SCIENCE & TECHNOLOGY

Safe disposal of carbon dioxide in the sea-floor
Dr S.S. Verma
A
S worries over the impact of carbon dioxide emissions on global climate change soar, researchers are increasingly searching for ways to rid the atmosphere of the greenhouse gas. But, so far, industrial-scale projects have been limited. Notable among them are: a project to build power plants that derive hydrogen from fossil fuels and sequester the carbon dioxide by-product and other separates excess carbon dioxide in natural gas extracted in sea mining operations and injects it into underground reservoirs.

Archaeologists find new origins for ancient cities
By Thomas H. Maugh II

E
xcavations
at a 6,000-year-old archaeological mound in northeastern Syria called Tell Brak are providing an alternative explanation for how the first cities may have grown. Archaeologists have thought that many cities began in a single small area and grew outward, but evidence at Tell Brak indicates that it was originally a ring of small villages that grew inward as it became a city — the opposite of the conventional viewpoint.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE 
PROF YASH PAL

My doubt is from cricket. Most of the time the Australian spinner Shane Warne gets more wickets than others do. It is by spinning the ball. What is the science behind his capability to turn the ball through spinning?
There are many spinners who can spin the ball while bowling. Shane Warne has the skill of doing it better and in a more controlled manner. In all this one also has to take the nature of the pitch into account. This is understood if you first know the reason for change in the direction of a spinning ball after it hits the ground.




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Safe disposal of carbon dioxide in the sea-floor
Dr S.S. Verma

AS worries over the impact of carbon dioxide emissions on global climate change soar, researchers are increasingly searching for ways to rid the atmosphere of the greenhouse gas. But, so far, industrial-scale projects have been limited. Notable among them are: a project to build power plants that derive hydrogen from fossil fuels and sequester the carbon dioxide by-product and other separates excess carbon dioxide in natural gas extracted in sea mining operations and injects it into underground reservoirs.

Here the dynamics between carbon dioxide and surrounding fluids are different than those in the sea floor, where the ocean keeps the fluids cool. Rather, these formations are heated by the earth’s crust, and the high temperature make the carbon dioxide less dense than the water in the surrounding rock, making it prone to rising to the surface.

Sea-floor injections: a safe, high-capacity method could make carbon sequestration more practical. A better way to store carbon dioxide is to pump it into the sea floor in liquid form. There high pressure and cold temperatures make it more dense than water in the surrounding rock, preventing it from rising to the surface.

Researchers at Harvard and Columbia Universities have proposed a new method for trapping nearly limitless amounts of carbon dioxide — a technique they say will be secure, as well as a practical option for areas located far from underground reservoirs. The researchers propose that carbon dioxide be pumped into the porous sediment a few hundred metres into the sea floor in deep parts of the ocean (greater than 3,000 meters deep), in what one of the researchers calls “a fairly simple, permanent solution.” The key was finding a “sweet spot,” where the pressure and temperature of the surrounding environment make carbon dioxide denser than surrounding fluids, thereby trapping it in place. This situation occurs at the bottom of the ocean because of a combination of high pressure and low temperatures — a fact others have also noted in proposals to store carbon dioxide in deep parts of the ocean.

The carbon dioxide, in liquid form, would be brought to the sequestration site by ship or pipeline, and piped into the sea floor with equipment like that used by the oil industry for drilling deep-sea wells. Once beneath the sea floor, the carbon dioxide would interact with the surrounding fluids and produce hydrate ice crystals, which would plug the rock pores, serving as a secondary cap on the carbon dioxide.

Over hundreds of years, the carbon dioxide would dissolve in the surrounding water, and then would only have the potential of leaking out by diffusion, a slow process that would take millions of years.

Within the next five years they hope to run a large-scale field test of this new approach. If all the known geologic reservoirs for conventional storage were useable, they could store all the carbon dioxide currently produced each year, and continue doing so for 80 years at current emission rates.

Indeed, the costs for the new sea-floor method will vary but will probably be slightly more than for land-based storage. It could, however, be more economical for areas near the ocean, especially those far from a known geological reservoir.

The cost for any method of large-scale sequestration is still unclear. Moreover, such injections would kill ocean life, and, unless sequestered in deep trenches, the carbon dioxide could be carried by currents to shallow areas, where it could reenter the atmosphere. The researchers’ insight was that injections into the sea floor could take advantage of the pressure and temperature of the ocean, while avoiding the negative side effects of earlier proposals. The need for robust, potentially inexpensive carbon sequestration schemes is enormous while it still requires more experimental validation it is potentially very important and should be considered very seriously.

Along with this, efforts should be made to identify which plants (land or ocean based) are most efficient at removing carbon dioxide through photosynthesis, and start growing them. At current levels of depletion of rain forest, and increasing production of carbon dioxide, we are burning (literally) the candle at both ends. 

Storage of CO2 will just defer the problem to future generations, while we continue our greenhouse gas emitting lifestyles. Unfortunately, we’ve already delayed long enough that even when we finish converting to sustainable energy we’re going to have to take out at least as much CO2 as we’ve already put in.

Moreover, the oceans are already becoming too acidic from CO2 for many important organisms.  Enough of the “trapped” CO2 will likely diffuse into the ocean to make the problem worse.

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Archaeologists find new origins for ancient cities
By Thomas H. Maugh II

Excavations at a 6,000-year-old archaeological mound in northeastern Syria called Tell Brak are providing an alternative explanation for how the first cities may have grown.

Archaeologists have thought that many cities began in a single small area and grew outward, but evidence at Tell Brak indicates that it was originally a ring of small villages that grew inward as it became a city — the opposite of the conventional viewpoint.

The finds provide new insight into political development in the region.

“Urbanism does not appear to have originated with a single, powerful ruler or political entity,” said archaeologist Jason Ur of Harvard University, who led the research reported Friday in the journal Science. “Instead, it was the organic outgrowth of many groups coming together.”

The city, whose name is unknown, was located in the ancient empire of Mesopotamia, which encompassed what is now Southern Iraq and Northern Syria. The nearby city of Uruk in Southern Iraq was thought to have been the oldest city in the world, but discoveries at Tell Brak suggest that it may have developed contemporaneously with Uruk.

Legend holds that the great leader Gilgamesh built the city of Uruk, and that story has long served as a model for the development of early cities.

Studying potsherds, bones and other artifacts at Tell Brak, Ur and his colleagues concluded that sometime about 4200 B.C. to 3900 B.C., habitation consisted of six distinct clusters, each with an area of five to 10 acres, scattered around what is now the central mound.

Over the next several hundred years, the population grew more dense and expanded inward until, by 3400 B.C., Tell Brak was a full-fledged urban center spreading over an area of about 325 acres.

The finds, the researchers wrote, suggest that the study of early urban areas “must accommodate multiple models for the origins of cities.”

By arrangement with LA Times-Washington Post

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THIS UNIVERSE 
PROF YASH PAL

My doubt is from cricket. Most of the time the Australian spinner Shane Warne gets more wickets than others do. It is by spinning the ball. What is the science behind his capability to turn the ball through spinning?

There are many spinners who can spin the ball while bowling. Shane Warne has the skill of doing it better and in a more controlled manner. In all this one also has to take the nature of the pitch into account. This is understood if you first know the reason for change in the direction of a spinning ball after it hits the ground.

The reason is actually quite simple. When the spinning ball hits the ground it pushes the ground in the direction of the spin. This push is possible because of the friction that the ground tends to absorb the momentum of the spin. The equal and opposite reaction of the ground gives the ball a push in the opposite direction. This is what turns the ball, often in an unexpected direction, to befuddle the batsman. The skill of great spin bowlers makes use of this aspect of dynamics.

There are other aspects of sport dynamics that skillful players and athletes use through their own discovery. There are many marvelous things we humans learn to do without understanding how we do them. This is the privilege of being human. We do not know how we get the best tunes and tones out of our vocal chords or the instruments we play. Much of art and craft belong in that category. Great bowlers are also artists and craftsmen of sorts.

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