Remember those cartoons where a character starts digging into the ground and emerges from the opposite side of the world? Have you ever wondered if this would be possible in real life? And if it were possible, what lengths would we have to go through in order to do it? Let’s take a look at whether it’s truly possible to dig your way to the other end of the world.
You might have learned in your Geography class that the Earth is not actually a perfect sphere but an ‘oblate spheroid’. This means that its diameter is not the same at all places. In fact, it is the widest at the equator (the zero-degree latitude) and gets narrower towards the poles. For the sake of our thought experiment, let’s assume that we are trying to dig across two opposite points at the equator. The diameter of the Earth at the equator is about 12,756 km. That sure is a lot of digging!
To dig all the way to the opposite side, our first challenge would be to dig through the outermost layer of the Earth, which is called the lithosphere. This outermost layer is like the eggshell of an egg and is made up of two parts – the crust and the upper mantle. Our first challenge would be digging through the crust.
The crust is generally divided into two types – the older, thicker continental crust (20 – 60 km thick) that holds all landmasses and the relatively younger and thinner oceanic crust (5 to 10 km) that forms the floor of our oceans. To prevent ourselves from drowning in ocean water or accidentally creating a tsunami, let’s pick a relatively thin part of the continental crust to get started!
Since we’re trying to get to the other part of the globe, we can’t dig with a simple shovel. So let’s assume we have some sophisticated machinery like those used by oil drilling companies. At this point, it’s probably a good time to note that the deepest artificial point man has ever reached is around 1,226 metres. This record is held by The Kola Superdeep Borehole in Russia. In comparison, the borewells under our homes are barely 100 to 200 metres deep. This means that humans have never dug deeper than the crust – the very first top layer of the lithosphere. But we’re not going to let that discourage us, are we?
It should be noted that as we keep digging downwards, the temperature and pressure also steadily keep increasing. Geologists estimate that, for every mile (~1.6 km) you dig beneath the Earth’s surface, the temperature rises 10º C and the pressure increases simultaneously at a rate of about 7,300 pounds per square inch. Even if we bear the discomfort and miraculously make it through the Earth’s crust, the fact remains that we would still have a long way to go. In fact, if the crust of the Earth is compared to the thickness of the eggshell of an egg, it would be three to four times thinner than the eggshell! That’s how relatively thin the crust is.
Right below the crust is a layer called the mantle. This is where things get interesting! The mantle is composed of silica-rich rocky material with an average thickness of 2,886 kilometres. The mantle makes up 84% of the Earth by volume, which makes it the egg-white in our above-mentioned egg analogy! The tricky part is that while the mantle is technically solid, it behaves like a viscous fluid due to the fact that temperatures are so high that the rocky material is almost close to the melting point. The upper mantle, which is the top part of the mantle, is what is responsible for seismic and volcanic activity and most of our knowledge about it comes from studying such volcanic activity.
At this point, it must be pretty obvious that the temperature and pressure in the mantle are certainly not suitable to sustain human life or any other kind of life for that matter. The temperature and pressure are so intense that ordinary carbon molecules turn into precious diamonds here! This is perhaps a good point to give up on our digging adventure! But let’s assume for a moment that we are placed inside an indestructible drilling machine that can sustain these inhospitable conditions.
Beyond the mantle lies the central structure of the planet – the core. Located at about 2,900 km below sea level and spanning a radius of roughly 3,400 km, the core is a giant sphere made mostly of iron. While the inner core is solid, the outer core is in a hot molten form. Scientists believe that it is the movement of the metals in the outer core that creates the Earth’s magnetic field. So if we do manage to dig all the way to this point, our compass is going to start malfunctioning! But that should be the least of our worries considering there is no oxygen to breathe and that the temperature and pressure are high enough to turn us into a very hot mulch!
If we miraculously survive to dig through the core of the Earth, remember that we have to go through the mantle and the crust on the other end of the planet in order to reach the surface again. An additional problem is that while we are resurfacing from the other side, we will most probably end up under one of the oceans. This is simply because the majority of the Earth’s uppermost layer is covered by oceans (roughly 71%) and the probability of us finding land is really slim unless we have some magic method of finding directions while digging through the formidable core of the Earth. Our compass is fried, remember!
So all things considered, would it be possible for humans to dig through to the other side of the planet as seen in cartoons? Everything we have learned so far suggests that it is practically impossible. A simpler way would be to dig a few metres into the crust and then tunnel all the way through to the other side. But where’s the fun in that?!
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