This application calculates the distance of a thunder storm by measuring the time between a lightning and the corresponding thunder. How to use: - When you see the lightning press the 'Lightning' button. - Wait until you hear the thunder and press the 'Thunder' button. - Tap the distance to toggle between metric and imperial units. - With the help of the history list you can see whether the storm comes closer and moves away. Background: The speed of light is much faster than the speed of sound. By measuring the time between the lightning and corresponding thunder one can easily approach the distance by multiplying the duration with the speed of sound. Apple Watch version: - distance calculation - history list - metric and imperial units - has a Check for a quick start