When astronauts are outside in space, they wear special protective suits, complete with airtight helmets, oxygen supplies, and communication devices equipped with microphones positioned near their mouths. However, despite being inside these suits, they are still in a vacuum. So, how can they hear, call, and communicate with each other?
In space, astronauts can still communicate with each other.
In fact, all our communication devices use radio waves for transmission. Radio waves behave like light; they do not require air to propagate, and they operate more efficiently in a vacuum. All electromagnetic waves, including visible light, do not need a medium to travel through, which is why they transmit fastest in a vacuum—at 300,000 km/s. This is how the Sun’s electromagnetic radiation travels to our Earth—across 150 million kilometers of high vacuum space.
To understand this better, we need to explore the mechanism of phone communication.
The telephone is one of humanity’s greatest inventions, emerging in the 18th century and officially used as a communication device in the mid-19th century. The first person to patent the invention of the telephone was the British inventor Alexander Graham Bell, who filed for the patent in March 1876, making him known as the father of the telephone.
Alexander Graham Bell – inventor of the telephone.
Alexander Graham Bell was a Scottish inventor, scientist, and reformer. Born and raised in Edinburgh, Scotland, he emigrated to Quebec, Canada in 1870 and later to Boston, Massachusetts, USA in 1871, becoming a U.S. citizen in 1882.
However, on June 15, 2002, the U.S. Congress passed Resolution 269, affirming that Antonio Meucci was the true inventor of the telephone, as he first demonstrated his invention to the public in 1860 and published about it in an Italian newspaper.
On June 15, 2002, the U.S. Congress passed Resolution 269 affirming Antonio Meucci as the true inventor of the telephone.
Antonio Meucci was an Italian inventor who developed a form of voice communication device in 1857. Many believe that Meucci is the true inventor of the telephone.
In this way, we implicitly acknowledge that there are two fathers of the telephone, but we still lack a clear conclusion on who actually created the first telephone for humanity. Therefore, we will set this issue aside to discuss the operating principles of the telephone.
After the invention of the telephone, from the simplest point-to-point calls, it gradually developed into long-distance calls, multi-party calls, video calls, etc., evolving from manual switching to rotary dialing, programmable phones, dual-tone multifrequency phones, and so on. With the emergence of modern technologies, Internet phones and digital mobile phones have provided increasingly convenient methods for making calls.
However, regardless of the mode of operation, the essence of the telephone remains unchanged: speaking at one end, answering at the other, and communicating through voice. The basic principle is that people produce sound waves through their mouths, which are transmitted to a microphone. The microphone converts sound waves into sound vibrations through its receiving devices, then changes the intensity of these vibrations into varying electric currents.
The electric current is transmitted to the recipient’s phone via wires or radio waves, and the receiving device in the phone converts the electric current back into sound vibrations through a process that reverses the transmitting devices, then converts these into audible sound waves delivered through the air to the ear. In this way, both parties in the call establish a communication channel.
By examining the basic operating principles of the telephone outlined above, it becomes clear that in addition to transmitting electric waves, the telephone also requires a fundamental and indispensable transmission medium—sound waves. Without sound waves, the telephone cannot transmit or receive voice.
Therefore, astronauts outside in space, dressed in special protective suits, can indeed hear and make phone calls normally. However, if they were to remove those suits in a vacuum, sound would be unable to propagate. Why is that?
Electromagnetic waves can transmit without a medium, while sound waves cannot.
Sound waves are mechanical waves. The difference between mechanical waves and electromagnetic waves is that electromagnetic waves can transmit without a medium, while sound waves require a medium to propagate. The simplest and most common medium is air, and sound can only travel through the vibrations of air and other materials. Sound waves travel at about 340 m/s in air and even faster in steel, at approximately 5,200 m/s.
And naturally, in a vacuum, there is no medium for transmission, so even if you do not suffocate to death in this environment, sound would have no way to reach the microphone. If the listener is also in a vacuum, due to the absence of sound wave vibrations, sound cannot travel through the outer auditory canal to the eardrum, and thus, the sound from the microphone cannot be heard.
Therefore, in a vacuum state, without special protective suits and oxygen, humans cannot only fail to survive but also cannot produce sound, nor can they make or receive calls.
