Dating the universe
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According to Censorinus quoting Varrothe second period mythikón lasted from 2137 to 776 BC, or if Censorinus' own dates are used: 2376 BC to 776 BC, or finally if Castor's: 2123 BC to 776 BC. Some scholars dating the universe gone further, attempting to harmonise this biblical chronology with that of recordedthus establishing a date for creation in a modern calendar. The older dates stem from the Greek. Statistical Challenges in Modern Astronomy. Tim has been outspoken about his Christian faith and has vowed to sol until marriage to have sex. The first dating the universe theories indicating that the age of the universe might be finite were the studies offormalized in the mid-19th century. Whence was it born, and whence came this creation. Assuming an extra background of relativistic particles, for glad, can enlarge the error bars of the WMAP constraint by one order of magnitude. The Persian Zoroastrian tradition places Zoroaster around the 7th or 6th century BC, since the 34. In 1915 published the theory of and in 1917 constructed the first based on his theory. So a tout estimate of the age of the universe comes from thethe inverse of the Hubble parameter.
This article is about scientific estimates of the age of the universe. For religious and other non-scientific estimates, see. In , the age of the universe is the elapsed since the. The has been narrowed down to 21 million years, based on a number of projects that all give extremely close figures for the age. These include studies of the , and by the , the and other probes. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang, and measurements of the of the universe can be used to calculate its approximate age by extrapolating backwards in time. The describes the evolution of the universe from a very uniform, hot, dense primordial state to its present state over a span of about 13. This model is well understood theoretically and strongly supported by recent high-precision such as. In contrast, theories of the origin of the primordial state remain very speculative. Since the universe must be at least as old as the oldest things in it, there are a number of observations which put a lower limit on the age of the universe; these include the temperature of the coolest , which gradually cool as they age, and the dimmest of in clusters lower-mass stars spend a greater amount of time on the main sequence, so the lowest-mass stars that have evolved off of the main sequence set a minimum age. The value of the age correction factor, F, is shown as a function of two : the current fractional matter density Ω m and cosmological constant density Ω Λ. The of these parameters are shown by the box in the upper left; the matter-dominated universe is shown by the star in the lower right. The problem of determining the age of the universe is closely tied to the problem of determining the values of the cosmological parameters. Today this is largely carried out in the context of the model, where the universe is assumed to contain normal baryonic matter, cold , radiation including both and , and a. The fractional contribution of each to the current energy density of the universe is given by the Ω m, Ω r, and Ω Λ. If one has accurate measurements of these parameters, then the age of the universe can be determined by using the. This equation relates the rate of change in the a t to the matter content of the universe. Turning this relation around, we can calculate the change in time per change in scale factor and thus calculate the total age of the universe by this formula. The first observation that one can make from this formula is that it is the Hubble parameter that controls that age of the universe, with a correction arising from the matter and energy content. So a rough estimate of the age of the universe comes from the , the inverse of the Hubble parameter. To get a more accurate number, the correction factor F must be computed. In general this must be done numerically, and the results for a range of cosmological parameter values are shown in the figure. To make this figure, Ω r is held constant roughly equivalent to holding the temperature constant and the curvature density parameter is fixed by the value of the other three. Apart from the Planck satellite, the Wilkinson Microwave Anisotropy Probe was instrumental in establishing an accurate age of the universe, though other measurements must be folded in to gain an accurate number. It is not as sensitive to Ω Λ directly, partly because the cosmological constant becomes important only at low redshift. The most accurate determinations of the Hubble parameter H 0 come from. Combining these measurements leads to the generally accepted value for the age of the universe quoted above. This is significant, since before the cosmological constant became generally accepted, the Big Bang model had difficulty explaining why in the Milky Way appeared to be far older than the age of the universe as calculated from the Hubble parameter and a matter-only universe. Introducing the cosmological constant allows the universe to be older than these clusters, as well as explaining other features that the matter-only cosmological model could not. However, this age is based on the assumption that the project's underlying model is correct; other methods of estimating the age of the universe could give different ages. Assuming an extra background of relativistic particles, for example, can enlarge the error bars of the WMAP constraint by one order of magnitude. This measurement is made by using the location of the first acoustic peak in the power spectrum to determine the size of the decoupling surface size of the universe at the time of recombination. The light travel time to this surface depending on the geometry used yields a reliable age for the universe. Assuming the validity of the models used to determine this age, the residual accuracy yields a margin of error near one percent. This is referred to as and essentially involves stripping the potential errors in other parts of the model to render the accuracy of actual observational data directly into the concluded result. To best avoid the problem, it is common to show two sets of uncertainties; one related to the actual measurement and the other related to the systematic errors of the model being used. An important component to the analysis of data used to determine the age of the universe e. This quantifies any uncertainty in the accuracy of a measurement due to a particular model used. Main articles: and In the 18th century, the concept that the was millions, if not billions, of years began to appear. However, most scientists throughout the 19th century and into the first decades of the 20th century presumed that the universe itself was and eternal, with maybe stars coming and going but no changes occurring at the largest scale known at the time. The first scientific theories indicating that the age of the universe might be finite were the studies of , formalized in the mid-19th century. The concept of dictates that if the universe or any other closed system were infinitely old, then everything inside would be at the same temperature, and thus there would be no stars and no life. No scientific explanation for this contradiction was put forth at the time. In 1915 published the theory of and in 1917 constructed the first based on his theory. In order to remain consistent with a steady state universe, Einstein added what was later called a to his equations. However, already in 1922, also using Einstein's theory, , and independently five years later , showed that the universe cannot be static and must be either expanding or contracting. Einstein's model of a static universe was in addition proved unstable by. The first direct observational hint that the universe has a finite age came from the observations of '', mostly by , combined with distances to the '' by in a work published in 1929. Earlier in the 20th century, Hubble and others resolved individual stars within certain nebulae, thus determining that they were galaxies, similar to, but external to, our. In addition, these galaxies were very large and very far away. In addition, the farther away these galaxies seemed to be the dimmer they appeared to us the greater was their redshift, and thus the faster they seemed to be moving away. This was the first direct evidence that the universe is not static but expanding. The first estimate of the age of the universe came from the calculation of when all of the objects must have started speeding out from the same point. Hubble's initial value for the universe's age was very low, as the galaxies were assumed to be much closer than later observations found them to be. The first reasonably accurate measurement of the rate of expansion of the universe, a numerical value now known as the , was made in 1958 by astronomer. His measured value for the Hubble constant came very close to the value range generally accepted today. However Sandage, like Einstein, did not believe his own results at the time of discovery. Sandage and other astronomers repeated these measurements numerous times, attempting to reduce the and thus increase the resulting age for the universe. Sandage even proposed new theories of to explain this discrepancy. This issue was finally resolved by improvements in the theoretical models used for estimating the ages of stars. The discovery of announced in 1965 finally brought an effective end to the remaining scientific uncertainty over the expanding universe. It was a chance result from work by two teams less than 60 miles apart. In 1964, and were trying to detect with a supersensitive antenna. The antenna persistently detected a low, steady, mysterious in the that was evenly spread over the sky, and was present day and night. After testing, they became certain that the signal did not come from the , the , or , but from outside our own galaxy, but could not explain it. At the same time another team, , , and , were attempting to detect low level noise which might be left over from the and could prove whether the Big Bang theory was correct. The two teams realized that the detected noise was in fact radiation left over from the Big Bang, and that this was strong evidence that the theory was correct. Since then, a great deal of other evidence has strengthened and confirmed this conclusion, and refined the estimated age of the universe to its current figure. The space probes WMAP, launched in 2001, and , launched in 2009, produced data that determines the Hubble constant and the age of the universe independent of galaxy distances, removing the largest source of error. Retrieved 24 November 2016. The Astrophysical Journal Supplement Series. An Introduction to Modern Cosmology 2nd ed. Archived from on 24 February 2008. Statistical Challenges in Modern Astronomy. Sitzungsberichte in German : 778—786.
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