1. List some of the pros and cons in the argument that alien spacecraft have visited Earth. 2. Our planet were the moon of a much larger, Jupiter-like planet that orbits the Sun at 1 AU? What might...

1. List some of the pros and cons in the argument that alien spacecraft have visited Earth.

2. Our planet were the moon of a much larger, Jupiter-like planet that orbits the Sun at 1 AU? What might Earth and life inhabiting it be like?

3. Our Moon were Earth-sized and also had life on it?