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  • General Science Notes On – Cosmology – For W.B.C.S. Examination.
    Posted on November 29th, 2019 in General Science
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    General Science Notes On – Cosmology – For W.B.C.S. Examination.

    সাধারণ বিজ্ঞান নোট – সৃষ্টিতত্ব – WBCS পরীক্ষা।

    Cosmology is a branch of astronomy that involves the origin and evolution of the universe, from the Big Bang to today and on into the future. According to NASA, the definition of cosmology is “the scientific study of the large scale properties of the universe as a whole.”Continue Reading General Science Notes On – Cosmology – For W.B.C.S. Examination.

    Cosmologists puzzle over exotic concepts like string theory, dark matter and dark energy and whether there is one universe or many (sometimes called the multiverse). While other aspects astronomy deal with individual objects and phenomena or collections of objects, cosmology spans the entire universe from birth to death, with a wealth of mysteries at every stage.

    History of cosmology 

    Humanity’s understanding of the universe has evolved significantly over time. In the early history of astronomy, Earth was regarded as the center of all things, with planets and stars orbiting it. In the 16th century, Polish scientist Nicolaus Copernicus suggested that Earth and the other planets in the solar system in fact orbited the sun, creating a profound shift in the understanding of the cosmos. In the late 17th century, Isaac Newton calculated how the forces between planets — specifically the gravitational forces — interacted.

    The dawn of the 20th century brought further insights into comprehending the vast universe. Albert Einstein proposed the unification of space and time in his General Theory of Relativity. In the early 1900s, scientists were debating whether the Milky Way contained the whole universe within its span, or whether it was simply one of many collections of stars. Edwin Hubble calculated the distance to a fuzzy nebulous object in the sky and determined that it lay outside of the Milky Way, proving our galaxy to be a small drop in the enormous universe. Using General Relativity to lay the framework, Hubble measured other galaxies and determined that they were rushing away from the us, leading him to conclude that the universe was not static but expanding.

    In recent decades, cosmologist Stephen Hawking determined that the universe itself is not infinite but has a definite size. However, it lacks a definite boundary. This is similar to Earth; although the planet is finite, a person traveling around it would never find the “end” but would instead constantly circle the globe. Hawking also proposed that the universe would not continue on forever but would eventually end.

    Cosmological missions & instruments

    Launched in November 1989, NASA’s Cosmic Background Explorer (COBE) took precise measurements of radiation across the sky. The mission operated until 1993.

    Although NASA’s Hubble Space Telescope is probably best known for its astounding images, a primary mission was cosmological. By more accurately measuring the distances to Cepheid variables, stars with a well-defined ratio between their brightness and their pulsations, Hubble helped to refine measurements regarding how the universe is expanding. Since its launch, astronomers have continued to use Hubble to make cosmological measurements and refine existing ones.

    Thanks to Hubble, “If you put in a box all the ways that dark energy might differ from the cosmological constant, that box would now be three times smaller,” cosmologist Adam Riess of the Space Telescope Science Institute said in a statement. “That’s progress, but we still have a long way to go to pin down the nature of dark energy.”

    NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) was a spacecraft that operated from 2001 to 2010. WMAP mapped tiny fluctuations in the cosmic microwave background (CMB), the ancient light from the early universe, and determined that ordinary atoms make up only 4.6 percent of the universe, while dark matter makes up 24 percent.

    “Lingering doubts about the existence of dark energy and the composition of the universe dissolved when the WMAP satellite took the most detailed picture ever of the cosmic microwave background,” said cosmologist Charles Seife in the journal Science.

    The European Space Agency’s Planck space mission ran from 2009 to 2013 and continued the study of the cosmic microwave background.

    The ESA is currently developing the Euclid mission, which should fly by the end of the decade. Euclid will study dark matter and dark energy with greater precision, tracing its distribution and evolution through the universe.

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