More on using 'The'
http://www.5minuteenglish.com/january21.htm
Use the when you talk about general places in nature like the lake, the mountains, the ocean, the beach, etc. For example: Let's go to the beach. I love to camp in the mountains. Use the when you are talking about something that there is only one of and everyone knows about it. The sky, the earth, the stars (as a group).
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