Black Holes
1. Black holes can be best described as a sort of vacuum, sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer burn due to loss of fuel, and because its temperature can no longer control the gravitational (重力的) force, hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses.
2. Black holes come from stars that are made of hydrogen, other gases and a few metals. When these explode it can turn into a stellar-mass (恒星质量) black hole, which can only occur if the star is large enough (should be bigger than the sun) for the explosion to break it into pieces, and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun ends up being a black hole that’s no longer than 70 kilometers, then the Earth would become a black hole that’s only a fraction of an inch!
3. Objects that get sucked in a black hole will always remain there, never to break free. But remember that black holes can only gobble up (吞噬) objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole, but the sun will continue to stay in place. Orbits do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only this time its mass is totally contracted that it can end up as no bigger than a state.
4. So far, astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity. In the end, through numerous studies, they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is nearly impossible to detect black holes via a telescope. But astronomers continue to study galaxies, space and the solar system to understand how black holes might evolve. It is possible that black holes can exist for millions of years, and later contribute to a bigger process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form.

第一篇
Energy and Public Lands
The United States boasts substantial energy resources. Federal lands provide a good deal of U.S. energy production; the U.S. Department of the Interior manages federal energy leasing, both on land and on the offshore Outer Continental Shelf. Production from these sources amounts to nearly 30 percent of total annual U.S. energy production. In 2000, 32 percent of U.S. oil, 35 percent of natural gas, and 37 percent of coal were produced from federal lands, representing 20,000 producing oil and gas leases and 135 producing coal leases. Federal lands are also estimated to contain approximately 68 percent of all undiscovered U.S. oil reserves and 74 percent of undiscovered natural gas. Revenues from federal oil, gas, and coal leasing provide significant returns to U.S. taxpayers as well as State governments. In 1999, for example, $553 million in oil and gas revenues were paid to the U.S. Treasury, and non-Indian coal leases accounted for over $304 million in revenues, of which 50 percent were paid to State governments. Public lands also play a critical role in energy delivery. Each year, federal land managers authorize rights of way for transmission lines, rail systems, pipelines, and other facilities related to energy production and use. Alternative energy production from federal lands lags behind conventional energy production, though the amount is still significant. For example, federal geothermal resources produce about 7.5 billion kilowatt-hours of electricity per year, 47 percent of all electricity generated from U.S. geothermal energy. There are 2,960 wind turbines on public lands in California alone, producing electricity for about 300,000 people. Federal hydropower facilities produce about 17 percent of all hydropower produced in the United States. Because of the growing U.S. thirst for energy and increasing public unease with dependence on foreign oil sources, pressure on the public lands to meet U.S. energy demands is intensifying. Public lands are available for energy development only after they have been evaluated through the land use planning process. If development of energy resources conflicts with management or use of other resources, development restrictions or impact mitigation measures may be imposed, or mineral production may be banned altogether.

第二篇
Putting Plants to Work
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels for decades. But plants are the real experts: They’ve been using sunlight as an energy source for billions of years. Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into sugars and starches, stored energy that the plants can use. This conversion process is called photosynthesis. Unfortunately, unless you’re a plant, it’s difficult and expensive to convert sunlight into storable energy. That’s why scientists are taking a closer look at exactly how plants do it. Some scientists are trying to get plants, or biological cells that act like plants, to work as miniature photosynthetic power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden, Colo., is working with green algae. She’s trying to trick them into producing hydrogen instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficiently, the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity. The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches. "But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen." Ghirardi says. For example, algae will produce hydrogen in an airfree environment. It’s the oxygen in the air that prevents algae from making hydrogen most of the time. Working in an airfree environment, however, is difficult. It’s not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present. Unfortunately, removing the sulfate also makes the algae’s cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells’ activity and produce larger quantities of hydrogen. The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: "You can grow them in a reactor, in a pond. You can grow them in the ocean. There’s a lot of flexibility in how you can use these organisms."

The Tough Grass that Sweetens Our Lives
Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their gardens. Gradually a different variety evolved which contained sucrose and was chewed on for its sweet taste. Over time, sugar cane became a highly valuable commercial plant, grown throughout the world. 46  Sugar became a vital ingredient in all kinds of things, from confectionery to medicine, and, as the demand for sugar grew, the industry became larger and more profitable. 47 Many crops withered and died, despite growers’ attempts to save them, and there were fears that the health of the plant would continue to deteriorate. In the 1960s, scientists working in Barbados looked for ways to make the commercial species stronger and more able to resist disease. They experimented with breeding programmes, mixing genes from the wild species of sugar cane, which tends to be tougher, with genes from the more delicate, commercial type. 48  This sugar cane is not yet ready to be sold commercially, but when this happens, it is expected to be incredibly profitable for the industry.  49  Brazil, which produces one quarter of the world’s sugar, has coordinated an international project under Professor Paulo Arrudo of the Universidade Estaudual de Campinas in Sao Paulo. Teams of experts have worked with him to discover more about which parts of the genetic structure of the plant are important for the production of sugar and its overall health. Despite all the research, however, we still do not fully understand how the genes function in sugar cane. 50  This gene is particularly exciting because it makes the plant resistant to rust, a disease which probably originated in India, but is now capable of infecting sugar cane across the world. Scientists believe they will eventually be able to grow a plant which cannot be destroyed by rust.

Wide World of Robots
Engineers who build and program robots have fascinating jobs. These researchers tinker (修补) with machines in the lab and write computer software to control these devices. "They’re the best toys out there," says Howie Choset at Carnegie Mellon University in Pittsburgh. Choset is a robotics, a person who designs, builds or programs robots. When Choset was a kid, he was interested in anything that moved — cars, trains, animals. He put motors on Tinker toy cars to make them move. Later, in high school, he built mobile robots similar to small cars. Hoping to continue working on robots, he studied computer science in college. But when he got to graduate school at the California Institute of Technology in Pasadena, Choset’s labmates were working on something even cooler than remotely controlled cars: robotic snakes. Some robots can move only forward, backward, left and right. But snakes can twist (扭曲) in many directions and travel over a lot of different types of terrain (地形). "Snakes are far more interesting than the cars," Choset concluded. After he started working at Carnegie Mellon, Choset and his colleagues there began developing their own snake robots. Choset’s team programmed robots to perform the same movements as real snakes, such as sliding and inching forward. The robots also moved in ways that snakes usually don’t, such as rolling. Choset’s snake robots could crawl (爬行) through the grass, swim in a pond and even climb a flagpole. But Choset wondered if his snakes might be useful for medicine as well. For some heart surgeries, the doctor has to open a patient’s chest, cutting through the breastbone. Recovering from these surgeries can be very painful. What if the doctor could perform the operation by instead making a small hole in the body and sending in a thin robotic snake Choset teamed up with Marco Zenati, a heart surgeon now at Harvard Medical School, to investigate the idea. Zenati practiced using the robot on a plastic model of the chest and then tested the robot in pigs. A company called Medrobotics in Boston is now adapting the technology for surgeries on people. Even after 15 years of working with his team’s creations, "I still don’t get bored of watching the motion of my robots," Choset says.

Black Holes
1. Black holes can be best described as a sort of vacuum, sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer burn due to loss of fuel, and because its temperature can no longer control the gravitational (重力的) force, hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses.
2. Black holes come from stars that are made of hydrogen, other gases and a few metals. When these explode it can turn into a stellar-mass (恒星质量) black hole, which can only occur if the star is large enough (should be bigger than the sun) for the explosion to break it into pieces, and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun ends up being a black hole that’s no longer than 70 kilometers, then the Earth would become a black hole that’s only a fraction of an inch!
3. Objects that get sucked in a black hole will always remain there, never to break free. But remember that black holes can only gobble up (吞噬) objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole, but the sun will continue to stay in place. Orbits do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only this time its mass is totally contracted that it can end up as no bigger than a state.
4. So far, astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity. In the end, through numerous studies, they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is nearly impossible to detect black holes via a telescope. But astronomers continue to study galaxies, space and the solar system to understand how black holes might evolve. It is possible that black holes can exist for millions of years, and later contribute to a bigger process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form.

He paused, waiting for her to digest the information.（）

The contract between the two companies will expire soon.（）

Come out, or I’ll bust the door down.（）

Make sure the table is securely anchored.（）