Wide binary stars are like two dancers holding hands but standing at opposite ends of the hall. Their bond is weak, and any passerby can break them apart. Astronomers found 26 such pairs and tested how tightly they hold on.
It turned out that 12 pairs dance by Newton's rules: their orbits can be calculated like those of planets around the Sun. But three pairs move too fast. The difference in speeds is such that no ordinary gravity can hold them.
The scientists ruled out other explanations: these pairs have no invisible third star or massive planet. Most likely, they were separated: either by a passing star or by the tidal forces of our Galaxy. This means such pairs cannot be considered isolated: their history is more complex than it seems.
Galaxy is not an empty hall but a crowd where anyone can bump into the dancers. And three pairs seem to have already let go of each other's hands.
The distance between stars in such pairs is thousands of times greater than from the Sun to Earth.
In Isaac Asimov's novel "The Gods Themselves," two universes exchange matter, much like wide binary stars exchange gravity.