What if Earth was the only habitable planet in the entire galaxy?

Let's say that Earth is in fact the only habitable planet in the galaxy, and humans live on it. <br><br>Would we build space habitats?<br><br>Would we focus on exploring or exploiting other planets?<br><br>What about a galactic empire?<br><br>Would we just forget about other planets and focus on our own planet?<br><br>How about space war potential?<br><br>How would we conduct the search for alien life?<br><br>What would be the implications of us being the only habitable planet?<br><br>What would be the ethical implications of us being the only ones?<br><br>How would this effect our culture?<br><br>What would be the effects on religion and spirituality?<br><br>What about art?<br><br>Would the lack of life in the galaxy make our achievements seem hollow?