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- 2017 - A lesson in particle physics.- How can the difference of + or - 1/2 a spin create the whole universe , or not? Quantum Mechanics has the strangest rules , but, that is what the math says. Also, the rules always work. When we get to the quantum level all the rules of physics change. A simple thing as direction of spin is the difference enabling everything in the universe to exist.
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- How can the difference of + or - 1/2 a spin create the whole universe , or not?
Quantum Mechanics has the strangest rules , but, that is what the math says. Also, the rules always work. 100 years of trying have not found a flaw in math versus observation. Quantum Mechanics becomes a different reality. We are the ones who have to adjust in order to begin to understand it.
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- The super small world for all things is the “quantum” level. When we get to that level all the rules of physics change. We enter the world of new physics. For example: Recent discoveries has photons behaving differently than we had defined in earlier physics.
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- First you entangle photons by passing them through a crystal creating photon pairs. Regardless of their distance of separation. Distances great enough that even the speed of light would not allow communications between them. Yet, changing one photon immediately, instantaneously, changes the other photon. One spin up the other spin down, one spin down and the other spin up. Instant communication faster than 186,000 miles per second.
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- Now, we thought entangled photons were created next to each other, side by side. But, new data shows that entangled pairs can be formed in far distant parts of the crystal. Separation of hundredths of a micron which is a far distance at the atomic levels.
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- Quantum Computing was counting on understanding entangled photons. The hope was a whole theater of new inventions. Now, they have something else to worry about.
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- It seems everything has a certain quantum “fuzziness” to it.
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- Entangled photons have correlated polarization, but, they don’t have to be created in the same atom, or even near the same atom. Being created in spatially separate points creates a new positional uncertainty to deal with. Designing computers has a new uncertainty to take into account.
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- Electrons and photons, in scientific terms, are called Fermions and Bosons. All particles have properties of mass and electric charge. They also have properties of spin, an intrinsic spin of angular momentum.
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- Fermions, which I will call electrons to use a more familiar term, have a 1/2 integer spin
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- Bosons , I will call them photons, have whole number spins, 1, 2, 3, etc. That is it , there are no other type of particles in particle physics. These two families are fundamental to the entire universe.
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- We even have a spin for a yet undiscovered particle. The “graviton” is to have a spin of two. It is the boson responsible for the force of gravity. Not yet discovered. And , not yet reconciled with Einstein’s theory of gravity being the result of bending space and time.
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- Spin is angular momentum. Is that what determines matter versus antimatter, or mass versus massless, or quarks versus leptons?
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- Electrons have anti-electrons called positrons, I will still call them anti-electrons. There are no anti-photons. That is a good thing because if anti-electrons and electrons come in contact they annihilate each other. Imagine what that would be like with light photons annihilating each other.
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- Two up quarks and one down quark make a positive proton. Protons are the nucleus of atoms.
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-One up quark and two down quarks make a neutron, also in the nucleus of atoms. Protons and neutrons are called “fermions”.
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- If you combine two fermions , a quark and an antiquark, you get a meson, which is another type of boson.
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Take notes if you need to keep up with this new vocabulary. Fermions , ie. electrons, are a spin 1/2. If there is an odd number of them they remain fermions with spin + or- 3/2, or +or- 5/2, etc. But, if there is an even number and the spin becomes an integer, + or - 1, or +or- 2, etc. then it becomes a boson, i.e.: a photon.
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- Electrons are limited to two in the ground state of every atom. The ground state is the lowest energy shell. The Pauli Exclusion Principle requires that no two electrons can occupy the same quantum state. Two electrons in the ground state must always have the opposite 1/2 spins.
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- This becomes very interesting when you learn about entangled electrons communicating their state so they always remain with opposite spins regardless of distance of separation.
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- This Exclusion Principle is what allows atoms to have different properties. Each element in the Periodic Table of Elements is unique in its atomic structure. This Principle is also what allows molecules to form with multiple elements.
- Bosons, photons, unlike fermions, electrons, photons can occupy the same quantum states. An example is known as Bose Einstein Condensation. Helium for example, having an even number of fermions, can become a superfluid at low temperatures. Other gases have also been cooled into this condensation state.
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- It is the Pauli Exclusion Principle in atomic structures that is responsible for keeping dense objects like White Dwarf stars , and Neutron stars from becoming blackholes. The gravity has to become much stronger to break down this repulsion inside the atoms.
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- The Bose Einstein statistics for bosons , photons, is a why the Cosmic Microwave Background is at a temperature of -2.73 Kelvin today.
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- The Fermi Durac statistics for fermions, electrons, is why the Cosmic Neutrino Background is 0.8 Kelvin cooler, at 1.93 Kelvin.
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- Our Universe from the largest to the smallest is full of mysteries at both ends. We have a lot more to learn. What is amazing is that the two sides seem to come together in a Blackhole that we can not see.
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- At the small end is particle physics. Particles , like an electron, have some intrinsic properties. They have mass, charge, and spin, or angular momentum. An electron is fundamental. A proton is not fundamental. It is made up of fundamental quarks
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- The proton has three quarks that gives it a +1 positive charge. The three quarks are +2/3 and +2/3 and -1/3 = +3/3 or +1.
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- The proton spin is more complicated. The proton has an angular momentum of 1/2.
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- The 3 valance quarks are two spin up and one spin down together constituting a spin of 1/2. Spin is a physics description for intrinsic angular momentum. Particles are not physically spinning.
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- A proton having 2 up quarks and one down quark are held together by gluons.
(Glue, get it). The gluons are massless, color-charged particles that mutually bind the three quarks together into a proton.
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- Each quark has a spin of 1/2. But, the three quarks alone can not account for the protons spin of 1/2. It is more complicated than that. Experiments have discovered that the three quarks only contribute 30% of the protons spin.
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- The quarks are not free. They are bound together with gluons inside the proton. The gluons are spinning as well. The gluon’s spin screens over the quark’s spin. The Pauli Exclusion Principle prevents identical particles from occupying the same state. So the missing 70% for the total spin appears to be real.
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- All quarks and gluons together are called fermions. All fermions have a spin of 1/2.
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- Bosons are the other category of particles. And, they have an integer spin, 1,2,3... Bosons , like the photon and the gluon, have an integer spin of 1.
- ( The Higgs Boson has a spin of 0. The Graviton has a spin of 2. )
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- Hang in there you thought this was going to be easy, proton, electron, + , - That is all we need to know. It is far more complicated we are just getting started. There is much more to learn.
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- Calculations using QCD methods put the gluons contributions to the proton spin at 50%. The remaining 20% must come from the orbital angular momentum created by the gluons orbiting the three quarks.
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- It is remarkable that simply adding up the spin for the three quarks gets you to the right answer , +1, but for the wrong reason. 70% of the right answer for proton spin comes from orbiting gluons and angular momentum.
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Think about it ! A simple thing as direction of spin is the difference enabling everything in the universe to exist. Just 1/2 intrinsic angular momentum creates all that diversity in atoms. Amazing! That is today’s lesson in particle physics. Hope you stuck with it to the end.-
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