The best way to answer this is to explain the concept behind a lightning rod, the unpredictability of a lightning strike and what happens when the lightning hits the lightning rod. Lightning rods do not attract lightning until it is very close to the rod, and the best way to explain this is probably through an example.

A simple lightning rod is nothing more than a conductive piece of metal about 3 feet in length that sits atop the highest point on a house. Attached to this piece of metal is a thick copper wire that runs down the side of the house and attaches to a pipe which is driven several feet into the earth. That’s it.

A lightning bolt is far more complex and the kind of lightning we are worried about is called a cloud-to-ground strike which starts high in the clouds. On average a cloud-to-ground lightning bolt produces about 1,000,000 kW or about 50,000 amps, which is a lot! So much that it instantly vaporizes any moisture and creates a steam explosion that’s capable of exploding concrete, blowing out a chunk of wall, or melting just about anything. The interesting thing about lightning is it doesn’t know what it’s going to strike when it first starts to form. As more and more positive charge builds on the ground beneath the storm, more and more negative charge builds in the lower part of the cloud. As the charge continues to build, so does the attraction between the positively and negatively charged particles. The only thing stopping the electric current from flowing is air, which happens to be a very good insulator. This allows an immense amount of charge to build up.

As the charge builds, the air between the cloud and the ground starts to ionize (this part is invisible). This is done in small little paths, step-by-step, zig-zagging all about (this is why lightning looks the way it does and isn’t a straight line). Once it gets to within 100′ of the ground something weird happens. Objects on the ground begin throwing up “streamers”. These are like little fingers that shoot upwards about 50 feet. The first streamer to touch a step leader coming down from the cloud above will complete the circuit and a huge surge of electricity will flow (this is the part we see as lightning). Understanding that lightning doesn’t know at 50,000 feet what it’s going to strike is key. Just because you have a lightning rod, doesn’t mean it will attract lightning. It only improves your odds if a lightning bolt is going to strike within a 100 feet or so of your house.

Lightning strike streamer movie

Now, say the lightning bolt is making its way down to the ground and it’s heading right for your house. Your rooftop, satellite dish or a large tree (or maybe all three) throw up a streamer. If the streamer from the satellite dish or your roof makes contact with one of the ionization channels first, well, that’s bad. That means the lightning bolt is going to hit your house and cause a great amount of damage. But, if you did have a lightning rod at the highest point on your roof and it created a bigger streamer than your rooftop, satellite dish or tree, then the odds of it striking the rod are greater. Therefore, you would have decreased the odds of it striking something you didn’t want it to. If the lightning rod is struck, the electric current would pass through the metal rod, down through the copper wire and into the Earth. This is what you want! Your house (and your wallet) would not suffer any damage and life goes on as normal.

So, the lightning rod attached to your roof doesn’t really attract the lightning any more so than your roof or satellite dish do. If the lightning is close enough, your house was going to be hit anyway. But assuming you do have a lightning rod, the odds of lightning striking the rod instead of some other part of your house are increased, especially if the lightning rod is at the highest point of you house such that the ionization path reaches it first.

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