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Lighthouses occupy a special place in the history of modern Australia. They stand as monuments to the transformation of the nation from a colonial outpost to a prosperous society. For millions of people, they were the first sign of civilization after a long sea voyage to a new home. For others, they are grim reminders of the sea’s dangers. Modern technology has made many lighthouses unnecessary, but the buildings still evoke a special passion. They remind us of a time when ships ruled the world.

Q1) The above text is the segment of a paragraph. I was wondering what the second and third sentence mean.

Does the second sentence mean this? When you think about lighthouses built in Australia, they remind you of colonial outpost and prosperous society? I.e., Australia was once an outpost (of the Great Britain?) and now is a prosperous society?

Q2) What about the third sentence? I have no idea what "a long sea voyage to a new home" means. Does "a long sea voyage to a new home" mean that some kind of people went to Australia to spread civilization?
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They stand as monuments to the transformation of the nation from a colonial outpost to a prosperous society.
The basic idea is this. Australia used to be a colonial outpost (of Britain). By building lighthouses, Australia showed that it was becoming a prosperous society.

For millions of people, they were the first sign of civilization after a long sea voyage to a new home.
Millions of immigrants sailed a very long way from Britain to Australia. The first things they saw were lighthouses. When they saw them, they knew that they had reached a new civilization.

Clive
Comments  
Students: Are you brave enough to let our tutors analyse your pronunciation?
Wow. Now I know what they mean clearly.

It was hard for me to derive the meaning of the sentences when I taught my students. Do you think it is hard to know the meaning of those two ssentences without the background knowledge? (like Australia was an outpose of (Britain) and "millions of immigrants sailed a very long way from Britain to Australia?"
I mean, is the context not enough to get the meaning you answered?
Yes, difficult without a little background knowledge.