Let’s assume you have the survival skills necessary to see you through a large scale disaster. You and your family had enough food and water. You were in a safe location and had sufficient security to see you through the aftermath and death of the majority of the people in your country.
For a while afterwards you can salvage supplies, materials and tools from the ruins of what’s left. You can start to establish a self sufficient environment for the future. But what happens next?
When the last battery wears out do you know how to make more? When the last flashlight bulb breaks can you make another one? When your last solar panel breaks can you make a replacement? When the last computer dies can you make a new one? When the last pair of shoes wears out are you going to go barefoot?
What will your children do when there are no more parts to salvage? What will your grandchildren do?
Much of our existing technological infrastructure has been built upon increasingly sophisticated technology which some time ago passed the point of being “bootstrappable” i.e. able to be recreated from scratch. Much of our technology requires other precursor and support technology which is itself not capable of being “bootstrapped” from scratch.
Computer production requires optical and electronic devices far beyond the capability of an individual to produce. The crystals of silicon used to produce most computer chips require sophisticated ovens and production facilities that few people could build. The tools used to manufacture wafers from silicon crystals depends on generations of development that could not be built in even a sophisticated machine shop. Even something as seemingly simple as a pocket calculator was beyond the capability of the technology that put a man on the moon in the 1960s.
The U.S. built the worlds first nuclear weapon in the 1940s. They built submarines. Aircraft that could fly half way around the world. Primitive ballistic missiles. Jet engines But all of the technology of that time could not build a simple pocket calculator as we know them today or an LED flashlight. They not only did not have the technology but would have had to build several generations of new industries in order even to create the tools and technology to do so.
Most of us today know how to OPERATE modern technology but few if any of us have the knowledge to manufacture that technology.