If we were able to dig through the Earth, at what point would you stop digging down and start digging up?

Asked by: Clare Johnson, West Yorkshire

To dig from London to Sydney, you would actually need to angle about 15° off the vertical, in a roughly easterly direction, so technically you are never digging straight down. Your tunnel would reach its closest point to Earth’s centre after about 6,150km and would slope upwards after that. Assuming, of course, that we ignore all the physical impossibilities inherent in such a project.

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