- 3095 - DARK ENERGY - into WIMPs and MACHOs? The more we learn the more we know the less we know. That is certaintly true with astronomy. We have come to the most recent conclusion that 95% of the Universe is “dark”. We call it Dark Energy and Dark Matter. Of course Matter is Energy too, according to energy = mass*c^2 .
------------------- 3095 - DARK ENERGY - into WIMPs and MACHOs
- Energy can not be created or destroyed. It can just be changed from one form of energy into another form of energy. The most amazing thing I can think of is that if we add up all the forms of energy in the Universe the total energy is zero. That is right, zero. To put it another way, the entire Universe was created out of “nothing“.
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- Drop an apple to the floor. The apple starts out in your hand with some gravitational potential energy dependent on the size of the apple and the height above the floor.
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----------- Potential Energy = mass * acceleration of gravity * height.
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- The acceleration of gravity at the surface of the Earth is a constant, 9.8 feet per second per second, or 22 miles per hour per second, “g“.
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----------- Force = mass * acceleration
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----------- Potential Energy = Force of gravity * height.
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----------- Energy = Force acting over a distance, in this case the height, “h“.
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----------- P.E. = m*g*h
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- When the apple is released it begins to accelerate at the 9.8 feet per second per second. The apple keeps gaining velocity with the maximum velocity occurring just before it hit’s the floor. The Potential Energy of gravity keeps decreasing as it falls , and, the Kinetic Energy of motion keeps increasing as it speeds up.
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---------- Kinetic Energy = ½ mass * velocity^2
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---------- Momentum = mass * velocity
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---------- Kinetic Energy = momentum * velocity
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---------- K.E. = ½ m *v * v
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- When the apple hit’s the floor it stops, momentum and velocity = zero,
Kinetic Energy = zero. The apple gets crushed and bruised. All of the Kinetic Energy of motion has been converted into Thermal Energy that has bruised the apple and heated the floor.
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- Now, if you add up all of these energies they total to zero. Energy changed but none of it was lost. Yes gravity potential energy lost energy, but heat gained energy. The total was zero. The Kinetic Energy may have slowed down due to air resistance, but, again the air heated up to get a net zero.
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- Your body is held together by very strong electromagnetic energy. There are extreme forces between positive and negative charges that make up every atom in your body. However, the some total of all these forces is zero. You are electrically neutral (usually).
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- The same is true with the entire Universe. If you add up all the electric charges and all the magnetic forces they all cancel out and the net effect is Universal neutral.
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- Remember Energy is a force acting over a distance. And, if you add up all the forces including gravity the net is zero. The Universe we understand today all came from nothing.
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- A “quantum fluctuation” started the whole process of the Universe’s expansion. As it expanded it cooled and the individual forces “froze” out. First Gravity froze out as an individual force, then the Strong Nuclear force, then the Weak Nuclear force, then the Electromagnetic force.
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- The same thing happened with matter, as the expansion occurred and the temperature cooled ,matter and anti-matter froze out. All of these are different manifestations of the energy of expansion. If we combined them all back together again they would disappear into nothing. Everything would cancel out.
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- The quantum fluctuations continued during the expansion and some tiny areas became more dense than adjacent tiny areas. Gravity was able to clump the more dense areas into bigger clumps. Voids were created in the less dense areas.
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- As these continued a web of gravity clumps got bigger and bigger until the first stars lit up with nuclear fusion. The first stars lit up after about 300,000,000 years of this expansion after that first quantum fluctuation.
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- When we look at the “Cosmic Microwave Background radiation” which dates back to 380,000 years after the Big Bang we can see the results of these fluctuations which by then had expanded to 1 degree of arc in the sky.
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- Extrapolating these fluctuations to today with 1000 times greater expansion in the Universe we can see the galaxies and clusters of galaxies that were created. At the same time distances expanded by a factor of 1000 temperature cooled by a factor of 1000 from 3,000 Kelvin then to 3 Kelvin today.
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- The rate of the expansion of the Universe depended on a balance with gravity that in turn was a balance in the density of matter. The math that supports this balance occurs when the density of the Universe is today 27% matter and 73% energy.
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- The 73% energy is a new discovery and it is called Dark Energy. “Dark” because we do not understand it. It is the anti-gravity in the vacuum of space that causes space to expand and the Universe to accelerate in its expansion.
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- The critical density for the 27% that is matter works out to be about the equivalent of 1 hydrogen atom of mass for every cubic meter of space. However, we can see with visible light only about 0.5% of this matter. That is all the stars, all the galaxies, everything that reflects light only adds up to 0.5 % of the Universe.
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- If we use X-rays and other wavelengths of the electromagnetic spectrum to find more matter we and find another 3% which is mostly hot interstellar gas. That leaves another 0.5% that we can not account for.
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- Astronomers call this form of Dark Matter, MACHOs. However, all the ordinary matter plus the MACHOs only adds up to 4%. What is the remaining is another 23%? Astronomers call this form of Dark Matter, WIMPs.
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- So far we have concluded that the Universe was made up of 27% matter and 73% Dark Energy. Of the 27% that is matter only 4% is gravitational ordinary matter. “Ordinary matter” being everything we know about that is made up of protons, neutrons, and electrons. Ok, so 4% we can explain and 23% we can not explain. Let’s call this 23% WIMPs.
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- WIMPs stands for “Weakly Interacting Massive Particles“. We call them matter because these particles, whatever they are, do interact with Gravity and with the Weak Nuclear Force. However, the WIMP particles react only weakly if at all with the Electromagnetic Force and the Strong Nuclear Force.
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- WIMPS do not emit or reflect light or any other electromagnetic radiation. They do not interact with other atomic nuclei. WIMPs in this sense have the same properties as neutrinos. However, neutrinos are nearly massless and travel near the speed of light.
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- WIMPs are very massive particles and thought to be slow moving and therefore cold. WIMPs are weakly interactive, massive, cold dark matter.
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- In the Standard Model for Particle Physics WIMPs can not be found. The closest relative is the neutrino. The WIMP particle has not yet been detected, except in our theories and in our imagination. But, imagination is more important than knowledge.
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- There are many experiments in works trying to detect the cold dark matter WIMPs. Here are a few acronyms for these experiments: CDMS, DRIFT, DEAP, SNOLAB, DAMA, EDELWEISS, COUPP, CRESST, HDMS, EXNON, ZEPLIN, WARP , PICASSO, SIMPLE .
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- Does it surprise you to learn the 23% of the 27%, or in other words 85% of the matter that fills the Universe are particles that we have not yet discovered? These unknown particles are the greatest source of gravity that defines the structure of the Universe. The gravity is there. There is just no light.
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- All of the evidence to date, including the above experiments, for the existence of Dark Matter depends on our understanding of gravity. This all assumes our equations for gravity are correct. If the equations are right Dark Matter is out there.
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- CDMS, Cryogenic Dark Matter Search usis detectors ½ mile underground in an iron mine in Minnesota. The deep iron mine is chosen to shield the detectors from Cosmic Rays and other background radiation.
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- Hundreds of billions of WIMP particles have passed through your body while you were reading this sentence. They pass right through without interacting with anything. Obviously they are hard to detect.
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- The CDMS detector is a kilogram crystal of germanium designed to vibrate if a single WIMP particle collides with a germanium atom. The detector is cooled to -273 C. The instrument is very sensitive and could detect as little as 2 weakly interactive collisions per year. None have been detected so far.
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- DAMA is a WIMP detector set up in Italy. This detector is 250 kilograms of thallium-doped sodium iodide crystals, 9.7 kilograms each. Electrons and nuclei in this crystal that receive a collision from a WIMP particle recoil and emit a photon that is detected in a photo-multiplier tube.
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- Astronomers use the rotation of the Earth around the Sun to separate the data caused by Dark Matter collisions versus other background radiation. DAMA has reported a positive signal but there as been no second source to verify it. More proof is needed.
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- DEAP is Dark Matter Experiment using Argon Pulse-shaped discrimination. This detector was operating in Queen’s University but recently moved to Sudbury, Ontario, Canada. Deep in a nickel mine the now SNOLAB experiment is 6,800 feet underground. PICASSO is Project In Canada to Search for Supersymmetric Objects. It uses a bubble chamber with Freon gas containing Fluorine atoms as a detector. It is located in the same lab.
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- XENON Dark Matter Search Experiment uses a liquid Xenon detector weighing 15 kilograms. It is installed in the Gran Sasso underground laboratory in Italy. And, there are many more labs all trying to win a Noble Prize with the first discovery of the WIMP particle.
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- In this review we are trying to identify the Dark Ordinary Matter that we can not find. 5% of ordinary matter that does interact with electromagnetic energy we can not detect for some reason.
- Astronomers call these objects, MACHOs, for Massive Astrophysical Compact Halo Objects. It is possible that these objects are Blackholes because they certainly are dark and do not emit any electromagnetic radiation. However, most Blackholes do have accretion disks rotating around them that do emit electromagnetic radiation.
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- Astronomers taking inventory of the total mass of all the Blackholes determined that it is not enough to explain the 25% Dark Matter. Remember, all the visible light astronomers can detect also adds up to 5% of ordinary matter. So, think of everything possible you can see and then realize that there is twice as much out there that is not gas but Massive Objects that you can not see.
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- Maybe these MACHOs only emit or reflect “very little” electromagnetic radiation making them very difficult to detect. These could be very faint neutron stars, Brown Dwarfs, White Dwarfs, or Red Dwarfs.
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- To detect these dark objects astronomers are trying to use gravitational lensing. Astronomers are counting on a few of this objects to pass directly in front of a visible star. When the light from the background star is bent by the gravity of the massive foreground object they image of the background star is magnified and the star appears brighter.
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- Astronomers using this technique can only account for 1% to 20% of the Dark Matter we are looking for.. There is a wide variation is their results ,but, they think dim dwarfs are nowhere numerous enough to account for the 25% ordinary Dark Matter we are looking for.
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- So what we are calling Dark Energy and Dark Matter is primarily an expression of our human ignorance. We are definitely in the dark on these matters.
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- Ok, besides the mathematics derived from the data in the Cosmic Microwave Background why do we believe that 23% of the Universe is full of Dark Matter? There are three other reasons:
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- First, the rotational curve of galaxies. Measuring the velocity of stars near the center bulge should be much faster than the velocity of the stars out at the perimeter of the galaxy edges that we can see.
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This is just the same as the planet Mercury velocity having much, much higher velocity than the planet Pluto. If Pluto had the same velocity as Mercury it would fly off into interstellar space because the Sun could not hold on to it.
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- However, in galaxies the perimeter stars have the same velocity as those near the center. In order for the math to work there must be 10 times more mass around the galaxy than we can see in order to hold these stars in their orbits.
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- The same problem arises when measuring the velocity of clusters of galaxies. In order to account for the speeds we can measure they must be orbiting 10 times more mass than we can see. Dark Matter is providing most of the gravity.
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- The third reason has to do with the Einstein Ring. When gravitational lensing is used to calculate the mass of the intermediate object that is bending the light from a background object there is 10 times more mass there than we can see.
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- So, the Dark Matter is out there. We are just going to call it WIMPs and MACHOs until we can figure out what it is.
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March 18, 2021 DARK ENERGY, WIMPs , MACHOs 952, 953, 954 3079
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--------------------- --- Thursday, March 18, 2021 ---------------------------
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