We have always been fascinated by the thought of digging a tunnel across the earth. What will actually happen? Is it even possible to dig that far? What will be the consequences of digging such a huge tunnel?
Well, when a tunnel is dug across the earth, you will reach the other side of the tunnel way faster than air travel time. Is it even possible? In a nutshell, we do not have the engineering capabilities to do so. Many researchers have tried to dig a tunnel and check how much distance they can reach. Let us find out whether it is even possible or not.
The diameter of the earth is what we have to cover when we dig a tunnel to reach the other side of the world. It is around 12,742 km in length. The highest achieved depth of a hole dug by the Russians in Kola Well is 7 km (23,000 feet). The project started in 1970 and the depth was achieved within five years. It was then scrapped in 1989 when the drilling stuck into the hard rocky bed nearly 12 km deep underneath the earth’s surface.
The engineering challenges, in this context, will be massive. Even if the two opposite countries start digging to reach the midway, it will not be possible as both the attempts will have to cover more than 6000 km. The practical outcomes will not allow us to dig that far.
We have always fantasised that drilling a hole or a tunnel that far can lead us to the other side of the world. It means if we cover the distance diametrically, we will reach the Southern Hemisphere from the Northern Hemisphere.
What will happen if a tunnel crosses the centre of the earth? If we jump into that tunnel, we will accelerate at the rate of 9.8 m/s2 and reach the centre due to the gravitational force. It will take you 21 minutes to reach the centre approximately. The speed you will attain is 28,000 km/hr.
According to physics, when you reach the centre of the earth, you will be practically weightless. The closer you go to the earth's centre, the lighter you will become. Eventually, the gravitational force will be zero at the centre.
After reaching the centre by freely falling in the tunnel, your moment of inertia will carry you to the other end against the gravitational force. It will take another 21 minutes to reach the other end of the tunnel. When you arrive at your destination, your velocity will reduce to zero from 28,000 km/hr. The opposite point of that tunnel is called the antipode. To find it, we will have to pass through the cross section of the earth's layers.
There is no need to dig a tunnel to find the antipode, luckily. It is the point located diametrically opposite to the beginning of a tunnel. The scientific tools, formulae and derivations allow us to calculate the exact location of an antipode.
The earth is a big sphere and finding the location of the antipode will not be a problem. It is obvious that it will be the farthest point from you on the earth diametrically. If you start digging in North America, it is possible that you will end up somewhere in the Indian Ocean.
In another example, if you dig in China, you will reach the antipode located in Argentina in the Southern Hemisphere. If you start digging in New Zealand, you will be able to land in Spain. People digging in the Indonesian land will reach the Amazonian rainforest on the other half of the globe. It is not practically possible but the antipode locations can be easily found theoretically.
It is clear that an antipode will always be located on the other side of the other hemisphere on earth. For instance, if you consider a location in Memphis at 35° N latitude, its antipode will be somewhere in 35° S latitude in the Southern Hemisphere.
As per the calculations, the antipode will be 180° longitudes away from the prime location. The location of Memphis is 90° W. Hence, the location of the antipode will be at 90° S. To aggregate the fact, Memphis is located at 35° N 90° W. Hence, the antipode will be located at 35° S 90° E. According to the map, this location is somewhere in the Indian Ocean close to the western vicinity of Australia.
A Tunnel Dug Through the Earth
It is practically impossible to dig a tunnel and reach an antipode from one location on the earth. We will have to cross the hot lava core to go that far. Even with engineering advancements, we cannot do it in the present era.
It might be possible in the future that we master the technology of travelling through the earth via tunnels. You will be surprised to know that travelling through these tunnels will cost less energy and even less time. The whole work will be done by gravity. This force will create enough inertia to help you reach an antipode without any hassle.
It means you will not have to spend a little bit of force to reach the other side of the world. The gravitational force will pull you down to the centre of the earth and the accumulated inertia will pull you up. As mentioned earlier, the whole journey will take 42 minutes to cover the diameter of the earth.