Immutable mobiles are a concept most fully developed by
Bruno Latour in discussing how
information is passed between agents. A newspaper is a good example of an immutable mobile. It is easily transported between people, but has some permanence to it.
Latour tells a story about French explorers in Southeast Asia. The explorers stop and ask the local natives if the bit of land they are on is an island or a peninsula. In response, the oldest of the natives drops to the sand and draws a map of the island. His son sees the tide is about to wash out the map, so retraces it in the European's logbook. However, the natives here do not understand the power of immutable mobiles.
What makes the immutable mobile powerful is that it allows coalition building around an idea. If the French explorer wants his fellow explorers to believe the land he saw was an island, he can show his map. More importantly, that map can be compared against other maps to show discrepancies. This does not mean exact information emerges, or that the natives know less about the land they live on, what it means is that the concept of "this land is an island" is vastly accelerated by the map as an immutable mobile.