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Seth Zenz | Imperial College London | UK

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The World’s Largest Detector?

Wednesday, August 13th, 2014

This morning, the @CERN_JOBS twitter feed tells us that the ATLAS experiment is the world’s largest detector:

CERN_JOBS Tweet Largest Detector

Weighing over 7,000 tons, 46 meters long, and 25 meters high, ATLAS is without a doubt the particle detector with the greatest volume ever built at a collider. I should point out, though, that my experiment, the Compact Muon Solenoid, is almost twice as heavy at over 12,000 tons:

CMS

CMS is smaller but heavier — which may be why we call it “compact.” What’s the difference? Well, it’s tough to tell from the pictures, in which CMS is open for tours and ATLAS is under construction, but the big difference is in the muon systems. CMS has short gaps between muon-detecting chambers, while ATLAS has a lot of space in order to allow muons to travel further and get a better measurement. That means that a lot of the volume of ATLAS is actually empty air! ATLAS folks often say that if you could somehow make it watertight, it would float; as a CMS member, I heartily recommend attempting to do this and seeing if it works. ;)

But the truth is that all this cross-LHC rivalry is small potatoes compared to another sort of detector: the ones that search for neutrinos require absolutely enormous volumes of material to get those ghostlike particles to interact even occasionally! For example, here’s IceCube:

"Icecube-architecture-diagram2009" by Nasa-verve - IceCube Science Team - Francis Halzen, Department of Physics, University of Wisconsin. Licensed under Creative Commons Attribution 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Icecube-architecture-diagram2009.PNG#mediaviewer/File:Icecube-architecture-diagram2009.PNG

Most of its detecting volume is actually antarctic ice! Does that count? If it does, there may be a far bigger detector still. To follow that story, check out this 2012 post by Michael Duvernois: The Largest Neutrino Detector.

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How Can We Hangout Better?

Wednesday, July 9th, 2014

Yesterday we had one of our regular Hangouts with CERN, live from ICHEP, at which we took questions from around the Internet and updated everyone on the latest results, live here at the ICEHP 2014 conference. You can see a replay here:

I sent it to my wife, like I usually do. (“Look, I’m on ‘TV’ again!”) And she told me something interesting: she didn’t really get too much out of it. As we discussed it, it became clear that that was because we really did try to give the latest news on different analyses from ICHEP. Although we (hopefully) kept the level of the discussion general, the importance of the different things we look for would be tough to follow unless you keep up with particle physics regularly. We do tend to get more viewers and more enthusiasm when the message is more general, and a lot of the questions we get are quite general as well. Sometimes it seems like we get “Do extra dimensions really exist?” almost every time we have a hangout. We don’t want to answer that every time!

So the question is: how do we provide you with an engaging discussion while also covering new ground? We want people who watch every hangout to learn something new, but people who haven’t probably would prefer to hear the most exciting and general stuff. The best answer I can come up with is that every hangout should have a balance of the basics with a few new details. But then, part of the fun of the hangouts is that they’re unscripted and have specialist guests who can report directly on what they’ve been doing, so we actually can’t balance anything too carefully.

So are we doing the best we can with a tough but interesting format? Should we organize our discussions and the questions we choose differently? Your suggestions are appreciated!

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My First Day at ICHEP (Again)

Thursday, July 3rd, 2014

ICHEPstartICHEP 2014 started today in Valencia, Spain. This is one of particle physics’s biggest conferences, held every two years. The last one, in 2012, coincided with the discovery of the Higgs boson. This year, we’re probably going to have more in the way of careful measurements than big new surprises. ATLAS and CMS have already released Higgs updates, and the pesky boson looks more and more like the Standard Model Higgs all the time.

This is the second ICHEP I’ve attended in person. I showed a poster at the first one, and wrote a blog post about it – which is a scary reminder of just how long I’ve been blogging. (I also still have my lanyard from that conference, which I’m wearing with my badge because it’s cooler than the boring black one we got this time.) This year, I’m here to give a parallel talk about the potential for even better measurements of the Higgs at the High-Luminosity LHC, which is a possible upgrade for the LHC that could take us well into the 2030s. By then, I suppose I should aspire to give an ICHEP plenary talk. ;)

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The Trees, the Forest, and Scientific Consensus

Tuesday, June 17th, 2014

I recently saw this comic from Twisted Doodles, which I think poses quite a conundrum for our usual simple picture of how science is studied and brought forth into the public:

From http://www.twisteddoodles.com/post/86414780702/working-in-science – used in this post with permission

From Twisted Doodles. Used in this post with permission.

If you are a non-scientist reading this blog, your idea of what science is for, and what it’s good for, is probably something like the left column – and in fact, I hope it is! But as someone who works day-to-day on understanding LHC data, I have a lot of sympathy with the right column. So how can they be reconciled?

Science takes hard work from a lot of people, and it’s an open process. Its ultimate goal is to produce a big picture understanding of a wide range of phenomena, which is what you’re reading about when you think all the good thoughts in the left-hand column. But that big picture is made of lots of individual pieces of work. For example, my colleagues and I worked for months and months on searching for the Higgs boson decaying to bottom quarks. We saw more bottom quarks than you would expect if the Higgs boson weren’t there, but not enough that we could be sure that we had seen any extra. So if you asked me, as an analyzer of detector data, if the Higgs boson existed, all I could say would be, “Well, we have a modest excess in this decay channel.” I might also have said, while I was working on it, “Wow, I’m tired, and I have lots of bugs in my code that still need to be fixed!” That’s the right-hand column.

The gap is bridged by something that’s sometimes called the scientific consensus, in which we put together all the analyses and conclude something like, “Yes, we found a Higgs boson!” There isn’t a single paper that proves it. Whatever our results, the fact that we’re sure we found something comes from the fact that ATLAS and CMS have independently produced the same discovery. The many bits of hard work come together to build a composite picture that we all agree on; the exhausted trees step back to take a broader perspective and see the happy forest.

So which is right? Both are, but not in the same way. The very specific results of individual papers don’t change unless there’s a mistake in them. But the way they’re interpreted can change over time; where once physicists were excited and puzzled by the discovery of new mesons, now we know they’re “just” different ways of putting quarks together.

So we expect the scientific consensus to change, it’s definitely not infallible, and any part of it can be challenged by new discoveries. But you might find that scientists like me are a bit impatient with casual, uninformed challenges to that consensus — it’s based, after all, on a lot of experts thinking and talking about all the evidence available. At the same time, scientific consensus can sometimes be muddled, and newspapers often present the latest tree as a whole new forest. Whether you are a scientist, or just read about science, keep in mind the difference between the forest and the trees. Try to understand which you’re reading about. And remember, ultimately, that the process of doing science is all the things in that comic, all at once.

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In Science, it’s OK to be Wrong

Monday, May 19th, 2014

It’s sort of a recurring theme for me, but a recent Washington Post article on the BICEP2 result, among others, has me wanting to repeat the idea, and keep it short and sweet:

Screen Shot 2014-05-18 at 8.15.54 PM

The issue at hand is whether BICEP2 has really observed the remnants of cosmic inflation, or if in fact they have misinterpreted their results or made a mistake in the corrections to their measurement. It’s frustrating that the normal process of the scientific method – that is, other experts reviewing a result, trying to reproduce it, and looking for holes – is being dramatized as “backlash.” But let’s not worry today about whether we can ever stop the “science news cycle” from being over-sensationalized, because we probably can’t. You and I can still remember a few simple things about science:

1. If scientists think they’ve found something, they should publish it. They should say what they think it means, even if they might be wrong.
2. Other researchers try to replicate the result, or find flaws with it. If flaws are found or it can’t be reproduced, the original scientists have to go back and figure out what’s going on. If other researchers find the same thing, it’s probably right. If lots of other researchers find the same thing, we can agree it’s almost certainly right and move on to the next level of questions.
3. Science makes progress when you say what you know and the certainty with which you know it. If everything you say is always right, you might be being too timid and delaying the process of other researchers building on your results!

But I think Big Bird says it best of all:

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On the Shoulders of…

Monday, April 14th, 2014

My first physics class wasn’t really a class at all. One of my 8th grade teachers noticed me carrying a copy of Kip Thorne’s Black Holes and Time Warps, and invited me to join a free-form book discussion group on physics and math that he was holding with a few older students. His name was Art — and we called him by his first name because I was attending, for want of a concise term that’s more precise, a “hippie” school. It had written evaluations instead of grades and as few tests as possible; it spent class time on student governance; and teachers could spend time on things like, well, discussing books with a few students without worrying about whether it was in the curriculum or on the tests. Art, who sadly passed some years ago, was perhaps best known for organizing the student cafe and its end-of-year trip, but he gave me a really great opportunity. I don’t remember learning anything too specific about physics from the book, or from the discussion group, but I remember being inspired by how wonderful and crazy the universe is.

My second physics class was combined physics and math, with Dan and Lewis. The idea was to put both subjects in context, and we spent a lot of time on working through how to approach problems that we didn’t know an equation for. The price of this was less time to learn the full breadth subjects; I didn’t really learn any electromagnetism in high school, for example.

When I switched to a new high school in 11th grade, the pace changed. There were a lot more things to learn, and a lot more tests. I memorized elements and compounds and reactions for chemistry. I learned calculus and studied a bit more physics on the side. In college, where the physics classes were broad and in depth at the same time, I needed to learn things fast and solve tricky problems too. By now, of course, I’ve learned all the physics I need to know — which is largely knowing who to ask or which books to look in for the things I need but don’t remember.

There are a lot of ways to run schools and to run classes. I really value knowledge, and I think it’s crucial in certain parts of your education to really buckle down and learn the facts and details. I’ve also seen the tremendous worth of taking the time to think about how you solve problems and why they’re interesting to solve in the first place. I’m not a high school teacher, so I don’t think I can tell the professionals how to balance all of those goods, which do sometimes conflict. What I’m sure of, though, is that enthusiasm, attention, and hard work from teachers is a key to success no matter what is being taught. The success of every physicist you will ever see on Quantum Diaries is built on the shoulders of the many people who took the time to teach and inspire them when they were young.

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My Week as a Real Scientist

Thursday, March 6th, 2014

For a week at the end of January, I was a real scientist. Actually, I’m always a real scientist, but only for that week was I tweeting from the @realscientists Twitter account, which has a new scientist each week typing about his or her life and work. I tweeted a lot. I tweeted about the conference I was at. I tweeted about the philosophy of science and religion. I tweeted about how my wife, @CuratorPolly, wasn’t a big fan of me being called the “curator” of the account for the week. I tweeted about airplanes and very possibly bagels. But most of all I tweeted the answers to questions about particle physics and the LHC.

Real Scientists wrote posts for the start and end of my week, and all my tweets for the week are at this Storify page. My regular twitter account, by the way, is @sethzenz.

I was surprised by how many questions people had when I they were told that a real physicist at a relatively high-profile Twitter account was open for questions. A lot of the questions had answers that can already be found, often right here on Quantum Diaries! It got me thinking a bit about different ways to communicate to the public about physics. People really seem to value personal interaction, rather than just looking things up, and they interact a lot with an account that they know is tweeting in “real time.” (I almost never do a tweet per minute with my regular account, because I assume it will annoy people, but it’s what people expect stylistically from the @realscientists account.) So maybe we should do special tweet sessions from one of the CERN-related accounts, like @CMSexperiment, where we get four physicists around one computer for an hour and answer questions. (A lot of museums did a similar thing with #AskACurator day last September.) We’ve also discussed the possibility of doing a AMA on Reddit. And the Hangout with CERN series will be starting again soon!

But while you’re waiting for all that, let me tell you a secret: there are lots of physicists on Twitter. (Lists here and here and here, four-part Symmetry Magazine series here and here and here and here.) And I can’t speak for everyone, but an awful lot of us would answer questions if you had any. Anytime. No special events. Just because we like talking about our work. So leave us comments. Tweet at us. Your odds of getting an answer are pretty good.

In other news, Real Scientists is a finalist for the Shorty Award for social media’s best science. We’ll have to wait and see how they — we? — do in a head-to-head matchup with giants like NASA and Neil deGrasse Tyson. But I think it’s clear that people value hearing directly from researchers, and social media seems to give us more and more ways to communicate every year.

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Which is the Real CERN?

Thursday, December 19th, 2013

Is this CERN...?

Is this CERN…?

Or is this CERN...?

Or is this CERN…?

A few weeks ago, at the very real peril of spending our weekend on something that was a little like work for both of us, I went with my wife to the Collider exhibit at the Science Museum in London.

Collider a detailed, immersive exhibit about the Large Hadron Collider and the people who work on it. It’s amazing to hear video interviews from real physicists and see real places at CERN reproduced. A lot of the information is on realistic-looking whiteboards, and there’s real stuff lying everywhere just like in real offices. (The real stuff is glued and stapled down; my wife, a museum curator interested in the implementation of the exhibit, checked that detail personally.) One thing that bothered me that might not bother you: the videotaped physicists are clearly actors, with stories told just a bit too dramatically. One thing that might bother you but didn’t bother me, because I can skip reading signage and just explain to my wife what I think it should say: not all of the amazing things you could see are explained very well.

But the fun part really is the feeling of actually being in the midst of where the science is done. For example, at right, you can see a picture of me in one of the CERN hallways recreated for the exhibit, and you can see a picture of me in front of the real version of the same office. But which is which?

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The Higgs, Particle Physics, and How Science Works

Friday, October 25th, 2013

Last week, I was in Arlington, Virginia to give a talk at a cybersecurity research workshop called LASER 2013.  Why did they want to hear a particle physicist speak?  Well, this particular workshop is focused on “properly conducted experimental (cyber) security research,” so they want to hear from people in other fields about how we run experiments, publish the results, and think about science in general.  So I gave a talk, slightly over an hour long, that used the Higgs boson to illustrate the giant experiments we do at the LHC, the social organization required to do them, and their results.  I said a lot of things here that you don’t normally say explicitly as part of a particle physics conference, and I also heard what sort of experiments one can do in cybersecurity research.  We had some very interesting discussions about how experimentation and data analysis really work, and I really appreciate the opportunity I had to participate in the workshop.

You can watch my whole talk here, and I would definitely appreciate your feedback:

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Women at CERN: A Professional Perspective

Monday, October 14th, 2013

Can you think of anything that all the men who won the Nobel Prizes in science this year have in common? I’ll give you a hint: the answer is already in the question. In fact, out of 195 people awarded the Nobel Prize in Physics since 1901, only two have been women: Marie Curie in 1901 and Maria Goeppert Mayer in 1963.

I have been thinking quite a bit about the status of women in science and what we say about it lately, ever since reading the most recent posts on the subject here on Quantum Diaries. Both were written by James Doherty: “Girls, at CERN – loads of ’em!” and “Five Lessons from a Summer at CERN” (formerly titled, in part, “Italians are Hot,” and still with a subsection by that name). I think it should become clear that I don’t approve of James’s tone in some places, although I understand that he was aiming to convey his experience as a summer student in “an open, honest and light-hearted way.” At the same time, Quantum Diaries is a place for voices from the physics community: writers here usually don’t speak for anyone, but we are supposed to be representative. So, if we are going to talk about the issues faced by women in physics, we also need voices from professional particle physicists, who have thought and learned a bit about where gender inequalities arise and their implications for our field. In that spirit, let me put forward my viewpoint, along with links to many other views I’ve found educational; I’m sorry to say that from my perspective there’s a bit less to be light-hearted about.

Particle physics is my job. I come to CERN every day and work with my colleagues to learn more about the universe. Some of my colleagues are women. Some are men. Some are Italian. Who they are, how they look, or what they’re wearing cannot be my foremost concerns. If I don’t look all of my colleagues in the eye and listen to what they’re saying, then I am doing poorly at my job. I’m likely to suffer for it later, because whoever I didn’t listen to probably said something I need to know. The starting point is to treat everyone professionally and with respect.

Easy enough to agree with so far; I think almost everyone would. The problem is that, well, we still have a problem. As Pauline Gagnon wrote here last year, more and more women are joining our field, but they are still greatly underrepresented. Unless you believe that women are inherently bad at physics – and there are pretty straightforward reasons to believe that that can’t possibly be causing the imbalance – then something is going wrong somewhere. A lot of excellent potential physicists are deciding against physics as a career at one stage or another, or perhaps never learning about it in the first place, or are even being pushed or nudged out by sexism. Anywhere we lose potential colleagues makes our work poorer.

Where is it going wrong, and what can we do about it? Well, my experience actually isn’t very informative. I have never seen an example of deliberate ill-will toward female participation in physics, and indeed I’ve only recognized a few situations that were even accidentally awkward. But bias can be unconscious and difficult to recognize. As a scientist, I know two things:

1. Just because I’ve never seen something, that doesn’t mean it doesn’t exist.
2. I can read what other people have written to learn about stuff.

So here are some articles and blogs I have found enlightening, in particular on the question of what actions we can take as scientists to help bring about more even participation by women:

The literature on women in science, technology, engineering, and math is enormous, and I’m very far from knowing all of it well. Do you have a favorite article or study, especially on what we as scientists can do better? Post the link and I’ll add it below.

Update, Oct 16: Some suggested links (thanks, Ben, Sarah, and Ken!):

Update, Oct 21 (thanks, Marga!): http://www.newyorker.com/online/blogs/elements/2013/10/a-ripple-of-voices-against-sexism.html

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