1> All time greatest achievement~ Computer/Internet. Very useful for information.

2> 20th Century's greatest achievement~ Personally, I think the phone. Many, many people have phones today and it is indeed very good to have.

3> So far the greatest achievement of 21st Century~ Advanced technology.

4> All time worst achievement~ The creation of nuclear weapons.

5> 20th Century's worst achievement~ War.

6> So far the worst achievement of 21st Century~ Technology that isn't need; the iPhone, more advanced iPods, more touch screen phones, and things such as that.