91热爆

Supporting Content

• Jumping into a black hole — Who Is Afraid of a Big Black Hole?

  Duration: 4:46

• The problem of measuring coastlines — How Long is a Piece of String?

  Duration: 6:23

• Recording data on global population at the UN — How Many People Can Live on Planet Earth?

  Duration: 4:44

• How long is a piece of string? — How Long is a Piece of String?

  Duration: 6:51
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