![The Economist Radio (All audio) show](https://d3dthqtvwic6y7.cloudfront.net/podcast-covers/000/026/794/small/the-economist-all-audio.jpg)
Summary: Their light takes billions of years to reach us, and they are bigger than whole solar systems. But science hasn’t just understood quasars, it has found a use for them. In this podcast, our science columnist Oliver Morton explains how they help us navigate our own planet