Ocean crossing

In 1492 a Spanish expedition led by Columbus reached the Caribbean. Norse sailors had reached North America centuries earlier and did not start a lasting link. This voyage did, because it plugged the Americas into European states that already had ships, guns, writing, and a hunger for routes to Asia.

The contribution to the technology timeline is a single trading world. Crops move: potatoes and maize to the old world, wheat and sugar the other way. So do diseases, which kill a large share of the people in the Americas. Silver from American mines changes prices in Europe and China. Later industry sits on this wider map of materials and markets.

It is not a moral success story, and it is not the invention of navigation. The compass, the astrolabe, and the caravel already existed. 1492 is the year the Atlantic stops being a barrier between two populated worlds.

The timeline includes it because technologies after this spread across empires, not only across a continent.