how big a telescope would you need to image earth size planets around nearby stars, with optical wavelengths, with resolution good enough to look like the moon in our night sky (i.e. to resolve a little detail of continents/polar caps etc...)
such as 55-cancri ? (star discovered with solar system type planets recently)
55-cancri... 41 light years away
http://www.planetary.org/news/2007/1107_Solar_System_Emerges_around.html

so 3 or more hubbles, in wide orbit around earth all synchronized to look at the same time might work ?