Solar activity goes through cycles. The main one is about 11 years long and its maximum is marked by powerful eruptions of electromagnetic radiation known as solar flares, as well as releases of plasma known as coronal mass ejections. The most powerful known flare happened in 1859 and led to telegraph stations catching fire across the US, and Northern and Southern Lights becoming visible in the tropics. Host Dr Alfredo Carpineti spoke with Dr Ryan French, astronomer at the National Solar Observatory and author of The Sun: Beginner's Guide to Our Local Star, to find out about solar flares and what would happen if a massive one took place today.