Your guess
A hole through the centre of the Earth, and you jump in. How long to the other side?
The real Earth is different
38minutesto fall through the centre of the real Earth
The Earth isn't equally dense everywhere. Calculated with its actual structure, worked out from earthquake data, the fall through the centre takes 38 instead of 42 minutes. Straight tunnels then range from 42 minutes for short trips to 38 for long ones.
An old idea
As early as the 17th century, Robert Hooke wrote to Isaac Newton about a body accelerating inside a planet. Lewis Carroll took up the idea in 1893 in "Sylvie and Bruno Concluded". For comparison: the deepest borehole in the world, Kola, goes down 12,262 metres.
