If such a thing had happened once, it must surely have happened many times in this galaxy of a hundred billion suns.
Interpretation
The quote suggests that extraordinary events in the universe are likely to recur, given the vastness of space and time.
Arthur C. Clarke's quote reflects on the immense scale of the universe, indicating that if a rare or remarkable event occurred once, it is plausible it has occurred multiple times throughout the cosmos. It invites contemplation about the possibilities of life and experiences in a galaxy with such a phenomenal number of stars, encouraging an appreciation for the complexity and mystery of the universe.
In practice
During a lecture about astronomy, one could use this quote to emphasize the vast possibilities in the universe.
Nowhere in space will we rest our eyes upon the familiar shapes of trees and plants, or any of the animals that share our world. Whatsoever life we meet will be as strange and alien as the nightmare creatures of the ocean abyss, or of the insect empire whose horrors are normally hidden from us by their microscopic scale.
As our own species is in the process of proving, one cannot have superior science and inferior morals. The combination is unstable and self-destroying.
It has yet to be proven that intelligence has any survival value.
The best measure of a man's honesty isn't his income tax return. It's the zero adjust on his bathroom scale.
It was the mark of a barbarian to destroy something one could not understand.
My favorite definition of an intellectual: 'Someone who has been educated beyond his/her intelligence'.
If any human being earnestly desire to push on to new discoveries instead of just retaining and using the old; to win victories over Nature as a worker rather than over hostile critics as a disputant; to attain, in fact, clear and demonstrative knowlegde instead of attractive and probable theory; we invite him as a true son of Science to join our ranks.
We must trust to nothing but facts: These are presented to us by Nature, and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation.
One in 200 stars has habitable Earth-like planets surrounding it - in the galaxy, half a billion stars have Earth-like planets going around them - that's huge, half a billion. So when we look at the night sky, it makes sense that someone is looking back at us.
But just as astronomy succeeded astrology, following Kepler's discovery of planetary regularities, the discoveries of these many principles in empirical explorations of intellectual processes in machines should lead to a science, eventually.
We went to the Moon as technicians; we returned as humanitarians.
The question now at issue, whether the living species are connected with the extinct by a common bond of descent, will best be cleared up by devoting ourselves to the study of the actual state of the living world, and to those monuments of the past in which the relics of the animate creation of former ages are best preserved and least mutilated by the hand of time.
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