Asked by David Doran
If the Earth were a perfect sphere of uniform density, and you could be placed there at rest with no overall movement, then theoretically you would be weightless. This is because you would be being pulled equally in all directions by the mass of the (uniform) planet, giving an overall gravitational force of zero. And with no overall gravity force, there is no weight.
However our planet is not a perfect sphere. Instead it is squashed at the poles and bulges at the centre. It is also not of uniform density. As a result, you would eventually feel an overall pull due to a denser region of gravity, and the thicker ‘bulge’ of the Earth giving you a small effective weight.
This does of course assume that you could overcome the extreme temperatures involved with traveling to the Earth’s core!
Answered by Sophie Allan at the National Space Centre
Image courtesy of the National Australian University (ANU)