How to build a multiverse
THE heavens do not lend themselves to poking and prodding. Astronomers therefore have no choice but to rely on whatever data the cosmos deigns to throw at them. And they have learnt a lot this way. Thus you can even (see article) study chemistry in space that would be impossible in a laboratory. Some astronomers, though, are dissatisfied with being passive observers. Real scientists, they think, do experiments.
It is impossible—not to mention inadvisable—to get close enough to a star or a black hole to manipulate it experimentally. But some think it might be possible to make meaningful analogues of such things, and even of the universe itself, and experiment on those instead.