Common and Hazardous Air Pollutants

America's Children and the Environment: Measures of Contaminants, Body Burdens, and Illnesses — U.S. Environmental Protection Agency— (Part 1: Environmental Contaminants / Outdoor Air Pollutants)         Particulate matter in the air (often called PM-10 or PM-2.5) has been found to cause increased risk of mortality (death), hospital admissions and emergency room visits for heart and lung diseases, respiratory effects, and decreases in lung function.       Prior to 1997, the National Ambient Air Quality Standard for particulate matter was based on particulate matter measuring 10 microns or less (PM-10). In 1997, the standard was revised to address the health risks from particulate matter measuring 2.5 microns or less (PM-2.5).       Lead accumulates in bones, blood, and soft tissues of the body. Exposure to lead can affect development of the central nervous system in young children, resulting in neurobehavioral effects such as lowered IQ.       Sulfur dioxide poses particular concerns for those with asthma, who are considered to be especially susceptible to its effects, which include respiratory illness, alterations in the lung's defenses and aggravation of cardiovascular diseases.         Exposure to carbon monoxide reduces the capacity of the blood to carry oxygen, thereby decreasing the supply of oxygen to tissues and organs such as the heart. Short-term exposure can cause neurobehavioral effects and a reduction in exercise performance.         Nitrogen dioxide effects include decreased lung function and increased respiratory symptoms or illness. Nitrogen dioxide is a major contributor to the formation of ground-level ozone, which can cause a variety of respiratory health effects and increased prevalence of asthma.         Hazardous air pollutants, also known as air toxics, have been associated with a number of adverse human health effects, including cancers, asthma and other respiratory ailments, and neurological problems such as learning disabilities and hyperactivity.         The Clean Air Act identifies 188 substances as hazardous air pollutants. Examples include benzene, trichloroethylene, mercury, chromium, and dioxin.         Hazardous pollutants are emitted from sources that are grouped into three general categories: major sources, area sources, and mobile sources.         Major sources typically are large industrial facilities such as chemical manufacturing plants, refineries, and waste incinerators. These sources may release air toxics during discharge through emission stacks or from equipment leaks.         Area sources typically are smaller stationary facilities such as dry cleaners. Collectively their emissions can be of concern — particularly where large numbers of sources are located in heavily populated areas.         Mobile sources include both on-road sources, such as cars, light trucks and buses, and non-road sources such as farm and construction equipment, marine engines, aircraft and locomotives.

The Hottest Thing in Theoretical Physics

The Unraveling of String Theory — Michael D. Lemonick— — August 2006— (Time Magazine)     Everyone knows that string theory is the hottest thing in theoretical physics. But string theory hasn't been embraced by everyone.     Physicists Peter Woit in Not Even Wrong and Lee Smolin in The Trouble with Physics both argue that string theory is largely a fad propped up by practitioners who tend to be arrogantly dismissive of anyone who dare suggest that the emperor has no clothes.       The two most important ideas of 20th century physics, relativity and quantum theory, were known to be fundamentally incompatible.         Quantum theory describes the universe as intrinsically discontinuous: energy, for example, can come in bits just so small, but no smaller. Relativity treats time and space and gravity as a smooth, unbroken continuum.             The solution: to think of the basic units of matter and energy not as particles but as minuscule, vibrating loops and snippets of stuff resembling string, which turn out to exist not just in our familiar four dimensions of space and time but in 10 or more dimensions.         This bizarre-seeming scheme appeared on first blush to explain why particles have the characteristics they do. It also included a quantum version of gravity and thus of relativity.         But: superstrings have proved a lot more complex than anyone expected. The mathematics is excruciatingly tough, and when problems arise, the solutions often introduce yet another layer of complexity.         The new, improved theory posits a nearly infinite number of different possible universes, with no way of showing that ours is more likely than any of the others.                The string theory’s idea of infinite universes is currently in vogue among some astronomers as well.           String theorists seem ready to abandon the essential definition of science. Is string theory too important to be hampered by old-fashioned notions of experimental proof?       In science, slow accretion of data and evidence eventually eliminates reasonable doubt, but not so with strings.       Nobody has any good idea of how to test string theory. Woit says, 'proposing speculative ideas is fine, but if they can't be tested, they're not science'.

General Relativity and Quantum Mechanics

The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory — Brian Greene— (Chapter 1: Tied Up with String)         There are two foundational pillars upon which modern physics rests.       One is Albert Einstein's general relativity, which provides a theoretical framework for understanding the universe on the largest of scales: stars, galaxies, clusters of galaxies, and beyond to immense expanse of the universe itself.       The other is quantum mechanics, which provides a theoretical framework for understanding the universe on the smallest of scales: molecules, atoms, and all the way down to subatomic particles like electrons and quarks.       Through years of research, physicists have experimentally confirmed to almost unimaginable accuracy virtually all predictions made by each of these theories.         But: as they are currently formulated, general relativity and quantum mechanics cannot both be right.         The two theories underlying the tremendous progress of physics during the last hundred years are mutually incompatible.         In the central depths of a black hole an enormous mass is crushed to a minuscule size.       At the moment of big bang the whole of the universe erupted from a microscopic nugget whose size makes a grain of sand look colossal.              There are realms that are tiny and yet incredibly massive, therefore requiring that both quantum mechanics and general relativity simultaneously be brought to bear.         Well-posed physical questions elicit nonsensical answers from the unhappy amalgam of these two theories.         Can it really be that the universe at its most fundamental level is divided, requiring one set of laws when things are large and a different, incompatible set when things are small?         Superstring theory: this new approach to describing matter at its most fundamental level resolves the tension between general relativity and quantum mechanics. Within this new framework, general relativity and quantum mechanics require one another for the theory to make sense.

Faraday’s Force Fields

Physics of the Impossible: A Scientific Exploration into the World of Phasers, Force Fields, Teleportation, and Time Travel — Michio Kaku— (Chapter 1: Force Fields)         In science fiction, a force field is deceptively simple: a thin, invisible yet impenetrable barrier able to deflect lasers and rockets alike.       In the same way that Edison's lightbulb revolutionized modern civilization, a force field could profoundly affect every aspect of our lives.       Bridges, superhighways, and roads could in theory be built by simply pressing a button. Entire cities could sprout instantly in the desert, with skyscrapers made entirely of force fields.       The concept of force fields originates from the work of the great nineteenth-century British scientist Michael Faraday.                  The young Faraday was fascinated by the enormous breakthroughs in uncovering the mysterious properties of two new forces: electricity and magnetism.         Faraday made a series of stunning breakthroughs that led to the creation of generators that would energize entire cities and change the course of world civilization — the key to Faraday's greatest discoveries was his "force fields."         If one places iron filings over a magnet, one finds that the iron filings create a spiderweb-like pattern that fills up all space. These are Faraday's lines of force, which graphically describe how the force fields of electricity and magnetism permeate space.         Empty space, to Faraday, was not empty at all, but was filled with lines of force that could make distant objects move.         One day in 1831, Faraday made the key breakthrough when he was moving a child's magnet over a coil of wire, without ever touching it. This meant that a magnet's invisible field could push electrons in a wire across empty space, creating a current.         Faraday's "force fields" which were previously thought to be useless, idle doodlings, were real, material forces that could move objects and generate power.         Force fields of Michael Faraday are the forces that drive modern civilization, from electric bulldozers to today's computers, Internet, and iPods.         Faraday's force fields have been an inspiration for physicists for a century and a half. Einstein was so inspired by them that he wrote his theory of gravity in terms of force fields.