What would you do if you passed through the center of the Earth? The answer is a bit weird

Apophobia is the fear of falling, which most humans and animals have to some extent. Let's take a hypothetical extreme fear: what would happen if you fell to the center of the earth?

In Jules Verne's science fiction novel "Journey to the Center of the Earth", the protagonists go deep underground and discover a fantasy land full of strange creatures and an underground climate system. However, if you were to travel to the center of the earth in reality, although you would not really encounter dinosaurs, monsters, and an underground society, the trip would still be full of dangers.

So what, from a scientific perspective, would happen on a journey to the center of the Earth?

We know that beneath the rocky crust and hot mantle of the Earth, there are the outer core and the inner core. In reality, however, no one has been able to really explore deep beneath the mantle, so we cannot obtain first-hand environmental samples, but it is obvious that it is not suitable for human survival. The Earth's outer core is made of high-temperature liquid metal, and in some places the temperature is even higher than the surface of the sun; the inner core is also hot and dense, with a pressure of about 3.5 million atmospheres. Without professional equipment, people can generally only withstand about two to four atmospheres of pressure. In addition, being in the Earth's inner core also requires a slightly faster rotation rate than other parts of the Earth.

If you fell to the center of the Earth, this is what you would face. But humans have not actually drilled that deep yet, and the deepest one so far is the Kola Superdeep Borehole in Russia. It is more than 40,000 feet (12,226 meters) underground, but it is only 9 inches wide, so you could get stuck and sprain your ankle badly, preventing you from freefalling to the bottom of the Kola Borehole.

And even if you could get to the bottom of it, it would still be a long, long way from the center of the Earth. In fact, you wouldn't even have broken through the Earth's crust.

The Kola Borehole is 40,000 feet deep, but the outermost layer of the Earth's crust alone is 120,000 feet deep. You'd have to travel 20 million feet, or about 4,000 miles, to get to the exact center of the Earth - the center of the Earth's inner core.

Even if there is a deep and wide enough entrance to reach the center of the earth, how long do we imagine it will take to reach the bottom from the entrance? That may depend on the free sedimentation rate.

Normally, free fall velocity is the point at which the value of the drag (usually air drag) and the force exerted by gravity are balanced and canceled out, and the falling object no longer accelerates: that is, the object's speed no longer increases.

There are a lot of variables that come into play when it comes to speed, and we know that skydivers can reach freefall speeds of about 120 miles per hour while lying flat on their backs, on their stomachs. And rappelling skydivers (freefalling headfirst) can reach speeds of 300 miles per hour. All of this shows that, considering only speed, and assuming that the air resistance underground is about the same as the air resistance above the ground, the time it would take to reach the center of the earth while falling belly-down is about 33 hours and 20 minutes.

If you go upside down, it will only take 13 hours and 20 minutes. But in reality, these data will be greatly affected by the change of gravity... more on that later! Of course, in any case, reaching the center of the earth is not as simple as digging a hole deep and wide enough and throwing yourself in it.

In practice, you can't even survive a few moments in the process of reaching the Earth's inner core. In other words, even if you just want to reach the Earth's outer core, or even just the mantle, the primary difficulty is high temperature and high pressure, and you also need to overcome the problem of lack of oxygen.

The current standard oxygen tank can only last for about 5 hours, so you definitely need to carry more than one oxygen tank. Carrying these oxygen tanks will undoubtedly increase your free fall speed, so you will reach your destination faster.

But even so, let's imagine that you are performing this operation in the future when technology is more advanced and you have plenty of oxygen, so there is no need to worry too much.

There will be nothing but extreme heat and pressure. Generally speaking, although the temperature will vary depending on where you are, as you go deeper, the temperature will gradually increase, and it will be noticeably warmer than the surface just a few feet below the surface. As you move deeper, you will find that the pressure is generally increasing (and there will be more and more air pressing on you). Furthermore, let's say you have prepared yourself and put on a special suit specially made for the journey to the center of the earth, which can maintain your body temperature and ensure your survival. Do you know what kind of heat it will protect you from?

The Mponeng gold mine is the deepest mine in the world, 2.5 miles (about 4,000 meters) deep. It takes miners an hour to reach the bottom of the mine from the surface. Although the temperature inside the tunnel has been cooled to an acceptable level, the temperature of the rock at this depth has reached 60°C, which is higher than the highest temperature ever recorded on the ground. Going down further, this number will become even more amazing.

At the interface between the crust and the mantle, 20-30 miles (32-48 km) from the surface, the temperature is between 200-400°C. When this journey to the center of the Earth reaches the middle of the mantle, we are already 900 miles (1448 km) below the surface of our planet. Before you enter the outer core, we will first reach the bottom of the mantle, 1800 miles (2900 km) deep, where the temperature is 4000°C and the pressure is as high as 1.4 million atmospheres (1.4GPa). Although you may not be able to actually reach such a close to the center of the Earth through a hole, if you don't have an extremely advanced pressure regulation suit here, your body will be torn apart in an instant due to the huge pressure.

Once you enter the outer core⑤, you will face temperatures exceeding 7500℃ and a magnetic field fifty times stronger than the surface. Moving further into the inner core, the temperature will drop to 5500℃ - a relatively cool temperature, but at the same time the pressure will surge to 3.5 million atmospheres (3.5GPa). And our journey is not over yet, you still have a long way to go.

The radius of the inner core ⑥ is only about 750 miles (about 1,200 kilometers), which is about 70% of the radius of the moon. So if you continue to move at the free fall speed ⑦, you will only have 2-6 hours of travel, unless you stop moving at the original speed. This has to mention the role of gravity. As you move inward along the inner core, gravity will no longer have the same effect as on the surface.

The Mponeng gold mine is currently the deepest mine on Earth and is considered one of the most important gold mines. The mine is located in Carltonville, South Africa, owned by Harmony Gold, and produced 5.45 tons of gold in 2021. -China Gold News.2022.5.27.04-Mining-Overseas

The outer core is separated from the mantle by the Gutenberg-Weichert discontinuity. This discontinuity is a solid-liquid phase transition surface, indicating that the outer core is molten. The boundary between the inner and outer cores is about 5,145 kilometers deep, with a clear interface, which is the liquid-solid phase transition.

By now, most of the Earth's mass is usually above you, so the pressure of gravity feels weaker, which means your terminal velocity will be slower. Therefore, it's extremely difficult to predict how long it will actually take you to fall through the Earth, but it's probably a few weeks (and you can do it). Once you finally reach the center, what then? Do you really just fall in and out the other side? Not really. It's still gravity. You might fall off the Earth temporarily, but it won't be long before gravity kicks in again and pulls you back in the other direction.

You would then be caught in this back-and-forth motion until you eventually came to rest right at the center of the planet; the innermost region of the Earth's core, where you would feel as if you were weightless. It would be an unusual resting place, to say the least! In the real world, this is a journey you could never take. It would be physically unimaginable, practically impossible, so your bottom-phobia, your fear of falling, need not panic you just yet. But if there was a hole deep and wide enough, a decent supply of oxygen, and a super-advanced pressure suit that could withstand the extreme temperatures, then we could at least make this journey.

Anyone brave enough to venture into the Earth's dangerous depths would surely be hailed as a global hero and endless adventurer. But without some means of flying out to the other side of the planet, they too would eventually fall victim to gravity. And that's what would happen if you fell from the center of the Earth.

Fy: Xia Hyun, everything, bucket, this young man, Roserina