The War of the Worlds by H. G. Wells is one of the first science fiction books. Aliens from Mars invade suburban England riding scary tripod machines.
The scariest thing about this book is that it was written in 1898, 16 years before World War I, yet it contains realistic depictions of the use of poison gas.
I saw the Spielberg movie when it came out in 2005, and I was surprised by how closely the plot elements were drawn from the book. The red vegetation, the mad 'curate' in the cellar, and of course the final downfall of the Martians are all the same.
But what worked in 1898 for H. G. Wells didn't work in 2005 for Spielberg. The ending frustrated me. How could alien beings with the technology to cross vacuum be defeated by something as common as microorganisms?
Enter the insightful husband. When War of the Worlds was first published, he points out, germ theory was only a few years old. It was still cutting-edge science, so it seemed reasonable to people that other technologically advanced people might not know about it. Now germ theory is 100 years old so it seems obvious. The newness of computer viruses made the defeat of the aliens in Indepdence Day seem credible ten years ago. Would it be believable today?
What technology of today would be a good choice for bringing down invading aliens? Nanotech? And in twenty years it will seem run-of-the-mill.