---------------------- 2732 - ASTRONOMY - more mysteries uncovered?
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- The weight of the universe, rather the mass of the universe, is a difficult thing to measure. To do it you need to count not just stars and galaxies, but dark matter, diffuse clouds of dust and even wisps of neutral hydrogen in intergalactic space. Astronomers have tried to weigh the universe for more than a century, and they are still finding ways to be more accurate.
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- Knowing the mass of the cosmos is central to understanding its history and evolution. While dark energy drives the universe to expand, matter does the opposite and tries to keep the universe from expanding. Together they form an average density of matter and energy in the universe, known as the cosmic density parameter.
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- One way to measure this parameter is to look at the Cosmic Microwave Background. This remnant glow from the big bang has small variations in temperature. The scale of these fluctuations tells us the rate of cosmic expansion, which in turn lets us know the cosmic matter “density“.
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- Another way to weigh the universe is to look at how the light of distant galaxies is deflected by galaxies. It’s an effect known as “gravitational lensing“. The challenge with this method is determining which light is lensed and which is not. To do that we would need to compare the distorted shape of the galaxy we see with the actual shape of the galaxy, which we don’t know exactly.
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- It’s not possible to make a comparison for a single galaxy, but we can compare them statistically after measuring many different galaxies. Since we know the shape of an average galaxy, we can compare this to the lensed shapes we see to get a statistical measure of how much lensing occurs.
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- While the lensing effect gives you a statistical measure of the amount of mass between us and a distant galaxy, it doesn’t give you the “cosmic density“. For that, you need to know how far away the galaxy is. The greater the distance, the more mass you’d expect between it and us. So the team also determined galactic distances by measuring their redshifts at several wavelengths.
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- The result is a cosmic density parameter that differs slightly from that found from the Cosmic Microwave Background. This is not the first time we’ve seen a strange disagreement in cosmology. In the standard cosmology model, it is assumed that the amount of dark energy in the universe is “constant“. But this latest data fit an alternative model where dark energy changes over time.
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- Not only does a universal constant rate of expansion seem annoyingly inconstant at the outer fringes of the cosmos, it occurs in only one direction, which is weird. Astrophysicists continue to find hints that one of the cosmological constant is not so constant after all.
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- New measurements of light emitted from a quasar 13 billion light years away reaffirm past studies that found tiny variations in the “fine structure constant”. The fine structure constant is a measure the strength of electromagnetism. one of the four fundamental forces in nature (the others are gravity, weak nuclear force and strong nuclear force).
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- The Fine Structure Constant is a dimensionless number and it involves the speed of light, something called Planck's constant and the electron charge, and it's a ratio of those things to measure the strength of the electromagnetic force."
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- The electromagnetic force keeps electrons whizzing around a nucleus in every atom of the universe. Without it, all matter would fly apart. It was believed to be an unchanging force throughout time and space. But over the last two decades anomalies in the fine structure constant ere found where the electromagnetic force measured in one particular direction of the universe seems ever so slightly different.
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- The fine structure constant was different in certain regions of the universe. Not just as a function of time, but actually also in direction in the universe.
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- The most distant quasars that we know of are about 12 to 13 billion light years from Earth. By studying the light in detail from these distant quasars, we can determine the properties of the universe as it was when it was in its infancy, only a billion years old.
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- The universe then was very, very different. No galaxies existed, the early stars had formed but there was certainly not the same population of stars that we see today. And there were no planets.
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- The fine structure constant along the one line of sight to the quasar was different than the constant measured by a different line of sight. This seems to be supporting this idea that there could be a directionality in the universe.
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- So the universe may not be isotropic in its laws of physics, Isotropic means that is the same, statistically, in all directions. But in fact, there could be some direction or preferred direction in the universe where the laws of physics change, but not in the perpendicular direction. In other words, the universe in some sense, has a dipole structure to it.
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- In one particular direction, we can look back 12 billion light years and measure electromagnetism when the universe was very young. Putting all the data together, electromagnetism seems to gradually increase the further we look, while towards the opposite direction, it gradually decreases.
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- In other directions in the cosmos, the fine structure constant remains just that, constant. These new very distant measurements have pushed our observations further than has ever been reached before.
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- The universe suddenly appears to have the equivalent of a north and a south.
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- Another team working completely independently made observations about X-rays that seemed to align with the idea that the universe has some sort of directionality. They found that the properties of the universe in this sense are not isotropic and there's a preferred direction.
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- Electromagnetism may fluctuate in certain areas of the universe to give it a form of directionality.
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- For a long time, it has been thought that the laws of nature appear perfectly tuned to set the conditions for life to flourish. The strength of the electromagnetic force is one of those quantities.
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- If the electromagnetic force were only a few percent different to the value we measure on Earth, the chemical evolution of the universe would be completely different and life may never have got going. Are the fundamental physical quantities like the fine structure constant are 'just right' to favor our existence, applying throughout the entire universe?
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- If there is a directionality in the universe, and if electromagnetism is shown to be very slightly different in certain regions of the cosmos, the most fundamental concepts underpinning much of modern physics will need revision.
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- Our standard model of cosmology is based on an isotropic universe, one that is the same, statistically, in all directions. The model itself is built upon Einstein's theory of gravity, which itself explicitly assumes constancy of the laws of Nature. If such fundamental principles turn out to be only good approximations, the doors are open to some very exciting, new ideas in physics.
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- New technologies are now emerging to provide higher quality data, and new artificial intelligence analysis methods will help to automate measurements and carry them out more rapidly and with greater precision.
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- There is much more to learn. We are searching on the beach picking up pebbles of knowledge with the whole ocean of the unknown that lies on the horizon.
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- May 5, 2020 2732
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--------------------- Tuesday, May 5, 2020 -------------------------
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