神马作文网15分求一篇 英语科普文.要新的.别到处复制.
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15分求一篇 英语科普文.要新的.别到处复制.
最好是最近的事实描写.
最好是最近的事实描写.
帮您找了两篇有关天文的科普文,希望对您有所帮助：
Black Holes(黑洞)
Black holes are some of the strangest things in space. A black hole sucks in anything that gets near it. Nothing can escape from a black hole—not even light.
BLACK HOLES ARE STRONG
Nothing escapes from a black hole because its gravity is so strong. Gravity is a force that pulls one thing to another. Gravity is the force that holds you down on Earth. When you jump up, Earth’s gravity pulls you right back down. Earth’s gravity also makes the Moon orbit (go around) Earth.
The more matter (stuff) that is packed in a star, planet, moon, or other object, the stronger is its gravity. Gravity makes an object with more matter pull an object with less matter toward it. The Sun has a lot more matter than Earth. The Sun’s gravity pulls on Earth. It makes Earth orbit the Sun.
Matter is packed very tightly in some things and loosely in others. The matter that makes up an iron ball is packed much tighter than the matter that makes up a bag of feathers. A scientist would say that an iron ball is much denser than a bag of feathers.
A black hole is denser than anything you could imagine. A black hole could have a million times more stuff than our Sun. All of this stuff would be packed into an area smaller than a city. The force of gravity from so much stuff packed into such a small area is awesome.
WHERE DO BLACK HOLES COME FROM?
Astronomers and physicists think black holes come from dying stars. A dying star burns out and stops shining. All the stuff that makes up the star starts falling in on itself. The star gets denser and denser. If the star is big enough and has enough matter, it could get dense enough to become a black hole.
STUDYING BLACK HOLES
No one has really seen a black hole. You cannot see black holes because they do not give off any kind of light. Physicists used math to predict that black holes exist.
Astronomers look for signs of black holes. Astronomers study powerful rays coming from stars in deep space. The stars seem to be orbiting black holes. Astronomers think that black holes are sucking gas from the stars, and this makes the stars give off X rays.
Galaxies are enormous groups of stars. Astronomers think that most galaxies have huge black holes at their centers. The Hubble Space Telescope took pictures of a disk of hot gases at the center of our own Milky Way Galaxy. Astronomers think this disk is going around an enormous black hole right in the center of our galaxy.
Big Bang(宇宙大爆炸)
The universe contains everything that exists: Earth, the Sun, the stars, galaxies (collections of billions of stars), and everything else in space. People have wondered how the universe got started for thousands of years. Most scientists now think they have the answer. They think the universe began about 14 billion years ago with a kind of big explosion. They call the explosion the big bang.
WHAT HAPPENED AFTER THE BIG BANG?
No one knows what caused the big bang, but scientists think they know what happened all the way back to the first seconds after the big bang.
The brand new universe was very hot and very small. It blew outwards very fast. In the first three minutes, matter started to form. Hundreds of years later, the universe looked like a big ball of fire.
You can picture the universe as something like a black balloon with white dots painted on it. The black represents space and the white dots are galaxies. Blowing air into the balloon makes it bigger. The spaces between each dot get farther apart as the balloon expands.
As it got bigger, the universe got cooler. Hydrogen gas formed. The gas broke into clumps. The clumps came together to make galaxies and stars. Other kinds of matter formed in the stars. Finally, planets like Earth formed around some stars.
IS THERE PROOF OF A BIG BANG?
The expansion of the universe is evidence for the big bang. American scientist Edwin Hubble studied light coming from galaxies far out in the universe. In 1929, he found that the galaxies were speeding away from Earth and from each other in all directions. Scientists tracked the paths of the galaxies back to their starting place. They saw that all the galaxies must have started from the same place. Packing all that matter into a small area would make a very dense, searing hot ball—the big bang.
Scientists use math to describe how the universe behaves. In the early 1900s, German American scientist Albert Einstein came up with equations that predict an expanding universe. These equations have correctly predicted the motions of stars, planets, and light.
More proof came in the 1990s from a spacecraft called the Cosmic Background Explorer (COBE). COBE saw rays coming from far off in the universe. The rays are left over from the early days of the universe. They could only have been created in a much smaller and hotter universe long ago.
WILL THE UNIVERSE KEEP EXPANDING?
Scientists are not sure what will happen to the universe. They currently think it will keep expanding forever. They even think the expansion is speeding up. But scientists are still studying this question.
Black Holes(黑洞)
Black holes are some of the strangest things in space. A black hole sucks in anything that gets near it. Nothing can escape from a black hole—not even light.
BLACK HOLES ARE STRONG
Nothing escapes from a black hole because its gravity is so strong. Gravity is a force that pulls one thing to another. Gravity is the force that holds you down on Earth. When you jump up, Earth’s gravity pulls you right back down. Earth’s gravity also makes the Moon orbit (go around) Earth.
The more matter (stuff) that is packed in a star, planet, moon, or other object, the stronger is its gravity. Gravity makes an object with more matter pull an object with less matter toward it. The Sun has a lot more matter than Earth. The Sun’s gravity pulls on Earth. It makes Earth orbit the Sun.
Matter is packed very tightly in some things and loosely in others. The matter that makes up an iron ball is packed much tighter than the matter that makes up a bag of feathers. A scientist would say that an iron ball is much denser than a bag of feathers.
A black hole is denser than anything you could imagine. A black hole could have a million times more stuff than our Sun. All of this stuff would be packed into an area smaller than a city. The force of gravity from so much stuff packed into such a small area is awesome.
WHERE DO BLACK HOLES COME FROM?
Astronomers and physicists think black holes come from dying stars. A dying star burns out and stops shining. All the stuff that makes up the star starts falling in on itself. The star gets denser and denser. If the star is big enough and has enough matter, it could get dense enough to become a black hole.
STUDYING BLACK HOLES
No one has really seen a black hole. You cannot see black holes because they do not give off any kind of light. Physicists used math to predict that black holes exist.
Astronomers look for signs of black holes. Astronomers study powerful rays coming from stars in deep space. The stars seem to be orbiting black holes. Astronomers think that black holes are sucking gas from the stars, and this makes the stars give off X rays.
Galaxies are enormous groups of stars. Astronomers think that most galaxies have huge black holes at their centers. The Hubble Space Telescope took pictures of a disk of hot gases at the center of our own Milky Way Galaxy. Astronomers think this disk is going around an enormous black hole right in the center of our galaxy.
Big Bang(宇宙大爆炸)
The universe contains everything that exists: Earth, the Sun, the stars, galaxies (collections of billions of stars), and everything else in space. People have wondered how the universe got started for thousands of years. Most scientists now think they have the answer. They think the universe began about 14 billion years ago with a kind of big explosion. They call the explosion the big bang.
WHAT HAPPENED AFTER THE BIG BANG?
No one knows what caused the big bang, but scientists think they know what happened all the way back to the first seconds after the big bang.
The brand new universe was very hot and very small. It blew outwards very fast. In the first three minutes, matter started to form. Hundreds of years later, the universe looked like a big ball of fire.
You can picture the universe as something like a black balloon with white dots painted on it. The black represents space and the white dots are galaxies. Blowing air into the balloon makes it bigger. The spaces between each dot get farther apart as the balloon expands.
As it got bigger, the universe got cooler. Hydrogen gas formed. The gas broke into clumps. The clumps came together to make galaxies and stars. Other kinds of matter formed in the stars. Finally, planets like Earth formed around some stars.
IS THERE PROOF OF A BIG BANG?
The expansion of the universe is evidence for the big bang. American scientist Edwin Hubble studied light coming from galaxies far out in the universe. In 1929, he found that the galaxies were speeding away from Earth and from each other in all directions. Scientists tracked the paths of the galaxies back to their starting place. They saw that all the galaxies must have started from the same place. Packing all that matter into a small area would make a very dense, searing hot ball—the big bang.
Scientists use math to describe how the universe behaves. In the early 1900s, German American scientist Albert Einstein came up with equations that predict an expanding universe. These equations have correctly predicted the motions of stars, planets, and light.
More proof came in the 1990s from a spacecraft called the Cosmic Background Explorer (COBE). COBE saw rays coming from far off in the universe. The rays are left over from the early days of the universe. They could only have been created in a much smaller and hotter universe long ago.
WILL THE UNIVERSE KEEP EXPANDING?
Scientists are not sure what will happen to the universe. They currently think it will keep expanding forever. They even think the expansion is speeding up. But scientists are still studying this question.