51% Doomsday: The Moment a Single Mining Pool Could Kill Bitcoin Overnight

A single mining pool crossing 51% of Bitcoin's hashrate could trigger market, political and miner reactions, and the 2014 episode when GHash.io briefly held a majority is offered as a precedent. Cornell researchers Eyal & Sirer documented GHash controlling the majority for about 12 hours, and Bitcoin's spot price fell roughly 5%, from US$633 to US$600, before GHash pledged never to exceed 39.99%. As of 11 June 2025, Foundry USA held 34% and Antpool 20%, combined 54%, and a 2026 scenario of Foundry reaching 52% is presented as hypothetical.