A retelling of 'The Last Question,' by Asimov and 'Island,' by rorscharchblot. Beta by the redoubtable Casse.
Between Hermione's meticulously researched spells and carefully crafted theoretical models, and Luna's continual state of creative inspiration, there was no reason to expect a failure in principle. Tracy and Hannah had been excellent teachers - Harry was confident that he understood the basics of the project. The best part was that once the fundamental spells were cast, their new home should need little in the way of maintenance. It would stabilize quickly, and soon would be completely self-sustaining. The new habitat would expand naturally, vastly outpacing their own population growth.
They would be safe, finally, from the muggles's science.
They were lined up behind him, waiting on brooms and magic carpets: families and friends staying close to each other. This first wave of the exodus numbered tens of thousands. Every colonist had brought literally hundreds of tons of supplies, carefully packed and protected against any conceivable problem. The second wave of magicals, mostly children, was awaiting confirmation of success before making the leap to follow them. Many more waves were planned. Outside of the deep-penetration moles left behind specifically to find and hide future muggleborn wizarding children, in a decade there would be no magical beings, animals, plants, insects, or items left on Earth.
They had found no hints at all that any magical person had ever even considered building a refuge on this scale. Perhaps only someone raised in the late 20th-century muggle world could conceive of it. After all, only in the last few decades had the concept of space travel really become part of a child's everyday life.
To Harry and Hermione, leaving earth entirely was simply the logical next step. There was no way the traditional methods of hiding the Wizarding world were going to work much longer. Muggle governments and statisticians alike were already starting to notice the numbers of children who simply dropped out of sight.
Harry took a deep breath, and centered himself. The first spell was actually the most difficult and complex step. Quietly, he started the chant - mostly a request for guidance, in fact. He felt the spell catch, weaving itself through the strands of the universe, then locking solidly on the other side.
Using occlumency training combined with deep meditation, Harry calmly stepped out of his body and through the portal. There was no reason to delay: Harry thought, as clearly as he could, the foundation equations. The sudden explosion of *possibility* was an unexpected delight. With joy, and love, Harry thought, "Let there be light."
And there was light -