Is the Universe Really Full of Stars?

I enjoy watching documentaries about the universe. From the Big Bang and black holes to the end of the universe and the birth and destruction of Earth, there is no shortage of subjects. Watching these programs, I sometimes find myself wondering about strange things. Why is the universe so hot? The temperature of the cosmic background radiation is said to be about 2.7 K, or roughly minus 270 degrees Celsius. Yet in this extraordinarily cold universe, the surface of the Sun reaches about 5,500 degrees Celsius, and its core is 15 million degrees. Countless stars are even hotter than the Sun. Why does heat exist in the universe at all? If you throw a bucket of hot water across the floor of a bathhouse, the water spreads out in every direction and cools. The universe, too, was once filled with hot energy, which gradually cooled as space expanded. Yet in this cooling universe, gravity drew matter together, and that matter formed stars. The stars, in turn, emit heat and light.

Listening to this explanation, I thought of a pimple on the human body. Suppose our body temperature is 36.5 degrees Celsius. When a small patch of skin becomes inflamed, its temperature may rise slightly above that of the surrounding skin. Compared with the body as a whole, it is an insignificant spot. Yet once that pimple begins to bother us, our attention can remain fixed on it all day. We scarcely notice the rest of our skin, where nothing is wrong. Could the stars in the universe be something like those pimples? Even if we added together the volumes of every star in the observable universe, they would occupy an infinitesimal fraction of its total volume. Imagine a sheet of graph paper measuring one meter by one meter. Marking a single square measuring one centimeter on each side would not begin to convey the difference. The space occupied by stars is incomparably smaller still. And yet, when we look at the universe, the first things we notice are those very stars. The universe shown in astronomy documentaries is spectacular. Red nebulae, blue stars, spiral galaxies, and gigantic explosions fill the screen. Many images are colored representations of wavelengths invisible to the human eye. After watching such images for a long time, one begins to feel that the entire universe is a place overflowing with light and heat. In reality, most of the universe consists of the vast spaces between stars.

This led me to think about the observer's position. Earth lies near one of the Milky Way's spiral arms. When we look at the night sky, we see countless stars. In the direction of the Milky Way, they form a long band across the heavens. We have looked up at skies like this since birth, and astronomy was developed by people who grew up beneath those same skies. What if we went to Pluto? Suppose we installed a telescope like Hubble or James Webb there and observed the universe. Although Pluto lies billions of kilometers from the Sun, the galaxies photographed from there would look much the same as those photographed from Earth. Compared with the size of the universe, the entire solar system is little more than a single tiny point.

What, then, if we ventured toward the center of the Milky Way? Suppose we reduced the radius of the entire galaxy to one meter and placed Earth fifty centimeters from its center. Now imagine an Earth-like planet only ten centimeters from the center. Its night sky would be quite different from ours. With a much higher density of stars, countless points of light would shine in every direction. In some places, dust and gas near the galactic center would obstruct the view. Conversely, imagine an Earth-like planet in intergalactic space, millions of light-years from the Milky Way. There might be almost no stars visible in its night sky. Distant galaxies would appear faintly, but to the naked eye the universe would be almost completely dark. What kind of astronomy would a civilization born on such a planet develop?

This brings to mind what Kojin Karatani called the “discovery of landscape.” A landscape is not simply the natural scenery before our eyes. It also has to do with how people see and understand the world. Where we stand affects the landscape we see. And that landscape influences what we become curious about. People living on a planet near the galactic center would contemplate the universe while looking at a sky crowded with stars. People living on an isolated planet between galaxies would contemplate it while looking at a sky in which almost nothing was visible. The questions they first asked would not be the same as those asked by humans born on Earth. Perhaps they would discover certain laws of nature before we did, while taking much longer to discover things that came easily to us. Even though they lived in a universe governed by the same physical laws, their observational data and their starting points for research would be different. Two civilizations that had advanced sufficiently might eventually reach the same conclusions. There is no reason to assume that they would have begun with the same questions or followed the same path.

Thinking along these lines also makes me question how we calculate the possibility of extraterrestrial civilizations. Astronomers estimate how many stars exist in the universe, how many planets orbit an average star, and how many of those planets might support life. There is even an equation for estimating the possible number of extraterrestrial civilizations. Such calculations are certainly necessary. The problem lies in the process of turning the number of planets into the number of civilizations. Suppose there are eight billion people on Earth. Some are born into prosperous circumstances, while others are born into poverty. Some children grow up using computers, attend good schools, and have opportunities to develop their abilities. Others struggle simply to find enough to eat each day. Even if two children possess equally exceptional intelligence, their chances of putting that intelligence to use are not equal. How gifted a person is and whether that person can actually make use of those gifts depend heavily on the surrounding environment.

The same may be true of planets throughout the universe. Some orbit stable stars, while others orbit stars with short lifespans and violent activity. Some have water and suitable atmospheres, while others experience extreme temperature changes and intense radiation. In densely populated regions such as the galactic center, the likelihood of exposure to interactions with neighboring celestial bodies or explosive astronomical events may also differ. Even if life emerges in such an environment, whether it can develop into a civilization is another question entirely. On a planet where single-celled organisms have appeared, it may take billions of years for complex life to emerge. Even if intelligent life evolves, it may fail to develop tools and language, or become extinct before establishing an industrial civilization. Even if countless planets possess conditions similar to Earth's, there is no guarantee that civilizations like ours will arise on them.

Let us say that humanity has spent roughly three million years evolving from distant ancestors such as Australopithecus. The exact date is not important. Throughout those immense stretches of time, humans searched for food, chipped stones, and made tools in order to survive. Yet the progress humanity has achieved in the ten thousand years or so since the beginning of the Neolithic period is astonishing. Humans began farming, built cities, invented writing, and developed mathematics and science. They built steam engines and began using electricity, then took to the skies in airplanes. Eventually, they sent humans to the Moon and landed probes on Mars. The Voyager spacecraft have left the heliosphere and are traveling through interstellar space. I do not believe human intelligence alone can explain all this. Prosperity mattered. If people must spend every hour of the day digging potatoes out of the ground, they can hardly devote themselves to researching machines that fly through the sky. Observing the wings of birds and designing flying machines, as Leonardo da Vinci did, has little direct connection to producing food for immediate survival. Science and art can develop only when there are people and societies able to undertake such pursuits. As humans increased productivity and accumulated food, they gradually freed themselves from some of the labor required for survival. Cities and educational institutions emerged. Some people could devote their entire lives to mathematics, while others observed the stars. The knowledge they discovered was passed down to subsequent generations.

The changes since the Second World War have been particularly remarkable. Under the international order led by the United States, the major industrialized nations were able to develop their economies and invest in science and technology over a relatively long period. There were numerous wars, including the Korean War, the Vietnam War, and the Iran–Iraq War, but global production and the accumulation of knowledge did not come to a halt. Economic prosperity, expanded education, the development of research institutions, and investment by governments and businesses came together. Competition and military needs also accelerated technological progress. One result of all that accumulated effort is artificial intelligence. Today, we can sit in front of a computer, ask a question, and have AI organize information from countless fields, from cosmology to ancient philosophy, almost instantly. Just a few decades ago, doing the same thing would have required visiting several libraries and searching through books. Yet AI sometimes presents false information as if it were true, or repeatedly agrees without evidence simply to please the person asking the question. At times, it cannot admit that it does not know something. Whenever I experience this, I feel a peculiar sense of unease. Humanity has created machines capable of handling enormous quantities of knowledge, yet we have not even properly solved the question of how far we can trust what those machines tell us.

Countless conditions had to come together for Earth to produce the technological civilization we have today. A suitable star and planetary environment, the emergence of life, a long history of evolution, intelligence and language, agriculture and cities, the accumulation of knowledge, advances in productivity, and social stability all had to follow one another. If any one of these conditions had gone seriously wrong, humans might still be carrying stone axes. Perhaps we would already be extinct. Humanity now possesses weapons capable of destroying itself. The results of millions of years of evolution and thousands of years of civilization could be destroyed in a matter of hours.

Whenever I think about this, Donald Trump comes to mind. Trump has been elected president of the United States, the most powerful country in the world, twice. The United States sent humans to the Moon, led advances in the internet and artificial intelligence, and possesses the world's most powerful military. Yet I sometimes find it difficult to believe the things its president says and does in public speeches. In 2015, during a campaign rally, Trump referred to Serge Kovaleski, a journalist with a congenital joint condition, while moving his arms awkwardly in an apparent imitation of the journalist. He was criticized for mocking the journalist's disability. Trump denied that he had been imitating a disability, but footage of the incident remains. I saw a similar scene during the 2026 U.S. Senate election in Michigan. The Democratic candidate, Abdul El-Sayed, was born in the United States to Egyptian immigrant parents. At a campaign rally, Trump called him “Abdul Mohammed El-Sayed” and attacked him as a jihadist and a member of the Muslim Brotherhood. He even said that El-Sayed would have to pass through a metal detector to enter the Senate. No evidence was presented to support the claim that El-Sayed was associated with such extremist organizations. El-Sayed ultimately won the election.

When I see scenes like these, I am struck first by the attitude of the person speaking, rather than by his policies. It is perfectly natural for a politician to criticize another politician's policies. He may also attack his opponent's ideology and political judgments. But when I see the president of the world's most powerful country mocking someone's name, invoking religious prejudice, and imitating the movements of a person with a disability in an official speech, I begin to wonder how seriously he regards the power he holds. This is not a private gathering where friends are joking among themselves. It is an official occasion at which a president is speaking before countless citizens. His words are broadcast around the world and preserved in the public record. What astonishes me even more is that such a person has twice become president of the United States through democratic elections. Democracy is a political system humanity has developed over a long period. Citizens elect those who govern them, divide power among institutions, and use laws and constitutional arrangements to limit abuses of authority. The United States became a global power on the foundations of that system. Yet even within such a system, a person like Trump can attain the highest office in the country.

At least the United States has Congress and the courts, a federal system, laws, and the separation of powers. Its structure does not allow a single president to decide absolutely everything as he pleases. But the thought of nuclear weapons makes me more apprehensive. The American president possesses immense authority to authorize their use. The consequences of an ordinary person speaking in a moment of anger are entirely different from those of a president making a decision in a moment of anger. When I think about this, human civilization begins to feel like an enormous house of cards. Earth has existed for 4.6 billion years. Life has evolved over billions of years, and humans have taken millions of years to become what we are today. Progressing from stone axes to spacecraft required the labor and discoveries of countless generations. Yet here, at the heart of a civilization built over such immense stretches of time, the president of the world's most powerful country publicly mocks another person's name, imitates a disability, and receives the cheers of a crowd.

I began writing this essay after seeing the news that Abdul El-Sayed had been elected to the U.S. Senate from Michigan in the 2026 midterm elections. I live in South Korea, and I do not know much about his policies. Even so, I want to congratulate him on his victory. I believe no one should be publicly mocked by a president because of their name or religion.

I look up at the night sky again. The space occupied by stars is infinitesimal compared with the vastness of the universe. Beside one of those stars, the Sun, humanity evolved over millions of years and eventually built a civilization capable of studying the very birth of the universe. In a universe so cold and immense, even the formation of a single hot star can hardly be taken for granted. Yet I find it strange that a civilization born beside such a star, having advanced so far, still entrusts its fate to someone like that.