Digging a Tunnel through the Earth

As a child, have you ever had one of those random thoughts about digging right across the earth centre to travel to the other side of the world? I did, and I’m pretty sure I’m not alone on this.

The idea sounds bizarre now when I think back at it. But imagine a tunnel already exists, all you need to do is jumping right into it. What happens afterwards? Let me warn you ahead. The journey is promised to get bumpy.

Firstly, you might already be dead a few kilometres down the hole. To explain this, the Coriolis Effect has to be brought up. Everything, including you, on the surface of our planet, is rotating at a speed of 1670 km per hour eastward. As you travel further away from the surface and towards the centre, spinning rate of the Earth around you will drop gradually. Picture the cross-section of Earth as a circular running track. The person on the inner lane can run at a slower speed than the one on the outer lane and still manage to complete a full circle within the same amount of time. Because of the unmatched speed between you and the inner parts of the Earth, you will soon hit the tunnel wall and never make it to the exit.

Planet Bogota © copyright Tijs Zwinkels and licensed for reuse under this CreativeCommonsLicense(https://creativecommons.org/licenses/by-sa/2.0/)

This problem is not entirely unsolvable. Digging from pole to pole would render the Coriolis Effect ineffective. Imagine jumping from the north pole, you would experience a free fall as dropping from any high spot, and soon be travelling at a speed of 8 kilometres per second under the effect of gravity. Only 13 minutes would have passed when you are halfway to the centre of the Earth. The falling speed would increase from this point as you experience greater gravitational pull at the Earth’s outer core.

The closer you are to the centre, the greater the mass of the Earth above you and the stronger the upward attraction. It would start to cancel out the downward pull on you. Upon arriving at the centre, gravitational forces from all directions would act on you where you would undergo a state of floating but still be speeding through at 10 kilometres per second.

Once you are past the centre, the rest of the journey is the same as the first half only that the process is reversed. The whole trip might seem a little complicated, but it would just take around 37 minutes for you to arrive on the other side of the Earth. If this became a reality, we wouldn’t need to sit through hours of flight travelling to a country on the opposite side of the Earth. How time-efficient does that sound? Pretty awesome, right? But life isn’t meant to be easy. The Earth’s core contains liquid and is incredibly hot. We wouldn’t be able to dig through the burning centre with a temperature comparable to that of the Sun’s surface.

However, it might not be a bad thing that this plan is impractical. As humans, we’ve already done enough damage to the surface of the Earth. It is better that we stop here and not to torture its ‘beating heart’ inside.

2 Responses to “Digging a Tunnel through the Earth”

  1. Kye Kudo says:

    This is a great post Liya!

    As a kid I was always wondering what would happen if we jumped through a whole to the other side of the planet.

    Elon Musk might have to consider building these “super tunnels” to other side of the earth.

  2. afujii says:

    Hello Liya, your blog is very interesting. The introduction and the way you explained about the effect of gravity kept me reading all the way down to the end. I’m also interested in how you calculated the time and speed. Overall, your writing finally solved my question I had from 5 years old. Thanks for sharing.