- 2905 - PHYSICS - in a nutshell? This review is mostly about “particle physics” in a nutshell. It starts out with the periodic table of about 100 elements. That is not many elements when you think it represents everything that is around us and also everything in all the other stars and planets. The 100 elements along with the electromagnetic force and gravity force is most of what we experience in our macro world.
--------------------------- 2905 - PHYSICS - in a nutshell?
- The macro world is the world of chemistry. The elements start with the hydrogen atom which has a single proton and a single electron and work their way up to uranium with 92 protons and 92 electrons.
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- Fusion is the process used to combine atoms together to build elements up from hydrogen to uranium. Fission is the process where elements break down and are reduced down from uranium to hydrogen working through the 90 elements in between.
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- Particle physics is about particles that are inside the atoms that make up the elements. This takes us from the macro world to the micro world. Here are the relative sizes of the particles we are talking about starting with the atom. A solid about the size of a marble contains 600,000,000,000,000,000,000,000 atoms. (Avagado’s Number for a Mole):
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---------------------- atom -------------- 10^-10 meters
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---------------------- nucleus ----------- 10^-14 meters
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---------------------- proton ------------ 10^-15 meters
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---------------------- electron ----------- 10^-18 meters
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---------------------- quark -------------- 10^-19 meters
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- The quark, the fundamental particle inside the protons and neutrons in the nucleus is 1 billion times smaller than the atom. To illustrate the relative size in dimensions we know say the quark is the size of a marble, then:
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---------------------- atom -------------- distance of a 10 kilometer race, 6.2 miles.
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---------------------- nucleus ----------- football stadium and parking lot
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---------------------- proton ------------ football field
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---------------------- electron ----------- soccer ball
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---------------------- quark -------------- marble
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- All atoms except hydrogen have neutrons as well as protons. The number of protons determines the element and the number of neutrons determines the isotopes of each element. Free neutrons are unstable and have a mean lifetime of 885.7 seconds, about 15 minutes.
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- A neutron weighs 1.6749*10^-27 kilograms. Inside the nucleus the neutrons are stable and held together by the strong and weak nuclear forces. When a neutron decays it turns into a proton, an electron and an antineutrino.
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- A proton and an electron can combine, (fuse) and form a neutron. A neutron can break apart (fission) and turn into a proton and an electron. Each process of fusion or fission must follow the laws of Conservation and the laws of Thermodynamics.
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- Each process has some inefficiencies, entropy always increases, and other particles are involved to make the process more complicated and to maintain the laws of Conservation.
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- A good example is the fusion that occurs in the thermonuclear reactions in the core of the Sun. When 4 hydrogen nuclei (4 protons) fuse into 2 helium nuclei (2 protons and 2 neutrons each) a small amount of mass is left over. The extra mass converts into energy in the form of gamma rays that radiate away from the core to heat up the Sun.
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- The radiating gamma rays are absorbed and reflected by other particles and this electromagnetic energy is transformed into kinetic energy of the particles, which we call heat. The kinetic energy of particles is thermal energy, or heat that we measure as temperature. Temperature is actually the average velocity of moving particles.
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- Temperature is the average kinetic energy of billions of vibrating or moving particles. In the case of the average temperature of a room, it is the average kinetic energy of air molecules. The average room temperature is about 30C or 300 Kelvin.
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- At that temperature the average velocity of the air molecules is the velocity of the speed of sound or about 700 miles per hour. If the temperature goes up the average velocity of the atoms increases. If the temperature goes down the average velocity of the atoms decreases. If the temperature goes down to zero Kelvin, absolute zero, the atoms almost stop moving. Only quantum vibrations exit when the temperature is absolute zero.
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- Going the other direction when temperatures get hot enough then more processes of fusion and fission can occur. Some of the fission processes can occur at room temperature. Radioactivity is the fission process that occurs naturally in elements that have excess neutrons in the nucleus.
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- Cosmic Rays and Particle Accelerators accelerate particles into collisions that create extreme temperatures spraying fission particles in an exploding shower. There are hundreds of strange particles created in combination with the 100 elements and the 24 fundamental particles. 12 are the fundamental particles of ordinary matter and 12 are antiparticles. The antiparticles are rare and short lived but they are exactly the counterpart of the particles except they have the opposite charge.
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- All of these 24 particles and antiparticles have mass, although we do not know what causes a particle to have mass in the first place. If a particle does not have mass it can not stand still, it can only travel at 186,000 miles per second. The Photon is massless and it must always travel at light speed.
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- The 24 particles and antiparticles that have mass are called “fermions” and they all have ½ spins. The massless particles like the photon are called “bosons” and they all have integral spins.
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- Let’s first talk about the fermions and we only need 12 because the antiparticles are exactly the same except with the opposite charge. The 12 fermions come in 3 generations of four particles. Each generation is a phase transition to higher energy particles. Think of the phase transitions from solid , to liquid, to gas. Think of ice, to water, to water vapor.
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-------- 1st generation --------- up quark ------- down quark ---- electron ----- neutrino
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-------- 2nd generation ------ charm quark ---- strange quark ----muon ----- muon neutrino
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-------- 3rd generation ------- top quark ------ bottom quark ----- tau ------- tau neutrino
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- For example: the muon can be viewed as a phase transition to a heavier electron. Remember mass and energy are the same thing according to E = mc^2. So a muon is a high energy electron. And, a tau is higher energy still. Here are their energy levels in electron volts /c^2.
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-------- 1st generation ------- electron ----- 511,000 eV
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-------- 2nd generation ---------muon ------- 106,000,000 eV
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-------- 3rd generation ---------- tau -------- 1,777,100,000 eV
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------------------------ (Charge -1 and spin ½, 3/2, 5/2, etc)
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- Physicists express mass in electron volts, but it is really electron volts / c^2. They just ignore the c^2 for convenience. These same particle masses can also be expressed in kilograms, but, like I say physicists don’t use these units in particle physics:
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-------- 1st generation ------- electron ----- 9.11 * 10^-31 kilograms
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-------- 2nd generation ---------muon ------- 1.9 * 10^-30 kilo grams
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-------- 3rd generation ---------- tau -------- 3.2 * 10^-27 kilograms
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- The charm quark is simply a higher energy up quark. And, a top quark higher still:
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-------- 1st generation ------- up quark ----- 300,000 eV
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-------- 2nd generation ---------charm quark------- 1,300,000,000 eV
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-------- 3rd generation ---------- top quark------- 175,000,000,000 eV
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----------------------------- (Charge +2/3, spin ½, 3/2, 5/2,etc)
- I mentioned that radioactivity is a natural, room temperature, fission process that occurs in elements that have an excess of neutrons in the nucleus. This is called “Beta Decay” when a neutron spontaneously decays into a proton, plus an electron, plus an anti-neutrino.
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- What happened inside the neutron was a down quark decayed into an up quark. A neutron is composed of one up quark (+2/3) and two down quarks (-1/3). Up quarks have +2/3 charge and down quarks have a -1/3 charge so the three quarks together have a neutral charge.
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- When a neutron’s down quark decays into a up quark the three quarks together become a proton with two up quarks ( +2/3 +2/3) and one down quark(-1/3) = +3/3 = +1 charge for the proton.
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- Now, back to the massless particles called bosons that always travel at the speed of light. These are the force carrier particles for the four fundamental forces. The electromagnetic force and the gravity force carry over large distances but their strength decreases by the square of the distance.
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- The weak and strong nuclear forces work over very small distances limited to inside the nucleus. So, to compare them we measure the strength at 3*10^-7 meters. (These are all bosons and have an integral spin of 1,2,3, etc. times 6.6*10^-16 eV*sec /wavelength)
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-------------- gravity force ---------- graviton ---- 10^-41 ------------- 0 mass
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-------------- weak force ------- W boson --------- 10^-4 -------- 80,000,000,000 eV
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-------------- electromagnetic force -- photon ------ 1 --------------- 0 mass
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-------------- strong force ----------- gluon --------- 60 --------------- 0 mass
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- Why do the +,- W bosons and the Z boson have such enormous mass? Because of this enormous mass the particles can only act over a very short distance for the weak force. The weak force is the one responsible for Beta Decay or as we learned for the down quark decaying into the up quark when the neutron becomes a proton. The rest of these bosons are massless and travel at the speed of light.
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- The photon is the most familiar of the massless particles. It carries the electromagnetic energy for all wavelengths. The amount of energy = 6.7*10^-34 times the frequency.
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- For visible light a single photon is around 4*10^-19 joules of energy, or about 2.5 eV. Photons are emitted whenever an electric charge is accelerated. A photon is emitted when an electron is dropped to a lower energy level inside the atom. A photon is emitted when a particle and antiparticle annihilate each other. A photon is absorbed in the opposite reactions to each of the processes above.
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- The photon carries spin and angular momentum and it can have two possible polarizations, Left-handed and Right-handed spin. Photons do not experience time because they are traveling at the speed of light. Left and Right-handedness is unique to particles that have no mass.
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- That is it in a nutshell. Physics in a nutshell what more do you need to know?
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- 2882 - PHYSICS - the way I learned it? Physics is the science of nature. It is the study of the Universe’s matter, energy, motion and force. Matter and Energy are the same thing. Energy = 90,000,000,000,000,000 * mass. ( E=mc^2).
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- 2738 - PHYSICS - Spacetime, Energy, and Calculus? Clocks run slower as you go faster and faster, yes, that includes biological clocks. NASCAR drivers are younger than their twin brothers the accountants . Using Einstein’s equations you can actually calculate how much younger. But, this review should be Newtonian, actually it is whole course in Physics
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- 2703 - PHYSICS - Uncertainty and Exclusions principles? Quantum Mechanics math had to be invented to work on the atomic scales. Much of this Quantum Mechanic’s math relied on two principles, the Uncertainty Principle and the Exclusion Principle. Both of these introduced math that we had not seen before.
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- November 15, 2020 524 973 2011 2905
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--------------------- --- Sunday, November 15, 2020 ---------------------------
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