Modern humans can go up to the sky, but also down to the sea, but in the "sky" and "down to the sea" on these two things, humans obviously prefer "up to the sky".

Compared to the exploration of space, human research on the Earth's oceans is far from enough. In the current situation, mankind has explored only 5% of the Earth's oceans.

Why would humans prefer to explore space rather than study the deep ocean?

The high pressure in the deep sea, you know that every 10 meters increase in water depth, the pressure in the ocean will increase by almost 1 atmosphere, and the average depth of the Earth's oceans is about 3700 meters, the pressure of this depth can reach 370 atmospheres, which is equivalent to an area of 1 square centimeter to bear the weight of 370 kilograms.

Such an extremely high-pressure environment, greatly limits the ability of human action in the deep sea, even with a special submersible dive into the deep sea, humans will face greater risks.

Of course, although the deep sea for humans is indeed very scary, human research on the deep sea does not necessarily personally go to the deep sea for "fieldwork". After all, the process of human exploration of space usually uses only unmanned equipment or long-distance detection means.

So, why do not humans use unmanned equipment or long-range detection means to study the deep sea?

When using unmanned devices at a distance, we need a carrier to establish wireless communication with them in order to instantly control their actions and obtain the data they send back, and when conducting long-range exploration, we also need a carrier to obtain information about the exploration target.

As we know, the carrier used by humans to explore space is actually electromagnetic waves. However, in the deep sea, electromagnetic waves are not "useful", why? Because electromagnetic waves in the water will be violently attenuated, and because of this, the deep sea is a terrible darkness, after all, visible light is actually an electromagnetic wave.

Without the "help" of electromagnetic waves, humans can only find a way to use another carrier, that is, sound waves. The reason is that sound waves are mechanical waves, the attenuation of their propagation in the water is far less than electromagnetic waves, and can be spread over long distances in seawater.

Although sound waves can also be like electromagnetic waves and unmanned equipment to establish wireless communication (which is also known as "hydroacoustic communication"), or access to detect the target information, the use of sound waves in the deep sea there is many problems, mainly the following points:

1, In the process of propagation, sound waves will be due to the uneven distribution of seawater medium, the surface, the impact of the sea floor interface and other factors such as random scattering, refraction, reflection, and interference, which will cause different moments, different intensity of the acoustic signal overlap each other, and then produce similar reverberation effect.

2, The surface of the ocean wave fluctuations and deep-sea dark currents, can easily lead to rapid changes in sound waves.

3, Environmental noise in the ocean, such as marine life or the sound of human ships, will significantly increase the difficulty of communication using sound waves.

4, Sound waves are also attenuated when propagating in seawater, and the higher the frequency attenuation is more severe, which results in the ability to use the signal bandwidth is very limited.

5, Compared with electromagnetic waves, the propagation speed of sound waves is too slow, even if the sound waves in water propagate speed than in the air, but also can only reach about 1500 meters per second, in this case, if the surface or underwater equipment relative motion (which is very common), it can produce a very obvious Doppler effect, which leads to the receiver can not correctly identify the information it carries.