Posted on by Fraser Cain

Earth Surface Temperature

Sea temperature model

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The average Earth surface temperature is 14° C. That’s 287 kelvin, or 57.2° F.

As you probably realize, that number is just an average. The Earth’s temperature can be much higher or lower than this temperature. In the hottest places of the planet, in the deserts near the equator, the temperature on Earth can get as high as 57.7° C. And then in the coldest place, at the south pole in Antarctica, the temperature can dip down to -89° C.

The reason the average temperature on Earth is so high is because of the atmosphere. This acts like a blanket, trapping infrared radiation close to the planet and warming it up. Without the atmosphere, the temperature on Earth would be more like the Moon, which rises to 116° C in the day, and then dips down to -173° C at night.

We’ve written several articles about the temperature of the planets. Here’s an article about the temperature of all the planets, and here’s an article about the temperature of the Moon.

If you’d like more information on the Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an entire episode of Astronomy Cast all about Earth. Listen here, Episode 51: Earth.

Posted on by Fraser Cain

Earth’s Mass

Blue Marble Earth

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The Earth’s mass is 5.9736 x 1024 kg. That’s a big number, so let’s write it out in full: 5,973,600,000,000,000,000,000,000 kg. You could also say the Earth’s mass is 5.9 sextillion tonnes. Phew, that’s a lot of mass.

That sounds like a lot, and it is, but the Earth has a fraction of the mass of some other objects in the Solar System. The Sun has 333,000 times more mass than the Earth. And Jupiter has 318 times more mass. But then there are some less massive objects too. Mars has only 11% the mass of the Earth.

Because of its high mass for its size, Earth actually has the highest density of all the planets in the Solar System. The density of Earth is 5.52 grams per cubic centimeter. The high density comes from the Earth’s metallic core, which is surrounded by the rocky mantle. Less dense planets, like Jupiter, are just made up of gases like hydrogen.

We’ve written several articles about the mass of planets in the Solar System. Here’s an article about the mass of Mercury, and here’s an article about the mass of the Sun.

If you’d like more information on the Earth mass, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about the Earth. Listen here, Episode 51: Earth.

Posted on 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.

Posted on by Fraser Cain

Earth’s Circumference

Blue marble Earth. Image credit: NASA

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.

Posted on 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

Posted on by Fraser Cain

Destruction of Earth

Planet Killer
Artist's conception of an asteroid hitting Earth.

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Want to destroy the Earth? It’s harder than it sounds. That’s because the Earth is held together by the mutual gravity of 5.97 x 1024 tonnes of rock and metal. In order to blast the Earth apart, you would need to introduce more energy than the gravitational energy holding the whole planet together.

Think about it, if you wanted to bring about the destruction of Earth, you can’t just fly in your orbiting death star and fire a turbo laser at the planet. You might melt a little spot, but it’s not going to cause the planet to detonate like it did in Star Wars. Add up the mutual gravitational attraction of every atom in the Earth, and that’s how much energy you would need coming out of your laser. A laser powerful enough could vaporize the rock and metal and let it escape out into space. Keep that laser firing for billions of years and it should do the trick.

Another possibility would be to strike the Earth with an asteroid large enough to smash the planet. We’ve been hit by millions of asteroids in the past, and one was even thought to have formed the Moon. It would take an object the size of Mars slamming into Earth at more than 11 km/s to actually shatter the planet.

Instead of burning it, or smashing it, you could change the Earth’s orbit into a downward spiral into the Sun. After a few million years the planet would be burned up and destroyed by the Sun. Problem solved. In order to actually shift the Earth’s orbit, you would need to move a heavy asteroid so that it gently nudges the Earth into a spiraling orbit.

Of course, you could just bring an equivalent amount of antimatter, and let the Earth and anti-Earth collide together. The entire Earth would be annihilated in a heartbeat, leaving a flash of energy. Earth destroyed, problem solved.

But in the end, the Earth will likely be destroyed when it’s swallowed up by the Sun in about 7 billion years. When the Sun runs out of fuel, it will expand in size, becoming a red giant star. Astronomers agree it will swallow up Mercury and Venus, but they aren’t sure if it will get so large that it reaches the Earth. But whatever happens, the surface of the Earth will be scorched.

If that doesn’t completely destroy the Earth, you’ll need to wait trillions of years for the planet to get sucked into some black hole. And if that never happens, it might take 10100 years for the atoms that make up the Earth to decay into pure energy.

Then, the destruction of Earth will be complete.

This is a just a taste of the monumental amount of work it would take to bring about the destruction of Earth. Perhaps the best article every written on the subject is over here at Things of Interest.

You should also read Phil Plait’s book, Death from the Skies, which looks at all the different ways the Universe is trying to kill us.

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 a two-part episode of Astronomy Cast about the End of Everything (including the Earth). Here’s part 1, and here’s part 2.

Reference:
NASA

Posted on by Fraser Cain

Barcena Volcano

Barcena

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Barcena is a volcano located on the island of San Benedicto, the third largest island of the Revillagigedo Islands. The whole island is only about 4.8 km by 2.4 km and Barcena takes up a good chunk of the southern end. Barcena rises to an elevation of 332 meters, forming a volcanic crater.

There has only been on eruption from Barcena in recorded history, but it was a big one. On August 1, 1952, Barcena had a severe Vulcanian eruption measuring 3 on the Volcanic Explosivity Index. It released huge pyroclastic flows that rolled over the entire island, covering it in ash and pumice to a depth of 3 meters. Within less than 2 weeks, it had created a new volcanic cone more than 300 meters high. A second series of eruptions started up later in the year, releasing magma that broke out of the cone and flowed into the ocean. By late 1953, the volcano went dormant again.

The eruption wiped out all the plants and wildlife on the island, making the San Benedicto Rock Wren extinct. Within a few years the plants and wildlife made a return, although the island still looks barren.

We have written many article about volcanoes for Universe Today. Here’s an article about Tacana, a tall stratovolcano that straddles the border between Mexico and Guatemala. And here’s an article about Paricutin, a volcano that suddenly appeared in a farmer’s cornfield.

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.

Posted on by Fraser Cain

Circumference of the Earth

The circumference of the Earth in kilometers is 40,075 km, and the circumference of the Earth in miles is 24,901. In other words, if you could drive your car around the equator of the Earth (yes, even over the oceans), you’d put on an extra 40,075 km on the odometer. It would take you almost 17 days driving at 100 km/hour, 24 hours a day to complete that journey.

If you like, you can calculate the Earth’s circumference yourself. The formula for calculating the circumference of a sphere is 2 x pi x radius. So, the radius of the Earth is 6371 km. Plug that into the formula, and you get 2 x 3.1415 x 6378.1 = 40,074. It would be more accurate if you use more digits for pi.

You might be interested to know that the circumference of the Earth is different depending on how you measure it. If you measure the circumference around the Earth’s equator, you get the 40,075 km figure I mentioned up to. But if you measure it from pole to pole, you get 40,007 km. This is because the Earth isn’t a perfect sphere; it bulges around the equator because it’s rotating on its axis. The Earth is a flattened sphere, and so the distance around the equator is further than the circumference around the poles.

Want some comparison? The circumference of the Moon is 10,921 km, and the circumference of Jupiter is 500,000 km.

Here are a bunch of measurements for you:
Circumference of the Earth in kilometers: 40,075 km
Circumference of the Earth in meters: 40,075,000 meters
Circumference of the Earth in centimeters: 4,007,500,000 centimeters

Circumference of the Earth in miles: 24,901 miles
Circumference of the Earth in feet: 131,477,280 feet
Circumference of the Earth in inches: 1,577,727,360 inches

We have written many articles about Earth for Universe Today. Here are some photos of the Earth and Moon together, and here are the 10 most impressive impact craters on Earth.

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.

Reference:
NASA Solar System Exploration: Earth Facts and Figures

Posted on by Fraser Cain

Albedo of the Earth

The albedo of the Earth is 0.367.

That’s the simple answer, now here’s the more complex one. Astronomers use the term “albedo” to define the amount of light that an object in the Solar System reflects. For example, if a planet was perfectly shiny, it would have an albedo of 1.00; it would reflect 100% of the light that hit it. If a planet was perfectly dark, it would have an albedo of 0, and so it would reflect 0% of the light that struck it.

The object with the highest albedo in the Solar System is Saturn’s moon Enceladus, with an albedo of 99%. On the other hand, asteroids can have albedos as low as 4%. The Earth’s moon has an albedo of about 7%. Can you imagine if we had Enceladus for a moon? Now that would be bright.

The albedo of the Earth is very important because it helps define the temperature of the planet. Fresh snow has an albedo of 90%, while the ocean has a very low albedo; land areas range from 0.1 to 0.4.

NASA’s Terra and Aqua satellites are constantly measuring the albedo of the Earth with their MODIS instruments, to help detect any evidence that the albedo is changing over time.

We have written many articles about the Earth for Universe Today. Here’s an article about how scientists track Earthshine on the Moon. And here’s a more detailed article about the albedo of the Moon.

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.