How to Calculate the Distance from Lightning

Lightning is an atmospheric electrical discharge accompanied by thunder, usually associated with and produced by cumulunimbus clouds, but also occurring during volcanic eruptions or in dust storms.. From this discharge of atmospheric electricity, a leader of a bolt of lightning can travel at speeds of 220,000 km/h (140,000 mph), and can reach temperatures of about 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites, which are normally hollow and can extend as much as several meters into the ground.

There are some 16 million lightning storms in the world every year. Lightning causes ionisation in the air through which it travels, leading to the formation of nitric oxide and ultimately, nitric acid, of benefit to plant life below. Lightning can also occur within the ash clouds from volcanic eruptions or can be caused by violent fforest fires which generate sufficient dust to create a static charge.

You know how it is - a thunderstorm is approaching, and suddenly you hear an absolutely deafening clap of thunder. Whoa, that sounded close! At times it can even be frightening! But how close is the lightning, really? It is difficult to determine the distance of a lightning bolt just by looking at it, and the volume of the thunder isn’t a good way to tell either. Read on for a simple, potentially life-saving method you can use to approximate how far away lightning is. Although these steps may not benefit you in the foreseeable future, it's a basic piece of knowledge that everyone should know.

Steps in calculating the lightning :
1. watch the sky for the flash lightning.
2. Count the number of seconds until you hear thunder. If you have a watch with a second hand or a digital watch that has seconds, begin timing as soon as you see the lightning and stop as soon as you hear the thunder start. If you don’t have a watch, do your best to count the seconds accurately. Say "One one thousand, two one thousand etc." in your mind for each second.
3.Every five seconds equals one mile. So if the delay between the lightning and the thunder is fifteen seconds, then the lightning is three miles away. The delay between when you see lightning and when you hear thunder occurs because sound travels much, much more slowly than light. Sound travels through air at about 1100-1200 feet (330-350 meters) per second (depending on altitude, relative humidity, pressure, etc.), which is a little more than one mile per five seconds (one kilometer per three seconds). In comparison, the speed of light is 983,571,058 feet (299,792,458 meters) per second.
4.Alternative. Since light is so fast you can simply multiply the seconds you counted by 340 to estimate the distance in meters (340 is approximately the speed of sound in m/s, and light is of the order of magnitude of 10^8 m/s so it will not affect your estimate by a meaningful amount) For example: 3 seconds times 340 gives you 1020m and that is even a bit more true than if you would divide 3 seconds by 3 to get 1km (from the previous method).

source:
http://en.wikipedia.org/wiki/Lightning
http://www.wikihow.com/Calculate-the-Distance-from-Lightning
http://wiki.answers.com/Q/What_is_the_speed_of_light_in_meters_per_second

guided by Prof. Crisencio Paner