If they do exist, they could lead to interstellar travel--indeed, to instantaneous access to points at the far range of the universe. They would also confirm both general relativity and the discovery of exotic matter. But curiously little thought seems given to detecting wormholes, or theorizing about how small, stable ones might have evolved since the early universe. Several co-authors and I proposed using the Massive Compact Halo Object (MACHO) searches to reveal a special class--"negative mass" wormholes--since they would appear as sharp, two-peaked optical features, due to gravitational lensing (Physical Review D 51, p3117-20, 1995) So far all the two peaked cases found have been attributed to binary stars or companion planets, though the data fits are not very close.
Surely there could be other ways to see such exotic objects. Some thought and calculations about wormhole evolution might produce a checkable prediction, as a sidelight to an existing search. Further thought is needed about the implications that extra dimensions from string theory will have on wormholes. It seems theoretically plausible that the inflationary phase of the early universe might have made negative mass string loops framing stable Visser-type wormholes.
Perhaps wormholes do not exist. A plausible search that yielded nothing would still be a result, because we could learn something about the possibility of exotic matter. A positive result, especially detection of a wormhole we could reach with spacecraft, could change human history.
Gregory Benford is a professor of physics and astronomy at the University of California, Irvine. His most recent nonfiction is Deep Time.