Of Particular Significance

Blog – Of Particular Significance

First, a couple of things you might like to read:

  • There was a long-overdue article from the New York Times as to how, after eight years of cuts from the Bush administration during good economic times, followed by additional inevitable cuts during the Great Recession, formerly world-leading scientific research efforts in the United States are on the verge of collapse, risking far more than the scientific research itself.  The situation is far more dire, in my opinion, than the tone of the article implies; the brain drain of talent leaving the US is frightening and well underway, and the problems are by no means limited to particle physics and astrophysics.
  • The article that I described last month by Moni Bidin et al. that claimed (loudly, in the press) that there was little evidence for dark matter in the Sun’s interstellar neighborhood (but far from the center of the Milky Way galaxy) has been discredited by one of the world’s leading astrophysicists, working with a younger collaborator. The claim (made without a big press release) of Jo Bovy and Scott Tremaine, from the Institute for Advanced Study in Princeton, is that one of the assumptions on which the Moni Bidin et al. argument was based is inconsistent with data and therefore wrong, ruining the argument. Bovy and Tremaine have replaced this assumption with a different one that is consistent with data, and they conclude, in contradiction to Moni Bidin et al., that the corrected argument leads to the conclusion that there is indeed dark matter in the vicinity — roughly the amount one would expect from other considerations. In short, the Moni Bidin argument, once corrected, actually leads to more evidence in favor of the existence of dark matter! A short description of the situation is given on the Resonaances blog.

Second: I’m starting to think about a new section for this website.

Particle physics, quantum mechanics, and all the strange-sounding stuff that many physicists study are often thought of as esoteric, abstract, and irrelevant to ordinary life. But in fact our world is directly impacted, in many different ways, by quarks and photons and quantum uncertainty and the like; these things are not abstract at all. To make this point more accessible, a website like this one needs a good introductory section to help beginners make their way into the world of particle physics. So I’m going to be constructing this section over the coming months. Feedback from readers as to whether the material is readable and sufficiently introductory will be very valuable, so please feel free to offer your comments.

One of my first tasks is to talk about the architecture of the universe — how its parts are formed from smaller parts, on down to the smallest objects we know about so far. Of course there are many other introductions to this subject already on the web (and a few of them are even correct!) What I hope will make my presentation a little different is the inclusion of some insights into not only what we know about the structure of the universe but also how we know it, and additionally some comments on how our lives are impacted by each level of detail in the architectural hierarchy.

The first phase of this process will be to look at how ordinary matter that we are made from and surrounded by is constructed from the basic ingredients of electrons, quarks (and anti-quarks and gluons), and the strong nuclear, electromagnetic and gravitational forces. The figure below gives a preview of what’s coming (and you can click the figure for a larger version.)

The hierarchical architecture of ordinary matter. At the lowest known level are found electrons (e), quarks (u,d,s) and anti-quarks, along with force particles such as gluons. Up and down quarks, gluons and pairs of quarks and antiquarks make up the proton and neutron (the “nucleons”), and are held together by the strong nuclear force; a residual effect of that force holds the protons and neutrons together in atomic nuclei, of which there are a few hundred. The electromagnetic force allows electrons to attach themselves to nuclei, forming a hundred or so chemically distinct types of atoms. A residual effect of the electromagnetic force then binds the atoms together into a gigantic zoo of molecules, out of which the vast complexity of ordinary materials — the air, the sea, the rocks underfoot, and the immense diversity of life — are formed. Meanwhile gravity crushes the earth’s rock into a rough sphere and keeps the air, water, and living things from floating off into outer space.  The rough sizes of the objects appearing at each level of structure are indicated at right.
Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 25, 2012

What would the Grand Canyon look like if it had sunset light without the sunset shadows?  Sunday’s annular solar eclipse provided a hint of an answer:

The Grand Canyon from the North Rim (Cape Royal), during the annular solar eclipse of May 20th, 2012, at maximum eclipse (“ring of fire”). Photo Matt Strassler, all rights reserved.

Quite a first visit to the North Rim of the canyon.  Maximum eclipse occurred an hour before sunset, and the sun set with a small piece of the moon’s silhouette still covering its disk.  As a result, the amount of sunlight remained low for the entire hour, bathing the canyon in the low light that allows its layers of color and geological time to be more easily seen.

Meanwhile, in the other direction the sun was still far too bright to look at with the naked eye, or photograph without a filter. Lacking both a proper filter and a tripod, this is all I could manage with my camera, I’m afraid:

The annular eclipse of May 20th, 2012, showing the moon traveling across the sun, along with various unfortunate camera and filter effects. What can I say? I’m an amateur photographer. Photo Matt Strassler, all rights reserved anyway.

I think that when you look at photos of an eclipse (certainly I find this for myself) it is easy to miss the visceral nature of the experience. When you are watching it happen, you can see (through a proper filter, or with a projection), second by second, the slow but steady glide of the moon across the sun. You can detect the ring of sunlight changing shape, from a perfect circle to one that is thicker on one side than the other, and finally turning back into a crescent. The process is a dynamic one, as well as a visual feast. And this is part of what makes it so beautiful — not just what one sees with the eyes, but what one feels as a witness to the steady motion of the heavens.

[p.s. don’t miss the other two crescents to see right now: crescent Venus and crescent Moon near each other in the western sky tonight!]

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 22, 2012

Hi all! I said that posts would be sparse for a couple of weeks, but I didn’t realize quite how sparse! But I’m gradually getting back on-line here.

Right now, what’s occupying my attention for the next 48 hours is all in the sky: three crescents, and a ring. I’ll be brief, but if you want more explanation about the geometry involved, you might want to read my very relevant article about geometry and the beauty of the heavens. (more…)

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 20, 2012

Posts are limited this week and next — partly because a draft of a document about “exotic” Higgs particle decays (which I wrote about here,  here,  here,  here and  here), relevant to how the Large Hadron Collider experiments ATLAS and CMS might collect their data in 2012 (in particular, how they might trigger on such decays), needs to get done right away. (Data’s already coming in! we’re later than I’d like.)   And it really has to get done now since I’m traveling next week with limited internet.

Meantime, a reminder in case you missed it: For those of you in the New York City area: I’ll be joined by the wonderfully talented singer-songwriter-pianist Andrea Wittgens in giving a physics/music joint performance/presentation at the storied Cornelia Street Cafe, Sunday May 13th at 6 p.m., as part of their Entertaining Science series.  It’s entitled Rhapsody for Piano and Universe, and intended for the general public.  The place is pretty small, so get reservations in advance by calling 212.989.9319.

One more heads-up: again in NYC, June 16th, I’ll be giving a lecture:

THE EINSTEIN OBSESSION: SCIENCE, MYTH AND PUBLIC PERCEPTION

June 16th, 2pm

Jefferson Market Library, 425 6th Ave. West Village, NYC

Free and open to the public!

Who hasn’t heard of Einstein? We all know Einstein failed eighth grade math. (Although he didn’t.)  We know he showed energy is the same thing as mass (or was it “matter”?), that he’s the father of the atomic bomb, that he was an old man with frizzy hair, and that he was a patent clerk whose theory was that everything is relative and that nothing can move faster than light.  This messy assortment of half-truths and misconceptions permeates our culture and affects public perceptions of science, at many different levels.  In this talk we’ll consider how our culture’s obsession with Einstein impacts efforts to convey science to the public.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 11, 2012

One of the strange but crucial features of our world is that every type of atom except hydrogen contains neutrons in its nucleus, even though neutrons, on their own, decay (to a proton, electron and anti-neutrino) within about 15 minutes on average.  At first glance this seems puzzling.  At second glance too.  How can stable matter be made from unstable ingredients?

The reason this is possible has everything to do with Einstein’s special relativity, and the way mass and energy are intertwined there.  A crucial role is played by the energy that is most important for binding things together, which I’ve called “interaction energy”.

I’ve now written an article explaining why neutrons inside of nuclei can be stable, giving the example of the deuteron (one proton bound to one neutron) which is the nucleus of “heavy hydrogen”, or “deuterium”.  If you understand this example, you’ll basically understand the point for other nuclei as well.

[For those of you in the New York City area: I’ll be joined by the wonderfully talented singer-songwriter-pianist Andrea Wittgens in giving a physics/music joint performance/presentation at the storied Cornelia Street Cafe, Sunday May 13th at 6 p.m., as part of their Entertaining Science series.  It’s entitled Rhapsody for Piano and Universe, and intended for the general public.  The place is pretty small, so get reservations in advance.]

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 8, 2012

The final panel discussion at the Maryland SEARCH workshop — six theoretical particle physicists talking about the 2011 experimental results from the Large Hadron Collider [LHC] and looking ahead to the 2012 data — has finally been posted online, along with the rest of the presentations at the workshop. I wrote about the workshop, which took place in mid-March, here and here.  In the latter post, I wrote:

The workshop concluded with a panel discussion — the only point during the entire workshop when theorists were formally asked to say something. The panel consisted of Michael Peskin (senior statesman [and my Ph.D. advisor] famous for many reasons, including fundamental work on the implications of highly precise measurements ), Nima Arkani-Hamed (junior statesman, and famous for helping develop several revolutionary new ways of approaching the hierarchy problem),  Riccardo Rattazzi (also famous for conceptual advances in dealing with the hierarchy problem), Gavin Salam (famous for his work advancing the applications of the theory of quarks and gluons, including revolutionary methods for dealing with jets), and myself (famous for talking too much… though come to think of it, that was true of the whole panel, except Gavin.) And Raman Sundrum, one of the organizers (and famous for his collaboration with Lisa Randall in introducing “warped” extra dimensions, and also anomaly-mediated supersymmetry breaking [which was competitive with a paper by Rattazzi and his colleagues]) informally participated too. (more…)

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON May 4, 2012

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