Where do Hurricanes Occur?

View of Hurricane Ike From Space Station
View of Hurricane Ike From Space Station

What is a hurricane? Well, a hurricane is a tropical cyclone that occurs in the North Atlantic Ocean or the Northeast Pacific Ocean and remains east of the International Dateline. Tropical cyclones are characterized by a large low pressure center and numerous thunderstorms. These produce strong winds and heavy rain. These cyclones feed on heat released when moist air rises causing condensation of the water vapor that is contained in the moist air. These storms are fueled by a different heat mechanism than other cyclonic windstorms(nor’easters, polar lows, and European windstorms). They are classified as a warm core storm system.

All tropical cyclones are areas of low atmospheric pressure. As a matter of fact, the pressures recorded at the center of tropical cyclones are among the lowest that occur at sea level. A hurricane is characterized and driven by the release of large amounts of latent heat of condensation(water vapor condenses as it moves upward). This heat is distributed vertically around the center of the storm, so, except at the surface of water, it is warmer inside the cyclone than it is outside. At the center of the hurricane is an area of sinking air. If this area is strong enough, it can develop into a large eye. Weather in the eye is normally calm and free of clouds, but the surface of the sea may be tossing violently. The eye is normally circular in shape, and may range in size from 3 km to 370 km in diameter.

While a tropical cyclone’s primary energy source is the release of the heat of condensation, solar heating is the initial source of that evaporation. An initial warm core system(an organized thunderstorm complex) is necessary for the formation of a tropical cyclone, but a large flux of energy is needed to lower atmospheric pressure. The influx of warmth and moisture from the underlying ocean surface is critical for tropical cyclone strengthening and most of it comes from the lower 1 km of the atmosphere. Condensation leads to higher wind speeds. These faster winds and the lower pressure associated with them cause an increase in surface evaporation and more condensation. This positive feedback system continues and feeds the hurricane until the conditions for hurricane formation are gone. The rotation of Earth causes the system to spin,(the Coriolis effect) which gives it a cyclonic appearance and affects its trajectory.
Tropical cyclones are distinguished by the deep convection that fuels them. Since convection is strongest in the tropics it defines the initial domain of the tropical cyclone. To continue to feed itself a tropical cyclone must remain over warm water. When a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly. The passage of a tropical cyclone over the ocean can cause the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. Scientists at the National Center for Atmospheric Research in the US estimate that a tropical cyclone releases heat energy equal to 70 times the world energy consumption, 200 times the worldwide electrical generating capacity, or the same as exploding a 10 megaton nuclear bomb every 20 minutes.
Well, there you have the answer to what is a hurricane. It is a tropical nightmare, but if humans could somehow harness that energy we would never need fossil fuels again.

We have written many articles about hurricanes for Universe Today. Here’s an article about human influences generating more hurricanes, and here’s a NASA video of Hurricane Bill.

If you’d like more info on hurricanes, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

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

The New Blue Marble

Permian Extinction
A new NASA image of Earth, by Robert Simmon and Marit Jentoft-Nilsen, based on MODIS data.

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Despite recent news of potential habitable exoplanets and amazing images of Mars and the Saturn system returned from visiting spacecraft, the ol’ home planet is still about the most gorgeous-looking planetary body out there. We first saw it as a whole “blue marble” when the Apollo astronauts sent back pictures while circling the Moon, and it has been said that the original “Blue Marble” image taken by the Apollo 17 crew has been one of the most viewed and most influential images ever. But truth be told, that “Blue Marble” really wasn’t all that blue (see the original below). However, this new look at the home world shows how prevalent water really is. This composite image is based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.

It sure is pretty.

According to the NASA Earth Observatory website, Earth’s water content is about 1.39 billion cubic kilometers (331 million cubic miles), with the bulk of it, about 96.5%, being in the global oceans. As for the rest, approximately 1.7% is stored in the polar icecaps, glaciers, and permanent snow, and another 1.7% is stored in groundwater, lakes, rivers, streams, and soil. Only a thousandth of 1% of the water on Earth exists as water vapor in the atmosphere.

Here’s the original “Blue Marble,” the view of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is Madagascar. The Asian mainland is on the horizon toward the northeast.

The original 'Blue Marble' taken by Apollo 17. Credit: NASA

For larger versions of the top image, see NASA Earth Observatory’s website, and this link for the Apollo 17 version, NASA also has versions of the Blue Marble compiled from various satellites in 2001 and 2002.

Watch the Effects of Earthquakes Just Hours After They Occur

Princeton University has developed software that can produce realistic “movies” of earthquakes based on complex computer simulations, and these visualizations will be available on the internet within hours of a disastrous upheaval. For example, this video of a 5.7 scale Earthquake off the coast of Peru occurred yesterday, September 22, 2010. “In our view, this could truly change seismic science,” said Princeton’s Jeroen Tromp, a professor of geosciences and applied and computational mathematics, who led the effort. “The better we understand what happens during earthquakes, the better prepared we can be. In addition, advances in understanding seismic waves can aid basic science efforts, helping us understand the underlying physics at work in the Earth’s interior. These visualizations, we believe, will add greatly to the research effort.”

Continue reading “Watch the Effects of Earthquakes Just Hours After They Occur”

What Is Water Made Of

Water
Water

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The answer to ‘what is water made of’ is as easy as you want it to be. Do you want to just do some superficial research or do you want to look a little deeper? Superficially, pure, distilled water is composed of 2 hydrogen atoms and 1 oxygen atom. If the sample of water is not ‘pure’, the composition of the sample can be different.

Salt water obviously contains salt, but it can contain many other trace elements. Fresh water from different sources will contain different elements and minerals. These come from the rocks the water washes over and the pollutants from farms and industry. The water that you drink will contain several additives used for purification plus the fluoride that is added for our health. Rain water will have any number of pollutants that have accumulated in the atmosphere.

At high temperatures and pressures, like those in the interior of giant planets, scientists think that water exists as ionic water in which the molecules break down into a soup of hydrogen and oxygen ions, and at even higher pressures as superionic water in which the oxygen crystallizes but the hydrogen ions float around freely within the oxygen lattice.

There are many interesting facts about water. Water is a tasteless, odorless liquid. The natural color of water and ice is slightly blue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas. Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, water carries a slight negative charge. As a result, water has a electrical dipole moment. Water can form a large number of intermolecular hydrogen bonds(four). These factors lead to to water’s high surface tension and capillary forces. Water is often referred to as the universal solvent. All major cellular components are dissolved in water. Water is at its maximum density at 3.98°C. Oddly, it becomes less dense when it is cooled down to its solid form, ice. It expands to occupy 9% greater volume in this solid state, which accounts for the fact of ice floating on liquid water.

Water covers the majority of our planet and can be found in one form or another throughout the known universe. No matter where you are on Earth, water affects you in some way each day.

We have written many articles about water for Universe Today. Here’s an article about the density of water, and here’s an article about the water on Earth.

If you’d like more info on Water, check out NASA’s Water, Water, Everywhere!. And here’s a link to NASA’s Earth Observatory.

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

Source: Wikipedia

What is Carbon Dioxide?

Carbon cycle diagram.

CO2 is more than just the stuff that comes out of smokestacks, tailpipes, cigarettes and campfires. It is also a crucial element here on planet Earth, essential to life and its processes. It is used by plants to make sugars during photosynthesis. It is emitted by all animals, as well as some plants, fungi and microorganisms, during respiration. It is used by any organism that relies either directly or indirectly on plants for food; hence, it is a major component of the Carbon Cycle. It is also a major greenhouse gas, hence why it is so closely associated with Climate Change.

Joseph Black, a Scottish chemist and physician, was the first to identify carbon dioxide in the 1750s. He did so by heating calcium carbonate (limestone) with heat and acids, the result of which was the release of a gas that was denser than normal air and did not support flame or animal life. He also observed that it could be injected into calcium hydroxide (a liquid solution of lime) to produce Calcium Carbonate. Then, in 1772, another chemist named Joseph Priestley came up with of combining CO2 and water, thus inventing soda water. He was also intrinsic in coming up with the concept of the Carbon Cycle.

Since that time, our understanding of CO2 and its importance as both a greenhouse gas and an integral part of the Carbon Cycle has grown exponentially. For example, we’ve come to understand that atmospheric concentrations of CO2 fluctuate slightly with the change of the seasons, driven primarily by seasonal plant growth in the Northern Hemisphere. Concentrations of carbon dioxide fall during the northern spring and summer as plants consume the gas, and rise during the northern autumn and winter as plants go dormant, die and decay.

Traditionally, atmospheric CO2 levels were dependent on the respirations of animals, plants and microorganisms (as well as natural phenomena like volcanoes, geothermal processes, and forest fires). However, human activity has since come to be the major mitigating factor. The use of fossil fuels has been the major producer of CO2 since the Industrial Revolution. By relying increasingly on fossil fuels for transportation, heating, and manufacturing, we are threatening to offset the natural balance of CO2 in the atmosphere, water and soil, which in turn is having observable and escalating consequences for our environment. As is the process of deforestation which deprives the Earth of one it’s most important CO2 consumers and another important link in the Carbon Cycle.

As of April 2010, CO2 in the Earth’s atmosphere is at a concentration of 391 parts per million (ppm) by volume. For an illustrated breakdown of CO2 emissions per capita per country, click here.

We have written many articles about Carbon Dioxide for Universe Today. Here’s an article about the Carbon Cycle Diagram, and here’s an article about Greenhouse Effect.

If you’d like more info on Carbon Dioxide, check out NASA’s The Global Climate Change. And here’s a link to The Carbon Cycle.

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

Sources:
http://en.wikipedia.org/wiki/Carbon_dioxide
http://en.wikipedia.org/wiki/Carbon_cycle
http://www.eoearth.org/article/carbon_dioxide
http://cdiac.ornl.gov/
http://www.epa.gov/climatechange/emission/co2.html
http://www.lenntech.com/carbon-dioxide.htm
http://www.davidsuzuki.org/issues/climate-change/science/climate-change-basics/climate-change-101-1/

What Color is the Sky

Space Travel
Atlantis Breaks Through the Clouds

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If you are a parent or are old enough to babysit younger relatives there is one question children ask that stumps most adults. It’s what color is the sky or why is the sky blue. This article will tell you why and do it in as simple a way as possible so that the next time a kids ask the question you have a good answer.

To understand why the sky is blue you need to remember how color works. Color is largely caused by how well an object absorbs the light spectrum. When you see a blue sky you only see blue because all the other colors were absorbed in the air. Any object with color works that way. For example a red ball is read because all the colors of light are absorbed by the ball except for red. This reflected light is what gives the object color.

This is what happens with the sky. The atmosphere is denser than we imagine and the different gases give the atmosphere unique properties in how it absorbs, diffuses, and reflects light. When sunlight passes through our atmosphere a portion of it is scattered and absorbed. The remainder either reaches the surface or is reflected back. The portion that makes it to us observers is 75 percent.

This process is called diffused sky radiation. So to review, we color because objects due to texture of dyes and surfaces absorb all light wavelengths and reflect back one or more. The reason we see the sky as blue is because the molecules in the air scatter the light absorbing most wavelengths of light except for blue.

In addition to this the sky is gray and overcast because of the water droplets in the atmosphere in the forms of clouds and humidity. water refracts light equally unlike air molecules in the atmosphere. This means we get the entirety of white light only it is dimmer just like when you shine a light through a white sheet.

The fact we see a blue sky is good thing because its shows that are atmosphere is at work shielding us from the full energy of the sun’s rays. While the sun is the largest source of energy to our planet, a lot of its high energy radiation that is deadly for living things. Our atmosphere plays it part by shielding us from that. So when you see a blue sky with your kid you can tell them it means the sky is acting like a huge shade blocking out the bad parts of the sun.

We have written many articles about the earth’s sky for Universe Today. Here’s an article about why the sky is blue, and here’s an article about how to find Venus in the sky.

If you’d like more info on the earth’s sky, check out an article about Strange Clouds. And here’s a link to NASA Space Place Article on Blue Sky.

We’ve also recorded an episode of Astronomy Cast all about Sky Survey. Listen here, Episode 118: Sky Surveys.

What Is The Largest Island In The World

Greenland. Image credit: NASA
Greenland. Image credit: NASA

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If you were asked what is the largest island in the world, what would you say? Australia maybe? Greenland is the worlds largest island. While Australia is an island, it is considered a continent. Greenland has an area of 2,166,086 square km, but a meager population of 56,452. The populations is over 85% Inuit. The remaining inhabitants are mainly Danish. The average annual temperature of Greenland varies between -9 to 7 °C.

Greenland is an autonomous country within the Kingdom of Denmark. Greenland is a group of islands and Greenland is the name of the largest, most populated one. Greenland has been inhabited on and off since 2500 BC. Denmark established rule in the 18th century. In 1979 Denmark granted home rule, in a relationship known as the Commonwealth of the Realm and in 2008 Greenland voted to transfer more powers to the local government. The Danish royal government is only in charge of foreign affairs, security, financial policy, and providing a subsidy to each citizen.

Greenland is bordered by the Atlantic Ocean to the southeast, the Greenland Sea to the east, the Artic Ocean to the north, and Baffin Bay to the west. The nearest countries to Greenland are Iceland to the east and Canada to the west. The country also contains the world’s largest national park. Scientists have thought for decades that the ice sheet covering the country may actually conceal three separate island land masses that have been bridged by glaciers over the last geologic cooling period.

The Greenland ice sheet covers 1,755,637 square km. It has a volume of 2,850,000 cubic km. Gunnbjorn Fjeld is the highest point on Greenland at 3,700 m. The majority of Greenland is less than 1,500 m in elevation. The weight of the ice sheet has formed a basin that is more than 300 m below sea level.

Between 1989 and 1993, climate researchers drilled into the summit of Greenland’s ice sheet, obtaining a pair of 3 km ice cores. Analysis of the layering and chemical composition of the cores has provided a revolutionary new record of climate change going back about 100,000 years. It illustrated that the world’s weather and temperature have often shifted rapidly from one stable state to another. The glaciers of Greenland are also contributing to a rise in the global sea level at a faster rate than was previously believed.

Greenland is fascinating and intimidating at the same time. To live there is a daily struggle against the elements that has forged a tough people.

We have written many articles about Greenland for Universe Today. Here’s an article about the growing ice sheets in Greenland, and here are some images of Greenland from space.

If you’d like more info on Earth’s islands, 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 planet Earth. Listen here, Episode 51: Earth.

Sources:
World Atlas
Geographia

What Is The Largest Continent

Asia Image Credit: NASA's Blue Marble project
Asia Image Credit: NASA's Blue Marble project

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There are a few different ways to answer ‘what is the largest continent’. The first is by area and another is by population. By area, Asia is the largest continent at 44,391,162 square km. It is also the largest by population with more than 4 billion people.

There is quite a bit of debate as to how many continents there are. Some areas of the world combine Asia and Europe into one continent called Eurasia. In that case, the continent of Eurasia would be the biggest continent in both area and population.

The debate as to how many continents there are is based in the basic, yet confusing definition of what a continent is. A continent is understood to be large, continuous, discrete mass of land, ideally separated by an expanse of water. Many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated by water. The criteria of being large is used arbitrarily. Greenland has an area of 2,166,086 square km and is considered an island. Australia has an area of 7,617,930 square km, but it is called a continent. The distinct landmass separated by water criteria is sometimes ignored in the case of Europe and Asia. All of the criteria are a consensus, not a rule, so some countries teach a different number of continents.

Whether you have been taught that there are 6 or 7 continents, you need to know that here have been changing numbers of continents since the formation of the Earth. There have been anywhere from 1 to 7 continents. As the tectonic plates have shifted, the continents have broken apart and collided together again. The Earth’s tectonic plates are still moving, so it is hard to predict how many continents there will be in 500,000 years, 1 million years, and so forth.

The answer to ‘what is the largest continent’ is pretty cut and dry. If you consider that there are seven continents, then Asia is the largest in area and population. If you combine Europe and Asia into the continent of Eurasia, it is still the largest by area and population.

We have written many articles about Continent for Universe Today. Here’s an article about the number of continents in the Earth, and here’s an article about the Continental Drift Theory.

If you’d like more info on continents, 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 planet Earth. Listen here, Episode 51: Earth.

Source:
Wikipedia

What is an Avalanche?

A powder snow avalanche in the Himalayas near Mount Everest. Credit: Wikipeida Commons/ Ilan Adler

Have you ever noticed how the snow packs on a car windshield after a heavy snowfall? While the temperature is cold, the snow sticks to the surface and doesn’t slide off. After temperatures warm up a little, however, the snow will slide down the front of the windshield, often in small slabs. This is an avalanche on a miniature scale.

On the other hand, a mountain avalanche in North America might release 229,365 cubic meters (300,000 cubic yards) of snow. That’s the equivalent of 20 football fields filled 10 feet deep with snow. However, such large avalanches are often naturally released. They are primarily composed of flowing snow but given their power, they are also capable of carrying rocks, trees, and other forms of debris with them.

In mountainous terrain avalanches are among the most serious objective hazards to life and property, with their destructive capability resulting from their potential to carry an enormous mass of snow rapidly over large distances.

Classification:

Avalanches are classified based on their form and structure, which are also known as “morphological characteristics”. Some of the characteristics include the type of snow involved, the nature of what caused the structural failure, the sliding surface, the propagation mechanism of the failure, the trigger of the avalanche, the slope angle, direction, and elevation.

Loose snow avalanches (far left) and slab avalanches (near center) near Mount Shuksan in the North Cascades mountains. Credit: wikipedia
Loose snow avalanches (far left) and slab avalanches (near center) near Mount Shuksan in the North Cascades mountains. Credit: Thermodynamic/Wikipedia Commons

All avalanches are rated by either their destructive potential or the mass they carry. While this varies depending on the geographical region – – all share certain common characteristics, ranging from small slides (or sluffs) that pose a low risk to massive slides that come that pose a significant risk.

An avalanche has three main parts: the starting zone, the avalanche track, and the runout zone. The starting zone is the most volatile area of a slope, where unstable snow can fracture from the surrounding snowcover and begin to slide. The avalanche track is the path or channel that an avalanche follows as it goes downhill. The runout zone is where the snow and debris finally come to a stop.

Causes:

Several factors may affect the likelihood of an avalanche, including weather, temperature, slope steepness, slope orientation (whether the slope is facing north or south), wind direction, terrain, vegetation, and general snowpack conditions. However, weather remains the most likely factor in triggering an avalanche.

During the day, as temperatures increase in a mountainous region, the likelihood of an avalanche increases. Regardless of the time of year, an avalanches will only occur when the stress on the snow exceeds the strength either within the snow itself or at the contact point where the snow pack meets the ground or the rock surface.

An avalanche east of Revelstoke in 2010 Credit: Canadian Avalanche Center
An avalanche east of the town of Revelstoke, BC, in 2010 Credit: Canadian Avalanche Center

Although avalanches can occur on any slope given the right conditions, in North America certain times of the year and certain locations are naturally more dangerous than others. Wintertime, particularly from December to April, is when most avalanches will occur with the highest number of fatalities occurs in January, February and March, when the snowfall amounts are highest in most mountain areas.

Deaths Caused by Avalanches:

In the United States, 514 avalanche fatalities have been reported in 15 states from 1950 to 1997. In the 2002–2003 season there were 54 recorded incidents in North America involving 151 people.

In Canada’s mountainous province of British Columbia, a total of 192 avalanche-related deaths were reported between January 1st, 1996 and March 17th, 2014 – an average of roughly ten deaths per year. During the winter of 2014, avalanche concerns also forced the closure of the Trans-Canada highway on a number of occasions.

Avalanches on Other Planets:

Not too surprisingly, Earth is not the only planet in the Solar System to experience avalanches. Wherever their is mountainous terrain and water ice, which is not uncommon, there is the likelihood that material will come loose and cause a cascading slide to take place.

On February 19th, 2008, NASA’s Mars Reconnaissance Orbiter captured the first ever image of active avalanches taking place the Red Planet. The avalanche occurred near the north pole, where water ice exists in abundance, and was captured by the MRO’s HiRISE (High Resolution Imaging Experiment) camera completely by accident.

Images taken by the MRO's HiRISE camera show at least four Martian avalanches, or debris falls, taking place near the north pole. Credit: NASA/JPL
Images taken by the MRO’s HiRISE camera show at least four Martian avalanches, or debris falls, taking place near the north pole. Credit: NASA/JPL

The images showed material – likely to include fine-grained ice dust and possibly large blocks – detaching from a towering cliff and cascading to the gentler slops below. The occurrence of the avalanches was spectacularly revealed by the accompanying clouds of fine material (visible in the photographs) that continue to settle out of the air.

The largest cloud (shown in the upper images) was about 180 meters (590 feet) across and extended about 190 meters (625 feet) from the base of the steep cliff. Shadows to the lower left of each cloud illustrate further that these are three dimensional features hanging in the air in front of the cliff face, and not markings on the ground.

The photo was unprecedented because it allowed NASA scientists to get a glimpse of a dramatic change on the Martian surface while it was happening. Despite seeing countless pictures that have detailed the planet’s geological features, most appear to have remained unchanged for several million years. It also showed that terrestrial events like avalanches are not confined to planet Earth.

We have written many articles about the avalanche for Universe Today. Here’s an article about the Mars avalanche predicted by geologists, and here’s an article about the volcanic tuff.

If you’d like more info on avalanche, check out NASA Science News: Avalanche on Mars. And here’s a link to the American Avalanche Association Homepage.

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

Sources:

Equator

GOES-8 Satellite Image Captures Earth
GOES-8 Satellite Image Captures Earth

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An equator is an imaginary line that runs around the surface of a planet, perpendicular to the sphere’s axis of rotation. Of course, the one we’re most interested in is the Earth’s equator. Regions north of the equator are called the Northern Hemisphere, and then south of the equator is the Southern Hemisphere.

Here on Earth, the equator has a length of 40,008.6 kilometers, and its latitude is 0°. And if you can stand on the equator, you’ll see the Sun rise in the East and travel overhead through the day, and then set in the West; on the March and September equinox, the rays from the Sun fall straight down. This is also the spot with the quickest sunrise and sunset times, since the Sun moves exactly perpendicular to the horizon, rising straight up, without moving at an angle to the horizon.

Because the Earth is rotating, turning once a day on its axis, the Earth’s equator bulges out further from the center than from the poles. The Earth isn’t a sphere, but it’s actually an oblate spheroid. The equatorial diameter of the Earth is actually 43 kilometers greater than the polar diameter.

Since it’s the region of Earth that receives the most sunlight, the climate near the equator is hot – it’s summer all the time. People who live near the equator will generally distinguish between a long hot dry season and a long hot wet season. Some of the countries with the equator include Gabon, Congo, Uganda, Kenya, Somalia, Indonesia, Ecuador, Columbia, and Brazil.

The equator is the best place to launch a spacecraft on Earth. That’s because the rotational speed of the planet adds to the launch velocity of a rocket. Rockets launched from the equator can launch with less fuel, or carry more mass into orbit with the same amount of fuel. This is why the Guiana Space Centre is located in Kourou, French Guiana. And this is also why the Sea Launch platform travels from Los Angeles down to the equator before launching rockets.

We have written many articles about the Equator for Universe Today. Here’s an article about the temperature of the Earth, and here’s an article about the circumference of the Earth.

If you’d like more info on Equator, check out NASA’s Article about Latitude and Longitude. And here’s a link to NASA’s Earth Observatory.

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

Source: Wikipedia