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--------------------- 2412 - UNIVERSE - comprehending an expanding universe
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- At my age I don’t even buy green bananas. So how am I supposed to comprehend a Universe that is 13,800,000,000 years old. This was when we believe the universe began. This moment, known as the Big Bang, is when space itself rapidly began expanding.
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- At the time of the Big Bang, the observable universe with its over 2 trillion galaxies fit into a space less than a centimeter across. Today the observable universe is 93,000,000,000 light-years across and still expanding.
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- Our observable universe was very small when man first started picking bananas from the trees. Our vision was very limited. For thousands of years the origins of the universe were shrouded entirely in myth and mysteries.
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- But , things changed in 1929. In that year an enterprising astronomer named Edwin Hubble discovered something very important about the universe. The whole thing is expanding.
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- Edwin Hubble made his discovery by measuring something called redshift, which is the shift toward longer, red wavelengths of light when it has traveled from very distant galaxies that are expanding away from us. The farther away the galaxy, the more pronounced the stretching of the light’s wavelength towards the red end of the light spectrum. We call it a redshift.
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- Hubble found that redshift increased linearly with distance in far-off galaxies, indicating that the universe is not stationary. It's expanding, everywhere, all at once.
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- Hubble was able to calculate the rate of this expansion, a figure known as the “Hubble Constant“. It was this discovery that allowed scientists to extrapolate back and theorize that the universe was once packed into a tiny point. They called the first moment of its expansion the “Big Bang“.
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- Current calculations have the universe expanding at 49,300 miles per hour for every light year of distance. This would mean that galaxies at the edge of the Observable Universe are traveling at faster than the speed of light. Their light will never reach us.
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- In May 1964, researchers at Bell Telephone Laboratories, were working on building a new radio receiver in New Jersey. Their antenna kept picking up a strange buzzing that seemed to come from everywhere, all the time. They thought it might be pigeons in the equipment, but removing the nests did nothing. Neither did their other attempts to reduce interference. Finally, they realized they were picking up something real in light energy.
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- What they had detected was the first light of the universe, the cosmic microwave background radiation. This radiation dates back to about 380,000 years after the Big Bang, when the universe finally cooled enough for light photons to travel freely.
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- This discovery lent support to the Big Bang theory and to the notion that the universe expanded faster than the speed of light in its first instant. This is because the cosmic background is quite uniform, suggesting a smooth expansion of everything at once from a small point.
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- The discovery of the cosmic microwave background opened a window into the origins of the universe. In 1989, NASA launched a satellite called the Cosmic Background Explorer (COBE), which measured these tiny variations in this background radiation.
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- The result was a picture of the early universe which showed some of the first density variations in the expanding universe. These miniscule variations gave rise to the pattern of galaxies and empty space, known as the cosmic web of galaxies, that we see in the universe today.
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- In 2016, physicists announced that they had detected a particular kind of polarization, or directionality, in this cosmic microwave background. This polarization is known as "B-modes." The B-mode polarization was the first-ever direct evidence of gravitational waves emanating from the Big Bang.
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- Gravitational waves are created when massive objects in space speed up or slow down. The first that were discovered came from the collision of two black holes. The B-modes provide a new way to directly probe the early universe's expansion.
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- Another consequence of the gravitational-wave discovery was that it allowed scientists to search for additional dimensions, beyond the usual three. According to theorists, gravitational waves should be able to cross into unknown dimensions, if those dimensions exist. A test came in 2017.
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- In October 2017, scientists detected gravitational waves from another collision of two neutron stars. They measured the time it took the waves to travel from the stars to Earth, and found no evidence of any extra-dimensional leakage.
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- The results published last year in July 2018 suggest that if there are any other dimensions out there, they're tiny, affecting areas of the universe less than 1 mile in size. That means that string theory, which posits that the universe is made of tiny vibrating strings and predicts at least 10 of the smallest dimensions, could still be true.
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- One of the strangest discoveries in physics is that the universe is not only expanding, it's expanding at an accelerating rate. This discovery dates back to 1998, when physicists announced the results of several long-running projects that measured particularly heavy supernovas called Type Ia supernovas.
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- The results revealed weaker-than-expected light from the most distant of these supernovas. This weak light showed that space itself is expanding. Everything in the universe is gradually getting farther away from everything else.
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- Scientists call the driver of this expansion "dark energy," a mysterious force that could make up about 68% of the energy in the universe. This dark energy seems to be crucial to making theories of the beginning of the universe fit observations that are being conducted by the Wilkinson Microwave Anisotropy Probe (WMAP), an instrument that has produced the most precise map of the cosmic microwave background to date.
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- Results from the Hubble Telescope, released in April 2019, have deepened the puzzle of the expanding universe. The measurements from the space telescope show that the universe's expansion is 9% faster than expected from previous observations. For galaxies, every 3.3 million light-years' distance from Earth translates to an additional 46 miles per second faster than earlier calculations predicted.
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- Why does this matter for the origins of the universe?
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- Because physicists must be missing something. There may have been three separate dark energy "bursts" during the Big Bang and shortly thereafter. Those bursts set the stage for what we see today.
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- The first might have started the initial expansion; a second may have happened much faster, causing the universe to expand faster than previously believed. A final dark energy burst may explain the accelerating expansion of the universe today.
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- None of this is proven. But, scientists are looking. Researchers are using a newly upgraded instrument, the Hobby-Eberly Telescope, to look for dark energy directly.
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- This project (HETDEX) is measuring the faint light from galaxies as far away as 11 billion light-years, which will allow researchers to see any changes in the universe's acceleration over time.
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- They will also be studying the echoes of disturbances in the 400,000-year-old universe, created in the dense soup of particles that made up everything right after the Big Bang. This too will reveal the mysteries of expansion and explain the dark energy that drove it.
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- The more we learn the more there is to learn. Expanding knowledge of an expanding universe.
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- July 8, 2019
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--------------------- Monday, July 8, 2019 --------------------
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