A little about neutron stars

Our galaxy is littered with the corpses of dead stars. At the end of their useful lives, the vast majority of the stars in the Milky Way shed their outer layers and shrink to white dwarfs, dense spheres about the size of Earth. But very massive stars explode in supernovae and leave behind even denser relics, called neutron stars, which are only 20 to 40 kilometres across but weigh more than the Sun. (The most massive stars of all become Black Holes.) Since the 1960’s astronomers have observed a wide variety of neutron stars, including madly rotating pulsars that sweep radio beams across the galaxy and X-ray binaries that devour material pulled from their companion stars.

Perpetual Motion Machine

Many inventors dream of perpetual motion machines, but they are an impossible dream according to the laws of Thermodynamics.

Imagine a device that uses an electric motor to turn a wheel. This wheel in turn runs an electric generator to generate the electricity. The electricity can be used to power a house as well as the electric motor turning the wheel. Once this device is set in motion, it will continue to run forever because it supplies its own electricity as well as creates enough electricity to run a house. No more electric bills! Because this device once set in motion, would never stop. Such a device is called a perpetual motion machine. Many would-be inventors have dreamed of building a perpetual motion machine, but none have succeeded. Enough of these devices could run a city or the entire world. The inventor of such a device could solve the whole world’s energy crisis. Selling this device would make its inventor rich enough to laugh at Warren Buffet, Ambani and Bill Gates’ poverty.

Sounds too good to be true? It is!

 

First Law of Thermodynamics The first law of thermodynamics is the law of conservation of energy applied to heat engines. It states that the work output from an engine cannot exceed the energy input. The perpetual motion machine described above violates the first law of thermodynamics. The generator portion generates enough electricity to run other devices as well as power the generator. Hence once this perpetual motion machine is set in motion, it produces useful work without any energy input. Energy is being created from nothing. Free work output with no energy input violates the first law of thermodynamics. Perpetual machines described above are the Perpetual Motion Machines of the First Kind. Perpetual Motion Machines of the Second Kind The first law forbids perpetual motion machine that creates extra energy, but imagine disconnecting the portion of the machine that powers the house. The motor powers a generator which supplies the electricity needed to run the motor. Such a machine would not supply free energy, but once set in motion it would still continue to run forever. The inventor of such a machine would not make untold riches by solving the world’s energy problems. It might, however, be possible to make a living selling them as novelty devices. This second kind of perpetual motion machine does not violate the first law of thermodynamics. Is it possible? Second Law of Thermodynamics The second law of thermodynamics says that an engine or process of any type must always have an efficiency of less than 100%. A perpetual motion machine that uses a generator to power the motor that runs the generator requires both the generator and the motor to operate with 100% efficiency. This type of perpetual motion machine does not violate the first law of thermodynamics, but violates the second law of thermodynamics. It is a perpetual motion machine of the second kind because it violates the second law of thermodynamics. Not even the cleverest engineer or inventor can build a perpetual motion machine because it would violate either the first or the second law of thermodynamics, which are the fundamental laws of physics. (In other words you cannot add on to something by breaking its very base!) But who knows if we can invent metal rubber, vulcanized rubbers, powerful supercomputers, iPods®, mobiles and preventions and cures to numerous diseases, maybe, just maybe, we can invent a perpetual motion machine too.

 

You may now say that “Impossible is nothing” is not always valid!!

Particle Physics

Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. It is also called “high energy physics”, because, many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. Modern particle physics research is focused on sub-atomic particles, which have less structure than atoms. These include atomic constituents such as electrons, protons and neutrons (protons and neutrons are actually composite particles made up of quarks), particles produced by radioactive and scattering processes, such as photons, neutrinos as muons, as well as a wide range of exotic particles. Strictly speaking, the term particle is a misnomer because the dynamics of particle physics are governed by quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behaviour under certain experimental conditions and wave-like behaviour in others (they are described more technically by state vectors in Hilbert space). All the particles and their interactions observed to date can be described by a quantum field theory called the Standard Model. The Standard Model has 40 species 0f elementary particles (24 fermions, 12 vector bosons and 4 scalars), which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960’s.

Particle Accelerators

A particle accelerator is a device, which is used to project sub-atomic particles at very high speeds. High energy (of many GeV or more) beams of particles are useful for applied researches in sciences. Scientific investigations often involve collisions of heavy nuclei – of atoms like iron or gold – at several GeV.

The main principle behind particle accelerators is that they are designed to impart kinetic energy on charged particles by means of an applied electric field. When a charged particle is subjected to an electric field it experiences a force proportional to the magnitude of the field, and therefore, acceleration. Once the particles have gained a sufficient amount of energy they are collided with other particles (either matter or anti-matter) and the particles resulting from the collision are observed by a detector array. Another necessity of accelerator is that the region where particles are accelerated is kept at high vacuum to prevent them from being scattered out of beam and getting lost through collisions with gas atoms or molecules.

There are mainly two types of accelerators. Linear high-energy accelerators called Linac and circular accelerators.

The Linac uses a linear array of plates which are supplied with alternating current. Just as the particles are accelerated towards the oppositely charged plate the polarity of the plates is changed and the particles are attracted by the next plate. Due to this specially monitored AC current, a group of particles are accelerated through many plates. This is known as Resonance Acceleration. Generally there is a circular accelerator attached to Linac.

The largest Linac is at Stanford, it has a 3km long underground linear accelerator which is also claimed to be the world’s straightest object. It is an electron-positron collider.

DC accelerators, which are the simplest type of accelerators, can sufficiently speed up neutrons for nuclear reactions, Cockcroft-Walton voltage multiplier and Van De Graff generator.

In a circular accelerator particles are accelerated in spirals or curves which are almost circles (using very strong electromagnets). Cyclotrons have a single pair of hollow ‘D’-shaped plates to accelerate the particles and a single large dipole magnet to bend their path into a circular orbit. It is a characteristic property of charged particles in a uniform and constant magnetic field that they orbit with a constant period, at a frequency called the cyclotron frequency, so long as their speed is small as compared to the speed of light. Circular accelerators are preferred over Linacs because of its relatively small size and its ring topology which allows continuous accelerations.

In India, we have the IUAC in New Delhi. Doctorate students from all across the India come to perform their experiments with accelerated particles. DRDO has developed many versions of accelerators under the name of KALI. The latest accelerator was started in June 2004.