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Fermi Paradox
When ordinary people ask, where are the aliens? We usually just laugh it off and take it as a joke. However, when this sentence is uttered from the mouth of a scientific authority, it becomes a question that is terribly thoughtful. The sun is a relatively young star, which means that there are terrestrial planets that are much older than the earth. In theory, their civilization should be far more developed than ours. Earth is 4.54 billion years old. Assuming we compare with a planet P which is 10 billion years old. If P’s experience is similar to that of Earth, their civilization should be 5.46 billion years ahead of us. Their technology will be beyond our comparison. This gap is like the monkey seeing human civilization. So why haven’t we discovered alien civilization so far?
One explanation for the Fermi Paradox is that alien civilizations tend to self-destruct before making contact with other civilizations (such as Earth). e.g. climate change, nuclear war
Another explanation is that intelligent civilizations are rare, either because the conditions necessary for the evolution of intelligent life are scarce, such as humans needing oxygen to live.
Or the alien civilization has received the signal sent by the earth, but they may not reply to us for some reason.
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Drake Equation
I have been thinking about whether there are civilizations other than Earth civilization in the galaxy. All the while, I saw a lot of articles about alien civilizations, but I never fully believed them. Although the Milky Way is very large, we have never found traces of alien civilization in the current exploration of human beings. But through the Drake equation, I almost completely believe in the existence of extraterrestrial civilizations. The Drake equation calculates the number of extraterrestrial civilizations from a full range of perspectives. Even though we don’t know the exact values of the variables in the Drake equation, but through estimation, I found that we do have a probability of discovering alien civilizations. I believe that in the future we will have more precise answers.
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Neptune
In the outermost layer of the solar system, there is a sapphire-like planet walking quietly. It is Neptune, the fourth largest and third most massive planet in the solar system. It is blue because its atmosphere is made up of hydrogen and helium, as well as methane. Well, it didn’t actually walk quietly. Neptune’s wind is the largest in the solar system (wind speed can reach 2100km/h). These factors contribute to Neptune’s atmosphere being one of the coldest places in the solar system.
With the basic information out of the way, let’s talk about what’s going to happen in the future. What concerns me the most is Neptune retrograde. At the end of June this year, Neptune will be retrograde (we’ve seen this before). Neptune’s retrograde motion will last for half a year. Another thing is that from mid-September onwards, the Moon will block Neptune. But that doesn’t mean we can’t see Neptune retrograde, or that we can see the Moon occult Neptune. In fact, we can see Neptune retrograde almost anywhere on Earth, but we can only see lunar occultations of Neptune from Antarctica.
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Pluto
Pluto is a particularly interesting dwarf planet, which is located in the Kuiper Belt. When humans first discovered Pluto, it was identified as the ninth planet in the solar system. Until 2006, Pluto was considered a dwarf planet because of its small size and the abundance of other debris in its orbit. Pluto has a highly elliptical orbit, and it takes 248 years to complete one orbit.
There are many interesting things about Pluto. About the naming of Pluto. It comes from the name of the Roman god of the underworld, which also honors Percival Lowell. When it comes to Percival Lowell, we have to talk about Planet X. This is a hypothesis that existed from the 19th century to the beginning of the 20th century. It is believed that there is a planet outside Neptune that affects the orbits of Neptune and Uranus, which was proposed by Percival Lowell. Pluto was thought to be Planet X at the time, but later measurements revealed that Pluto’s mass was far from enough to affect the orbits of Neptune and Uranus. In the end, Ernest Brown concluded that the discovery of Pluto might just be an accident.
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Meteors
Meteors are common celestial bodies. There are a lot of fine dust and some fine solid matter in the solar system, which we call meteoroids. Despite their relatively small size, they also orbit the Sun. If they break into the atmosphere and have violent friction and collisions with the atmosphere, they will burn and emit dazzling light. These meteoroids burn up as they fly high and are what we see as meteors.
Meteors generally appear at an altitude of about 80-120 kilometers from the ground. Usually, meteoroids are evenly distributed around the Earth. If the Earth didn’t rotate and revolve, then there should be an equal number of meteors coming in from all directions. As the Earth orbits the sun, the number of meteors seen at different times varies. -
The Formation of the Solar System
So far, there are several hypotheses about the formation of the earth and the solar system. There are two main popular hypotheses: one believes that the solar system was produced by a violent accidental mutation, the catastrophe theory; the other believes that the solar system evolved gradually in an orderly manner, that is, evolutionary theory.
In 1755, the German philosopher Kant proposed the hypothesis of the formation of the solar system based on Newton’s principle of universal gravitation. He believed that the sun, planets, and moons in the solar system formed gradually from nebulae—thin clouds of granular matter. In 1796, French astronomer Laplace also proposed a nebula theory similar to Kant’s. Later generations often combine the two together, collectively referred to as “Kant-Laplace nebula theory”. This assumption dominated most of the 19th century.
Scientists believe that stars form as spherical fragments of a primordial nebula that runs through the Milky Way. Under the action of its own gravity, it constantly shrinks and creates a vortex. The vortex shattered the nebula into a multitude of fragments, each of which gradually transformed into a star. The sun is one of them, and it is also constantly shrinking and rotating, forming the original sun in long-term motion. The surrounding objects continue to gather, collide, and become larger and larger, forming today’s eight planets. The material around the planets also gradually formed moons in this way. This is one of the leading hypotheses for the formation of the solar system. -
Retrograde motion
Retrograde motion is one of the apparent motions of planets relative to the background of the stars. If we continue to track a certain planet for a period of time, we will find that it sometimes moves to the east, sometimes stops for a short time, sometimes moves to the west, then makes a short stay, and then moves to the east as it did at the beginning. In order to explain this phenomenon, the epicycle-deferent model was born. This geocentric model dominated for two thousand years until Kepler’s three laws were proposed.
So, what causes the retrograde motion of the planets? Actually, they are not really retrograde. The earth is closer to the sun than many planets, so the earth moves faster. Whenever Earth overtakes a planet, the outer planets appear to start receding in the sky. From Earth, Mercury and Venus appear to oscillate on either side of the Sun. These planets all do circular motion around the sun, it’s just that here on Earth, it looks like the planets are going backwards.
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Historical Astronomers in Context
Johannes Kepler（12/27/1571 – 11/15/1630）
In 1609, Kepler published the first two laws of planetary motion: the orbit of planetary motion is ellipse; in equal time, the areas swept by the line connecting the sun and the moving planets are equal. In In 1619, he produced his third law, which says that the square of the circular motion period of each planet around the sun and the cube of the semi-major axis of its elliptical orbit are proportional.
I think this event is very interesting. Kepler is one of my favorite astronomers. Among the many hits, I especially like Kepler’s universe model. The most amazing thing about Kepler’s universe model is that he uses mathematics to explain the observed universe. While previous astronomers had limited themselves to recording the observed positions of planets, Kepler went further and sought mathematical models that could explain the observed phenomena. This is a very important process of the scientific method. Of course, we all know today that this model is wrong. There are not only six planets, but the orbital distances obtained are only approximate.
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Moon phases
Image from NASA Science The image above shows the position of the Moon, the Sun, and the Earth during each phase. The whole process( the Moon orbiting the Earth) takes about 29.5 days; and this time period makes Moon Phases.
The cause of Moon Phases is the Moon’s orbiting motion and the sunlight. Like Earth, half of the Moon would be illuminated by the Sun and the other half remains dark. The rotation of the Moon will change the dark side and bright side. And because of the Moon’s orbiting motion, the illuminated part that is exposed to us will change. As the position of the moon relative to the earth and the sun changes, the side illuminated by the sun sometimes faces the earth, and sometimes faces away from the earth; sometimes the bright side facing the earth is larger and sometimes smaller, thus appearing different moon phases which shown above.
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visiting wild animal safari park
The photo was taken at Atlanta Wild Animal Safari on Oct 15, 2022 by myself. It was a picture of ostrich and was my first time see a ostrich.
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