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" And so from then onwards, Daniel understood that the point of this grueling sundial project was not merely to plot the curve but to understand why each curve was shaped as it was. To put it another way, Isaac wanted to be able to walk up to a blank wall on a cloudy day, stab a gnomom into it, and draw all of the curves simply by knowing where shadow would pass. This was the same thing as knowing where the sun would be in the sky and that was the same as knowing where the Earth was in its circuit around the sun, and in its daily rotation. Though as months went on, Daniel understood that Isaac wanted to be able to do the same thing even if the blank wall happened to be situated on, say, the moon that Christiaan Huygens had lately discovered revolving around Saturn. Exactly how this might be accomplished was a question with ramifications that extended into such fields as would Isaac, and Daniel for that matter, be thrown out of Trinity College? Were the Earth and all the works of man nearing the end of a long, relentless decay that had begun with the expulsion from Eden, and that would very soon culminate in the apocalypse? Or might things actually be getting better, with the promise of continuing to do so? Did people have souls? Did they have free will? "
― Neal Stephenson
