Human history can be told in terms of the history of energy. The discovery of fire, the domestication of animals, the discovery of fossil fuels, the electrification of cities, the oil wars in the Middle East, and advances in nuclear physics are all pivotal points in human history. Energy is a multifaceted concept; it is central to science and education, it plays pivotal role in economic growth, and it has a dominant position in international affairs. Conventional energy sources are major sources of environmental stress at global as well as local levels. Emissions from fossil fuels drive a range of global and regional environmental changes, including global climate change, acid deposition and urban smog. Coal mining disturbs vast areas of natural habitat, hydropower development can have significant environmental and social costs, and the exploration for and extraction of oil and natural gas can have significant impacts, particularly in sensitive ecosystems
A greenhouse gas is one of several gases that can absorb and emit longwave (infrared) radiation in a planetary atmosphere. This phenomenon is often termed the greenhouse...
Energy qualityLast Updated on 2014-03-06 16:45:22
Energy quality refers to differences in the ability of a unit of energy to produce goods and services for people. The usefulness of an energy system is determined by a complex combination of physical, technical, economic, and social attributes. These include gravimetric and volumetric energy density, power density, emissions, cost and efficiency of conversion, financial risk, amenability to storage, risk to human health, and ease of transport. No single metric of an energy system captures all such attributes. It stands to reason, therefore, that a comprehensive and balanced comparison of energy technologies should employ a range of metrics, with their strengths and weaknesses duly noted.
The most common way to measure energy is by heat content because all forms of energy can be completely converted to heat (Btus, joules, calories, kilowatt-hours). The aggregation of... More »
Human population explosionLast Updated on 2014-02-26 17:23:15
Approximately 7.2 billion humans inhabited the Earth in year 2013. By comparison, there might be 500,000 elephants of different kinds, 200,000 chimpanzees, 100,000 gorillas, 20,000 polar bears, 3,000 tigers, 2,000 giant pandas and 200 California condors. Notably, the human population has grown about ten-fold over the past 300 years and nearly four-fold in just the last century. This monumental historical development has profoundly changed the relationship of our species to its natural support systems and has greatly intensified our environmental impact, particularly regarding species extinctions. Equally amazing are the signs that, in our generation, the human population explosion is abating (Figure 1; note that, here and below, many of the values given are estimates and, after the year 2005, projections). Our numbers are expected to rise by another 50%... More »
UraniumLast Updated on 2013-12-15 23:42:25Uranium is a radioactive element that occurs naturally in low concentrations (a few parts per million) in soil, rock, and surface and groundwater. It is the heaviest naturally occurring element, with an atomic number of 92. Uranium in its pure form is a silver-colored heavy metal that is nearly twice as dense as lead and is pyrophoric when finely divided.
Uranium exhibits three crystallographic modifications as follows: alpha --(688°C)→ beta --(776°C)→ gamma. It is a little softer than steel, and is attacked by cold water in a finely divided state. It is malleable, ductile, and slightly paramagnetic. In air, the metal becomes coated with a layer of oxide. Acids dissolve the metal, but it is unaffected by alkalis.
Previous Element: Protactinium
Next Element:... More »
Complex SystemsLast Updated on 2013-10-24 15:13:11
As Science has begun to ask where the enduring features of nature come from and how they work, the answer seems to be “complex systems”. Every kind of thing and event seems to require them. As the science has advanced, and as the modern problems of economies and environmental conflicts emerge, a new kind of science is emerging that requires being very openly exploratory, using all the tools and combining all the related perspectives of others, to develop complex knowledge systems matching the variety of the complex system problems they respond to.
Systems are storms or “like storms” in many respects, complex distributed phenomena that may be either unexpectedly eventful or highly predictable. There’s still a rather wide range of opinion within science as to what complex systems are, even whether they are made of information or... More »
Public Health Statement for EthylbenzeneLast Updated on 2013-09-18 20:41:06This article is a verbatim version of the original and is not available for edits or additions by EoE editors or authors. Companion articles on the same topic that are editable may exist within the EoE.
This Public Health Statement is the summary chapter from the Toxicological Profile for Ethylbenzene. It is one in a series of Public Health Statements about hazardous substances and their health effects. A shorter version, the ToxFAQs™, is also available. This information is important because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. For more information, call the ATSDR Information Center at 1-888-422-8737.
This public health statement tells you about ethylbenzene and the... More »
Drag and drop the content to change the order of featured content. The top nine will be displayed.