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------------------ 2768 - DARK MATTER - What is the Universe Made of?
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- In August 2006 astronomers found the first direct evidence that Dark Matter really existed. Studies of the Bullet Cluster of galaxies, two galaxies that have been colliding head-on in the Constellation Carina.
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- The studies showed that when galaxies collide all matter inside them does not behave the same way. Stars represent only 1 to 2% of the material and they are spread out so thinly that they pass by each other with almost no collisions and only a very small slow down in velocity due to gravity.
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- However, the hot interstellar gas represents 5 to 15% of the total mass. It is electrically charged ions, referred to as ionized plasma, are significantly affected by the electromagnetic forces and significantly slows down in velocity. As the galaxies pass through each other the stars and the interstellar gas get separated with mass of the stars leading the gas in the shape of a Bullet.
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- Astronomers then used gravitational lensing to measure the affects of gravity on light beams that are coming from distant stars behind the galaxies. Gravity bends light and as the light beams pass the mass of the two galaxies the stars appear to shift position.
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- The amount of shift and the outline of shifting light beams tell astronomers how big the mass is and where it is located. The conclusion was strong evidence that the mass was much greater than what could be seen. And, the position of the mass was around the stars, the ordinary matter. It was Dark Matter.
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- The unseen mass was not around the ionized gas so it was not affected by electromagnetic forces in the same way the gas was. In other words the gravity detected was greater around the 1 to 2% mass of stars than around the 5 to 15% mass of gas. The stars must have had some help that we can not see.
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- The collision occurred 150,000,000 years ago. Much of the astronomy was done with X-ray telescopes because the shockwave from the gas collisions created temperatures of 70,000,000 C plowing through gas at 100,000,000 C with velocities of 6,000,000 miles per hour. These high temperatures emitted X-rays and gave astronomers a good picture of the ionized gas.
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- Since 1970 astronomers have believed Dark Matter existed because studying the orbits of galaxies and stars around galaxies could not be calculated based on the stars and matter they could see. Either Kepler’s and Newton’s formulas for the laws of gravity and motion were incorrect, or there was matter there that they could not find.
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- The rotational velocities of stars around galaxies are nearly constant from stars near the center of rotation to stars near the edge of rotation. At least, the edge that we can see. All of the formulas require the near in stars to be traveling faster than the far out stars.
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- Just like the planets orbiting the Sun. Mercury is traveling much faster than Pluto. If Pluto was traveling as fast as Mercury it would fly out of the Solar System. The same with galaxies. If there was not some unseen mass the galaxies would fly apart. The only way to make the formulas work is to believe there is an unseen mass surrounding galaxies in a giant halo. The unseen mass is called Dark Matter.
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- How much Dark Matter is there? Astronomers are just now answering this question with all the evidence pointing to Dark Matter representing 85% of all the matter in the Universe. Here is what they get adding up all the mass and energy in the Observable Universe:
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----------------- Heavy elements, heavier than helium ----------- 0.03%
----------------- Neutrinos ------------------------------------------- 0.30%
----------------- Stars, mostly hydrogen and helium ------------- 0.40%
----------------- Free hydrogen and helium gas ------------------- 3.50%
----------------- Dark Matter ---------------------------------------- 23%
----------------- Dark Energy --------------------------------------- 73%
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-The Big Bang basically only created hydrogen and helium. 25% hydrogen and 75% helium. This comes from the fact that the hydrogen nucleus is one proton and there are four protons in the helium nucleus. But, it must have created a lot more because hydrogen and helium are only about 4% of the Universe.
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- All the elements heavier the hydrogen and helium, and there are 116 elements, were created in the nuclear reactions of the cores of stars, or in the supernova explosions that occur when the cores run out of fuel, the star implodes, and rebounds into a giant explosion called a supernova.
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- The shockwave from the explosion slams into incoming gas and interstellar gas creating more nuclear reactions and heavier elements. These are all the elements that make up us and everything we see around us. All these elements are less than 0.03% of what makes up the Universe.
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- All the stars in all the galaxies only make up 9% of ordinary matter.
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- Ordinary matter itself only make up 16% of all the matter. 84% of all the matter is Dark Matter. It is that 84% of the mass of the Bullet Cluster galaxy collision that the astronomers detected in gravitational lensing.
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- If we assume that Dark Matter and Dark Energy are made up of particles like the rest of the Universe, how many particles make up the Universe?
-------------- Matter, that is protons and electrons -------- 10^78 particles --- 17%
-------------- Radiation, that is photons --------------------- 10^87 photons --- 19%
-------------- Neutrinos ---------------------------------------- 10^87 neutrinos --- 19%
-------------- Dark Matter ------------------------------------ 10^77 particles ---- 17%
-------------- Dark Energy ----------------------------------- 10^118 particles --- 26%
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------------------TOTAL ----------------------------------------10^447 particles --- 100%
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- If Dark Matter and Dark Energy are particles they represent 43% of all particles.
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- Photons and neutrinos are massless and nearly massless and they represent 38% of all particles.
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- Protons and electrons must be of equal numbers because the Universe has a neutral electric charge, so protons = 10^78 particles and electrons = 10^78 particles, but an electron is only 1/1860th the mass of a proton.
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- Absence of evidence is not evidence of absence. Now we have evidence of presence, but we have little knowledge of what the presence is. Dark Matter is most likely a sub-atomic particle that we have yet to discover. It is most likely a very heavy particle or it would have shown up in our particle accelerator experiments. -
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- Dark Energy was not known until 1998 so we have only 30 years to think about it. The most likely answer is vacuum energy. A vacuum is not really a vacuum but a see of virtual particles and anti-particles going into and out of existence in such a short time they do not defy the laws of physics and cannot be detected using the laws of physics. The hope is that higher energy particle accelerators may discover some of the answers.
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- It is interesting that astronomy with the theory of Relativity studying the biggest things in the Universe, now depends on the particle physicists with the theory of Quantum Mechanics studying the smallest things in the Universe.
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- Mathematicians have the other big problem of bringing Relativity and Quantum Mechanics together. Neither math will work in the others scale. The new mysteries in the Dark are bringing everyone together to solve the same problem. What is the Universe made of? We are still trying to figure that out?
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- June 27, 2020 827 2768
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--------------------- Sunday, June 28, 2020 -------------------------
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