Sunday, January 1, 2023

3804 - DARK ENERGY - where dose it come from?


     3804  -  DARK  ENERGY  -   where dose it come from?    DarkEnergy is the energy causing the universe to expand at an ever increasing rate.   What could explain the crisis in cosmology?

           


            ---------  3804  -  DARK  ENERGY  -   where dose it come from

            -    In 1916, Einstein finished his Theory of General Relativity, which describes how gravitational forces alter the curvature of spacetime. Among other things, this theory predicted that the Universe is expanding, which was confirmed by the observations of Edwin Hubble in 1929.

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            -    Since then, astronomers have looked farther into space and, back in time,  to measure how fast the Universe is expanding,  called the Hubble Constant rate of universe expansion.  The rate is measured at 49,306 miles per hour for every million lightyears of distsnce. The more space betwewen the faster the rate of expansion of their separation.

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            -  These measurements have become increasingly accurate thanks to the discovery of the Cosmic Microwave Background (CMB) and observatories like the Hubble Space Telescope.

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            -    Astronomers have traditionally done this measurement in two ways: directly measuring it locally (using variable stars and supernovae) and indirectly based on redshift measurements of the CMB and cosmological models.

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            -    Unfortunately, these two methods have produced different values over the past decade. As a result, astronomers have been looking for a possible solution to this problem, known as the “Hubble Tension.”  The existence of “Early Dark Energy” may be the solution cosmologists have been looking for.

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            -    The direct method involves using supernovae as “standard candles” (distance markers) to conduct measurements on the local scale. The indirect method involves comparing measurements of the CMB with cosmological models – like the Lambda Cold Dark Matter (LCMD) model, which includes the presence of Dark Matter and Dark Energy.

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            -   Unfortunately, these two methods produce different results, the former yielding a value of 73 km/s per megaparsec (Mpc) and the latter yielding 67 km/s Mpc. Mpc is a Megaparsec and it is a distance of 3,262,000 lightyeasrs.

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            -    The “Hubble constant” is the present rate at which the Universe expands. The “Hubble tension” is a discrepancy in the value you find for the Hubble constant when you either measure the expansion rate as best you can at present or you predict the value it should have based on the way the Universe looked after the Big Bang coupled with a model of how the Universe should evolve. Its a problem because if these two ways do not agree, it makes us think we are misunderstanding something about the Universe.

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            -    The mystery of the Hubble Tension is not as much of a problem as it is an opportunity for new discovery. So far, many candidates have been offered to explain the discrepancy, ranging from the existence of extra radiation, modified General Relativity (GR), Modified Newtonian Dynamics (MOND), primordial magnetic fields, or the existence of Dark Matter and Dark Energy during the early Universe that behaved in different ways. These can generally be divided into two categories: early-time (shortly after the Big Bang) and late-time solutions (more recently in cosmic history).

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            -    What makes EDE preferable to late-time solutions is how the latter implies the existence of a fluid that effectively creates energy out of nothing – which violates the strong energy condition predicted by GR. What’s more, such models are difficult to reconcile with the Cosmic Distance Ladder measurements of Cepheid variables and Type Ia supernovae in nearby galaxies (low-redshift targets) and Type Ia supernovae in distant galaxies (high-redshift).

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            January 1, 2022        DARK  ENERGY  -   where dose it come from?      3804                                                                                                                               

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            --------------------- ---  Sunday, January 1, 2023  ---------------------------

             

             

             

             

                     

             

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