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Physicists generally agree that the atoms in superfluid helium-4 is not a Bose–Einstein condensate in the original sense of the term because its atoms interact too strongly. Reppy studied an exception: tiny amounts of helium trapped in nanometer-sized pores of a spongelike glass called Vycor. Even though the pores keep its atoms too far apart to jostle one another much, the helium still behaves like a three-dimensional fluid. In 1983 Reppy and colleagues reported results that suggested the helium was sloshing through the glass as a true Bose–Einstein condensate.