Crikey, we're get a little off beam here, discussing science.

Yes, the Earth's gravity depends on the MASS of the Earth. The MASS is at it's optimum at the point furthest from the centre of the Earth )the thickest point). Thus a suspended "plumb line" will settle at a point directly pointing to the centre of the Earth/MASS.

Notes:

1) Two high plumbed pillars set a good distance apart will never be vertically parallel.

2) Three high plumbed in line pillars set good distances apart will never be vertically parallel.

3) If you put a datum/level mark on the face of each of those pillars using a water-level the marks will not be precisely optically in line. The centre one will appear to be higher due to the gravitational effect on the water in the tube.

4) This effect can be checked and measured using an optical instrument like a laser beam or theodolite., etc.

Next week: How to build an ark capable of holding at least two of everything living on Earth for a month or so at sea. How to feed the lot of 'em and get rid of their waste products. How to stop the buggers from killing and eating each other. And how to repopulate the world with sane people and healthy animals despite the inherent dangers of crossbreeding.