It takes 38 minutes to fall through Earth!

It would only take a person 38 minutes to fall all the way through the centre of the Earth, instead of the commonly accepted 42 minutes.
The traditional calculation to measure a fall through Earth assumes that our planet has a constant density throughout its many layers.
The new approach assumes that when the different densities of Earth's layers are taken into account, the trip is four minutes shorter than predicted.
To get a realistic mass distribution for Earth, Alexander Klotz, a graduate student in physics at McGill University in Canada, relied on the Preliminary Reference Earth Model, which is based on seismic data.

It traces Earth's density from about less than 1,000 kilogrammes per cubic meter at the surface to roughly 13,000 kilogrammes per cubic meter at the centre of the core 6,371 kilometres below, including a dramatic jump at the edge of the outer core, 3,500 kilometres from the centre.
Solving the problem numerically, Klotz found that an object should fall through Earth in 38 minutes and 11 seconds, instead of the 42 minutes and 12 seconds predicted assuming a uniform planet, 'Science magazine' reported.

Klotz found that he got almost exactly the same answer - 38 minutes flat - if he simply assumed that the force of gravity remained constant and equal to the value at the surface as an object plummeted towards the centre.

Such a constant force would require a different density distribution, one that increases steadily as the distance to Earth's centre falls - so that when the distance to the centre is halved, the density doubles - and peaks to infinity at the centre.
The research was published in the American Journal of Physics.