steuard: (physics)
Monday, March 17th, 2014 06:26 pm

So that physics announcement that I posted the rumors about happened, and it was indeed just as big of a deal as rumor had made it. Here are a few links I've found that summarize the results nicely:

This is really cool, and there are some neat, neat implications. (The data points to an energy scale for inflation that happens to be very close to the expected energy scale of grand unification of fundamental forces in simple supersymmetric models of particle physics, for instance.) It'll be great to see if this result holds up.

steuard: (physics)
Monday, March 17th, 2014 12:11 am
If you happen to be the sort to follow a few cosmologists on blogs or social media, you've probably seen rumors swirling around like mad for the past few days. I'm not sure if this was triggered by the Harvard press release promising that a "major discovery" in astrophysics would be announced Monday at noon, or whether that release was hurried out the door only after the rumors got out. But it sounds like it could be a Big Deal, so keep your eyes open tomorrow. (One rumor is that they've invited Guth and Linde, the first theorists to propose cosmic inflation, to attend the announcement.)

Probably the best description I've seen of what people think the press conference is going to be about came from my friend Sean Carroll at Caltech: it seems that an experimental group observing the Cosmic Microwave Background is going to announce that they have seen direct evidence of perturbations of that background caused by gravitational waves in the first instants of the Big Bang. (As Sean explains, today our direct experimental data on the early universe extends back to about one second after the start of the Big Bang. This observation would push that back to an astounding 10-35 seconds after the start.)

I won't try to explain the physics here, since it's really not my specialty. The intriguing thing is that, as far as I can tell, most people were not expecting to see any actual detection of this signal from the current generation of experiments: other data suggested that the current experiments would only be able to set "less than this threshold" sorts of limits. So this impending announcement would seem to imply one of four things: 1) The signal is much stronger than expected, which would be Very Exciting(TM) for physics, 2) The experiment turned out to be more sensitive than expected, which would presumably involve either really good luck or some neat improvements in data analysis algorithms, 3) The announcement is merely of strongly suggestive evidence rather than a true discovery-level result, which would make the "major discovery" press conference seem quite overblown, or 4) Someone messed up their analysis and/or got fooled by a statistical fluctuation, which after all this hoopla would probably wind up ending multiple careers. (I can guarantee that the experimental team here is painfully aware of all these possibilities. But then, so were the folks who claimed to have seen neutrinos moving faster than light a few years back.)

So yeah. It sounds like the actual science talk will begin at 10:45 (with papers and data going online at the same time). So watch the news, or at least the blogs! It should be exciting.
steuard: (physics)
Monday, August 6th, 2012 01:12 pm
This is an absolutely stunning image: the Curiosity rover spotted while descending to the Martian surface, dangling under its parachute. It took some tremendously careful calculations by the Mars Reconnaissance Orbiter team (and some good luck) to snap this shot of a fast-moving object in the few moments available (they had to aim the camera in advance, tell it when to take the shot, and hope). The Bad Astronomer gives a bit more detail. (Click the image for a larger version.)

(Image via NASA/JPL/University of Arizona )

I honestly yelped out loud with glee when this image showed up on my screen. (Good thing my office door was closed.)

I'm still in awe that this insanely complicated landing scheme worked; for once, the reality of space exploration turned out to be just as awesome as what science fiction promised us fifty years ago. I mean, heat shields and parachutes are old hat, sure, but to follow those up by setting the one-ton rover gently on the ground using a crane suspended from a hovering rocket platform? That's just crazy talk. (Here's a nice video summary, for those just catching up.) And it worked. IT WORKED. (Sorry... I seem to have something in my eye.) Now we get to find out what remarkable science we can do.

EDIT: For those who aren't following all this on their own, a couple of followups. First, it turns out that the same (large) image by the MRO also includes the heat shield that had separated from Curiosity a minute earlier, still falling toward the ground. And second, there's already a rough video of the landing as seen from a camera on the bottom of Curiosity itself. (It sounds like they'll eventually have the whole thing in high definition, too!) This just keeps getting cooler.
steuard: (Default)
Sunday, July 15th, 2012 11:31 am
Charged particles released after the big solar flare last week have been reaching the Earth all weekend, and there's a good chance of an impressive aurora tonight! (I probably ought to have said something yesterday...) There's a good Aurora Forecast page from the University of Alaska that will show you what to expect where. In fact, if it weren't sunny right now, their Short Term forecast map seems to imply that auroral activity would likely be happening right over Michigan (and Montana and Maine and possibly even farther south than that) and that it might even be visible on the horizon as far south as New Orleans. Who knows whether it will be anything like that tonight, but try to have a look!
steuard: (physics)
Wednesday, July 4th, 2012 11:58 am
The rumors were true! Both experiments at the LHC that were searching for the Higgs announced discovery-level evidence early this morning. This is a Big Deal, even if we did pretty much expect that the LHC would produce a result like this eventually. There's a lot to say (and lots of good discussions out there at various technical levels), but for a nice layman's overview I might recommend Bad Astronomy's Higgs post. The quotes near the beginning of this post by Tommaso Dorigo are good, too.

The very short version is this: a new particle has most definitely been discovered, and CERN found it by looking in all the places that one would look for the Higgs. Its properties aren't nailed down very well yet, but they appear to be broadly consistent with the properties we expect for the Standard Model Higgs. But, enticingly, there are tentative hints of some differences from that expectation, too. Further data over the next few years will (we hope) show us whether those differences are just random noise in the detection system or whether they reflect entirely new physics. (Most of us really, really hope it's the latter.)

Edit: I've seen some folks linking to a nice video explaining the Higgs from PhD Comics a couple of months ago. Also, since the topic of Comic Sans came up in my blog last week, I'm sad to see that the things I grumbled about last December were still a problem for the real announcement.

Edit2: Strassler's post lists a few more specifics in a nice, clean way.
steuard: (physics)
Tuesday, July 3rd, 2012 11:04 pm
Wednesday may prove to be a very exciting day in physics: the two LHC teams searching for the Higgs boson are scheduled to give a seminar, and pretty much the entire particle physics community expects their announcement to amount to a discovery (though either experiment on its own may or may not pass the official threshold this time). This is a Big Deal: finding the Higgs was one of the primary goals of the LHC (perhaps the primary goal), and it's the very last piece of the Standard Model of particle physics whose existence has not yet been confirmed. These groups presented some very tantalizing evidence last December, but now that they've taken more data we may finally be there for real.

The really interesting thing to watch for in this announcement is whether the particle they're seeing seems to behave exactly as the Standard Model predicts, or whether its interactions are different in some subtle way. Most of us really, really hope that there are differences, because the behavior of the Higgs is sensitive to many types of "new physics": it could give us the first fundamentally new experimental evidence about the ultimate laws of nature that we've had in a decade (or maybe even three decades or more, depending on what you count as "new" and how narrowly you focus on particle physics). Nobody expects tomorrow's announcement to make solid claims about any of that: it will take years of data to really start to understand the details. But December's data seemed to have weak hints of something unexpected, so people will be watching carefully to see whether those hints get stronger or whether they fade away as the statistics improve.

I'll presumably post something all excited in the morning. But if you're interested, keep an eye on Cosmic Variance or your favorite particle physics blog for news. The seminar is at 9am in Geneva, so that's 3am Eastern. I expect to be envious of everyone on the west coast who gets to see the results live at midnight!
steuard: (Default)
Monday, June 4th, 2012 06:48 pm
Tomorrow (Tuesday, June 5) starting at about 6:04 Eastern time, the planet Venus will pass directly between the Earth and the Sun. This is a Rare Thing: the next time will be in 2117. There's been a lot of good science done using these transits in the past (like the first good estimates of the size of the solar system) and they still provide neat science opportunities today (like the plan to refine exoplanet detection by looking at the moon that I wrote about previously).

So look around locally for a chance to view the transit in person! Lots of observatories and planetariums and other groups will be organizing viewing events, which is probably your best bet. If you want to view it yourself, you can look at the official Transit of Venus site for some suggestions. (Don't look directly at the sun! Don't point an ordinary telescope at the sun!) Or look for some of the many webcasts out there: the Bad Astronomy site is planning what sounds like a good one, and there are others from NASA and other places. But you should really try to have a look: it won't look awe inspiring, but watching this sort of thing as it happens and thinking about the vast celestial objects in play can inspire great thoughts on astronomy and our place in the universe. Good stuff!
steuard: (physics)
Wednesday, March 7th, 2012 09:24 am
Last December, the LHC experiments from CERN looking for the Higgs boson announced some pretty promising evidence that they had started to see it, and had measured its mass-energy at about 125 GeV. It wasn't clear enough to claim a true "discovery" yet, but it was promising. Today, scientists from Fermilab presented analysis of some of the last data collected before the Tevatron shut down (along with some improved analysis of their years of previous data), and they found evidence consistent with what the LHC saw. It's not as strong as the LHC signal was, but that's expected because their accelerator isn't as powerful. But the fact that two entirely separate machines have produced results that agree is an awfully good sign that this is the real thing. If you want to read some details, I heard about this from blog posts here and here.

The worrisome thing right now is that we're awfully close to the "nightmare" scenario for data from the LHC: finding the Higgs but not finding any evidence at all of physics beyond the Standard Model. All of the searches for things like extra dimensions and supersymmetry have thus far found nothing, even though the most natural supersymmetry models would quite likely have started to give strong hints by now. (Those ideas all have lots of variations and thus aren't remotely close to being ruled out yet, but it's getting harder to believe in the variations that got people excited about them in the first place.) If we find the Higgs, then that means the Standard Model is complete and internally consistent... as far as it goes. But we also know that the Standard Model can't be the whole story: its math simply isn't capable of being a "final" theory of nature. (For example, on its own it predicts effects that would make us measure the Higgs mass to be infinite! And of course it's ultimately incapable of coexisting with a universe that contains gravity, but that's true of any quantum field theory.) So it would be Really Unpleasant to have (on some level) finished studying the particle physics that we've already known for thirty years without the slightest hint of what the next step ought to be.

But still: finding the Higgs is really exciting, and there's plenty of time to worry about future prospects later.
steuard: (Default)
Tuesday, December 13th, 2011 04:20 pm
I have a final to finish writing, but I wanted to share a quick summary of the Higgs news from this morning (for those of you who care but somehow haven't seen it yet). You can read Sean Carroll's summary for a few more details (and links to lots of posts with more detailed commentary), but my take on the talks boils down to this:

  1. The current LHC data makes it look awfully likely that the Higgs boson exists and has a mass (energy) of about 125GeV. Similarly strong evidence has appeared and then proven to be statistical noise in the past, but the agreement between two experiments and the strong expectation that the Higgs ought to exist somewhere in the ever-shrinking viable mass range make this time seem more promising.

  2. The data from the CMS experiment seems more thoroughly analyzed, and its result (considered alone) is real but weak enough that I would hardly have paid attention to it. The data from the ATLAS experiment is perhaps less complete, but it shows a clearer signal. The two signals don't quite line up at the same mass, which could be a bad sign, but they're awfully close to being consistent with each other.

  3. If the LHC runs as planned, we should have a definitive discovery or exclusion of the Standard Model Higgs boson by the end of 2012, and quite possibly as early as next summer.

  4. CERN needs a better video streaming server, and physicists in general might possibly benefit from lessons on how to create good presentation slides. (The number of groans about Comic Sans on Twitter was impressive, but I thought the real issue was that a lot of the slides felt cluttered. To be fair, they were trying to convey a lot of information to a highly expert audience.) Also, the term "God particle" should be immediately banned from public discourse.
steuard: (Default)
Monday, August 8th, 2011 02:38 pm
My name (including its weird spelling) has been in my family for generations. My father is Walter Steuard Jensen, Jr., son of Walter Steuard Jensen, son of Walter ??? Jensen, son of Steuard Raun Jensen who came to America from Denmark as a teenager. The source of that name has always been a bit of a puzzle, but we've had no way of tracing it further back because the family lost track of its Danish relatives (even their names) years ago. That's always left me a little sad: I've enjoyed connecting with my mother's distant cousins in Sweden, and it would be nice to have something like that on my father's side.

Flash forward to my mother's visit last week. In cleaning out old boxes, she found a letter from one Niels Jensen to his brother in America. The letter talked about all of the surviving siblings back in Denmark (including full names), and a bit of Google searching eventually led me to a definitive match: the family of Rasmus August Jensen (translated here from Danish).

If you look at that list of children, you'll see that there's a distinct lack of Steuards there (by any spelling). But there is a "Søren Ravn Jensen", and a comment in the letter seems to confirm that that was my great-great-grandfather's given name. So apparently I ought to be named Søren! My new theory is that Søren decided at some point that he wanted a more American-sounding name, but when he chose one he wasn't clear on how to spell it. We'll see if this takes us anywhere in the future; it would be fun to see if we could track down any living cousins back in Denmark.
steuard: (strings)
Sunday, June 19th, 2011 12:11 pm
Just in time to avoid delays due to childbirth, I've finished and submitted a new paper for publication: The KK-Monopole/NS5-Brane in Doubled Geometry. I'm excited about this work; it's the same topic that I presented on a couple of months ago at the Great Lakes Strings conference in Chicago. Since the title is once again largely jargon, I've written up a summary of what it's all about for non-specialists. To be honest, I have no idea how much sense that summary will make anyway, so let me know if you think it's unreadable. I hope you at least like the pretty pictures there!

[Oh, and I've also replaced my user icon with something that looks a little more obviously like strings: strings interacting with D2-branes, to be exact. It's one of my more popular string images out in the wild, and hey, it's pretty, too.]
steuard: (physics)
Tuesday, May 31st, 2011 05:11 pm
It's been a long, long time since I wrote anything here: I've just finished teaching an intensive one month "Spring Term" class on Medical Physics that met two to three hours a day, five days a week. This might have been less stressful if I'd ever taught (or taken) a class on the subject before (or if I hadn't spent the whole week between my previous final exams and the class starting writing and giving a conference talk in Chicago). But it seems to have gone well, and I've now officially hit summer vacation! That means that I get to procrastinate on baby preparation and paper writing by sharing cool recent science tidbits.

The first is serious physics, and has the potential to be tremendously exciting if it pans out: the CDF experiment at Fermilab may have found the first direct evidence of physics beyond the Standard Model of particle physics! For a nice layman's summary, my friend Sean Carroll has a good writeup at Cosmic Variance; for some more detail, follow the links to posts at Résonaances. I won't try to repeat them here; I'll just show the exciting data:

and comment that the red line is the expected Standard Model result and the blue bump above would presumably correspond to an entirely new neutral particle about 150 times heavier than a proton. This result still isn't 100% solid: it's a "4.8 sigma" result, which is extraordinarily unlikely to happen by chance, but until it's reproduced by Fermilab's D0 experiment or by the LHC there's always the chance that someone forgot to carry a two during the data analysis.

The second thing to share is a beautiful time-lapse video of the Earth rotating under the stars that was recently adapted from an earlier video of stars rotating in the sky. It's a vivid demonstration of the Earth's motion through the heavens that makes you rethink your assumptions about what's really moving when you watch the sky. Here's the video; seriously consider watching it full-screen in HD!
steuard: (Default)
Wednesday, May 20th, 2009 11:42 pm
I don't think I'm excessively nervous around spiders. Sure, I tend to react poorly if they're actually on my body, and I'm not eager to share my living space with big ones. But in general I think spiders and their webs are pretty cool. Relatively few are dangerous, so there's no reason to be paranoid about them. In fact, I've never been near a dangerous spider that wasn't in a cage.

Or so I'd assumed. A student mentioned last week that some Scripps dorms have black widow spiders in their basements. Still, I've never spent much time in the Scripps dorms: no worries. But then another student commented that you could sometimes see them around the steps of our science building. So, ok, they're around, but it's not as if they're a visible presence.

But no. Coming back from lunch today, another faculty member pointed out a big web made by a black widow. Three feet from where I park my bike. This suddenly casts the small webs I've found on my bike itself from time to time in a whole new light.
steuard: (Default)
Monday, May 18th, 2009 09:41 am
The stairs up to our apartment double as a doorbell: the apartment shakes a little when people come to the door. So when I felt them shaking last night, I thought "Kim's home!" I jumped up to get the door for her, but when I looked outside there was nobody there (false alarms aren't entirely uncommon). I'd obviously been a bit too vigorous as I headed to the door, too: the TV was still rattling a little from where I'd run by. "Boy," I thought, "I really have to be more considerate of the people downstairs: they might have thought there was an earthquake!"

Kim assures me that despite mistaking an actual earthquake for her, I don't deserve to be slapped.
steuard: (Default)
Tuesday, July 29th, 2008 02:30 pm
I just had my first real earthquake! Sure, on a couple of occasions I've felt a quick jolt around the house, but never enough to even be completely sure it was actually a quake. No doubts about this one, though. While my first thought was "What did they drop upstairs this time?", I quickly realized that the rumbling and shaking was stronger and longer lasting than the usual bumps from the lab above, and I scrambled under my desk just as the ripples hit. (Thanks to my Fields and Waves class at Harvey Mudd, I know pretty precisely what was going on at each stage of the way.)

It didn't last long, and it didn't seem like anything disastrous had happened, but we were evacuated from the college buildings as a precaution. I'm obviously new at this (and I may have been more flustered than I thought), because I didn't think to grab my bag lunch off of my desk (it was almost noon) and or even to close my door behind me (we've got laptops in here). Fortunately, someone else closed it for me, and they let us back in before I got too hungry. All in all, it made for a more interesting day, and happily it sounds like there weren't any serious injuries anywhere (one news story commented that a couple of people had minor head injuries from taking cover under tables). If you want all the latest California earthquake news, I highly recommend this USGS site.