Statler Waldorf introduction.

[TheDarkestOfAngels]

That is because we have observed trees growing and people aging so we can apply what we have learned to trees and people that we have never seen before. But no one has ever observed how the universe began.

Or it's because we've cut a number of trees open and simply noticed that the younger ones have fewer rings than the older ones.
The funny thing is that the oldest tree in the world is older than what creationists believe the earth is.
See how that works? We didn't even need to observe a tree from sapling to death to know something like that. Utterly perposterous notion about observations you have.

Scientific estimates of age are based on the assumption that everything developed by natural means alone without any divine intervention. If this assuption is wrong then all of the estimates will be wrong.

http://atheistforums.org/thread-4052.html

Scientific estimates of the earth's age is based off of empirical evidence and nothing more, nothing less. If the evidence showed 6000 years, then scientists would say 6000 years. If it showed 4.54 billion years, then that's what they'd say it is. Unfortunately for creationists, it's the latter estimate.

Edit: Nice link you provided. It's too bad all of the 'evidence' against evolution and whatnot is wrong.