“The unleashed power of the atom has changed everything except our way of thinking. We need an essentially new way of thinking if mankind is to survive.” – Albert Einstein
The German physicist Wilhelm Röntgen was the first person to observe X-rays, on November 8th, 1895. It was a significant scientific advancement that would revolutionise medical investigation, by making the invisible visible.
Röntgen’s was testing whether cathode rays could pass through glass. He noticed a glow coming from a nearby chemically coated screen. He named the rays that caused this glow X-rays because their nature was unknown.
X-rays were found to be electromagnetic energy waves (radiation) which even though were similar to light rays, had wavelengths approximately 1,000 times shorter than those of light. Roentgen sat in his laboratory and carried out a series of experiments to gain a better understanding of the significance of his discovery. He was astonished to find that X-rays could penetrate human flesh. But they could not penetrate higher-density substances such as lead or bone, and that they could be photographed with clarity. This is the reason why bones appear white on the x-ray, soft tissue appears in shades of gray, and air appears black.
The scientific community hailed Roentgen”s discovery as a medical miracle.
Soon X-rays became a very important tool in medical diagnosis as they enabled doctors to see human flesh and bones without surgery for the first time. Two years later, X-rays were first used, on a military battlefield, to locate broken bones and bullets inside the bodies of patients.
While scientists immediately rejoiced in the fantastic benefits of of new medical marvel they did know about the harmful effects of this radiation. Initially, scientists believed that X-rays passed through flesh as harmlessly as light. However, during the following years scientists began to notice cases of burns and skin damage in those exposures to X-rays. In 1904, assistant of the great inventor Thomas Edison’s assistant, Clarence Dally, who had worked extensively with X-rays, developed skin cancer and died. This made scientists to begin taking the risks of radiation more seriously.
However the phenomenon wasn’t fully understood. On the contrary from the 1930s, for about 20 years many American shoe stores sold shoe-fitting fluoroscopes that used X-rays which enabled customers to see the bones in their feet; however in the late 1950s this practice was considered to be fraught with risks, and discontinued.
Wilhelm Röntgen received numerous honours for his work, he was the first recipient of the first Nobel Prize for physics in 1901. However being modest he never tried to patent his discovery. Today, X-ray technology is widely used in medical diagnosis, material analysis and many other devices such as airport security scanners, in almost every airport in the world. Despite the invention of advanced tools like MRI, PET SCAN, and CAT Scan, X Rays are still regarded as useful in diagnosis.
Scientists as well as economists believe that nuclear power would soon prove to be a salvation for our energy-starved planet.
They are hopeful that by exploiting the power of the atom, we would be able to meet the future energy requirements as our present resources are drying up fast.
But, at the same time, we continue to be haunted by doubts. This is because, of the fact that an operating nuclear power plant does produce very small amounts of radioactive gases and liquids. It also produces small amounts of direct radiation. An average radiation dose of about 0.01 millirem per year, would be received by people living within 50 miles of a nuclear power plant.
Today, very word ‘radiation’ conjures up visions of people afflicted with leukaemia groping under the debris in devastated cities, like Hiroshima and Nagasaki strange monsters that send Geiger counters rattling, and mushroom clouds that loom large over the horizon spelling disaster.
One popular misconception is that radiation is ‘man-made’ and therefore more dangerous than power derived from natural sources. On the contrary, natural radiation is much more harmful than anything man can produce. The radiation of the sun is so intense that it can destroy all life on this planet in the absence of the ozone shield of the atmosphere or the earth’s magnetism. (The former blocks ultraviolet rays and the latter traps most of the deadly nuclear particles coming from the sun.)
Several times in the past the ozone shield has broken down, exposing the earth to the full blast of solar particles possibly resulting in destruction of many species of life. The threat to life due to another breakdown of this shield cannot be underestimated.
Potentially harmful natural radiation comes from even such common sources as brick walls of our homes, the granite stones and the radon gas that percolates into our water from deep wells and springs. People living at high altitudes are naturally more exposed to higher-level doses of radiation than sea dwellers and, hence, to greater risk of cancer.
Quantum mechanics suggests that radiation can be viewed either as particles or waves, for it exhibits both kinds of behaviour. (Radiation is a form of energy that comes out of atoms at speeds up to 1,86,000 miles per second.)
Matter consists of atoms which, in turn, are made up of different kinds of particles (more than 100 of them have so far been discovered). While many atoms are normally stable, others behave like houses of cards which collapse with the slightest push or even of their own accord. The stability of an atom depends on the ratio of two kinds of particles in its nucleus: protons and neutrons. Uranium 235 has 92 protons and 143 neutrons—the 235, representing the sum of the two kinds of particles. Currently all nuclear power is currently produced by precisely controlling the rate at which nuclear reactions occur. This is also the manner in which Nuclear Power Plants function at present.
Occasionally a nucleus of U235 disintegrates giving out nuclear fragments, single particles (particularly neutrons) and other kinds of radiation, of which ‘heat’ is the useful part. If other U235 atoms happen to be in the neighbourhood (as in a nuclear reactor), the neutrons clash against atoms nearby and cause them to break up, producing still more neutrons as well as heat resulting in a ‘chain reaction’.
Nuclear weapons, on the other hand, are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction will lead to an explosive energy release. High quality, highly enriched fuel exceeding the critical size and geometry necessary in order to obtain an explosive chain reaction, is used to manufacture a Nuclear weapon, such as an Atom Bomb. All these phenomena follow logically from Einstein’s, mass -energy equation E = mc2 ( ‘ M’ represents mass, ‘C’ represents the velocity of light, and ‘E’ represents ‘Energy’). According to the equation energy and mass (matter) are interchangeable; they are different forms of the same thing.
Atoms like U 235 that undergo fission due to their lack of stability are called radioactive, since they emit radiation.
All living organisms have absorbed radioactive substances from the environment; this radioactivity lodges in their bones or shells and after death decays very slowly. From the rate it dies out, scientists calculate the age of fossils by measuring the residual radioactivity.
Decaying or excited atoms give out positively charged protons, neutrons (which have no charge) the nuclei of helium atoms (alpha-particles) and negatively charged electrons (beta-particles). These particles may have strong effects on living organisms depending on the number of particles in a beam of radiation as well as the speed of the particles.
Apart from particles another kind of radiation (waves of pure energy) is also given out by atoms. In order to imagine these radiation waves, you may visualise a rope stretched between your hand and the branch of a tree. By shaking the rope up and down, you can produce a wave that will travel along the rope to the branch and also make it move up and down.
Increasing the rate of shaking increases the number of waves reaching the branch in a given period of time, thus increasing the ‘frequency’ of the waves. Changing the frequency of the waves of a rope may have little practical effect, but altering the frequency of the waves, carrying radiation energy radically changes the nature of the radiation itself. When a steam of energy is shaken 60 times a second (as by an electric generator), a 60 cycle alternating current (radiation) comes out of the wall plugs through the wires. When shaken 10,000 times a second, the energy is transformed into long wave radioactive radiation which can travel great distances through empty space (no metal wires are needed).
If shaken at about one billion cycles per second the radiation becomes a microwave signal of the kind used in radar or for television broadcasting or roasting food in microwave ovens. This kind of radiation may be used in the future to convey solar energy from satellites to terrestrial power plants. When the frequency is increased further, the radiation becomes infrared light, the kind that radiates heat from glowing objects. When the frequency reaches 100 trillion ‘shakes’ a second the radiation becomes visible light.
Further increase in the frequency changes the colour of the light from red to violet and then the radiation moves out of the visible range into the ultraviolet region. Up to this point all the radiation tends to have mainly a heating effect on the things that absorb it. Radiation of low frequency shakes up molecules just as a waving rope moves the entire branch to which the rope is tied and the motion of a molecule, called kinetic energy, is known as heat.
Beyond the ultraviolet frequency range some other developments take place. The waving energy rope breaks the molecules up (instead of merely shaking them) by making them lose or gain the electrons that had cemented them together. Electron-rich or electron-poor atoms are called ‘ions’. Radiation which rips a molecule apart is called ionising, and radiation becomes much more intensively ionising as frequencies increase to ‘hard’ ultraviolet, then to X-rays, gamma- rays (which are emitted by some radioactive atoms) and the cosmic rays that come to us from the cores of super hot stars in outer space.
Intensive ionising radiation may have been responsible for the chemical reactions in the primordial soup in the earth’s early oceans billions of years ago—the reactions that had led to the formation of the complex molecules from which life arose.
All life is based on carbon and energy is required to string carbon atoms into long chains and other structures from which we are all built. This energy comes as radiation from the sun, especially the visible light that powers the chlorophyll molecules in plants. Plants manufacture sugar chains (which are the first link in the food chain that sustains all animals) using only simple carbon dioxide and water as raw materials.
Scientists believe that radiation has also played a crucial role in evolution. Life is based on cells. The manner in which a cell grows, shapes itself and reproduces is determined by the coded instructions built into complex chemical molecules that function like a magnetic or punch card programme in a computer. However, this programme is actually a large and fragile chemical molecule which can be chipped or broken by outside forces such as ionising radiation. Since the world is constantly exposed to natural ionising radiation, the chemical programme in a cell frequently gets ‘changed’ by such radiation. Therefore, when the cell reproduces its progeny would naturally reflect that change.
An alteration of the genetic code of a cell usually proves destructive. The cell may die immediately or, if it reproduces, its offspring would be mutants whose characteristics usually doom them to extinction. But sometimes a genetic change may produce a cell (or an entire organism) with some advantage over competing cells or organisms of the standard kind. If this happens, the improved version has a comparatively better survival chance leading to selective evolution of new and ‘better species. In this manner radiation actually created and developed species.
But radiation can also destroy us. Ionising radiation can penetrate deep within us and scramble genetic chemical codes. If the reproduction code of a single cell is disrupted, it will no longer reproduce systematically but will produce chaotic offspring and continue to do so. This is what happens when one is afflicted by cancer.
Scrambled genetic material may not prevent normal cell reproduction but may result in a complete organism with some defect such as a club-foot or hair-lip.
People are advised to avoid doses of radiation totalling more than five rads a year. A chest X-ray exposes a patient to between four one-hundredths of a rad and one rad. In other words, more than five exposures a year are not desirable unless unavoidable. Researchers now believe that even low doses of non-ionising radiation from radar and television signals may have some effect on living processes and advise avoiding excessive exposure.
The physiological effects of radiation have not been fully studied and assessed. There is no doubt that a proper understanding of radiation will definitely broaden our knowledge of the physical universe. Radiation technology should be approached with a great deal of caution, perhaps in the same manner that early man had approached fire whose Promethean fire is not only capable of giving light and warmth but can also cause instant death if used in an unwise and unimaginative manner.