Matter, Earth, And Sky
Matter, Earth, And Sky ===> https://cinurl.com/2t7ePT
At the moment, a hypothetical particle called the axion stands out as important. As well as being a strong candidate for dark matter, the existence of axions may provide answers to a few other persistent questions in physics such as the Strong CP Problem.
Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas met much resistance from the astronomical community, but her confirmed observations now create pivotal proof of the existence of dark matter. In honor of this crucial and historic piece of detective work toward establishing the existence of dark matter, the revolutionary Large Synoptic Survey Telescope recently received the name Vera C. Rubin Observatory.
If it exists, Galaxy X is a satellite galaxy to our Milky Way. Large galaxies like the Milky Way are thought to have many satellite galaxies that are too dim to see, dominated by dark matter, the mysterious unseen substance thought to make up 23 percent of the mass of the universe.
The ancient Greeks believed that there were four elements that everything was made up of: earth, water, air, and fire. This theory was suggested around 450 BC, and it was later supported and added to by Aristotle.
(Aristotle also suggested that there was a fifth element, aether, because it seemed strange that the stars would be made out of earthly elements. He would be surprised to learn that they are in fact made up of many elements found on earth, and are so hot they could be said to be on fire all the time!)
8-12 miles above the earth, rivers of air known as jet streams move above us. Several miles wide and 1-2 miles deep, these currents of air can have wind speeds as high as 250 miles per hour. To contrast, the strongest hurricanes have wind speeds between 150-200 miles per hour.
By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?
We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.
Classical elements typically refer to earth, water, air, fire, and (later) aether which were proposed to explain the nature and complexity of all matter in terms of simpler substances.[1][2] Ancient cultures in Greece, Tibet, and India had similar lists which sometimes referred, in local languages, to "air" as "wind" and the fifth element as "void".
While the classification of the material world in ancient Indian, Hellenistic Egypt, and ancient Greece into air, earth, fire, and water was more philosophical, during the Middle Ages medieval scientists used practical, experimental observation to classify materials.[3] In Europe, the ancient Greek concept, devised by Empedocles, evolved into the system of Aristotle and Hippocrates, who introduced systematic classification into the area, which evolved slightly into the medieval system, which for the first time in Europe became subject to experimental verification in the 1600s, during the Scientific Revolution.[4]
Modern science does not support the classical elements as the material basis of the physical world. Atomic theory classifies atoms into more than a hundred chemical elements such as oxygen, iron, and mercury. These elements form chemical compounds and mixtures, and under different temperatures and pressures, these substances can adopt different states of matter. The most commonly observed states of solid, liquid, gas, and plasma share many attributes with the classical elements of earth, water, air, and fire, respectively, but these states are due to similar behavior of different types of atoms at similar energy levels, and not due to containing a certain type of atom or substance.
Plato seems to have been the first to use the term "element (στοιχεῖον, stoicheîon)" in reference to air, fire, earth, and water.[10] The ancient Greek word for element, stoicheion (from stoicheo, "to line up") meant "smallest division (of a sun-dial), a syllable", as the composing unit of an alphabet it could denote a letter and the smallest unit from which a word is formed.
Aristotle added a fifth element, aether (αἰθήρ aither), as the quintessence, reasoning that whereas fire, earth, air, and water were earthly and corruptible, since no changes had been perceived in the heavenly regions, the stars cannot be made out of any of the four elements but must be made of a different, unchangeable, heavenly substance.[15] It had previously been believed by pre-Socratics such as Empedocles and Anaxagoras that aether, the name applied to the material of heavenly bodies, was a form of fire. Aristotle himself did not use the term aether for the fifth element, and strongly criticised the pre-Socratics for associating the term with fire. He preferred a number of other terms indicating eternal movement, thus emphasising the evidence for his discovery of a new element.[16] These five elements have been associated since Plato's Timaeus with the five platonic solids.
The Neoplatonic philosopher Proclus rejected Aristotle's theory relating the elements to the sensible qualities hot, cold, wet, and dry. He maintained that each of the elements has three properties. Fire is sharp, subtle, and mobile while its opposite, earth, is blunt, dense, and immobile; they are joined by the intermediate elements, air and water, in the following fashion:[17]
In the Pali literature, the mahabhuta ("great elements") or catudhatu ("four elements") are earth, water, fire and air. In early Buddhism, the four elements are a basis for understanding suffering and for liberating oneself from suffering. The earliest Buddhist texts explain that the four primary material elements are solidity, fluidity, temperature, and mobility, characterized as earth, water, fire, and air, respectively.[25]
The elemental system used in medieval alchemy was developed primarily by the anonymous authors of the Arabic works attributed to Pseudo Apollonius of Tyana.[31] This system consisted of the four classical elements of air, earth, fire, and water, in addition to a new theory called the sulphur-mercury theory of metals, which was based on two elements: sulphur, characterizing the principle of combustibility, "the stone which burns"; and mercury, characterizing the principle of metallic properties. They were seen by early alchemists as idealized expressions of irreducible components of the universe[32] and are of larger consideration within philosophical alchemy.
Japanese traditions use a set of elements called the 五大 (godai, literally "five great"). These five are earth, water, fire, wind/air, and void. These came from Indian Vastu shastra philosophy and Buddhist beliefs; in addition, the classical Chinese elements (五行, wu xing) are also prominent in Japanese culture, especially to the influential Neo-Confucianists during the medieval Edo period.
Plato, the Greek philosopher who lived in the 5th century B.C.E., believed that the universe was made of five types of matter: earth, air, fire, water, and cosmos. Each was described with a particular geometry, a platonic shape. For earth, that shape was the cube.
No, the night sky will not eventually end up completely black. It is true that the universe is expanding, which causes many stars to be farther and farther away from earth, and therefore causes them to be dimmer. But the expansion of the universe only affects the distance between galaxy groups. It does not affect the distance between stars inside a galaxy, or even the distance between galaxies in a group. On galaxy group scales and smaller, local gravity overpowers the universe's expansion. The stars in our Milky Way galaxy and in nearby galaxies are not increasing in their distance from the earth, despite the expansion of the universe. As a result, the stars in our galaxy and in nearby galaxies are not growing dimmer over time. Interestingly, almost all of the stars that you can see in the night sky with your naked eye are in our galaxy. This means that the expansion of the universe will have essentially no effect on the appearance of the night sky to the naked eye, no matter how long we wait. The night sky will not go completely dark because of the expansion of the universe.
In addition to all the stars in space, there is a lot of other matter, called dark matter, between us and the stars that can block starlight. This dark matter can include nebulae which are clouds of gas, interstellar dust or planets.
Ordinary matter makes up only about 5% of the universe. Dark energy, which cosmologists hypothesize drives the accelerating expansion of the universe by counteracting the force of gravity, accounts for about 70%. The last 25% is dark matter, whose gravitational influence binds galaxies together. Both dark matter and dark energy remain invisible and mysterious, but DES seeks to illuminate their natures by studying how the competition between them shapes the large-scale structure of the universe over cosmic time. 2b1af7f3a8