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Adrian Lewis
Adrian Lewis

Precision Cosmology : The First Half Million Years [CRACKED]



Over the course of six years, from 2013 to 2019, DES used 30% of the time on the Blanco Telescope and surveyed 5000 square degrees -- almost one-eighth of the entire sky -- in 758 nights of observation, cataloging hundreds of millions of objects. The results announced today draw on data from the first three years -- 226 million galaxies observed over 345 nights -- to create the largest and most precise maps yet of the distribution of galaxies in the Universe at relatively recent epochs. The DES data were processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.




Precision cosmology : the first half million years



Ten regions of the sky were chosen as "deep fields" that the Dark Energy Camera imaged repeatedly throughout the survey. Stacking those images together allowed the scientists to glimpse more distant galaxies. The team then used the redshift information from the deep fields to calibrate the rest of the survey region. This and other advancements in measurements and modeling, coupled with a threefold increase in data compared to the first year, enabled the team to pin down the density and clumpiness of the Universe with unprecedented precision.


DES concluded its observations of the night sky in 2019. With the experience gained from analyzing the first half of the data, the team is now prepared to handle the complete dataset. The final DES analysis is expected to paint an even more precise picture of the dark matter and dark energy in the Universe.


Bottom line: Astronomers have taken a fresh look at the oldest light in the universe, otherwise known as the cosmic microwave background. Their new observations suggest that the universe is 13.77 billion years old, give or take 40 million years.


The map results suggest the universe is expanding more slowly than scientists thought, and is 13.8 billion years old, 100 million years older than previous estimates. The data also show there is less dark energy and more matter, both normal and dark matter, in the universe than previously known. Dark matter is an invisible substance that can only be seen through the effects of its gravity, while dark energy is pushing our universe apart. The nature of both remains mysterious.


The map, based on the mission's first 15.5 months of all-sky observations, reveals tiny temperature fluctuations in the cosmic microwave background, ancient light that has traveled for billions of years from the very early universe to reach us. The patterns of light represent the seeds of galaxies and clusters of galaxies we see around us today.


The age, contents and other fundamental traits of our universe are described in a simple model developed by scientists, called the standard model of cosmology. These new data have allowed scientists to test and improve the accuracy of this model with the greatest precision yet. At the same time, some curious features are observed that don't quite fit with the simple picture. For example, the model assumes the sky is the same everywhere, but the light patterns are asymmetrical on two halves of the sky, and there is a spot extending over a patch of sky that is larger than expected.


The newly estimated expansion rate of the universe, known as Hubble's constant, is 67.15 plus or minus 1.2 kilometers/second/megaparsec. A megaparsec is roughly 3 million light-years. This is less than prior estimates derived from space telescopes, such as NASA's Spitzer and Hubble, using a different technique. The new estimate of dark matter content in the universe is 26.8 percent, up from 24 percent, while dark energy falls to 68.3 percent, down from 71.4 percent. Normal matter now is 4.9 percent, up from 4.6 percent.


Until recently, astronomers estimated that the Big Bang occurred between 12 and 14billion years ago. To put this in perspective, the Solar System is thought to be 4.5billion years old and humans have existed as a genus for only a few million years.Astronomers estimate the age of the universe in two ways: 1) by looking for the oldeststars; and 2) by measuring the rate of expansion of theuniverse and extrapolating back to the Big Bang; just as crime detectives can trace theorigin of a bullet from the holes in a wall.


The life cycle of a star depends upon its mass. Highmass stars are much brighter than low mass stars, thus they rapidly burn through theirsupply of hydrogen fuel. A star like the Sun has enough fuel in its core to burn at itscurrent brightness for approximately 9 billion years. A star that is twice as massive asthe Sun will burn through its fuel supply in only 800 million years. A 10 solar mass star,a star that is 10 times more massive than the Sun, burns nearly a thousand times brighterand has only a 20 million year fuel supply. Conversely, a star that is half as massive asthe Sun burns slowly enough for its fuel to last more than 20 billion years.


All of the stars in a globular cluster formed at roughly the same time, thus they canserve as cosmic clocks. If a globular cluster is more than 20 million years old, then allof its hydrogen burning stars will be less massive than 10 solar masses. This implies thatno individual hydrogen burning star will be more than 1000 times brighter than the Sun. Ifa globular cluster is more than 2 billion years old, then there will be nohydrogen-burning star more massive than 2 solar masses.


Measurements by the WMAP satellite can help determine the age of the universe. The detailed structure of the cosmic microwave background fluctuations depends on thecurrent density of the universe, the composition of theuniverse and its expansion rate. As of 2013, WMAP determined these parameters with an accuracy ofbetter than than 1.5%. In turn, knowing the composition with this precision, we can estimate the age of the universe to about 0.4%: 13.77 0.059 billion years!


For a long time, the two largest mass extinctions got surprisingly little attention in geology textbooks. Part of the reason was the fragmentary nature of the fossil record. The layering of rocks and fossils is not neat and orderly throughout geological time. Volcanism, erosion, or metamorphosis of rocks can destroy some of the fossil evidence. Also, radioactive dating has limits. Let's say we could determine the age of 100-million-year-old rocks with a precision of 0.1%. The measurement error is still 100,000 years. This means that 100,000 years is the limit of our ability to resolve time. If we see the disappearance of many species over that interval, should we consider it gradual or catastrophic change? But as geologists found more fossils, their precision improved, and the extinctions seemed to be more dramatic.


The first mass extinction to be explained by direct scientific evidence was the one at the end of the Mesozoic, 65 million years ago. Approximately 75% of all species of plants and animals disappeared within a few million years, including the dinosaurs! In the early 1980s, geochemists made an interesting discovery about the thin layer of sediments at the boundary between Cretaceous and Tertiary rocks. It contained an excess of iridium, an element that is extremely rare in Earth's crustal rocks, but present in higher levels in meteorites. This discovery suggested that a giant meteorite impact might have been connected with the end of the Mesozoic. Further evidence supported this theory: the iridium layer was mixed in with glassy spheres formed by melted rock and quartz grains that had been heated and shocked suddenly. The extreme pressures required to do this can only be reached during a high-velocity impact. Scientists also discovered concentrations of soot that indicated worldwide forest fires.


In 1996, Oregon paleontologist Gregory Retallack presented evidence of shocked quartz grains from the layer at the end of the Paleozoic. Shocked quartz grains are usually accepted as evidence of an impact. Conceivably, an impact in the oceans or continental margins might have disturbed the oceans, and the crater could have been subsequently destroyed by plate tectonic activity. The fossil record this far back in time is quite patchy. Also, since radioactive techniques cannot date rocks with very high precision, it's difficult to distinguish between the rival hypotheses of a sudden catastrophe and a somewhat slower geological change. Even the story of the K-T extinction has got muddier in recent years. Geologists have pointed to a surge in volcanism that slightly preceded the impact and other craters of similar age have been found, so life may have been subject to multiple "punches." It's a lesson in the scientific method not to confuse correlation with causation. The race to explain the most dramatic episodes of dying in Earth's history continues.It's a sobering fact that we're in the midst of another mass extinction, this time by our own hand. Unlike the other mass extinctions caused by geological processes of impacts from space, the rapid loss of species currently is caused by environmental degradation, pollution, and the expanding human "footprint" on the planet. The current geological is called the Holocene, covering the past 12000 years since the dawn of civilization. Time will tell whether we can avert an environmental catastrophe.


The sixth annual Breakthrough Prize in Fundamental Physics has been awarded to an experiment that revolutionized cosmology and mapped the history of our universe. The $3 million prize was given to the science team and five leaders who worked on the Wilkinson Microwave Anisotropy Probe, which investigated matter, the Big Bang and the early conditions of our universe.


What is the cosmic microwave background?The cosmic microwave background (or CMB) fills the entire Universe and is leftover radiation from the Big Bang. When the Universe was born, nearly 14 billion years ago, it was filled with hot plasma of particles (mostly protons, neutrons, and electrons) and photons (light). In particular, for roughly the first 380,000 years, the photons were constantly interacting with free electrons, meaning that they could not travel long distances. That means that the early Universe was opaque, like being in fog. 041b061a72


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