Note also that "practical" is extremely subjective. The tungsten filament won out over the carbon arc for home lighting with better light quality and better durability. But it's not what we use to light up the IMAX.
Eli Whitney didn't invent the first cotton gin, he invented the first cotton gin that would work with the American long-fiber cotton without jamming up. That was only needed because better agricultural production technology made it so that there was more cotton harvested than could have the seeds combed out of it by hand.
A lot of it comes down to cost vs benefit. Babbage's difference engine was within the reach of the craftsmen of the time. But the price tag was hideously expensive. And for what? Yes, a completely error-free set of navigation tables would have been useful. But the rate of error was already low enough that the additional benefit of eliminating those errors wouldn't have paid for itself. An aeolipile could become a workable steam-turbine with sufficient investment in nozzle design, but when 80+% of your population has to be full-time farmers to grow enough food for everyone, who has time to work on that?
It's not just what you have to have for precursor technology to build something, it's also what you have to give up when you spend your resources on it. For much of human history that second factor has been quite high.
Note also that "practical" is extremely subjective. The tungsten filament won out over the carbon arc for home lighting with better light quality and better durability. But it's not what we use to light up the IMAX.
Eli Whitney didn't invent the first cotton gin, he invented the first cotton gin that would work with the American long-fiber cotton without jamming up. That was only needed because better agricultural production technology made it so that there was more cotton harvested than could have the seeds combed out of it by hand.
A lot of it comes down to cost vs benefit. Babbage's difference engine was within the reach of the craftsmen of the time. But the price tag was hideously expensive. And for what? Yes, a completely error-free set of navigation tables would have been useful. But the rate of error was already low enough that the additional benefit of eliminating those errors wouldn't have paid for itself. An aeolipile could become a workable steam-turbine with sufficient investment in nozzle design, but when 80+% of your population has to be full-time farmers to grow enough food for everyone, who has time to work on that?
It's not just what you have to have for precursor technology to build something, it's also what you have to give up when you spend your resources on it. For much of human history that second factor has been quite high.