> Isn't the whole world a fixed pie?

Nope. We use energy to transform valueless things into ever more valuable things.

Someday our current cheap energy will run out, and we'll just have to divide up what we have left. At least, that's what I hear. People have been predicting this for a while, and it hasn't happened yet (at least where I live in the US), but that doesn't mean it won't.

The Earth is just a dot in the sphere around the Sun through which all the Sun's energy passes.

And eventually the sun will become a red giant, devouring the earth.

we have about 5 billion years to figure out a solution to that. I'm not too worried.