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Comet threat to earth
Fiercer hurricanes
Prof Yash
Pal
This Universe
Trends
New roles for drug
Growing human lungs
Fine fabric
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Comet threat to earth
What after all is the risk to earth from asteroids and what are these? It is well known that more than 100,000 asteroids lie in a belt between Mars and Jupiter and nearly 1100 out of these can come close to earth. A 400-metre wide asteroid can now be expected to travel about 40,000 km from earth, which is roughly the altitude geosynchronous satellites orbit the earth. Astronomers believe that even at a risk of scaring the people, they are better kept well informed.
Risk of an asteroid or comet’s collision with earth is expressed by astronomers through a scale called Torino Impact Hazard. There are about 1100 large space objects straddling close to earth. Almost every 500,000th year or so any of these NEOs (Near Earth Objects) can be on head-on hit course with our planet. Not having had any such hits in recorded human history makes it difficult to comprehend its potential. Also any guesses about its probability also become a complex statistical puzzle. Normally the atmosphere cover enveloping earth burns up most small objects straying into our proximity. Yet we have distinct meteorite impact depression like Lonar lake Maharashtra now filled up and seen as a lake. Be it as it may it is necessary to keep a watch and astronomers have no option but to keep calculating and guessing. NASA has a space guard programme since 1968. It tracks NEOs over 1 km in diameter as this size would create global effects. According to Richard P. Binzel of MIT,
Cambridge, USA, “ Chances are there is no sizeable threat in the coming century but it makes sense to survey the sky to make sure” and “ If an object were discovered, the best bet would be launch a mission to try to nudge it off course”. This planning may take a decade to plan. By 2003, 60 per cent of all large NEOs were accounted for. Hence NASA turned attention to objects smaller than 1 km, which are likely to strike the earth in coming 1000 years or less. Even if such objects were incapable of causing global damage, these according to NASA are regionally quite dangerous. Poor dinosaurs and their predecessors and successors had no such enlightened far sited astronomers. Quite a few major extinctions on earth coincided with cosmic bombardments reflected in rare element enrichments in very thin rock layers. The writer is from the Geology Dept., Panjab University, Chandigarh
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Fiercer hurricanes
Hurricanes have become more destructive over the past 30 years and global warming could increase their intensity in the future, an expert has warned.
He found that both the duration of the tropical cyclones and the wind speeds they produce have risen by 50 percent along with increases in the average surface temperature of tropical oceans. “My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and taking into account an increasing coastal population, a substantial increase in hurricane-related loss in the 21st century,’’ Prof Kerry Emanuel of the Massachusetts Institute of Technology (MIT) in the United States said. In a research letter published in the science journal Nature he analysed records of tropical cyclones — hurricanes and typhoons — since the middle of the 20th century. His findings suggest that the rising sea surface temperature, thought to be due at least in part to global warming, is responsible for the increased power of hurricanes. “I have shown that they have become more destructive over the last 30 years. This particular hurricane energy measure is very well correlated with the surface temperature of the tropical oceans. That temperature has an upward trend. It has increased by about half a degree Centigrade over the last 50 years,’’ Emanuel explained in an interview. Many climatologists believe the rise in sea surface temperature is a signal of global warming.
— Reuters
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This Universe
Some years ago why did the Russian Mir space station fall to the earth?
Mir did not fall to the earth unassisted. It was de-orbited, which is to say that its orbital velocity was changed by firing rockets. A lower centrifugal force led to the descent of the space station. As the density of the atmosphere increased, so did the frictional force. The descent became faster, frictional forces tore the station apart and much of it disintegrated and burnt up like a meteor in the heat that was generated. The larger pieces that survived atmospheric entry fell into the ocean. To a large extent, it was a controlled descent (though nowhere as well controlled and gentle as the landing of the space shuttle, but controlled nevertheless) because it was necessary to avoid populated areas of the earth from a shower of debris from the skies. Hidden in your question, I think, is another one. Why did it become necessary to bring down a space station that had been going around the earth for so many years? A space station needs continuous maintenance. Not being at very high altitude (less than three hundred kilometers, perhaps), it was subject to frictional deceleration by the small amount of air still present at that altitude. There were the perturbations caused by the pressure of the solar wind on its body and the solar panels. It also needed to change its orientation to meet the requirements of various scientific and other functions. Then there were other requirements. For the sustenance of the astronauts, Mir had to be serviced by a continuous stream of supply ships; it was a small habitation, most of whose requirements had to be met through transportation from the earth. The
control systems and computers had become dated and needed repairs and maintenance. The Russians felt they could not afford to go on maintaining this station and simultaneously meet their commitments for the International Space Station being set up in collaboration with the Americans, the Europeans and the Japanese. That is why the Mir station had to be laid to rest. It could not be left there because it would have come down in any case if left unattended. To allow that would have been dangerous and irresponsible. Most substances melt when heated, but why does our scrambled egg turn from liquid to solid as we cook it? Heat, in reality temperature, is a measure of the energy of molecules of substances. Higher the temperature higher is their random velocity, or velocity of vibration. Therefore with rise of temperature molecules can overcome their binding forces. Solids tend to become liquids. But they can also overcome the barriers that separate different families of molecules. It becomes easier, therefore, for them to combine with each other and produce newer forms of molecule. In other words the rate of chemical reactions increases. This is precisely what happens when you heat a raw egg through boiling or frying. The solid form is the result of new molecular substances that have a right to be
different — they can also be in a solid state.
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Trends
For thousands of years, people have been coaxing other creatures into doing chores. Now, a team of scientists has microsized the strategy. They’ve devised a way to make single-cell algae bear loads over distances of several centimeters — a tactic that the researchers say could prove useful in tiny machines.
Algae and other single-celled organisms power their movements with molecular motors. Scientists have long coveted these motors for use in micromachinery, notes chemist Douglas B. Weibel of Harvard University. However, pulling the devices from cells and modifying them to work with lab-derived machinery would require sophisticated bioengineering techniques. To avoid that hurdle, Weibel and other scientists led by George M. Whitesides of Harvard tried something simpler. The team recruited entire organisms, leaving their motors in place. New roles for drug
The test for the boys and girls was simple: to cover as much ground as they could in 6 minutes. But these children, ages 5 to 18, had pulmonary hypertension-high blood pressure in their lungs from constricted blood vessels. Such kids “don’t have a lot of energy,” explains pediatric cardiologist Tilman Humpl. “They can’t exercise at all. They may not be able to walk up from the basement to the first floor.” During the test, the 14 children walked, on average, 278 metres, about half of what a healthy young person would walk at a comfortable pace. But 6 months later, after treatment with an experimental drug, the same kids averaged 443 meters during the time. “That’s a huge increase for a patient with that disorder,” says Humpl, of the Hospital for Sick Children in Toronto. What’s more, the treatment seemed to extend the children’s lives. The drug that Humpl credits with making the difference is just now making its debut in children, but it’s already been used by some 20 million adult men. Named sildenafil citrate, it’s better known as Viagra. Growing human lungs
Scientists have successfully converted human embryonic stem cells into lung cells, taking a first step towards building human lungs for transplantation. According to research to be published in the journal Tissue Engineering, the team from Imperial College London, took human embryonic stem cells and “directed” them to convert into the type of cells needed for gas exchange in the lung, known as mature small airway epithelium. Dame Professor Julia Polak, from Imperial College London, who led the research team, says: “This is a very exciting development, and could be a huge step towards being able to build human lungs for transplantation or to repair lungs severely damaged by incurable diseases such as cancer.” Fine fabric
Scientists have come up with a way to efficiently produce thin, transparent sheets of carbon nanotubes that are several metres long and could have applications as diverse as automobile windows that double as antennas and electronic displays that can bend like paper. Nanotubes, minuscule cylinders of carbon atoms just a few nanometers across, are lightweight and stronger than steel, and they can conduct electricity. Now, Ray H. Baughman of the University of Texas at Dallas and his colleagues have developed a way to produce sheets of nanotubes with an ease and speed that could make their manufacture commercially viable.
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Tsunami resulting from quakes is common knowledge. Not many know an asteroid plunging into oceans can cause circular tsunamis, which can travel quite high on most continents. An asteroid impact on land can also cause such a holocaust as to be easily confused with a nuclear attack and accidentally trigger retaliation on an innocent enemy.