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----------------- 1775 - Cosmic Evolution.
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- The “ Universe” 100 years ago was a few million visible stars in our Milky Way Galaxy. It was simple, unchanging, and consistently static.
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- My how times change. Today the Observable Universe is inhabited by 100 billion galaxies , and , each galaxy could contain 100 billion stars, and, probably 100 billion planets as well.
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- Somehow galaxies are configured in a super structure controlled by mysterious Dark Matter. The space between these web like structures continues to expand and consequentially the galaxies are moving further and further apart. The energy driving this expansion is another mystery, called Dark Energy.
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- Over the last 13.7 billion years we have grown from a plasma of Quark soup to the complexity of galaxies and life itself. Light from when the Universe was only a few hundred million years old has traveled 13.7 billion lightyears to reach us. Traveling through expanding space the light wavelengths have stretched by a factor of 10 to microwave wavelengths. To see this early light astronomers must us infrared and radio detectors as their telescopes.
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- At 100 million years galaxies first formed using 5 parts Dark Matter and 1 part hydrogen and helium, ( ordinary matter). Dark Matter did not emit or absorb light radiation. Hydrogen and helium did emit light and this caused them to loose energy. This in turn allowed early ordinary matter to concentrate in the center of clouds of Dark Matter that didn’t loose energy. This phenomena formed the web of filaments and clusters of galaxies we see today.
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- The early stars were massive, 100’s of Solar Mass. They burned hot and with intense ultraviolet light. They had short lives, exploding as supernovae after only 100 million years. It took the next billion years for gravity to assemble the first galaxies out of the next generation stars.
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- For the first 100,000 years the Universe was dominated by pure radiation. The first elements fused in the nucleosynthesis era was limited to the lightest elements, 75% hydrogen and 25% helium. We had to wait 1 billion years before the heavier elements were fused in the exploding supernovae of second generation stars. The following generations of exploding supernovae is what formed the elements in the Periodic Table.
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- The identity of Dark Matter remains unclear but cosmologists are convinced its existence emerged from the Quark soup when ordinary matter emerged.
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- One possible candidate for Dark Matter is called the “ neutralino”. Like neutrinos however with masses 100 to 1,000 times greater than a proton mass. The Large Hadron Collider at CERN, Switzerland, is today searching for this heavy particle.
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- A second candidate is called the “ axion”. It is believed that a strong magnetic field can transform an axion into a photon. These particles would have a mass one trillionth that of an electron.
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- Physics tells us that the early Universe must have contained equal amounts of matter and anti-matter. Somehow out of the Quark soup we got one extra Quark for every billion anti-Quarks. The rest were annihilated in a burst of radiation. This slight imbalance occurred only 10^-34 seconds after the Big Bang.
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- Quantum fluctuations on the sub-atomic scale got blown up to astrophysical size by Cosmic Inflation. These were the seeds for all the Cosmic structure we see today. What we see are made up of protons, neutrons, and electrons. What we see is all matter and almost no anti-matter. What we see is only 4.5% of the mass-energy of the total Universe.
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- There is irony in the arrogance implied in our figuring this stuff out. At the same time it gives us the humility that there is so much more to the Universe than us.
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- If the Universe continues its accelerated expansion at the current rate than all traces of the Big Bang will disappear in 30 billion years. We will go back to what astronomers knew 100 years ago when instruments were not powerful enough to reveal the Universe we know today. All other galaxies would have been carried by Cosmic Acceleration out of our ability to see them. The temperature of the CMB radiation would be too low to even measure. All evidence of the Big Bang would have disappeared.
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- A new telescope will measure the expansion of the Universe with more accuracy. Called DESI, Dark Energy Spectroscopic Instrument.
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- DESI will allow us to make a 3-D map of galaxy locations. It will measure the Redshifts of 25 million galaxies to add depth information to our 2-D image. If the light from the galaxy starts out with a wavelength of 373 nanometers and we see it Redshifted to 746 nanometers we know the Universe stretched by a factor of 2 in that region of space during the time the light was making its way to us.
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- By knowing the distances between pairs of galaxies astronomers can track the expansion of the Universe. They can calculate the gravitational fields between galaxies. They can check to see if our current theory of gravity works the same in both the early Universe and today. Maybe Cosmic expansion comes and goes in a Cosmic oscillation. Stay tuned there is much more to learn about Cosmic Evolution. And, how we got here, from there.
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----- 707-536-3272 ---------------------- Tuesday, May 12, 2015 -----
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