Carl sagan and the navigator.
1 In August and September, 1977, Voyager1and Voyager 2 started their own journeys respectively. Each of them carried a gold record with sound and images. These two records were written by carl sagan, and they are the civilized signals sent by the earth people to outer space. Some people say that in the distant future, after the extinction of mankind, these two records may be the only traces left by mankind.
This is a record that can be preserved in the universe for 1 100 million years. It contains 55 greetings to extraterrestrial life in human languages (4 from China), 90 minutes of music recordings from various countries (representing the famous guqin music "Mountain Flowing Water" in China), a song "Voice of the Earth" and 1 18 photos showing the earth and human beings.
In addition to the interstellar record, Voyager 1 also took a famous photo "Dim Blue Dot". In this photo taken 6.4 billion kilometers away from the earth, the earth is just a pixel as fine as dust. This photo greatly shook people's understanding of the earth, and it was carl sagan who proposed to take this photo. Before him, no one thought of looking back at the earth in the depths of the universe.
Carl Sagan's Theory of the Universe
The galaxies in the universe are rapidly moving away from each other. These galaxies are remnants of the Big Bang. Some scientists believe that our universe is just one of many universes-maybe countless. Some can grow, then shrink and collapse, from birth to death in an instant. Others will expand indefinitely. Some universes have just the right physical conditions, so they can contract and collapse after expansion, then begin to expand and then contract and collapse, and so on, from expansion to contraction and collapse, many times. It has been about 654.38+0.5 billion years since our universe was born in the Big Bang.
Other universes may have different physical laws and forms from ours. In these universes, there may be no life, or there may be no sun and planets. Of course, other universes may be more mysterious, broader and richer than our present universe. But if these universes exist, we may never be able to explore their mysteries, let alone visit them. After all, with today's technology, we are too busy to understand our own universe.
There are hundreds of billions of galaxies in our universe, one of which is the Milky Way. We like to call it "our galaxy", even though we don't own it at all. There are many gases and cosmic dust in the Milky Way, and there are about 400 billion planets. One of them, on an ordinary spiral arm in this galaxy, is our sun and the nearest regional star-as far as we know, the sun is a monotonous and not excellent ordinary planet, rotating around the center of the Milky Way with a period of 250 million years. At the center of the Milky Way is a small world like a follower. In these small worlds, there are planets, satellites, asteroids and comets. We humans live on the third smallest planet from the sun, which we call the earth. We are just one of the 500 billion biological species that have evolved and grown on this planet. We have launched a spaceship to explore 70 other planets in the solar system. We have entered the atmosphere of four of these worlds or landed on their surfaces. These four worlds are: the moon, Venus, Mars and Jupiter. We are doing a fabulous job.
The nebula hypothesis is confirmed.
The orbits of Jupiter and other planets in the solar system are all on the same plane, as if they were lines on a phonograph record or CD. Why is this happening? Why are the orbital planes not inclined to each other? Isaac Newton, a great mathematical genius, explained how gravity makes planets revolve around the sun, but he couldn't explain why the planes of these orbits almost coincide, so he asserted that at the beginning of the creation of the solar system, God must have put all the planets on the same plane to rotate.
However, a mathematician Marquis of Pierre-Simon Laplace and a very famous philosopher Immanuel Kant later discovered the reason why these orbits are almost always on the same plane even without the help of God. Unexpectedly, they applied the physical principles discovered by Newton. Kant-Laplace's simple hypothesis is this: between the stars, there is an irregular and slowly rotating dust cloud gas. There are many such clouds in the universe. If their density is high enough, the attraction between dust clouds and gases distributed everywhere will be so great as to restrain their irregular motion, and then the clouds and gases will begin to shrink. When it contracts, its rotation will be accelerated, which is the same as when a girl in figure skating takes back her outstretched hand and rotates with the tip of an ice blade. This rapid rotation will not prevent the collapsed cloud gas from contracting along the rotation axis, but will prevent the gas located in the rotation plane from contracting. So this originally irregular cloud gas will become a flat dish-shaped object. Therefore, the planets gathered on this flat dish-shaped object will all run on the same plane-only the laws of physics are enough, without the help of supernatural forces.
It is one thing to assume that this disk-shaped cloud gas existed before the formation of the planet, but it is another matter to actually observe that this disk-shaped cloud gas rotates around other planets. After discovering other spiral galaxies similar to the Milky Way, Kant thought that these were the forward nebulae and gas disks he predicted, so he claimed that the "nebula hypothesis" (nebulae are Greek cloud gases) was confirmed. However, people later learned that these spiral nebulae are actually very distant galaxies full of planets, not the places where planets and planets were born.
It is not easy to find a cloud disk that really revolves around a star. It was not until more than a century later, with the help of instruments (including astronomical observatories orbiting the earth), that this nebula hypothesis was really confirmed. When we observe young planets similar to the sun (similar to the sun 4.5 billion years ago), we find that about half of them are surrounded by "disks" made of gas and dust. This is not absolute evidence, but it gives us a powerful revelation-there are often (not without exception) companion stars around stars like our sun. This discovery has expanded the number of planets in the Milky Way (estimated at several billion).
However, how to directly observe these planets? These planets are very far away from us-the nearest distance is almost 65.438+0 billion astronomical units-and in visible light, the light emitted by the planets reflects the light of the main star (star), which is far weaker than the light emitted by the main star itself. However, our science and technology have made progress in the form of the Great Leap Forward. Can't we at least find a big planet like Jupiter near the neighboring planets? If you can't find it in visible light, can you find it in infrared light?
Looking for a new world
When it comes to the possibility of life on woody planets, I can only say that Jupiter is similar-almost impossible. However, these wooden planets are likely to have satellites, just like our Jupiter has 16 satellites. These satellites, like their planets (such as the wood-like planet of Virgo 70), are very close to the main star, so the temperature of these satellites may be mild. These planets are only 35 to 40 light years away from us, which is very close in terms of interstellar distance. At least imagine that one day, we will launch a very high-speed spaceship to visit them, and the data sent back will be analyzed by our descendants.
At the same time, many other technologies are emerging. In addition to the sudden change of pulsar synchronous rotation and the Doppler effect of measuring the wavelength change of stars, we also have ground interferometer or better space interferometer; Large telescopes on the ground can eliminate the interference of atmospheric airflow on images; Ground observation is carried out by using the principle of gravitational lens caused by distant heavy objects; Extremely accurate space telescope: you can observe the tiny brightness changes caused by the planet blocking a tiny part of the starlight when it passes in front of the main star. In the following years, it seems that the development of these technologies can reach the level of practical application. Therefore, we can expect some very important detection results in the future. We are about to enter an era when we can cruise among thousands of neighboring stars, and we will freely explore the companion stars of these planets. In the next decade, we are likely to get information about hundreds of extrasolar planetary systems-perhaps, in these alien "solar systems" (referring to extrasolar planetary systems), there will be several small blue worlds, which are endowed with oceans, oxygen and atmosphere, as well as signs of life that we think are miracles.
Book Introduction
This is a "book of prophecy" written more than 20 years ago, and it is also a popular science book that reflects the current realistic dilemma. Carl. Sagan finished his last work in his hospital bed, and he looked at the important issues related to human destiny in the 2 1 century with wise eyes. From environmental protection to abortion rights, from restricting nuclear weapons to space exploration, these beautifully written and lively articles not only show the vastness of the universe, but also touch the soft corners of human hearts. In the last chapter of this book, Sagan rarely reveals his attitude towards life, love, death and faith in his works, bravely facing death and thanking life for giving us short and rich opportunities.
Brief introduction of the author
Carl. American astronomer carl sagan (1934— 1996) is one of the most famous popular science writers in the 20th century. He used to be the director of the Center for Planetary Research at Cornell University in the United States, and was known as "public astronomer" and "public scientist". As a consultant of NASA, Sagan participated in the American space program and designed Mariner 1 to explore Venus with his colleagues. He played an important role in sending unmanned spacecraft into space and made many achievements in planetary science, the origin of life and the exploration of alien intelligence. During the Cold War, Sagan established a meteorological model to show that nuclear war on a global scale may lead to ecological imbalance of the earth, and put forward the hypothesis of "nuclear winter". Since 1970s, he began to host TV popular science programs and published a large number of popular science books. His TV series "The Universe" received a warm response all over the world, and the popular science work "The Garden of Eden Flying Dragon" won the Pulitzer Prize.