How did we find out that the earth is part of the solar system?

i need to do a astronomy booklet and cant find this answer anywhere. PLEASE help!!! Also- Why do we think that the Earth is the only planet in the solar system that organisms can survive on? and to:- Find out three theories about how the universe is organised that are different from the one we know to be... show more i need to do a astronomy booklet and cant find this answer anywhere.
PLEASE help!!!
Also-
Why do we think that the Earth is the only planet in the solar system that organisms can survive on?

and to:-
Find out three theories about how the universe is organised that are
different from the one we know to be true today

Please help!
Thanks, please can i juust have proper answers and no mucked up stuff!
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