- 2873 - GAMMA RAYS - are photons Cosmic “Rays” are particles. Gamma ray mystery covering years of research? Gamma Rays are essentially high energy light. They started out with the Big Bang and have been loosing energy as they travel though an expanding Universe. But, they also include processes created by cosmic ray interactions with interstellar gas, supernova explosions and interactions of energetic electrons with magnetic fields.
--------------- 2873 - GAMMA RAYS - are photons Cosmic “Rays” are particles
- We are all familiar with the photons which are the light that reveals the world we can see. There is also infrared light that we can not see but we can feel Then there is higher frequency light in the Ultraviolet that we can not see but that gives us sunburns. There is still higher frequency called Gamma Rays that come from the Sun , but also from space. High power Gamma Rays coming from outer space remain a mystery Here is why?
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The Earth is being constantly bombarded from space by gamma rays cosmic rays of an unknown origin! Mysterious cosmic rays traveling at speeds approaching that of light constantly pelt Earth’s upper atmosphere from the depths of space, creating high-energy collisions that dwarf those produced in even the most powerful particle colliders. These atmospheric crashes rain down gigantic showers of secondary particles to the surface of our planet.
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- Despite being discovered more than a century ago, physicists still don’t know where cosmic rays come from. The short answer to why we can’t trace cosmic rays back to their source: magnetic fields. Charged cosmic-ray particles are redirected by the magnetic fields they pass through on their long journey through space. As magnetic fields in space have local, small, randomly oriented structures, a prediction of the exact path of a cosmic-ray particle is impossible.
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- What are cosmic rays? One thing we certainly do know about cosmic rays is that they are comprised of extremely energetic charged particles , like protons, alpha particles, and atomic nuclei like helium and iron, and miniscule proportions of antiparticles
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- It’s hard to imagine just how shocking the discovery of cosmic rays must have been to physicists in the early 1900s. The energies of these particles were monumental in comparison to those of every other particle they had observed until that point.
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- The average energy of a solar photon is approximately 1.4 electron volts (eV). For reference, a flying mosquito has an energy of about 1 trillion eV, or 1,000,000,000,000 eV, but a mosquito is also much, much larger than a single particle. Meanwhile, an alpha particle emitted during the decay of Uranium-238 possess 4,270,000 eV of energy.
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- Compare that to a cosmic ray proton, which has an energy of some 1x10^20 eV.
Imagine a proton that is accelerated so that it has an energy of 100 Joule. This energy corresponds to that of a tennis ball smashed by someone with a velocity of around 124 miles per hour. Only, the tennis ball 10^29 times heavier than the proton.
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- That means a proton can only reach that extreme, macroscopic energy by traveling at almost the speed of light. The universe must be able to accelerate particles to these energies, but we still do not know how it does it.
- We know that the processes that accelerate cosmic rays to such astounding energies must result from powerful and violent events.
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- One of the best ways of accelerating particles is a shock front that occurs when a medium with a large velocity runs into a slower one, producing a shock, a sudden change in the properties of the medium.
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- In the case of the universe, the changed properties are velocity and density, and even magnetic fields. Luckily for the cosmic rays, the field becomes highly turbulent in that process. And the combination of a shock front with turbulence is a great particle accelerator.
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- But what could produce such a shock front? One likely suspect is supernovae. As a shell of shocked material blasted away from an exploding star, it hits the cool interstellar medium that lies between stars, almost like a cosmic tsunami.
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- The phenomena of a traveling shock front can also be found in active galaxies, where huge plasma jet exist. Supernova remnants and active galaxies are the most promising candidates for cosmic-ray acceleration.
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- This research all began August, 1912, when Austrian-American physicist Victor Hess began a series of flights to the upper atmosphere in a hydrogen-filled balloon equipped with an electroscope. His aim was to take measurements of ionizing radiation. At the time, it was widely believed that radiation from the Earth itself was responsible for this phenomenon of knocking electrons off atoms. Should this be the case, however ionization should be strongest near the planet’s surface.
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- That’s not what Hess found. Hess discovered something startling. At an altitude of 3.3 miles, ionization rates of the air were three times that measured at sea level. He concluded that the source of this ionization was not coming from below our feet, but instead from above.
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- Further measurements made during a solar eclipse also showed the Sun wasn’t the source of this ionization radiation.
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- During the course of seven balloon trips, Hess discovered cosmic rays , later confirmed and named by Robert Millikan in 1925 , were coming from beyond our solar system. But, while the detection of cosmic rays has been associated with balloon flights ever since, the upper atmosphere isn’t the most convenient laboratory to investigate the high-energy particle collisions they produce.
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- To study the collisions caused by cosmic rays, particle physicists retreated below ground, employing increasingly monstrous particle accelerators to slam together particles in an attempt to replicate the collisions that cosmic rays spark in the upper atmosphere.
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- This quest has culminated with CERN’s Large Hadron Collider (LHC) with a 16-mile circumference deep beneath the French/Swiss border.
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- At roughly the same time a thrilling balloon ride changed our perspective of the universe forever, a physicist named Einstein was working on a wild theory that would radically change our understanding of the fabric of space-time. And this theory, many decades later, could provide the next step to decoding cosmic rays.
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- The discovery of gravitational waves , ripples in space-time predicted by Einstein’s theory of general relativity, has made a new form of astronomy possible, allowing us to investigate events and objects that we could never hope to observe in the electromagnetic spectrum alone.
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- This combination of electromagnetic or “traditional” astronomy and gravitational-wave detections, along with detecting neutrinos, which are ghost-like particles with virtually no mass or electric charge is known as multi-messenger astronomy. And it has a significant role to play in future investigations of cosmic rays, and the high-energy universe.
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- The first detected gravitational-wave signal GW170817 came from the merger of two neutron stars and was observed in 2017. It was significant for both multi-messenger astronomy and identifying potential sources of cosmic rays. Not only did this violent merger become the first such event to be detected in both gravitational waves and electromagnetic radiation, but it also confirmed that the merger of compact stellar remnants can accelerate particles to great speeds, creating cosmic rays.
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- There is no other way than multi-messenger astronomy to understand the origin and impact of cosmic rays. Cosmic rays alone cannot give an answer, neither can gamma-rays or neutrinos for themselves. All three messengers have unique properties and show different parts of a big puzzle. Only by putting together all the pieces, can we see the full picture.
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- Gamma-rays are the highest frequency electromagnetic radiation and therefore have the highest energy levels in the electromagnetic spectrum.
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--------------------- Their wavelengths are 10^-2 to to 10^-14 meters.
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--------------------- Their frequency ranges from 10^10 to 10^22 cycles per second (hertz).
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--------------------- Their energy measured on a single photon ranges from 100,000 to 10,000,000 electron volts. In contrast visible light has and energy level of 2 to 3 electron volts.
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- The energy of a photon of electromagnetic radiation is given by:
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------------------------ Energy = Planck’s Constant * frequency of the radiation
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------------------------ E = h * f
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------------------------ Frequency = speed of light / wavelength
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------------------------ f = c / w
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------------------------ Planck’s constant = h = 6.624 * 10^-34 joule * seconds
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------------------------ Shortest Highest Highest
----------------------Wavelength Energy Temperature
-------------------Nanometers, 10^-9 m Electron volts Kelvin
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- Radio 10^7 10^-4 .03
- Microwave 4 * 10^5 3 * 10^-3 30
- Infrared 700 2 4100
- Visible 400 3 7300
- Ultraviolet 10 1000 3 * 10^6
- X ray 10^-2 100,000 3 * 10^8
- Gamma ray <10^-2 > 10^5 > 3 * 10^8
- Cosmic ray These are particles 10^9
- High Energy Cosmic ray 10^20
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- Gamma-rays are produced in the core of star’s nuclear reactions. Our Sun produces gamma-rays when its hydrogen is fused into helium. These gamma-rays fight their way to the surface of the Sun bouncing, absorbing and emitting, through all the particles in the very dense interior.
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- Gamma-rays finally reach the surface with much of their energy lost, emitting form the surface of the Sun with all the lower frequencies in the spectrum, including those of visible light.
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- The Sun’s core fusion starts with six hydrogen nuclei and ends with one helium nuclei and two hydrogen nuclei.
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---------------- The mass of six hydrogen nuclei is 6 * (1.674 * 10^-27 kilograms) = 10.044 * 10^-27 kilograms.
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--------------- The mass of one helium nuclei and 2 hydrogen nuclei is 6.643 * 10^-27 + 2 * (1.674 * 10^-27 kilograms) = 9.991 * 10^-27 kilograms.
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- The difference is 0.053 * 10^-27 kilograms which is converted into energy in the form of gamma rays, electromagnetic radiation, according to Einstein’s formula, E = m* c^2.
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------------------------ Energy = mass * (speed of light) ^2
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------------------------ Energy = 0.053 * 10^-27 kg * 8.98755 * 10^16 (m/sec)^2
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------------------------ Energy = 0.47 * 10^-11 joules
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------------------------ One Electron volt = 1.6 * 10^-19 joules
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------------------------ Energy = 0.3 * 10^8 electron volts
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- This amount of energy is multiplied 10^38 times every second to equal the energy output of the Sun. The luminosity of the Sun is 2.4 * 10^45 electron volts / second.
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- The Sun’s electromagnetic radiation striking the Earth’s atmosphere, covers the entire electromagnetic spectrum. The longer wavelength radiation penetrates the atmosphere to reach the Earth’s surface. This includes radio waves, infrared, light, and some ultraviolet.
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- The penetration of the atmosphere depends on the wavelength of the radiation in relation to the physical size of atoms and molecules that it encounters.
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- The shorter wavelengths hit particles more their own size. Gamma-ray has a wavelength of 10^-11 meters. The diameter of an atom is 10^-9 meters and its nucleus 10^-13 meters.
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- Red and yellow light wavelengths ( 7 * 10^-7 meters ) penetrate more easily than blue and ultraviolet. Blue light ( 4 * 10^-7 meters ) is one half the wavelength of redlight and is the first of the shorter wavelengths to begin to scatter in the atmosphere. That is why the sky is blue.
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- Ultraviolet, with shorter wavelengths still, is even more attenuated by the atmosphere. That is why you have trouble getting a tan in late afternoon because the ultraviolet wavelengths have to pass through more atmosphere in order to reach you.
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- X-rays and Gamma-rays have such short wavelengths that very little radiation can ever make it through the atmosphere and reach the ground.
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- It is a good thing that celestial gamma-rays dissipate their energies 10 to 300 miles above our heads because gamma-rays can kill living cells. In fact they are used in medicine to kill cancerous cells in radiation therapy.
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- Marie Sklodowska Curie, the Polish-French chemist who discovered radiation and X-rays, died of leukemia a form of cancer caused by the overexposure to radioactive radiation (1934).
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- Research in celestial gamma-rays needs to use instruments held aloft in high altitude balloons or in satellites. The first gamma-ray telescope was carried into orbit in 1961. When this was first done astronomers were surprised to learn that great bursts of gamma-rays were being seen all over the cosmos.
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- They are now being detected at the rate of about one per day. Supernova explosions, neutron stars, pulsars, and black holes are all sources of celestial gamma-rays.
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- Gamma-ray telescopes can not use lenses and mirrors because this radiation passes right through them. These telescopes use Compton scattering to detect the gamma-rays.
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- Arthur Holly Compton was an American physicist born in Ohio in 1892. He got his Ph.D. at Princeton in 1916. In 1923 while studying X-rays he noted that scattering lengthened their wavelength. Arthur presumed that the photon of light struck an electron, which recoiled, subtracting some energy from the photon thereby increasing its wavelength.
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- It was Arthur who first named the “photon” to account for the light quantum in its particle aspect. He got the Noble prize in 1927 and worked on the Manhattan project in World War II. He was chancellor of Washington University in St. Louis until 1953.
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- The Compton scattering is measured when the gamma-rays strike electrons and lose energy, much the same way they lose energy high in Earth’s atmosphere. If the gamma-ray telescope looks at the moon it sees a round blob with no lunar features visible, but the blob is brighter than gamma-rays emitting from our quiet Sun.
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- However, solar flares, from a not so quiet Sun, would out shine the moon. The brightest gamma-ray objects in the sky would be spinning neutron stars and pulsars. The Crab Nebula pulsar would be a bright light in the sky.
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- The gamma-ray bursts that occur at least once per day, last for only 0.2 seconds up to 40 seconds, popping off like cosmic flashbulbs from unexpected directions, flickering, and fading after briefly dominating the gamma-ray sky. The energy released in a burst of 10 seconds can be more than our Sun will emit in its entire 10,000,000,000-year lifetime.
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- We expect to see a gamma-ray burst in our Milky Way once every few million years. So far, it appears that all of the bursts we have observed to date have come from far outside our Milky Way Galaxy.
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- After 25 years of study these gamma-ray bursts remain a mystery. The Compton Gamma-Ray Observatory was a satellite launched in 1991. Its gyro failed and it was de-orbited in June, 2000, after accumulating a large amount of data that is still being analyzed.
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- Gamma-rays are not to be confused with Cosmic Rays. Cosmic rays are actually bits of matter, normally, hydrogen nuclei, or protons. Sometimes, they are the positive ions, or nuclei from higher elements than hydrogen. They are charged pieces of atoms traveling at high speeds with enormous energies. They are distinguished from gamma-rays because their path can be bent in a magnetic field.
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- Gamma rays, like X-rays, are electromagnetic radiation that are massless and not affected by magnetic fields. Normally, cosmic rays arrive with energy levels of 10^9 electron volts. Very few exceed 10^16 electron volts. However, nearly a dozen incidents have been recorded of cosmic rays with 3 * 10^20 electron volts.
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- This high level of energy can not be explained. The generators must be quasars, or gamma-ray bursters, or some other cataclysmic generators. It is thought that positive ions with energies above 5 * 10^19 electron volts would be attenuated by the cosmic background radiation that pervades space.
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- Quasars are billions of lightyears away. Cosmic rays should have lost most of their energy by the time they reach us. The most energy production we can imagine are colliding galaxy clusters and magnetars, super dense stars with extremely high magnetic fields, but even these may not be able to create jets as high as we need to explain high energy cosmic rays.
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- The plastic helmet worn by Jim Lovell during Apollo 8 lunar mission in 1968 bears microscopic pits, 1/50 of an inch long, left by bombarding cosmic rays. This alerted researchers to the need for better shielding for astronauts during missions into deep space. We have much more to learn about high energy cosmic rays and high energy gamma-rays.
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- The photon has zero mass at rest and in a vacuum always travels at the same speed, 670,633,500 miles per hour. Photons begin moving at the speed of light at the moment of creation and keep moving at that speed until the moment of absorption.
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- A photon is emitted by an atom in 10^-8 seconds. And, it need be in the vicinity of an atom for only about 10^-8 seconds to have a good chance of being absorbed.
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- Ordinary light has a much longer wavelength than gamma-rays and takes longer to pass a single atom. Light is therefore more readily absorbed and rarely penetrates more than a couple of dozen atom-thicknesses into a solid.
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- In contrast, gamma-rays will penetrate 10 feet of lead before being absorbed.
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------------------------ Other Reviews about Gamma Rays and Cosmic Rays:
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- 2858 - COSMIC RAYS - where do they come from? Earth is being constantly bombarded from space by “cosmic rays” of an unknown origin! Mysterious cosmic rays traveling at speeds approaching that of light constantly pelt Earth’s upper atmosphere from the depths of space, creating high-energy collisions that dwarf those produced in even the most powerful particle colliders.
-
- 2825 - GAMMA RAYS - mystery covering years of research? Gamma Rays are essentially high energy light. They started out with the Big Bang and have been loosing energy as they travel though an expanding Universe. But, they also include processes created by cosmic ray interactions with interstellar gas, supernova explosions and interactions of energetic electrons with magnetic fields.
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- 2821 - GAMMA RAY BURSTS - how often it happens? Would you like to see the most powerful explosion that occurs in the Universe? Don’t worry you do not have to stand too close. These explosions are at least 2,000,000,000 lightyears away. They occur once a day on average and one of these occurred in the constellation Hydra. Log on to http://grb.sonoma.edu/ and see the sky map with the Gamma Ray Bursts exploding in real time.
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- 2330 - Monday, December 27, 2004, the brightest flash of light in our history passed by Earth . It came from a neutron star, a remnant of a giant star that ended its live in a supernova explosion. These giant stars start out at 30 to 40 times the mass of our Sun. They live short lives of only 10 million years before they have burned all their nuclear fuel down to an iron core.
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- 2329 - Gamma Rays and Cosmic Rays are totally different. Gamma Rays are high frequency, high power light waves. Cosmic Rays are high speed particles , atomic nuclei, mostly hydrogen protons, mostly coming from our Sun, but some from distant stars.
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- 1482 - Enormous Gamma Ray bubbles and jets are shooting out from our galaxy’s Blackhole. What is going on? If you travel far out into space and look back at the Milky Way Galaxy edge-on with a camera that detects light in the Gamma Ray frequency range your image includes two enormous “ bubbles”, “tear drops” above and below the galaxy center. And, there are two jets shooting up at a 15 degree angles to the perpendicular. How to explain this ?
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- 1323 - Other Gamma Ray Sources and Mysteries? What we “see” in our Universe is very limited, extremely limited. Our eyes can detect that part of the electromagnetic spectrum from about 400 to 700 nanometers wavelength. That is the wavelengths from blue light to red light and all the colors in between. We can use our radio receivers to detect the really long wavelengths. TV receivers, Microwave receivers detect other parts of the electromagnetic spectrum.
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- 1238 - Do Thunderstorms Create Anti-Matter with Lightning? Gamma Ray telescopes were launched into space to study distance sources of Gamma Ray radiation and flares. Imagine our surprise when the Gamma Ray flares were found coming from the tops of thunderstorms in the opposite direction we were looking.
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- 1160 - What Can Astronomers See with Gamma Rays? Astronomers are just beginning to see in Gamma Rays. Visible light has energies between 2 and 3 electron volts. An electron volt is the energy of a single electron moving through a voltage about the potential of a flashlight battery. A very small amount of energy. Gamma Rays are light photons of very high energy, in the 100,000 to 100,000,000 electron volts.
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- 1158 - Where Do Gamma Rays Come From? Gamma Rays are light of the maximum possible energy. With wavelengths shorter than 10^-11 meters, each Gamma Ray photon has an energy of at least 100,000 electron volts. That is 100,000 times more energy than visible light. Some Gamma Rays have even shorter wavelengths and even more energy. The most energetic Gamma Ray recorded was 100,000,000,000 electron volts.
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- 916 - Gamma Ray Telescopes. Electromagnetic radiation starts with radio waves and goes all the way up to Gamma Rays as the frequency increases. The energy of radiation is a function of frequency. So, as the frequency increases the energy in the photons increases. When you get up to Gamma Rays they can carry so much energy that they can actually convert back to mass, according to E=mc^2.
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- October 23, 2020 2873
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