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An eye on dark matter Use of sonar by navies killing dolphins Why the bad boys get the girls
THIS UNIVERSE
Prof Yash
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An eye on dark matter NASA’s latest adventure, the Gamma-Ray Large Area Space Telescope (GLAST), successfully launched on June 11, is a special eyeglass to investigate gamma-ray events in space. Launched on the DELTA II rocket from Cape Canaveral Air Force Station in Florida, GLAST would start scientific operations after a 60-day initial check-out and calibration period. The human eye has its limits. It can see light only if it falls under a specific optical length, which is 400 nm to 750 nm. Any light whose wavelength is more or less than this cannot be visualised. But our universe is composed of all forms of light like gamma-rays, radio waves, infra-red, ultra violet etc. The categorisation of light is based on the energy of the rays. Our atmosphere blocks high energy gamma-rays, some ultraviolet rays and infra-red light produced from various events taking place in the universe. David J. Thompson, GLAST Deputy Project Scientist, in an e-mail to this correspondent, said that the main objectives of GLAST are to explore the most extreme environments in the universe, where nature harnesses energies far beyond anything possible on Earth, to search for signs of new laws of physics and what composes the mysterious ‘Dark Matter.’ Dark Matter is estimated to constitute 22 per cent of the universe’s energy contents, but still eludes astrophysicists. Supersymmetry theory posits that it is composed of WIMPS — Weak Interacting Massive Particles — and GLAST will try to verify its existence. Thomson further said that the observatory would also seek to explore how black holes accelerate immense jets of material to nearly light-speed and crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts. GLAST will focus only on gamma ray events, where it is important to study all forms of light. Thomson clarified that the telescope project will work cooperatively with astrophysicists of all types. “We are particularly looking forward to the upcoming launch of the ASTROSAT mission by India, because ASTROSAT has several types of telescopes. We expect to organise cooperative efforts between GLAST and ASTROSAT science teams,” he added. Lynn Cominsky, Professor and Chair, Department of Physics and Astronomy and Director, NASA Education and Public Outreach at Sonoma State University, said in an e-mail that GLAST is 30 times more sensitive, with better angular resolution, broader energy range, wider field of view and more complete sky coverage, than the last similar mission, EGRET, on the Compton Gamma Ray Observatory. This $890 million telescope is a joint effort of France, Germany, Italy, Japan, Sweden and
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Use of sonar by navies killing dolphins More than 25 dolphins were found stranded recently in four different river creeks on the River Fal estuary in Cornwall, UK. A pod of many more dolphins was attracted to the area following the stranding. They were apparently lured there by the distress calls of the others but were successfully led to safety by coastguards. Neil Oliver, a Falmouth coastguard, said: “Initially, one dolphin swam up and got disorientated in shallow water. It put out a distress call and it looks as though the others have followed and thought ‘we’ll find out what’s going on’.” Scientists have gone to great efforts in trying to understand mass stranding but there appears to be no single explanation. The species involved in the Falmouth episode is the common dolphin but mass strandings occur in many other species of cetaceans (dolphins, porpoises and whales). Liz Evan-Jones, a zoologist at the Natural History Museum in London, said a mass stranding could occur because of sickness, disorientation of a pod leader, natural mortality, extreme weather or injury. Mass strandings are also thought to result from the use of naval sonar. Another possibility is that the dolphins may simply have been caught by fishermen and thrown overboard either dead, dying or disorientated. “Whales and dolphins strand themselves for a number of reasons and we are not sure yet what happened with these dolphins. We haven’t had a mass stranding in the UK since 29 cetaceans were seen floating in Dorset in March 2003,” said Dr Evans-Jones. “Many different types of cetaceans strand themselves. In the past we’ve recorded harbour porpoises, white-sided dolphins, common dolphins an also whales beached along Cornish coast.” Strandings have been recorded throughout history. It appears that mass strandings are increasing, or are at least more widely reported, but this may be because of better and faster communications rather than an absolute increase in their number. The Natural History Museum’s records show there has been at least one stranding involving 100 or more animals since 1913. Worldwide, mass strandings seem to be becoming more common, but again this may be due to better reporting — or possibly because of the wider use of sonar by navies around the world. The navy confirmed yesterday that it was on exercises in the area. One the strongest pieces of evidence was published in 2003, when scientists examined 14 beaked whales found beached in the Canaries in an area where a Spanish naval exercise took place in 2002. The scientists found that sonar could induce a condition similar to decompression sickness in the stranded whales. “The link between military sonar and stranded sea mammals has been established. Our study suggested a potential mechanism,” Paul Jepson, of the Institute of Zoology in London, said at the time. Dissolved gases in the blood of the stranded whales appeared to have come out of solution to form tiny bubbles in the liver and other vital organs — leading to the effects of decompression sickness. Until then, it was thought that whales and dolphins could not get the “bends” but the scientists believe this is indeed the case when the animals are forced to come to the surface too quickly, for instance, if they are startled by a loud underwater explosion. “A small number of stranded animals had gas bubbles and associated tissue injuries,” Dr Jepson said. “Although decompression sickness was previously unheard of in marine mammals, we concluded that a form of marine mammal decompression sickness was the most likely cause.” A further study in 2004 lent weight to the idea. Scientists at Woods Hole Oceanographic Institution in Massachusetts found evidence of decompression sickness in the bones of sperm whales. They concluded that anything which disrupted the slow ascent of the whales to the surface — such as acoustic signals from a submarine — could increase the risk of this sort of tissue damage. —
The Independent |
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Why the bad boys get the girls Bad boys, it seems, really do get all the girls. Women might claim they want caring, thoughtful types but scientists have discovered what they really want — self-obsessed, lying psychopaths. A study has found that men with the “dark triad” of traits — narcissism, thrill- seeking and deceitfulness — are likely to have a larger number of sexual affairs. Peter Jonason, of New Mexico University in Las Cruces, believes that these traits may have an innate, genetic component that explains why some men seem unable to stop themselves behaving badly. The dark triad of traits are the self-obsession of narcissism, the impulsive, thrill-seeking and callous behaviour of psychopaths and the deceitful and exploitative nature of Machiavellianism. “We have some evidence these traits may represent a successful evolutionary strategy,” Dr Jonason told New Scientist magazine. Many famous men — from James Dean to Pete Doherty — could be said to show elements of the dark triad of traits, but perhaps the best fictional example is James Bond. “He’s clearly disagreeable, very extrovert and likes trying new things — including killing people and new women,” Dr Jonason said. The study subjected 200 college students to personality tests designed to rank them in terms of the dark triad. They were also asked about their sexual relationships, including their attitude towards brief affairs. Dr Jonason said those with the highest rating in terms of the dark triad tended to have more partners and a greater desire for short-term affairs. The dark triad approach is one way of maximising a man’s reproductive potential by having sex with many females, while not bothering to stick around to help with the children. “The strategy seems to have worked. We still have these traits,” Dr Jonason said. —
The Independent |
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THIS UNIVERSE You seem to be referring to a stage of stellar evolution when the star becomes a Red Giant. The reason for this is understood in the following way: Let us start with a star the size of our Sun. Like all other stars it started generating its energy through thermonuclear reactions at its centre. For every self-gravitating body the centre is the hottest place. When the temperature reached close to 15 million degrees the thermal velocity of ions was high enough to overcome the electrostatic repulsion of positive ions – mostly protons. (We are mentioning protons because hydrogen happens to be the most abundant element). Through a set of reactions we end up in situation where fusion of four protons leads to production of a Helium nucleus. This is the basic fusion reaction in which most of the energy of the Sun is produced, the basic reason being the fact that mass of a helium nucleus is substantially less than the mass of four protons. For completeness sake I might mention that in addition to helium nuclei you must produce some positrons and neutrinos. While the positrons are locally absorbed through annihilation the neutrinos, being weakly interacting, escape right out of the Sun. In fact the flux of these neutrinos gives a measure of the internal temperature of the Sun! But let us get on with our story. The sun has been shining for 4.5 billion years and busily eating up the hydrogen in its core and producing helium. It is estimated that it could go on doing that for another 3-4 billion years. But then the hydrogen at the core will be depleted and then finished. The radiation pressure at the core would fall leading to a contraction that would result in an increase of temperature. Some fusion of helium into higher elements might also begin, but the descent of upper layers into the hotter region below will bring about a qualitative change in the character of the solar furnace. This is due to the fact that the upper layers of the sun would not yet be depleted of hydrogen. Fusion of hydrogen into helium now begins in these higher layers on which the overlying pressure is not so high. Burning hydrogen therefore pushes up and inflates the outer part of the sun into a balloon that could expand enough to swallow nearby planets, including the earth. The temperature would be three/four thousand degrees, enough to evaporate all our oceans and incinerate every thing on the ground. Temperature of about 3000 degrees would make the bloated sun shine in red colour. Our sun would have become a Red Giant. Why does Saturn revolve around the sun and not around Jupiter? According to Newton’s law of gravitation the force of gravity decreases with the distance. Jupiter is very large and it must be having more gravitational pull on Saturn and other planets beyond that? You have to remember that the Newton’s law also says that in addition, it depends on the product of the masses. So do a little sum. Look up the masses of the Sun, Jupiter and Saturn and do a little arithmetic. You will find out that the Sun wins out. It is so much bigger. What is the reason behind the shifting of earth plates, which is responsible for earthquakes? The earth deep below is very hot and even rocks and metals are in a liquid state. Due to convection this material rises and falls, the way liquid in a beaker heated over a gas stove would. The heat inside the earth comes from gravitational falling of heavier material as also from radio activity. These moving currents of matter carry the solid crust with them. Rotation of the earth is also implicated. This is believed to be the reason for movement of plates. Which forces are acting on a person ascending in an elevator? Why is the formula used to calculate this force described as total mass of lift (acceleration of lift + acceleration due to gravity);i.e. m(a+g) I am very pleased that you asked this question. It is true that the force acting on the floor of the lift will be m(g+a) mg is the force due to your weight even when the lift was stationary while (m a) is the force due to the fact that the lift is accelerating. In other words, the formula you have given is correct. (Incidentally if the acceleration ‘a’ was equal to - g, you and the lift would be both be in free fall and become weightless, because you would not be exerting any force on the floor). The reason I am delighted with your question is that you have noticed that the mass that is influenced by gravity and the mass that defines the inertia of a body, and gives the value of a force when multiplied by acceleration is taken as the same. In other words, why the gravitational mass and the inertial mass be the same? This is an assumption that gives a special place to gravity. There have been several scientific and philosophical discussions on this. Several deep and difficult experiments have been done to detect a slight difference between these two masses. Perhaps the very existence of mass and gravity is intimately connected. Do not lose the habit of such wondering. |
By Bhartesh Singh Thakur
