This is what a trade war looks like. Trump has been standing his ground on tariffs (he's even had a law drafted called the FART Act — U.S. Fair and Reciprocal Tariff Act). And now the retaliation is rolling out — from Canada, China and from the EU. Canada's tariffs took effect this week. China's retaliatory package of $34 billion in tariffs is set to start on Friday. Super smart Dartmouth economics professor Doug Irwin gives us some big picture history, theory and context. Like: if you're gonna start a trade war, is a strong economy actually a good time to do it? Plus, two entrepreneurs tracking a shipment of their products from China explain why they're freaking out.