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How may planets are there in the solar system revolving around the sun？
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更多“How may planets are there in t…”相关的问题
The trouble starts when we come to estimate the probability that life will emerge on any of these planets. The problem is that we don' t have a good theory of the origin of life on earth. Without one, it is anybody' s guess how likely this event actually was. Out of thin air Aczel conjures (想像) the figure of 1 in a trillion for this likelihood and concludes that the probability of life existing on at least one other planet is virtually 1.
Statistics are extremely powerful and important, and Aczel is a very clear and capable exponent (倡导者) of them. But statistics cannot substitute for empirical (经验主义的) knowledge about the way the universe behaves. We now have no reasonable way of arriving at robust estimates for the probability of life arising spontaneously when the conditions are right. So, until we either discover extraterrestrial (外星球的) life or understand far more about how at least one form. of life--terrestrial life--first appeared, we can do little more than guess at the likely hood that life exists elsewhere in the universe. And as long as we' re merely guessing, we should not dress up our interesting speculations as mathematical certainties.
The term "Out of thin air" in Line 3 of Paragraph 2 can be best replaced by ______.
A．convincingly
B．confidently
C．groundlessly
D．suitably
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere, a larger one would hold too much of it.
Life also required a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life？ First, eliminate those stars that are not like our sun. Next, eliminate most of their planets, they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
Astronomers believe that matter in different parts of the universe ______.
A．has different laws
B．has one common law
C．shares the same laws
D．shares no common law
Compared with their cosmologist(宇宙学家) colleagues, cosmogonists(星源学家) can sound a little old-fashioned. Edgar Allen Poe turned to the mysteries of cosmogony in an 1848 public lecture, just reprinted by Hesperus Press. And we encountered a reference to cosmogonists most recently in a new edition of Poe's prose poem Eureka.
What's the difference between cosmologists and cosmogonists？ Just two letters and a few billion light years. Cosmologists worry about where the Universe came from, cosmogonists with how the Solar System formed. The interesting thing is that one-and-a-half centuries after Poe, they still can't reach agreement on what happened in the nearest 5 light years of space.
What's the problem？ It turns out that there are a couple of competing explanations for why our neighbourhood is the shape it is, as well as several bizarre anomalies in the data. Cosmogonists know that the Solar System is essentially flat. With the exception of two tiny outliers, Mercury and Pluto, the orbits of all the other planets lie in very nearly the same plane. And most cosmogonists agree that this is because the planets themselves formed from a nebular(星云状的)disc orbiting the early Sun, which had itself coalesced out of the same cloud of gas and dust.
But there's a catch. If the planets and the Sun came from the same nebular disc, then the Sun's equator should lie in the planetary plane. It doesn't. The Sun leans over at an angle of 7.25° The majority of cosmogonists insist that the angle is so close to zero that it really doesn't matter. Anyway, they add, the Sun has been losing mass for most of its life, and may have slipped a little.
The remaining minority aren't having this. How can 7.25° be the same as zero？ The Sun and the planets did come from cosmic dust, they say, but not from the same cloud of material. The Sun took shape somewhere in the Galaxy. Then it sailed along and picked up the planets—or perhaps the gas and dust that gave birth to them—elsewhere.
Is a tilting Sun the cosmogonists' only headache？ Not at all. It's also hard to agree on how the outer planets formed. Far out in the nebular disc, matter would have been so spread out that it couldn't quickly have dumped together. Some suggest planet-sized gravitational instabilities, others can find no reason for Uranus and Neptune to have formed yet.
The closer you get to home, it seems, the deeper the mysteries.
What is the best title for the passage？
A．Difference Between Cosmologist and Cosmogonist.
B．Where the Universe Came From.
C．How the Solar System Formed.
D．The Titling Sun.
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.
Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life？ First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
第36题：Astronomers believe that matter in different parts of the universe
A) has different laws.
B) has one common law.
C) shares the same laws
D) shares no common law.
根据短文回答 36～40 题。
Life in the Universe
Many scientists today are convinced that life exists elsewhere in the universe － life probably much like that on our own planet. They reason in the folio, wing way.
As far as astronomers (天文学家) can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This .eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.
Life also requires a steady supply of heat and light. This eliminates double stars, or tars that flare up (闪耀) suddenly. Only single stab that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life？ First, eliminate those stars that are not like our sun. Next, eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
第 36 题 Astronomers believe that matter in different parts of the universe（）
A．obeys different laws
B．obeys one common law
C．obeys the same laws
D．obeys no common law
请根据短文内容，回答题。
So Many "Earths"
The Milky Way (银河) contains billions of Earth-sized planets that could support life. That&39;s the finding of a new study. It draws on data that came from NASA&39;s top planet-hunting telescope.＜br＞
A mechanical failure recently put that Kepter space telescope out of service..Kepler had played a big role in creating a census of planets orbiting some 170,000 stars. Its date have been helping astronomers predict how common planets are in our galaxy. The telescope focused on hunting planets that might have conditions similar to those on Earth.＜br＞
The authors of a study published in The Proceedings of the National Academy of Sciences conclude that between 14 and 30 out of every 100 stars with a mass and temperature similar to the Sun may host a planet that could support life as we know it. Such a planet would have a diameter at least as large as Earth&39;s but no more than twice that big. The planet also would have to orbit in a star&39;s habitable zone. That&39;s where the surface temperature would allow any water to exist as liquid.＜br＞
The new estimate of how many planets might fit these conditions comes from studying more that 42,000 stars and identifying suitable worlds orbiting them. The scientists used those numbers to extrapolate (推算) to the rest of the stars that the telescope could not see.＜br＞
The estimate is rough, the authors admit. If applied to the solar system, it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars. Neither planet is Earthlike (although either might have been in the distant past). Using tighter limits, the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world. These are ones that would take 200 to 400 days to complete a yearly orbit.＜br＞
Four out of every 100 sunlike stars doesn&39;t sound like a big number. It would mean, however, that the Milky Way could host more than a billion Earth-sized planets with a chance for life
The Kepler space telescope has been in service for 15 years. 查看材料
A.Right
B.Wrong
C.Not mentioned
A．Y
B．N
C．NG
The searchers used NOT to believe______.
A．other stars may have the planets resembling those going around the sun
B．planet forms owing to the gas and dust in star formation
C．the formation of star is subsequent to that of planet
D．star is formed by the collapsing interstellar cloud
How many planets orbiting other stars have the two scientists discovered so far？
A．100.
B．69.
C．66.
D．65.
Life on Other Planets
In 1961, scientists set up a gigantic, sensitive apparatus to collect radio waves from the far roaches of space, hoping to discover in them some mathematical pattern indicating that the waves were sent out by other intelligent beings. The first at tempt failed; but someday the experiment may succeed.
But is there intelligent life？ Life that has reached the stage of being able to send radio waves out-into space in a planned pattern？ Our own planet may have been in existence for five billion years and may have had life on it for two billion, but it is only in the last fifty years that intelligent life capable of sending radio waves into space has lived on earth. From this it might seem that even if there were no technical problems involved, the chance of receiving signals from any particular earth-type planet would be extremely small.
This does not mean that intelligent life at our level does not exist somewhere. There is such an unimaginable number of stars that, even with only a small chance, it seems certain that there are millions of intelligent life forms scattered through space. The only trouble is, none may be within hailing distance of us. Perhaps none ever will be; perhaps the huge distances that separate us from our fellow inhabitants of this universe will forever remain too great to be conquered. And yet it is conceivable that someday we may come across one of them or, frighteningly, one of them may come across us. What would they be bike, these extraterrestrial creatures？
Surely, it would seem, there is no way of telling. Here on earth alone, life has developed in many directions, taking on forms that could scarcely be invented by the wildest imagination if they were not already known to exist.
Who would dream that a mouse could fly if he had never seen a bat？ Who would predict blind lizards living in caves, or worms living in the intestines of other creatures？ Consider the giraffe, the humming-bird, the redwood tree, the Venus' flytrap, and see whether you can imagine any limit to various forms of life. Then how can anyone predict anything at all a bout extraterrestrial beings？
Ah, but all these variations and modifications that exist on earth are in some ways only superficial. In the chemist's test tube, all amazing differences in life forms vanish when we consider the basic similarity of those life forms, which is neither exciting nor amazing. Whatever appearance earth creatures may have, they are all made up of the same kinds of complex molecules; with minor variations, they all make use of the same chemical machinery.
For all its wonderful differences, life on earth is merely an imaginative variation on a single chemical structure. Life on any earthlike planet may prove to be similar.
As we understand life, it consists of molecules large enough and complex enough to meet the infinitely flexible requirements of living tissue. The molecules must be stable enough to retain their structure under some conditions, and unstable enough to change kaleidoscopically under other conditions. In living things on earth, the most important molecules of this type are the proteins, and as far as we know, nothing will substitute for them.
Furthermore, the changes these proteins undergo in the process of living can only take place against a watery back ground. Life began in the oceans, and even the various forms of land life are still from 50 to 80 percent water.
The chemical structure, then, upon which life is based, here and possibly on all earth-type planets, is protein-in water. If we are ever to meet up with creatures from an earth-type planet, we may not be able to predict their appearance, but we can predict that, whatever their shape, they will very likely be protein-in-water.
But what about life on planets that are not like the earth？ Wh
A．Y
B．N
C．NG
