Tsunami Facts

What is a tsunami?

A tsunami is a series of ocean waves with very long wavelengths (typically hundreds of kilometres) caused by large-scale disturbances of the ocean, such as:

• earthquakes
• landslide
• volcanic eruptions
• explosions
• meteorites

These disturbances can either be from below (e.g. underwater earthquakes with large vertical displacements, submarine landslides) or from above (e.g. meteorite impacts).

Tsunami is a Japanese word with the English translation: "harbour wave". In the past, tsunamis have been referred to as "tidal waves" or "seismic sea waves".

 The term "tidal wave" is misleading; even though a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. (Tides result from the gravitational influences of the moon, sun, and planets.) The term "seismic sea wave" is also misleading. "Seismic" implies an earthquake-related generation mechanism, but a tsunami can also be caused by a non-seismic event, such as a landslide or meteorite impact.

Tsunamis are also often confused with storm surges, even though they are quite different phenomena. A storm surge is a rapid rise in coastal sea-level caused by a significant meteorological event - these are often associated with tropical cyclones.

The physics of a tsunami

Tsunamis can have wavelengths ranging from 10 to 500 km and wave periods of up to an hour. As a result of their long wavelengths, tsunamis act as shallow-water waves. A wave becomes a shallow-water wave when the wavelength is very large compared to the water depth. Shallow-water waves move at a speed, c, that is dependent upon the water depth and is given by the formula:

where g is the acceleration due to gravity (= 9.8 m/s²) and H is the depth of water.

In the deep ocean, the typical water depth is around 4000 m, so a tsunami will therefore travel at around 200 m/s, or more than 700 km/h.

For tsunamis that are generated by underwater earthquakes, the amplitude (i.e wave height) of the tsunami is determined by the amount by which the sea-floor is displaced. Similarly, the wavelength and period of the tsunami are determined by the size and shape of the underwater disturbance.

As well as travelling at high speeds, tsunamis can also travel large distances with limited energy losses. As the tsunami propagates across the ocean, the wave crests can undergo refraction (bending), which is caused by segments of the wave moving at different speeds as the water depth along the wave crest varies.

What happens to a tsunami as it approaches land?

As a tsunami leaves the deep water of the open-ocean and travels into the shallower water near the coast, it transforms. If you read the "The physics of a tsunami" section, you will know that a tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows. The tsunami's energy flux, which is dependent on both its wave speed and wave height, remains nearly constant.

Consequently, as the tsunami's speed diminishes, its height grows. This is called shoaling. Because of this shoaling effect, a tsunami that is unnoticeable at sea, may grow to be several metres or more in height near the coast.

The increase of the tsunami's waveheight as it enters shallow water is given by:

where h_s and h_d are waveheights in shallow and deep water and H_s and H_d are the depths of the shallow and deep water. So a tsunami with a height of 1 m in the open ocean where the water depth is 4000m would have a waveheight of 4 to 5 m in water of depth 10 m.

Just like other water waves, tsunamis begin to lose energy as they rush onshore - part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Depending on whether the first part of the tsunami to reach the shore is a crest or a trough, it may appear as a rapidly rising or falling tide.

Local bathymetry may also cause the tsunami to appear as a series of breaking waves.

Tsunamis have great erosion potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of metres inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a run-up height, of tens of metres.

How are tsunamis measured or observed?

In the deep ocean, a tsunami has a small amplitude (less than 1 metre) but very long wavelength (hundreds of kilometres). This means that the slope, or steepness of the wave is very small, so it is practically undetectable to the human eye. However, there are ocean observing instruments that are able to detect tsunamis.

Tide Gauges

Tide gauges measure the height of the sea-surface and are primarily used for measuring tide levels. Most of the tide gauges operated by the Bureau of Meteorology's National Tidal Centre are SEAFRAME stations (Sea Level Fine Resolution Acoustic Measuring Equipment). These consist of an acoustic sensor connected to a vertical tube open at the lower end which is in the water.

The acoustic sensor emits a sound pulse which travels from the top of the tube down to the water surface, and is then reflected back up the tube. The distance to the water level can then be calculated using the travel time of the pulse. This system filters out small-scale effects like wind-waves and has the capacity to measure sea-level changes within 1mm accuracy.

The tide gauge at Cocos Island observed the tsunami on December 26th 2004 as it passed by the island, as shown in these observations made during December.

Satellites

Satellite altimeters measure the height of the ocean surface directly by the use of electro-magnetic pulses. These are sent down to the ocean surface from the satellite and the height of the ocean surface can be determined by knowing the speed of the pulse, the location of the satellite and measuring the time that the pulse takes to return to the satellite.

One problem with this kind of satellite data is that it can be very sparse - some satellites only pass over a particular location about once a month, so you would be lucky to spot a tsunami since they travel so quickly. However, during the Indian Ocean tsunami of December 26th 2004, the Jason satellite altimeter happened to be in the right place at the right time.

The picture below shows the height of the sea surface (in blue) measured by the Jason satellite two hours after the initial earthquake hit the region southeast of Sumatra (shown in red) on December 26, 2004. The data were taken by a radar altimeter on board the satellite along a track traversing the Indian Ocean when the tsunami waves had just filled the entire Bay of Bengal. The data shown are the differences in sea surface height from previous observations made along the same track 20-30 days before the earthquake, showing the signals of the tsunami.

Picture courtesy of NASA/JPL-Caltech

The DART System

In 1995 the National Oceanic and Atmospheric Administration (NOAA) began developing the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. An array of stations is currently deployed in the Pacific Ocean. These stations give detailed information about tsunamis while they are still far off shore. Each station consists of a sea-bed bottom pressure recorder which detects the passage of a tsunami. (The pressure of the water column is related to the height of the sea-surface) .

The data is then transmitted to a surface buoy via sonar. The surface buoy then radios the information to the Pacific Tsunami Warning Center (PTWC) via satellite. The bottom pressure recorder lasts for two years while the surface buoy is replaced every year. The system has considerably improved the forecasting and warning of tsunamis in the Pacific.

The Indian Ocean tsunami of 26th December 2004

An undersea earthquake in the Indian Ocean on 26th December 2004 produced a tsunami that caused one of the biggest natural disasters in modern history. Over 200,000 people are known to have lost their lives.

The waves devastated the shores of parts of Indonesia, Sri Lanka, India, Thailand and other countries with waves reported up to 15 m high, reaching as far as Somalia on the east coast of Africa, 4500 km west of the epicentre. Refraction and diffraction of the waves meant that the impact of the tsunami was noticed around the world and sea-level monitoring stations in places such as Brazil and Queensland also felt the effect of the tsunami.

This animation (10.4Mb) was produced by scientists in the Bureau of Meteorology's National Tidal Centre. A numerical model was used to replicate the generation and propagation of the tsunami and it shows how the waves propagated around the world's ocean basins.

The earthquake took place at about 1am UTC (8am local time) in the Indian Ocean off the western coast of northern Sumatra. With a magnitude of 9.0 on the Richter scale, it was the largest since the 1964 earthquake off Alaska and equal fourth largest since 1900, when accurate global seismographic record-keeping began.

The epicentre of the earthquake was located about 250 km south-southeast of the Indonesian city of Banda Aceh. It was a rare megathrust earthquake and occurred on the interface of the India and Burma tectonic plates.

This was caused by the release of stresses that develop as the India plate subducts beneath the overriding Burma plate. A megathrust earthquake is where one tectonic plate slips beneath another, causing vertical motion of the plates. This large vertical displacement of the sea-floor generated the devastating tsunami, which caused damage over such a large area around the Indian Ocean.

The earthquake was also unusually large in geographical extent. An estimated 1200 km of faultline slipped about 15 m along the subduction zone over a period of several minutes. Because the 1,200 km of faultline affected by the quake was in a nearly north-south orientation, the greatest strength of the waves was in an east-west direction. Bangladesh, which lies at the northern end of the Bay of Bengal, had very few casualties despite being a populous low-lying country.

Due to the distances involved, the tsunami took anywhere from fifteen minutes to seven hours (for Somalia) to reach the various coastlines. (See this travel time map). The northern regions of the Indonesian island of Sumatra were hit very quickly, while Sri Lanka and the east coast of India were hit roughly two hours later. Thailand was also struck about two hours later, despite being closer to the epicentre, because the tsunami travelled more slowly in the shallow Andaman Sea off its western coast.

On its arrival on shore, the height of the tsunami varied greatly, depending on its distance and direction from the epicentre and other factors such as the local bathymetry. Reports have the height ranging form 2-3 m at the African coast (Kenya) up to 10-15 m at Sumatra, the region closest to the epicentre.

read more

Environment Clean Generations

Twice the Water

Like oil in the 20th century, water could well be the essential commodity on which the 21st century will turn.

Human beings have depended on access to water since the earliest days of civilization, but with 7 billion people on the planet as of October 31, exponentially expanding urbanization and development are driving demand like never before.Environment Clean Generations

Water use has been growing at more than twice the rate of population increase in the last century, said Kirsty Jenkinson of the World Resources Institute, a Washington think tank.

Water use is predicted to increase by 50 percent between 2007 and 2025 in developing countries and 18 percent in developed ones, with much of the increased use in the poorest countries with more and more people moving from rural areas to cities, Jenkinson said in a telephone interview.Environment Clean Generations

Factor in the expected impacts of climate change this century -- more severe floods, droughts and shifts from past precipitation patterns -- that are likely to hit the poorest people first and worst "and we have a significant challenge on our hands," Jenkinson said.

Will there be enough water for everyone, especially if population continues to rise, as predicted, to 9 billion by mid-century?

"There's a lot of water on Earth, so we probably won't run out," said Rob Renner, executive director of the Colorado-based Water Research Foundation.Environment Clean Generations

"The problem is that 97.5 percent of it is salty and ... of the 2.5 percent that's fresh, two-thirds of that is frozen. So there's not a lot of fresh water to deal with in the world."

Over a billion people lack access to clean drinking water, and over 2 billion live without adequate sanitation, leading to the deaths of 5 million people, mostly children, each year from preventable waterborne disease, Renner said.Environment Clean Generations

Only 8 percent of the planet's fresh water supply goes to domestic use and about 70 percent is used for irrigation and 22 percent in industry, Jenkinson said.

by "environment clean generations"

Marine Craft with Solar Power

Imagine a futuristic marine craft that looks like it jumped off the pages of a Jules Verne or H.G. Wells science fiction novel. Imagine breakthrough technology that captures the power of the sun for fueling adventures. Imagine traveling to exotic destinations in the equatorial regions of the earth using advanced technology. Imagine sailing around the world in a completely quiet vessel that does not cause adverse ecological or environmental impacts.Environment Clean Generations

Stop imagining! The future of ocean travel is upon us, and it is called the MS TÛRANOR. This is the largest solar-powered boat in the world. Craig Loomes from Auckland, New Zealand, designed the ship, and Knierim Werft in Kiel, Germany, built it. It took Werft about 14 months to construct the futuristic vessel. The name TÛRANOR comes from J.R.R. Tolkien's book "Lord of the Rings" and means "the power of the sun" and "victory," according to the PlanetSolar Web site.Environment Clean Generations

The large, 60-ton catamaran is nearly concealed by the solar panels topside. The ship's deck is an impressive 5,700 square feet of solar panels. The solar ship is large enough to hold up to 40 people: four crew members and 36 passengers.Environment Clean Generations

Some of the solar cell panels are adjustable to optimize sunlight capturing. The solar ship also is equipped with rechargeable power cells that can sustain the craft for up to three days if the ship encounters excessively cloudy skies or poor weather conditions.

This voyage to circumnavigate the earth using only the power of the sun began September 27, 2010. The ship set off from Monaco amidst much celebration and fanfare. The crew plans to sail the craft around the world at a leisurely average of 7.5 knots.

by "environment clean generations"

With Population Growth and Climate Change Making US Water Worse

Climate change and population growth in the United States will make having enough fresh water more challenging in the coming years, an expert on water shortages said on Wednesday.

"In 1985-1986 there were historical (water level) highs and now in less than 25 years we are at historical lows. Those sorts of swings are very scary," said Robert Glennon, speaking at the State of the Lakes Ecosystem Conference in Erie, Pennsylvania. Environment Clean Generations

Glennon, a professor at Arizona State University and the author of "Unquenchable: America's Water Crisis and What To Do About It," said that that according to climate experts, shorter, warmer winters mean less ice and greater exposure to the air, leading eventually to more water evaporation.

"We think about water like the air -- infinite and inexhaustible but it is very finite and very exhaustible," Glennon said.

"When you have a shorter ice season you have great exposure to the air and more evaporation. As temperatures go up it is very troubling," Glennon said. "The cycles are going to become more acute which is very troubling."

This past summer, Ohio Governor John Kasich vetoed a bill that would have allowed unrestricted removal of five million gallons of water from Ohio's lakes and rivers every 90 days.Environment Clean Generations

Kasich, a Republican who has criticized government regulations, surprised some political observers by following the advice of organizations that felt the bill would allow lake levels to become dangerously low.

Glennon agrees the bill would have set the stage for diversion in other lakes. "It would have been open season on the Great Lakes."Environment Clean Generations

Glennon doesn't believe that water diversion whether by pipeline, desalinization or more drilling are long-term answers. He thinks conservation, water reuse, and better agriculture practices bolstered by higher, seasonally-adjusted water costs will bring things in line.Environment Clean Generations

"We pay less for water than we pay for cell phone service or cable television," he said. "All of our incentives are wrong."

by "environment clean generations"

Cold Fusion is Big Ahead

Rossi, an Italian inventor, claims to have come up with the Holy Grail of power generation, an "Energy Catalyser" or E-Cat, which produces limitless energy. He has already carried out laboratory demonstrations in front of scientists and the Italian media, and in October he plans to unveil a one-megawatt power plant in the US. If it works, the E-Cat is the biggest thing since atomic power, bringing an inexhaustible supply of cheap energy. It looks much too good to be true and many dismiss it as an obvious scam, but Rossi has powerful support from some surprising quarters.

The E-Cat is deceptively simple: hydrogen is passed over a special catalyst based on nickel in a container about a litre in size, and enough heat is produced to boil water. A demonstration in January appeared to show a several kilowatts of output from a four hundred watt input. The catalyst is secret, but Rossi says it can be produced at low cost. The two questions that matter: does it really work? And what are the implications if it does?

The E-Cat is the latest incarnation of cold fusion, an area long shunned by respectable scientists. In 1989, researchers Stanley Pons and Martin Fleischmann claimed to have produced a small amount of energy by nuclear fusion on a lab bench via electrolysis. This was unprecedented and appeared to contradict accepted science, as fusion only occurs at temperatures of millions of degrees in the Sun and stars.

Other scientists failed to replicate this cold fusion, and the whole field was soon labelled bad science at best. Few journals will cover it these days. In science terms, an interest cold fusion is up there with astrology and alchemy.

A few scientists do still work in this field, notably at the US Naval Research Laboratory. Occasional papers are published claiming positive results in the area of "Low Energy Nuclear Reactions" and "excess heat generation". Nobody calls it cold fusion, and this is an area led by experiment rather than theory. But some scientists are breaking cover.

Frank Acland has been following Rossi's work closely, and has a website, E-Cat World, tackling the latest developments. He reels off a list of scientists who have examined the E-Cat for themselves and verified what was happening.

"They have all gone on the record to say that they believe that there is a nuclear reaction taking place, " says Acland, "that the levels of energy output the E-Cat produces could not come from a chemical reaction."

The demonstrations appear to show a lot more heat is coming out of apparatus than goes in. Two Swedish scientists from NyTeknik magazine ruled out any hidden power source and concluded: "The only alternative explanation is that there is some kind of a nuclear process that gives rise to the measured energy production." Unlike the Pons and Fleishman experiments, where the excess heat was tiny, this is on a massive scale. Rossi even claims to have been heating a factory using E-Cats. It's a big effect -- or a big hoax.

Rossi's heavyweight supporters include 1973 physics Nobel prize winner Brian Josephson. Josephson also supports telepathy research. Dennis Bushnell, chief scientist at Nasa's Langley Research Centre, appears to be a believer in the E-Cat, commenting in a recent interview with Electric Vehicle World that the science was being worked out and, "I think this will go forward fairly rapidly now". However, Nasa scientists are still at the stage of exploring whether there is valid physics behind the E-Cat rather than actually buying them.

Darpa, the Pentagon's advanced science wing, has also been involved in this field. Budget documents reveal a longstanding interest in low energy nuclear reactions, and the plan for 2012 includes the line "Establish scalability and scaling parameters in excess heat generation processes in collaboration with the Italian Department of Energy."

Ex-Darpa chief Tony Tether told New Energy Times that "If it is a hoax, it's a damned good one."

Inventors often complain that their technology could change the world if investors would just give them a few million to produce it. Rossi will get his chance. The one-megawatt device Rossi plans to soon demonstrate was originally meant to be made by combining 300 small E-Cats. It will now comprise 52 larger E-Cats.

What will it mean if it does work? The E-cat will provide a lightweight source of cheap energy, without any CO2 emissions. (And unlike nuclear fission, there is also no radioactive waste.) This could turn the world upside-down, and trigger a new industrial revolution which would shift away from fossil fuels and into an era of clean, plentiful energy.

The simplest application would use the steam or hot water from an E-Cat for heating. An E-Cat could heat your home so you would never need gas, oil or coal again. It could be scaled to heat offices, factories, or other buildings. Rossi eventually hopes to make 300,000 E-Cat modules a year.

The E-Cat could also bring back the steam engine. The steam car powered by an E-Cat could replace the electric car as green transport. The idea is not as peculiar as it might sound; steam cars have a long pedigree, and speed record for this type of vehicle is held by the British Steam Car team who achieved an impressive 149 mph in 2009. It might not make the sort of noise beloved of Jeremy Clarkson, but you'd never have to stop at a petrol station again, just top up with water at intervals.

Electricity generation is more challenging. Rossi says the E-Cat only runs at about 500 degrees for safety reasons; modern power plants run at higher temperatures, which are more efficient. Rossi says he is working on the problem, and reckons that E-Cats could produce electricity for about 2,000 Euros per kilowatt initially, with costs falling dramatically when economies of scale kick in. Combined heat and power units would be most economical, and domestic E-Cats could see people selling to the grid rather than buying from it. Energy prices would plummet, and it could create a new type of economy.

"Many people go to work every day to have enough money to fuel their cars, pay the light and heat bills, and to pay for goods whose cost is largely made up of the energy required to produce and transport it," says Acland. "If energy prices go down across the board, theoretically goods will become much cheaper, and people won't need to work in the same way that they do now just to survive."

Because it does not produce carbon dioxide, the E-Cat solves the CO2 emission problem at a stroke. Transport, manufacturing and heating will all switch over to E-Cat because of the lower costs, and fossil fuels would become a thing of the past. Britain's reliance on imported gas would end, and oil imports would all but cease, being confined to a few niche applications. Oil companies, and oil-based economies, would collapse.

It's an appealing vision -- unless you happen to be working in one of the sectors that would be affected -- but until later this month we can't tell if it's for real.

Skeptics point to the lack of published science, and the way that Rossi keeps details of his special catalyst secret. They also point to his past involvement in Petroldragon, a company involved in converting organic waste into fuel, which collapsed in the 1990's amidst allegations of dumping toxic waste. (Rossi maintains that he was the victim in this complex case).

And the E-Cat development has thrown up its own scandal. Until August of this year, Rossi was planning his big launch in Greece, and an E-Cat factory was being built in Xanthi. But the deal has somehow fallen through for unexplained reasons, vaguely blamed on pressure from "international energy interests" who may be threatened by the invention.

The megawatt E-Cat will be unveiled in America. Rossi has licensed the technology to a start-up called Ampenergo. Though new, the company has credentials; one of its founders is Robert Gentile, Assistant Secretary of Energy for Fossil Energy at the US Department of Energy (DOE) in the 90's.

Rossi claims the demonstration will be attended by high-level scientists and science journalists, unlike previous occasions which have had little mainstream coverage. They have not so much attacked his claims as ignored them.

Surprisingly enough, Rossi's most severe critic is Steven Krivit, editor of the New Energy Times. Krivit has had years of experience at looking at all sorts cold fusion devices which have been claimed to produce power. His team have carried out a very thorough analysis of Rossi's demonstrations and they have their doubts.

"According to my analysis, his claim has no scientific credibility," Krivit told Wired.co.uk. The device he claimed to heat a factory in Bondeno seems to exist only on paper."

Krivit's analysis looks at the amount of steam that actually comes out of the device and the way it is measured. He concludes that the E-Cat does not have nearly the output he suggests, and may not even be producing excess energy.

Krivit's answer to the question of whether Rossi's demonstrations support his claims is: "Definitely no."

There is some irony at work here: we apparently have a number of mainstream scientists backing an outlandish project which inves, tors are putting money into, while the most vocal critic comes from the world of cold fusion.

Who's right? The only way to find out will be to watch out for what Rossi does later this month.

by "environment clean generations"

MIT's Artificial Leaf is Better

Speaking at the National Meeting of the American Chemical Society in California, MIT professor Daniel Nocera claims to have created an artificial leaf, made from stable and inexpensive materials, which mimics nature's photosynthesis process.

The device is an advanced solar cell, no bigger than a typical playing card, which is left floating in a pool of water. Then, much like a natural leaf, it uses sunlight to split the water into its two core components, oxygen and hydrogen, which are stored in a fuel cell to be used when producing electricity.

Nocera's leaf is stable -- operating continuously for at least 45 hours without a drop in activity in preliminary tests -- and made of widely available, inexpensive materials -- like  silicon, electronics and chemical catalysts. It's also powerful, as much as ten times more efficient at carrying out photosynthesis than a natural leaf.

With a single gallon of water, Nocera says, the chip could produce enough electricity to power a house in a developing country for an entire day. Provide every house on the planet with an artificial leaf and we could satisfy our 14 terrawatt need with just one gallon of water a day.
Those are impressive claims, but they're also not just pie-in-the-sky, conceptual thoughts. Nocera has already signed a contract with a global megafirm to commercialise his groundbreaking idea. The mammoth Indian conglomerate, Tata Group has forged a deal with the MIT professor to build a small power plant, the size of a refrigerator, in about a year and a half.

This isn't the first ever artificial leaf, of course. The concept of emulating nature's energy-generating process has been around for decades and many scientists have tried to create leaves in that time. The first, built more than ten years ago by John Turner of the US National Renewable Energy Laboratory, was efficient at faking photosynthesis but was made of rare and hugely expensive materials. It was also highly unstable, and had a lifespan of barely one day.

For now, Nocera is setting his sights on developing countries. "Our goal is to make each home its own power station," he said. "One can envision villages in India and Africa not long from now purchasing an affordable basic power system based on this technology."

by "environment clean generations"

A Huge Pipe, a Balloon and Water

It sounds barmy, audacious or sci-fi: a tethered balloon the size of Wembley stadium suspended 20km above Earth, linked to the ground by a giant garden hose pumping hundreds of tonnes of minute chemical particles a day into the thin stratospheric air to reflect sunlight and cool the planet.

But a team of British academics will next month formally announce the first step towards creating an artificial volcano by going ahead with the world's first major "geo-engineering" field-test in the next few months. The ultimate aim is to mimic the cooling effect that volcanoes have when they inject particles into the stratosphere that bounce some of the Sun's energy back into space, so preventing it from warming the Earth and mitigating the effects of man-made climate change.

 

Before the full-sized system can be deployed, the research team will test a scaled-down version of the balloon-and-hose design. Backed by a £1.6m government grant, the team will send a balloon to a height of 1km over an undisclosed location. It will pump nothing more than water into the air, but it will allow climate scientists and engineers to gauge the engineering feasibility of the plan. Ultimately, they aim to test the impact of sulphates and other aerosol particles if they are sprayed directly into the stratosphere.

If the technical problems posed by controlling a massive balloon at more than twice the cruising height of a commercial airliner are resolved, then the team from Cambridge, Oxford, Reading and Bristol universities expect to move to full-scale solar radiation tests.

The principal investigator, Matthew Watson, a former UK government scientific adviser on emergencies and now a Bristol University lecturer, says the experiment is inspired by volcanoes and the way they can affect the climate after eruptions.

"We will test pure water only, in sufficient quantity to test the engineering. Much more research is required," he said, in answer the question of what effect a planetary-scale deployment of the technology could have.

Other leaders of the government-funded Stratospheric particle injection for climate engineering (Spice) project have investigated using missiles, planes, tall chimneys and other ways to send thousands of tonnes of particles into the air but have concluded that a simple balloon and hosepipe system is the cheapest. 

The research is paid for by the government-funded Engineering and Physical Sciences Research Council.

"The whole weight of this thing is going to be a few hundred tonnes. That's the weight of several double-decker buses. So imagine how big a helium balloon do you need to hold several double-decker buses – a big balloon. We're looking at a balloon which is possibly 100-200m in diameter. It's about the same size as Wembley stadium," said the Oxford engineering lecturer Hugh Hunt in an interview earlier this year.

"This hose would be just like a garden hose, 20km long and we pump stuff up the pipe. The nice thing about it is that we can really have a knob, if you like, which we can control to adjust the rate at which we inject these particles."

While the October experiment is expected to have no impact on the atmosphere, it could also be used to try out "low-level cloud whitening", a geo-engineering proposal backed financially by Microsoft chairman and philanthropist Bill Gates.

In this case, fine sea salt crystals would be pumped up and sprayed into the air to increase the number of droplets and the reflectivity in clouds. Together, many droplets are expected to diffuse sunlight and make a cloud whiter.

However, environment groups in Britain and the US said the government's experiment was a dangerous precedent for a full-scale deployment that could affect rainfall and food supplies. Even if the approach successfully cools the planet by bouncing some of the Sun's energy back into space, it would do nothing for the build up of CO₂ in the atmosphere, which leads to increased ocean acidity.

"What is being floated is not only a hose but the whole idea of geo-engineering the planet. This is a huge waste of time and money and shows the UK government's disregard for UN processes. It is the first step in readying the hardware to inject particles into the stratosphere. It has no other purpose and it should not be allowed to go ahead," said Pat Mooney, chair of ETC Group in Canada, an NGO that supports socially responsible development of technology.

Mike Childs, head of science, policy and research at Friends of the Earth UK, said: "We are going to have to look at new technologies which could suck CO₂ out of the air. But we don't need to do is invest in harebrained schemes to reflect sunlight into space when we have no idea at all what impact this may have on weather systems around the globe."

But the principle of large-scale geoengineering has been backed strongly by Sir Martin Rees, the former president of Royal Society, which in 2009 concluded in a report that it may be necessary to have a "plan B" if governments could not reduce emissions.

"Nothing should divert us from the main priority of reducing global greenhouse gas emissions. But if such reductions achieve too little, too late, there will surely be pressure to consider a 'plan B' – to seek ways to counteract the climatic effects of greenhouse gas emissions by 'geoengineering'," said Rees.

Members of the British public who were consulted by researchers in advance of the Spice experiment were broadly sceptical.

"Overall almost all of our participants were willing to entertain the notion that the test-bed as an engineering test – a research opportunity – should be pursued. Equally, very few were fully comfortable with the notion of stratospheric aerosols as a response to climate change," the Cardiff University-based researchers concluded.

by "environment clean generations"

Discovery of how Water was Present on Earth and Mars

The discovery of the mineral jarosite in rocks analyzed by the Mars Rover, Opportunity, on the Martian surface had special meaning for a team of Syracuse University scientists who study the mineral here on Earth. Jarosite can only form in the presence of water. Its presence on Mars means that water had to exist at some point in the past. The trick is in figuring out if jarosite can be used as a proxy for determining when, and under what conditions, water was present on the planet.

The SU scientists have done just that. In a recent study published in an October issue issue of Earth and Planetary Science Letters, Suzanne Baldwin, professor of Earth Sciences in SU's College of Arts and Sciences; and Joseph Kula, research associate and corresponding author for the study, established the "diffusion parameters" for argon in jarosite. In simpler terms, they discovered a way to use the noble gas argon, which accumulates in jarosite over time, to determine the age of the mineral and the surface conditions under which it formed.

The discovery of the mineral jarosite in rocks analyzed by the Mars Rover, Opportunity, on the Martian surface had special meaning for a team of Syracuse University scientists. (Credit: NASA)

                                                                    

The new study is the first in a series of experiments designed to provide a roadmap of sorts for scientists who may someday study Martian samples brought back to Earth. "Our experiments indicate that over billion-year timescales and at surface temperatures of 20 degrees Celsius (68 degrees Fahrenheit) or colder, jarosite will preserve the amount of argon that has accumulated since the crystal formed," Kula says, "which simply means that jarosite is a good marker for measuring the amount of time that has passed since water was present on Mars."

Moreover, since the development of life requires water, knowing when and for how long water was present on the Martian surface has implications for the search for potential habitats harboring life, the scientists say. "Jarosite requires water for its formation, but dry conditions for its preservation," Baldwin says. "We'd like to know when water formed on the surface of Mars and how long it was there. Studying jarosite may help answer some of these questions."

Jarosite is a byproduct of the weathering of rocks exposed at the surface of a planet (such as Earth and Mars). The mineral forms when the right mixture of oxygen, iron, sulfur, potassium and water is present. Once formed, the crystals begin to accumulate argon, which is produced when certain potassium isotopes in the crystals decay. Potassium decay is a radioactive process that occurs at a known rate. By measuring the isotopes of argon trapped within the crystals, scientists can determine the age of the crystals.

However, because argon is a gas, it can potentially escape rapidly from the crystals under hot conditions or slowly over long durations at cold conditions. In order to determine the reliability of the "argon clock" in jarosite, the scientists had to determine the temperature limits to which the crystals could be subjected and still retain the argon. Using a combination of experiments and computer modeling, the team found that argon remains trapped inside the crystals for long periods of time over a range of planetary surface temperatures.

"Our results suggest that 4 billion-year-old jarosite will preserve its argon and, along with it, a record of the climate conditions that existed at the time it formed," Baldwin says. The scientists are in the process of conducting further studies on jarosite that formed less than 50 million years ago in the Big Horn Basin in Wyoming, which they hope will reveal when the minerals formed and how fast environmental conditions changed from water-saturated to dry. The results can be used as a context for interpreting findings on other planets.

Baldwin and Kula are members of the NASA-funded New York Center for Astrobiology at Rensselaer Polytechnic Institute in Troy, N.Y. The center is one of 10 such centers nationally that are part of the NASA Astrobiology Institute, located at NASA's Ames Research Center at Moffett Field, Calif. Their jarosite research is funded by NASA.

 by "environment clean generations"

Irrigation Might Raise Sea Level

Ocean levels have risen several inches over the last century, and that's only likely to increase going forward. Most of that is related to climate change — but now scientists may have discovered a hidden factor in all this: irrigation. 

At first glance, that might seem surprising. After all, irrigation is just moving water from one area to another, to allow people to live in naturally dry or arid areas. The problem is that not all irrigation comes from water already on the surface - a lot of it is now extracted from deep underground, introducing tons of extra water that would not otherwise be a part of the planet's water cycle.

Researchers from the US Geological Survey calculated that the last century saw over a thousand cubic miles worth of water extracted from underground and used for irrigation purposes. 

That was enough water to boost ocean levels by about half an inch, accounting for 12.6% of the total sea level rise in the 20th century.

And all this isn't likely to stop anytime soon. Ground water extraction has skyrocketed in the last decade, with some estimates say we're now bringing up about 34 cubic miles each year. That's enough to increase sea levels by .016 inches each year, which is 13% of the current rise. 

While melting ice and other climate-related factors remain responsible for the vast majority of the sea level increase, this adds a new wrinkle to how we use irrigation and ground water going forward.

by "environment clean generations"

Manufacturing Water

Water is becoming an increasingly important issue in the developed world. But this issue is nothing new for other, less developed nations. For centuries, clean drinking water has been hard to come by for many populations, especially the poor. In some areas, water may be available, but it's often disease-ridden, and drinking it can be fatal. In other areas, a viable water supply is sim­ply not available at all.

­A 2006 United Nations report estimated that as much as 20 percent of the world's population doesn't have access to clean drinking water [source: BBC]. This leads us to wonder: If we need it so badly, why can't we jus­t make it?

­Water is made of two hydrogen atoms attached to an oxygen atom. This seems like pretty basic chemistry, so why don't we just smash them together and solve the world­'s water ills? Theoretically, this is possible, but it would be an extrem­ely dangerous process, too.

To create water, oxygen and hydrogen atoms must be present. Mixing them together doesn't help; you're still left with just separate hydrogen and oxygen atoms. The orbits of each atom's electrons must become linked, and to do that we must have a sudden burst of energy to get these shy things to hook up.

­Since hydrogen is extremely flammable and oxygen supports combustion, it wouldn't take much to create this force. Pretty much all we need is a spark -- not even a flame -- and boom! We've got water. The hydrogen and oxygen atoms' electrons' orbits have been conjoined.

But we also have an explosion and -- if our experiment was big enough, a deadly one. The ill-fated blimp, the Hindenburg, was filled with hydrogen to keep it afloat. As it approached New Jersey on May 6, 1937, to land after a trans-Atlantic voyage, static electricity (or an act of sabotage, according to some) caused the hydrogen to spark.

When mixed with the ambient oxygen in the air, the hydrogen exploded, enveloping the Hindenburg in a ball of fire that completely destroyed the ship within half a minute.

There was, however, also a lot of water created by this explosion.

To create enough drinking water to sustain the global population, a very dangerous and incredibly large-scale process would be required. Still, over a century ago the thought ­of an internal combustion engine -- with its controlled repeated explosions -- seemed dangerously mad. And as water becomes scarcer, the process of joining hydrogen atoms to oxygen atoms may become more attractive than it is currently. Necessity, after all, is the mother of invention.

But there are safer ways of creating water out of thin air, and projects to do just that are already underway. Read the next page to learn about a few mad scientists who may end up solving the world's impending water crisis.

  

   Creating Water from Thin Air

There's water around us all the time, we just can't see it. The air in our atmosphere contains a varying amount of water vapor, depending on the weather. When it's hot and humid, evaporated water can make up as much as 6 percent of the air we breathe. On cold, dry days it can be as low as .07 percent of the air's makeup [source: U.S. Department of Energy].

 

This air is part of the water cycle, an Earth process. Crudely put, water evaporates out of rivers, lakes and the ocean. It's carried up into the atmosphere, where it can collect into clouds (which are actually just accumulations of water vapor). After the clouds reach the saturation point, water droplets will form, which we know as rain. This rain runs off the land and collects into bodies of water, where the whole process begins again.

The problem is, the water cycle goes through dry periods. Because of this, some inventors have begun to wonder, why wait? Why not pull the water vapor right out of the air?

One Australian inventor has done just that. Max Whisson is the creator of the Whisson Windmill, a machine that uses wind power to collect water out of the atmosphere. Whisson points out to the Australian Broadcasting Corporation that water vapor amounts to about "10,000 billion litres [about 2,600 billion gallons] in the bottom kilometere [about .62 miles] of air around the world" [source: ABC]. What's more, this water is replaced every few hours as part of the water cycle.

Whisson's windmill uses refrigerant to cool the blades of his mill, which he's named Max Water. These blades are situated vertically rather than diagonally, so that even the slightest breeze turns them. The cool blades cool the air, causing the water vapor to condense -- become liquid water again. This condensation is then collected and stored.

Whisson's windmill can collect as much as 2,600 gallons of water from the air per day.

Whisson says that his biggest challenge isn't the engineering behind his invention but finding the venture capital to back it -- he says that people think it's too good to be true. This problem would sound familiar to a pair of American inventors who have a water-making invention of their own.

Jonathan Wright and David Richards have created a machine that's similar to Whisson's, except that it resembles a collapsible pull-behind camper more than it favors a windmill. This invention -- which its creators call AquaMagic -- pulls air directly from the area surrounding it. Inside the machine, the air is cooled via a refrigerated coil. The air condenses, and the water is collected, purified, and released through a spigot.

The AquaMagic machine -- which currently cost about $28,000 per unit -- can produce up to 120 gallons of purified water in 24 hours, and since it's small it can be toted to disaster sites and Sub-Saharan Africa alike. But it also has one drawback: To produce this much water, AquaMagic requires about 12 gallons of diesel fuel. It's here that the Whisson Windmill (which runs about $43,000 per unit) has a clear advantage over AquaMagic: It's totally green. It runs exclusively on wind power, requiring no fossil fuel. Even the condenser runs off the power generated by the windmill's turbines.

Speaking of the environment, why go to the trouble of collecting water out of the air? Why not simply cause more rain to fall? It may sound far-fetched, but this is actually done -- at times, with catastrophic consequences.

Cloud Seeding and the British Disaster

HowStuffWorks has discussed China's plan to prevent rain during the opening ceremonies of the 2008 Olympics in Beijing. The process, called cloud seeding, works by firing silver iodide into storm clouds in the days leading up to the event. The Chinese government hoped it could essentially "use up" the existing clouds and assure clear skies for the ceremony.

The country's been doing it for decades -- with positive results. But another experiment in cloud seeding, on the other side of the Eurasian land mass, didn't go so smoothly.

Following World War II, the British government was still looking at ways to get a leg up over enemy militaries. The Nazis had come close to destroying Britain, and the United Kingdom had developed a taste for preparation. The British government looked to the skies for an advantage. The Royal Air Force (RAF) began experimenting with cloud seeding. By impregnating the clouds with the particles needed to create a severe thunderstorm, the British could effectively thwart the movement of troops and even literally rain out enemy advances. But the cloud-seeding project went terribly awry.

It's not that the experiments with cloud seeding didn't work. It worked too well.

In 2001, the British Broadcasting Corporation (BBC) investigated rumors that the RAF had seeded the clouds over England. They turned up first-person accounts of some of the pilots who were involved in a top-secret mission called Operation Cumulus. During this August 1952 operation, RAF pilots flew above the cloud line, dropping payloads of dry ice, salt and -- like the Chinese currently use -- silver iodide.

After just 30 minutes, rain began to fall from the infected clouds. At first, the RAF pilots -- dubbed rainmakers by the press -- reputedly celebrated their success. But within the week a deluge began. By the end of the month, North Devon, an area of England near the site of the cloud-seeding experiment, experienced 250 times the normal amount of rainfall [source: BBC].

On August 15, 1952, the day the rain started, an estimated 90 million tons of water coursed through the town of Lynmouth in just one day [source: The Guardian]. Entire trees were uprooted, forming dams and allowing the tide of the two rivers flowing through Lynmouth to grow even stronger in force. Boulders were carried by the current, destroying buildings and carrying residents into the sea. In all, 35 Britons lost their lives that day as a result of the torrential rain. Britain's Ministry of Defense maintains that it had not experimented with cloud seeding prior to the Lynmouth incident.

China and Britain paint two versions of the same picture. On one hand, the Asian nation has successfully created a cloud-seeding program. They've managed to generate irrigation for arid croplands from the ultimate source. But the British disaster shows the potential results of toying with the forces of nature.

And still, we need water more than ever. Using explosions isn't viable to produce water currently, and AquaMagic and Whisson's Windmill aren't being produced on a large enough scale to help with the immediate need for water. Water is a finite resource, and one life on Earth can't do without.

 by "environment clean generations"

Deciphering The Earth, A Brief Review

n "The Hitchhiker's Guide to the Galaxy," Arthur Dent has trouble getting his mind around the Vogon Constructor Fleet's destruction of the Earth. He can't process it -- it's just too big. Arthur tries to narrow it down, but thinking of England, New York, Bogart movies and the dollar produces no reaction. Only when he considers the extinction of McDonald's hamburgers does it finally sink in.

After deciding to write about how the Earth works, we felt a little like Arthur Dent. Even though it's tiny compared to the rest of the universe, the Earth is enormous, and it's extremely complex.

But instead of collectively going out for a burger, we decided to take another approach. Rather than examining each of the Earth's parts, we'll look at what ties it all together. Just about everything on Earth happens because of the presence of the sun. 

Power and light

Compared to the rest of the universe, the Earth is very small. Our planet and eight (or maybe nine) others orbit the sun, which is only one of about 200 billion stars in our galaxy. Our galaxy, the Milky Way, is part of the universe, which includes millions of other galaxies and their stars and planets. By comparison, the Earth is microscopic.

Compared to a person, on the other hand, the Earth is enormous. It has a diameter of 7,926 miles (12,756 kilometers) at the equator, and it has a mass of about 6 x 10²⁴ kilograms. The Earth orbits the sun at a speed of about 66,638 miles per hour (29.79 kilometers per second). Don't dwell on those numbers too long, though; to a lot of people, the Earth is inconceivably, mind-bogglingly big. And it's just a fraction of the size of the sun.

From our perspective on Earth, the sun looks very small. This is because it's about 93 million miles away from us. The sun's diameter at its equator is about 100 times bigger than Earth's, and about a million Earths could fit inside the sun. The sun is inconceivably, mind-bogglingly bigger.

 

But without the sun, the Earth could not exist. In a sense, the Earth is a giant machine, full of moving parts and complex systems. All those systems need power, and that power comes from the sun.

The sun is an enormous nuclear power source -- through complex reactions, it transforms hydrogen into helium, releasing light and heat. Because of these reactions, every square meter of our planet's surface gets about 342 Watts of energy from the sun every year. This is about 1.7 x 10¹⁷ Watts total, or as much as 1.7 billion large power plants could generate [source: NASA]. You can learn about how the sun creates energy in How the Sun Works.

When this energy reaches the Earth, it provides power for a variety of reactions, cycles and systems. It drives the circulation of the atmosphere and the oceans. It makes food for plants, which many people and animals eat. Life on Earth could not exist without the sun, and the planet itself would not have developed without it.

To a casual observer, the sun's most visible contributions to life are light, heat and weather. Now we'll look at how the sun powers each of those.

A World of Spheres

People generally think of the Earth as a "blue marble" or a sphere, although it's really shaped more like a pumpkin. But scientists classify the Earth as several spheres:

• Atmosphere: the air we breathe


• Biosphere or ecosphere: the life on earth


• Geosphere: the layers of the planet itself


• Hydrosphere: all of the water, including oceans, rivers, and lakes


• Cryosphere: the ice at the poles


• Anthrosphere: the people who live on the Earth

 Night and day

Some of the sun's biggest impacts on our planet are also its most obvious. As the Earth spins on its axis, parts of the planet are in the sun while others are in the shade. In other words, the sun appears to rise and set. The parts of the world that are in daylight get warmer while the parts that are dark gradually lose the heat they absorbed during the day.

You can get a sense of how much the sun affects the Earth's temperature by standing outside on a partly cloudy day. When the sun is behind a cloud, you feel noticeably cooler than when it isn't. The surface of our planet absorbs this heat from the sun and emits it the same way that pavement continues to give off heat in the summer after the sun goes down. Our atmosphere does the same thing -- it absorbs the heat that the ground emits and sends some of it back to the Earth.

The Earth's relationship with the sun also creates seasons. The Earth's axis tips a little -- about 23.5 degrees. One hemisphere points toward the sun as the other points away. The hemisphere that points toward the sun is warmer and gets more light -- it's summer there, and in the other hemisphere it's winter. This effect is less dramatic near the equator than at the poles, since the equator receives about the same amount of sunlight all year. The poles, on the other hand, receive no sunlight at all during their winter months, which is part of the reason why they're frozen.

Most people are so used to the differences between night and day (or summer and winter) that they take them for granted. But these changes in light and temperature have an enormous impact on other systems on our planet. One is the circulation of air through our atmosphere. For example:

1. The sun shines brightly over the equator. The air gets very warm because the equator faces the sun directly and because the ozone layer is thinner there.


2. As the air warms, it begins to rise, creating a low pressure system. The higher it rises, the more the air cools. Water condenses as the air cools, creating clouds and rainfall. The air dries out as the rain falls. The result is warm, dry air, relatively high in our atmosphere.


3. Because of the lower air pressure, air rushes toward the equator from the north and south. As it warms, it rises, pushing the dry air away to the north and the south.


4. The dry air sinks as it cools, creating high-pressure areas and deserts to the north and south of the equator.

This is just one piece of how the sun circulates air around the world -- ocean currents, weather patterns and other factors also play a part. But in general air moves from high-pressure to low-pressure areas, much the way that high-pressure air rushes from the mouth of an inflated balloon when you let go. Heat also generally moves from the warmer equator to the cooler poles.

Imagine a warm drink sitting on your desk -- the air around the drink gets warmer as the drink gets colder. This happens on Earth on an enormous scale.

The Coriolis Effect, a product of the Earth's rotation, affects this system as well. It causes large weather systems, like hurricanes, to rotate. It helps create westward-running trade winds near the equator and eastward-running jet streams in the northern and southern hemispheres. These wind patterns move moisture and air from one place to another, creating weather patterns. (The Coriolis Effect works on a large scale -- it doesn't really affect the water draining from the sink like some people suppose.)

The sun gets much of the credit for creating both wind and rain. When the sun warms air in a specific location, that air rises, creating an area of low pressure. More air rushes in from surrounding areas to fill the void, creating wind. Without the sun, there wouldn't be wind. There also might not be breathable air at all. 

  

Sun and Moon

The sun has a relationship with the moon, too. The light we see when the moon shines at night is really reflected light from the sun. The relative positions of the sun and moon also create solar and lunar eclipses. This might make it seem like the moon is nothing without the sun, but it does some important jobs for the Earth. The moon regulates the Earth's orbit, and it causes the ocean tides.

Sugar and carbon

The Earth's atmosphere is mostly composed of nitrogen. Oxygen makes up just 21 percent of the air we breathe. Carbon dioxide, argon, ozone, water vapor and other gasses make up a tiny portion of it, as little as 1 percent. These gasses probably came from several processes as the Earth evolved and grew as a planet.

But some scientists believe that the Earth's atmosphere would never have contained the oxygen we need without plants. Plants (and some bacteria) release oxygen during photosynthesis, the process they use to change water and carbon dioxide into sugar they can use for food.


Photosynthesis is a complex reaction. In a lot of ways, it's similar to the way your body breaks down food into fuel that it can store. Essentially, using energy from the sun, a plant can transform carbon dioxide and water into glucose and oxygen. In chemical terms:
6CO₂ + 12H₂O + Light -> C₆H₁₂O₆ + 6O₂+ 6H₂O

In other words, while we inhale oxygen and exhale carbon dioxide, plants inhale carbon dioxide and exhale oxygen. Some scientists believe that our atmosphere had little to no oxygen before plants evolved and started releasing it.

Without the sun to feed plants (and the plants to release oxygen), we might not have breathable air. Without plants to feed us and the animals most people use for food, we'd also have nothing to eat.
Obviously, plants are important, but not just because they give us food to eat and oxygen to breathe. Plants help control the amount of carbon dioxide, a greenhouse gas, in the atmosphere. 

They protect the soil from wind and from water runoff, helping to control erosion. In addition, they release water into the air during photosynthesis. This water, along with the rest of the water on the planet, takes part in a huge cycle that the sun controls

  

The Carbon Cycle

Carbon is fundamental to life -- all organic forms of life contain it. On Earth, carbon cycles through the atmosphere and the planet itself. This cycle has two components. The geological component involves carbon-containing compounds eroding from the land, washing into the sea, entering the Earth's mantle layer and being expelled through volcanoes. The biological component involves plants' and animals' inspiration and expiration. Since carbon is a greenhouse gas, its presence affects how warm or cool the planet is. The NASA Earth Observatory has a thorough explanation of the carbon cycle.

Water and fire

The sun has a huge effect on our water. It warms the oceans around the tropics, and its absence cools the water around the poles. Because of this, ocean currents move large amounts of warm and cold water, drastically affecting the weather and climate around the world. The sun also drives the water cycle, which moves about 18,757 cubic miles (495,000 cubic kilometers) of water vapor through the atmosphere every yea.

If you've ever gotten out of a swimming pool on a hot day and realized a few minutes later that you were dry again, you have firsthand experience with evaporation. If you've seen water form on the side of a cold drink, you've seen condensation in action. These are primary components of the water cycle, also called the hydrologic cycle, which exchanges moisture between bodies of water and land masses. The water cycle is responsible for clouds and rain as well as our supply of drinking water.
Here's what happens:

1. The sun shines on the surface of oceans and lakes, exciting molecules of water. The more the sun excites the molecules, the faster they move, or evaporate.


2. The molecules rise through the atmosphere as water vapor. Plants add to this water vapor through transpiration, a byproduct of photosynthesis, which also depends on the sun. In some locations, water sublimates, or changes directly from ice to vapor.


3. All of this water vapor rises into the atmosphere. The higher it rises, the cooler it gets. The molecules of water slow down and stick together, or condense, as they cool. This forms clouds. Depending on how high and thick they are, clouds can either warm or cool the surface of the planet under them.


4. Droplets continue to combine inside the clouds. When they get big and heavy enough, they fall as precipitation. (Pollution in clouds can decrease the amount of rainfall by requiring droplets to be bigger and heavier before they can fall.)


5. Precipitation falls as rain, snow, sleet or hail, depending on the temperature and other conditions. Over land, it falls onto the ground and into rivers and lakes. Some of the water seeps into the soil, nourishing plants and joining the groundwater. Much of it flows into rivers and lakes, which eventually run into the ocean.

Without the sun to start the process of evaporation, the water cycle wouldn't exist. We wouldn't have clouds, rain or weather. The water on the planet would be stagnant. It would also be solid, since without the sun to warm it, the Earth would be entirely frozen.

The sun powers the processes that control our climate and the content of our atmosphere. Without it, we wouldn't have oxygen or liquid water on our planet. We wouldn't have weather or seasons. But the sun's immense source of power also has some drawbacks. Next, we'll look at some of phenomena that protect Earth from the power of the sun.

The Earth's Atmosphere

Some people imagine the Earth's atmosphere as a blanket of air that gets thinner and colder the higher you go. While the atmosphere does tend to get thinner, it's made of distinct regions, and some outer layers are much hotter than our planet's surface. NASA has a great description of the layers of the atmosphere with links to images of each.

Heat and wind

The sun's massive power source has two main disadvantages -- ultraviolet light and the solar wind. Ultraviolet light can cause cancer, cataracts and other health problems. The solar wind, a stream of charged, or ionized, particles that stream off of the sun, could strip away our atmosphere. Fortunately, the Earth has some natural defenses against both. Our ozone layer protects us from ultraviolet (UV) light, and our magnetic field protects us from the solar wind.

The stratosphere, the layer of atmosphere just above the one in which we live, contains a thin layer of ozone (O3). This layer wouldn't exist without the sun. Ozone is made of three atoms of oxygen. It's not a very stable molecule, but it takes a lot of power to create it. When UV light hits a molecule of oxygen (O2) of, it splits it into two atoms of oxygen (O).

When one of these atoms comes into contact with a molecule of oxygen, they combine to make ozone. The process also works in reverse -- when UV light hits ozone, it splits it into a molecule of oxygen and an atom of oxygen.

This process is called the ozone-oxygen cycle, and it converts UV light into heat, preventing it from reaching the surface of the Earth. Without the sun, the Earth wouldn't have an ozone layer -- but without the sun, the Earth also wouldn't need it.

 

Oxygen molecule + light = two atoms of oxygen. Oxygen atom + oxygen molecule = ozone molecule.

But while the sun creates the ozone layer, the Earth itself creates its defense against the solar wind. Without the Earth's magnetic field, ionized particles from the solar wind could strip the planet's atmosphere away. This magnetic field comes from deep inside the Earth's core. Interactions between the inner and outer core create the magnetic field.

The planet's inner core is made of solid iron. Surrounding the inner core is a molten outer core. These two layers are very deep within the Earth, separated from its crust by the thick mantle. The mantle is solid but malleable, like plastic, and it's the source of the magma that comes from volcanoes.

The Earth's inner core spins, much like the Earth spins on its axis. The outer core spins as well, and it spins at a different rate than the inner core. This creates a dynamo effect, or convections and currents within the core. This is what creates the Earth's magnetic field -- it's like a giant electromagnet. When the solar wind reaches the Earth, it collides with the magnetic field, or magnetosphere, rather than with the atmosphere.



The poles actually change places periodically -- about 400 times in the last 330 million years. The field weakens while the shift takes place. But computer simulations predict that the sun might come to the rescue, interacting with the atmosphere to supplement the magnetic field, while the shift is in process.
The Earth's physical composition generates its magnetic field. That composition is a product of the Earth's creation, which would not have been possible without the sun.

 Image courtesy SOHO Consortium. SOHO is a project of international cooperation between ESA and NASA.

How Do We Know?

As with evolution, the Big Bang Theory has caused some controversy. Here are a few of the reasons scientists think it's accurate:

• All of the matter in the universe is moving away from all the other matter at a very fast rate. Scientists have proven this by measuring stars' Hubble red shift, or how light waves get stretched out as they rush away from us.


• Scientists can detect and measure low-level radiation called cosmic microwave background (CMB) or primordial background radiation. This seems to be an aftereffect of the Big Bang. New analysis of the CMB suggests that the universe changed from a microscopic point to an enormous system in a fraction of a second

Planets and stars

The most prominent scientific theory about the origin of the Earth involves a spinning cloud of dust called a solar nebula. This nebula is a product of the Big Bang. Philosophers, religious scholars and scientists have lots of ideas about where the universe came from, but the most widely-held scientific theory is the Big Bang Theory. According to this theory, the universe originated in an enormous explosion.

Before the Big Bang, all of the matter and energy now in the universe was contained in a singularity. A singularity is a point with an extremely high temperature and infinite density. It's also what's found at the center of a black hole. This singularity floated in a complete vacuum until it exploded, flinging gas and energy in all directions. Imagine a bomb going off inside an egg -- matter moved in all directions at high speeds.

As the gas from the explosion cooled, various physical forces caused particles to stick together. As they continued to cool, they slowed down and became more organized, eventually growing into stars. This process took about a billion years.

About five billion years ago, some of this gas and matter became our sun. At first, it was a hot, spinning cloud of gas that also included heavier elements. As the cloud spun, it collected into a disc called a solar nebula. Our planet and others probably formed inside this disc. The center of the cloud continued to condense, eventually igniting and becoming a sun.

There's no concrete evidence for exactly how the Earth formed within this nebula. Scientists have two main theories. Both involve accretion, or the sticking together of molecules and particles. They have the same basic idea -- about 4.6 billion years ago, the Earth formed as particles collected within a giant disc of gas orbiting what would become our sun. Once the sun ignited, it blew all of the extra particles away, leaving the solar system as we know it. Our moon formed in the solar nebula as well.

At first, the Earth was very hot and volcanic. A solid crust formed as the planet cooled, and impacts from asteroids and other debris caused lots of craters. As the planet continued to cool, water filled the basins that had formed in the surface, creating oceans.

Through earthquakes, volcanic eruptions and other factors, the Earth's surface eventually reached the shape that we know today. Its mass provides the gravity that holds everything together and its surface provides a place for us to live. But the whole process would not have started without the sun.

by"environment clean generations"