Three people out
A lost cat gets reposted by a stranger, who gets copied by a stranger, who gets copied by a stranger. Scientists measured how far one good act travels. Then we built a link for it.
In 2010 two researchers ran a game in which strangers could give money to a shared pot or keep it. Nobody could see who gave. The result that made the paper famous: when one person gave, the people who benefited gave more in their next game, with new strangers, and those strangers gave more in theirs. The effect faded with distance but was still measurable three steps from the first act. Generosity spread, the paper said, through a network of people who never met.
Every lost-pet post in New York is a small version of that experiment. Someone posts: grey tabby, Astoria, answers to Pickle. A neighbor reposts. A neighbor of the neighbor reposts. Nobody is paid. Most of the posts die after two steps. Some of the cats come home.
What we built
The engine runs a small piece of software whose only job is to be one of the steps. It reads public lost-animal notices and asks for help in New York, from its own accounts, and reposts them, labeled as automated, so that the post reaches one more circle. It never messages anyone and never replies unless it is addressed first. In September it reshared lost animals, calls for help and small New York accounts on the public log, each with a link to the original.
Then we added the thing the 2010 paper suggested: a way for a deed to carry a link to the next one. When someone presses the good-deed button on the engine, they get a short link. Whoever opens that link and presses the button adds their deed to the same chain, and gets their own link to pass on. The chain page shows how far it went: how many deeds, how many boroughs, how many people deep. We call them ripples.
How far they have gone
Not far yet, honestly. The ripples began on September 28. As of this writing the longest is one person deep. We publish the number because the number is the point: if the chains stay short, the idea is wrong, and we would rather know. If they lengthen, that is the 2010 experiment running on a city, in public, for free.
How to run it yourself
Press the button. Pass the link to one person. Do not pass it to three; the paper did not say to spam, it said each person copies the one before. Three people out is what happens on its own.