I dont quite understand this, was hoping someone could explain in simpler terms.

IĀ“ve read the wikipedia article, but I think I might have missed something.

HereĀ“s what I dont get.

The expected expansion is based on observation from Earth. But how can we be sure there isnt much more beyond the borders we can observe?

By definition we can only observe things as far away as light have had time to travel to us. But that is not to say there isnt things even further away is it?

And lastly, weĀ“ve only been able to observe and document like 200(if even?) years of modern astronomy, but letĀ“s over-optimisticaly say we have 2008 years of knowledge..

That in relation to the Universal timescale must be neglectable small.

It would be like guessing the size of the Earth by looking at a square centimeter on the ground and measuring its curve..

Well I for one canĀ“t get it together, isnt it naive to asume we know the age or size of the Universe with this (relativly) small amount of data?