There are ~400bn systems in the galaxy, if you just wander randomly then you see an earth like every 200-250 systems on average so that makes a likely 1.5-2 *billion* systems with earth likes.
There are ~400bn systems in the galaxy, if you just wander randomly then you see an earth like every 200-250 systems on average so that makes a likely 1.5-2 *billion* systems with earth likes.