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---------------------- 2263 - The Universe as We Know It.
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- The Universe is everything that exists. If something “exists“, it exists in space and in time. “Everything” is all forms of matter and energy that occupy space and time But, energy and matter are the same thing according to Einstein’s E = mc^2. Energy and matter are the same thing separated by the constant c^2, which is 90,000,000,000,000,000 meters^2 per second^2. E = 90*10^15 * m .
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- The Universe is and has always been everything, but, today it has bigger volume than it had yesterday. And, every day it gets bigger! Everything is constantly being spread over a wider volume, density is getting smaller. Tomorrow it will be bigger than it was today and today it is bigger than it was yesterday.
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- Today the Universe is at least 93 billion lightyears in diameter, at least. At the same time it is only 13.73 + or - 0.12 billion years old. How can the Universe be bigger than the speed of light? Has the Universe grown faster than the speed of light? Yes, it has.
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- If the Universe is older and bigger today, it must have been younger and smaller in the past. Tomorrow it will be bigger and older still. If the Universe is 13.75 lightyears old why is the Universe not 27.5 lightyears in diameter? How can it be 93 billion lightyears in diameter? Run time backwards and the Universe must have had a beginning. We call that beginning the Big Bang.
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- The Big Bang started from an immense density of all the energy in the Universe concentrated in a single point, a singularity. A small, dense, very hot spot of spacetime and energy. For some reason the space began to expand and time began to run in the forward direction.
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- Energy began to disperse and the Universe began to cool. Today it is
-455 degrees Fahrenheit, which is very cool (2.73 Kelvin). Space somehow expanded faster than the speed of light and that is how two galaxies 13 billion years old can be 93 billion lightyears apart.
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- The Universe may have been bigger than the singularity, we don‘t know. The singularity today is only the Observable Universe. There is more of the Universe that is Unobservable.
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- We believe the same laws of physics have been constant throughout this expansion. We are still trying to discover more of the laws of physics. There is much about the Universe we do not see and do not understand. What is worse is that due to the accelerating expansion we are seeing less and less all the time.
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- Gravity is the attractive force that stretches across the entire Universe. It is pulling everything back together. The force of gravity affects all energy and matter and it should be slowing the expansion down. But, it is not. The expansion is speeding up. There must be a repulsive force that we do not understand that is overcoming the force of gravity. We call it, for lack of a better name, Dark Energy.
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- Quantum Mechanics throws in another wrinkle on the Universe. We said the Universe is everything that exists. It is also every thing that does not exist. Quantum Mechanics describes reality as one possible outcome of an event. However, all possible outcomes are considered and therefore exist before the single outcome collapses into reality.
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- Reality is defined in this case as all matter-energy that exists in spacetime and follows the laws of physics.
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- The average density of the Universe today amounts to a single hydrogen atom in every 4 cubic meters of volume. In other words the Universe is mostly empty space. Or, at least space that we think is empty. This density is ordinary matter, or atoms. It only represents 4.6 % of the Universe. 23.3 % is Dark Matter and 72.1 % is Dark Energy.
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- The Universe appears to have no net electric charge. So electromagnetic force is neutralized and gravity is the dominant force. The Universe appears to have no angular momentum, it is not rotating. It appears to be a smooth spacetime continuum with zero curvature, or nearly flat.
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- The Universe of ordinary matter is dominated by matter and not antimatter. This defies the laws of Conservation since physics expects there to be equal amounts of matter and antimatter. Somehow the Universe we know prefers matter.
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- This matter is made of fundamental particles called leptons, quarks, photons, gluons, bosons, and gravitons. There are three generations of each of these particles. Each generation occupying higher energies. The lowest energy generation is the one that is stable and the one we live in, electrons, protons, photons and neutrinos.
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- There are three fundamental forces that affect these particles. The electroweak force, the strong nuclear force, and gravity. Again, the electric and magnetic forces are neutral, the weak and strong nuclear forces only operated over the diameter of the atom, so the force of gravity is the dominant, singularly attractive force. Except Dark Energy may be more dominant today. The Higgs boson was just recently discovered and the graviton fundamental particles have not yet been discovered . And, Dark Energy has not been discovered either. Evidence and theory tells us they exist.
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- The Cosmic Microwave Background radiation has been the most significant evidence in the past five years. This energy started out 380,000 years after the Big Bang as high energy Gamma Rays ( high frequency, small wavelength, hot temperature). The Universe has expanded by 1000 times since then.
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- This expansion has redshifted these photons making them less energy microwaves, (lower frequency, longer wavelength, and cooler temperature). The CMB was first released 380,000 years after the Big Bang because at that point the Universe had expanded and cooled enough for neutral atoms to form out of the electrons and nuclear ions, protons.
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- When this plasma became neutral the electromagnetic radiation, the photons, could escape the opaque cloud. The CMB sees this opaque cloud after 13 billion years of expansion. It has cooled to 2.725 Kelvin, but it is not perfectly smooth. There are hotter and colder spots that are + or - 0.0002 Kelvin. They represent denser and less dense volumes of space that today have come the galaxies and voids in space. The size of these spots is what tells us the Universe’s shape is flat.
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- We are talking about the Observable Universe here. It is something finite that we can study. The Total Universe may be infinite, we just do not know. We can only see 13.7 billion light years because that is as far as light has traveled. It is the edge of the Observable Universe.
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- The actual Universe may have no edge. We know the edge is further away than we can see because during the time the light has traveled here space has been expanding. The edge is at least 93 billion lightyears in diameter. We can not see that far but it is out there. With the expansion accelerating the light at the edge will never reach us. Space is expanding faster than the photons are traveling. In that sense Our Observable Universe is shrinking.
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- In this situation distances become very difficult to measure. We have the distance of separation of two bodies at the time the light was given off. (smaller distance). We have the distance light has traveled to reach us (medium distance). And, we have the distance of separation “now” considering space has grown during the time light has been traveling. (farther distance).
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- The word “now” has a different meaning. Now when we see a supernova explosion 12 billion lightyears away the explosion actually happened a long, long time ago. Before the Earth was even born.
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- The next problem with distances in the Universe is that we assume that light travels in a straight line. It doesn’t. Light gets bent by intervening gravitational forces as it travels throughout the Universe. If the light from the supernova explosion traveled by a cluster of galaxies on its way to us, some of the light would be bent. It is called gravitational lensing and it has the same effect as a giant magnifying glass. It is possible to see the supernova explosion from the light that traveled straight through and see it again month’s later from the light that was bent around the cluster.
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- Then there is the problem with an infinite Universe. Infinity is just too big to get your mind around. If something is truly infinite then everything that is possible to exist, does or will exist. Somewhere. Sometime. In fact, everything would occur an infinite number of times. No matter how small the probability of something happening it will eventually happen.
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- Then there is the shape of the Universe even if we say it is finite. If the shape is spherical, and it is a closed system you should be able to look in one direction far enough and see the back of your own head.
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- Recent evidence in astronomy is that the shape of the Observable Universe is flat, or nearly flat. Flat means that if you shoot parallel laser beams no matter how far they go they will stay parallel. Perpendicular lines will stay perpendicular.
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- But, that does not mean necessarily that flat is like a sheet of paper. To follow this definition of parallel lines a donut shape is flat. The Universe could be the shape of a donut and appear flat to us. It could be spherical and big enough that the part we see appears flat.
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- The best test is a triangle. If an equilateral triangle in space has 60 degree angles and totals 180 degrees than the space is flat. If the total is more than 180 degrees than it is spherical, like the surface of Earth. If it totals less than 180 degrees than it is saddle shaped and not a closed system.
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- Then there is Inflation of the Universe. Shortly after the Big Bang the Total Universe grew by at least 100 times bigger than the Observable Universe in an instant of time. So if the Observable Universe is 93 billion lightyears across, the Total Universe must be, at least, 9,300 lightyears across.
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- Of course, we can not see, nor never will see, the Total Universe. Our field of view is limited. But, it is studying the changes of our field of view with distance that will tell us the shape of the Universe. If you have a cluster of galaxies in view. Those galaxies are younger the farther away they are. If you see more and smaller galaxies the field of view is saddle shaped. If your view includes fewer and bigger galaxies than they actually are then the view is spherical shaped. Of course you have to know how big the galaxies really are to know what our field of view is telling us. It is not just the size but the distances that are hard to measure.
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- The way the Cosmic Microwave Background measurement tells us is the variation of the hot and cold spots that appear across the sky. Remember these hot and cold spots are only 0.0002 degrees from 2.725 Kelvin. And, the hot spots are denser volumes of energy and matter that eventually condensed into the galaxies and stars.
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- But, to be the sizes they are today that had to be a certain size when they started at Universe age of 380,000 years, 13,730,000,000 years ago. The angle of our field of view of the spots would put them at ½ angular degree across the sky if the shape were a saddle. They would be 1½ degree if it were spherical. And, 1 degree, which it is, telling us it is flat.
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- To have grown and remain flat the Universe must be filled with the exact critical density. If it were a little more dense gravity would pull us back into a Big Crunch. If it were a little less dense Dark Energy would expand us into a Big Freeze.
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- Another reason astronomers like a flat Universe is that the math is easier. Non-Euclidian math is just too hard to do. The Universe is hard enough to figure out without making the math difficult. If we could go as far as forever where would we get to? The best rule is to live like you will die tomorrow, and dream like you will live forever.
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Footnote: 380,000 years after the Big Bang, 13.73 billion years ago, neutrinos were 10% of the Universe, atoms were 12%, Dark Matter 63%, photons were 15%, and Dark Energy was negligible. The Universe continues to expand, become cooler, and less dense.
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- Gravity needs density to be strong. Dark Energy is the same regardless. Today 1% of the Universe is neutrinos, 4.6% is atoms (which is everything in our world) 23.3% is Dark Matter ( which is something we have not identified yet), and 72.1% is Dark Energy (which is something we have not identified yet but whatever it is it now dominates.)
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- The Universe is expanding into the Big Freeze. The Observable Universe is getting smaller and we can see less and less.
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- February 8, 2019 898
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-------------------------- Friday, February 8, 2019 --------------------------
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