Somewhere right in the middle, you’d be weightless. Might feel kind of funky. But certainly privileged too: after all, how many of us get to experience weightlessness? Only, you’d likely also be dead.
That last might be one reason nobody has tried the experiment. Then again, there is actually a more compelling reason than death: this is a pretty much impossible thing to carry out. Except as a thought experiment.
And what am I referring to? Drilling a hole through the Earth and crawling all the way through to the other side. Somewhere in the middle, you will be weightless for a short while. That alone would be enough to attract me to such an effort, were someone ever to attempt it. But how to cope with death?
Before we try answering that, let’s get something about all this straight. Assuming you could drill all the way through the Earth, it’s more than likely that when you get to the other end, you’ll have an ocean draining into the hole. Put another way, the great majority of points on land on our planet have antipodes—the points diametrically across the planet—that are not on land.
For example, if you started drilling in Mumbai, you would emerge smack in the South Pacific, something like 3,000 km west of Lima, Peru. Similarly if you began in New Delhi, or Kolkata ... in fact, from anywhere in India. Similarly Moscow, London or Cairo. Start from San Francisco and you’ll end up with the Indian Ocean flooding you. Tokyo, the South Atlantic. Melbourne, the North Atlantic. Dig in Lima, on the other hand, and you’ll emerge somewhere in Cambodia. And wait, it’s not quite anywhere in India. There is a point about 40km northwest of Jaisalmer from where a hole through the centre of the Earth will take you to Easter Island.
(Aside: how do we know all this? Take the latitude and longitude of where you want to start—Mumbai is about 19°N, 73°E. The latitude of its antipode is thus 19°S. The longitude there is (180-73)°W, or 107°W. Check that: 19°S, 107°W is in the South Pacific. Water, water everywhere.)
The point is, you will need to very carefully select a spot to start digging, to ensure you finish on land and don’t drown instead. So yes, you can start northwest of Jaisalmer and aim to arrive, not having drowned, at Easter Island.
Though as I’ve already hinted, drowning at the other end will likely be the least of your problems. Start with simply digging down. The deepest gold mine in the world is in South Africa, and it’s about 3,900m below the surface. In China, scientists started digging a hole last July. They want it to extend about 10,000m into the Earth, to study a layer of rocks known to date back 145 million years. Still, it won’t even be the deepest hole humankind has ever dug. That honour goes to the Kola Superdeep Borehole in Russia. Digging there started in 1970 and continued till 1992, when it had penetrated to a depth of over 12,000m. It was discontinued then, and the hole was sealed in 2005.
Deep as those holes are, the truth is that we humans haven’t done too well at digging through our planet—in the sense that we haven’t got very far at all. The Earth’s radius is 6,371km. So even that Kola hole in Russia completed less than 0.2% of the journey to the centre of our world. In fact, the planet’s “crust", its outermost layer that we are all standing on, is about 35km thick on average. So it’s no exaggeration to say that the Kola hole barely even scratched the surface of the Earth.
Part of the reason is that there are physical limitations to such drilling efforts. After all, you can’t simply lower a drill bit into a deep hole and rotate it. Why? Because, think of rotating a drill bit that’s 12km long. How is that going to happen? Then again, nobody operates bits that long. There are more realistic ways to dig that deep. But there are other constraints to deal with. Mainly, as you get ever deeper, there’s the ever-increasing pressure and heat.
For example, the heat in the gold mine I mentioned above, at 3,900m below ground level, is unbearable for miners. They could only work there because it was air-conditioned. At the bottom of the Kola hole, the temperature was 180°C, impossible for humans to tolerate. These temperatures will only rise as we get deeper into the Earth. Below the planet’s crust is the mantle, some 3.000km thick. Then a 2,250km thick outer core, followed by the inner core, a molten iron ball with a radius of about 1,250km. Now iron melts at a temperature of over 1,500°C. So we know the inner core is at least that hot. In fact, at about 5,000°C, it is much hotter. Even if the digging equipment somehow survived that furnace, humans would not. Crawling or falling through the hole you’ve made, you’d be roasted alive in a matter of minutes.
But what if you got yourself a body suit that’s resistant to this extreme heat? Well, then there’s pressure that will kill you. At the Earth’s surface, we have an atmosphere that’s about 10km thick. In the hole, you’d have thousands more kilometres of atmosphere pressing down on you. Every 10m deeper you proceed will add one more atmosphere of pressure. At the absolute centre of the planet, you’d be feeling over 1 quadrillion times as much pressure as at the surface. Subjected to that kind of pressure, the air itself would become a fluid of sorts, and so would you. Let’s just say, you’d be an integral part of that molten iron.
Then again, despite its extreme heat, the inner core is not liquid. That’s because the intense pressure solidifies the molten iron. So if you were actually able to crawl all the way there, I am unable to speculate on what kind of state you’d be in, in that ball of molten iron. Apart, that is, from dead. No speculation there.
But you’d also be weightless. Because right at its centre, the Earth’s mass will exert equal force on you in every direction. Probably a pleasant feeling. Too bad your roasted, compressed, molten and very dead self won’t feel a thing.
Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. His Twitter handle is @DeathEndsFun.
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