Did China "discover" The Americes first?

[source: http://history.howstuffworks.com/european-history/chinese-beat-columbus.htm] [pages 1-4]
I belive the theory is true because of all the evidence that has been discovered. I personally think that even though alot of historians oppose the 1421 theory is because they dont want to change the history that has been around for alot of years. Not only that but if historians give in to that theory then people are going to think that ALL the prior knowledge or well known history is wrong and historians do not want to go through the trouble rewriting and having to prove all the information in text books is true. Knowing that the chinese have always been one step ahead of everyone and still to this day they are. It is not vey hard to believe that they made that voyage but the maps discoverd are the best clue that maybe they did disciver the Americas first.