It takes a photon 170,000 years to travel from the core of the Sun to the surface, but only 8 minutes to travel the rest of the way to Earth.
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The Sun and Moon appear to be the same size because the moon is 400 times smaller than the Sun, but 400 times closer to Earth.
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Mars had an oxygen-rich atmosphere around 4 billion years ago
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The last time that the Sun was in its current position in space around the Milky Way, dinosaurs ruled the Earth.
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An organisation called Mars One is planning to establish a permanent colony of humans on Mars by 2023.
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