Wednesday, March 8, 2023

3907 - Einstein Ionized the Universe?

 

-   3907  -  Einstein Ionized the Universe?   The James Webb Space Telescope can’t study the radiation coming out of the galaxies directly, because that radiation gets absorbed by the billions of light-years worth of matter between us and those galaxies. So instead they had to look for other clues.


------------  3907  -   Einstein Ionized the Universe?

-    Billions of years ago our universe was a lot smaller and a lot hotter than it is today. At very early times it was so small and hot that it was in the state of a “plasma”, where electrons were separated from atomic nuclei.

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-    But when the universe was roughly 380,000 years old, it cooled to the point that electrons could recombine onto their nuclei, forming a soup of neutral atoms.

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-   Observations of the present-day universe reveal that almost all the matter in the universe is not neutral at all. Instead it’s “ionized”, once again in the state of a plasma. Something had to happen in the intervening billions of years to transform the neutral gas of the cosmos into an ionized plasma.

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-    Astronomers call this event the “Epoch of Reionization” and suspect that it happened within the first few hundred million years after the Big Bang. But they are not sure how this transformational event proceeded.

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-    One of the great debates in modern cosmology is the source of this “reionization”. One hypothesis is that quasars are responsible. Quasars are the ultra bright cores surrounding supermassive black holes which pump out enormous amounts of high energy radiation.

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-    This radiation could easily flood the universe and transform it from neutral to ionized. But the problem with this hypothesis is that quasars are relatively rare, and so they have difficulty covering the volume of the universe.

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-    Another hypothesis is that young galaxies rich with star formation are responsible. In this scenario the process of ionizing the neutral gas is more spread out throughout the universe.

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-    Each individual galaxy is only capable of ionizing the gas in its nearby vicinity, but since there are so many galaxies it’s possible to reionization the entire universe.   But the only way to do this is if enough high energy radiation leaks out of galaxies and into the surrounding medium.

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-     Using the James Webb’s ability to study distant galaxies, they were able to measure how compact the galaxies were, and how rich in star formation they were. They were then able to compare these galaxies to similar galaxies found in the present day universe to create an estimate of the amount of radiation leaking from them.

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-    They estimate that on average the galaxies in the early universe leaked roughly 12% of their available high energy photons. This is just enough to potentially reionization the entire cosmos in a relatively short amount of time.

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-   Einstein's theory of special relativity changed the way we think about space and time and established a universal speed limit of the speed of light. One of Einstein's earliest achievements, at the age of 26, was his theory of “special relativity”, so-called because it deals with relative motion in the special case where gravitational forces are neglected.

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-   It was one of the greatest scientific revolutions in history, completely changing the way physicists think about space and time.

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-    In effect, Einstein merged these into a “single space-time continuum”. One reason we think of space and time as being completely separate is because we measure them in different units, such as miles and seconds. But Einstein showed how they are actually interchangeable, linked to each other through the speed of light, 186,000 miles per second.  E-mc^2

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-   Perhaps the most famous consequence of special relativity is that nothing can travel faster than light. But it also means that things start to behave very oddly as the speed of light is approached. If you could see a spaceship that was traveling at 80% the speed of light, it would look 40% shorter than when it appeared at rest.

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-    And if you could see inside, everything would appear to move in slow motion, with a clock taking 100 seconds to tick through a minute. This means the spaceship's crew would actually age more slowly the faster they are traveling.

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-    An unexpected offshoot of special relativity was Einstein's celebrated equation E = mc^2.  The equation expresses the equivalence of mass (m) and energy (E), two physical parameters previously believed to be completely separate.

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-    In traditional physics, mass measures the amount of matter contained in an object, whereas energy is a property the object has by virtue of its motion and the forces acting on it. Additionally, energy can exist in the complete absence of matter, for example in light or radio waves.

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-     However, Einstein's equation says that mass and energy are essentially the same thing, as long as you multiply the mass by c^2, the square of the speed of light, which is a very big number to, (670,633,500 mile per hour squared),  ensure it ends up in the same units as energy.

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-    This means that an object gains mass as it moves faster, simply because it's gaining energy. It also means that even an inert, stationary object has a huge amount of energy locked up inside it.   If sufficiently energetic particles are smashed together, the energy of the collision can create new matter in the form of additional particles.

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-    Lasers are an essential component of modern technology and are used in everything from barcode readers and laser pointers to holograms and fiber-optic communication. Although lasers are not commonly associated with Einstein, it was ultimately his work that made them possible.

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-   The word laser, coined in 1959, stands for "light amplification by stimulated emission of radiation" and stimulated emission is a concept Einstein developed more than 40 years earlier.

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-    In 1917, Einstein wrote a paper on the quantum theory of radiation that described, among other things, how a photon of light passing through a substance could stimulate the emission of further photons.

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-     Einstein realized that the new photons travel in the same direction, and with the same frequency and phase, as the original photon.  This results in a cascade effect as more and more virtually identical photons are produced.

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-   In 1935 Einstein and Nathan Rosen described the possibility of shortcuts from one point in space-time to another, known as Einstein-Rosen bridges. Einstein's theory of special relativity showed that space-time can do some pretty weird things even in the absence of gravitational fields.

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-      Einstein discovered when he finally succeeded in adding gravity into the mix, in his theory of general relativity. He found that massive objects like planets and stars actually distort the fabric of space-time, and it's this distortion that produces the effects we perceive as gravity.

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-    Einstein explained general relativity through a complex set of equations, which have an enormous range of applications. Perhaps the most famous solution to Einstein's equations came from Karl Schwarzschild's solution in 1916, a black hole.

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-   Even weirder is a solution that Einstein himself developed in 1935 in collaboration with Nathan Rosen, describing the possibility of shortcuts from one point in space-time to another. Originally dubbed Einstein-Rosen bridges, these are now known to all fans of science fiction by the more familiar name of “wormholes”.

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-     In 1929, Edwin Hubble's observations of other galaxies showed that the universe really is expanding, apparently in just the way that Einstein's original equations predicted. It looked like the end of the line for the “cosmological constant”, which Einstein later described as his biggest blunder.

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-   That wasn't the end of the story, however. Based on more refined measurements of the expansion of the universe, we now know that it's speeding up, rather than slowing down as it ought to in the absence of a cosmological constant. So it looks as though Einstein's "blunder" wasn't such an error after all.

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-   In February 2016, with the announcement of the discovery of gravitational waves was yet another consequence of general relativity. Gravitational waves are tiny ripples that propagate through the fabric of space-time, and it's often bluntly stated that Einstein "predicted" their existence.

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-    The Laser Interferometer Gravitational-Wave Observatories (LIGO) in Hanford, Washington, and Livingston, Louisiana. As well as being another triumph for Einstein's theory of general relativity, the discovery of gravitational waves has given astronomers a new tool for observing the universe, including rare events like merging black holes.

-  The more we learn the more we find there is still more that is unknown.

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                   March 8, 2023   3907  -   Einstein Ionized the Universe?               3907                                                                                                                         

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