Earth Archives

October 6, 2009December 24, 2015 by Fraser Cain

Earth’s Layers For Kids

My son recently came back from a science day camp with one of the coolest things. It was a model of the Earth that he had created out of modeling clay. It showed the internal structure of the Earth, and because he built it, he was able to remember all of the layers of the Earth. Very cool. So here’s a good way to learn the Earth layers for kids.

To make your own, you need some modeling clay of different colors. You start by making a ball about 1.2 cm across. This represents the Earth’s inner core. Then you make a second ball about 3 cm across. This ball represents the Earth’s outer core. Then you make a third ball about 6 cm across. This ball represents the Earth’s mantle. And finally, you make some flattened pieces of clay that will be the Earth’s crust. To make it extra realistic, make some pieces blue and others green.

Take inner core and surround it with the outer core, and then surround that by the mantle. Cover the entire mantle with a thin layer of blue, and then put on some green continents on top of the blue.

If you’ve been really careful, you should be able to take a sharp knife and slice your Earth ball in half. You should be able to see the Earth’s layers inside, just like you’d see the real Earth’s layers. And you can see that the mantle is thicker underneath the Earth’s continents than it is under the oceans.

Here’s a link with more information from Purdue University so you can do the experiment yourself.

If you’re interested in teaching your children Earth science, here’s lots of information about volcanoes for kids.

We have also recorded a whole episode of Astronomy Cast just about Earth. Listen here, Episode 51: Earth.

October 6, 2009December 24, 2015 by Fraser Cain

How Big is Earth?

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Here’s a question: how big is Earth? Let’s take a look at how big our planet is.

First, the equatorial diameter of Earth is 12,756 km. In other words, if you dug a tunnel on the equator that went straight down and went right through the center of the Earth, it would be about 12,756 km long. Just for comparison, that’s about 1.9 times the diameter of Mars. And only .09% the diameter of Jupiter.

The volume of Earth is 1.08 x 10¹² km³. Written another way, that’s 1.08 trillion cubic kilometers of rock and metal. Again, it’s about 6.6 times more volume than Mars.

The surface area of Earth is 510,072,000 square kilometers. Of that, 29.2% is covered by land and 70.8% is covered by water. Just for comparison, that’s 3.5 times as much surface area as Mars.

The mass of Earth is 5.97 x 10²⁴ kg. Here that is written out: 5,970,000,000,000,000,000,000,000 kg. Yeah, that’s a really big number. And yet, it’s only 0.3% the mass of Jupiter (and Jupiter is mostly lightweight hydrogen).

We have written many articles about Earth for Universe Today. Here’s an article about how fast Earth rotates, and here’s an article about Earth’s magnetic field.

You can learn more about Earth from NASA’s Earth Observatory, as well as NASA’s Solar System Exploration Guide.

We have also recorded an entire episode of Astronomy Cast that’s just about Earth. Listen here, Episode 51: Earth.

September 24, 2009December 24, 2015 by Fraser Cain

Tsunami Pictures

Tsunamis are some of the most devastating natural disasters. The recent Boxing Day Tsunami was generated by an enormous earthquake off the coast of Indonesia on December 26, 2004. Coastlines in Asia were inundated with enormous tsunami surges, killing more than 200,000 people.

Here are some Tsunami pictures capture by satellite that show before and after images of the regions affected by the tsunami.

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This photograph shows the devastation that happened in Sri Lanka on December 26th. This picture was taken by the DigitalGlobe Quickbird satellite, and shows how the whole coastline was inundated with water.

Perhaps the most devastation from the tsunami occurred in Indonesia. This is an image of the town of Lhoknga, Indonesia. It was completely wiped off the map by the tsunami, except for the white mosque in the center of town.

This photograph, captured by NASA’s Terra satellite shows how the whole northwest coast of the island of Sumatra was hit hard by the tsunami. It looks like the vegetation was just scraped back from the edge of the island.

We have written many articles about the devastation from the 2004 tsunami. Here’s an article about how GPS could be used for a tsunami warning system.

You can get many more tsunami pictures from NASA from their Earth observation page.

September 23, 2009December 24, 2015 by Fraser Cain

Pictures of Rivers

Here are some cool pictures of rivers taken by various spacecraft.

Here’s a picture of the Mississippi river delta. The image was captured by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard NASA’s Terra satellite.

This is an image of flooding on the Betsiboka River in Madagascar. The flooding was created by Tropical Storm Eric, which swept through the region in early 2009. This photograph was taken by astronauts on board the International Space Station.

People rely on the Colorado River so much that very little of it actually reaches the ocean. Instead, almost all of the water that flows through the river is used for irrigation along its route.

This is a picture of the river delta for the Ganges. In fact, the Ganges combined with the Brahmaputra River make up the largest river delta in the world. The rivers flood from snow melt in the nearby Himalayas.

This is a picture of the Niger River. It was captured by the ASTER instrument on board NASA’s Terra Earth Observation satellite.

We have written many articles with pictures of rivers for Universe Today. Here’s an article about flooding in the Red River, and here’s an image of the Yangtze River from space.

We have also recorded an episode of Astronomy Cast all about the Earth. Listen to it here, Episode 51: Earth.

September 22, 2009December 24, 2015 by Jean Tate

Abiogenesis

What are Fossils — Fossil stromatolite, Barberton Mountains South Africa (2.5 billion years old)

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How did life on Earth arise? Scientific efforts to answer that question are called abiogenesis. More formally, abiogenesis is a theory, or set of theories, concerning how life on Earth began (but excluding panspermia).

Note that while abiogenesis and evolution are related, they are distinct (evolution says nothing about how life began; abiogenesis says nothing about how life evolves).

Intensive study of the Earth’s rocks has turned up lots and lots of evidence that some kinds of prokaryotes lived happily on Earth about 3.5 billion years ago (and there’re also pointers to the existence of life on Earth in the oldest rocks). So, if life arose on Earth, it did so from the chemicals in the water, air, and rocks of the early Earth … and in no more than a few hundred million years.

Because there are no sedimentary rocks older than about 3.7 billion years (and no metamorphic ones older than about 3.9 billion years), and because the oldest such rocks already contain evidence that there was life on Earth then, testing abiogenesis theories must be done by means other than geological.

There is a long history of attempts to create various organic molecules – such as amino acids – from simple precursors such as carbon dioxide, ammonia, and water, in conditions which simulate those of the early Earth. Those of Miller and Urey, in 1953, are the most famous (and the first).

It turns out that it’s pretty easy to form many kinds of organic molecules, in a wide range of environments … so the focus of research today is on how life could arise from any particular brew. And the hard part is how reliable self-replication get going (if you can make some sort of primitive cell in a test tube, it isn’t a form of life if it can’t reproduce itself!). So far, it seems that RNA and DNA cannot have been involved (too hard to form and stay stable), but several simpler kinds of molecules may work.

Well, that’s one hard part; another is how can a stable bag of chemicals form? (There have been some exciting recent discoveries which may help answer at least part of this question).

A different approach – than reproduction – to finding the key to how life got started involves asking how metabolism arose; how can a bag of chemicals take in ‘food’, process it (to supply energy to all the other chemical processes going on in the bag), and get rid of the waste?

The TalkOrigins website has a summary of abiogenesis, though it is now somewhat dated (much has happened in just the last three years)!

Abiogenesis in its strict sense (origin of life on Earth) is a bit off the track for Universe Today; however, conditions under which life might spontaneously arise, on other planets (etc) is not. Some Universe Today stories on this are Sub-surface Oceans In Comets Suggest Possible Origin of Life, Add Heat, Then Tectonics: Narrowing the Hunt for Life in Space, and Has Liquid Water Been Detected on Mars?

September 22, 2009December 24, 2015 by Fraser Cain

Earth’s Circumference

The Earth’s circumference – the distance around the equator – is 40,075 kilometers around. That’s sounded nice and simple, but the question is actually more complicated than that. The circumference changes depending on where you measure it. The Earth’s meridional circumference is 40,008 km, and its average circumference is 40,041 km.

Why are there different numbers for the Earth’s circumference? It happens because the Earth is spinning. Think about what happens when you spin around holding a ball on a string. Your rotation creates a force that holds the ball out on the end of the string. And if the string broke, the ball would fly away. Even though the Earth is a solid ball of rock and metal, its rotation causes it to flatten out slightly, bulging at the equator.

That bulge isn’t very much, but when you subtract the meridional circumference (the equator when you pass through both poles), and the equatorial circumference, you see that it’s a difference of 67 km. In other words, if you drove your car around the equator of the Earth, you would drive an extra 67 km than you would if you drove from pole to pole to pole.

And that’s why the average circumference of Earth is 40,041 km. Which answer is correct? It depends on how accurate you want to be with your calculation.

We have written many articles about the Earth for Universe Today. Here’s an article about how fast the Earth rotates, and here’s an article about how round the Earth is.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

September 19, 2009December 24, 2015 by Abby Cessna

Magnetic North Pole

The movement of Earth's north magnetic pole across the Canadian arctic, 1831--2001 (Geological Survey of Canada)

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The Earth has a magnetic field, known as the magnetosphere, that protects our planet from the particles of the solar winds. One point of that field is known as the Magnetic North Pole. The Magnetic North Pole is not the geographic North Pole; it is actually hundreds of miles south of the geographic North Pole and north of Canada.

Hundreds of years ago, European navigators believed that the needles of compasses were attracted to some “magnetic mountain” or “island” thought to be located in the far north. Some also believed that the needles could be attracted to the Pole Star, which is part of the Ursa Minor constellation and has long been used in navigation. One English philosopher, William Gilbert, proposed that the Earth acts like a giant magnet; he also was the first person to state that the Earth’s magnetic field points vertically downward at the Magnetic North Pole. It took hundreds of years before scientists came to properly understand our planet’s magnetic field, although this is known to be correct now.

All magnets have two poles, like the “plus” and “minus” signs found on batteries. Instead of these locations being named plus and minus though, they were named the North and South Magnetic Poles. It is toward the Magnetic North Pole that your compass points not the geographic North Pole, which makes sense considering it utilizes magnets to determine direction. At the Magnetic North Pole, the magnetic fields points down vertically; in other words it has a 90° “dip” toward the Earth’s surface. The counterpart of the Magnetic North Pole is the Magnetic South Pole. Because the Earth’s magnetic field is not perfectly symmetrical, the magnetic fields are not antipodal. That means that if you draw a straight line between them, it does not pass through the Earth’s center. It is off by approximately 530 km. The North and South Magnetic Poles are also known as Magnetic Dip Poles because they “dip” at a 90° angle towards the Earth.

The Magnetic North Pole continues to move around. According to the Geological Survey of Canada, which routinely studies the Magnetic North Pole, the pole moves as much as 40 km per year. It also moves daily. Every day, the Magnetic North Pole has an elliptical movement of approximately 80 km from the average point of its center. That means when you are using a compass, you have to be aware of the difference between magnetic north and geographic north.

Universe Today has articles on Earth’s magnetic field and modeling the Earth’s magnetic field.

For more information, check out the Magnetic North Pole and geomagnetism.

Astronomy Cast has an episode on Earth.

References:
Earth’s Inconstant Magnetic Field
Earth’s Magnetic Field and its Changes in Time

September 16, 2009December 24, 2015 by Fraser Cain

Exosphere

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The Earth’s atmosphere is broken up into several distinct layers. We live down in the troposphere, where the atmosphere is thickest. Above that is the stratosphere, then there’s the mesosphere, thermosphere and finally the exosphere. The top of the exosphere marks the line between the Earth’s atmosphere and interplanetary space.

The exosphere is the outermost layer of the Earth’s atmosphere. It starts at an altitude of about 500 km and goes out to about 10,000 km. Within this region particles of atmosphere can travel for hundreds of kilometers in a ballistic trajectory before bumping into any other particles of the atmosphere. Particles escape out of the exosphere into deep space.

The lower boundary of the exosphere, where it interacts with the thermosphere is called the thermopause. It starts at an altitude of about 250-500 km, but its height depends on the amount of solar activity. Below the thermopause, particles of the atmosphere have atomic collisions, like what you might find in a balloon. But above the thermopause, this switches over to purely ballistic collisions.

The theoretical top boundary of the exosphere is 190,000 km (half way to the Moon). This is the point at which the solar radiation coming from the Sun overcomes the Earth’s gravitational pull on the atmospheric particles. This has been detected to about 100,000 km from the surface of the Earth. Most scientists consider 10,000 km to be the official boundary between the Earth’s atmosphere and interplanetary space.

We have written several articles about the Earth’s atmosphere for Universe Today. Here’s an article about an evaporating extrasolar planet, and this article explains how far away space is.

You can learn more about the layers of the atmosphere, including the exosphere from this page at NASA.

We have recorded a whole episode of Astronomy Cast talking about the Earth’s (and it’s atmosphere). Check it out here, Episode 51: Earth.

September 15, 2009December 24, 2015 by Fraser Cain

Satellite Map of the World

There’s no better way to appreciate the planet you live on than to have a great big picture of it on your wall. Here are some ways you can get your hands on a satellite map of the world.

If you’ve got a nice printer and you’d like to save yourself some money, why not download a satellite map of the world for free from NASA. You can get free satellite images from the NASA Earth Observatory.

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Each month NASA releases a new composite satellite image of the entire planet. This lets you track changes from month to month. You can view the full images on this page.

You can also get a free satellite map of the world captured at night. This photo shows whole planet Earth, but now you’re seeing it at night. The bright spots are cities and populated areas. It’s easy to see the differences between 1st world countries and more developing nations.

If you want to just buy a poster that you can put on your wall, you can find a bunch of satellite world maps from Amazon.com. Here’s a link to buy the Earth at night poster. And here’s an image of the whole Earth by day.

September 11, 2009December 24, 2015 by Fraser Cain

Albedo Effect

Stains on the ice visible on this satellite image. Credit: British Antarctic Survey

Astronomers define the reflectivity of an object in space using a term called albedo. This is the amount of electromagnetic radiation that reflects away, compared to the amount that gets absorbed. A perfectly reflective surface would get an albedo score of 1, while a completely dark object would have an albedo of 0. Of course, it’s not that black and white in nature, and all objects have an albedo score that ranges between 0 and 1.

Here on Earth, the albedo effect has a significant impact on our climate. The lower the albedo, the more radiation from the Sun that gets absorbed by the planet, and temperatures will rise. If the albedo is higher, and the Earth is more reflective, more of the radiation is returned to space, and the planet cools.

An example of this albedo effect is the snow temperature feedback. When you have a snow covered area, it reflects a lot of radiation. This is why you can get terrible sunburns when you’re skiing. But then when the snow covered area warms and melts, the albedo goes down. More sunlight is absorbed in the area and the temperatures increase. Climate scientists are concerned that global warming will cause the polar ice caps to melt. With these melting caps, dark ocean water will absorb more sunlight, and contribute even more to global warming.

Earth observation satellites are constantly measuring the Earth’s albedo using a suite of sensors, and the reflectivity of the planet can actually be measured through Earthshine – light from the Earth that reflects off the Moon.

Different parts of the Earth contribute to our planet’s overall albedo in different amounts. Trees are dark and have a low albedo, so removing trees might actually increase the albedo of an area; especially regions typically covered in snow during the winter.

Clouds can reflect sunlight, but they can also trap heat warming up the planet. At any time, about half the Earth is covered by clouds so their effect is significant.

Needless to say, the albedo effect is one of the most complicated factors in climate science, and scientists are working hard to develop better models to estimate its impact in the future.

We have written many articles about the albedo effect for Universe Today. Here’s an article discussing the albedo of the Earth, and how decreasing Earthshine could be tied to global warming.

There are some great resources out on the Internet as well. Check out this article from Scientific American Frontiers, and some cool photos of different colors of ice.

We have recorded a whole episode of Astronomy Cast just about the Earth. Listen to it here, Episode 51: Earth.

Reference:
Encyclopedia of Earth