"The $600 million Kepler observatory launched in March 2009 to hunt for Earth-size alien planets in the habitable zone"
I don't get why we can't live on planets bigger than earth or size like Jupiter ;-;
Well
Jupiter's gravity would crush you.
But for planets that are slightly larger/smaller than Earth, even if the gravity difference is minuscule, it would make a huge impact on our bodies in the long run.
Most children would have to be conceived in test-tubes if you expect them to live. Our bodies were made to live on Earth, and only Earth.