forces or those of our allies, under single or joint control. As a major illustration important both for defense and foreign policy, I shall treat the particularly stringent conditions for deterrence which affect forces based close to the enemy, whether they are U.S. Deterrence in the 1960's will be neither inevitable nor impossible but the product of sustained intelligent effort, attainable only by continuing hard choice. The balance, I believe, is in fact precarious, and this fact has critical implications for policy. Because of its crucial role in the Western strategy of defense, I should like to examine the stability of the thermonuclear balance which, it is generally supposed, would make aggression irrational or even insane. One of the most important of these assumptions - that a general thermonuclear war is extremely unlikely - is held in common by most of the critics of our defense policy as well as by its proponents. Western defense policy has almost returned to the level of activity and the emphasis suited to the basic assumptions which were controlling before Sputnik. The flurry of statements and investigations and improvised responses has died down, leaving a small residue: a slight increase in the schedule of bomber and ballistic missile production, with a resulting small increment in our defense expenditures for the current fiscal year, a considerable enthusiasm for space travel, and some stirrings of interest in the teaching of mathematics and physics in the secondary schools. (Neutrons hardly damage cells because they do not carry any electrical charge.The first shock administered by the Soviet launching of Sputnik has almost dissipated. At equivalent absorbed doses, neutrons can cause more severe damage to the body than gamma rays. The human body contains a large amount of hydrogen (a constituent of water molecules that occupy 70% of the human body), and when neutrons hit the nucleus of hydrogen, i.e., a proton that is positively charged, the proton causes ionizations in the body, leading to various types of damage. In fact, it is neutrons that trigger the nuclear chain reaction to explode an atomic bomb. Neutron particles are released following nuclear fission (splitting of an atomic nucleus producing large amounts of energy) of uranium or plutonium. X rays consist of a mixture of different wavelengths, whereas gamma-ray energy has a fixed value (or two) characteristic to the radioactive material. This was first observed by Wilhelm Roentgen in 1895, who considered it a mysterious ray, and thus called it an X ray. When high-speed electrons hit metals, electrons are stopped and release energy in the form of an electromagnetic wave. X rays have the same characteristics as gamma rays, although they are produced differently. A cobalt-60 gamma ray can penetrate deeply into the human body, so it has been widely used for cancer radiotherapy. Gamma rays are produced following spontaneous decay of radioactive materials, such as cobalt-60 and cesium-137. A gamma ray’s wavelength is far shorter than ultraviolet (i.e., it is far higher in energy). Sunlight consists of a mixture of electromagnetic rays of various wavelengths, from the longest, infrared, through red, orange, yellow, green, blue, indigo, and violet, to the shortest in wavelength, ultraviolet. Gamma raysĪn electromagnetic wave, a gamma ray is similar to ordinary visible light but differs in energy or wavelength. As with alpha rays, the major concern for health effects is after their ingestion (i.e., internal exposure). Depending on its energy (i.e., speed), a beta ray can traverse different distances in water–less than 1 mm for tritium to nearly 1 cm for phosphorus-32. Beta rays are produced following spontaneous decay of certain radioactive materials, such as tritium (an isotope of hydrogen), carbon-14, phosphorus-32, and strontium-90. Beta raysĪ particle ray consisting of a fast electron whose mass is nearly 1/2000 of the mass of a proton or neutron. Therefore, health effects of alpha-ray exposures appear only when alpha-emitting materials are ingested (i.e., internal exposure). A single piece of paper can stop an alpha ray effectively. Because of its large mass and positive charge, an alpha ray can usually pass only a short distance–less than 1 mm–in water. Alpha rays are produced following spontaneous decay of certain radioactive atoms, such as radium, plutonium, uranium, and radon. A particle ray consisting of two protons and two neutrons (namely, a nucleus of helium).
0 Comments
|
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |