Why can the 3K glasses in The Three-Body Problem see cosmic microwave radiation?

Gou Lijun

Hello everyone, I am Gou Lijun from the National Astronomical Observatory. Today I will introduce to you the 3K glasses in the novel The Three-Body Problem.

In the novel, you can see the cosmic microwave background radiation by putting on glasses. Let us first introduce the cosmic microwave background radiation. What exactly is it? The cosmic microwave background radiation is the isotropic microwave radiation from the background of the universe. It is a relic of the Big Bang of our universe. We know that our universe was created by a big bang 13.8 billion years ago. After the explosion, the fireball expanded and then slowly cooled. 380,000 years after the explosion, because the temperature dropped, electrons and atoms combined, and the universe became transparent at this time. At this time, the average temperature of the universe reached 3000 Kelvin. After the photons generated were radiated outward, the universe continued to expand, and the temperature gradually dropped until it reached about 3 Kelvin as we know it now.

It should be noted that Kelvin is also a unit of temperature. The unit we use in daily life is Celsius. There is a linear conversion relationship between the two units. The difference is 273.15, which is what we often call 0 degrees Celsius, that is, when it freezes, if Kelvin is used as the unit, it is 273.15 Kelvin. And our current understanding is that zero degrees Kelvin is absolute zero. At this time, the movement of all objects, including atoms and molecules, will stop. So we can see that the temperature of the universe has been very high in the early days, and gradually decreased to the current 2.73 Kelvin. Of course, we can also use the corresponding wavelength to express it, but physicists find temperature more convenient.

Research related to cosmic microwave background radiation has won two Nobel Prizes. In the early 1960s, American scientists Pengias and Wilson established a high-sensitivity horn-type receiving antenna system to improve satellite communications. In 1964, in order to reduce noise, they even cleared the bird droppings on the antenna, but there was still centimeter-wave background noise that could not be eliminated. They believed that these wavelengths from the universe were 7.35 cm microwaves, equivalent to 3.5 Kelvin. In 1965, they revised it to three Kelvin and made the discovery public. For this, they won the 1978 Nobel Prize in Physics. Later, the US satellite made a precise measurement of the microwave background radiation and won the Nobel Prize in 2006.

We know that the temperature of the cosmic microwave background radiation is about 2.73 Kelvin. Microwaves are what we often call the radio wave band, so our naked eyes cannot see it directly. We must now detect it through appropriate detectors. In the novel "Three-Body Problem", the audience wears such glasses at night and can see the scattered background radiation of the universe and the cosmic flicker. In fact, so far, we have not yet realized such technology, but what is described in the article is just an imagination. Because we still have some other signals in this frequency band. For example, when we first discovered the cosmic microwave background radiation, this radiation was only equivalent to the noise. So even if we wear such glasses, it is difficult for us to directly see the microwave background radiation signal of the universe.

That’s all I have to say about 3K glasses for now. I’ll talk to you about some other related scientific knowledge when I have the chance.

This article is a work supported by the Science Popularization China Starry Sky Project. Author: Gou Lijun

Audit: Korean standard

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.