Why the Shape of Lightning is Zig-Zag and not a Straight Line?

... Ashish/scienceabc:

very time it rains heavily, people get to see a lot of lightning in the clouds. Sometimes, you get to see bolts of lightning even when it is not raining. The sharp branches of lightning looks like many sharp weapons stabbing the sky, all at the same time. For some the visual is majestic, and for some, it is utterly dreadful. No wonder why people sometimes shudder when they hear a thunder.

The shape of lightning is what intrigues many. Why is lightning zig-zag? Can’t it be a straight line, or a triangle or a circle for that matter? Why the ‘branched shape’ ‘is what we get to see every time lightning strikes? 

What is lightning?

Lightning is basically an electric current (yeah, like the one we have in our houses, only lightning is thousands of time more powerful and dangerous). The temperature of lightning is around 27,000 Degree Celsius, that is 6 times hotter than the sun! It is a kind of electric current which, most of the times, forms in the cloud but sometimes forms between the cloud and the ground, resulting in a spark of lightning that we see.

The upper part of cloud is at a very low temperature i.e below the freezing point of water. So water vapour in the clouds turn to ice. As the cloud gets bigger, these small bits of ice bump into each other continuously, resulting in the build-up of electric charge. The lighter and positively-charged particles remain at the top of the cloud and the heavy negatively-charged particles (electrons) remain at the bottom of the cloud. A bolt of lightning is created when the buildup in electrical charge is enough to create a channel between the two opposite charged particles. And the moment these two charges connect, voila! There is lightning!

Why such a weird shape?

Why can’t lightning have a plain, straight shape?

Pretty much like we do, lightning likes to take the path of least resistance i.e the path where there would be minimum opposition to its flow.

For understanding this, say you have a heap/mound of dirt or sand. Now when you pour water on it, right at the peak of the mound, how does the water flow downward? Does it flow in a straight line? Is there a specific pattern to which it adheres?

No. There is no specific pattern or path that water would take to come down. Similar is the case of lightning.

Air is made up of a number of things like certain gases, dust particles, pollutants and so on. But this mixture is not homogeneous i.e it is not uniform. Air is uneven and irregular. This is why when lightning is formed (due toit the potential difference of the charges) it makes sure that its path is clear or has least resistance.

It doesn’t have to be a straight line (as straight line means ‘the least distance’ and not ‘the least resistance’) for lightning. In fact, you would never see a straight bolt of lightning, at least in reality.

Does lightning travel upward or downward?

This is another question about lightning that seems to confound many. To be precise, it is actually both.

The positively charged particles from the ground start to move upwards through the air to meet the negatively-charged particles that are racing downwards from the bottom of the sky. So some could say that many times the whole process of lightning starts from the ground up. But the whole process was first initiated due to the presence of electric charge in the clouds.

Lightning is a process of flow of charged particles both ways, downwards and upwards. That is the reason it appears to be flickering.

Also remember, as lightning looks for the path of least resistance, anything on the ground like tall buildings, towers, trees or even humans may provide the path of least resistance. So it would be a good idea to stay indoors when there are lightning strikes occurring constantly.

You wouldn’t want to provide lightning a path through yourself, would you?