On January 10, 2009, at 10:33 PM Pacific Time (06:33 UTC on January 11), Hal Finney posted two words to Twitter:
Quote from: Hal Finney on January 11, 2009, 6:33:00 AM UTC
Running bitcoin
The message is widely treated as the first tweet about Bitcoin. What it announced was the only fact it carried — that the Bitcoin software was, at that moment, running on a machine other than Satoshi’s.
Finney was not a random first observer. As the RPOW author and a longtime PGP developer, he was already inside the territory the Bitcoin whitepaper addressed — distributed proof-of-work, cryptographic protocols for digital cash, hashcash heritage. When Bitcoin v0.1 was publicly released, he was among the first readers equipped to follow the design end to end and run it. He did, from his home in Santa Barbara, California.
The tweet received virtually no reaction. The word bitcoin did not yet name anything to the readers scrolling past it; the proof-of-work network had no public traffic for them to verify against. The post became iconic only retroactively, after the system it announced had a public history large enough for readers to recognize what those two words had marked.
At the moment the tweet was posted, the known Bitcoin network shifted from one node to two. A peer-to-peer system requires at least two peers to function as one, and until Finney brought his node online the design’s distributed properties were structural rather than active. The two-word post is the shortest possible record of that change: a network with a second known operator.
Two days later, on January 12, 2009, the first Bitcoin transaction crossed the network: Satoshi sent ten BTC (TX f4184fc596403b9d638783cf57adfe4c75c605f6356fbc91338530e9831e9e16) from his node to Finney’s. The tweet had made the precondition for that send visible — a second operator, named, reachable, running the same software — without itself causing it.
The tweet was two words. Finney’s documented involvement with Bitcoin extended from that moment for five and a half years, until his death in 2014 from ALS. The shortest declaration any non-Satoshi participant made about the system sits at the entrance of one of the longest and best-documented engagements with Bitcoin in its early history.