Black body can not only absorb all electromagnetic radiation from the outside, but also be better than any other object at the same temperature.

The distribution of blackbody radiation energy according to wavelength is only related to temperature.

The study of blackbody makes the quantum effect in natural phenomena discovered.

Maybe let's put it another way:

The so-called blackbody radiation is actually the phenomenon that light and matter in local state are in equilibrium: matter is in equilibrium, so it can be described by a temperature, and the interaction between light and matter is very strong, so light and light can also be described by a temperature (light itself does not interact, but the interaction between light and matter is very strong). What describes this relationship is Planck distribution.

In reality, blackbody radiation does not exist, but it is very approximate (like in a star).

For example, we observed cosmic background radiation (CMBR), which is equivalent to about 3K blackbody radiation.

This means that in the early universe, light and matter were in balance. As time goes on, the temperature drops slowly, but the form of the function remains the same (or bold). (The effects of frequency and temperature cancel each other out)

1948, Alf and Herman predicted that the residual radiation scattered by the Big Bang was due to the expansion of the universe.

And now its temperature is about 5℃ higher than absolute zero, or 5 K (absolute zero

The temperature is equal to -273 degrees Celsius, that is -273 degrees Celsius). But their predictions did not arouse people's enthusiasm.

Concern, but buried in the vast sea of physical literature. Several other scientists believe that.

The origin of the expanding universe, but they don't know Alf and Herman's paper. as a result of

Very clear. At that time, communication and communication were not the same as today. In the 1940s and 1950s,

For most physicists, recreating the details of the early history of the universe is not a very serious science.

Activities. But many years later, that is, 1965, two wireless electricians in Bell Laboratories, New Jersey, USA.

Shicheng arno penzias and robert wilson.

However, when they tried to track the first echo, they found this cosmic radiation field very unexpectedly.

(Echo) satellite and calibrate a very sensitive radio antenna. Meanwhile, the prince nearby.

At Leiden University, a group of scientists led by Robert Dick has independently

The early predictions of Alf and Herman were rediscovered, and a detector was designed to search.

Residual radiation from the big bang. They heard that there was something unexplained in this receiver at Bell Labs.

Noise, and immediately interpret it as the residual radiation of the big bang. It is equivalent to the electromagnetic spectrum.

The microwave part is a radio wave signal with a wavelength of 7. 35cm If thermal radiation is assumed, then

It has energy corresponding to the temperature of 2. 7K, which is similar to that of Alf and Herman.

The estimate of feeling is very close. It is called "cosmic microwave background radiation" as the beginning of its prediction and discovery.

Finally, it should be mentioned that 1983, people began to understand the radio physics of the former Soviet Union.

Shmaonov may have discovered this radiation as early as 1957 and published it in Russian.

This fact was spread. Shimonoseki built an antenna sensitive to microwave signals, and it was reported that it was detected.

All directions in the sky get some kind of uniform signal, and the corresponding radiation has a range between

1K to 7K. At that time, neither he nor anyone else knew the importance of this discovery.

Make love. In fact, it was not until 1983 that Shimanov heard about BIGBANG's prediction and penzias and Will.

Johnson's discovery, and this is 18 years ago, the last two people who won the Nobel Prize for making outstanding discoveries.

That was five years after the Nobel Prize.

This discovery is a signal that people begin to seriously study the big bang model. Gradually, people

More observations have been made on cosmic microwave, revealing the differences of cosmic microwave background radiation.

Quality. The intensity of this radiation is the same in all directions, and the accuracy is at least one thousandth.

Moreover, people measured its intensity at different frequencies and began to reveal the square of its intensity changing with frequency.

The formula (that is, its "spectrum") has the characteristics of pure heat. This kind of radiation is called "blackbody" radiation. Unfortunately.

In fact, the absorption and emission of radiation by molecules in the earth's atmosphere prevented astronomers from confirming the whole.

The background radiation spectrum is indeed a thermal radiation spectrum. People still suspect that it may be caused by the expansion of the universe.

There have been various violent incidents for a long time, not the expansion about 654.38+0.5 billion years ago.

At first, only by observing this radiation outside the earth's atmosphere can these doubts be dispelled, and this is precisely the United States.

NASA's Cosmic Background Detector (COBE) satellite began to measure the whole from space in 1989.

The first great achievement of the background radiation spectrum (see Figure 2.6). This is what people see in nature.

The most perfect blackbody spectrum, it is very surprising to confirm that the universe used to be thousands of times hotter than it is now.

Tens of thousands of degrees. Because only under such extreme conditions can the radiation in the universe appear in the form of black body.

To achieve such high accuracy.