SCIENCE & TECHNOLOGY

A junkyard in outer space
Radhakrishna Rao
T
he widely publicised anti-satellite test carried out by China with the help of a ground based missile in January this year, in addition to raising concern over the militarisation of outer space, has led to worry over its potential contribution to the fast-growing space junkyard.

Females first to develop weapons?
M
ales may have the brawn, but a study supports the theory that females used their brains to develop the first weapons. This was an evolution of necessity, the research released last week suggests, because females did not have the strength or leisure to compete with males for prey that could be hunted by hand. Anthropologists studying chimpanzees in Senegal have discovered that female chimps regularly gnaw down sticks and use them as spears to hunt their prey.

Animals too can think ahead
“B
ird-brained” may not be an insult after all, according to a study which shows that humans are not the only animals capable of planning for the future. In an experiment designed by British scientists, eight western scrub-jays forestalled a lack of food by stashing pine nuts the night before in a location where, during a series of two-hour morning lock-downs, they had earlier gone unfed.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE
PROF YASH PAL

Why are X-rays and Gamma rays different in nature? After all, both are forms of electromagnetic radiation.

 

 


Top






A junkyard in outer space
Radhakrishna Rao

The widely publicised anti-satellite test carried out by China with the help of a ground based missile in January this year, in addition to raising concern over the militarisation of outer space, has led to worry over its potential contribution to the fast-growing space junkyard.

In fact, anti-satellite and killer satellite tests carried out by the erstwhile Soviet Union and USA during 1970s and 1980s had made an enormous contribution to the existing mountain of space debris. And according to space experts the recent Chinese test could have yielded hundreds of large fragments. Indeed, around 800 pieces of detectable debris from fragmented satellites could go up to 1000 pieces as both the space based and ground based monitoring of space activities continues without a pause.

Of course, the number of space debris that cannot be detected run into more than 10,000. “It is inevitable. A significant piece of debris will run into an old rocket body that will in turn create more debris” says Nicholas L.Johnson, Chief Scientist for Orbital debris at the National Aeronautics and Space Administration (NASA).

Interestingly, not long back China had highlighted the need for voluntary guidelines for debris control in outer space. On its part Indian Space Research Organisation (ISRO)has suggested a number of remedial measures for minimising the generation of space debris.

ISRO Chairman G. Madhavan Nair has made it plain that Chinese killer satellite test not only poses a threat to the peace in outer space but also helps increase the volume of space debris.

Meanwhile, concern is also mounting over the space activities contributing to the environmental wellbeing. In order to obviate the problem of toxic chemicals, used in rocket stages, posing a threat to the atmospheric balance, research efforts are on to develop eco friendly fuel for use in rocket stages. Of course, the worry over the space debris posing a threat to the multimillion dollar satellite missions designed for communications, weather watch and earth observation is quite palpable.

Discarded rocket stages and parts of disintegrated satellite which have piled up in outer space over the last five decades could seriously hamper active satellite missions. As it is, a tiny speck of paint from a dead satellite had in 1980s dug a pit in a space shuttle window .In this context, researchers point out that a major challenge before the global scientific community is to develop methods to detect objects smaller than 10cm in size which are capable of inflicting mission-degrading effects on satellites.

Researchers also say that many pieces of satellites continue to stay in orbit indefinitely if they attain what is called the first cosmic speed.

Only the objects that slip below an altitude of 120-150 km re-enter the atmosphere to blaze down as unidentifiable pieces on earth.

The collision hazard posed by the space debris is mainly due to the high energy impact borne out of its rapid acceleration. While most of the space junk stems from launch activities, garbage also results from satellite and meteorite collisions.

Moreover, space missions routinely dump food items and spent oxygen cylinders into space. These debris can only make space exploration difficult in coming years.

Incidentally, most of the debris lies in the earth orbit between 200 km and 1000 km.

However, the greatest concentration of the junk is to be found in the 900 km range where most of the weather watch and earth observation satellites are positioned. The space junk in low earth orbit continues to move around till the slow wear of molecular friction and gravity cause them to enter the earth’s atmosphere and burn up into small pieces.

The growing junk belt in outer space is also known to be a hindrance to astronomical observation. “Space junk is already a real hazard to ground-based astronomy” says an astrophysicist. 


Top

Females first to develop weapons?

Males may have the brawn, but a study supports the theory that females used their brains to develop the first weapons. This was an evolution of necessity, the research released last week suggests, because females did not have the strength or leisure to compete with males for prey that could be hunted by hand. Anthropologists studying chimpanzees in Senegal have discovered that female chimps regularly gnaw down sticks and use them as spears to hunt their prey.

Many animals have been known to use tools but this was the first time researchers observed an animal using a weapon to hunt. It shows that chimps are closer to humans than previously thought.

While the use of a primitive spear was observed as a regular habit among females and immature male chimps, it was rarely used by full-grown males who were strong and quick enough to hunt bigger animals. “It’s just not a male behaviour,” lead researcher Jill Pruetz, a professor of anthropology at Iowa State University, said in an interview.

The scarcity of available protein, and the resulting refusal of adult males to share the meat from the monkeys they caught, may have encouraged the female and adolescent chimps to develop tools to hunt smaller and more agile prey that was mostly ignored by the adult males, she explained.

“Females will have to come up with creative ways at getting at a problem whereas males have brawn,” Pruetz said. Chimpanzees are the closest living relatives to humans and savanna chimps can provide insight into the behaviours of human ancestors because they live in a similar environment and have similar characteristics. — AFP 

Top

Animals too can think ahead

“Bird-brained” may not be an insult after all, according to a study which shows that humans are not the only animals capable of planning for the future. In an experiment designed by British scientists, eight western scrub-jays forestalled a lack of food by stashing pine nuts the night before in a location where, during a series of two-hour morning lock-downs, they had earlier gone unfed.

The birds stocked only a third as many goodies in a second location where they had, by contrast, been allotted morning meals on alternate days during the previous week. “The birds behaved as if they were planning for breakfast by caching food items in the place where the food was most likely to be needed,” observed Sara Shuttleworth, a professor of psychology and zoology at the University of Toronto who wrote a commentary in Nature, which also published the study.

To truly demonstrate the capacity to think ahead, she said, the birds needed to fulfil two criteria.

They had to demonstrate a novel action, ruling out deeply ingrained behaviour such as migration and hibernation, and they had to show the capacity to anticipate a “motivational state” — in this case, hunger — that they were not experiencing at the time. The scrub-jays had had plenty to eat when they set about stocking the larder for the morning after.

“Knowledge of and planning for the future is a complex skill that is considered by many to be uniquely human,” write the authors, led by Caroline Raby.

“The results described here suggest that the jays can spontaneously plan for tomorrow... thereby challenging the idea” that only humans are able to think ahead. — AFP

Top

THIS UNIVERSE
PROF YASH PAL

Why are X-rays and Gamma rays different in nature? After all, both are forms of electromagnetic radiation.

My first reaction to this question was to tell the person asking it to first understand what is electromagnetic radiation and if he does that the answer to his question might become obvious. But knowing that a child studying in class 9 has asked this question, such a response would be silly. It would take him/her a few years to get to that stage. Somehow I do not like such complete postponements. Perhaps using simple language and avoiding too many technical words could provide some understanding and this might kindle an interest in pursuing this subject a few years later.

First let us look at various forms of electromagnetic radiation. When we think a little we will realize that we are not looking at different types of animals. It might appear that way when I tell you that radio waves, light or heat from the sun or, for that matter, from an electric bulb, are all electromagnetic radiations. So are X-rays and Gamma rays. It turns out that the primary difference between all these forms of radiations is that they differ in wavelength. Radio waves have long wavelength, which decreases as we go down to heat waves, visible light, ultra-violet, X-rays and Gamma rays. There are no bounds on either side. It is amazing that this single parameter makes all the difference. In the optical range the wavelength changes roughly by a factor of two in going from red to indigo! The velocity of all these waves in vacuum is the same.

A revolutionary development right in the beginning of nineteenth century finally brought electromagnetic theory in line with observations. This was the suggestion that the energy in radiation is in the form of packets whose measure is proportional to the frequency of the radiation, frequency being the ratio of the velocity of light and wavelength. This was the famous hypothesis of Planck who introduced a constant of proportionality “h” in the theory. As a result the size of the energy packets in which the radiated energy is produced increases as the frequency of radiation increases. This is the reason that Gamma rays come in packets larger than X-rays and so on down the line. These packets or quanta, as they are called, determine the manner in which radiation interacts with matter. As a result X-rays are more penetrating than light, and Gamma rays even more. This effect is also responsible for our being able to distinguish between the colours of the light spectrum.

When water is boiled it changes into oxygen and hydrogen. But if we hold a burning stick above the steam the same oxygen and hydrogen, instead of instigating fire, extinguish the burning stick. Why?

We cannot produce oxygen and hydrogen just by boiling water. Steam is just a gaseous form of water. The process of boiling does not provide enough energy to break the bond between hydrogen and oxygen atoms in a water molecule. We can, on the other hand, produce hydrogen and oxygen by passing an electric current through water. This is called the process of electrolysis.

Top


HOME PAGE