How many things can you see in the night sky? A lot! On a clear night you might see the Moon, some planets, and thousands of sparkling stars.

You can see even more with a telescope. And with bigger and bigger telescopes you can see more and more objects in the sky. And you can see those objects in more and more detail.

But scientists believe there are some things in the sky that we will never see. We won't see them with the biggest telescope in the world, on the clearest night of the year.

That's because they're invisible. They're the mysterious dead stars called black holes.

You might find it hard to imagine that stars die. After all, our Sun is a star. Year after year we see it up in the sky, burning brightly, giving us heat and light. The Sun certainly doesn't seem to be getting old or weak. But stars do burn out and die after billions of years.

As a star's gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.

As the star cools, the outer layers of the star pull in toward the center. The star squashes into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball called a black dwarf. If the star was very big, it keeps squashing inward until it's packed together tighter than anything in the universe.

Imagine if the Earth were crushed until it was the size of a tiny marble. That's how tightly this dead star, a black hole, is packed. What pulls the star in toward its center with such power? It's the same force that pulls you down when you jump--the force called gravity. A black hole is so tightly packed that its gravity sucks in everything--even light. The light from a black hole can never come back to your eyes. That's why you see nothing but blackness.

So next time you stare up at the night sky, remember: there's more in the Sky than we can see! Scattered in the silent darkness are black holes--the great mystery of space.

68. According to the article, what causes a star to die?

A. As its gases run out, it cools down.                B. It has a collision with other stars.

C. It can only live for about a million years.         D. As it gets hotter and hotter, it explodes.

69. Which of the following statements is NOT true?

A. Black holes are dead stars.         B. Black holes have gravity.

C. Black holes are invisible.           D. There is nothing as mysterious as a black hole.

70. What happens AFTER a star dies?

A. It becomes invisible.                              B. It fails to Earth.

C. It burns up all of its gases.                     D. It becomes brighter and easier to see.

71. Why can't you see light when you look at a black hole?

A. Because most black holes are so far away.

B. Because the gravity of a black hole is so strong that it sucks the light inward.

C. Because as the star's gases burn, it stops giving off heat and light.

D. Because as a star cools, its outer layers pull in toward its center.

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay where you are until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated (脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates（旋转）through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

What might be the best title of the passage?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

Which of the following pictures matches the description of the position of the north star?

Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay where you are until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated (脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates（旋转）through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

 What might be the best title of the passage?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

【小题２】Which of the following pictures matches the description of the position of the north star?

【小题３】Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

【小题４】If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay put until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated(脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

67. What might be the best title of the passage ?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

68. Which of the following pictures matches the description of the position of the north star?

69. Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

70. If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay put until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated(脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

68. What might be the best title of the passage ?

A. How to survive in the forest                     B. How to protect yourself in the forest

C. How to direct your way out of the wild                D. What to do if you are lost

69. Which of the following pictures matches the description of the position of the north star? 

70. Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay put until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated(脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

67. What might be the best title of the passage ?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

68. Which of the following pictures matches the description of the position of the north star?

69. Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

70. If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay put until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated(脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

67. What might be the best title of the passage ?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

68. Which of the following pictures matches the description of the position of the north star?

69. Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

70. If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all，but just stay where you are until dawn．Because then you won’t trip over things? No，mainly because you’ll have an idea of direction．The sun rises in the east．But you will be amazed at how many people forget they know that．Apparently，the area underneath a holly bush provides a good makeshift shelter — they are thick，and evergreen．The next thing to do — or rather not to do — is panic，for the obvious reason that unless there is someone there to hear you scream，it will get you nowhere．Just try to think of nice， happy things．

There is always a point in films when a person who is lost in the desert or the snow， dehydrated （脱水的） and exhausted，comes across a set of their own footprints and realizes they have just walked in a huge，round circle．It is wrong to owe it to the unequal strengths or different lengths of your legs．Experiments prove that，without the sun or the moon （or landmarks）as a fixed guide，lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction．To just get out of somewhere，pick a spot on the horizon and just head for it．

There are several ways to find directions in the dark，and by far the best is to establish north using the stars．Most people can identify the Plough，which is part of Ursa Major．It looks a lot like a saucepan．The Plough rotates（旋转）through the sky，but let’s imagine the saucepan lying horizontally （水平地），with its handle on the left．You need to trace a line from the star at the right-hand base of the pan， through the star at the right-hand rim （边沿）， and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars．Then drop a vertical line from the North Star to the horizon and that’s north．

“Tonight is very cloudy and I can’t see the Plough．” Maybe luckily， it is quite windy．Keep in mind that almost all of our weather comes from a south-westerly direction．（This only works if you are in the British Isles）．To find the direction，you can throw light bits of dried-out grass in the air and see which way they blow; or， if there are clouds and patches of clear sky， see which way they blow across the stars．You can also get an idea of direction from leggy plants．If they look as if they have been blown over，they will probably be pointing north-east．If they are simply leaning in one direction as they grow， there’s a good chance that is south （they will be reaching towards the sun）．The last thing to do is to judge your direction and off you go．

1．What might be the best title of the passage?

    A．How to survive in the forest

    B．How to protect yourself in the forest

    C．How to direct your way out of the wild

    D．What to do if you are lost

2．Which of the following pictures matches the description of the position of the north star?

3．Why will people often walk in a circle if they are lost in the desert or the snow?

    A．Because without anything to refer to for directions， the brain will be confused by errors．

    B．Because one of the legs is longer and stronger than the other．

    C．Because the desert or the snow usually covers a large area for people to get across．

    D．Because people usually feel dehydrated and exhausted in the desert or the snow．

4．If you were lost in Taklimakan Desert in China， _________ would NOT be dependable for you to identify the directions．

    A．the sun             B．the North Star    C．wind                 D．the moon

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay out until dawn．Because then you won’t trip over things? No, mainly because you’ll have an idea of direction．The sun rises in the east．But you will be amazed at how many people forget they know that．Apparently, the area underneath a holly bush provides a good makeshift shelter—they are thick, and evergreen．The next thing to do—or rather not to do—is panic, for the obvious reason that unless there is someone there to hear you scream．it will get you nowhere．Just try to think of nice, happy things．

There is always a point in films when a person who is lost in the desert or the snow, dehydrated （脱水的） and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle．It is wrong to owe it to the unequal strengths or different lengths of your legs．Experiments prove that, without the sun or the moon（or landmarks） as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction．To just get out of somewhere, pick a spot on the horizon and just head for it．

There are several ways to find directions in the dark, and by far the best is to establish north using the stars．Most people can identify the Plough, which is part of Ursa Major．It looks a lot like a saucepan．The Plough rotates （旋转） through the sky, but let’s imagine the saucepan lying horizontally, with its handle on the left．You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim （边沿）, and follow it upwards; the North Star is roughly five times the distance between those two ‘pointer” stars．Then drop a vertical line from the North Star to the horizon and that’s north．

“Tonight is very cloudy and I can’t see the Plough．” Maybe luckily, it is quite windy．Keep in mind that almost all of our weather comes from a south-western direction．（This only works if you are in the British Isles．）To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars．You can also get an idea of direction from leggy plants．If they look as if they have been blown over, they will probably be pointing north-east．If they are simply leaning in one direction as they grow, there’s a good chance that it is south （they will be reaching towards the sun）．The last thing to do is to judge your direction and off you go．

1．What might be the best title of the passage?

       A．What to do if you are lost

       B．How to protect yourself in the forest

       C．How to survive in the forest

       D．How to direct your way out of the wild

2．Which of the following pictures matches the description of the position of the North Star?      

3．Why will people often walk in a circle if they are lost in the desert or the snow?

       A．Because without anything to refer to for directions, the brain will be confused by errors．

       B．Because one of the legs is longer and stronger than the other．

       C．Because the desert or the snow usually covers a large area for people to get across．

     D．Because people usually feel dehydrated and exhausted in the desert or the snow．

4．If you were lost in the Talklimakan Desert in China, ____ would NOT be dependable for you to identify the directions．

       A．the sun                B．the North Star      C．the moon             D．the wind