It is often said that the universe is a vast dark world, filled with infinite cold. However, this common view is not entirely accurate. Why is the universe cold and dark? Isn't the heat of the sun enough to warm the space of the universe? This question has been bothering scientists for a long time, leading to an in-depth exploration of the mysteries of the universe. In the process of exploration, we gradually uncover the hidden secrets behind the universe and discover a series of amazing facts.
The Warmth and Coldness of the Universe: Cosmic Microwave Background Radiation and Cosmic Expansion
Let's talk about cosmic microwave background radiation. This is a type of electromagnetic radiation that exists in the universe and is emitted about 380,000 years after the Great **. At that time, the universe was too hot to form an atomic structure. However, as the universe expands, the temperature gradually drops and atoms begin to form. When electrons combine with protons to form hydrogen atoms, it is called "cosmic reionization". The radiation emitted by this process is the cosmic microwave background radiation.
The existence of cosmic microwave background radiation proves that the universe was once an extremely hot place, and that the universe today has become relatively cool. Through the observation and analysis of cosmic microwave background radiation, scientists have successfully explained the origin and evolution of the universe. This radiation is almost uniform, coming from all directions, and exhibits spectral lines typical of blackbody radiation. This discovery further supports the theory that the universe originated at a point of extreme heat and density.
However, the cooling of the universe is not just due to the presence of cosmic microwave background radiation. The expansion of the universe is also an important factor in the cooling of the universe. According to the theory of cosmic expansion, the rate at which the universe expands determines the rate at which the universe cools. As the expansion of the universe accelerates, so does the temperature in the universe.
The theory of the expansion of the universe was first proposed by Alexander Friedman and George Böttel in 1920. Based on Einstein's theory of general relativity, they derived equations describing the expansion of the universe. Later, their theory was supported by Hubble's observation that the universe was expanding by observing the redshift phenomenon of galaxies.
The reason why the universe cools down due to the expansion of the universe is that the expansion dilutes the matter in the universe. As the universe expands, matter collides with each other becoming more sparse, reducing energy transfer and heat conduction. This causes a gradual drop in temperature in the universe. If the universe does not expand, then the heat energy will be more concentrated and the temperature will be higher.
The Darkness of the Universe: The Role of Dark Matter and Dark Energy
Let's explore dark matter. Dark matter refers to a substance that cannot interact with electromagnetic waves and therefore cannot be directly observed. However, by studying the gravitational effects of objects in the universe, scientists have discovered an unexplained gravitational effect. It has been calculated that this gravitational effect can only be explained by the presence of dark matter. According to available observations, dark matter accounts for about 27% of the total mass of the universe. In other words, less than one-third of the mass in the universe is made up of visible matter as we know it, and the rest is mysterious dark matter.
So, what role does dark matter play in the universe? First of all, dark matter is an important support for the formation and stability of the structure of the universe. The visible matter in the universe, although massive, is relatively small and cannot generate enough gravity to maintain the stability of galaxies. The presence of dark matter provides additional gravitational pull, allowing galaxies to attract each other and maintain structural stability. In addition, dark matter also plays an important role in the movement of stars within galaxies. Due to the gravitational pull of dark matter, stars in galaxies are able to be more closely grouped together, forming stable structures such as globular clusters.
Next, let's take a look at dark energy. Dark energy refers to a uniform form of energy with negative pressure, which is described by the "cosmological constant" introduced by Albert Einstein. Dark energy exists to explain the phenomenon of accelerating expansion of the universe. At the end of the 20th century, scientists' observations of the expansion of the universe found that, contrary to our expectations, the expansion of the universe was accelerating. To explain this phenomenon, scientists have put forward the hypothesis that there is an unknown form of energy in the universe, namely dark energy. According to current observations, dark energy accounts for about 68% of the total energy in the universe.
And the role of dark energy is also crucial. Its existence can help us explain the acceleration of the expansion of the universe. According to scientists' speculation, dark energy is a type of energy with an anti-gravity effect that drives the expansion of the universe by creating negative pressure. This anti-gravity effect cancels out the gravitational pull between galaxies, accelerating the expansion of the universe. Dark energy has actually become the dominant factor that governs the evolution of the universe, and it has shaped the structure and development of the universe.
The Gradual Cooling of the Universe: The Second Law of Thermodynamics and the Cosmic Redshift
Let's take a look at the second law of thermodynamics. The second law of thermodynamics is the law that describes the direction of heat transfer in nature, also known as the law of entropy increase. In simple terms, the second law of thermodynamics states that heat does not transfer itself from a cold object to a hot object unless there is an input of external energy. This law tells us that systems in nature always tend to be disordered and entropy-increasing. In other words, the energy of the system tends to dissipate and disappear.
Next, let's take a look at the phenomenon of cosmic redshift. Cosmic redshift is an astronomical phenomenon in which light rays in galaxies or objects far away from us become longer in wavelength, appearing red. This is caused by the expansion of the universe causing the space between objects to stretch. According to Einstein's theory of general relativity, the expansion of the universe can be seen as an expansion of space-time, resulting in an increase in the distance between objects. As light travels through such stretched space, their wavelengths also become longer, showing a cosmic redshift.
So, what is the relationship between the second law of thermodynamics and the redshift of the universe? We know that the second law of thermodynamics requires the energy of the system to dissipate and disappear, and the cosmic redshift means that the space between objects in the universe is constantly expanding. Both of these phenomena suggest that the universe is getting colder.
As the universe expands, the distances between objects increase, and the energy in the universe becomes more dispersed and sparse. It's like putting a hot cup in a cold room, and because the heat can't be transferred to the whole room on its own, eventually the heat in the cup will dissipate and disappear, causing the temperature inside the cup to drop. Similarly, the expansion of the universe leads to the dispersion of energy, causing the temperature in the universe to gradually decrease.
So, how long will the gradual cooling of the universe last? According to scientists, the gradual cooling of the universe will be a long process. According to the available observational data, the current rate of expansion of the universe is accelerating, which means that the temperature of the universe is getting lower and lower, and the trend to continue to develop to lower temperatures is intensifying. However, because gravity and other forces still work in the universe, we cannot be precise about the ultimate fate and temperature of the universe. Some theories suggest that at the end of the universe, there may be a heat death state, in which the universe cools to the point of near absolute zero.
The Void of the Universe: The universe is essentially a network of spaces with a large number of voids
In the past, people often thought of the universe as an infinite void where no matter or energy existed. However, with the advancement of science and technology and the improvement of observation instruments, we have begun to discover that there are various galaxies, nebulae, planets and other celestial bodies in the universe. These observations make people wonder what the nature of the universe really is.
In recent years, scientists have come to an astonishing conclusion through the study of cosmic microwave background radiation: the universe is essentially a spatial network structure with a large number of holes. The so-called void refers to the existence of some huge void areas in the universe, and the distribution of matter inside is very sparse compared to the surrounding matter. The spatial network structure refers to the existence of a network connection between these holes, which are intertwined and interspersed with each other to form an intricate network. This network has had an impact on our perception of the universe.
The discovery of holes and spatial reticulation has not only changed our understanding of the universe, but also helped explain some astronomical phenomena that were previously difficult to understand. For example, the uniformity of cosmic background radiation was originally thought to be due to the fact that the universe originated at one time, but now we can explain this phenomenon through holes and spatial reticulation. In the initial stage of the universe, the distribution of matter was not uniform, and there were various holes of different sizes, and the distribution of these holes formed a statistical uniformity, that is, the uniformity of the cosmic background radiation that we observed.
Voids and spatial reticulation also help explain the formation and evolution of galaxy clusters in the universe. In the early days of the universe, due to the accumulation of matter and gravity, the voids were gradually filled, forming clusters of galaxies. The distribution of such holes and galaxy clusters is due to the existence of a spatial network structure, which makes the material organization in the universe more orderly.
However, although we have discovered the void and spatial network structure of the universe, we still know nothing about their origin and nature. Scientists are still conducting further research trying to unravel the mysteries of the universe.
The wonder of the universe: The cold and dark of the universe is the key condition that supports life
Let's explore the low temperatures of the universe. According to scientists, the average temperature of the universe is about minus 270 degrees Celsius, which is close to absolute zero. Such an incredibly low temperature freezes everything into a frozen state. But it is precisely this cold temperature that creates the basic conditions for the existence of life.
The low temperatures of the universe slow down the movement of molecules, making matter more stable. This stability helps the chemical reactions between molecules to be carried out, so that the basic molecules of life such as proteins, nucleic acids, etc. can be formed. If the temperature of the universe is too high, the movement of molecules will become too violent, causing chemical reactions to be unable to carry out, and the basic substances of life cannot be produced.
Extremely low temperatures also help maintain the stability of life. Many biochemical reactions in living organisms need to be carried out within a specific temperature range, and the low temperatures of the universe provide a stable environment. It is precisely because of the cold of the universe that life on Earth has been able to adapt to its environment over hundreds of millions of years of evolution, and has evolved into the diverse biomes it is today.
Next, let's explore the darkness of the universe. Although the universe is full of bright stars, for human beings, the universe is pitch black. This is because there is a lot of dark matter and dark energy in the universe, which does not interact with light, so it cannot be seen by us.
However, it is precisely because of the darkness of the universe that galaxies are formed and evolved. The gravitational pull of dark matter causes the stars in galaxies to attract each other, creating beautiful galactic structures. The presence of dark energy accelerates the expansion of the universe, making galaxies more distant from each other. This expansion of the universe provides a broader space for the birth and evolution of life.
The darkness of the universe also brings about a wonderful phenomenon: the twinkle of the stars. When we look up at the starry sky, we see not that every star is shining continuously, but that it is a faint glow. This is because the light of the stars interacts with the gases and dust in the universe as it travels through the universe, creating scattering and absorption. Together, these faint rays of light make up the splendor of the universe and take us on a dreamy interstellar journey.
In conclusion, the inability of the sun's heat to heat the cosmic space adequately is the main reason why the cosmic space is cold and dark. While this makes people sigh at the infinite vastness and mystery of the universe, it also reminds us to cherish the warmth of the earth and the wonder of life.
Proofreading: Plain and tireless.