Some skeptics of the geology text books we had in school theorize that the Earth maybe hollow. They say; the Earth is probably hollow and since it has had 5.5 billion years to cool down, it probably is not hot any longer in the center and that the effect of gravity has loosened up the center and pulled it outward along with the centripetal force of the Earths rotation. If it is hollow, what is inside? Is it a vacuum, void of air or does it have its own atmosphere of gas? What type of gas. Interesting if you are referring to 22% oxygen we have in our atmosphere, if this is your question; yes it is void of what we consider air. You most likely could not breath it or could you? But just because humans cannot breath it does not mean another form of life could.

If you used the Earths rotation and the energy harvested from a properly places spiraled tunnel exiting at the equator, you could launch stuff into space without rocket fuel. You would use and elliptical entry into the Earth avoiding problems of plate tectonics near the surfaces near continental shelves and with a bang the spacecraft or whatever it was you were shooting would be launched through the atmosphere. You could use this for trips to the moon for mining, visiting, or even shooting nuclear waste into the sun, so it would not be a containment, which might harm life here. Speaking of inertia, you might use the nuclear fuel inside your vacuum tunnel so you can get an exponential boost of your shot, by starting it at a higher speed. Kind of like the principle of time and money in your kids college fund. The more you start with the faster it can double every 6.6-7.5 years. You could also use this tunnel to shoot pieces of ice particles into the atmosphere causing condensation and rain clouds, when ever and wherever you wanted them. Where do you get the ice? At the poles, as soon as they hit the atmosphere they would turn to hot water due to the friction.

Traveling through the center of the earth is also good because we can calculate the inertia needed and end the tunnel with whatever speed we wanted to exit at, let use say 5 mph. Its all simple math. The other great things about this are the possibilities for mining of raw materials. Its all here already. The periodic table of elements is in abundance here under our feet; need more gold, silver, titanium; no problem.

There are benefits to traveling to the center of the Earth for curing the effects of gravity here on our bodies. If you have a back ache or a problem you could fix it, via robotic surgery in the center of the Earth, while all your body was pulling itself apart, fixing a disk in your back. I bet as soon as someone tried to drill a tunnel for the good of humanity into the Earth that the sierra club would have a tizzy. Dont hurt the endangered microbes? Think about a half of a gravity pull in all directions, how could the center of the Earth stay together with that type of pull over 5.5 billion years? If your answer is quantum physics, you are correct. But one would have a hard time negating the theorists of the hollow Earth completely as there must be parts which are hollow. So then what is in the center of the hollow earth? Your new answer would be that there is sand particles, which had stayed together and are clinging to all sides of the walls of the center. The true mass of the Earth is in the donut itself pulling itself together sideways where the ends, equator sides are pushing into each other and forcing friction at the surface outwards, yet the spinning is keeping centripetal force working in our favor. Some say the center of the Earth is filled with oil and we therefore will never run out of it. What do you think of the hollow Earth theorists? Interesting indeed; think about it.