• The Field Guide to Particle Physics

  • 著者： Sean Downes
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The Field Guide to Particle Physics

著者： Sean Downes
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  • This is your informal guide to the subatomic ecosystem we’re all immersed in. In this series, we explore the taxa of particle species and how they interact with one another. Our aim is give us all a better foundation for understanding our place in the universe. The guide starts with a host of different particle species. We’ll talk about their masses, charges and interactions with other particles. We’ll talk about how they are created, how they decay, and what other particles they might be made of.
    ©2021 The Pasayten Institute. Attribution-Sharealike CC
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あらすじ・解説

This is your informal guide to the subatomic ecosystem we’re all immersed in. In this series, we explore the taxa of particle species and how they interact with one another. Our aim is give us all a better foundation for understanding our place in the universe. The guide starts with a host of different particle species. We’ll talk about their masses, charges and interactions with other particles. We’ll talk about how they are created, how they decay, and what other particles they might be made of.
©2021 The Pasayten Institute. Attribution-Sharealike CC
物理学 生物科学
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  • The Reason for Antiparticles

    The Reason for Antiparticles
    2022/12/07
    The Reason for Antiparticles.The Field Guide to Particle Physics : Season 3. Episode 8.https://pasayten.org/the-field-guide-to-particle-physics©2022 The Pasayten Institute cc by-sa-4.0The eBookThe Field Guide to Particle Physics eBook is now available! If you're looking to support the show, we've got some fun options for you here, or you could buy us a coffee!ReferencesThe definitive resource for all data in particle physics is the Particle Data Group: https://pdg.lbl.gov. This episode also pays tribute to Richard Feynman’s 1986 Memorial Dirac Lecture.Terrell-Penrose rotation can be viewed from a human perspective in at "A Slower Speed of Light" by MIT's GameLab. That demo also includes the relativistic doppler effect. Some other great videos by Ute Kraus and Corvin Zahn at spacetimetravel.org. See in particular their dice demo.The Reason for Antiparticles.Antimatter is uncommon, but it’s not exactly rare. Antiparticles - especially those generated by cosmic radiation - are all around us, all the time. But just what is it doing here?Antimatter is just like MatterIn a lot of ways, antimatter behaves just like matter does. Quarks make up protons? Antiquarks make up antiprotons… and antineutrons, too!Antiprotons and antielectrons - that is, positrons - combine to form antihydrogen atoms.The Antihydrogen Laser PHysics Apparatus - the ALPHA Experiment at CERN - studies the spectroscopic properties of antihydrogen. That is, it uses photons to give a little extra energy boost to those positrons. As those positrons relax to their ground state, they emit distinct wavelengths of light.Just like regular hydrogen atoms.Photons, you see, are their own antiparticles. They interact with matter and antimatter in precisely the same way.If there were any difference between hydrogen and antihydrogen - any difference in mass, spin or the magnitude of their electric charge - those wavelengths of emitted light would also be different. And the ALPHA experiment would be able to detect those differences.But no such differences have been observed.So again, what exactly is antimatter doing here in our physical reality?Antimatter annihilates MatterThe one thing antimatter does *not* do is hang around.Antimatter annihilates with ordinary matter. Electrons and positrons annihilate to form a pair of gamma rays, a pair of photons.If the universe were balanced between matter and antimatter, we wouldn’t be here. Or… perhaps worse… we’d rapidly disintegrate into a bursts of gamma radiation as our particles and those antiparticle partners annihilated.So if antimatter is so uncommon - why is it even here? What is the point, the reason for antimatter? Why does the universe need antimatter?To understand that, we need to talk about time travel.The Light ConeOur reality has four dimensions. Three space and one time. Famously, Einstein’s special theory of relativity tell us that these four dimensions are related.That relationship is nature’s conspiracy to make sure that nothing travels faster than the speed of light.One way to think about how this works is time travel. Literally traveling through time. When we are still, we are traveling forward, through time. When we spring up to go for a run, we’re still traveling through time, but we *rotate* our perceived motion through time into space. This is a four-dimensional sort of rotation. Sometimes this is called a Terrell rotation. There are some stunning visualizations of Terrell rotation linked in the show notes.The amount of Terrell rotation varies without speed. In a sense, we exchange some of our speed in the time direction to travel through space. The faster we go through space, the slower we go through time. There is a limit to this kind of rotation. We cannot rotate our motion so deep into space that we travel backwards in time. The most we can do is cause time to stand almost still, which happens when we travel just shy of the speed of light.Light of course always and only travels at the speed of light, in the absence of matter anyway. And because everything that must travel slower than light - everything that has mass - like protons, electrons, atoms and US - is subject to the ultimate cosmic constraint: the light cone.To visualize this four-dimensional cone, think of a camera flash. It’s a sphere of light moving outwards from a point. The tip of the cone is us snapping the photo, and the vertical part of the cone corresponds to the dimension of time.At any moment, our reality can be cut into two regions: inside or outside the light cone. All those points that light can touch - and those that it can’t. Inside the light cone represents everything we can possibly hope to effect later in time. Outside the light cone is outside of our agency to do so.The light cone - in other words - represents the boundary of causality.Because we cannot travel faster than the speed of light, any Terrell rotation we experience inside our light cone retains a positive flow of ...
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    13 分
  • Bonus : The Perils of Science Communication

    Bonus : The Perils of Science Communication
    2022/11/04
    Update! Best place to find associated references are linked in our substack essay:This is an essay that we originally posted on our substack page:https://pasayteninstitute.substack.com/p/the-perils-of-science-communicationA Bonus Episode for The Field Guide to Particle Physics : Season 3https://pasayten.org/the-field-guide-to-particle-physics©2022 The Pasayten Institute cc by-sa-4.0The definitive resource for all data in particle physics is the Particle Data Group: https://pdg.lbl.gov.The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! Get in touch.A History LessonIn the film “Einstein’s Big Idea”, French Scientist Antoine Lavoisier is portrayed just as he discovers how to split water into oxygen and hydrogen gas, thereby realizing the conservation of mass in chemical reactions.Lavoisier is generally credited with disproving the phlogiston theory of combustion and reframing Chemistry as a quantitive science.This shift from the qualitative is emphasized in a specific scene where Lavoisier meets with an excited young man who is pitching his apparatus for observing heat. Lavoisier assertively dresses down the man for failing to meet the modern, quantitative standards of scientific experiment.This man is later revealed to be a revolutionary, and Lavoisier’s final act of the film ends with an escort to the guillotine.While dramatized, the message was clear:Science needs popular support, and clear communication is not enough. We need to do more than educate. We need to build community with inspiration, excitement and respect for Science. We also need to share with folks how Science works1.Respect for Science is a value we share as Scientists. But it’s not universal. Whether or not Science is morally entitled to respect is irrelevant. Without constantly striving to earn and refresh that respect from Society, it can be lost.The Siren Call of the OutsiderScience Communication is a rapidly professionalizing field that encompasses a spectrum from dynamic professional speakers to university department media managers to science-minded journalists. From journalists like Natalie Wolchover, to Professors like Tatiana Eurikhamova, there’s a lot of great work being done by people I admire.The line between #SciComm and marketing is extremely thin, and unfortunately, the internet’s content treadmill incentives their confluence.Journals and university departments alike publish heroic press-releases about recently accepted scientific publications by department staff as if they were breakthrough results. But more often than not, these results are merely slow, incremental progress.How is anyone but a specialist supposed to understand the difference?The SciComm ecosystem, in other words, is full of noise. Especially for the general audience.Cutting through that noise is tough. But content editors have had a tool for this as long as humans have printed newspapers: headlines.Here’s a recent one:“No one in physics dares say so, but the race to invent new particles is pointless.In private, many physicists admit they do not believe the particles they are paid to search for exist – they do it because their colleagues are doing it”Sabine Hossenfelder - the Guardian Opinion (26 Sept 2022)As a lead generator, this headline and its subtitle are incredible. Given the current intellectual climate around distrusting experts, it hits all the high points: All these experts have no idea what they’re doing, there’s some structural conspiracy and they’re wasting your money.Taken with the author’s antagonistic, “outsider” persona2, it's direct aim at an established field of study. It's a recipe for clicks, likes and angry shares.Unfortunately, the piece willfully and violently mischaracterizes the current state of particle physics. It’s so flagrant - and so short - that it’s worth a read. A Reading Guide to Hossenfelder’s ComplaintHere is a highlighted list of rhetorical and factual errors which both discredit the thesis of Hossenfelder’s piece and demonstrates its disservice to the endeavor of Science Communication.Broadly, high energy or “particle” physics is the study of what constitutes matter and energy, as well as the forces that govern their dynamics. Like any good science, it involves the study of both what particles we see as well as how those forces work.Hossenfelder’s piece begins with a collection of names of physical models at various stages of generality. As written, it conflates them with concrete models for actual, physical particles. Doing so betrays such a misunderstanding of how Particle Physics works in practice that it was almost certainly an editorial decision.Let’s consider some examples.The SfermionThe sfermion is a very broad class of particle, a collective noun akin to saying “cats” or even “mammals”. They are particles associated to fundamental fermions - particles of matter like the electron, muon or up quark - by a...
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    16 分
  • Bonus : The Physics of Muon Colliders

    Bonus : The Physics of Muon Colliders
    2022/09/27

    The rest of season three is still under development! We wanted to improve the clarity before publishing. Parity violation just isn't that easy to talk about! In the mean time, here is the second episode in a short bonus series about the state and future contemporary particle physics. I hope you enjoy it!

    This is an essay that we originally posted on our substack page:
    https://pasayteninstitute.substack.com/p/the-physics-of-muon-colliders

    This is a follow up to our 4 Reasons to Build a New Particle Collider
    You can also get the bumper sticker version here!

    A Bonus Episode for The Field Guide to Particle Physics : Season 3
    https://pasayten.org/the-field-guide-to-particle-physics
    ©2022 The Pasayten Institute cc by-sa-4.0
    The definitive resource for all data in particle physics is the Particle Data Group: https://pdg.lbl.gov.

    The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! Get in touch.
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    10 分

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