearts run through by spears of radiation that outshine galaxies. The energies that feed these quasars beggar all metaphor, and their quantification seems all but meaningless. What does it serve to know that they are converting matter to energy at a rate that equates to the complete annihilation of a planet the size of the Earth ten times a second? Or that all the fires of the sun, from its birth to its death, would be a few weeks’ worth of work to one of them? No human sense can be made from so inhuman a scale. Boggle, and move on. Or stop, and appreciate that for all their grandeur, quasars are actually rather hard to see. Not one of them is close enough for the naked eye to pick out; even through the largest telescopes their mighty discs are but points of light. Again, the numbers are incomprehensibly enormous: billions of light years, when the longest trip taken by humans, to the Moon and back, is just a few light seconds. Yet here is a human connection that makes something wonderful of the spectacle. The billion-year journeys of the quasars’ light end at human telescopes. And there this far-flung light is not merely absorbed, but also understood.
…In 1960 no one had knowingly observed a quasar in any wavelength whatsoever. By 1969 hundreds were known, and a detailed theory of black holes had been developed which accounted for the quasars’ remarkable properties. Matter pulled towards a large black hole is heated to extraordinary brightness by friction; from the swirling disc thus formed a constant stream of matter passes into the hole’s oblate “ergosphere” whence some is squirted out with even greater energy in jets that protrude from the quasar’s poles. That men and women can, in a few short years, take tiny smidges of data from often ill-behaved instruments around the world and judiciously combine them with a wide range of physical theory – including the demanding mathematical subtleties of general relativity – to form an account of something not only unimagined but unimaginable to anyone without the new mental equipment this joint endeavour provided: that seems to me a source of wonder greater than the vastest of astronomical numbers.