Electromagnetic Radiation and Human Health

EMF Protection

This ebook is the complete guide to learning about electrical sensitivity and how to prevent getting it in your life. You will learn what electrical sensitivity is, and what causes it. Once you have started learning about it you will learn how to get rid of it and protect yourself from the dangers of electrical sensitivity. You will also learn how to heal yourself. This book is the product of careful research by the scientific and medical communities into the dangers and preventative measures of electrical sensitivity. ES is one of the most under-diagnosed conditions in the world right now, and this ebook is designed to education people as to how it works and how to prevent it. Do not let it take hold of your family; take control and prevent it now! Do not let yourself get any more hurt; learn about this condition and fight it! More here...

How To Beat Electrical Sensitivity Summary


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Electromagnetic waves and photons

Electromagnetic waves are disturbances in equilibrium static electric and magnetic fields, which for convenience can be taken as zero in the absence of charges and currents. The waves which are of interest to astronomers are mainly electromagnetic, with frequencies ranging from radio frequencies of the order of 106 Hz to Y -rays with frequencies greater than 1018 Hz. Today, one could add two additional types of wave - neutrinos and gravitational waves - but these are not the subject of this book. The identification, by means of their velocity, of light and radio waves as manifestations of electromagnetic waves predicted by J. C. Maxwell was one of the greatest triumphs of nineteenth century physics. The basic derivation of electromagnetic waves from Maxwell's equations, as we express it in vector notation today, is given in Appendix A. The telescope is a device which concentrates the electromagnetic radiation from a distant source onto a detector. The detector is usually an imaging...

Electromagnetic radiation

Astronomers learn about the cosmos through the study of signals arriving at the earth in the form of electromagnetic radiation or as neutrinos, cosmic rays, meteorites, and, hopefully in the near future, gravitational waves. Electromagnetic radiation travels at speed c and can behave either as a wave or as a flux of photons each of energy E h v. One can convert between wavelength, frequency and photon energy through algebraic or numerical relations. The bands of electromagnetic radiation extend from radio waves at the lowest frequencies to gamma rays at the highest. The average photon energy, or frequency, of radiation from an object is an indicator of the temperature of the emitting source if the radiation is thermal. Absorption of photons in the earth's atmosphere is frequency dependent so observations of some bands must be carried out from high altitude balloons or space vehicles. Similarly, absorption in the interstellar medium by dust and atoms renders the cosmos more or less...

Radiative Feedback from the First Sources of Light 71 Escape of Ionizing Radiation from Galaxies

The intergalactic ionizing radiation field, a key ingredient in the development of reionization, is determined by the amount of ionizing radiation escaping from the host galaxies of stars and quasars. The value of the escape fraction as a function of redshift and galaxy mass remains a major uncertainty in all current studies, and could affect the cumulative radiation intensity by orders of magnitude at any given redshift. Gas within halos is far denser than the typical density of the IGM, and in general each halo is itself embedded within an overdense region, so the transfer of the ionizing radiation must be followed in the densest regions in the Universe. Reionization simulations are limited in resolution and often treat the sources of ionizing radiation and their immediate surroundings as unresolved point sources within the large-scale intergalactic medium (see, e.g., Gnedin 2000a 152 ). The escape fraction is highly sensitive to the three-dimensional distribution of the UV sources...

Other electromagnetic waves

There are other electromagnetic waves which travel at the speed of light and turn out to have the same wave structure as light but which are produced in different ways and can have enormously different wavelengths, as indicated. Radio waves have the lowest energies and gamma rays the highest. Spectum of electromagnetic waves. We are all familiar with non-visible electromagnetic waves in certain contexts. Radio waves might be associated with radio and television, infrared waves with night vision binoculars, ultraviolet light with sunburn, microwaves with cooking, and X-rays and gamma rays with medical procedures. As we shall see in Chapter 10, electromagnetic waves are produced whenever an electric charge is accelerated. The universe is full of such radiation, ranging in wavelength right across the electromagnetic spectrum. It comes from natural sources and crosses billions of light years of interstellar space, carrying information about a variety of astrophysical phenomena.

What Is Electromagnetic Radiation

All forms of light are forms of electromagnetic radiation. Whether it is visible light the eye can detect, X-rays used by doctors to look at bones, radio waves that transmit music, or microwaves used to cook food, all are forms of electromagnetic radiation. Astrophysicists consider electromagnetic radiation to be both waves and photons, each distinct from the other. In all cases, the length of the wave is related to the energy contained in the photons the shorter the wavelength, the higher the energy of the photons. The only difference between the various types of electromagnetic radiation is their wavelengths and the amount of energy found in their photons. Radio waves, for example, which can occasionally be miles in length, have photons with very low energies, while gamma rays, which rarely exceed one-millionth of an inch, have very high energies. As a point of comparison, the vibration energy required to produce a single gamma ray is billions of times more rapid than the vibration...

How does matter emit electromagnetic energy

Matter consists of atoms and molecules containing protons and electrons, which respectively have positive and negative charge. There is always electrical activity even in an electrically neutral piece of matter, because of atomic oscillators whose motion becomes more rapid with increasing temperature. As predicted by Maxwell, and verified by Hertz in 1888, oscillating charges emit electromagnetic waves and in the process lose energy and slow down. That is one way in which a hot surface may cool down by radiating light into the space around it. Eventually, thermal equilibrium is established when the average energy emitted per second is balanced by the radiation absorbed.

Remarks on the Electromagnetic Radiation Field K0g

The characteristics of the field K0g. TETG assumes the existence of a narrow electromagnetic radiation band, of a specific intensity K0g (formula (3)), throughout the Solar System. The most probable characteristics of K0g are (a) the specific intensity as a thermodynamic measure k0K0 2.46 x 107m s-2 (b) the wavelengths X satisfy the relation 2.4 x 10-15m 0 14.8944 x 10-15m, where 0 is the diameter of the substance nuclei (c) the mean frequencies of the field vxmean 1023Hz (d) the energy transported by each quantum E 6.6256 10-11J (e) the frequency band of K0 being very narrow it satisfies the condition 10

Equations of Motion of Spin in Electromagnetic Field

In the next section the general problem of the spin precession in an external gravitational field will be reduced to the analogous problem for the case of an external electromagnetic field. The equations of motion for spin of a relativistic particle in electromagnetic field are not directly related to GR, and besides, they are well known.4 However, at least to make the presentation coherent, we will consider in this section just the problem referring to the electromagnetic The right-hand side of the equation for dSy dr should be linear and homogeneous both in the electromagnetic field strength Fyv, and in the same four-vector Sy, and may depend also on uy. In virtue of the first identity (7.20), the right-hand side should be four-dimensionally orthogonal to Sy. Therefore, the general structure of the equation we are looking for, is

Solar Electromagnetic Radiation

The Sun emits electromagnetic radiation at all wavelengths from 7-rays to radio waves. The shape of the spectral distribution is such that the bulk of the solar energy lies between 150 nm and 10 pm with the maximum near 450 nm, i.e., at the visible range of wavelengths. However, the ultraviolet portion ( 300 nm) of the spectrum is the most important in determinining the effects of solar radiation on the upper atmosphere and on technological systems in space. During solar storm conditions, also X-ray fluxes are significant. The variability of electromagnetic radiation in the visible wavelength range is very small over the solar cycle. Other parts of the spectrum can be much more variable both over the 27-day solar rotation period and over the 11-year solar

Electromagnetic Fields in the Magnetopause

In this section we present a few examples of Cluster's ability to measure electromagnetic field structure in the magnetopause. Two case studies demonstrate what is possible with burst mode data when the spacecraft are at small separation (100 km) Section 8.5.2 deals with a thin magnetopause without boundary layer, and Section 8.5.3 illustrates the detection of narrow current layers within a thick magnetopause. Section 8.5.4 discusses the properties of electromagnetic wave emissions observed near the magnetopause. 8.5.4 Electromagnetic waves

A52 Medical radiation exposure

Ionizing radiation for medical purposes, both in diagnosis and in treatment, is widely used. It must be noted that most of these procedures are carried out in countries where only one-quarter of the world population lives. World health care has been divided into four qualitative levels, depending on the number of physicians available.

Stars and Radiation 921 Electromagnetic Radiation

The spectrum of electromagnetic radiation ranges from gamma rays , X-rays, UV, visible light to IR, microwaves, and radiowaves. This is also a sequence of where c 300,000 km s, the speed of light. The energy of electromagnetic radiation (Fig. 9.12) depends on its frequency Fig. 9.12 Electromagnetic radiation. Only the visible part (400-700 nm), some part of the IR, and the radio part is observable from the ground. Wikimedia Cosmos

A22 The Wavelength Range of the Electromagnetic Spectrum

Radio waves are at the long-wavelength end of the electromagnetic spectrum, as long as hundreds of meters down to a millimeter and well-known microwaves have wavelengths of around a few centimeters. As wavelength decreases we find infrared (1R) radiation, commonly experienced as heat, then light waves which range from 70 millionths of a centimeter (7 x 10-5 cm) for the long wavelength red light down to 40 millionths of a centimeter (4 x 10 5 cm) tor violet light. The colors of the rainbow fall between these two extremes. Beyond that going to shorter wavelengths comes ultraviolet (UV) radiation, sometimes called blacklight. (UV causes sunburn, and in large doses is extremely harmful to living organisms.) Next are Xays, with wavelengths so short that they literally wriggle between atoms and so can penetrate our bodies. Finally, at the shortest (less than 1 x IO8 cm) wavelength end of the spectrum are the gamma rays.

The Conqest of the Electromagnetic Spectrum

Newton, in the middle of the 17th century, found out that light is composed of a whole range of colors and that this spectrum spans from violet to blue, green, yellow, orange and red. It implies a wavelength range from about 400 to about 750 nanometers. Not much was known about the nature of light until 1690 when C. Huygens showed that light has a wave character. Over 100 years later this scale rapidly expanded at both ends. F.W. Herschel found in 1800 that the largest amount of heat from the Sun lies beyond the red color in the spectrum. One year later J. W. Ritter detected radiative activity beyond the violet color of the spectrum. Both events mark the discovery of infrared and ultraviolet light. J. Maxwell postulated in 1865 that light is composed of electromagnetic waves, a theory that was proved to be correct by H. Hertz in 1887, who also detected electromagnetic waves with very long wavelengths and thus added the radio band to the electromagnetic spectrum. In another milestone...

The Electromagnetic Spectrum

Pair Production Interaction Radiation

The quantum description of electromagnetic radiation emphasises its wave-particle duality. Thus energy is transferred in packets or quanta called photons and the energy of a photon of frequency v (Ev) is given by Photons of electromagnetic radiation can interact with matter in a variety of ways, depending on their energy, as indicated schematically in Figure 13.1 (see also Chapter 8). At lower photon energies, the photoelectric effect (a) involves the removal of a bound electron by the incoming photon (ionisation) where the Table 13.1 Regions of the electromagnetic spectrum. Table 13.1 Regions of the electromagnetic spectrum. Figure 13.2 The transmission of the Earth's atmosphere for photons of the electromagnetic spectrum as a function of wavelength. Figure 13.2 The transmission of the Earth's atmosphere for photons of the electromagnetic spectrum as a function of wavelength. While X-rays with Ev 50 keV can penetrate to 30 km above the Earth's surface, where they can be studied by...

The energy tensor of the electromagnetic field

In this final section we give a brief account of Minkowski's energy tensor, and show how the electromagnetic field itself possesses energy, momentum, and stress just like a material continuum. In this way the well-validated conservation laws of mechanics can be extended to interactions between charged matter and electromagnetic fields. For example, if we simultaneously release two oppositely charged particles from rest and they accelerate towards each other, where does the kinetic energy come from Or, relative to another inertial frame where one of these charges begins to move before the other, where does the momentum come from One can use 'potential' energy and even potential momentum as bookkeeping devices, but there are good reasons (both formal and physical) for considering the field itself able to exchange energy and momentum with matter. According to Einstein's general relativity, energy (that is, mass), momentum, and stress all curve spacetime (measurably, in principle) at...

Electromagnetic Field Except For Its Complexion

(b) In the generic (non-null) case in the frame in question, show that T is the Maxwell tensor of the extremal electromagnetic field f with components (d) Show that the most general electromagnetic field which will reproduce the non-null tensor T11 in the frame in question, and therefore in any coordinate system, is (e) Derive a corresponding result for the null case. The field F defined in the one frame and therefore in every coordinate system by (d) and (e) is known as the Maxwell square root of J * is known as the extremal Maxwell square root of 7 and the angle a is called the complexion of the electromagnetic field. See Misner and Wheeler (1957) see also Boxes 20.1 and 20.2, adapted from that paper.

How This Book Is Organized

Part 2, Now You See It (Now You Don't), explains how telescopes work, offers advice on choosing a telescope of your own, and provides pointers to help you get the most from your telescope. You'll also find an explanation of the electromagnetic spectrum (of which visible light is only one part) and how astronomers use radio telescopes and other instruments to see the invisible portions of that spectrum. Finally, we'll take you into the cosmos aboard a host of manned and unmanned probes, satellites, and space-borne observatories.

The Telescope Is Born

The electromagnetic spectrum is the complete range of electromagnetic radiation, from radio waves to gamma waves and everything in between, including visible light. The electromagnetic spectrum is the complete range of electromagnetic radiation, from radio waves to gamma waves and everything in between, including visible light.

Observatory in Space the Hubble Space Telescope

There are other ways to escape the seeing caused by the earth's atmosphere You can get above and away from the atmosphere. In fact, for observing in some portions of the electromagnetic spectrum, it is absolutely required to get above the earth's atmosphere. That is just what NASA, in conjunction with the European Space Agency, did with the Hubble Space Telescope. High above the earth's atmosphere, the HST regularly achieves its theoretical resolution. V Light is a form of electromagnetic radiation. Radiation carries energy and conveys information. V Objects in space produce or reflect the various forms of electromagnetic radiation (including radio, infrared, visible light, ultraviolet, x-rays, and gamma rays) this radiation is what we see with our eyes or detect with special instruments.

Big News from Little Places

Atoms can be further broken down into electrons, protons, and neutrons, and the latter two are made of even smaller things called quarks. Electrons carry a negative electric charge, and protons a positive charge. Neutrons have a mass almost equal to a proton, but as their name implies, neutrons are neutral, with no positive or negative charge. charged particles (like protons and electrons) that are not moving are surrounded by what we call an electric field those in motion produce electromagnetic radiation. Let's turn to a specific example A star is made up of innumerable atoms, most of which at unimaginably hot stellar temperatures are broken into innumerable charged particles. A star produces a great deal of energy (by nuclear fusion, which we'll discuss in Chapter 16, Our Star ). This energy causes particles to be in constant motion. In motion, the charged particles are the center points of electromagnetic waves (disturbances in the electromagnetic field) that...

The Black Body Spectrum

As Maxwell first described in the nineteenth century, all objects emit radiation at all times because the charged atomic particles of which they are made are constantly in random motion. As these particles move, they generate electromagnetic waves. Heat an object, and its atomic particles will move more rapidly, thereby emitting more radiation. Cool an object, and the particles will slow down, emitting proportionately less electromagnetic radiation. If we can study the spectrum (that is, the intensity of light from a variety of wavelengths) of the electromagnetic radiation emitted by an object, we can understand a lot about the source. One of the most important quantities we can determine is its temperature. Fortunately, we don't need to stick a thermometer in a star to see how hot it is. All we have to do is look at its light carefully. Now, no object in the physical world absorbs and radiates in this ideal fashion, but the black-body curve can be used as a reference index against...

Dark Doesnt Mean You Cant

On a clear night far from urban light pollution, the sky is indeed dazzling. Just remember that the electromagnetic information your eyes are taking in, wondrous as it is, comes from a very thin slice of the entire spectrum. As we mentioned in the last chapter, the earth's atmosphere screens out much of the electromagnetic radiation that comes from space. It allows only visible light and a bit of infrared and ultraviolet radiation to pass through a so-called optical window and a broad portion of the radio spectrum to pass through a radio window.

The Rest of the Spectrum

Optical astronomy with the naked eye is at least 5,000 years old and probably much older. Optical telescope astronomy is about 400 years old. Radio astronomy is a youthful discipline at about 70 years, if we date its birth from Jansky's work in the early 1930s. But it has been only since the 1970s that other parts of the electromagnetic spectrum have been regularly explored for the astronomical information they may yield. As might have been expected, each new window thrown open on the cosmos has brought in a fresh breeze and enriched our understanding of the universe.

Chandrasekhar and the XRay Revolution

Electromagnetic radiation at the highest end of the spectrum can now be studied. Since x-rays and gamma rays cannot penetrate our atmosphere, all of this work must be done by satellite. Work began in earnest in 1978 when an x-ray telescope was launched, called the High-Energy Astronomy Observatory (later, the Einstein Observatory). The Roentgen Satellite (ROSAT) was next launched by Germany in 1990. The Chandra X-ray Observatory (named for astronomer Subrahmanyah Chandrasekhar) was launched into orbit in July 1999 and has produced unparalleled high-resolution images of the x-ray universe. The Chandra image of the Crab Nebula, home to a known pulsar, showed never before seen details of the environment of an exploded star. For recent images, go to www.chandra.harvard.edu. X-rays are detected from very high energy sources, such as the remnants of exploded stars (supernova remnants) and jets of material streaming from the centers of galaxies. We'll tell you more about some of these...

Capturing the Full Spectrum

Once satellites are launched, any astronomer can make a proposal to obtain observing time. There are always many more proposals than time available, but this practice makes some of the world's most advanced technologies available to astronomers at institutions worldwide. Today's astronomers have the unique ability to turn to almost any region of the electromagnetic spectrum for answers to their questions. They can play with a full keyboard, instead of plunking away on a single key. V In recent years, astronomers have launched instruments into orbit that can detect all segments of the electromagnetic spectrum, from infrared, through visible, and on to ultraviolet, x-rays, and gamma rays. The highest frequency radiation (x-rays and gamma rays) comes from some of the most energetic and exotic objects in the universe.

Pearls the Size of Worlds

There were critics of the nebular theory in the nineteenth century, among them James Clerk Maxwell, who had figured out the fundamentals of electromagnetic radiation. What Maxwell and the other critics of the Kant-Laplace theory didn't know about was interstellar dust. Microscopic dust grains ice crystals and rocky matter formed in the cooling atmosphere of dying stars, then grew by attracting additional atoms and molecules of various gases. These dust grains served two purposes in the formation of planets

Postcards from the Edge

Next, suppose we equipped the probe with a transmitter broadcasting electromagnetic radiation of a known frequency. As the probe neared the event horizon, we would begin to detect longer and longer wavelengths. This shifting in wavelength is known as a gravitational redshift. This shift occurs because the photons emitted by our transmitter lose some energy in their escape from the strong gravitational field near the event horizon. The reduced energy would result in a frequency reduction (and, therefore, a wavelength increase) of the broadcast signals that is, a redshift. As the wavelength of the broadcast is stretched to infinite lengths, so the time between passing wavecrests becomes infinitely long. Realize, however, that if you could somehow survive aboard the space probe and were observing from inside rather than from a distance, you would perceive no changes in the wavelength of electromagnetic radiation or in the passage of time. Relative to you, nothing strange would be...


But professional astronomers don't limit their observations to the visible spectrum. Modern astronomy can tune into radio, infrared, ultraviolet, and even high-energy gamma radiation. Chapter 7 orients you within the electromagnetic spectrum, and Chapter 8 explores the range of the modern invisible astronomies.

The Whole Spectrum

Electromagnetic radiation travels though the vacuum of space in waves, which we shall also examine in some detail in Chapter 7. A wave think of a water wave is not a physical object, but a pattern of up-and-down or back-and-forth motion created by a disturbance. Waves are familiar to anyone who has thrown a rock in a pond of still water or watched raindrops striking a puddle. The wave pattern in the water, a series of concentric circles, radiates from the source of the energy, the impact of the rock or the rain drop. If anything happens to be floating on the surface of the water say a leaf the waves will transfer some of the energy of the splash to the leaf and cause it to oscillate up and down. The important thing to remember about waves is that they convey both energy and information. Even if we didn't actually see the rock or the raindrop hit the water, we would be able to surmise from the action of the waves that something had disturbed the surface of the water at a particular...

Dont Look Too Hard

V Understanding electromagnetic radiation V A tour of the electromagnetic spectrum V Using the electromagnetic spectrum to get information from the sky We have concentrated thus far on optical photons (the ones that we can see with our eyes). As it turns out, our eyes respond to visible wavelengths because that is where the peak of the emission from the sun is located in the electromagnetic spectrum. If our eyes were most sensitive to infrared radiation, for example, we would see some things we can't now see (body heat), but would miss a lot of other useful stuff. In this chapter, we're going to talk more about visible light and the electromagnetic spectrum, of which visible light is a tiny subset. Think of it this way If the electromagnetic spectrum is represented by a piano keyboard, then the visible part of the spectrum is but a single key or note. In the cosmic symphony, there are many notes, and we want to be able to hear them all. If you're concerned that this sounds more like...

Making Waves

Electromagnetic radiation sounds like dangerous stuff and, in fact, some of it is. But that the word radiation need not set off sirens in your head. It just describes any way energy is transmitted from one place to another without the need for a physical connection between the two places. We use it as a general term to describe any form of light. It is important that radiation can travel without any physical connection, because space is essentially a vacuum that is, much of it is empty. If you went on a space walk clicking a pair of castanets, no one, including you, would hear your little concert. Sound is transmitted in waves, but not as radiation. Sound waves require some medium to travel in. So despite what most science fiction movies would lead you to believe, explosions in space are silent. Light (and other forms of electromagnetic radiation) requires no such medium to travel, although many physicists tried in vain to detect a medium, which they called the ether. We'll talk more...

Full Spectrum

Often, when people get excited, they run around, jump up and down, and shout without making a whole lot of sense. But when atomic particles get excited, they can produce energy that is radiated at a variety of wavelengths. In contrast to the babble of an excited human throng, this electromagnetic radiation can tell you a lot, if you have the instruments to interpret it. How fast do electromagnetic waves move All of them whether visible light, invisible radio waves, x-rays, or gamma radiation move (in a vacuum) at the speed of light, approximately 186,000 miles per second (299,792,458 meters per second). Fast, but hardly an infinite, unlimited speed. Remember the Andromeda galaxy from Chapter 5 We can see it, but the photons of light we just received from the galaxy are 2 million years old. Now, that's a long commute. How fast do electromagnetic waves move All of them whether visible light, invisible radio waves, x-rays, or gamma radiation move (in a vacuum) at the speed of light,...

What Makes Color

Within such a tiny range of wavelengths all colors are contained. Just as wavelength (or frequency) determines whether electromagnetic radiation is visible light or x-rays or something else, so it determines what color we see within this tiny range. Our eyes respond differently to electromagnetic waves of different wavelengths. Red light, at the low-frequency end of the visible spectrum, has a wavelength of about 7.0 x 10-7 meters (and a frequency of 4.3 x 1014 Hz). Violet light, at the high-frequency end of As we said earlier in this chapter and in Chapter 5, we see celestial objects because they are producing energy, and that energy is transmitted to us in the form of electromagnetic radiation. As we will see in later chapters, different physical processes produce different wavelengths (energies) of light. Thus the portion of the spectrum from which we receive light itself is an important piece of information.

Seeing in the Dark

But, Daddy, the visible spectrum is squeezed between 400 and 700 nm. What about the rest of the electromagnetic spectrum Until well into the twentieth century, astronomers had no way to see most of the nonvisible electromagnetic radiation that reached Earth from the universe. Then along came radio astronomy, which got its accidental start in 1931-1932 and was Radio astronomy is simply the study of the universe at radio wavelengths. Astronomers used to categorize themselves by the wavelength of the observations that they made radio astronomer versus optical astronomer. Increasingly, though, astronomers define their work more by what they study (pulsars, star formation, galactic evolution) than by what wavelength they use. The reason for this change is that, in recent years, new instruments have opened the electromagnetic spectrum to an unprecedented degree. Astronomers now have the ability to ask questions that can be answered with observations at many different wavelengths.

Solar Wind

The sun does not keep its energy to itself. Its energy flows away in the form of electromagnetic radiation and particles. The particles (mostly electrons and protons) do not move nearly as fast as the radiation, which escapes the sun at the speed of light, but they move fast nevertheless at more than 300 miles per second (500 km s). It is this swiftly moving particle stream that is called the solar wind.

Stellar Lighthouse

Charged particles are accelerated by the star's magnetic field. These regions, which rotate with the star, radiate intense energy. As the neutron star rotates, a beam of electromagnetic radiation (especially intense in the radio regime) sweeps a path through space. If the earth lies in that path, we see the pulsar.

Wheres the Surface

Remember that the collapse of a black hole is in some sense infinite. Our three-or-more solar-mass stellar core will not stop shrinking just because it has reached the Schwarzschild radius. It keeps collapsing. Once it is smaller than the Schwarzschild radius, however, it will effectively disappear. Its electromagnetic radiation (and the information that it carries) is thereafter unable to escape. We spoke earlier about electromagnetic radiation carrying energy and information. Since we cannot get radiation from within the Schwarzschild radius, we cannot get any information from there, either. Events that occur within that radius are hidden from our view. For this reason, the Schwarzschild radius is also called the event horizon. We cannot see past this ultimate horizon.

Anatomy of a Wave

We can understand how electromagnetic radiation is transmitted through space if we appreciate that it involves waves. What is a wave The first image that probably jumps to mind is that of ocean waves. And ocean waves do have some aspects in common with the kind of waves that we use to describe electromagnetic radiation. One way to think of a wave is that it is a way for energy to be transmitted from one place to another without any physical matter being moved from place to place. Or you may think of a wave as a disturbance that carries energy and that occurs in a distinctive and repeating pattern. A row boat out in the ocean will move up and down That regular up-and-down motion that the rowboat experiences is called harmonic motion. But there are two important differences with electromagnetic radiation The sources of waves are things on atomic scales (electrons and the nuclei of atoms), and no medium is required for electromagnetic waves to travel through space. The pond of space...

Blocking Light

Why is it that dust blocks our optical view of the Milky Way It's due to the size of the dust grains. Let's think about this for a moment. A satellite dish can be made out of a wire mesh, perforated by small holes. Why doesn't this structure let the radio waves slip through, like water through a sieve Because it's catching radio waves, and radio waves are big. So big, in fact, that as long as the holes are small enough, the radio waves don't even know the holes are there. The waves reflect off the surface of the dish as if it were solid. In fact, all electromagnetic radiation (light included) works this way. The waves interact only with things that are about the same size as their wavelength. As luck would have it, optical wavelengths are about the same size as the diameter of a typical dust grain. As a result, optical photons are absorbed or scattered by dust, while long-wavelength radio waves pass right through.

Types of Supernovae

No supernova has appeared in our Galaxy, the Milky Way, since 1604. Since supernovae are among the most energetic processes known, it is not surprising that the light of a supernova can outshine the combined light of the entire Galaxy. Theory predicts a supernova occurrence in our Galaxy every 100 years or so. We are, therefore, more than a bit overdue, and we may be in for a spectacular display any day now. The cosmic rays and electromagnetic radiation that would rain down on the earth if a nearby supernova were to go off (say within 30-50 light-years) would have catastrophic results. Fortunately, there aren't any stars that close to us massive enough to generate a Type II supernova.

Star Words Glossary

Cosmological redshift The lengthening of the wavelengths of electromagnetic radiation caused by the expansion of the universe. electromagnetic radiation Energy in the form of rapidly fluctuating electric and magnetic fields and including visible light in addition to radio, infrared, ultraviolet, x-ray, and gamma-ray radiation. EM radiation often arises from moving charges in atoms and molecules, though high-energy radiation can arise in other processes. electromagnetic spectrum The complete range of electromagnetic radiation, from radio waves to gamma waves and everything in between. radio telescope An instrument, usually a very large dish-type antenna connected to a receiver and recording and or imaging equipment, used to observe radio-wavelength electromagnetic radiation emitted by stars and other celestial objects. redshift An increase in the detected wavelength of electromagnetic radiation emitted by a celestial object as the recessional velocity between it and the observer...

Relativistic Quantum Theory of Atoms and Molecules

The Springer Series on Atomic, Optical, and Plasma Physics covers in a comprehensive manner theory and experiment in the entire field of atoms and molecules and their interaction with electromagnetic radiation. Books in the series provide a rich source of new ideas and techniques with wide applications in fields such as chemistry, materials science, astrophysics, surface science, plasma technology, advanced optics, aeronomy, and engineering. Laser physics is a particular connecting theme that has provided much of the continuing impetus for new developments in the field. The purpose of the series is to cover the gap between standard undergraduate textbooks and the research literature with emphasis on the fundamental ideas, methods, techniques, and results in the field.

Summary Of Observations

Spacecraft have measured particle velocity distribution functions and electromagnetic fields as close to the Sun as 60 R (Helios 1 and 2), and as far as 12,000 J 0 (Voyager 2). Departures from Maxwellian velocity distributions have been used as sensitive constraints on the kinetic physics on microscopic scales (see, e.g., Feldman & Marsch 1997). In situ instruments have also measured fluctuations in magnetic field strength, velocity, and density on time scales ranging from 0.1 second to months and years. Both propagating waves (mainly Alfvenic in nature) and nonpropagating, pressure-balanced structures advecting with the wind are observed. Nonlinear interactions between different oscillation modes create strong turbulent mixing, and Fourier spectra of the fluctuations show clear power-law behavior indicative of inertial and dissipation ranges in agreement with many predictions for fully developed MHD turbulence (Goldstein et al. 1995, Tu & Marsch 1995).

I25 Science opportunities

A lunar base will be a superb platform for scientific activities of, on, and from the Moon. For example, the Moon is a much more stable platform for the operation of space telescopes than Earth orbit or free space, and the lunar regolith can be used to shield instruments from ionizing radiation, micrometeorites, and temperature extremes. Interferometry, the high-precision telescopic technique that yields images of very high resolution in optical and longer wavelengths, can be fully exploited on the Moon. The far side of the Moon is also free from all radio interference from the Earth, and is therefore the ideal site in the solar system for the operation of radio telescopes, including the search for extraterrestrial intelligence (SETI). The Moon will eventually become a coordinated astronomical observatory that will greatly expand humankind's knowledge of the universe. The Moon is also a treasure trove of information on the geologic history of the solar system, and a global program of

Introduction nuclei and their behaviour

Many isotopes exist indefinitely, at least in normal conditions, and these are known as stable isotopes, S. The nuclei of the great majority of isotopes are, however, not stable and can spontaneously decay, i.e. turn into other nuclei, by emitting or absorbing a particle as summarized in Fig. 1.1. These decaying isotopes are termed radioactive or parent isotopes, rR, and the decay products are radiogenic or daughter isotopes, rD. Generally after decay an excited daughter nucleus cools down , emitting y-rays (high-frequency electromagnetic radiation). Each radioactive isotope species has its own specific rate of decay, X, known as the

Whats New In The Seventh Edition

Web sites with daily astro-news and space scenes never before viewed by humans are specified. Labeled drawings of the Keck Telescope, Fermi Gamma Ray Observatory, and Hubble Space Telescope data path clarify space technology. New art illustrates fundamental concepts, such as the electromagnetic spectrum, phases of the Moon, planet orbits, and H-R diagrams.

Preface to the second edition

We had toyed with the idea of a second edition for some time. It was clear that tinkering at the edges of the first edition would not do so much had changed since the publication of what we began to refer to as 'CNI'. There were of course the inevitable advances in the quality and nature of the observations' over the entire electromagnetic spectrum, and in our theoretical understanding of the classical nova phenomenon as computing power grew. However, there was also the advent of the NASA Astrophysics Data System (ADS), and the facility to prepare a finding chart at the click of a mouse button (R. A. Downes & M. M. Shara 1989, PASP105, 127) who could have foreseen this when CNI was being compiled The latter two rendered the Data on Novae chapter of the first edition completely obsolete. There was no alternative but to start what inevitably became known as 'CNII' effectively with a clean sheet.

Determination of binary parameters

The parameters of binary systems are generally obtained from astrometric, or spectro-scopic, or photometric observations, and in favourable cases by a combination of two, or even all three, of these methods. Note that terms such as 'astrometric' and 'photometric', coined originally to refer to observations in the visible portion of the electromagnetic spectrum, are now generally used to cover all parts of the spectrum, for instance radio and X-rays. If the two components of a binary are so far apart in the sky as to be resolvable from each other, which means at visual wavelengths more than 0.1 (0.5 iirad) apart, then the system is a 'visual binary' or 'VB', and careful astrometry, sometimes over a century or more, can reveal the orbit. Visual binaries tend to have long periods because short-period orbits are generally not resolvable. Only for systems within 5 pc of the Sun (about 50 in number) could a separation of 0.2 correspond to a period of year. The upper limit of well-determined

Requires No External Sensorsorbit Independent High Accuracy For Limited Time Intervals Easily Done Onboard

That affect the attitude, as listed in Table 1-2, are aerodynamic torque caused by the rapid spacecraft motion through the tenuous upper atmosphere gravity-gradient torque due to the small difference in gravitational attraction from one end of the spacecraft to the other (the same differential force which produces tides) magnetic torque due to the interaction between the spacecraft magnetic field (including induced magnetism from the surrounding field) and the Earth's magnetic field and solar radiation torque due to both the electromagnetic radiation and particles radiating outward from the Sun. Early investigators felt that micrometeorites might also supply a significant source of torque. However, this has been found negligible relative to the other torques, except perhaps in some unexplored regions of the solar system, such as inside the rings of Saturn.

Why look at the heavens from space

Most of our information on celestial objects comes through the electromagnetic radiation that planets, stars and galaxies emit throughout the spectrum.They obviously do not care that on our planet only a small (frequency) window, the one to which our eyes became adapted, penetrates the atmosphere. Placing telescopes in orbit has provided astronomers with an immense leap in their powers of observation.The recent Nobel Prize to Riccardo Giacconi for the development of X-ray astronomy is but one example of the recognition of such a widening of horizons. There is more to space astronomy besides the electromagnetic spectrum and in situ exploration.We also receive information from the Universe through essentially untapped channels, such as gravitational waves - another of Einstein's predictions -that have so far only been indirectly observed.Through them, we expect to improve our understanding of a variety of phenomena, such as merging neutron stars, forming gigantic black holes in the...

Introduction solar features and terminology

The Sun serves as the source of inspiration and the touchstone in the study of stellar magnetic activity. The terminology developed in observational solar physics is also used in stellar studies of magnetic activity. Consequently, this first chapter provides a brief illustrated glossary of nonmagnetic and magnetic features, as they are visible on the Sun in various parts of the electromagnetic spectrum. For more illustrations and detailed descriptions, we refer to Bruzek and Durrant (1977), Foukal (1990), Golub and Pasachoff (1997), and Zirin (1988).

What is Radio Astronomy

Eighty years later historians of science would report that Hertz was at least the sixth physicist to see this odd effect, but he was the first to follow up on his key question. He proceeded to design a series of brilliantly simple experiments, one after another, in search of an answer. He was able to show that an invisible form of radiation, which he called electric waves, carried energy through intervening space. Hertz was also able to demonstrate that the electric waves were a phenomenon very similar to light. In fact their speed through the air was the same as that of light. Today we know that both light and Hertz's electric waves are forms of electromagnetic radiation (see Appendix A.2). Over time, the Hertzian waves (a name used very early in the 20th century) came to be called radio waves. Their frequency is measured in cycles per second, now called Hertz (Hz), In Appendix 2.1 the relationship between frequency and wavelength is discussed. For the bulk of our story we will refer...

Historical Background

It is a common perception that astronomy is one of the oldest occupations in the history of mankind. While this is probably true, ancient views contain very little about the origins of stars. Their everlasting presence in the night sky made stars widely used benchmarks for navigation. Though it always was and still is a spectacular event once a new light, a nova, a new star appears in the sky. Such new lights are either illuminated moving bodies within our Solar System, or a supernova and thus the death of a star, or some other phases in the late evolution of stars. Never is a normal star really born in these cases. The birth of a star always happens in the darkness of cosmic dust and is therefore not visible to human eyes (see Plate 1.1). In fact, when a newborn star finally becomes visible, it is already at the stage of kindergarten in terms of human growth. It takes the most modern of observational techniques and the entire accessible bandwidth of the electromagnetic spectrum to...

Lorentz transformations

Maxwell's equations describe the propagation of light in the form of electromagnetic waves. These equations are linear. The Michelson-Morley experiment 372 shows that the velocity of light is constant, independent of the state of the observer. Lorentz derived the commensurate linear transformation on the coordinates, which leaves Maxwell equations form-invariant. It will be appreciated that form invariance of Maxwell's equations implies invariance of the velocity of electromagnetic waves. This transformation was subsequently rederived by Einstein, based on the stipulation that the velocity of light is the same for any observer. It is non-Newtonian, in that it simultaneously transforms all four spacetime coordinates.

Snells Law and Glass Dispersion

The light is the visible part of the electromagnetic spectrum which covers wavelengths from gamma rays to radio waves that all propagate at velocity c in a vacuum. The propagation of the electric and magnetic vectors E and H is represented by Maxwell's equations of electromagnetism (cf. Born and Wolf 17 ). In an homogeneous medium (as all media considered hereafter), these equations reduce to the wave equations

Disk Irradiation by Energetic Particles and Extinct Radioactivities in Meteorites

For the young Solar System, the X-rays may play another role. First, we know from solar observations that flares seen in X-rays also accelerate particles, i.e., electrons, protons and heavier nuclei, which induce so-called spallation nuclear reactions, that is, in-flight, low-energy collisions breaking the nuclei. Among the resulting fragments, some nuclei are produced in an excited state, others are radioactive they are subsequently de-excited or decay, emitting 7-ray photons, such as those that were observed from the Earth in the solar photosphere by the SMM satellite (Murphy et al. 1991), and more recently by the RHESSI satellite (Lin et al. 2003). Again relying on the analogies between the magnetic activity of young stars and that of the Sun, one can then safely assume that particles must be accelerated in the flares of the young stars. This is in part confirmed by radio observations in the centimetre range, which show evidence for a non-thermal emission mechanism (...

Classical Yang Mills Black Hole Hair in Antide Sitter Space

The black hole no-hair conjecture 142 states that (see, for example, 51, 52, 77-79, 118 for detailed reviews and comprehensive lists of references) All stationary, asymptotically flat, four-dimensional black hole equilibrium solutions of the Einstein equations in vacuum or with an electromagnetic field are characterized by their mass, angular momentum, and (electric or magnetic) charge.

Basic solar properties

The solar distance is called the astronomical unit (AU) it is used as a basic unit in the Solar System and beyond. So is the solar mass, which is negligibly altered by the solar wind ejection. Indeed, the solar wind pours out in space roughly 109 kgs-1, which amounts to only 1O 4M0 over the Sun's age of a few 109 years. Note that the wind is not the only source of solar mass loss the mass-energy equivalence tells us that the luminosity L0 - the energy lost by the Sun per second via electromagnetic waves - yields a mass loss of L0 c2 4.3 x 109 kgs-1 this amounts to about four times the mass carried away by the solar wind, and thus barely alters the Sun's mass either we will return later to the solar energy source. At the mean distance of the Earth (but outside its atmosphere), the flux received from the Sun in the form of electromagnetic radiation by a surface perpendicular to the rays of sunlight is

The Interstellar Medium

Radio telescopes have detected the presence of water molecules in the large clouds of gas between the stars. Water masers are clouds of water molecules that have absorbed some energy from collisions or infrared radiation and that have not yet lost this energy as a result of energy transitions. The water masers subsequently amplify background electromagnetic radiation in exactly the way that lasers in Earth-based laboratories do. Such water masers have been detected in the environments of young and old stars, a fact that implies the presence of large amounts of water in the environments around many stars. This water ice may play an important role in the advent of life in newly formed planetary systems. And some of this water eventually may be locked up in the far reaches of other systems (their Kuiper Belts and Oort Clouds), providing billions of years of comet infall. The nascent field

I4Observations versus theory

Neutron stars are observed in all bands of electromagnetic spectrum in our Galaxy and in nearby satellite galaxies (such as the Large Magellanic Cloud and Small Magellanic Cloud). The neutron star astronomy is extending into the Local group of galaxies and even further. For instance, X-ray bursters ( 1.4.6) have been observed in the galaxy M31 (Pietsch & Haberl, 2005), and an ecpipcing X-ray binary has been discovered in the galaxy M101 outside the Local group (Liu et al., 2006). We outline main observational manifestations of neutron stars and mention also some theoretical work on interpretation of these manifestations. The same star can manifest itself in different ways. Our description will inevitably be schematic and bibliography incomplete. We summarize numerous observational manifestations of neutron stars in Table 1.1. We hope that the table will simplify reading of this section. The table heading is just the title of the conference which took place from September 30 till...

So What Is Radio Astronomy

Nonthermal emission, sometimes called synchrotron radiation, involves cosmic ray electrons that spiral around magnetic fields and radiate energy in the form of radio waves. Depending on the energy of the particle and the strength of the magnetic field involved, this process can produce emission at any of the wavelengths across the electromagnetic spectrum (see Appendix A.2).

Electrodynamics and Gravitation

The equation of motion for a particle of a mass m and a charge e in an electromagnetic field F v is well known The equations of the electromagnetic field are Equations (2.1) and (2.2), taken together with initial conditions for charges and fields on a space-like surface, determine completely the evolution of a system. The equations of electrodynamics are linear, for electromagnetic fields the superposition principle is valid. The point is that it is the charges that serve as a source of the electromagnetic field. But the electromagnetic field by itself is neutral, it bears no charge. As to the gravitational field, its source is energy, however, the gravitational field possesses energy by itself. Therefore, the gravitational field equations are in fact nonlinear. The linear equations (2.6) and (2.7) are valid, as has been pointed out already, for weak fields only.

Some basic wave concepts

The waves on the pond can be used to illustrate several other wave concepts. The stone hitting the water surface excites a group of waves, within which the surface profile is approximately sinusoidal. The line following a particular maximum of the wave (a growing circle in this case) is called a wavefront. The wavefront has a velocity called the wave or phase velocity this can be deduced by comparing figure 2.4(a) and (b) and measuring the distance that the wavefront has traveled in the time between the photographs. It also has a group velocity which is the distance traveled in unit time by the envelope of the group of waves excited by the stone. The group and wave velocities may not be equal in the case of water surface waves they are not, but for electromagnetic waves in free space the two velocities are equal.

A case of failure of Tebased abundances metalrich giant H II regions

In many cases, the weak O Ill A4363 or NII A5755 lines are not available because either the temperature is too low or the spectra are of low signal-to-noise ratio, or else the data consist of narrow-band images in the strongest lines only. Then, one may use the so-called strong-line methods to derive abundances. Such methods are only statistical, in the sense that they allow one to derive the metallicity of an H II region only on the assumption that this H II region shares the same properties as those of the H II regions used to calibrate the method. In practice, such methods work rather well for giant H II regions, since it appears that giant HII regions form a narrow sequence (see e.g. McCall et al. 1985), in which the hardness of the ionizing radiation field and the ionization parameter are closely linked to the metallicity. Indeed, an increased metallicity enhances the metal line blocking of the emergent stellar flux in the extreme ultraviolet and softens the ionizing spectrum. In...

What we learn in this chapter

Celestial measurements reaching back 3000 years or more were carried out in many cultures worldwide. Early astronomers in Greece deduced important conclusions about the nature of the earth and the solar system. Modern astronomy began in the renaissance with the observations of Tycho Brahe and Galileo and the theoretical work of Kepler and Newton. The progress of our knowledge of the sky may be traced through a series of major discoveries which often follow the development of new technologies such as the telescope, computers, and space observatories. Astronomy is now carried out across the entire electromagnetic spectrum from the radio to the gamma ray (see cover illustrations) as well as with cosmic rays, neutrinos, and gravitational waves. The mutual dependence of theory and observation has led to major advances in the understanding of a wide diversity of celestial objects such as stars, supernova remnants, galaxies, and the universe itself. Current observations reveal important...

Astronomy From The Moon

From the time of Galileo until the beginning of the twentieth century, the primary means by which astronomers derived knowledge of the universe was by making telescopic observations of the visible light that was emitted or reflected by objects in space. Significant advances in astronomy were made from these telescopic observations however, the data that were gathered were incomplete because visible light represents only a small fraction of the electromagnetic spectrum from which the universe may be observed. In the twentieth century, technical advances have allowed astronomers to expand their investigations to include the entire range of the electromagnetic spectrum, thus greatly expanding our knowledge of the universe. The divisions and characteristics of the electromagnetic spectrum from which astronomical observations may be made are listed in Table 2.1. Table 2.1 Properties of the electromagnetic spectrum Table 2.1 Properties of the electromagnetic spectrum

Robot Spacecraft in Service to Astronomy

Each portion of the electromagnetic spectrum (that is, radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays) brings astronomers and astrophysicists unique information about the universe and the objects within it. For example, certain radio frequency (RF) signals help scientists characterize cold molecular clouds. The cosmic microwave background (CMB) represents the fossil radiation from the big bang, the enormous ancient explosion considered by most scientists to have started the present universe about 15 billion years ago. The infrared (IR) portion of the spectrum provides signals that let astronomers observe non-visible objects such as near-stars (brown dwarfs) and relatively cool stars. Infrared radiation also helps scientists peek inside dust-shrouded stellar nurseries (where new stars are forming) and unveil optically opaque regions at the core of the Milky Way Galaxy. Ultraviolet (UV) radiation provides astrophysicists special information...

Astronomy from Earth orbit

Observation of every major segment of the electromagnetic spectrum have been placed in Earth orbit, creating whole new bodies of knowledge about the universe. For example, orbiting observatories such as the IRAS and Compton Gamma Ray telescopes have made extensive observations of the sky in the infrared and gamma-ray segments of the electromagnetic spectrum, respectively, that would not have been possible by means of Earth-based observatories. The Hubble Space Telescope operates primarily in the visible-light region of the electromagnetic spectrum it has greater resolving power4 than, and its images far exceed the quality of, Earth-based telescopes.

The Spectrum of Starlight

By the way, the spectrum of electromagnetic radiation, which includes visible light, continues beyond violet with wavelengths shorter than those of visible light ultraviolet, X-rays, and gamma rays and beyond red with wavelengths longer than those of visible light infrared, microwaves, and radio waves. Some astronomical bodies produce radiation in many of these wavelengths. In the past few decades, those wavelengths have become increasingly observable by improved detectors and by satellites being able to make the observations above Earth's atmosphere, which blocks some of the wavelengths from reaching us at the surface.

Elements of gravitational waves

General relativity is a theory of gravity that is consistent with special relativity in many respects, and in particular with the principle that nothing travels faster than light. This means that changes in the gravitational field cannot be felt everywhere instantaneously they must propagate. In general relativity they propagate at exactly the same speed as vacuum electromagnetic waves the speed of light. These propagating changes are called gravitational waves.

An example of photoionization modelling without a satisfactory solution the mostmetalpoor galaxy I ZW 18 Stasiska

The observational constraints were provided by narrow-band imaging in nebular lines and the stellar continuum, together with optical spectra giving nebular line intensities. The ionizing-radiation field was given by a stellar-population synthesis model aimed at reproducing the observed features from hot Wolf-Rayet stars. The conclusion from the modelling exercise was that, even taking into account strong deviations from the adopted spectral energy distribution of the ionizing radiation and the effect of postulated additional X-rays, the photoionization models yield an O III A4363 5007 ratio that is too low by about 30 .* This significant discrepancy cannot be solved by invoking expected inaccuracies in the atomic data. The missing energy is of the same order of magnitude as the one provided by the stellar photons.

The search for extraterrestrial life

The spectral emission signatures of oxygen, water vapor and carbon dioxide are all in the infrared part of the electromagnetic spectrum. The search for evidence of extraterrestrial life will be facilitated by the lunar infrared telescopes placed in the permanently-shadowed regions of the Moon, where continuous cooling of the detectors may be possible without the use of cryogenic liquids.

Wave optics and polarization

Optical phenomena may be divided mainly into four areas, such as geometrical optics, wave optics, quantum optics, and statistical optics. Geometrical optics is the study of optics when the propagation of light is described using ray tracing. It deals with the image formation and related phenomena that can be discussed within the framework of the laws concerning reflection, refraction, and rectilinear propagation. This can be applied in those cases where interference and diffraction phenomena are ignored. It has found an application in the method of ray tracing widely used in optical design. Physical (or wave) optics that helps in describing diffraction and interference phenomena at length, is founded on Maxwell's equations, according to which, light is composed of electromagnetic waves of different frequencies. Light is an electromagnetic radiation, propagating disturbance involving space and time variation. A wave may be described as a periodic disturbance that transports energy from...

Cosmic radiation and the solar wind

The lack of an atmosphere on the Moon permits the cosmic radiation and solar wind plasma to reach the lunar surface unimpeded. Thus, analogous to the advantages of lunar-based observations of electromagnetic radiation, detectors can be placed on the lunar surface to study the origins, character, and directions of cosmic radiation. Similarly, measurements of the solar wind can be made directly from the lunar surface.

Probing the Milky Way Galaxy with XRays

For most of the history of astronomical observation, astronomers have had detectors sensitive only in the visible part of the electromagnetic spectrum. From before recorded history to the time of Galileo (1564-1642), the only available detector was the human eye. Having evolved on a planet illuminated by a sun that puts out most of its energy in the yellow green part of the visible spectrum, the human eye is an ideal detector for very bright or nearby stars and for objects that glow in reflected starlight. The sun, moon, planets, and other stars are easily visible in this part of the electromagnetic spectrum. But by the nineteenth and twentieth centuries, scientists realized that the visible part of the spectrum is only a tiny fraction of the whole.

Photon and nonphoton astronomy

Photons (electromagnetic waves) The astronomical light that arrives at the earth from a distant source is known as electromagnetic radiation. This radiation can be described in terms of waves or in terms of photons. Electromagnetic waves are propagating electric and magnetic fields whereas photons are discrete bundles of energy. These two descriptions of light are difficult to reconcile with one another intuitively. Both are correct the radiation can behave as one or the other under different circumstances. The electromagnetic waves described by Maxwell's equations are encountered as radio waves, infrared radiation, optical light, ultraviolet radiation, x rays and gamma rays. These different names simply specify ranges of wavelengths or frequencies. The lowest frequencies (or longest wavelengths) are radio waves, and the highest frequencies (or shortest wavelengths) are gamma rays. In the discrete picture, the photons, or quanta, carry energy and momentum much as a mass-bearing...

High energy astronomy

All of the telescopes that we have discussed so far have been for electromagnetic radiation. High energy phenomena also make their presence known in other ways. One way is by the emitting beams of cosmic rays, charged particles, often with very high energies. They also give off neutrinos, subatomic particles that are very difficult to detect. They also give off gravitational radiation,

Observations and Instruments

Astronomical photography was introduced at the end of the 19th century, and during the last few decades many kinds of electronic detectors have been adopted for the study of electromagnetic radiation from space. The electromagnetic spectrum from the shortest gamma rays to long radio waves can now be used for astronomical observations.

Threeplusone View Versus Geometric View

The electromagnetic field is a good example. In geometric language, it is described by a second-rank, antisymmetric tensor ( 2-form ) F, which requires no coordinates for its definition. This tensor produces a 4-force on any charged particle given by Not only is the geometric view far simpler than the 3 + 1 view, it can even derive the 3 + 1 equations with greater ease than can the 3 + 1 view itself. Consider, for example, the transformation law (3.23) for the electric and magnetic fields. The geometric view derives it as follows (1) Orient the axes of the two frames so their relative motion is in the z-direction. (2) Perform a simple Lorentz transformation (equation 2.45) on the components of the electromagnetic field tensor

The Energy Reservoir Model

Picture, it is assumed that large amounts of accretion power are stored in the accretion flow before being channelled either into the jet (responsible for the variable optical emission) or into particle acceleration heating in the Comptonising region responsible for the X-rays. MMF04 have developed a time-dependent model which is complicated in operation and behaviour. However, its essence can be understood using a simple analogue Consider a tall water tank with an input pipe and two output pipes, one of which is much smaller than the other. The larger output pipe has a tap on it. The flow in the input pipe represents the power injected in the reservoir P that in the small output pipe the X-ray power Px and in the large output pipe the jet power Pj. If the system is left alone the water level rises until the pressure causes P Pj + Px. Now consider what happens when the tap is opened more, causing Pj to rise. The water level and pressure (proportional to E) drop causing Px to reduce....

Matter with and without light

Atomic matter is the blossoming of all matter, making up for its weakness in numbers by its force of expression. For humankind, it is the sensorial manifestation of the Universe, its crowning eloquence. Indeed, it stands out by its expression in light, in stark contrast to dark matter which is totally indifferent to electromagnetic radiation, neither absorbing nor emitting it, in this respect a featureless entity.

Elementary Processes In Strong Magnetic Fields

Abstract The magnetic constriction of electronic orbits in strong magnetic fields (SMF) drastically modifies the properties of electronic matter, while SMF will even modify the properties of electromagnetic radiation in vacuum through such processes as polarization, pair creation, and photon splitting. We review the bulk properties of matter in SMF with emphasis on radiative opacities and transport in external magnetic fields appropriate for application to pulsars and magnetars. SMF changes in atomic matter and condensed matter at the surface layers of neutron stars are also touched upon.

Space Plasma and Spacecraft Charging

The arcing itself produces electromagnetic interference (EMI) that will generally be considered unacceptable. Such noise is not insignificant in the case of the shuttle, the EMI environment is dominated by plasma interaction noise. Solar arrays, which depend on maintaining a specified potential difference across the array, can develop arcs between exposed

The Search for Young Stars

Today searches for young stars are pursued throughout the entire electromagnetic spectrum (see Sect. 2.3.1) as a result of the accelerating development of technologies. To be more specific, searches today are performed in the Radio, Sub-mm, IR, and X-ray bands (see Sects. 2.3.2 and 2.3.3).

Drivers of space weather

The term space weather refers to a vast array of phenomena that can disturb the interplanetary medium and or affect the Earth and near-Earth environment. This includes recurrent structures in the solar wind (fast solar wind streams, co-rotating interaction regions), the ionizing radiation and hard particle radiations from flares, radio noise from the Sun, coronal mass ejections, and shock-accelerated particles. These drivers result in geomagnetic storms, changes in the ionosphere, and atmospheric heating which can, in turn, result in a large variety of effects that are of practical concern to our technological society ground-level currents in pipelines and electrical power grids, disruption of civilian and military communication, spacecraft charging, enhanced atmospheric drag on spacecraft, etc. A historical perspective of solar and solar radio effects on technologies is presented by Lanzerotti in Chapter 1. The drivers of space weather fast and slow solar wind streams, flares, and...

The Geometry of the Universe

12 to 15 billion years ago when the universe was much hotter, denser, and smaller than it is today. The photons we see as the CMB have been stretched by the expansion of the universe to the point that they are now detected in the long-wavelength (microwave) part of the electromagnetic spectrum. Early investigations seemed to show that the photons were distributed in a very smooth fashion across the sky. The question soon arose, however, that if the CMB were absolutely smooth, then how did the current roughness of the universe ever arise That is, how would galaxies and clusters of galaxies ever form if the early universe were perfectly uniform

Astronomical Technology and Techniques

The link between technological innovation and increased understanding has continued into the twentieth and twenty-first centuries. With the advent of enormous optical telescopes at the beginning of the twentieth century, and the development of telescopes and detectors sensitive to photons with wavelengths outside the tiny optical part of the electromagnetic spectrum in the 1930s, our understanding of the universe has grown in tandem with the development of new technologies (Figure 2.1). This chapter describes the state of the art in astronomical techniques, telescopes, and detectors and includes a description of the most advanced ground- and space-based telescopes in each portion of the electromagnetic spectrum.

Into The Next Millennium 19902000

The 1990s ushered in an era of cooperation among other nations as well. During the 1970s, the European Space Agency and nations such as Japan had developed their own independent access to space, often competing with the United States, particularly in the commercial use of space. As the century ended, they frequently collaborated with NASA on major space research projects. In 1990, NASA and the European Space Agency deployed the Hubble Space Telescope to provide detailed observational coverage of the visible and ultraviolet portions of the electromagnetic spectrum. This was the first of NASA's great observatories designed to increase our understanding of the origins and evolution of the universe. The following year, NASA deployed the Compton Gamma Ray Observatory to investigate some of the most puzzling mysteries of the universe gamma-ray bursts, pulsars, quasars, and active galaxies. The Chandra X-Ray Telescope was deployed in 1999 to detect X-ray sources that are billions of...

Gravitation Acceleration and the Principle of Equivalence

Compare electromagnetism and gravitation. Space seems to exist independently of any electromagnetic fields present. A charged particle responds to an electromagnetic field, but an uncharged particle moves in space as if the field were not present at all. Not so with gravitation All particles react to the gravitational field, and in fact they all react in the same manner, independent of their mass or composition. Near the earth's surface this is exemplified by Galileo's law of falling bodies. The classical experiments of E tvos, and later improved versions, verify with remarkable accuracy that the gravitational acceleration of a body is indeed independent of its mass. Now, while a static electric field is governed by a single scalar Coulomb potential, nonstatic electromagnetic fields require a scalar potential and a vector potential, or, briefly, a 4-vector potential (this is discussed in Chapter 10, p. 121ff). A consequence of this is that electromagnetic disturbances are propagated...

Geosynchronous Orbits

Communication satellites serving the United States and most of Western Europe are in GEO. When your long-distance telephone call is routed through one of these robotic outposts, you will notice a time lag in the conversation. This is because radio is a form of electromagnetic radiation, which is propagated by variations in electric or magnetic fields, and therefore moves at the speed of light (300,000 km sec). A half-second time delay is introduced when your question to your distant friend travels up to the satellite and back again and your friend's answer performs the same journey in reverse.

Light from the Past Astrophysics

It now became possible, using the laws of physics, to trace the history of the universe back to the original 'big bang'. It was later realised that the function of light as a messenger extended to bringing news of the first moments of the universe, when massive energy was released in the form of electromagnetic radiation which is still around us.

Instrumentation Facilities and Bandpasses

Today searches for young stars are pursued throughout the entire electromagnetic spectrum as a result of the accelerating development of advanced technologies specifically for focal-plane instrumentation. Instrumental development is an essential part of stellar research, and astronomy in general always motivates the creation of new technologies. The goal is to gain increased sensitivity, increased spatial and spectral resolution, and increased wavelength coverage. Of course, one would like to achieve all this throughout most essential parts of the electromagnetic spectrum. For a short review readers are directed to J. Kastner's review on imaging science in astronomy 454 . In starformation research, observing efforts today engulf almost the entire spectral bandwidth from Radio to 7-radiation. In essence, it took the whole second half of the 20th century to conquer the electromagnetic spectrum technologically in its entire bandwidth for star-formation research. The following offers a...

The methods of astrophysics

The same principle was soon extended to other forces and other physical laws. Electromagnetic and nuclear forces all have their parts to play in the running of the universe. The sun is powered by nuclear fusion, its heat energy transported away in all directions by electromagnetic waves, subject to the laws of electromagnetism.

Gravitationalwave detectors

The gravitational wave spectrum is completely unexplored, and whenever a new electromagnetic waveband has been opened to astronomy, astronomers have discovered completely unexpected phenomena. This seems to me just as likely to happen again with gravitational waves, especially because gravitational waves carry some kinds of information that electromagnetic radiation cannot convey. Gravitational waves are generated by bulk motions of masses, and they encode the mass distributions and speeds. They are coherent and their low frequencies reflect the dynamical timescales of their sources. In contrast, electromagnetic waves come from individual electrons executing complex and partly random motions inside their sources. They are incoherent, and individual photons must be interpreted as samples of the large statistical ensemble of photons being emitted. Their frequencies are determined by microphysics on length scales much smaller than the structure of the astronomical system emitting them....

Expressed In Simplest Form

View the same electromagnetic field in a rocket frame moving in the direction of n with the velocity parameter a (not 2a factor 2 comes in because energy flow and energy density are components, not of a vector, but of a tensor). By employing the formulas for a Lorentz transformation (equation 3.23), or otherwise, show that the energy flux vanishes in the rocket frame, with the consequence that E and B are parallel. No one can prevent the z-axis from being put in the direction common to E and B. Show that with this choice of direction, Faraday becomes

Le Sages Theory in the Twentieth Century

Soon after the revival by Kelvin, many authors, including Lorentz (1900) and Brush (1911), attempted to substitute electromagnetic waves for Le Sage's corpuscles. Many of the most recent efforts have continued in this vein. The earliest such theory was due to Lorentz (1900). Assuming that space is filled with radiation of a very high frequency, Lorentz showed that an attractive force between charged particles (which might be taken to model the elementary sub-units of matter) would indeed arise, but only if the incident energy were entirely absorbed. This situation thus merely reinforced the previous difficulties noted above in Le Sage's own theory and served to discourage further research along this line. In essence, this same problem has continually thwarted all subsequent Le Sage-type models.

Bootstrapping Lunar Development

7 Since humanity has already visited the Moon with robots and humans, we clearly have the technology to get there. The current technological challenge is not so much getting there as it is learning how to remain there (addressing dust mitigation, resource extraction and utilization, ionizing radiation protection, and so on).

Atmospheric Absorption And Transmission

While the Earth's atmosphere provides the biosphere that we live in and protects life on the planet from harmful radiation from space, it is not so friendly to the pursuit of astronomy. The atmosphere absorbs and scatters incident electromagnetic radiation. It is the scattering of sunlight by air molecules that makes the sky seem blue Lord Rayleigh (1842-1919) showed that the scattering is inversely proportional to wavelength to the fourth power (A 4) and so blue photons are scattered much more strongly and reach our eyes from all directions. Scattered sunlight is also highly polarized (90 from the Sun), a fact that is easily demonstrated with Polaroid sunglasses by tilting your head from side to side while looking at the blue sky to see that the intensity changes with the angle of your sunglasses. Under certain conditions the atmosphere also emits radiation. Of more concern is the fact that the atmosphere disturbs the incoming waves through turbulent air motion which in turn limits...

Linear and nonlinear systems

Most waves encountered in physics are linear to a good approximation, at least as long as their amplitudes remain small. In the case of sound waves, musical instruments depend for their harmonious quality on the linearity of vibrations in air, on strings, etc. Electromagnetic waves such as light and radio waves are also linear, a fact of great importance in telecommunications. Oscillating currents in electric circuits are often linear too, and most electronic equipment is designed to operate linearly. Non-linearities that sometimes occur in faulty equipment can cause distortions in the output.

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