At the risk of being whooshed, you do know that the “safety” is referring to the opener and not the can, right?
The fork was pretty late in coming compared to the knife and spoon
Re cans and openers
You know what’s funny? The fact that all the raw materials to invent anything we have today has always been around. Imagine if someone or a group of people thought of it, computers could have been around since the 1800’s and then all our Grandparents would know more than us about computers. :dubious:
The quintessential example must be the freaking steam engine. It’s amazingly simple and the technology to create it was there for centuries (shown by Greeks inventing it two thousand years ago, but failing to put it to any use) before it was finally invented. Imagine if the Vikings had figured it out. Imagine the industrial revolution five hundred years earlier. Where would we have been today?
But oh no! The world had to wait for some easily distracted Englishman to put the kettle on.
[sub]Just because this is this board and someone will point it out: I know James Watt didn’t invent the steam engine. It’s funnier this way. Cope.[/sub]
As you say, the concept of the steam engine is fairly simple. But I honestly don’t think one could have been successfully built much earlier than it was. There are a lot of prerequisites in metallurgy and precision of manufacturing before you can build a steam engine that doesn’t explode. The same applies to gunpowder. The Chinese had it a couple millenia ago, but making a usable cannon chassis or arquebus barrel is quite another thing.
But steam-driven toys were made around the turn of the millennium. Surely you could just scale them up? Or install a pressure relief valve like Watt’s speed governor, which surely could have been made at the time?
Suck. Bang. Blow. No, not your girlfriend – the jet engine. Its function and design are amazingly simple compared to the internal combustion or diesel engine. Air goes in through a compressor (suck), fuel mixes with the air, the mixture is ignited (bang), and force and exhaust are expelled from the rear (blow). The resulting combustion in turn powers the compressor, forcing more air in and self-igniting the combustion. Very few moving parts. Why didn’t we have these earlier than the 1940’s?
Adam
Pantyhose. Why did it take so long for someone to realize that you could attach a nylon panty to a pair of hose and do away with those horrible girdles and garter belts?
What do I look like, SkipMagic? 
What I find funny about this whole can opener thing is that I was indeed thinking only of the safety can opener. I had assumed that the lever and blade type was introduced with the cans themselves, not 50 years later.
As for the jet engine, various prototypes were made very early, I believe at least one experiment was even pre WWI. But, suitable alloys, able to withstand the heat, pressure, and corrosiveness (or whatever) weren’t available yet.
Watt is credited for the first positive-pressure steam engine. All the earlier models were essentially pumps that used condensing steam to create a vacuum.
Because nylon wasn’t widely available until after WW2? Before that you had silk “tights” like circus performers wore.
My contribution? The manned kite/ hang glider. If only people had been able to get over the preconception that you HAD to get the wings to flap, we’d have these in the Middle Ages.
The scroll wheel. It’s a very simple device, and it would have been useful on even the earliest GUI systems.
The horse collar. A simple idea, but the Romans and Greeks were using only half the available ‘horsepower,’ as the beasts we darn near choking themselves.
Street names and regularized addresses. People lives in cities a couple of dozen centuries before we go past the ‘turn left at the dead horse’ stage.
The Laser – the technology existed much earlier, but it required the theory of the resonant cavity and the idea that the stimulated emission would be emitted in phase with the excitation (according to this month’s Scientific American, Einstein thought it would be randomly phased) to produce a laser beam. It needed the maser to be built first.
1920’s style “Death Rays”.
People have been using looms to create cloth for millenia; even nomadic tribes hauled them around. But a simple set of knitting needles can do a lot too, and are a lot easier to carry.
Seat belts
Infant car seats
Horses as cavalry mounts
Gunpowder used as a weapon rather than just signal rockets or fireworks
Rifled barrels
Penicillin (no cite whatsoever, but a friend of mine told me that in her college biology class, they quoted the notes from an early 19th century medical student’s journal that, when conducting petri dish-type tests, they needed to avoid getting a particular bread mold in their cultures because it would kill everything else in the test…).
The ball element for typewriters, making the non-moving carriage possible. Why did it take IBM so long to invent the Selectric?
My guess is because the garters and such look hot.
Oddly crochet hooks are a fairly modern invention. Sailors used them in the early 1800s to make repairs and stuff. Then the ladies got involved.