Britain is rejoining the European Union’s $100 billion science-sharing program Horizon Europe, the two sides announced Thursday, more than two years after the country's membership became a casualty of Brexit. British scientists expressed relief at the decision, the latest sign of thawing relations between the EU and its former member nation. After months of negotiations, the British government said the country was becoming a “fully associated member” of the research collaboration body U.K.-based scientists can bid for Horizon funding starting Thursday and will be able to lead Horizon-backed science projects starting in 2024.