Silicon Valley firms have poured billions of dollars into artificial intelligence. But a new cheap AI model from DeepSeek, a Chinese start-up, has sent shockwaves through the stockmarket. Our correspondent explains why investors are rattled. Canada’s remote indigenous communities are struggling to install solar power (9:37). And why you should lift weights (18:25).Listen to what matters most, from global politics and business to science and technology—Subscribe to Economist Podcasts+For more information about how to access Economist Podcasts+, please visit our FAQs page or watch our video explaining how to link your account.  Hosted on Acast. See acast.com/privacy for more information.