Sending messages into deep space could be the best way for Earthlings to find extraterrestrial (地球以外的) intelligence, but it carries a risk: alerting unfriendly aliens to our presence. Game theory may provide a way to deal with this situation.
So far the search for extraterrestrial intelligence (SETI) has mostly been restricted to listening for signs of technology elsewhere. Only a few attempts have been made to broadcast messages towards distant starts. Many scientists are against such “active” SETI for fear of revealing our presence. If all aliens feel the same way then no one will be broadcasting, and the chance of detecting each other is limited.
To weigh up the potential losses and gains, Harold de Vladar of the Institute of Science and Technology Austria in Klosterneuburg turned to the prisoner’s dilemma, a game-theory problem in which two prisoners choose between admitting their shared crime or keeping quiet, with different sentences depending on what they say. An individual prisoner gets off scot free if he betrays (出卖) a partner who remains silent, with the silent partner getting a maximum sentence. If they both betray each other, each gets a medium sentence. By contrast, if both stay silent, both get minimum sentences---the best overall result.
De Vladar reasoned that the SETI dilemma is essentially the same, but reversed. Mutual betrayal for prisoners is equivalent to mutual silence for aliens. And while a selfish prisoner stops keeping silent, a selfish civilization is silent, waiting for someone else to take the risk of waving “Over here!” at the rest of the universe.
This led de Vladar to apply the mathematics of the prisoner’s dilemma to SETI. In the classic version of the prisoner’s dilemma, each selfishly betrays the other. But as we do not know the character of any aliens out there, and as it is difficult to put a value on the benefits to science, culture and technology of finding an advanced civilization, de Vladar varied the reward of finding aliens and the cost of unfriendly aliens finding us. The result was a range of best broadcasting strategies. “It’s not about whether to do it or not, but how often,” says Vladar.
One interesting idea was that as you increase the rewards placed on finding aliens, you can decrease the frequency of broadcasts, while keeping the expected benefit to Earthlings the same. Being able to keep broadcasts to a minimum is good news, because they come with costs--- equipping our planet with transmitters won’t come cheap---and risk terrible disasters, such as interstellar (星际的) wars.
1. According to the passage, which of the following can be classified as “passive” SETI?| A．Concealing our presence from aliens. | B．Listening for signs of technology elsewhere. |
| C．Broadcasting to distant stars. | D．Detecting the existence of aliens. |
| A．both civilizations sending messages | B．people on the earth sending messages |
| C．both civilizations keeping silent | D．people on the earth keeping silent |
| A．Equipping the earth with the most advanced transmitters. |
| B．Preparing for the disasters such as interstellar wars. |
| C．Sending to space as few messages as possible. |
| D．Decreasing the rewards for finding aliens. |
| A．Earthlings are likely to be attacked by extraterrestrial intelligence. |
| B．Scientists are looking for better approaches to finding aliens. |
| C．Earthlings should be more active in broadcasting to aliens. |
| D．Decision to contact aliens is a game-theory dilemma. |
相似题推荐
【推荐1】Revealing the source of Jupiter’s x-ray auroral flares
Abstract
Jupiter’s rapidly rotating, strong magnetic field provides a natural laboratory that is key to understanding the dynamics (动力学) of high-energy plasmas (等离子体). Spectacular auroral (极光的) X-ray flares (耀斑) are diagnostic of the most energetic processes governing magnetospheres but seemingly unique to Jupiter. Since their discovery 40 years ago, the processes that produce Jupiter’s X-ray flares have remained unknown. Here, we report simultaneous (同时的) in situ satellite and space-based telescope observations that reveal the processes that produce Jupiter’s X-ray flares, showing surprising similarities to terrestrial ion aurora. Planetary-scale electromagnetic waves are observed to modulate (调节) electromagnetic ion cyclotron waves, periodically causing heavy ions to precipitate and produce Jupiter’s X-ray pulses. Our findings show that ion aurorae share common mechanisms across planetary systems, despite temporal, spatial, and energetic scales varying by orders of magnitude.
INTRODUCTION
Aurorae, observed from planetary polar regions across the solar system, are displays of light that are produced when energetic particles precipitate along magnetic field lines and transfer their energy to the atmosphere. Jupiter’s soft x-ray aurorae are produced by energetic [~ (MeV) (电子伏)] heavy ions (S and O), originally from the moon Io’s (木卫一的) volcanic activities. The dynamic X-ray emissions often pulse with a regular beat of a few tens of minutes. The spectacular quasi-periodic (准周期性的) auroral pulsations at Jupiter have also been observed in ultraviolet (UV), infrared, and radio emissions. The X-ray aurorae are predominately confined (主要局限于) to the region poleward of Jupiter’s main aurora, connecting to Jupiter’s outer magnetosphere via magnetic field lines. The mapping of the emissions leads to the suggestion that the particle precipitations were driven by magnetic reconnection. However, observations show that the x-ray pulsations last for several Jupiter days or longer, evidencing that the driver may not be a transient process like magnetic reconnection.
To date, 40 years after their discovery, the mechanisms that cause these X-ray aurorae remain unknown. Simultaneous measurements of the magnetospheric environment and the auroral emissions are critical to revealing their driving mechanisms. Here, we present observations of Jupiter’s unique x-ray aurorae with simultaneous in situ measurements from the magnetosphere. In this study, we reveal the physical driver for Jupiter’s pulsating x-ray emissions by analyzing simultaneous in situ measurements from Juno and remote spectroscopic imaging by XMM-Newton telescope (XMM，牛顿卫星) during 16 and 17 July 2017. XMM’s European Photon Imaging Camera (EPIC-pn and MOS) instruments provided spatial, spectral, and timing data of Jupiter for a continuous 26-hour (~2.6 Jupiter rotations) observation from 18:26 UT on 16 July to 22:13 UT on 17 July, which was shifted to account for the ~46-min light travel time between Jupiter and Earth. This XMM observation was planned to coincide with the time when NASA’s Juno spacecraft was moving from 62 to 68 RJ (1 RJ = 71 492 km) radially away from the planet in the Southern Hemisphere in the predawn sector between ~0400 and 0430 magnetospheric local time (MLT).
Ionosphere-magnetosphere (电离层) mapping from previous observations suggested that the origins of Jupiter’s X-ray auroral pulsations occurred at these distances from the planet. Juno provided contemporaneous (同时发生的) in situ measurements from the plasma sheet only when Jupiter’s north magnetic pole tilted to Earth. Therefore, we focus on the northern aurora, for which Juno’s in situ measurements detail what was happening in the plasma sheet during the X-ray pulses. At Jupiter, the analysis of these comparisons between in situ and remote sensing observations is more complex than at Earth. At Earth, during the time scale of an auroral event, typically tens of minutes, a spacecraft in the terrestrial magnetosphere usually travels little (e.g., hundreds of kilometers) in comparison to the spatial scale of a magnetospheric event (e.g., several Earth radii) that would cause a large auroral brightening so that this in situ spacecraft could be magnetically connected to the aurora region over the full auroral lifetime. This is not true for Jupiter, because the footprint of the aurora (which is rotating with Jupiter) with respect to Juno’s location changes substantially during an observation. There are also substantial travel times (a few tens of minutes) along the magnetic field expected from the outer magnetosphere to the Jovian aurora. Therefore, the correlation between a single outer magnetosphere event in Jupiter’s in situ measurements and a single auroral pulse cannot be expected on a one-to-one level basis. Instead, a series of successive events are required to draw reliable careful correlations, with the regular periodicity of the x-ray flares, providing an invaluable diagnostic signature of the source process.
(Adapted from an essay on Science.)
1. What does the essay focus on?| A．The X-ray pulses happening on Jupiter. |
| B．The formation of the aurora in the pole of Jupiter. |
| C．The ways to teach people how to appreciate auroras. |
| D．The process of detecting the X-ray pulses on Jupiter. |
| A．Their conclusions. | B．Their measure to do the research. |
| C．Discussion of some problems of preciseness. | D．Their acknowledgements. |
| A．辐射 | B．红外线技术的 | C．太阳风 | D．红外线 |
| A．The strong magnetic is a good breakthrough point to research the auroral flares. |
| B．The X-ray pulses will last for several days on Jupiter. |
| C．The soft X-rays are caused by high-energy ions. |
| D．The X-ray pulses beat regular on Jupiter. |
【推荐2】Scientists have discovered more than 5,000 new species living on the seabed in an untouched area of the Pacific Ocean that has been identified as a future hotspot for deep-sea mining, according to a review of the environmental surveys carried out in the area.
It is the first time the previously unknown biodiversity of the Clarion-Clipperton Zone (CCZ), a mineral-rich area of the ocean floor that spans 1.7m sq miles between Hawaii and Mexico in the Pacific, has been comprehensively documented. The research will be critical to assessing the risk of extinction of the species, given contracts for deep-sea mining in the near-pristine area appear imminent.
Most of the animals identified by researchers exploring the zone are new to science, and almost all are unique to the region: only six, including a carnivorous sponge and a sea cucumber, have been seen elsewhere.
Contracts for mining exploration in the CCZ have been granted to 17 deep-sea mining contractors in an area covering 745,000 sq miles. The companies, which are backed by countries including Britain, the US and China, want to dig for minerals including cobalt manganese and nickel in part to sell to the alternative energy sector.
To better understand the impact of mining this fragile ecosystem and its newly discovered inhabitants, an international team of scientists has built the first “CCZ checklist” by compiling all the records from expeditions to the region. Published in the journal Current Biology, it includes 5,578 different species, of which an estimated 88% to 92% had never before been seen.
To study and collect specimens (样品) from the ocean floor, biologists have joined research cruises in the Pacific that send remote-controlled vehicles to traverse (穿越) the seabed 4,000 to 6,000 meters below. Adrian Glover, a deep-sea biologist at the NHM and senior author of the study described it as an “incredible privilege”. The expedition, funded through the Natural Environment Research Council and others, is backed by UK Seabed Resources (UKSR), a deep-sea mining company that operates the UK’s exploration area. The scientists watch operations by video link direct from the boat as new species are gathered by remote control vehicles in the darkness below.
The seabed, Glover said, is an “amazing place” where, despite the extreme cold and dark, life thrives. “One of the characteristics of the abyssal plain is the lack of food, but life has a way of persisting down there,” he said, “It’s a mystery.” One of the deep-sea animals discovered was nicknamed the “gummy squirrel”, because of its huge tail and jelly-like appearance, he said. There are also glass sponges, some of which look like vases.
With approval for deep-sea mining looming, Glover said he believed it was “imperative that we work with the companies looking to mine these resources to ensure any such activity is done in a way that limits its impact upon the natural world”.
1. What’s the meaning of the underlined word “imminent”?| A．Easy to carry out. | B．Ready to take place. |
| C．Hard to cope with. | D．Important to look over. |
| A．Identifying new species living on the seabed. | B．Assessing the risk of extinction of species. |
| C．Documenting the biodiversity of the area. | D．Exploring the potential for deep-sea mining. |
| A．Abundance of food. | B．Extreme lifeless environment. |
| C．Presence of glass sponges. | D．Prosperous life despite challenging conditions. |
| A．A magic zone:available to mining companies |
| B．A mineral-rich area: Clarion-Clipperton Zone |
| C．An “amazing place”: new species booming |
| D．Deep-sea wonders: the new species found in a Pacific mining hotspot |
【推荐3】The relationship between exercise and cancer has long both intrigued and puzzled oncologists and exercise physiologists.
Exercise is strongly associated with lowered risks for many types of cancer. At the same time, exercise involves biological stress, which typically leads to a short-term increase in inflammation(发炎)which can contribute to higher risks for many cancers.
Now, a new study in mice may offer some clues into the exercise-cancer paradox. It suggests that exercise may change how the immune system deals with cancer by boosting adrenaline(肾上腺素), certain immune cells and other chemicals that, together, can reduce the severity of cancer or fight it off altogether.
To try to better understand how exercise can both elevate inflammation and simultaneously protect the body against cancer, scientists at the University of Copenhagen in Denmark and other institutions decided to closely examine what happens inside mice at high risk for the disease.
So, for the new study, they began by gathering a group of adult lab mice. These animals generally like to run.
The scientists then implanted melanoma (黑素瘤) skin cancer cells into the mice before providing half of them with running wheels in their cages while the other animals remained sedentary. After four weeks, far fewer of the runners had developed full-blown melanoma than the sedentary mice and those that had been diagnosed with the disease showed fewer and smaller lesions.
They drew blood from both the exercising and sedentary animals and cells from any tumors in both groups. As expected, they found much higher levels of the hormone adrenaline in the blood of the exercising animals, especially right after they had been working out on the wheels but also at other times of the day. The body releases adrenaline in response to almost any type of stressful experience, including exercise.
They also found higher levels of interleukin-6 in the blood of the runners. This is a substance that is released by working muscles and is believed to both increase and decrease inflammation in the body, depending on where and how it goes to work.
Perhaps most important, they found much higher numbers in the bloodstreams of runners than in the sedentary mice of a type of immune cell named natural killer cells that are known to be strong cancer fighters.
So the scientists repeated their original experiment multiple times, inducing cancer while allowing some mice to run and others to sit. In some of these follow-up experiments, the scientists injected the runners with a substance that blocked the production of adrenaline and gave sedentary animals large doses of added adrenaline.
What they now found was that when running mice could not produce adrenaline, they developed cancer at the same rate as the sedentary animals, while the sedentary animals that had been injected with extra adrenaline fought off their tumors better than other sitting mice.
More remarkably, the scientists determined that adrenaline seemed to be sending biochemical signals to some of the animals’ IL-6 cells, making them physiologically more alert, so that when a tumor began to develop in the affected animal, those IL-6 cells in turn activated the natural killer cells in the bloodstream and actually directed them to the tumors, like minute guide fish.
With these results, “we show that voluntary wheel running in mice can reduce the growth of tumors, and we have identified an exercise-dependent mobilization of natural killer cells as the underlying cause of this protection,” said Pernille Hojman, a researcher at the University of Copenhagen who oversaw the new study. It perhaps provides one more incentive for us to get up and move.
1. The relationship between exercise and cancer has long puzzled oncologists and exercise physiologists because ________.| A．exercise is strongly associated with lowered risks for many types of cancer |
| B．exercise can both elevate inflammation for many cancers and protect the body against cancer |
| C．exercise may change can reduce the severity of cancer or fight it off altogether |
| D．exercise can increase in inflammation which can contribute to elevated risks for many cancers |
| A．Natural killer cells are much more in the bloodstreams of runners than in the sedentary mice. |
| B．Levels of interleukin-6 are higher in the blood of the runners than in the sedentary mice. |
| C．Exercise such as running seemed to help the mice fight against the cancer. |
| D．Adrenaline can reduce the severity of cancer or fight it off. |
| A．run | B．move | C．sit | D．sleep |
| A．the hormone adrenaline has much higher levels in the blood of the exercising animals |
| B．how these elements in the runners — their increased adrenaline, IL-6, and natural killer immune cells — fight against tumor |
| C．interleukin-6 can both increase and decrease inflammation in the body, depending on where and how it goes to work |
| D．what happens inside mice at high risk for the disease that kill the immune cells |
| A．adrenaline | B．interleukin-6 | C．natural killer cells | D．genes |
【推荐1】Anecdotal evidence has long held that creativity in artists and writers can be associated with living in foreign parts. Rudyard Kipling, Pablo Picasso, Ernest Hemingway, Paul Gauguin, Samuel Beckett and others spent years living abroad. Now a pair of psychologist has proven that there is indeed a link.
As they report in the Journal of Personality and Social Psychology, William Maddux of INSEAD, a business school in Fontainebleau, France, and Adam Galinsky, of the Kellogg School of Management in Chicago, presented 155 American business students and 55 foreign ones studying in America with a test used by psychologists as a measure of creativity Given a candle, some matches and a box of drawing pins, the students were asked to attach the candle to a cardboard wall so that no wax would drip on the floor when the candle was lit. (The solution is to use the box as a candleholder and fix it to the wall with the pin.) They found 60% of the students who were either living abroad or had spent some time doing so, solved the problem, whereas only 42% of those who had not lived abroad did so.
A follow-up study with 72 Americans and 36 foreigners explored their creative negotiating skills. Pairs of students were asked to play the role of seller of a petrol station who then needed to get a job and a buyer who would need to hire staff to run the business. The two were likely to reach a deadlock because the buyer had been told he could not afford what the seller was told was his minimum price. Nevertheless, when both negotiators had lived abroad 70 % struck a deal in which the seller was offered a management job at the petrol station in return for a lower asking price. When neither of the negotiators had lived abroad, none was able to reach a deal.
Merely travelling abroad, however, was not enough. You do have to live there. Packing your beach towel and suntan lotion will not, by itself make you Hemingway.
1. What is the purpose of mentioning the famous names in the opening paragraph?| A．To show the relationship between creativity and living abroad. |
| B．To indicate the link between artistic creation and life experience. |
| C．To emphasize how great these artists are. |
| D．To impress the importance of creativity. |
| A．William Maddux and Adam Galinsky have carefully designed the test. |
| B．Negotiators who had lived abroad are more flexible in negotiating. |
| C．American business students are less creative than those oversea students. |
| D．One's creativity is associated with the length one has spent abroad. |
| A．There exist sharp differences between travelling and living abroad. |
| B．You shouldn't lie on the beach when travelling. |
| C．Only real experience of living abroad can help drive creativity. |
| D．Living abroad is more meaningful than just travelling abroad. |
| A．A diary. | B．A magazine. |
| C．A novel. | D．A guidebook. |
【推荐2】Fortunately, the days of being spread on thick baby oil and lying in the sun to get you skin yellowish-brown—or more likely burnt—are long over. Many sunscreens work by filtering (过滤) the sun’s ultraviolet (UV) rays to keep them from reaching skin cells and causing the DNA damage that can lead to wrinkles and skin cancer. But in recent years, the safety of some of those filtering chemical ingredients, particularly oxybenzone (氧苯铜), has been in question.
A 2019 study published in JAMA found evidence that oxybenzone is absorbed into the bloodstream, leading to concerns about whether it might affect functions of our body. Oxybenzone has also been detected in breast milk for newborn babies. Because of concerns about higher intake in children, doctors from the American Academy of Pediatrics advise against sunscreen with oxybenzone for kids.
The Environmental Working Group, an activist organization that monitors chemical safety, has called for a ban, but the U.S. Food and Drug Administration considers sunscreens with oxybenzone safe. “It’s uncertain,” says Deborah S. Sarnoff, president of the U.S. Skin Cancer Foundation. “Just because you’re absorbing the chemical doesn’t mean it’s dangerous.” Further study is required.
But oxybenzone is a risk to coral reefs. Hawaii and the U.S. Virgin Islands have banned the sale of sunscreens with oxybenzone. In a 2022 study published in Science, researchers found that some certain sea plants, when exposed to sunlight, turn oxybenzone into energy or something needed in a way that damages and kills corals.
Some companies have been trying to stop using oxybenzone gradually in stages, and many big brands offer oxybenzone-free options. For anyone who is pregnant or breastfeeding, or simply looking to avoid these chemical filters, Dr. Sarnoff recommends mineral sunscreens, which contain mainly physical barriers.
1. What is the advantage of sunscreen?| A．It gets your skin yellowish-brown. | B．It stops wrinkles and skin cancer. |
| C．It keeps UV rays from harming you. | D．It prevents skin cells from DNA damage. |
| A．They don’t want children to absorb more oxybenzone. |
| B．They don’t want oxybenzone to hurt babies’ functions. |
| C．They know oxybenzone can affect children’s bloodstream. |
| D．They know oxybenzone has been found in newborn babies. |
| A．Coral reefs in Hawaii were damaged or killed by sunscreens. |
| B．More research is needed to prove the danger of oxybenzone. |
| C．Some organizations have already banned the use of sunscreens. |
| D．Mineral sunscreens are much safer than those with oxybenzone. |
| A．The findings about sunscreens with oxybenzone. |
| B．Questions on safe use of oxybenzone raised by doctors. |
| C．Discussion on safety of oxybenzone between organizations. |
| D．Effects of sunscreens on humans and plants in recent studies. |
【推荐3】Not too many decades ago it seemed “obvious” both to the general public and to sociologists that modern society has changed people’s natural relations, loosened their responsibilities to kin (亲戚) and neighbors, and substituted in their place superficial relationships with passing acquaintances. However, in recent years a growing body of research has revealed that the “obvious” is not true. It seems that if you are a city resident, you typically know a smaller proportion of your neighbors than you do if you are a resident of a smaller community. But, for the most part, this fact has few significant consequences. It does not necessarily follow that if you know few of your neighbors you will know no one else.
Even in very large cities, people maintain close social ties within small, private social worlds. Indeed, the number and quality of meaningful relationships do not differ between more and less urban people. Small-town residents are more involved with kin than are big-city residents. Yet city dwellers compensate by developing friendships with people who share similar interests and activities. Urbanism many produce a different style of life, but the quality of life does not differ between town and city. Nor are residents of large communities any likelier to display psychological symptoms of stress or alienation, a feeling of not belonging, than are residents of smaller communities. However, city dwellers do worry more about crime, and this leads them to a distrust of strangers.
These findings do not imply that urbanism makes little or no difference. If neighbors are strangers to one another, they are less likely to sweep the sidewalk of an elderly couple living next door or keep an eye out for young trouble makers. Moreover, as Wirth suggested, there may be a link between a community’s population size and its social heterogeneity (多样性). For instance, sociologists have found much evidence that the size of a community is associated with bad behavior including gambling, drugs, etc. Large-city urbanities are also more likely than their small-town counterparts to have a cosmopolitan(见多识广)outlook, to display less responsibility to traditional kinship roles, to vote for leftist political candidates, and to be tolerant of nontraditional religious groups, unpopular political groups, and so—called undesirables. Everything considered, heterogeneity and unusual behavior seem to be outcomes of large population size.
1. Which of the following statements best describes the organization of the first paragraph?| A．An argument is examined and possible solutions given. |
| B．Two contrasting views are presented. |
| C．Research results concerning the quality of urban life are presented in order of time. |
| D．A detail description of the difference between urban and small-town life is given. |
| A．could not develop long-standing relationships. |
| B．did not have the same interests as their neighbors. |
| C．tended to be associated with bad behavior. |
| D．usually had more friends. |
| A．disrupt people’s natural relations. |
| B．make them worry about crime. |
| C．cause them no to show concern for one another. |
| D．cause them to be suspicious of each other. |
| A．the better its quality of life |
| B．the more tolerant and open-minded it is. |
| C．the likelier it is to display psychological symptoms of stress. |
| D．the more similar its interests |
