How, if some day or night a demon were to sneak after you into your loneliest loneliness and say to you, “This life as you now live it and have lived it, you will have to live once more and innumerable times more; and there will be nothing new in it, but every pain and every joy and every thought and every sigh and everything immeasurably small or great in your life must return to you—all in the same succession and sequence—even this spider and this moonlight between the trees, and even this moment and I myself. The eternal hourglass of existence is turned over and over, and you with it, a dust grain of dust.” Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus? Or did you once experience a tremendous moment when you would have answered him, “You are a god, and never have I heard anything more godly.” If this thought were to gain possession of you, it would change you, as you are, or perhaps crush you. The question in each and every thing, “Do you want this once more and innumerable times more?” would weigh upon your actions as the greatest stress. Or how well disposed would you have to become to yourself and to life to crave nothing more fervently than this ultimate eternal confirmation and seal?
The above quote, taken from The Gay Science, includes one of the first mentions of Nietzsche’s idea of the “eternal recurrence,” which as we can see from the context is more of a thought-experiment litmus test than a scientific postulation. You can test the meaning of any action or thought by imagining doing that action or thinking that thought over and over again in the same way for eternity.
Perhaps every action or thought becomes meaningless after enough repetition, and perhaps that is the point Nietzsche is ultimately attempting to make. Nevertheless, this hypothetical situation should make one pause to evaluate the usage of one’s precious time, as counterintuitive as it may at first glance seem, considering that the experiment itself rests on the imagining of unlimited revolutions of the hour glass.
Meanwhile, actual scientific theories are beginning to confirm this unscientific one; as this, this, and many other new articles suggest, the universe could have existed before the Big Bang, and thus could be expanding and contracting ad infinitum. Or, as Ecclesiastes wrote, “there is no new thing under the sun.”
Stephen Hawking, who thinks time was created in the Big Bang 15 billion years ago, as the prevailing theory holds, gave one of my favorite quotes of all time about the universe’s possible end: “When I gave a lecture in Japan, I was asked not to mention the possible re-collapse of the universe, because it might affect the stock market.”