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I know the Sahara used to be green and now it’s not due to geography and planet axis, but is the Sahara a rainforest that sometimes in history is a desert or vice versa?

349 upvotes

197 upvotes

Title	Upvotes	Mark as read	Favorited	Rating	Add to a list
I know the Sahara used to be green and now it’s not due to geography and planet axis, but is the Sahara a rainforest that sometimes in history is a desert or vice versa?	349
How do scientists determine chemicals in the atmosphere of planets that are over a hundred light years away?	197