Hi Harsha

I am using 4.0 as a shorthand for the next stage of human development

There was a time before Fire was used by man - let this serve for World 1.0

And then we had a long period where the primary energy us by humanity came from burning wood cut down from trees - let this era serve to define World 2.0

And then came the Industrial Revolution which started to need huge amounts of energy

Thus began our World 3.0

This energy was initially supplied by mining coal as you can see in the previous chart

Then Oil was introduced as a fuel, and later Gas began to play an increasing role

- which brings us up to today

But it was not just about the form or source of energy that we were using