Chapter 4 Chapter 3 The Blue Planet

Eratosthenes Denise, who measured the size of the Earth, is arguably the greatest example of the power of the mathematical geniuses of the ancient Greeks to conquer space.Before the time when the Alexandrian survey was carried out, man's interest in the world in which he lived was purely geographical. In fact, Eratosthenes Denius himself was a famous geographer.But his remarkable feat was not just an achievement in the field of geography.This is the first time that human beings regard the earth as a whole and a celestial body.Eratos Deneus placed the earth among the stars. Later, many other important turning points in the history of human knowledge were also associated with changes in thinking about the nature of the earth.The idea that the earth is a sphere rather than a flat disk gave rise to the great geographical expeditions of the fifteenth and sixteenth centuries, a glorious age that brought the world's continents within the reach of Western knowledge. Inside.The recognition that the Earth is a planet orbiting the sun gave rise to modern astronomy.There are still many aspects of our planet today that have not been explored in detail, and the importance of Earth science is increasing every year.Only recently did scientists arrange the largest single international research effort, called the International Year of Geophysics, to do a thorough physical examination of the Earth and to further study the forces of matter in the solar system and universe, and our planet is Part of the solar system and universe.

Since we live on the surface of the earth, it is difficult to stand far away and have an unbiased view of the earth as a whole.If the earth were not our home, perhaps our impression of it would be quite different, and more representative of its true nature.Now that we are going to do some research on this stone ball flying in space, we might as well be imaginative and see what our hometown looks like with the eyes of outsiders. Suppose you are not from Earth, but are part of a technologically advanced race that lives on a planet orbiting a star somewhere in the far reaches of the Milky Way galaxy.Those of your race have solved the problem of flying between the stars and the Milky Way long ago.Of course, the distances between the stars are too great to use any of the old-fashioned methods of space travel, such as slowing down at the speed of light.In that way, it would take about thirty thousand years to fly from the center of the Milky Way to the outside of its protruding vortex handle, where our sun is.One-tenth of this journey takes longer than your whole life, although your people have figured out how to live longer than people on earth.

Leaving aside for the moment travel at the speed of light; suppose you have a way of transporting yourself easily from one part of the galaxy to another.One day, you set off with an expedition to explore the outer reaches of the Milky Way.On the way, you came close to our sun by chance.This not particularly bright star is completely invisible to the naked eye on your planet.The people on your planet only detected our sun from the photos. The photos were taken with a very large telescope. Our sun is just a faint dot in the photos, and we need to use a mirror to see clearly. , which is mixed with a thousand other little dots.This very ordinary star is not surprising among the stars in Tianhe, and it does not attract the special attention of the viewers at all.But the route you have taken takes you to a place only ten billion miles away from our sun, which is an ordinary star, but since you are so close to it, you cannot help but change your course a little, and come near it. Take a closer look.

You are about three times farther away from the sun than Pluto, the farthest planet in the solar system.Since you are so far away from the sun, if you look at it with your naked eyes, what you see is not a disk, but a small dot.But he was radiant, nearly a thousand times brighter than Venus among the planets, which, seen from earthlings, is the brightest light in the sky after the moon and the sun itself.Now you turn to the sun, propelled by the power of old rockets instead.You travel at a speed slightly less than the speed of light and can expect to reach the sun in about fifteen hours. You are now in the outer orbit of the solar system.The planets were shown to you one by one, and you studied them exhaustively with the sophisticated instruments and methods produced by your advanced culture.People on Earth have spent thousands of years figuring out all the known facts about the nine planets, but you know everything in just a few hours.You find that the planets and the sun are mostly ordinary, just like the stars you saw on your previous interstellar explorations.All planets, with the exception of two, are pretty mediocre.

There is a sixth planet, which is called Saturn by people on earth.It was adorned with a whole set of great rings, which glistened in the sun like a necklace of pearls.You've seen similar rings around planets in other galaxies, but none as beautiful as the rings around Saturn.These rings are extremely thin, proportionally thinner than a sheet of tissue paper several feet wide.Their mathematical sophistication is marvelous, forming a perfect set of concentric circles, as if drawn with gigantic compasses on the dark canvas of the sky.You have never seen such a splendid decoration on any planet.

You see planet number three again.This planet has a moon, which is enormous for its size; in fact, the two bodies may be said to form a double star.Planet number three revolves once every twenty-four hours on its own axis, and rounds its sun every three hundred and sixty-five days and hours.But what sets this planet apart from all others is its strange color, even from a great distance.All the other planets are reddish, yellow or white, only the outer planets are tinged with green.But the third planet is blue. In fact, it is the only blue planet in the entire solar system. As you pass by Planet Number Three, its entire surface, illuminated by the sun's rays, appears to glow in subdued colours.There were patches of orange and green in places, and large patches of harsh white, but the blue was always visible.The entire planet hangs in a veil of bluish mist, and you can see large areas of its surface that are a deep, watery blue.

But there are other factors that set Planet Three apart from all the others.The sun is reflected on the surface of this planet.A blindingly intense light was emitted, making this great sphere appear perfectly round.It floats in space like a sparkling ball hanging from a Christmas tree.This strong reflection is caused by a remarkable feature: the planet's surface is mostly water!No other planet in the solar system has liquid on its surface. Now you know what the planet Earth looks like to a traveler from another world from outer space.You might as well try to take a closer look at it from a fresh, unbiased perspective.This is not an easy task, because we live on this planet, and all the characteristics of it that we feel are distorted and unreal because of their proximity to us.For example, because of the enormous size of our planet, we have always had a wrong conception of the relative size of everything associated with it.Now, to make things easier for us to understand, we might as well make ourselves a model of the Earth, about two feet (61 cm) in diameter, about twice the size of a normal globe.The scale is about one to twenty million.But our model is not an ordinary globe.Everything on and in the model is to be true, and to be in exact and exact proportions to the actual length, width, height, and depth.Now we're about to make some amazing discoveries.

Check first the weight of our earth: here is where the first surprise happened to me.The model weighs 1,300 pounds, which is as heavy as eight burly grown men!In fact, our planet is surprisingly heavy; for its size, it is the heaviest of all planets, since no other planet is composed of matter so dense as that of the earth.Most of the Earth is made of various heavy metals: the core is roughly iron and nickel contained in a rocky shell. The weight of the earth is so singular that all other features seem insignificant by comparison.Take the atmosphere, for example.We always thought it was an extremely deep ocean of gas, reaching as far as space.In fact, the atmosphere is just a very thin layer of fog, close to the surface of the earth.We have a hard time finding a substance that represents the extreme thinness of the atmosphere on the exact scale of our model of the Earth.Only the quilt woven of the most slender and closest to invisible kermell silk can barely match the thinness of the atmosphere on the surface of our earth model.A cigarette smoker exhales a small smoke ring that spreads evenly around the model, roughly representing the extent of our atmosphere.

All oceans add up to more than two-thirds of the Earth's surface.In our earth model, the proportion of the ocean is exactly the same as the real situation, not only the area is true to reality, but also the amount of water contained in the ocean is true to reality.If you reach out and touch the mid-pacific on the model, your fingertips will only be slightly damp.Can we correctly represent the immeasurable vastness of water in the Pacific Ocean in terms of slight humidity?This is the right adjective for our model, since the ocean depth on the model is less than one-hundredth of an inch.If we gather the water from all the oceans on the model, it's only about half a glass of juice!

In addition to sea water, there is fresh water on the earth.How much fresh water does our model need?One drop of water from an eyedropper is too much; so we use a sprinkler that sprays a drop roughly one-tenth the size of the drop that comes out of the eyedropper.This small drop of water is enough to fill all the inland lakes on the earth, such as the Great Lakes of North America, Lake Victoria, Alar Sea, etc.; it can also fill the major rivers such as the Amazon River, Mississippi River, and the Nile; With rivers and underground freshwater reservoirs, it also supplies sufficient moisture for storms!

Not all of Earth's water is liquid; a large portion freezes into ice.In fact, there is more ice on Earth than fresh water.The wide valleys of the high mountains in most regions are filled with glaciers.But most of the ice has frozen into a blanket of ice that covers and surrounds the tops of the North and South Poles.Airline passengers flying over the North Pole and looking at the ice on the earth must have thought it infinitely great, especially when they heard that in some places on Greenland and Antarctica the ice blanket was two miles thick.But as far as the whole earth is concerned, adding up all the ice is equivalent to forming a thin layer of frost on the north and south poles.The sharp point of an ordinary icicle will melt instantly in your hand; such a small amount of ice will suffice for our models.Spreading this bit of ice evenly over the north and south poles would create a layer of ice about as thick as a thin sheet of cellophane. The tallest mountains, such as Mount Everest in the Himalayas, and the deepest ocean trenches, such as the seven-mile-deep chasm near the Mariana Islands, are barely visible on our models.The entire sphere appears almost completely smooth.This makes us wonder, because the common bump models of mountains and oceans are greatly exaggerated: they have to be so exaggerated in order to give a strong impression. For our model, we did a little trick to make mountains and trenches come into view.We project the edge of the model on the screen, magnify it many times, and draw an arc with two feet, and compare it with the projection of the edge of the model.In this way, we can see the slight unevenness on the edge of the earth, that is, the high mountains and the deep sea bottom.The average ocean on Earth is no deeper than two sheets of writing paper, and mountains are no taller than the creases of a small piece of cellophane are creased and laid out straight on a smooth surface. According to the same representation method, the hard rock shell of the earth also appears extremely thin.We might as well dig out the solid part of the United States on the model.The piece we dug up was hollow in the middle, like a bowl, with bumps and bumps all around, and was thinner than an egg shell.It was about nine inches long, six inches wide, and less than a tenth of an inch thick.This is indeed very different from what we see on the flat map! Models are extremely useful in correcting many of the world's misconceptions about the length, breadth, height, and depth of the earth and its features.There is a misconception that Texas is bigger than California.In fact, the latter is greater than the former.Texas is fairly flat, with a statewide average height above sea level that is small, while California is mountainous.In terms of land area above sea level, California represents more than Texas.Actually, if you want to see how California is bigger than Texas, you just have to weigh both on a scale if you have the chance. Wait a minute, a person in Texas can still say that his lovely hometown is bigger than the United States including California, Alaska, Hawaii, and even Texas itself!Texas stretches far and wide on the globe, so it has a slight but noticeable curvature.We dug out a piece of the earth model occupied by Texas, and put it on the platform facing the sky. It is shaped like a flat and slightly concave disk.Let's take the whole of the United States above sea level, including Alaska, which was recently listed as a state in the United States, and squeezed out the status of the largest state occupied by Texas. The method is to cut off everything beyond the sea. Plane size mountains, plains, soil and rocks.The chipped things, in a small pile, were put into the Texas concave tray.The plate is only slightly more than half full!In this way, isn't the whole of the United States, including Texas, smaller than Texas, because it can easily accommodate fifty states above the level.There is actually a handle on the plate that can hold it up. Digging out a chunk of North America deprived our model of Earth of a solid crust.And so the red, molten core of the earth was exposed.We see how unbelievably thin the solid crust actually is: proportionally, it is only twice as thick as the shell of an egg.Almost ninety-nine percent of the entire mass of the Earth is molten or mushy; only slightly more than one percent is solid.If we can call this molten matter a liquid, it is indeed a strange liquid that fills my planet.During an earthquake, these guts of the earth behave as if they were made of refined steel.The shock wave of the earthquake travels a long distance with great speed, which is only possible when these viscera are extremely dense.In fact, during earthquakes, our planet behaves as if a steel ball were struck by a large hammer. It seems paradoxical: during an earthquake the earth behaves like a steel ball, but under other circumstances it behaves like a ball of jelly ready to melt and flow.Even its hard, stony crust changes shape easily under pressure.Fortunately, our Earth rotates rather slowly, so it remains almost perfectly circular (the diameter of the equator on our model Earth is only one-tenth of an inch longer than the distance between the North and South Poles.).But if we managed to make the Earth spin seventeen times faster than it currently does, the centrifugal force at the equator would cancel out the gravitational force.At that time, the earth will begin to divide, and the seas and lands will fly away piece by piece, like sparks bursting from a grinding wheel. How can the earth be as hard as steel and as soft as jelly at the same time?This is because it is huge.As a thing grows bigger and bigger, its hardness decreases more and more.Let's take a little ladybug as an example.It weighs less than one-hundredth of a tael.But it is so powerful that it can carry a hundred ladybugs on its back.Among human beings, only a strong man like Mount Tai can carry three or four people on his back.A man is much larger than a ladybug, and therefore proportionally less rigid in structure.However, humans are smaller than whales.Huge animals like whales.In fact, it is very weak, and it can only survive when it is supported by water, that is, when it floats on water.If a whale happens to be washed ashore by a wave, it must be smothered, for the weight of its enormous body crushes its lungs.All large animals are proportionately heavier and therefore more clumsy than small ones.If you reduce the skeleton of a large lizard to the same size as that of a small lizard, you will find that the bones of the large lizard are much weaker than those of the small lizard. The same is true of the structure of planets.It has been said that the structural stability of the straw is a sheer miracle, superior to anything of human design.If a straw were as tall as a gigantic ship's funnel, all parts scaled up in proportion, it might be only a foot (thirty centimeters) in diameter, but it would be able to carry the weight of many tons of grain.This incident is often cited as proof that nature is superior to humans in designing technology.In fact, this example proves nothing.Man can easily duplicate the structure of a straw, more than six feet high, by using a hard steel wire; it can easily bear the weight of a ripe ear of wheat without breaking in the wind.Moreover, if you enlarge an ear of wheat to the size of a tall chimney, it will collapse at once; it cannot bear its own weight.Not even nature can do anything about this fact. The larger the size, the more fragile the texture.Skyscrapers apparently sway in moderate winds.The shaking and vibration of a large suspension bridge like the Golden Gate Bridge in the United States can be felt by anyone who walks across the bridge.Proportionally speaking, such a bridge is actually weaker than a single-plank bridge spanning the creek. The Earth's jelly-like softness explains why the planet is an almost perfect sphere.It is impossible for a soft object of this size to have the corners and sides of a cube.Any protruding part will immediately collapse under its own great weight.In other words, gravitational pulls all the protruding mass together with the rest of the mass into a spherical shape.The earth is a large sphere, almost perfectly round, and because of its shape, all the masses that make up its huge body are packed together very tightly. Our planet is far more fragile than a ball hanging from a Christmas tree.It can't even bear its own weight.Suppose we could put the Earth on the surface of a much larger planet where everything weighs the same as it does on the Earth.We put the earth down as gently as possible, but no matter how careful we are, we cannot prevent its total destruction.As soon as the earth touched the surface of that planet, it flattened where it came into contact with the surface, as a drop of honey touches a saucer.At this time, huge cracks appeared all over the earth, and the cracks became wider and wider, and lava from the earth's core flowed out.The ocean is heated and evaporated, and the steam is surging.The old earth collapsed quickly into a messy, sticky, hissing mess. The pulling force of the sun keeps the earth in its orbit. This force is gentle and constant.The rotation of the earth is easy, lazy.The planet floats forward without hindrance, disturbance or support.May its fragility never be tested!