------------ 2748 - MATTER - missing matter in the Universe?
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- In the late 1990s, scientists made a prediction about how much “ordinary matter” there should be in the universe. About 5%, they estimated, should be regular stuff with the rest a mixture of dark matter and dark energy. But when cosmologists counted up everything they could see or measure at the time, they came up short. By a lot.
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- The sum of all the ordinary matter that cosmologists measured only added up to about half of the 5% what was supposed to be in the universe. This is known as the “missing baryon problem” and for over 20 years, scientists have looked hard for this matter without success. Baryons is just another name for Ordinary Matter.
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- Baryon is a classification for types of particles that encompasses protons and neutrons, the building blocks of all the ordinary matter in the universe. Everything on the periodic table and pretty much anything that you think of is made of baryons.
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- Since the late 1970s, cosmologists have suspected that dark matter to be an unknown type of matter that must exist to explain the gravitational patterns in space. It makes up most of the matter of the universe with the rest being baryonic matter, but they didn’t know the exact ratios. Gravity is the force that depends on mass, or matter, and decays as the square of distance of separation.
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- In 1997, scientists used the ratio of heavy hydrogen nuclei, that is hydrogen with an extra neutron, to normal hydrogen to estimate that baryons should make up about 5% of the mass-energy budget of the universe.
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- Other cosmologists reported that a direct measure of baryons in our present universe by determining through a census of stars, galaxies, and the gas within and around them added up to only half of the predicted 5%, or 2.5% being ‘Ordinary Matter”.
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- This sparked the “missing baryon problem“. Provided the law of nature held that matter can be neither created nor destroyed, there were two possible explanations: Either the matter didn’t exist and the math was wrong, or, the matter was out there hiding somewhere.
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- In 2001, astronomers confirmed the initial prediction of baryons making up 5% of the universe by looking at tiny temperature fluctuations in the universe’s cosmic microwave background which is essentially the leftover radiation from the Big Bang. With two separate confirmations of this number, the math had to be right.
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- In 2007, astronomers made the discovery of a cosmological phenomenon known as a fast radio burst (FRB). FRBs are extremely brief, highly energetic pulses of radio emissions. Cosmologists and astronomers still don’t know what creates them, but they seem to come from galaxies far away.
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- As these bursts of radiation traverse the universe and pass through gasses and undergo something called ‘dispersion“.
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- The initial mysterious cause of these FRBs lasts for less a thousandth of a second and all the wavelengths start out in a tight clump. To be near the spot where an FRB was produced, all the wavelengths would hit simultaneously.
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- But when radio waves pass through matter, they are briefly slowed down. The longer the wavelength, the more a radio wave interacts with the matter. Think of it like wind resistance.
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- This “wind resistance” effect on radio waves is incredibly small, but space is big. By the time an FRB has traveled millions or billions of light-years to reach Earth, dispersion has slowed the longer wavelengths so much that they arrive nearly a second later than the shorter wavelengths, or higher frequencies.
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- Therein lay the potential of FRBs to weigh the universe’s baryons. By measuring the spread of different wavelengths within one FRB, we could calculate exactly how much matter, how many baryons, the radio waves passed through on their way to Earth.
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- To precisely measure the baryon “density“, astronomers need to know where in the sky an FRB came from. If we knew the source galaxy, we would know how far the radio waves traveled. With that and the amount of dispersion they experienced, they could calculate how much matter they passed through on the way to Earth?
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- The first FRB astronomers detected came from a galaxy that is about 4 billion light-years away from Earth. Astronomers were able to measure the dispersion from an FRB and knew where it came from.
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- By July 2019, astronomers had detected five more events which was enough to perform the first search for the missing matter. Using the dispersion measures of these six FRBs, they were able to make a rough calculation of how much matter the radio waves passed through before reaching earth.
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- The data predicted the same 5% estimate. The excellent correspondence confirms the detection of all the missing matter. Astronomers were able to estimate the amount of baryons, but with only six data points, you can’t yet build a comprehensive map of the missing baryons.
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- The missing matter is believed to be part of a vast filamentary network of gas that connects galaxies termed “the cosmic web,” but if astronomers had about 100 fast radio bursts they could start building an accurate map of this web.
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- Understanding fast radio bursts will help us learn more about parallel universes, why time seems to move in one direction only, and why we don’t understand chaos. No matter how astronomers crunch the numbers, the universe simply doesn't add up.
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- One example is what is dark matter? Evidently, about 84 percent of the matter in the universe does not absorb or emit light. "Dark matter," as it is called, cannot be seen directly, and it hasn't yet been detected by indirect means.
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- Dark matter's existence and properties are inferred from its gravitational effects on visible matter, radiation and the structure of the universe. This shadowy substance is thought to pervade the outskirts of galaxies, and may be composed of "weakly interacting massive particles," or WIMPs.
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- Worldwide, there are several detectors on the lookout for WIMPs, but so far, not one has been found. One recent study suggests dark mater might form long, fine-grained streams throughout the universe, and that such streams might radiate out from Earth like hairs.
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- Matter and energy are two forms of the same thing. Another example of unknowns is what is Dark Energy? What is mysterious energy that even though gravity is pulling inward on space-time this energy keeps expanding outward faster and faster. To account for this, astronomers have proposed an invisible agent that counteracts gravity by pushing space-time apart.
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- In the most widely accepted model of dark energy, it is a "cosmological constant": an inherent property of space itself, which has "negative pressure" driving space apart. As space expands, more new space is created, and with it, more dark energy.
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- Based on the observed rate of expansion, scientists know that the sum of all the dark energy must make up more than 70 percent of the total contents of the universe. But no one knows how to look for it. The best researchers have been able to do in recent years is narrow in a bit on where dark energy might be hiding.
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- Then astronomers are left with another mystery. Why is there more matter than antimatter? The question of why there is so much more matter than its oppositely-charged and oppositely-spinning twin, antimatter, is actually a question of why anything exists at all.
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- One assumes the universe would treat matter and antimatter symmetrically, and thus that, at the moment of the Big Bang, equal amounts of matter and antimatter should have been produced. But if that had happened, there would have been a total annihilation of both. Protons would have canceled with antiprotons, electrons with anti-electrons (positrons), neutrons with antineutrons, and so on, leaving behind a sea of photons in a matterless expanse.
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- For some reason, there was excess matter that didn't get annihilated, and here we are. I can’t explain this either. For this, there is no accepted explanation. The most detailed test to date of the differences between matter and antimatter confirm they are mirror images of each other, providing exactly zero new paths toward understanding the mystery of why matter is far more common.
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- The universe experiences four fundamental forces: electromagnetism, the strong nuclear force, the weak interaction (also known as the weak nuclear force) and gravity. To date, physicists know that if you turn up the energy enough, inside a particle accelerator, three of those forces "unify" and become a single force.
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- Physicists have run particle accelerators and unified the electromagnetic force and weak interactions, and at these higher energies, the same thing should happen with the strong nuclear force and, eventually, with gravity too.
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- But even though theories say that should happen, nature doesn't always oblige. So far, no particle accelerator has reached energies high enough to unify the strong force with electromagnetism and the weak interaction. Including gravity would mean yet more energy.
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- It isn't clear whether scientists could even build one that powerful; the Large Hadron Collider, can send particles crashing into each other with energies in the trillions of electron volts ( 14 tera-electron volts, or TeV). To reach grand unification energies, particles would need at least a trillion times as much, so physicists are left to hunt for indirect evidence of such theories.
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- Besides the issue of energies, Grand Unified Theories (GUTs) still have some problems because they predict other observations that so far haven't panned out. There are several GUTs that say protons, over immense spans of time (on the order of 10^36 years), should turn into other particles. This has never been observed, so either protons last much longer than anyone thought or they really are stable forever.
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- Another prediction of some types of this theory is the existence of magnetic monopoles which are isolated "north" and "south" poles of a magnet. Nobody has seen one of those, either. It's possible we just don't have a powerful enough particle accelerator. Or, physicists could be wrong about how the universe works.
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- This all leaves young science students with plenty to work on. So much we do not yet understand.
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------------------------------------ other Reviews available:
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- 2342 - The Waves of Matter. If all matter is waves then this could explain how matter interacts with all other matter in the Universe. Maybe some day we will understand how gravity is produced by matter. If all matter in the Universe is interconnected how big should the Universe be?
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- 2135 - MATTER - Atoms at Absolute Zero. There are at least six forms of matter. Everyone is familiar with three of them: gas, liquid, solid. If we keep cooling and adjusting temperatures and pressures on matter we can come across three more forms of matter: plasma, boson condensation, fermionic condensation. Learn about the strange properties matter acquires as temperatures approach -273 C, or 0 degrees Kelvin.
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- 2136 - Mayan Calendar. The ancient Maya were capable astronomers and their predictions must not be taken lightly. They had precise understanding of the Sun’s path throughout the year. They knew that December 21 was the shortest day of the year, winter season begins. They knew the phases of the Moon. They knew the movements of the 4 visible planets. The ancient Maya calendar predicts the end of the world on December 21.
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- May 28, 2020 2748
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--------------------- Friday, May 29, 2020 -------------------------
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