Thi Thử VSTEP Đề 4 Reading Test 1 Part 2

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 3 QUESTIONS 21 - 30

The Solar System, as we know it, contains over 178 objects which revolve around our central star, or the Sun. Some of these objects can be seen from Earth with the unaided eye or an earth-based telescope, but the majority have only been detected through the development of instruments such as the Hubble Space Telescope, or unmanned probes like Voyager. These instruments operate outside Earth's atmosphere collecting information on thecompositionand behavior of objects in the Solar System, which has enabled researchers to hypothesize their origins.

[A] It is generally thought that a cloud of interstellar gas and dust known as a "nebula", was disturbed by some major event in space, possibly a supernova, about five billion years ago and began to collapse under its own gravity, forming a cloud. [B] The center of the cloud became so hot that it eventually exploded into a star with the cooler gases flowing around it. [C] In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. [D] These solid particles collided with each other to form larger objects, or asteroids, as they continued to spin around our central star.

As these asteroids increased in size, their gravity began to pull in all the material in their immediate surroundings, and the largest of these went on to become planets. Thevery different composition of the inner planets (Mercury, Venus, Earth and Mars) and the outer planets (Jupiter, Saturn, Neptune and Uranus)has led astronomers to hypothesize that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun, where all the ice particles were vaporized due to the incredible heat, were formed mostly of rock, silicates, and metals with high melting points. These particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any, satellites, which would indicate that most of the available material was either pulled into their own gravity or burned away in the heat of the Sun.

The inner and outer planets are separated by an asteroid belt, consisting of material that was not able to form into planets due to Jupiter's immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as material was thrown out from the center by the spinning star's centrifugal force. About a million years after the cooling of the original nebula, the Sun began to emit a stream of charged protons and electrons known as solar wind which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects in their vast gravity fields, some of which are big enough to be termed "satellites", and countless smaller fragments which formed rings around the planets.

The discovery of more objects in the Solar System in recent times has led to the need for further clarification. Far beyond the outer planets lies Pluto, which was originally considered to be the ninth planet, but which has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto's origins may be in the recently discovered Kuiper Belt, the source of many of the comets which travel through the Solar System. This theory is based on Pluto's rock/ice composition which is similar to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far, the others being Eris and Ceres.

Scientific knowledge is only as good as the ability of scientists to collect evidence, so as new advances are made in astronomy, the present theories may be disproved, as in the case of Pluto. The above account represents the consensus of current opinions on the matter.

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]

PASSAGE 4 QUESTIONS 31 - 40

Ocean Thermal Energy Conversion (OTEC) is a method of producing electricity developed from the temperature difference that subsists between deep and shallow waters. It converts solar radiation to electric power. The system uses the ocean's natural thermal gradient to direct a power-producing cycle. To produce a significant amount of power, the temperature between warm water on the surface and deep cold water should differ by about 20 degrees Celsius. On average, 23 million square miles of tropical seasabsorban amount of solar radiation equal in heat content to about 250 million barrels of oil. If less than one tenth of this could beconvertedinto electric power, it would provide more than 20 times the total amount of electricity utilized in America on any given day.

Oceans are a huge renewable resource with the possibility of producing millions of watts of electric power. Some experts think the cold, deep seawater that is used in the OTEC process is rich in nutrients and, therefore, can be used to culture marine and plant life on shore or on land.

There are certain conditions which have to be met to enable OTEC to work. First, commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. This means that they must be built on land or submerged on the continental shelf. In addition, the natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20°N and 20°S.The temperature of the surface watermust differ from that of deep water and allowances should be made for a wide-open space. Tropical islands meet the requirements for a wide space, so they are areas for OTEC development. Land-based facilities offer advantages. For example, plants do not require extensive maintenance, and they can be installed in sheltered areas, safe from storms and general bad weather. Land-based sites allow OTEC plants to function with related industries.

Thermal energy from the ocean was first proposed as far back as 1881. However, it wasn't until 1930 that a system was built, producing 22kW of electricity. Another was constructed sometime later, but it was destroyed by waves. In 1980, the U.S department of energy built a site for OTEC heat exchangers on board a navy ship. Tests revealed that OTEC systems are able to function on slow moving ships and are of little consequence to the surrounding marine environment.

In 1981, Japan established a closed-cycle plant in the Pacific Ocean, producing 40,000 watts of electricity. In May 1993, another 50,000 watts of electricity was produced. However, it was an impractical energy source as the materials used were expensive. Currently, scientists are continuing to develop more cost effective and open-cycle OTEC systems.An integrated OTEC system can help create harmonious, self-sustaining island communities, independent of imported fossil fuels and their associated costs.

Tidal energy is another form of ocean energy caused by the gravitational pull of the moon and sun, and the rotation of the Earth. When tides come into shore, they can be trapped in reservoirs behind dams. Then when the tide lowers, the water behind the dam can be released, functioning similarly to a hydroelectric power plant. Tidal dams can change the tidal level in the local basin, affecting the navigation. The prime disadvantage is the effect a tidal station has on plants and animals. However, tidal fences, which are also used to channel the energy of tides, have less environmental impact than traditional sources of power such as fossil fuels or nuclear power, and are cheaper to install.

Turbines are devices with blades attached to a central rod that spin when a force hits the blades. [A] This spinning motion is extremelypractical. The first turbine used was the undershot waterwheel, probably the oldest type of waterwheel dating back over 2,000 years. [B] Waterwheels and windmills were the first turbines; their wooden blades captured the power of wind or rivers to lift water for irrigation or to rotate huge stones to grind grain. [C] It wasn't until the 1880s, when the generator was first invented, that people began using turbines to produce electricity. [D]