what is mean "The world's forge"?

Without context, I can only assume it means a place where products are hammered into shape to become useful objects. Again, depending on context, it might be a heavily industrialized city or nation.

this is context.
Detroit. This is where it all began. The world's forge. The place where it all started, and it will all end. One year, when I came to life, I stepped out of the darkness and I opened my eyes. First there was fear-the light, the noise, the cold-and the fear again. I could feel my hands shaking, my heart pounding in my chest, life running into my veins. I wanted to live-I fought for that.

Well, it was an early center of automobile manufacturing. It was more casting and machining than forging, but they are speaking metaphorically.

can you explain for me in other way?
because I can't understand world's forge.

I'll try.

A forge is a thing in which metal like iron or steel is heated prior to being beaten into shape by a hammer on an anvil. Take 'forge' to be a symbol of all manufacturing. The world has lots of places in which manufacturing occurs, but your writer is trying to make it sound like Detroit is at least representative of all of them.

Difficult. Let me take a stab at it. Going back to it's Latin origin we get 'Mundi fabrica' Translate 'fabrica' to fabrication.
"The planets fabrication centers are also known as the 'worlds forge'??? That sucks.

This is a heck of a lot harder than it looks. Anyone else want to try?

Think of forge as being made. For a period of time Detroit was where most of the Word's cars were made.

Or perhaps the center of the world's heavy manufacturing.

The writer is trying to be poetic, not literal. He is trying to paint a picture in your mind of factories with molten metal pouring into molds, guys in hard hats and grimy overalls carrying metal lunch pails to work. A gritty, somewhat dirty, hard working place.

I know, I get it. The OP seems to have problems grasping that. I was just trying to simplify things, I don't know if I've succeeded.

the context

http://able2know.org/topic/332843-1#post-6225180

The car industry was a huge step in America's development into an economic powerhouse. This was the first country where the average worker could own a car, and it symbolizes the industrial age and a huge increase in standard of living for almost everyone. Detroit was the home of that-in fact, it wasn't until the late 1960s that the rest of the world combined made as many cars as America did, mostly in and around Detroit. The factories that turned out the cars were enormous, city blocks in length and a hundred feet high inside, and had huge hammers and all sorts of mechanized metalworking machines forming the cars. It was like a different world in those metal car factories. Now many of those big huge factories that gave employment to so many people in the Midwest are largely gone, and Detroit has become a symbol of a deteriorating city with much poverty and a high rate of crime and violence.

PS: In the same sense, today you sometimes hear China referred to as "The World's Factory" because of all the factories and industry there.

100 years ago Britain, with its busy manufacturing industries which transformed imported raw materials into finished products for export was sometimes called 'the world's workshop'.

thanks.

Grain growing regions are often called 'breadbaskets' e.g. the Great Plains of North America, Ukraine, are "America's breadbasket" and "Europe's breadbasket" respectively. The county of Kent was called the "garden of England" because it has a large number of orchards and hop farms. The city of Reedley in California considers itself the "world's fruit basket" because of the large amount of stone fruit grown there. Such expressions focus on the global or regional significance of a region or country in the supply of a commodity or service.

thanks you so much.

You're welcome.

thank you so much..

thanks..

thank.