Thursday, April 13, 2023

3956 - DARK MATTER - to explain the Universe?

 

-   3956 -    DARK  MATTER  -  to explain the Universe?    Einstein was right about invisible dark matter, a massive new map of the universe suggests.  Light produced just 380,000 years after the Big Bang was warped by the universe's dark matter exactly the way Einstein predicted it would be.


------------  3956  -  DARK  MATTER  -  to explain the Universe?

-    Astronomers have made the most detailed map ever of mysterious dark matter using the universe’s very first light, and the "groundbreaking" image has possibly proved Einstein right yet again.  The new image, made using 14 billion-year-old light from the turbulent aftermath of the Big Bang, shows the enormous matter tendrils that formed not long after the universe exploded into being.

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-    It turns out the shapes of these tendrils are remarkably similar to those predicted using Einstein's theory of general relativity.  The new result contradicts previous dark matter maps that suggested the cosmic web. the gigantic network of crisscrossing celestial superhighways paved with hydrogen gas and dark matter that spans the universe, is less clumpy than Einstein's theory predicted.

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-    This new result shows that both the 'lumpiness' of the universe, and the rate at which it is growing after 14 billion years of evolution, are just what you'd expect from our standard model of cosmology based on Einstein's theory of gravity.

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-    Scientists think that the universe that formed after the Big Bang teemed with matter as well as antimatter particles, which are identical to their matter counterparts but with opposite electrical charges.

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-    Because matter and antimatter annihilate each other when they collide, if both were made in equal measure, all of the universe's matter should have been annihilated. However, the rapidly expanding fabric of space-time, along with some helpful quantum fluctuations, kept pockets of the universe's primordial plasma intact.

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-    Then, according to the rules set out by Einstein's theory of relativity, gravity compressed and heated these plasma pockets so that sound waves, called baryon acoustic oscillations, rippled outward from the clumps at half the speed of light. These gigantic waves pushed out matter that hadn't already been sucked in on itself, creating the infant cosmic web: a series of thin films surrounding countless cosmic voids, like a nest of soap bubbles in a sink.

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-    Once this matter cooled, it coalesced into the first stars, which pooled into matter-rich galaxies at the meeting points of the web's tangled strands.  But in the past, astronomers studying the cosmic web found what seemed to be a massive discrepancy, the matter was significantly more evenly distributed and less lumpy than expected. It was an ominous sign that existing cosmological models were missing important physics.

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-    The  Atacama Cosmology Telescope (ACT) in Chile, which scanned a quarter of the entire night sky from 2007 to 2022. Using its incredibly sensitive microwave detector, the telescope picked up light from the cosmic microwave background radiation (CMB), the universe's very first light made just 380,000 years after the Big Bang, and used a process called gravitational lensing to map the concentrations of matter in the CMB.

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-    Gravitational lensing is a phenomenon in which light moving through a region of space-time warped by powerful gravitational fields travels, in a curve, warping and twisting through a gigantic funhouse mirror until it emerges as a stretched-out arc called an Einstein ring.

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-    Gravitational lensing can detect dark matter, which makes up 85% of the universe's matter but cannot be directly observed.  The new map contradicted previous ones made with visible light from galaxies, and showed that Einstein's original theory was far more accurate than first thought.

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-    Astronomers estimate that roughly 85% of all the matter in the universe is dark matter, meaning only 15% of all matter is normal matter. Accounting for dark energy, the name astronomers give to the accelerated expansion of the universe, dark matter makes up roughly 27% of all the mass energy in the cosmos.

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-    Astronomers have a variety of tools to measure the total amount of matter in the universe and compare that to the amount of "normal" (also called "baryonic") matter. The simplest technique is to compare two measurements.

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-   The first measurement is the total amount of light emitted by a large structure, like a galaxy, which astronomers can use to infer that object's mass.

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-     The second measurement is the estimated amount of gravity needed to hold the large structure together.

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-   When astronomers compare these measurements on galaxies and clusters throughout the universe, they get the same result: There simply isn't enough normal, light-emitting matter to account for the amount of gravitational force needed to hold those objects together.

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-   Thus, there must be some form of matter that is not emitting light: dark matter.

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-   Different galaxies have different proportions of dark matter to normal matter. Some galaxies contain almost no dark matter, while others are nearly devoid of normal matter. But measurement after measurement gives the same average result: Roughly 85% of the matter in the universe does not emit or interact with light.

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-    There are many other ways astronomers can validate this result. For example, a massive object, like a galaxy cluster, will warp space-time around it so much that it will bend the path of any light passing through an effect called gravitational lensing. Astronomers can then compare the amount of mass that we see from light-emitting objects to the mass needed to account for the lensing, again proving that extra mass must be lurking somewhere.

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-    Astronomers can also use computer simulations to look at the growth of large structures. Billions of years ago, our universe was much smaller than it is today. It took time for stars and galaxies to evolve, and if the universe had to rely on only normal, visible matter, then we would not see any galaxies today. Instead, the growth of galaxies required dark matter "pools" for the normal matter to collect in.

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-   Cosmologists can look back to when the cosmos was only a dozen minutes old, when the first protons and neutrons formed. Cosmologists can use our understanding of nuclear physics to estimate how much hydrogen and helium were produced in that epoch.

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-   These calculations accurately predict the ratio of hydrogen to helium in the present-day universe. They also predict an absolute limit to the amount of baryonic matter in the cosmos, and those numbers agree with observations of present-day galaxies and clusters.

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-    Alternatively, dark matter may be a misunderstanding of our theories of gravity, which are based on Newton's laws and Einstein's general relativity.  Astronomers can tweak those theories to provide explanations of dark matter in individual contexts, like the motions of stars within galaxies. But alternatives to gravity have not been able to explain all the observations of dark matter throughout the universe.

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-    All the evidence indicates that dark matter is some unknown kind of particle. It does not interact with light or with normal matter and makes itself known only through gravity.

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-    In fact, astronomers think there are trillions upon trillions of dark matter particles streaming through you right now. Scientists  hope to nail down the identity of this mysterious component of the universe soon.

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                   April 12, 2023       DARK  MATTER  -  to explain the Universe?           3956                                                                                                                         

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--------------------- ---  Thursday, April 13, 2023  ---------------------------

 

 

 

 

         

 

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