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--------------------- 2663 - PHYSICS - the theory for everything?
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- For me physic started out learning about the simple atom. The atom is made up of protons and electrons. The number f protons in the atom determines all of the 90 elements from hydrogen to oxygen to iron to uranium.
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- Atoms make up our material world. Electrons provide us electricity and magnetism. Light is a form of electromagnetic energy. Light is massless and travels at only one speed , 186,000 miles per second.
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- Atoms are made of particles smaller than protons and neutrons. These are quarks and gluons that were first discovered just a few decades ago. Neutrinos were also discovered to be flooding us from the Sun arriving in three different varieties.
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- Today we believe that all this we know so far makes up only 5% of the total Universe. 95% of the Universe is made up of dark matter and dark energy that we classify as unknown.
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- With that state of affairs what are the new answers we are trying to uncover? Why is the Universe expanding at an ever increasing pace? Cosmic inflation is stretching our tiny Universe. And, somehow it turned this cosmic energy into matter. How did the matter even get into us?
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- It is likely that this same Cosmic Inflation created an equal amount of matter and antimatter. One theory is that a phase transition after inflation led to a tiny bit more matter than anti-matter and at the same time created cosmic strings which would produce slight ripples in space-time known as gravitational waves.
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- Why is there more matter than antimatter? That answer, in turn, could explain why everything from atoms to black holes exists.
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- Billions of years ago, soon after the Big Bang, cosmic inflation stretched the tiny seed of our universe and transformed energy into matter. Physicists think inflation initially created the same amount of matter and antimatter, which annihilate each other on contact.
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- But then something happened that tipped the scales in favor of matter, allowing everything we can see and touch to come into existence. The explanation is hidden in very slight ripples in space-time.
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- If you just start off with an equal component of matter and antimatter, you would just end up with having “nothing“, because antimatter and matter have equal but opposite charge. Everything should just annihilate.
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- Obviously I escaped this annihilation soI cold rite this. But why? The answer might involve very strange elementary particles known as “neutrinos“, which don't have electrical charge and can thus act as either matter or antimatter.
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- One idea is that about a million years after the Big Bang, the universe cooled and underwent a phase transition, an event similar to how boiling water turns liquid into gas. This phase change prompted decaying neutrinos to create more matter than antimatter by some "small, small amount.
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- Scientists have figured out a way we might be able to see this phase transition. They proposed that the change would have created extremely long and extremely thin threads of energy called "cosmic strings" that still pervade the universe.
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- These cosmic strings would most likely create very slight ripples in space-time called “gravitational waves“. Detect these gravitational waves, and we can discover whether this theory is true.
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- The strongest gravitational waves in our universe occur when a supernova, or star explosion, happens, when two large stars orbit each other; or when two black holes merge. But the proposed gravitational waves caused by cosmic strings would be much tinier than the ones our instruments have detected before.
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- Further study has made an encouraging discovery: In all cases, cosmic strings would create gravitational waves that would be detectable by future observatories, such as the European Space Agency's Laser Interferometer Space Antenna and proposed Big Bang Observer and the Japan Aerospace Exploration Agency's Deci-hertz Interferometer Gravitational wave Observatory.
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- If these strings are produced at sufficiently high energy scales, they will indeed produce gravitational waves that can be detected by these planned observatories.
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- Or another explanation has our universe flooded with hundreds of kinds of nearly invisible particles and that, long ago, formed a network of universe-spanning strings?
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- This second theory is a prediction of “string theory“, the best attempt at a “theory of everything“. This theory has little particles, known as “axions“, that would create a vast "axiverse." This incomprehensibly huge network of strings may be detectable in the near future with microwave telescopes that are actually being built.
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- The axion, named by physicist Frank Wilczek in 1978, gets its name because it's hypothesized to exist from a certain kind of symmetry-breaking, when certain patterns appear in mathematics.
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- There's one kind of symmetry, called the “CP symmetry“, that says that matter and antimatter should behave the same when their coordinates are reversed. But this symmetry doesn't seem to fit naturally into the theory of the strong nuclear force.
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- One solution to this puzzle is to introduce another symmetry in the universe that "corrects" for this misbehavior. However, this new symmetry only appears at extremely high energies. At everyday low energies, this symmetry disappears, and to account for that requires a new particle, the “axion“.
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- String theory is an attempt to unify all of the forces of nature, especially gravity, in to a single theoretical framework. For string theory to work and for the mathematics to even have a hope of working out, our universe must have more than the usual three dimensions of space and one of time; there have to be extra spatial dimensions.
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- These spatial dimensions have to be tiny and curled up on themselves at scales so small that they evade normal efforts to spot them. We are not exactly sure how these extra dimensions curl up on themselves, and there's somewhere around 10^200 possible ways to do it. “10^200” is a one followed by two hundred zeros, a very large number.
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- But what these dimensional arrangements appear to have in common is the existence of axions, which, in string theory, are particles that wind themselves around some of the curled-up dimensions and get stuck.
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- String theory does not predict just one axion but potentially hundreds of different kinds, at a variety of masses, including the axion that might appear in the theoretical predictions of the strong nuclear force.
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- Could axions make up dark matter, which seems to be responsible for giving galaxies most of their mass but can't be detected by ordinary telescopes?
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- In the earliest moments of the history of our cosmos, the universe went through phase transitions, changing its entire character from exotic, high-energy states to regular low-energy states.
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- During one of these phase transitions happened when the universe was less than a second old. The axions of string theory didn't appear as particles. Instead, they appeared like loops and lines. Axions were a network of lightweight, nearly invisible strings crisscrossing the cosmos.
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- This hypothetical “axiverse“, filled with a variety of lightweight axion strings, is predicted by no other theory of physics but string theory.
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- How can we search for these axion strings? Models predict that axion strings have very low mass. Axions likely wouldn't mingle with other particles. There could be millions of axion strings floating through the Milky Way right now, and we wouldn't see them.
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- The cosmic microwave background (CMB) is the oldest light in the universe, emitted when it was just 380,000 years old. This light has soaked the universe for all these billions of years, filtering through the cosmos until it finally hits something, like our microwave telescopes.
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- So, when we look at the CMB, we see it through billions of light-years' worth of universe. It's like looking at a flashlight"s glow through a series of cobwebs: If there is a network of axion strings threaded through the cosmos, we could potentially spot them.
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- Researchers in 2019 calculated the effect an axiverse would have on CMB light. They found that, depending on how a bit of light passes near a particular axion string, the polarization of that light could shift. That’s because the CMB light (and all light) is made of waves of electric and magnetic fields, and the polarization of light tells us how the electric fields are oriented
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- This is something that changes when the CMB light encounters an axion. We can measure the polarization of the CMB light by passing the signal through specialized filters, allowing us to pick out this effect.
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- The researchers found that the total effect on the CMB from a universe full of strings introduced a shift in polarization amounting to around 1%, which is right on the verge of what we can detect today.
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- Future CMB mappers, such as the Cosmic Origins Explorer, Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), and the Primordial Inflation Explorer (PIXIE) , are currently being designed.
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- These futuristic telescopes would be capable of finding an axiverse. And once those maps come online, we'll either find that we live in an axiverse or rule out this particular prediction of string theory.
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- Either way, there's a lot to untangle. Stay tuned , we have a lot more to learn.
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- March 11, 2020 2663
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--------------------- Thursday, March 12, 2020 --------------------
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