If you're new to crypto, here's one idea you might not have heard before: Bitcoin (CRYPTO: BTC) could be ready to challenge the U.S. dollar as the world's reserve currency. In his annual letter to investors this year, BlackRock (NYSE: BLK) CEO and Chairman, Larry Fink, suggested that Bitcoin had the potential to replace the U.S. dollar as the world's reserve currency. The first is the entire notion of what a reserve currency should be, and what role it plays in the global economy.