I hope you’re all ready for today’s transit of Venus across the face of the Sun. You certainly can’t have missed that it’s happening, given the media hype. (Look at the website http://transitofvenus.nl/wp/, their post from yesterday in particular, for all sorts of useful resources, including timing for the event in various locations, and on-line resources for you to watch in case clouds interfere at your location. UPDATE: that website is overwhelmed. In the continental U.S. transit begins just after 6 pm Eastern, 3 pm Pacific, differing by a few minutes from place to place; and sunset will occur before the transit is over. One online location to watch the transit is http://events.slooh.com/) But — let me be the first to warn you — this is going to be very cool, but it isn’t going to be a spectacular event like a big meteor shower or a total solar eclipse or even a total lunar eclipse. It’s going to be subtle, slow, and potentially very boring, unless you have the right mindset (or a truly excellent telescope, properly filtered for sun viewing). So here are some suggestions: (more…)
Author: Matt Strassler
A reminder that the transit of Venus across the Sun will be visible a little over 24 hours from now (starting before sunset June 5th in the United States.) It’s the last of your lifetime, so make your plans now. Weather forecast across much of the eastern U.S. is pretty bad, I’m afraid. Of course there will be many places to watch on-line. For more information, I highly recommend http://transitofvenus.nl/wp/ . Also, though you and I can’t see Venus right now (too close to the Sun), the SOHO satellite can: click here for the latest photo, updated frequently, which shows the sun (at center, blocked out) and the sun’s corona around it, and a white dot approaching the sun, which is Venus (ignore the white horizontal lines, which are an imagining artifact).
The transit of Venus was used, historically, to figure out how big is the solar system (the sun and the planets). As I’ll explain tomorrow, it wasn’t that hard to figure out how large are the distances between the sun and the planets relative to one another, but getting the overall scale — the absolute distances — was a much harder problem. The first measurement accurate to a couple of percent came from the transits of Venus in the 1760s. I’ll explain (roughly) how this works tomorrow; the technique relies on the principle of parallax, a principle which lies behind our own ability to perceive depth, and is used by astronomers to measure distances to (relatively nearby) stars.
[Reminder: two events coming up in which I’ll be speaking: (more…)
POSTED BY Matt Strassler
ON June 4, 2012
A brief mention today of a new measurement from the BABAR experimental collaboration, which tests lepton universality (to be explained below) and finds it wanting.
The Basic Story (Slightly Oversimplified)
Within the Standard Model of particle physics (the equations that describe and predict the behavior of all of the known particles and forces), the effects of the weak nuclear force on the three leptons — the electron, the muon and the tau — are all expected to be identical. This called “lepton universality”. (more…)
POSTED BY Matt Strassler
ON June 1, 2012
For those of you curious about why posts have been a little sparse this month and have been wondering what I’ve been up to, here’s the latest on what has been an on-going story.
The Large Hadron Collider [LHC] is producing lots of new data, and the search for the Higgs particle continues at the ATLAS and CMS experiments. We’re still within Phase 1 of the search for the Higgs particle (I’ve described the two main phases here and in more detail here) in which the experiments are trying to discover unequivocally, or exclude unequivocally, the simplest possible form of the Higgs particle, which is called the Standard Model Higgs. Phase 1 is well along the way, the experimenters having excluded a Standard Model Higgs particle at any mass except a small range around 125 GeV/c2. Within that range there are hints that a Higgs particle might be showing up (see here, here, here and here). Some would say the evidence is significant and are quite convinced already, while others (quite a few of the experimentalists, and a few cautious theorists such as myself) would say the hints are not yet especially significant and are willing to let more data settle the issue. But everyone agrees there’s a very high chance the issue will be settled in 2012.
At that point, the Higgs search will move toward Phase 2. In fact, in some sense it is already in transition, because either there is a Standard Model Higgs particle with a mass near 125 GeV/c2, or the Higgs particle, if it exists, must be more exotic and complicated — two possibilities on which we can focus our planning.
One of the most important questions that will be asked (and is already being asked) is whether the particle that is showing up in the 2011 data (if it is really there in the first place) is a Standard Model Higgs or a look-alike Higgs particle that is actually more complicated in some way. (more…)
POSTED BY Matt Strassler
ON May 30, 2012
[Here we go: the first in the promised “structure of matter” series, which will trickle out over the coming weeks…]
In any of the world’s great libraries, the rooms and shelves of books stretch on seemingly without end. The tomes in the United States’ Library of Congress number in the tens of millions. Each of them presents a distinct story, or a detailed analysis, or a historical document, with its own individual meaning. Yet these millions of books written in the English language are constructed from a mere few tens of thousands of words, and each of these words is formed from a combination of just 26 letters — the letters A through Z.
Meanwhile, we live surrounded by a vast and astonishing diversity of materials — not the least fantastic of which are the many types of biological structures that make up our own bodies and those of all other animals, plants, and other living creatures. The planet on which we live is made from all sorts of rocks, some hard and brittle, some malleable, of many colors and textures. In addition to water we encounter alcohols, acids, sugars and oils of various forms. The food cooking on our stoves produces all sorts of aromas for us to inhale, floating amid the air we breathe. To salts and chalks and alloys, we must add new, synthetic materials, such as the many types of plastics. But it is important to remember that the vast contents of this Library of Materials are all constructed from a smaller (though still very large) assortment of molecules, themselves formed from a mere 100 or so atoms — the elements H through U (hydrogen through uranium, and beyond).
The complexity of a written language like English rests on words, and the complexity of materials begins with molecules. Click here to read more.
POSTED BY Matt Strassler
ON May 29, 2012
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.)
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:
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:
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!]
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…)
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.
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.]
POSTED BY Matt Strassler
ON May 8, 2012
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