pp 623-623 Editorial
pp 626-626 Science Smiles
pp 627-631 Article-in-a-Box
pp 633-643 General Article
Light was assumed to propagate in a medium called etherwhich was all pervading and stationary. Earth’s motionthrough ether was expected to have an effect on the velocityof light in the direction of the relative motion by the law ofaddition of velocities. Michelson–Morley experiment used aninterferometric technique to detect this effect and got a nullresult, which was the first strong evidence against existenceof ether and eventually had a natural explanation in specialtheory of relativity.
pp 645-657 General Article
Stars, other than the Sun, appear to our unaided eyes aspoints of light. Large telescopes show an image whose sizeis dictated by refractive index irregularities in the Earth’s atmosphere.The size of this blurring is much greater than thatof the star, and hence it is difficult to measure the stellar size.Fizeau showed how one might overcome this limitation usingthe two-slit interference technique. It was Michelson whocarried out this programme and made the first direct measurementof the giant star Betelguse in the constellation ofOrion. His value for the angular diameter, 47 milliarcsecondsor 2.6×10−7 radians, was completely confirmed by laterwork following his methods. The key concept introduced was
‘fringe visibility’, which turned out to be very fruitful in thelater development of optics as well as astronomy.
pp 659-676 General Article
Second law of thermodynamics can be apparently violated insystems whose dynamics depend on information acquired bymeasurement. However, when one considers measurementand erasure together with the system, it saves the second law.We consider the simple example of an information machine,where information is used as a resource to increase the machine’s performance. The system is connected to two baths, awork source, and a moving tape which is used as an informationreservoir. The performance of the device is autonomous.The system acts as an engine, erasure or refrigerator. Evencombination of any two is possible. All these possibilities areallowed by the generalized second law.
pp 677-690 General Article
Snow leopard, an elusive mammal species of the cat family,is the top-predator of the Central and South Asian, highaltitudeecosystem. Snow leopards occur at low densities acrossthe Central Asian mountains and the Indian Himalayan region.Owing to their secretive nature and inaccessible habitat,little is known about its ecology and distribution. Due toits endangered status and high aesthetic value, the snow leopardis considered as an ‘umbrella species’ for wildlife conservationin the Indian Himalayas. This article summarizes thecurrent knowledge on snow leopard ecology and conservationissues in the Indian context.
pp 691-696 General Article
The most common plasticizer, phthalates, are facing stricterregulations due to their omnipresence and possible effects onhuman health, and environment. But high cost, lack of applicationrange, and unknown long-term effects of non-phthalatealternatives make the scenario puzzling.
pp 697-703 Classroom
In this series of articles, the authors discuss various phenomenain fluid dynamics, which may be investigated via tabletopexperiments using low-cost or home-made instruments.The fifth article in this series is about some fascinating experimentswith non-Newtonian fluids.
pp 705-714 Classroom
The formula for the shortest distance of a point from a linecan be derived in several different ways. Some typical methodsare taught at the elementary (i.e., high-school and juniorcollege) level. However, solving such ‘school-book’ problemsusing advanced mathematical methods is often overlookedand neglected. This article illustrates how this formula canbe derived in various ways. Such a comparison will not onlyencourage the reader to explore and understand how andwhy mathematical techniques work, but it will also help understandthe common thread between different branches ofmathematics. This exercise also shows that ‘the best way’ tosolve a mathematical problem is a misnomer.
pp 715-715 Information and Announcements
pp 716-716 Information and Announcements
pp 717-717 Information and Announcements
pp 718-718 Information and Announcements
pp 719-719 Flowering Trees