在加拿大
How Was the Solar System Formed? Scientists aren't completely sure how the solar system formed, but most agree the best explanation is that a cloud of molecules collapsed inward on itself, forming our solar system about 4.6 billion years ago. In this description, called the nebular model, our sun coalesced first, surrounded by a spinning disk of gas and dust. How the sun formedSome evidence, such as a 2010 study from scientists at the Carnegie institution, suggests this contraction could have been spurred by a burst from nearby supernovas. Other forces like differences in density could also have caused the cloud begin collapsing according to "From Suns to Life: A Chronological Approach to the History of Life on Earth" (Springer, 2004), an astronomy review text.Initially, gas collected in the dense center of this spinning disk, creating a protosun. Collisions between molecules heated things up, eventually raising temperatures to about ten million degrees Celsius. These increasingly hot and violent crashes sparked nuclear reactions, which turned the protosun into a star. This process took about 100,000 years, according to "From Suns to Life."How the planets formedMeanwhile, in the disk of material around the young sun, a process called accretion formed the planets, moons, comets and asteroids. Small particles crashed together to form larger and larger bodies, eventually reaching the size of planetesimals ― up to a few kilometers across. Massive enough to create their own gravity, these bodies drew even more collisions, with only the largest surviving the destructive crashes, according to the Lunar and Planetary Institute.In the hot area near the evolving Sun, water on the planetesimals tended to evaporate away, gasses were swept outward and only heavier material, like silicon and metals could condense into solids. Young planets in the inner solar system (like Earth) formed from this rocky, dense material.Farther away from the new star, cooler temperatures and abundant ice allowed for much larger bodies to form, creating the cores of planets such as Jupiter and Saturn. These cores were large enough for their gravity to pull in gas from the surrounding nebula, creating the gas giants of the outer solar system, according to the third edition of "The Solar System," an astronomical reference book.The other objects in the solar systemBeyond Neptune, in the even colder reaches of the disk, there was not enough material available for planetesimals to grow to gas giants. These stunted chunks make up the Kuiper belt.Between Mars and Jupiter, another field of planetesimals became the asteroid belt, which is thought to have been kept from clumping into a planet by the gravity of Jupiter, according to "The Solar System."The nebular model explains why all of the planets orbit in the plane of the Sun’s rotation ― that plane contains the remnants of that early gaseous disk.Telescopes have captured images of early moments in the formation of other solar systems throughout the universe, showing in live action what we believe took place around our own Sun.Gallery: The New Solar SystemWhat's at the Center of the Milky Way? How Do Scientists Know the Universe is Expanding?Got a question? Email it This e-mail address is being protected from spambots. You need JavaScript enabled to view it to Life's Little Mysteries and we'll try to answer it. Due to the volume of questions, we unfortunately can’t reply individually, but we will publish answers to the most intriguing questions, so check back soon.评论
回复: 太阳系怎样形成的?这个帖子比较费脑子，阳春白雪啊。
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回复: 太阳系怎样形成的?What's at the Center of the Milky Way? If you look up on a dark, clear night, away from city lights, you may see a wide band of faint light stretching above you, stiller than a cloud and glittering with densely packed stars. Translated from the Ancient Greek as "Milky Way" for resembling spilled milk on the sky, that band of light is the center of our galaxy.At its center, surrounded by 200-400 billion stars and undetectable to the human eye and by direct measurements, lies a supermassive black hole called Sagittarius A*, or Sgr A* for short.The Milky Way has the shape of a spiral and rotates around its center, with long curling arms surrounding a slightly bulging disk. It’s on one of these arms close to the center that the sun and Earth are located. Scientists estimate that the galactic center and Sgr A* are around 25,000 to 28,000 light years away from us. Ads by GoogleWe revolve around the center every 250 million years.While the supermassive black hole the largest type of black hole in a galaxy, with a mass millions of times that of our Sun can’t be imaged directly because black holes pull in all light, scientists have inferred its presence by looking at the speed and motion of stars and matter close to the galactic center. They have inferred that the movements are influenced by the gravitational pull of a black hole.No one knows how the black holes at the center of galaxies form, but some suspect the may begin as a cluster of smaller black holes that merge, or when a smaller black hole consumes enough matter become a supermassive one.How Do Scientists Know the Universe is Expanding?What Are Supernovas and What Do Scientists Learn from Them? What's at the Center of Black Holes?
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回复: 太阳系怎样形成的?这个帖子比较费脑子，阳春白雪啊。点击展开...已经是最简单的解释了.
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回复: 太阳系怎样形成的?
What's at the Center of Black Holes? Produced from the implosion of massive stars, black holes are wells in the fabric of space-time so deep that nothing, not even light, can escape them.At the center of a black hole is what physicists call the "singularity," or a point where extremely large amounts of matter are crushed into an infinitely small amount of space. Ads by Google"From a theoretical point of view, the singularity is something that becomes something infinitely large," said physicist Sabine Hossenfelder at the Nordic Institute for Theoretical Physics.Technically, that "something" is the curvature of space, or the heightened gravity that scientists have observed in the presence of very large masses like planets and stars.Similar to how a stretched rubber sheet dips around a bowling ball, massive objects can cause space-time to curve around them. And the more massive the object is, the steeper the curvature will be. First theorized by Einstein, nowhere is this effect more extreme than for a black hole, whose center represents an infinitely curving curve. Like a bottomless hole in a rubber sheet, the force becomes infinitely bigger as objects travel further and further into the hole.Around the singularity, particles and materials are compressed. As matter collapses into a black hole, its density becomes infinitely large because it must fit into a point that, according to equations, is so small that it has no dimensions.Some scientists have debated whether the theoretical equations that describe black holes are correct meaning whether they actually exist.No one can be sure that their singularity doesn't describe a physical reality, Hossfelder told Life's Little Mysteries. But most physicists would say that the singularity, as theorized by equations, doesn't really exist. If the singularity was "really real," then it would mean that "energy density was infinitely large at one point," exactly the center of the black hole, she said.However, no one can know for sure, because no complete quantum theory of gravity exists, and the insides of black holes are impossible to observe.How Big Is the International Space Station? What Will Replace the Hubble Space Telescope?How Do Astronauts Go To the Bathroom in Space?评论
回复: 太阳系怎样形成的?
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回复: 太阳系怎样形成的?Why should we know?
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回复: 太阳系怎样形成的?Why should we know?点击展开...you don't have to. Why should you be a huamn being?
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回复: 太阳系怎样形成的?还是对外星人更感兴趣
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回复: 太阳系怎样形成的?还是对外星人更感兴趣点击展开...Don’t talk to aliens, warns Stephen Hawking THE aliens are out there and Earth had better watch out, at least according to Stephen Hawking. He has suggested that extraterrestrials are almost certain to exist ― but that instead of seeking them out, humanity should be doing all it that can to avoid any contact.The suggestions come in a new documentary series in which Hawking, one of the world’s leading scientists, will set out his latest thinking on some of the universe’s greatest mysteries.Alien life, he will suggest, is almost certain to exist in many other parts of the universe: not just in planets, but perhaps in the centre of stars or even floating in interplanetary space.Hawking’s logic on aliens is, for him, unusually simple. The universe, he points out, has 100 billion galaxies, each containing hundreds of millions of stars. In such a big place, Earth is unlikely to be the only planet where life has evolved.Times ArchiveNew light on black holes, 1976Exploding black holes, 1977Related LinksOops, that was a bad call, EarthHello... Are we alone in the Universe?“To my mathematical brain, the numbers alone make thinking about aliens perfectly rational,” he said. “The real challenge is to work out what aliens might actually be like.”The answer, he suggests, is that most of it will be the equivalent of microbes or simple animals ― the sort of life that has dominated Earth for most of its history.One scene in his documentary for the Discovery Channel shows herds of two-legged herbivores browsing on an alien cliff-face where they are picked off by flying, yellow lizard-like predators. Another shows glowing fluorescent aquatic animals forming vast shoals in the oceans thought to underlie the thick ice coating Europa, one of the moons of Jupiter.Such scenes are speculative, but Hawking uses them to lead on to a serious point: that a few life forms could be intelligent and pose a threat. Hawking believes that contact with such a species could be devastating for humanity.He suggests that aliens might simply raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”He concludes that trying to make contact with alien races is “a little too risky”. He said: “If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”The completion of the documentary marks a triumph for Hawking, now 68, who is paralysed by motor neurone disease and has very limited powers of communication. The project took him and his producers three years, during which he insisted on rewriting large chunks of the script and checking the filming.John Smithson, executive producer for Discovery, said: “He wanted to make a programme that was entertaining for a general audience as well as scientific and that’s a tough job, given the complexity of the ideas involved.”Hawking has suggested the possibility of alien life before but his views have been clarified by a series of scientific breakthroughs, such as the discovery, since 1995, of more than 450 planets orbiting distant stars, showing that planets are a common phenomenon.So far, all the new planets found have been far larger than Earth, but only because the telescopes used to detect them are not sensitive enough to detect Earth-sized bodies at such distances.Another breakthrough is the discovery that life on Earth has proven able to colonise its most extreme environments. If life can survive and evolve there, scientists reason, then perhaps nowhere is out of bounds.Hawking’s belief in aliens places him in good scientific company. In his recent Wonders of the Solar System BBC series, Professor Brian Cox backed the idea, too, suggesting Mars, Europa and Titan, a moon of Saturn, as likely places to look.Similarly, Lord Rees, the astronomer royal, warned in a lecture earlier this year that aliens might prove to be beyond human understanding.“I suspect there could be life and intelligence out there in forms we can’t conceive,” he said. “Just as a chimpanzee can’t understand quantum theory, it could be there are aspects of reality that are beyond the capacity of our brains.”Stephen Hawking's Universe begins on the Discovery Channel on Sunday May 9 at 9pm
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回复: 太阳系怎样形成的?you don't have to. Why should you be a huamn being?点击展开...Why should you be a human being? With great interest to have a piece of your answer.
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回复: 太阳系怎样形成的?Why should you be a human being? With great interest to have a piece of your answer.点击展开...But I don't have any interest in getting to know someone like you. Go away!
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回复: 太阳系怎样形成的?How Do Scientists Know the Universe is Expanding? By Corey Binns 18 March 2010 8:53 AM ET We thought we’d ask Geza Gyuk, Director of Astronomy at the Adler Planetarium and a research scientist at the University of Chicago. Here's what he said:A few years after Albert Einstein had developed his famous (and by now very well tested!) theory of General Relativity (GR) in 1915 he applied it to the entire universe and found something remarkable. The theory predicts that the whole universe is either expanding or contracting. There really isn't any other alternative. To have the universe staying static is like a pencil balanced on its point... possible, but very, very unlikely and not liable to last for very long.In 1929 the astronomer Edwin Hubble measured the velocities of a large selection of galaxies. He expected that about equal numbers would be moving toward and away from us. After all, the Earth isn't a particularly special place in the universe. Instead, he discovered that almost all galaxies are moving away from us!Since the time of Hubble we have observed millions of galaxies with better equipment and verified his results. With the exception of a small handful of galaxies close to us, every galaxy is moving away from us.And in fact, the farther away a galaxy is the faster it is moving away from us. This fits in very well with Einstein's predictions. The galaxies seem to be receding from us because the entire universe is getting larger. The space in between the galaxies is stretching! And the farther away a galaxy is the more space there is to stretch so the faster the galaxy appears to move away from us.Over the past half-century astronomers have observed many other facts about the universe that all point to the fact that the universe is expanding. While a very inventive person might be able to explain away one or at most two of these discoveries, the expansion of the universe is the only theory that can explain all of them at once. And with each passing year the evidence piles up higher!Does the Universe Have an Edge?The Greatest Mysteries in ScienceIs There Gravity in Space?
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回复: 太阳系怎样形成的?我这个有兴趣的但英文不好的人看得极慢。谢谢科普了。
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回复: 太阳系怎样形成的?这事准确的答案得问CREATOR
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回复: 太阳系怎样形成的?this is much simpler.[ame]http://www.no video.com/watch?v=tFLOsRSuW0E[/ame]
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回复: 太阳系怎样形成的?好像science9,10年级的书上有。
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The only thing necessary for the triumph of evil is for good men to do nothing. 不要去欺骗别人，因为你能骗到的人，都是相信你的人。回复: 太阳系怎样形成的?有机会在网上查查“太阳系皮壳”吧。其实我们太阳系是一个被制造和隔离的“培养皿”宇宙就是为我们放映的一部电影。这个是上世纪那个比爱迪生还杰出的科学家提出的。那个科学家的名字我一时想不起来，但是看看他的发明大家就能知道：交流电，电报，X光透视，火箭助推器，。。。当人类的深空探测器飞离木星地带后，探测器上的摄像头看到的只是一片漆黑。
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太初有道，道与神同在，道就是神。天行健，君子以自强不息。谷神不死，是谓玄牝。玄牝之门，是谓天地根，绵绵若存，用之不勤。个人建议华人应该在加拿大积极参政，可以有效地保护华人的权益。有机会在网上查查“太阳系皮壳”吧。其实我们太阳系是一个被制造和隔离的“培养皿”宇宙就是为我们放映的一部电影。这个是上世纪那个比爱迪生还杰出的科学家提出的。那个科学家的名字我一时想不起来，但是看看他的发明大家就能知道：交流电，电报，X光透视，火箭助推器，。。。当人类的深空探测器飞离木星地带后，探测器上的摄像头看到的只是一片漆黑。点击展开...太不可思议了。
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回复: 太阳系怎样形成的?如果有情绪问题的话，看了这样的话题，就豁然开朗了。认识一个患有恐惧症的人，病假期间偶尔看到了这类书籍，竟然再没有复发过。
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