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In the 2012 film Total Recall, a straight tunnel exists between two antipodal places on Earth and work shuttle passes through the tunnel by dropping into it, reaching maximum velocity at the centre of the Earth, and rising out the other side. In the film this takes 10 minutes (I think), but how long would it take in "real life" (assuming it were possible to construct)?

I believe this is SHM and I have an answer written down from someone else of 42 minutes. I am not sure how he got it though. Thank you.

Kristof Arnaldo
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    Here is a reference. – lulu Aug 02 '19 at 00:39
  • @lulu Thanks. I didn't realise that people have actually thought about this already and there is even a Wikipedia page called Gravity Train with a derivation! – Kristof Arnaldo Aug 02 '19 at 00:56
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    It is a curious fact that the timing is independent of the two points connected, which need not be antipodal, assuming a friction free tunnel. – hardmath Aug 02 '19 at 01:43
  • @hardmath I wonder then if it is one of the reasons for why Douglas Adams chose 42 as the answer to life, the universe and everything... the fact you can get anywhere on a gravity train in 42 minutes! – Kristof Arnaldo Aug 02 '19 at 02:55

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