# How to calculate the distance to a thunderstorm?

Perhaps you know of a method to find out how far away a thunderstorm is by counting the seconds after lightning strikes? In this short article, we'll talk about it. For those who don't know this trick, after reading this you will know how to quickly estimate the distance to a thunderstorm, as well as why counting seconds allows you to estimate the distance. Lightning and Thunder First of all, although we talk about "thunderstorm distance," the method described below is used to estimate the distance to a particular lightning strike, not necessarily to a thunderstorm in general. During a thunderstorm, the air currents produce a difference in electrical charges, which eventually accumulate between the ground and the cloud (and even parts of the same cloud). This potential difference can reach, by some estimates, a billion volts, and when the potential is too high, the air becomes ionized and the current briefly sets in between the ground and the cloud, forming a conductive transition, and a flash of lightning occurs. The lightning is short-lived. The current flowing heats the air to over 10,000 Kelvin (twice the surface temperature of the Sun). The air lights up strongly and becomes visible: this is lightning. Still under the influence of temperature, the air thus heated expands instantly and causes a shock wave, or, in other words, a very loud sound - thunder. Thus, lightning, which is light, and thunder, which is sound, are produced simultaneously. What is interesting for us is that light travels at 300,000,000 meters per second (1 billion km/h), while sound travels at "only" 340 meters per second (1,200 km/h). This means that light travels a million times faster than sound. In terms of human perception, lightning is immediately visible no matter how far away it is, while thunder takes a few seconds to become audible, depending on distance. This difference is used to determine the distance to where the lightning struck. Estimating the distance to a thunderstorm For every second the sound travels 340 meters. By counting the number of seconds between lightning and thunder, we calculate how many times 340 meters it is. To get the distance in meters, simply count the number of seconds and multiply it by 340: distance in meters = seconds × 340 For simplicity, you can also assume that 1 km ~ 3 × 340 meters. So every time you count 3 seconds, you should count 1 km. Conversely, if you divide the number of seconds by 3, you immediately get the approximate distance in kilometers. If you count from 1 to 3 seconds, it means that the storm is less than a kilometer away.
The same applies to the concept of a light year: "one light year" corresponds to a distance: the distance traveled by light, and therefore about one billion kilometers per hour. One light year corresponds to approximately 9,400 billion kilometers. Thus, if light takes one year to reach us, this means that the star is 9,400 billion kilometers away.