Possible to know all the history of the world?

 What a fantastic question! As someone who loves history, I love questions like this (and this is my 4000th answer on Quora). I personally did not learn much history in school and when you do, you tend to learn about names and dates, which isn't near as interesting and fun as reading about the people and events that made up history.

First, I would start by watching John Green's excellent Crash Course World History series on YouTube. He manages to make it fun and interesting and he does a good job condensing complex history down to the basics. He then followed it up with more in-depth histories by going into World History 2 and U.S. History as well. That's a good place to start.

Beyond that, you could pick up a book on world history, but the problem is that world history encompasses so much that the books and sites that cover them all are going to only pick the really big and significant events. You're likely going to get a very Eurocentric viewpoint as well as "Great man history", where they cover the kings and the wars and the nations. It's interesting on a certain level, but where it really gets fun is when you get down the little bits and pieces that make up history and see where they go. How the little individual people and events suddenly make a big difference and the economies and aspects ripple through time to change everything. So what I suggest is to pick a particular era, then find books and sites and videos that deal with that era and go from there. I love to pick up historical fiction novels, then grab source materials that the author used, read that, and then follow it up with other books on the time period, expanding my knowledge and finding out as much as I can. The novels give it a person touch and make me feel connected to the time through fictional characters and the history books give me a more scholarly viewpoint not colored by a narrative twist. That keeps it interesting for me.

Have fun and if you have any questions about a specific time period I can give you specific suggestions.

Here's something I wrote on Facebook a few years ago:

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You know the best part of history, especially ancient history? It's like a story where you know the ending and you can see all the little tiny pieces and how they come together. It's like following the most magnificent game of chess with thousands of pieces and random events unfolding to bring about a completely unpredictable conclusion.