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---------------------------- - 2335 - The Universe Almost Didn’t Happen
- By the Universe I mean the “reality” we observe and that we are a part of. We believe that this “reality” is the same everywhere. Physics is the same everywhere. Physics is the same backwards in time.
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- The Universe is expanding today, so, running backwards in time it must have been denser and hotter than it is today. Gravity is constantly trying to pull all the matter back to a Singularity.
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- However, as the Universe continues to expand the pull of gravity is weaker and weaker. It all depends on the relative density of matter in the Universe. A lot of matter will stop the expansion and cause it to contract. Too little matter and the expansion will continue forever. There is a balancing point were the density of matter is just “critical” to slow the expansion to a stop at an infinite point in time. This is called the “ Critical Density”.
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- Mass and Energy are the same thing according to E=mc^2. Energy is mass in kilograms times 90,000,000,000,000,000 meters^2 per seconds^2. So, we really mean the mass-energy density of the Universe.
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- If the pull of gravity and the push of expansion are exactly in balance at the Critical Density, then this is an unstable condition. It is like balancing a pencil upright on its point. The slightest force in any direction will cause the pencil to fall in that direction. If the Universe is exactly in balance then the slightest perturbation will cause it to either contract or expand again.
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- If the mass-energy density is greater than Critical it will stop expanding and begin contracting until the density becomes infinite at a single point ( a Singularity). If the mass-energy density is less than Critical then the Universe will continue expanding causing density to become less and less and colder and colder into the Deep Freeze. All the measurements astronomers are able to make confirm that the actual mass-energy density is almost exactly Critical.
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- Astronomer’s calculations make the density so close to Critical that if you added or subtracted 10% of the mass of a “dime” to the total mass of the Universe conditions would change to make the Universe physically impossible for life.
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- This is called the Universe’s Fine- Tuning Problem. If you run the calculations backwards in time to one second after the Big Bang the density would be extremely high. If you continue calculating back to a billionth or a second, one nanosecond, after the Big Bang you get the density of the entire Universe to be:
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------------------- 447,225,917,218,507,401,284,016 grams per cubic centimeter
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- Adding just 0.2 grams per cubic centimeter to this number and the Universe would have collapsed into a Big Crunch by now, 13.7 billion years after the Big Bang. If you take away only 0.2 grams per cubic centimeter the matter density would be so low by now we could not even detect it. The Fine-Tuning Problem! If any of the constants in physics were slightly different life could not exist.
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- When the Universe is at Critical Density astronomers say the geometry of the Universe is “flat”. The measurements to date tell us the Universe appears to be flat to one part in 10^60.
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- This is a very small number:
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------- 0.000000000000000000000000000000000000000000000000000000000001
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- But, the Universe could not be exactly flat because that would be an unstable condition. It is so close to Critical Density, but not exactly Critical Density. The Fine-Tuning Problem AGAIN!!!
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- Only a flat geometry Universe meets two essential requirements for life. First, a flat Universe survives long enough for generations of stars to form. The elements in the periodic table are formed in supernovae explosions. These elements in chemistry and biology are essential for life to form.
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- Secondly, a flat Universe expands slowly enough for matter to clump into stars, galaxies, planets, moons, asteroids. But, not so slowly that only Blackholes and Neutron Stars are formed.
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- Because the Universe is flat to one part in 10^60, astronomers must conclude that the matter we see is only 4% of the mass-energy of the Universe. 23% must be Dark Matter and 73% must be Dark Energy. We do not know what 96% of the Universe is but it must the there because we are here.
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- One explanation for the flat Universe is the “Theory of Inflation”. Between 10^-34 and 10^-32 seconds after the Big Bang, when the force of gravity split off from the other three forces, the Universe expanded be a factor of 10^50, expanding from 10^-50 meters to 1 meter in size.
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- This faster than the speed of light expansion explains why the Observerable Universe is homogenous and isotropic. It also explains why it appears flat. Just like the Earth appears flat in the part we observe from 2 meters off the ground. The more we see the more we learn. The more we learn the more we can see.
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- April 18, 2019. 1050
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--------------------- Tuesday, March 24, 2020 -------------------------
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