- 3716 - UNIVERSE - expansion rate still a ? Astronomer are still convinced that thee universe was created by a giant bang. The Big Bang occurred 13,800,000,000 years ago, and when the universe started to expand. The expansion is still ongoing today. The Universe is being stretched out in all directions like a balloon being inflated.
--------------------- 3716 - UNIVERSE - expansion rate still a ?
- Astronomers agree on this, but something is wrong. Measuring the expansion rate of the universe in different ways leads to different results in the rate and age. So, is something wrong with the methods of measurement? Or is something going on in the universe that physicists have not yet discovered and therefore have not taken into account?
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- Some astronomers propose the existence of a “new type of dark energy” in the universe.
When physicists calculate the expansion rate of the universe, they base the calculation on the assumption that the universe is made up of three parts, dark energy, dark matter and ordinary matter.
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- Conflicting results arise when looking at the latest data from measurements of supernovae and the “cosmic microwave background radiation“; the two methods quite simply lead to different results for the expansion rate.
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- If there was a “new” type of extra dark energy in the early universe, it would explain both the background radiation and the supernova measurements simultaneously and without contradiction.
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- Maybe in the early universe, dark energy existed in a different phase. You can compare it to when water is cooled and it undergoes a phase transition to ice with a lower density. In the same way, dark energy undergoes a transition to a new phase with a lower energy density, thereby changing the effect of the dark energy on the expansion of the universe.
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- It is a phase transition where many bubbles of the new phase suddenly appear, and when these bubbles expand and collide, the phase transition is complete. On a cosmic scale, it is a very violent quantum mechanical process.
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- Today we know approx. 20% of the matter that the universe is made of. It is the matter that you and I, planets and galaxies are made of. The universe also consists of dark matter, which no one knows what type of matter it is.
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- There is “dark energy” in the universe; it is the energy that causes the universe to expand, and it makes up approx. 70% of the energy density of the universe.
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- Astronomers using the Hubble Space Telescope have discovered that the universe is expanding 5 percent to 9 percent faster than expected. This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don't emit light, such as dark energy, dark matter, and “dark radiation“.
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- By refining the universe's current expansion rate to unprecedented accuracy, reducing the uncertainty to only 2.4 percent uncertainty. The astronomers looked for galaxies containing both Cepheid stars and Type 1a supernovae.
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- Cepheid stars pulsate at rates that correspond to their true brightness, which can be compared with their apparent brightness as seen from Earth to accurately determine their distance. When you know brightness you can calculate distances.
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- Type 1a supernovae, another commonly used cosmic yardstick, are exploding stars that flare with the same brightness and are brilliant enough to be seen from relatively longer distances.
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- By measuring about 2,400 Cepheid stars in 19 galaxies and comparing the observed brightness of both types of stars, astronomers accurately measured their true brightness and calculated distances to roughly 300 Type 1a supernovae. They compared those distances with the expansion of space as measured by the stretching of light from receding galaxies. They used these two values to calculate how fast the universe expands with time, or the Hubble constant of expansion.
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- The improved Hubble constant value is 73.2 kilometers per second per megaparsec. (A megaparsec equals 3.26 million light-years.) The new value means the distance between cosmic objects will double in another 9.8 billion years.
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- This refined calibration presents a puzzle because it does not match the expansion rate predicted for the universe from its trajectory seen shortly after the big bang. Measurements of the afterglow from the big bang by NASA's “Wilkinson Microwave Anisotropy Probe” (WMAP) and the European Space Agency's “Planck satellite” mission yield predictions for the Hubble constant that are 5 percent and 9 percent smaller, respectively.
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- If we know the initial amounts of stuff in the universe, such as dark energy and dark matter, and we have the physics correct, then we can go from a measurement at the time shortly after the big bang and use that understanding to predict how fast the universe should be expanding today.
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- There are a few possible explanations for the universe's excessive speed over this calculation. One possibility is that dark energy, already known to be accelerating the universe, may be shoving galaxies away from each other with even greater, or growing, strength.
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- Another idea is that the universe contained a new subatomic particle in its early history that traveled close to the speed of light. Such speedy particles are collectively referred to as "dark radiation" and include previously known particles like neutrinos. More energy from additional dark radiation could be throwing off the best efforts to predict today's expansion rate from its post-big bang trajectory.
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- The boost in acceleration could also mean that dark matter possesses some weird, unexpected characteristics. Dark matter is the backbone of the universe upon which galaxies built themselves up into the large-scale structures seen today.
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- Despite all the advances in theory and observations in particle physics and cosmology we only understand about 5% of the Universe. The remaining matter and energy of the Universe consist of dark matter, which accounts for the rotational speeds of galaxies and formation of cosmic structure, and dark energy which accelerates the expansion of the Universe."
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- The rate of acceleration delivered by astronomical observations and the standard model of cosmology is much smaller than the value presented by the standard model of particle physics. If the discrepancy between different observations is not resolved even after more refined observations, then it will mean that the base model of “Lambda CDM“, the most favored standard model of cosmology, needs to be changed.
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- Failure to resolve this disparity could mean that the way we currently measure cosmological distance using the spectroscopic red-shift and the use of standard candles like Type-1a supernovae or Cepheid variables, stars whose luminosity varies periodically with time, needs to be revised.
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- Unraveling the nature of dark energy by study of the accelerated Universe will unlock the deepest level of our understanding of the Universe. The best way to proceed in the understanding of dark energy is to closely relate theory with observations which are now possible due to a plethora of new precision experiments in cosmology and particle physics. We have much more to learn.
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October 20, 2022 UNIVERSE - expansion rate still a ? 3716
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