increasingly dispersed. The sky would be dotted with fewer and fewer spirals, ellipticals, and other ensembles of stars. Eventually all that could be seen, even with a telescope, would be the local group of galaxies; the others would lie beyond visual range. Consequently, any alien signals sent by remote extragalactic civilizations would never reach us. We’d be cosmic hermits, separated from other systems, until all the stars in the Milky Way burned out—turning into white dwarfs, neutron stars, and black holes. When doomsday finally arrived, it would be extraordinarily dark and lonely.

The road to a Big Rip would greatly exacerbate this isolation. The lambda force would pull the universe apart at breakneck speed, like a glutton attacking a bucket of chicken wings. Sooner than in the previous scenario, signals would be unable to span the increasingly formidable gaps. Hence, if we have any chance of intergalactic communication we’d best attempt it expeditiously; otherwise, we may someday wake up and find that it is too late.

If it seems ambitious to talk about possible events billions of years hence, you’ve perceived correctly. With the ease of meteorologists forecasting one or two days ahead, cosmologists feel comfortable projecting eons into the future. Yet if you read the fine print, many of the predictions are based on the proposition that the known laws of nature, as measured from Earth, must hold true for all places and all times.

But what if the principles of nature themselves evolve, like the stunning metamorphoses of “Darwin’s finches” on the Galapagos Islands? Unless we perfectly understood these changes, we’d be in little position to make projections. Indeed, some of the exciting new cosmological theories posited to resolve the dark-matter and dark-energy riddles are based on the astonishing notion that nature’s very “constants” could alter throughout the ages.

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