Just how far is an astronomical unit (AU)? Such an enormous distance is not easy to comprehend. I could say, well, it’s the average distance from the Earth to the Sun. But nobody can actually travel from the Earth to the Sun to get a feel for that distance (and even a future space explorer would never travel it in a straight line). But maybe we can put this distance in terms of human experiences by asking: has anybody traveled an AU in their lifetime?

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