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--------------- 2729 - COSMIC RAYS - to explain an expanding Universe?
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- Einstein’s theory of relativity in 1905 determined the speed of light to be constant, independent of the relative motion of the light source or the observer, light always travels at 186,000 miles per second. Regardless of where you are or how fast you are moving the speed of the photon that you see will always be the same.
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- Is this true at all energy levels? Could it be that at very high energy levels light travels even faster. If in the early Universe light did travel faster then it would not have been necessary to invent the theory of “Cosmic Inflation” to explain the characteristics of today’s Universe.
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- If you look 12 billion light years in one direction and you look 12 billion light years in the opposite direction you see fundamentally the same Universe. But, there is no way for light, or temperature, or information to travel that distance of 24 billion lightyears in 12 billion lightyears.
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- That would be traveling faster than the speed of light. And, this same is true regardless of where in the Universe you are standing. The Universe appears to be “homogeneous” and “isotropic“. If light really was faster in the beginning then that could explain it.
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- One way to test this theory is to study cosmic rays. Cosmic rays are high energy protons entering the Earth’s upper atmosphere at near light speeds. When these particles collide with gas atoms in the atmosphere they produce a shower of other lower energy particles that can be detected striking the Earth’s surface.
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- No one knows where these cosmic rays come from or how they can attain such enormous energies. Some have been observed to have 100,000,000,000 times the energy of a proton at rest. To have this amount of energy the protons must have the kinetic energy with velocities near the speed of light.
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- Also, cosmic rays must have traveled millions or billions of light years across the Universe before arriving here. The space that cosmic rays are traveling through is not empty. Space is filled with the Cosmic Microwave Background Radiation.
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- If cosmic rays have energies over 10^19 electron volts then these photons will interact with the background radiation and create “pions“, or “pi-mesons“. Mesons are particles that are both “hadrons” and “bosons“. They are a quark and an anti-quark bound together by a “gluon“. ( See Review on Particle Physics to learn about these fundamental particles.)
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- There are 20 different types of mesons which have intermediate weights between the lightest particles, leptons, electrons and neutrinos, and the heaviest particles, baryons, protons and neutrons.
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- If these pi-mesons are truly created, than energy is required and the cosmic rays would slow down to maintain the Conservation of Energy. Space is in effect opaque to the passage of any photons that carry more energy than that needed to make pi-mesons. Space therefore functions as a kind of filter.
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- One cosmic ray experiment in Japan, Akeno Giant Air Shower Array, reported dozens of events where cosmic rays exceeded 3*10^20 electron volts. ( This is the energy of a baseball traveling at 100 mph , except it is with the mass of a proton).
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- Either the theory of relativity is breaking down at these high energies, or these cosmic rays are originating close enough to Earth that they have not had time to be slowed down by the Cosmic Microwave Background.
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- Or, the high energy cosmic rays may not be protons, hydrogen nuclei. They may be higher weight nuclei, like iron. Or, maybe the experiments have made an error in their measurements.
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- Utah has another experiment called Fly’s Eye that detects the fluorescent light cosmic rays create in the upper atmosphere when they collide with gas atoms. This was an attempt to detect which direction the rays were coming from.
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- However, because the rays are charged particles they are deflected by the magnetic fields and enter the Earth’s atmosphere from all directions. The very highest energy rays will travel a more direct line and scientists hope to use them to pinpoint their origin.
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- A third experiment is just coming on line in Argentina. Called the Auger experiment after Pierre Auger who discovered cosmic rays in 1938. He conducted research at Chicago in 1942 using hot-air balloons to study cosmic rays.
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- The Auger experiment in Argentina has 1,600 detectors over 1,200 square miles ( an area about the size of Delaware) located 600 miles west of Buenos Aires. Only one high energy particle strikes any given square mile of Earth in a century. That is why so many detectors are spread over such a wide area.
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- The detectors are an array of plastic water tanks, 5 feet tall, 12 feet diameter spaced at one-mile intervals. They will occasionally intercept a particle from the atmospheric cascade generate by cosmic rays.
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- As the particle crosses from air into water its speed changes, producing a supersonic shock wave in the water that in turn creates a flash of blue light that is detected. Other detectors have a fluorescence telescope that can detect the ultraviolet light emissions generated high up in the atmosphere. The two detections should allow scientists to pinpoint the direction of the rays origin.
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- This experiment should tell us whether high-energy cosmic rays are produced by jets of matter emitted by super massive black holes, or by gamma-ray busters.
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- Or, by stresses and strains generated in the topology of the early Universe.
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- Or, by spinning neutron stars within the Milky Way Galaxy.
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- Or, from a very young neutron star spinning at 3,000 times a second, producing strong magnetic fields that could slam these particles with incredible energies.
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- Or, could Einstein’s theory of relativity need to be modified for very high energies?
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- There is much to be learned about cosmic rays. You came along at a good time in human evolution.
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- May 3, 2020 763 2729
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--------------------- Sunday, May 3, 2020 -------------------------
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