Currently there are different types of radiometers, each with its own way of detecting and measuring electromagnetic wavelength, but the most popular model still remains to be the Crookes radiometer. Made in 1873 by a physicist named Edward Crooks, this model is one of the earliest to have been used. It is made of a spindle fitted with a rotor and a set of vanes inside a partial vacuum. The vanes, which are painted silver on one side and black on the other, rotate upon exposure to light. This motion is commonly explained by physicists as the result of the heat generated upon absorption of the blackened side of the vanes of the photons from the light. The Crookes radiometer is used to provide a quantitative measurement of electromagnetic radiation. In principle, the more intense the light is that hits the vanes, the faster the rotation will be.

But as popular as the Crookes radiometer is, its use has been usurped by newer models such as the MEMS and Nichols radiometer which tend to be more diverse and sensitive in measuring electromagnetic radiation.

Crookes Radiometer

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Light polarization, for one, is considered to be an essential phenomenon in this particular field of science. The much observed polarization of starlight gave way to the development of theories that use polarization data in tracing interstellar magnetic fields, thus furthering studies of astronomical objects way beyond our solar system.

Polarization has also given way to the study of the cosmic microwave background or CMB. This refers to the thermal radiation that uniformly spreads across the universe. CMB is essential to the study of the beginnings and earlier characteristics of our universe.

In the observation of extended astronomical objects like reflection nebulae, optical polarization can provide data on their nature, structure and even their dust content. The measurements of both the circular and linear polarizations of light waves coming form the Sun has also given scientists more information towards a much deeper understanding of the components of our very own star, its activities as well as its possible life span.

Polarization can also provide scientists with information on the various sources of radiation and scattering. This can be observed in both coherent and incoherent sources in interstellar space. Coherent radiation is capable of interference, while incoherent once tend to produce electromagnetic waves on its own.

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A radio wave actually pertains to a type of electromagnetic radiation. Like other types of waves in the electromagnetic spectrum, a radio wave is produced by acceleration of an electric charge and has both electric as well as magnetic components.

Waves of the electromagnetic spectrum are arranged either according to frequency or wavelength. The higher the frequency of the wave, the shorter is the wavelength and vice versa. In the waves of the electromagnetic spectrum ordered based on decreasing frequency, gamma rays come first, followed by x-rays, ultraviolet radiation, then visible light, infrared, and finally microwave and radio wave. This means that radio waves have the lowest frequency but the longest wavelength.

The existence of radio wave was discovered through the mathematical work of James Clerk Maxwell and demonstrated by Heinrich Hertz. What makes radio waves and other waves of the electromagnetic spectrum interesting is that they are able to travel even without the existence of a medium for transmission. They are, thus, able to travel from interplanetary or interstellar space toward the Earth.

The discovery of radio wave has brought about the existence of useful applications for man including in the fields of communication and medicine. For instance, radio frequency energy has long been used in less invasive medical procedures.

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All galaxies are capable of emitting electromagnetic radiation. In fact, even the Earth’s galaxy, the Milky Way, produces radio waves. A radio galaxy, however, compared to ordinary galaxies gives off as much as a thousand to a million times more energy per unit time. Basically, elliptical galaxies produce more radio waves than spiral ones and, as such, are perceived as the brightest in galaxy clusters.

Radio waves are produced when electrons move at light’s speed through the magnetic field, a process called synchrotron radiation. Because of the field being influenced by magnetism, it bends the electrons’ path leading to their release of energy.

With the gadgets scientists now have, they can detect radio wave emissions from the most distant parts of the universe. Interestingly, such emissions were produced in the past when the galaxies were still one-third of their current age. This means that such galaxies are so distant that the waves have only now reached the Earth. The ability to measure electromagnetic radiation makes possible the detection of how far such galaxies are from the Earth as well as their speed.

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Thus, everything in the universe can be analyzed using infrared detectors, including those that are very distant from the earth. Stars and heavenly bodies emit infrared wavelengths between 1 and 300 microns. These are not detectible by the human eye, but infrared instruments can identify them and glean important characteristics from the type of the radiation. In effect, infrared detectors can see what would otherwise be invisible and unknowable if only the naked eye and telescopes are used.

Light or electromagnetic radiation is of various wavelengths. Only a small fraction of these radiations are actually visible to people. The more distant the source of the radiation, the harder it is for the human senses to detect them. Galaxies are incredibly far, far away, and it is estimated that the human eye can see only less than 1% of the radiation they emit. It is a good thing then that infrared detectors have been invented to help astronomers uncover the wealth of information coming from all around the universe through infrared radiation.

Some infrared detectors were sent out in space, so that they can better detect electromagnetic signals without interference from the earth’s atmosphere. They detect various kinds of radiation within the infrared region, including near-infrared light, which refers to infrared wavelengths that are closest to visible light. There too is far-infrared light, referring to wavelengths farthest from visible light and closer to microwave radiation. In between the two is mid-infrared light.

Aside from infrared radiation and visible light, there too are gamma rays, X-rays, ultraviolet, microwave light, and radio waves. With the help of various instruments, astronomers study all these types of radiation coming from different parts of the universe to uncover more information.

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Most dictionaries would define the term as the process of energy (either in rays or waves) emission from a source. In physics, it is a process by which energized particles travel through space or another medium. There are different types of radiation of which the emission of energy from radioactive substances such as uranium is one; however, what is important in astronomy and the study of space is electromagnetic radiation. Under electromagnetic radiation, there are also several types from gamma rays, infrared radiation, radio waves, microwaves, synchrotron radiation, and many others.

The discovery of electromagnetic radiation began with James Clerk Maxwell. He postulated that light is composed of electromagnetic waves. However, his theory had many loopholes. It was not until Max Planck’s quanta of radiation that the phenomenon was viewed clearly. He proposed that the absorption and emission of radiation occur in fixed units of energy referred to as quanta. Later, Albert Einstein shed light into the process when he proposed that electromagnetic radiation behaved similarly with particles, which forms the foundation of what people know today about radiation.

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One of the topics not commonly tackled when talking about momentum is radiation pressure. Another name for radiation pressure is light pressure since it refers to the force exerted by an individual photon (usually a quantum of visible light but can also pertain to any other type of electromagnetic radiation). With momentum being a property of most objects, it is not surprising that even a small photon can possess such characteristics. In fact, the photon might not have mass or electrical charge but has energy and momentum. This is where it becomes complicated because if momentum is computed by multiplying the mass of an object by its velocity, how can a photon that does not have mass, have momentum?

The answer: because it is momentum that actually determines the amount of pressure or force that a particular object exerts on a surface, even photons that technically do not have mass can be said to have such property. However, instead of referring to the force exerted by the photon as momentum, it is called pressure; thus, the use of the term radiation pressure with radiation referring to electromagnetic radiation. Technically, radiation pressure is the pressure exerted on any surface that is exposed to electromagnetic radiation.

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There are more than five hundred pulsars that have been identified in the Milky Way (the Earth’s galaxy). Before, the existence of pulsars was merely based on predictions with astronomers unsuccessful in finding one. It was not until the time of Jocelyn Bell and Antony Hewish that the first pulsar was identified and named PSR 1919+21.

Pulsars are actually detected from a neutron star’s powerful radio wave emissions. A neutron star is named as such since it is composed of minute neutrons. It is formed from the remnants of a supergiant, a star in the advanced stages of evolution. Because of the massiveness of a supergiant, it collapses under its own weight when no nuclear reaction can occurs because of the exhaustion of its nuclear fuel. This explosion of a supergiant is what is referred to as supernova.

When the supergiant collapses, material most distant to its center folds in. This coupled with the spinning of the star on its axis, causes the star to pick up rotational speed as the material moves in closer (This can be likened to a figure skater who gains more speed as she folds her hands closer to her body.). The result is a superdense flattened neutron star of about 20 km in diameter that spins about a hundred times per second.

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Observed gamma ray burst is outside Milky Way. There are theories that if a gamma ray burst would occur in Milky Way, there would probably be a mass extinction in earth.

Gamma ray burst is first detected using satellites designed to sense nuclear weapon tests. These are US military satellites searching for Soviet?s nuclear testing in the atmosphere. A nuclear explosion can emit gamma rays. These satellites have gamma ray detectors and then that?s how gamma ray burst was discovered.

There are two classifications of gamma ray bursts. The long gamma ray bursts and the short gamma rays. They are classified based on the duration of the bursts. The long gamma ray bursts that lasts from two seconds or more and the short gamma ray that lasts in less than two seconds.

Gamma Ray Burst (GRB)

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Gamma ray

All ionizing radiation can cause damage at a cellular level. Gamma rays penetrate and can cause severe and scattered damages throughout the body. Examples would be radiation sickness and cancer.

Gamma rays can kill living cells that?s why it is used widely in sterilizing medical instruments. The process is called irradiation. It can also be used to remove bacteria from foods and prevent fruit and vegetables to sprout to keep its flavor and freshness.

Though gamma rays have properties that may cause cancer, it can also be used to treat some types of cancer. It can be used to kill the cancer cells, and the process is known as the gamma-knife surgery where its beams are directed on the cancer growth.

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