"That heat would thus solve the great problem that faced us; it would halt the doom that was closing down on us. For that heat would so warm Neptune, that we could go back again and take up our existence once more upon it free from all peril, could live again in that great compartment-city that covered all Neptune. And Triton, too, would be livable, then. For the great roofs that we had erected around Neptune and its moon would tend to make of both worlds great hot-houses in effect, the sun's or suns' heat being able to penetrate down through those roofs. And with those enclosing roofs about us, and with the two new suns close, we could live on in safety. For the enclosing roofs themselves would prevent any inconvenience from the fact that Neptune now and then would be farther from the two suns than at other times, those great roofs keeping a constant warmth upon Neptune and its moon. "Thus all the great peril that confronted us would be thrust back, and we could live once more on Neptune, more warm and comfortable there than ever before; we could pour back once more to our mighty world that lay now dead and cold and deserted--could do all this, if the sun _did_ divide into a double star. Yet what hope was there that this could happen? We knew that the reason other suns of the universe divide into double or multiple stars is because they have reached a rate of rotatory speed that makes it impossible for them longer to hold together. For when a sun is spinning its mass tends to split up by its own centrifugal force, just as a turning wheel, and the faster the sun spins the greater grows its centrifugal force, the greater its tendency to split. And then at last that rate of spin grows so great, and its centrifugal force is such that its mass can no longer hold together, and fission takes place, the sun dividing into two or three or even more stars, that push apart from each other. But what chance was there of the sun doing this? For the sun, we knew, rotated at the speed of one turn in 25 days, at its equator, and to split it would have to be rotating at a speed of one turn in an hour. That meant that it would be unthinkable eons before the sun's rotatory speed would have increased to that point. For though a sun's rotatory speed does increase as time passes, due to the shrinkage of its mass, it increases so infinitely slowly that it would be eons, indeed, before the sun's rate of spin would be so great as to cause its division. And thus there seemed small hope indeed in that plan. * * * * *