By Yin Nwe Ko
BILLIONS of years ago, an object the size of Mars smashed into the Earth. The resulting debris jetted into orbit, leaving us with a moon — or maybe two.
Those two above sentences made me confused about our planet. People who are moving about on the planet always think of everything in their self-centred instincts. Thus, greed, anger, and hatred have been appearing for ages nonstop on earth. Consequently, wars and battles have never been stopping up to now. Have you heard about the wars and the battles in the animal kingdom? In reality, man is a kind of animal as he is also included in the animal kingdom. Only due to the ability to speak one another with different languages, man has got a great chance that can overwhelm all other animals. A man usually thinks he is the greatest, the most powerful, and the most incomparable among animals or other people like him. His thought which he thinks quite right might be a little true on the earth’s surface surrounding him.
However, if he flies up into the high sky and looks back onto the surface he stood on earlier, he will see the people like sesame seeds and the buildings like tiny stones. This is not in the space yet. If he flies up into space, he will see his native earth as a small ball. At that moment, should he think his greed, anger, ignorance, and pride which have flamed his mind on the earth, all will be completely gone away from him? It is sure. It is a man who is just the tiniest particle compared with the universe. When we find the truth of nature, we will realize that every greed, anger, ignorance, and pride becomes nothing at all. The following article written by Mike Brown who is a professor of Planetary Astronomy at Caltech will highlight our solar system and then the one who has read it will certainly contemplate his current life and “Kilesa” meaning passion and defilement.
If you visited the surface of the Earth 4.5 billion years ago, you would not recognize it. The newly formed planet was still cooling from its recent coagulation. There was a hot rocky surface that we do not probably know for sure, volcanoes, and a steamy atmosphere (maybe). It seems unlikely that even the smallest thing resembling life was yet present, though we do not know. What we do know is what came next. On the most extraordinary day in the history of our planet, a Mars-sized body crashed into the Earth.
Over the course of a few hours, this mini planet ploughed deep into the Earth’s interior, sending shock waves throughout the globe and eventually melting all the rocks on its surface. A massive spray of material was blasted into deep space before it was slowed by gravity and captured into orbit. The Earth was left covered in an ocean of liquid magma hundreds of miles deep, while the mixed remnants of the Earth and the original Marssized body circled high above in a glowing ring of molten rock. We can be forgiven for not knowing what the surface of the Earth was like before this moment, as nothing survived that day intact.
A thousand years after that eventful day, the glowing ring of superheated rocks in orbit above had coagulated, and the Earth finally had the moon. Or maybe, according to a scientific hypothesis pioneered in part by Erik Asphaug, a planetary scientist at the University of Arizona, it had two moons. Mr Asphaug explains that notion in “When the Earth Had Two Moons,” but, as he shows, to understand even one moon, one has to understand how the whole solar system came to be assembled. The story swings from the birth of the universe, through the history of astronomy, to the modern understanding of the piece-by-piece building of the planets. There are delightful sidetracks into feasting monks, desert meditations, and how a tech billionaire could (and should) launch an exploration of Saturn’s hydrocarbon-rich moon Titan.
Early on, Mr Asphaug poses a simple question that, even to a person like me who has been thinking and studying planets for 30 years, should give pause: Why are all of the planets so different? Mercury is tiny with a huge iron core. Venus and Earth are similar in size, but Venus is a dead, dry planet with an atmosphere dense enough to crush spacecraft. Mars is small and lopsided. Jupiter is massive, Saturn has rings, Uranus is oddly tilted on its side and Neptune is missing the types of moons that all of the other giants have. Why? The interstellar cloud of gas and ice and dust that eventually formed the sun and planets probably varied smoothly from one region to the next, so why would the planets that came out of it vary so wildly?
Mr Asphaug has a plausible solution: catastrophic collisions. Planets are assembled bit by bit, with the largest pieces coagulating together last. The collision that led to the moon — catastrophic — was the last major part of the coagulation of the Earth. If the Mars-sized body that hit the Earth had hit it slightly differently — more head-on or at a higher speed, for example — we probably wouldn’t have the moon. With the tilt of the Earth no longer stabilized by the moon, we could have the types of extreme climate variations that we see on Mars, where glaciers periodically cover the equator. Without the moon, there would be no tides, which — maybe? — were crucial in the evolution of life. If that singular day 4.5 billion years ago had never happened, the Earth would be a very different planet.
The other planets have their own one-off stories. Mercury probably had a near-catastrophic impact that tore away most of its rocky exterior; Mars was nearly destroyed by an impact that left it with a massive northern basin that could have once been filled with a temperate ocean; Saturn’s rings and small moons could be the remnants of multiple colliding moons; Uranus was perhaps bashed by something huge that knocked it on its side, and Neptune’s moon Triton was captured from the outer solar system and disrupted or ate all of Neptune’s original moons as it came in. Even the non-planets get in on the act. The distinctive “heart” on the face of Pluto is a giant basin that formed a massive impact that then slowly filled with glaciers made out of frozen nitrogen gas.
Mr Asphaug’s account sometimes requires a bit of background knowledge, but his writing is peppered with playful images (one possible collision was like “mashing your fist into a cherry pie”). He is at his most charming when he is not just telling how scientists currently think about the chaotic formation of the solar system but relaying his part in the story, as with the idea of that second moon. He perfectly captures the way that so many scientific insights occur: while sitting listening to something else and having your mind wander. Mr Asphaug tells the story of daydreaming a second moon into existence during a talk on the peculiarly thick crust on the moon’s far side. Daydreaming turns to speculative computer simulation, which excitedly turns into a detailed simulation, which satisfyingly turns into a substantial hypothesis: Perhaps a small second moon was created at the same time as our moon, and that small moon eventually gently collided with the main one, making, essentially a mound on the far side.
Is the story true? Possibly. Like any good hypothesis, it explains something that was previously unexplainable. Just as important: It makes predictions that can be tested. Future lunar geologists and seismologists could eventually find traces of the little moon that once was.
Mr Asphaug’s thesis that random catastrophic impacts explain the astounding diversity of our planetary system is humbling to a planetary astronomer like me. We are always trying to understand why the planets and other bodies in the solar system have the specific characteristics they do. It is initially depressing to think that the answer to many of our questions is simply dumb luck. But I think that embracing the chaos around us, as Mr Asphaug does, ultimately makes the solar system an even weirder and more wonderful place than it seemed before.
Here, the article is ended up and those who are impressing themselves as the greatest, the most powerful and the most incomparable ones will be enough to realize how they are the tiniest particles in the universe. I am also going to stop my long article with a sentence. Everything is impermanent.
Reference: A smashing solar system
(Wall Street Journal; January 2020)
