Who hasn’t enjoyed Jules Verne great novel ‘ Journey to the center of the world’. As a child this book inspired my imagination. Imagine finding a passage way thru the crust of the earth, down down down one goes.  Passing thru prehistoric ages and finally reaching the very center of the earth where their magnetic compass no longer worked.

I was thinking about such a travel and the location of the center of the earth. Would the Magnetic poles no longer apply? Could lava force a return to the surface in a volcano, such as in the novel.  If it were possible to construct a spherical room at the center of the earth, I believe the most striking difference from the surface would be the absence of gravity.  Think about it, We are all drawn ‘down’ towards the center as the center of mass of all the matter under us. At the center,in our spherical room, one would be drawn equally in all directions by all the surrounding matter and hence weightless.  We all think we can achieve ‘weightlessness’ by going into orbit, but realistically in orbit one is still drawn to the center of the earth. In orbit, one is always falling. The reason we feel weightless is the fall is not sensed as the craft moved forward such that the earth surface fell away from the craft the same distance one fell.

The only place in the Universe where the effects of earth’s gravity is ZERO is the center of the Earth.. Everywhere else in the Universe the gravity can be detected.

John J Klosak

My brother in law brags how he gets 100k miles between changing his brake pads. Modern brake pads generally last about 50k miles. This is a remarkable feat but what does he do different? Brakes of course slow down the forward kinetic energy of the car. To reduce speed the kinetic energy of forward motion has to be converted to heat by the friction of the pads and rotors. The formula for kinetic energy is E=mass x velocity squared. Lets consider this. To slow down from 90 mph to 60 mph, assuming mass is 1(car) the kinetic energy change is the difference between 90 squared and 60 squared or 8100 – 3600 = 4500 energy units (EU) of heat. So if is one is driving at 90mph and pushes the brakes to slow down to 60 mph, the brakes wear down or heat up 4500 EU.

Now if you are driving at 30mph on a city street and apply the brakes to stop, Then you are dissipating 30 squared or 900 EU to reach 0 speed. Therefore slowing down from 90 mph to 60mph is 6 times as wearing on the brakes as one time stopping from 30 mph.

Lets consider a more modest highway speed change. Lets analyse slowing from 60 mph to 50 mph. By the same method this is the difference between 3600 EU and 2500 EU or 1100 EU. Of note, slowing from 60 mph to 50 mph is more wearing on the brakes than going from 30 mph to a stop (900 EU).

Going back to my brother in law, he must never touch the brakes when moving more than 30 mph.

John J Klosak