NOTES
Inertial navigation was developed, with enormous effort, for a specific need, and won out against alternatives in spite of the opposition of smart scientists.
It's easy to imagine tiny changes in the 1950s that would result in inertial navigation not being developed, or being developed in a different way, resulting in huge changes, as the balance of the cold war changes, intellectual energies that would have been devoted to developing IN go elsewhere, and spinoffs go away, replaced by other spin-offs from whatever other technologies take the place of IN. And to the people who experienced that history, everything would seem as natural as our history appears to us.