Recently around my neck of the woods we’ve been hammered with heavy thunderstorms packing damaging winds and dangerous lightning and thunder. Sunny summer days suddenly turn dark and ominous. Thick dark clouds blot out the sun and the sky opens up and lets loose with torrential rains, high winds and most impressively–lightning and thunder.
Are you noticing that I am saying “lightning and thunder” instead of the usual way of saying “thunder and lightning”? I think it sounds more natural to say thunder and lightning but really there is no thunder without lightning so it seems strange to put the cart before the horse.
So what is lightning and thunder? I think we all take lightning and thunder for granted. It’s part of nature but if you think about it you would agree that bolts of electricity shooting out of the clouds containing enough electricity to light a small city is truly amazing.
In order to understand lightning we need to step back and take a look at where lightning comes from. On hot humid summer afternoons the sun warms the land. Large columns of hot air rise into the sky. As the air raises it cools and the water vapor trapped in the air condenses which forms a cloud. These puffy round clouds are called cumulous clouds. They have flat bottoms, which indicate the condensation level. As the summer afternoon wares on the amount of cloud building increases. The small clouds become huge towering clouds with dark bottoms. Often these clouds are now called thunderheads, and they can reach up to 50,000 feet up into the atmosphere. Now these clouds are called cumulonimbus clouds. Within these clouds are very powerful winds surging up and down within the cloud causing the tops of the clouds to billow or mushroom out forming rounds puffy tops.
Within the clouds are water droplets and ice crystals bump into each other as they ride up and down on the strong internal winds. The constant collisions of the cloud particles build up electric charges within the cloud. The positive and the negative charges within the cloud are mutually repulsive which means they separate and segregate from one another. The negative charges migrate to the bottom of the cloud while the positive changes inhabit the middle and upper part. At the same time positive electrical charges are building on the ground below the cloud. Positive electrical charges gather on the tops of trees, buildings and any other prominent feature found below the cloud.
When enough positive electrical charges build up on the ground, a discharge of electricity flows from the cloud to the ground. During this process the electrical charges illuminate. The result is a flash of lightning. The flash is fast, only taking a millionth of a second but it can also take up to two seconds giving you plenty of time to see it. Lightning can also occur from cloud to cloud or from within the same cloud. The positive charges on the ground often jump up to meet the descending charges from the cloud giving the lightning the appearance of going from the ground up.
Lightning bolts have so much electric energy that they heat up to extreme temperatures. The average lightning bolt has temperatures between 30,000 and 50,000 degrees F. That is hotter than the surface of the sun. As the lightning bolt passes through the air, it heats up the surround air very quickly. The heated air expands so quickly that it creates a shock wave of expanding air. This fast moving air is what creates the thunder. So you can see there is no thunder without the lightning or the other way around.
We can see lightning from many miles away but sometimes we don’t hear it. This is often referred to as heat lightning. However as we just learned if there is lightning there will be thunder. When lightning strikes the light we see travels at the speed of light. In nature nothing travels faster than the speed of light. However sound doesn’t travel very fast at all, so it is very possible to see lightning and not hear the resulting thunder because it is so far away. You can hear thunder up to 20 miles away but not beyond that.
You can estimate the distance that lightning struck by slowly counting after you see the lightning flash. Since sound travels at about 5000 feet per second and there are 5280 feet in a mile, you can safely say that if you hear the thunder 5 seconds after you see the lightning, it was about one mile away.
Lightning is deadly so if you do see lightning take shelter immediately. There are over one hundred people struck by lightning every year in the United States. The National Weather Service calculates a one-in-three hundred chance that you will be struck by lightning during your lifetime. Until next time
Stan Tekiela is an author / naturalist and wildlife photographer who travels the US to study and photograph wildlife. He can be contacted via his web page at www.naturesmart.com