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Trickle Down Science [Uncertain Principles]

Science Blogs Physcial Sciences - 2 May, 2012 - 20:53

A week or so ago, lots of people were linking to this New York Review of Books article by Steven Weinberg on "The Crisis of Big Science," looking back over the last few decades of, well, big science. It's somewhat dejected survey of whopping huge experiments, and the increasing difficulty of getting them funded, including a good deal of bitterness over the cancellation of the Superconducting Supercollider almost twenty years ago. This isn't particularly new for Weinberg-- back at the APS's Centennial Meeting in Atlanta in 1999, he gave a big lecture where he spent a bunch of time fulminating about what idiots politicians were for cancelling the project. If anything, the last decade and a bit has mellowed him somewhat.

Sort of in parallel with this, I've also been reading Neil deGrasse Tyson's latest book, Space Chronicles (I say "sort of" because I actually stopped reading it for a couple of weeks, because I found it maddening for reasons that I may go into in another post). This is a collection of things from other sources that collectively sort of advances the argument that we need to spend flipping great wodges of cash on space exploration, for the good of science and society as a whole.

While these aren't directly related to each other-- and, indeed, are somewhat in conflict, as Weinberg has no use for manned space flight-- they're both making a similar argument: that we should be spending money on Big Science projects, because they're important for science as a whole. Which is fine, to a point-- I'm all in favor of increasing the amount of money we spend on scientific research-- but I can't help thinking that it's awfully easy to make this argument when the Big Science projects just happen to fall very close to your area of interest.

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Categories: Education

Clock Synchronization Done Right: "A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th Decimal Place" [Uncertain Principles]

Science Blogs Physcial Sciences - 2 May, 2012 - 17:05

I've been busily working on something new, but I'm beginning to think I've been letting the perfect be the enemy of the good-enough-for-this-stage, so I'm setting it aside for a bit, and trying to get caught up with some of the huge number of things that have been slipping. Which includes getting the oil changed in my car, hence, I'm sitting in B&N killing time, which is a good excuse to do some ResearchBlogging.

ResearchBlogging.orgLast week was a banner week for my corner of physics, with three really cool experiments published. Two of those are on the arxiv, which means I can use images from the paper (but those take longer to write). The third was in Science and isn't available in preprint form, and since the AAAS are bastards about permissions, and I'm not paying them $30 for the sake of a blog post, we'll do that one first.

The paper in question has the incredibly sexy title "A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th Decimal Place", and got a pretty good write-up in Physics World, but there's still room for some Q&A:

Seriously? Optical fibers and frequency metrology? What do those even mean? Seriously. This is a significant advance for people who care about precision measurement of time. The authors took two ultra-precise atomic clocks in labs at opposite ends of Germany, and were able to compare their frequencies at the level of a few parts in 1019. That's 0.0000000000000000004 times the original frequency, or, since they started with an optical frequency, 0.00008Hz out of 194,000,000,000,000.

OK, I admit, that's a lot of zeroes. But why does that matter? Isn't the whole point of ultra-precise atomic clocks that they all work exactly the same way? Why do you need to compare them? All atomic clocks using a given type of atom have the same basic frequency, but not all clocks are equally well made. The only way to determine the performance of a new one is to compare it to one you know works, but they're also not very portable, so you need to be able to do the comparison remotely.

There's also the fact that the local conditions for different clocks will be different, which can lead to some small shifts in the frequency due to things like general relativity, which means you can study some interesting physics using a distributed network of clocks. You can also check to see if the constants of nature are changing by comparing clocks based on different atoms, and again, these are not easy to make or move around, so being able to reliably do the comparison over long distances is a bug deal.

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Categories: Education

You're not from around here, are you? [Starts With A Bang]

Science Blogs Physcial Sciences - 2 May, 2012 - 02:35

"A journey is a person in itself; no two are alike. And all plans, safeguards, policing, and coercion are fruitless. We find that after years of struggle that we do not take a trip; a trip takes us." -John Steinbeck Here on Earth, we all get to enjoy the delight of being located in an extremely fortuitous place in our Solar System. Not just today, mind you, but billions of years ago, when the Solar System's planets were first forming!


(Image credit: NASA / JPL-Caltech, retrieved from Jodrell Bank CfA.)

Located close enough to our Sun, when the Earth first formed, like our neighbors Mercury, Venus and Mars, we were chock full of heavy elements. Not just the carbons, nitrogens and oxygens that abound on all the known worlds, but important ones much higher up on the periodic table, including silicon, sulphur, iron, nickel, tin, lead, and even the radioactive uranium!

This might not sound so special to you, but our world would be a lot more boring if we had formed farther from the Sun. See for yourself:


(Image credit: Russ Meyer, using data from NASA.)

Jupiter and Saturn aren't simply less dense than Earth is because they retained all that excess hydrogen that our wimpy gravitational field couldn't hold. Although that's true, they're also made out of elements that are intrinsically less dense!

We can identify where an object found anywhere in the Solar System -- including meteorites that fall to Earth -- simply by examining what they're made out of.


(Image credit: NASA, retrieved from National Geographic.)

One of the most spectacular applications of this knowledge came when we first journeyed to the Moon. For the first time, we'd be able to analyze rocks from the Moon and their chemical composition! What we found was simultaneously profound and the most boring thing imaginable.


(Image credit: NASA / Apollo 11, retrieved from here.)

Because the Moon is made out of the same stuff that the Earth is!

Before you start saying, "Duhhhhh," as some of you are wont to do, let's remember that it didn't have to be this way. We need only look at our nearest moon-ed neighbor.


(Image credit: Johannes Schedler / Panther Observatory, retrieved here.)

Because Mars' two moons, Phobos and Deimos, are not made out of the same stuff Mars is! They formed significantly farther out in the Solar System, originating in the asteroid belt. Only a chance encounter with another body (probably Jupiter) flung them in to the inner Solar System, where they were gravitationally captured by the red planet!

If it happens for Mars from the asteroid belt, you may be wondering about that other, even bigger belt in our Solar System, and what the possibilities might be from there.


(Image credit: Don Dixon / Cosmographica.)

I refer, of course, to the Kuiper Belt, the band of leftover proto-planetesimals from the formation of our Solar System. These small, icy objects are only about a third the density of Earth, but are more dense than the gas giants that lie interior to them.

If the asteroids could be flung towards the inner, rocky worlds due to the gravitational influence from Jupiter, it stands to reason that these Kuiper Belt objects could similarly be flung inwards thanks to Neptune.


(Image credit: source unknown, retrieved from clowder.net.)

There are some dead giveaways that your object isn't from the same part of the Solar System as its initial planet is. There's the elemental composition / density argument, of course, but simply via random chance, 50% of these objects that get captured will wind up revolving around their planet the wrong way. One obvious guy like this is Neptune's largest moon, Triton.


(Image credit: Voyager Spacecraft, S. Albers / NOAA / GSD.)

Triton is maybe the easiest one; he's so large that if he were still in the Kuiper belt, he'd be the largest object there, dwarfing (burn!) both Pluto and Eris!

But there are others, elsewhere, that don't quite look like they belong. And a Saturnian mystery may, in fact, be on the cusp of being solved thanks to this idea.


(Image credit: Cassini / NASA / JPL-Caltech.)

This is Iapetus, one of Saturn's moons, looking like it always does: like it came out on the wrong side of a trip through the mud. Iapetus does all the moon-like things correctly: it revolves the right way around Saturn, it's got the right density for its spot in the Solar System, its surface is even made of the same elements -- as far as we can tell -- as it ought to be.

Except for that muddy mess that discolors one of its face. What's going on here? It turns out Iapetus isn't alone.


(Illustration credit: AP / NASA, retrieved from here.)

A giant, diffuse outer ring, well beyond the Saturnian rings you're used to, pollutes Iapetus' orbit. As the tidally-locked moon speeds around Saturn, these grains from the ring smack into Iapetus, discoloring it like billions of bugs on a windshield.

The question, of course, is where did this ring come from? Because it isn't Saturn. The answer is much more fun than that!


(Image credit: Cassini / NASA / JPL-Caltech.)

Say hello to Phoebe, Saturn's very suspicious moon, located in the same vicinity as both this outermost ring and Iapetus. Phoebe is full of craters, a different color and elemental composition than the other moons, and -- this is a big and -- it revolves around Saturn the wrong way!

In other words, this outsider came all the way from the Kuiper Belt to become a moon of Saturn! And the journey was no picnic for Phoebe, either.


(Image credit: NASA / Cassini / Caroline Porco / CICLOPS.)

Those craters on its surface are from a lifetime of bombardment! The once-spherical Phoebe has lost a lot of its mass, and that's almost certainly where the material that makes up both the outermost ring and the diffuse discoloring of Iapetus comes from!

Let this be a lesson to all of you: if you want to be adopted by another planet, make sure you orbit the same direction as everything else! In the meantime, know that objects from the asteroid belt or Kuiper Belt could come in at any time, and could even become our planet's next additional moon!

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Categories: Education

Ten Years Before the Blog: 2004-2005 [Uncertain Principles]

Science Blogs Physcial Sciences - 1 May, 2012 - 20:33

Delayed again by the need to do actual, you know, work, here's a look back at the third year of this blog's existence. You can also read posts covering year one and year two.

2004-2005 was the last complete year before the move to ScienceBlogs in January of 2006, after which the making of these posts will become more complicated, because my posting rate went way up. For this year, though, I was still sticking to one post a day, and the blog had settled into a pretty decent groove.

The year did feature a brief foray into silly physics-related fiction, which might possibly be called a precursor to the books, and a local tv appearance related to the election of 2004 (which I had otherwise tried to blot from memory. Ye gods, that was depressing to relive). This was back before YouTube became really big, so I didn't include a clip in the post, but I added it a few years later, so you can see me talking about lying with statistics for a few seconds.

Specific posts of interest, by tagline category:

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Categories: Education

Thank You from the USA Science and Engineering Festival! [USA Science and Engineering Festival: The Blog]

Science Blogs Physcial Sciences - 1 May, 2012 - 18:54

The 2012 USA Science and Engineering Festival was a huge success this past weekend! More than 150,000 attendees battled the rain, traffic and crowds to celebrate science at the Convention Center!

Start of Festival.jpg

The Festival would not have been possible without the hard work of our amazing volunteers! Over 750 volunteers dedicated their valuable time and showed incredible patience and enthusiasm during their shifts at the Festival. We are so grateful to ALL of you! We received wonderful feedback about our exhibitors and the amazing hands-on activities. Exhibitors made each person feel welcome and thoroughly explained their activities to attendees of all ages. And finally, we are so thankful for the extraordinary generosity of our sponsors and Festival Host Lockheed Martin.


With over 3,000 exhibits and 150 stage shows, there are so many wonderful Festival moments to highlight. Our Festival Host Lockheed Martin surprised us all with a few last minute additions including presentations by US Olympic Speed Skaters and cast members of NCIS Los Angeles. R2D2 made a special appearance along with our science celebrities including astronauts, Bill Nye, the Mythbusters, Mayim Bialik and NAO the robot! It was quite apparent that kids of all ages explored their "inner scientist" and had an amazing time at the Festival!


Bill Nye the Science Guy delighted crowds all weekend long! Watch this clip courtesy of The Epoch Times:

We received quite a number of comments and suggestions via email, twitter and Facebook. Twitter followers were tweeting and posting pictures all weekend long! We greatly appreciate all of the feedback and will definitely take it all into consideration for the next celebration!

Here are some of our favorite comments:

C.N. writes: "I can't say enough good things about this event! It was wonderful to see so many children so engaged with science, and clearly having fun at the same time! This was probably the best children's festival I have ever attended. Please bring it back to DC next year!"

C.J. writes: "What a FABULOUS Festival! You guys outdid yourselves. The exhibits and volunteers were wonderful. Loved all the cool giveaways, especially Lockheed Martin's blue lighty necklace. Wish we could have seen more... I too am home resting my feet! Thank you!"

NAEYC writes: "It was wonderful to see so many families at the Festival, and teachers who came from a distance to get ideas for their program."

Exhibitor SEM Link writes: "Thank you USA Science & Engineering Festival for allowing SEM Link to be a Partner and Exhibitor for the 2nd US Science and Engineering Festival Grand Finale and Expo. We had a blast and look forward to participating in next year's festival."

J.B. writes: "Whoever came up with the idea of the Science Festival should be congratulated. It made science fun for my children to learn about."

And one of the best comments we received in response to the enormous crowds that attended the Festival was from L.Y. "How nice to see people excited about science and engineering! Nice switch from what people usually complain about.....lines, crowds at concerts, sporting events, etc! Maybe we are making progress!"

Festival Fun.jpg

Once again, we appreciate all of the feedback and please continue to share your favorite Festival moments on our Facebook page! Stay connected with the Festival and thank you all again your support and enthusiasm! We hope that the Festival inspired you to see that with hard work, dedication and of course the desire to dream big the possibilities are endless!

Enjoy this wonderful recap of Day 1 of the Expo by Festival Sponsor ENGINEERING.com:

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Categories: Education

A Tale of Two Predictions [A Few Things Ill Considered]

Science Blogs Physcial Sciences - 1 May, 2012 - 17:47

Real Climate has done two posts recently that I thought would be served well by their juxtaposition. The first one highlights an early projection of global mean temperatures made by Jim Hansen in 1981.

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Categories: Education

There's a little town down in Texas known as Wacko. For a reason. [Greg Laden's Blog]

Science Blogs Physcial Sciences - 1 May, 2012 - 14:00

Sometimes it's spelled "Waco" but we all know that it should be Wacko. Yet Another Zany Thing (YAZT) has happened there which you may find amusing.

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Categories: Education

Outland It's Not: Billionaires Plan Asteroid Mining [Uncertain Principles]

Science Blogs Physcial Sciences - 30 April, 2012 - 16:22

I'm about a week late talking about this, but I've mostly resigned myself to not doing really topical blogging these days. Anyway, there was a lot of excitement last week over the announcement that an all-star team of nerd billionaires is planning to do commercial asteroid mining. (The post title is a reference to the Sean Connery movie, not the post-Bloom County comic.) I find it kind of amusing that this made the news while I'm doing retrospective blog posts (the next of which is coming), which have turned up a bunch of old posts where I say skeptical things about space in general. So I sort of feel like I ought to say something, and give other people the chance to talk about it in comments.

All in all, I'm pretty much on board with Phil Plait's cautious optimism. The three-stage plan they sketch out seems well considered, they have some plausible-sounding technology, and the principals involved are both seriously smart rich people and people who have shown a willingness to spend huge sums of money to achieve goals they find worthwhile. If this sort of project is ever going to work, this is the kind of team you want working on it.

My primary initial reaction to this was not so much excitement at the idea of asteroid mining per se, because there are a huge number of things that have to fall out the right way for that to work. What struck me as interesting about the initial plan is the first stage, where they plan to launch some unspecified number of small space telescopes. The idea is to use these to detect, identify, and try to determine the composition of asteroids passing relatively near the Earth, but this strikes me as the sort of thing that's likely to turn out to have some scientific benefit that isn't part of the original plan. They're not very large (9" diameter is the spec that keeps getting thrown around), so I'm not quite sure what you'd do with them, but I'm pretty sure that if you gave a bunch of astronomers access to a whole bunch of these, they'd find something interesting to do. Actual astronomers are invited to chime in in the comments.

(The "can be turned toward the Earth" aspect of those seems slightly more problematic, though the resolution wouldn't be all that great. If I'm doing the math right, from the low-ish orbit of the ISS, they'd be able to resolve ~1m objects on the Earth's surface, and only around ~100m from geosynchronous orbit, so this isn't a total panopticon scenario.)

Anyway, I wish them luck, and I'm interested to see what comes of this.

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Categories: Education

Another Week of GW News, April 29, 2012 [A Few Things Ill Considered]

Science Blogs Physcial Sciences - 30 April, 2012 - 16:20

Logging the Onset of The Bottleneck Years
This weekly posting is brought to you courtesy of H. E. Taylor. Happy reading, I hope you enjoy this week's Global Warming news roundup

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Categories: Education

Weekend Diversion: Discover the Night Sky for Yourself! [Starts With A Bang]

Science Blogs Physcial Sciences - 28 April, 2012 - 23:20

"They will see us waving from such great heights
'Come down now,' they'll say.
But everything looks perfect from far away
'Come down now,' but we'll stay." -The Postal Service Whether you're under urban, city skies, where only a few dozen stars are visible on a clear night, or beneath some of the darkest skies on Earth, the Universe is out there, and you can get started discovering it, right now, for yourself. You can have yourself, as Bishop Allen would sing,

Another Wasted Night,

or you can take advantage of it. For me, I currently live in Portland, OR, where the twilight looks like this.


(Image credit: FocusX7 / B. Emmerling on flickr.)

When the Moon sets and the neighbors turn off all their lights, I can get skies that are darker than purely urban skies: maybe all the way down to (lower is better) a seven on the Bortle dark-sky scale.


(Image credit: Stellarium.)

But even with only the most major constellations and asterisms visible, there's still plenty to see, even in the city, if you're interested in exploring the night sky. Darker skies will only net you more (and fainter, dimmer, and more diffuse) objects, of course, so you'll want equipment that will be versatile. Normally, people just starting to take an interest in it have a large number of things they want, some of which they don't even realize they want. What are they?

  • You want something relatively inexpensive, because no one wants to blow a lot of money on something you're not even sure you'll like.
  • You want something that's quick easy to set up and take down, so that you'll use it often, even late at night, when you're tired and/or unmotivated.
  • You want something where the optics are high-quality, because you want to see out into the Universe, not a scratchy, blurry haze.
  • You want something with a lot of light-gathering power, capable of seeing as much as you can for the skies that you have.
  • And, let's face it, you want something that's durable, because you never take as good care of your stuff as you wish you did.
So, what would I recommend to a beginning skywatcher? I gave some general advice once before, but let me share with you the best astronomy present I've ever, personally, bought for myself.


(Image credit: Focus Scientific.)

This is my preferred tool for checking out the night sky, no matter where I am: a pair of Celestron Skymaster, 20x80mm binoculars. These are versatile -- both for people who do and don't wear glasses -- and they meet all of the criteria above.

  • They're cheap, costing only about $100 if you shop around.
  • You'll also need a (not included) tripod. The crummy $40 one I bought at Circuit City five years ago is just fine for this, but this is really the upper limit (in weight) that a cheap tripod like this can handle.
  • Some lying liars will tell you that you can do just fine without them, but they're no longer with us because they've burned to a crisp from the fires that engulfed them, originating in their pants. Why do you think it has a built-in tripod mount?!


(Images credit: a review at Buzzillions.)

  • The 80mm number in that title refers to the diameter of each light-gathering lens, which means these binoculars (when you use both eyes) have the equivalent light gathering power to a 4.5" telescope!
  • The optics are multi-coated and the telescope is water/weather resistant, which is very good, but not quite the best. If you want to pay a lot more, you can go for fully-coated optics, and/or a waterproof pair, but for this price point you're not going to find better.
  • Finally, setup takes only about 10 minutes, including focusing. The lone exception is that for some pairs (mine wasn't one of them), collimation is a problem, which requires you to either fix them yourself (with an eyeglasses screwdriver), send them in to Celestron, or take them into a camera shop. If you do have this problem, it's a one-time-only fix.


I like these binoculars much better than a telescope for quick setup and takedown, and they really shine -- especially for beginning skywatchers -- for a few reasons. First off, they have a much wider field of view, meaning that when you see an object in the sky, it's much easier for a novice to locate it through binoculars than through a telescope. Second, it's much easier to get to know your night sky, to just move around and explore. Poke around your favorite constellations and bright stars and see what's there. You can see roughly 30-100 times as many stars through a pair of binoculars like this than you can with your naked eye, no matter what the viewing conditions are. The deep-sky objects, ideal for viewing under skies with less light pollution, can be found with these binoculars, too. (The free, downloadable software Stellarium is invaluable for finding what is where, and when.)

And finally, the 20x magnification (what that first number means in binocular-speak) is enough to see some amazing things! The last time I took them out was Sunday night, which was unseasonably warm and clear. Yes, I got to see the color of some of my favorite stars, as well as the pink/red disk of Mars. But there were a few highlights that I wanted to share.


(Image credit: gaelicstorm7 (Alan) of Stargazers Lounge.)

Saturn, bright and yellow in the night sky, has rings that are actually distinctly visible through these binoculars! I wasn't entirely sure I'd be able to see them, but when I had it centered in the field of view and truly focused the binoculars properly, the nearly edge-on rings came into crisp view, and it was my first time seeing them with my own, personal equipment!


(Image credit: John Graham at Cloudy Nights.)

As far as stars go, whenever the Big Dipper is prominent, you owe it to yourself to check out the second star from the end of the handle: Mizar. It's not only a binary star system, with the bright star Alcor also present, but there are many other, fainter stars there as well! Even with my lousy, fairly urban skies, I was very clearly able to see the third brightest star in there, which marked only the second time in my life I'd ever seen it, and again, the first time I'd found it on my own.

And last of all, there's the brightest object that isn't named the Moon in our current night sky.


(Image credit: David at the Astronomy Nexus.)

Venus! Currently in its crescent phase, you'll be able to watch Venus' crescent progressively shrink and shrink over the coming 5 weeks, until in early June it actually transits in front of the Sun, for the last time until 2117!

So if you've got an interest in the night sky, but not a lot of time, money, and not even necessarily good skies, there are still some amazing sights just waiting for you. The question is what are you waiting for; the Universe is yours to explore!

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Categories: Education

Why Should There Be Dark Matter? [Starts With A Bang]

Science Blogs Physcial Sciences - 28 April, 2012 - 05:32

"And what I wanted to do was, I wanted to explore problems and areas where we didn't have answers. In fact, where we didn't even know the right questions to ask." -Donald Johanson You can learn an awful lot about the Universe by asking it different questions than you asked about it previously. If all you ever used were your own senses, there would be an awful lot to learn, but you would be severely limited.

Grizzle Peak snow.jpeg

(Image credit: Kerri Rankin Thoreson.)

Even from the highest mountaintops, for example, you'd never be able to distinguish whether the Earth was round like a sphere or flat as a pancake, if all you used were your eyes. But by looking at the Earth on a larger scale than you could achieve otherwise, its roundness becomes both apparent and indisputable.


(Image credit: NASA / Johnson Space Center.)

The same thing applies to the Universe, both on large scales and small. If you want to know what the overall structure is of the Universe, you have to look at it on the largest scales. Looking at individual galaxies or even large clusters of galaxies won't get you there at all; if you want to know what your Universe looks like, you need to look at it on the largest and grandest of all scales, spanning billions of light years in all directions.


(Image credit: Sloan Digital Sky Survey - III / Data Release 8.)

In the above image, still showing just a fraction of the Universe scanned and measured by the Sloan Digital Sky Survey, each pixel represents an entire galaxy. By measuring how galaxies cluster and clump together -- how they are distributed throughout the Universe -- we can determine what it takes to create a Universe that looks like ours.


(Image credit: Millennium-XXL / Raul Angulo & Simon White / MPA-Garching.)

What we learn, as you can go through in detail, is that the structure of the Universe requires that there be a type of matter in it that does not collide with either normal matter or with photons, that outnumbers our (normal) matter by a factor of five- or six-to-one, that don't respond to either electric or magnetic fields, and that... frustratingly, can not be any of the known particles in the Universe!


(Image credit: Contemporary Physics Education Project.)

This would be a very, very big problem under one condition:

If the known particles and laws of physics explained all of the observed phenomena in the Universe.

In other words, if there's no new physics out there (beyond the standard model), then there's no need for any new particles out there, and so, why would there be any dark matter? There simply wouldn't be a strong motivation, not from an elementary physics standpoint.


(Image credit: retrieved from io9.)

And yet the opposite of that is also true: if there is physics out there that isn't explained by the standard model, then there must be new types of particles out there! And if there are new particles out there, there are good candidates for this dark matter. You've probably heard of some of the speculations that abound:


(Image credit: retrieved from École Polytechnique Fédérale de Lausanne.)

For example, if there's a symmetry of nature known as Supersymmetry (or SUSY, for short), then there ought to be twice as many fundamental particles as the ones we currently know about. Moreover, the lightest one is a perfect candidate for dark matter! Until we know what this particle's properties are, however, we don't know exactly what predictions to make as far as particle-particle interactions go.

While dark matter may or may not be supersymmetric in nature (many argue that SUSY may not even exist), this last part -- that until we know what dark matter's particle properties are, we don't know what predictions to make for dark matter's interactions -- is generally true. But there are plenty of other ideas. Two more speculative ones, first, and then two definitive ones.


(Image credit: Kamioka Observatory, ICRR, Univ. of Tokyo.)

The electromagnetic, weak, and strong nuclear forces could all unify at some high energy, in what's called a Grand Unified Theory, or GUT. One of the universal consequences of GUTs is that they all predict that protons will decay, and so that's one of the things we look for. In many variants of GUTs, there are candidates for dark matter that emerge naturally.


(Image credit: Brian Greene / Columbia University.)

Same case for extra dimensions; they may or may not exist, but if they do, then there are plenty of new particles and interactions that certainly exist, and one (or some) of them may make excellent dark matter candidates.

But those -- supersymmetry, grand unification, and extra dimensions -- are speculative ideas, and may not describe our Universe. But there are two observations that we have already made in the Standard Model that already cannot be explained by the particles and interactions we know today. This means there are new particles out there, yet undiscovered, that could easily solve the dark matter problem.


(Image credit: Hiroshi Nunokawa.)

For one, neutrinos have mass! According to the Standard Model, there should only be one type of neutrino -- a left-handed one -- and they should have zero mass. But this is not the case!

They are observed to have non-zero mass. In fact, all three types of neutrinos have non-zero mass, meaning there is new physics and there are new particles out there! Right-handed (or sterile) neutrinos could very easily make up the dark matter; we are searching for them as you read this! But perhaps the new physics that explains neutrinos isn't also what explains dark matter. There's another problem.


(Image credit: Normal Rockwell, retrieved from here.)

There are a couple of fundamental symmetries of nature that, at least in everyday life, seem pretty obvious. One is that the laws of physics in a mirror -- where left and right are reversed -- are the same as our normal laws of physics. (We call that Parity, or P-symmetry.) Another is that matter and anti-matter obey the same laws of physics. (We call that Charge Conjugation, or C-symmetry.) Most laws of physics that you know, like gravity and electromagnetism, always obey these symmetries.

According to the standard model, they have to; it's coded into the physics. But these symmetries don't exist for the nuclear (weak and strong) forces in the standard model. If I took something like a muon, reflected it in the mirror (applying P-symmetry), and replaced that image with an anti-muon (applying C-symmetry), I'd be testing whether the combination of CP-symmetry was a good one or not.


(Image credit: James Schombert at University of Oregon.)

If it were a good symmetry, then if all the muons decayed with one orientation, all the anti-muons would decay with that specific, mirrored orientation. But they don't, and so that CP-symmetry is violated. This is good for the Universe, because CP-violation is one of the necessary things to make more matter than anti-matter. But if it happens for an interaction like this -- the Weak nuclear interaction -- then it stands to reason that it should also happen for the strong nuclear force.

But it doesn't! Why wouldn't it?


(Image credit: Playmobil Circus Tightrope Artists Performers, retrieved here.)

The same reason this unicycle toy doesn't tip over: there must be some sort of extra, hidden weight that provides extra balance, or in the particle's case, crushes the amount of strong CP violation. Theoretically, the standard model allows you to violate both C and P together here, but we've looked, and to something like one part in a billion, we don't see any. So something -- and this means there's new physics -- has got to be forbidding it!

This outstanding problem, known as the Strong CP problem, is the second hint of new physics that must go beyond the standard model. And at least one class of solutions to it produces an outstanding dark matter candidate, known as the axion.


(Image credit: Axion Dark Matter Experiment (ADMX), LLNL's flickr.)

There's definitely physics in this world that's beyond the standard model, there's definitely more to neutrinos than we know, and there's definitely something stopping CP violation from occurring in the strong interactions. There may also be extra dimensions, grand unification, supersymmetry, or something even more exotic or surprising. But all of these possibilities require new particles, many of which make good dark matter candidates, and all of which have unknown particle parameters.

When you combine this information with our astrophysical knowledge of dark matter, you can see why I prefer the approach of using the astrophysics to try and reconstruct/determine some of the particle properties of dark matter, and try to guide us as to what we should look for. (No, really, I sometimes research that!)

We've got lots of options and lots of searches going, but there's so much we don't know about it at this point! Cross-sections, masses, reaction rates, lifetimes, etc., they're all mysteries at this point. We may not know what dark matter is, exactly, but we've got lots of strong possibilities for what it could be, and some hints that simply can't be ignored. We're desperately trying to be able to detect it directly, and solve this mystery once and for all. Welcome to the cutting edge!

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Categories: Education

Tomorrow: Join us for the Woodstock of Science! [USA Science and Engineering Festival: The Blog]

Science Blogs Physcial Sciences - 27 April, 2012 - 19:21

The excitement is filling the air at Sneak Peek Friday today as we are gearing up for an amazing weekend! The Festival takes place Saturday from 10-6 and Sunday from 10-4 at the Walter E Washington Convention Center in Washington, D.C. Please visit our "Plan Your Day" section on our website for important information regarding attending this FREE event. Those attending the Festival will be in for quite a treat with over 3,000 hands-on science and engineering activities and over 150 stage shows!

We have had some incredible events leading up to this weekend including our AT&T Sponsored Nifty Fifty Program. The 'Nifty Fifty (times 2)' are a group of one hundred noted science and engineering professionals who visited Washington, D.C. area schools to speak about their work and careers. We were absolutely thrilled with the speakers and the students seemed to really enjoy this talented group that presented with such passion and enthusiasm.

Thumbnail image for Nifty.jpgSome of the Nifty Fifty Speakers included NIH Director Francis Collins, NASA Deputy Administrator Lori Garver, Evolutionary Biologist Dr. Beth Shapiro, Nerd Girls Founder & Engineer Dr. Karen Panetta and many more! Students learned about the need to preserve coral reefs, sustainable 'Styrofoam' made from mushrooms, how diseases are cured and best of all the importance to follow their dreams and overcome obstacles.

This weekend the Festival will be jam packed with entertainment for the entire family. The Expo exhibits and stage shows are suitable for ALL AGES! We have a huge line up of entertainment for the little ones including PBS Kids, a plethora of exhibits and events for students of all ages and of course some in depth STEM exhibits for those with the advanced scientific palate. We have some big name science celebrities that will be in attendance including Bill Nye the Science Guy, Adam Savage and Jamie Hyneman from the Mythbusters, Big Bang Theory's Mayim Bialik, Sleight-of-hand Artist Apollo Robbins and Discovery Channel's Jeff Lieberman. Our Book Fair features 36 of the TOP science authors such as Homer Hickam, Robin Cook, Carl Zimmer, Lisa Randall and Ken Denmead.

Here are just a few of the stage shows and hands-on exhibits that you can look forward to:
The Many Worlds of Lockheed Martin. Check out more than 25 new exhibits from Lockheed Martin, the official host of the Festival! Immerse yourself in the cockpit simulator of an F-22 fighter jet, tour cities of the future; delve into the wonders of robotics and the Hubble telescope, plus many more exciting adventures!

Meet the Scientists/Engineers. Chat one-on-one at this Career Pavilion location with some of the nation's top scientists, engineers to learn about such fields as medical research, oceanography, national security with the CIA, microbiology, and technology intellectual property law!

Innovative Entrepreneurs. Hear these exciting entrepreneurs who are changing the course of technology: Elon Musk, creator of rocket manufacturer SpaceX, and legendary computer video game innovator Richard Garriott who became the sixth private citizen to journey into Earth's orbit.

Music by Monty Harper. Dance like a dinosaur and spin like a planet. You'll do it all to the music of this science singer-musician who was recently named a winner in the Festival's songwriting competition.

Ready for the Science Olympiads? Learn how to compete in the Science Olympiads from Olympiad student teams in the DC Metro area who will demonstrate vehicles, structures, musical instruments and other devices they've developed for the competition!

Saving the Humpback. Nan Hauser, founder of the Center for Cetacean Research & Conservation, will inspire you with her fascinating expeditions to save the endangered humpback whale and other marine species.

Circus Physics. How do all those clowns fit in one car? What's involved in the physics of the ferris wheel and roller coaster? Come to the circus exhibit of the American Institute of Physics and other partners to find out!

The Science of Bubbles. The fascinating Keith Michael Johnson (as seen on the Discovery Channel's Time Warp), uses soap bubbles to explain liquids, solids and gasses, geometry, tension and pressure.

Enjoy yourself this weekend and take time to explore as much as you can. We hope the Festival ignites the "Inner Scientist or Engineer" in you! Thank you for all of your support and have an amazing time!

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Categories: Education

Book Roundup: People Talking About Dog Physics [Uncertain Principles]

Science Blogs Physcial Sciences - 26 April, 2012 - 22:09

sidebar_relativity_cover.jpgI've been falling down on the shameless self-promotion front, lately, but that doesn't mean I'm not tracking How to Teach Relativity to Your Dog obsessively, just that I'm too busy to talk about it. Happily, other people have been nice enough to talk about it for me, in a variety of places:

  • The most significant, in terms of probable impact on sales, is this excerpt at BoingBoing, which is the text for the dog dialogue from Chapter 8. This is the same dialogue that became the "Looking for the Bacon Boson" video, and, indeed, they were nice enough to include the video in the post, too. Woo-hoo!
  • Over at Backreaction, Bee gave the book a nice review ("a flawless popular science book that gets across a lot of physics in an entertaining way. If you always wanted to know what special and general relativity is all about and why it matters, this is a good starting point."). This is a huge relief not just because she said nice things about it, but because she didn't spot any huge mistakes, which I'm always paranoid about when I see actual physicists writing about my stuff.
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Categories: Education

Just Two Days Until the Largest Celebration of Science & Engineering! [USA Science and Engineering Festival: The Blog]

Science Blogs Physcial Sciences - 26 April, 2012 - 15:19

molecula-photo.jpgThe 2nd USA Science & Engineering Festival has finally arrived! The Expo will take place this weekend at the Walter E Washington Convention Center in Washington, DC. The hours are Saturday from 10-6 and Sunday from 10-4. Evening shows are also scheduled for the weekend including the Stargazing Party with Bill Nye and Featured Author Panel Discussion- Science Stories in Society & School: Using Narrative to Bridge the Gap.

The Festival will be packed with entertainment for the whole family with 3,000 amazing hands-on exhibits and over 150 incredible stage shows. This FREE event is perfect for all ages and has something special for just about everyone. We have created "thematic tracks"' including Tiny Animal Lovers, Math is Really Fun, Be a Robotics Engineer, Nuclear to Stellar and much more to make your Festival experience fun, easy and enjoyable. Please visit our Plan Your Day Section on our website for all your Festival questions. And be sure to download our free Festival App to stay connected to the Expo using your mobile device. Iphone users can download the app here and Android users can download the app here.

We thank you for all of your support and look forward to seeing you this weekend! Please enjoy this awesome video created by Festival Founder Larry Bock's talented daughter:

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Categories: Education

So, you've learned that the Sun is going to explode... [Starts With A Bang]

Science Blogs Physcial Sciences - 26 April, 2012 - 07:25

"Through that last dark cloud is a dying star... And when it explodes, it will be reborn. You will bloom... and I will live." -The Fountain I want to start off by letting you all know that I, myself, do not have any children of my own. I have taught children, adolescents and adults for nearly a full generation now in varying capacities, and while each learner is different, there's one science fact that universally seems to shatter each and every one of them.

P2121843 - edit.jpeg

(Image credit: the bloggers at Dear Kugluktuk.)

The fact that the Sun, our Sun, the bringer of warmth, light, energy, and the sustaining force of all life on this planet, isn't going to shine forever. Quite to the contrary, someday, the Sun will die in a fiery, catastrophic explosion, one which will quite possibly obliterate our entire planet, and then eventually cease to shine at all.


(Image credit: L.Calçada / ESO.)

Being faced with not only our own mortality, but the demise of literally everything we've ever encountered throughout the entire history of our world is a philosophical and existential challenge for even well-adjusted adults. But I was a bit taken aback when I received this question from one of my most loyal readers: I need a good explanation for a third grader, whose Mom tells me is deeply concerned, that the sun will blow up. I sympathize with parents in this position, because on the one hand, you want to tell the truth to your children. You want to expose them to our most accurate understanding of reality, to have them learn and appreciate knowledge, science, and using their minds.

But you not only want to do that with kindness, compassion, and optimism, you also don't want your kid having night terrors and years of therapy because you told them the gory details of, literally, the end of the world.


(Image credit: Brian Smallwood.)

There is, perhaps, a wrong way to go about this. As the comedian Louis C.K. once said, She started crying immediately, crying bitter tears for the death of all humanity... and now she knows all of those things: she's gonna die, everybody she knows is gonna die, they're gonna be dead for a very long time, and then the sun's gonna explode. She learned that all in 12 seconds, at the age of seven. That's one approach, but maybe not the one I would choose if I were going to put some thought into it. You see, there's a remarkable story to be told, and if I were in elementary school, it just might be the most wonderful thing I had ever heard at that point in my life. Here's what I would tell a child.


(Image credit: Hana Druckmüllerová, Úpice Observatory, and Miloslav Druckmüller.)

The Sun that you know, the brightest thing in the sky, is no more special than any other star in the sky. Even during the day, there are thousands of stars in the sky. You'd be able to see them, too, except that our star, the Sun, is so close to us that its brightness makes all the other stars invisible, except at night.


(Image credit: Tony Hallas, retrieved from APOD.)

These stars, each and every one of them, live much, much longer than anything on Earth has ever lived. While some plants and animals can live for thousands of years, the stars all live, burning brightly, for millions, billions, or even trillions of years.

That's a very, very long time! But it isn't forever, and believe it or not, we're lucky that it isn't forever.


(Image credit: Oliverbeatson at wikipedia.)

Because if the stars never died, if they never exploded, and if they never blew up, we wouldn't be here, talking to each other, right now. And I'm so glad that we are, because you get to learn one of the most amazing secrets about life, and I get to teach it to you.


(Image credit: Ed Uthman.)

The secret is that practically everything that makes up you, me, and the entire planet -- the tiniest parts of everything we've ever known -- they were all made inside a star.

But it's too hot for you and me inside a star. In order to make Earth, and you, and me, all the good things that the stars make need to get out, so they can make something new. And how does that happen?

(Video credit: ESA/NASA, retrieved here.)

Why, they explode. And the insides of the star, the things that it made while it was alive, you know what they do?


(Image credit: NASA/JPL-Caltech/T. Pyle (SSC).)

The old insides from those stars make planets, like Earth, and -- because we're very lucky -- some of those insides make up us, too.

The stars of the past died so that you could be here, and someday, a long time from now, our Sun will return the favor, and help make more new planets, new worlds, and new chances for life.


(Image credit: ESA, NASA, and L. Calçada (ESO for STScI).)

So yes, the Sun will blow up, someday, but when it does, that's the greatest gift any star can ever hope to give to the Universe. After all, it took billions of stars giving that gift already in order to make you. And you know what?

It was worth it.

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Categories: Education

Historical Interdisciplinarity Examples? [Uncertain Principles]

Science Blogs Physcial Sciences - 25 April, 2012 - 15:51

For something I'm working on, I'm trying to come up with good examples of interdisciplinarity making a difference in science. Specifically, I'm looking for cases where somebody with training in one field was able to make a major advance in another field because their expertise let them look at a problem in a different way, and bring a different set of techniques to bear on it.

I can think of a decent number of examples within physics-- techniques from NMR being adopted by atomic physicists, atomic physics techniques being used to address problems in condensed matter, the whole Higgs boson business coming in part from condensed matter ideas-- but a lot of those are kind of subtle and technical. I feel like I must be missing something bigger and more obvious.

(I know about Schrödinger's turn toward biology late in life, but I'm not sure biologists find that as impressive as physicists do...)

So, help me out, here. What's the best example you know about of somebody from one field using their knowledge from that to make dramatic progress in another field? It doesn't need to involve a physicist, either (so I'll cross-list this in the life science channel at ScienceBlogs)-- chemists revolutionizing biology or geology (or vice versa) would be great, too.

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Categories: Education

The Sombrero is Two Galaxies in the Same Spot in the Universe [Greg Laden's Blog]

Science Blogs Physcial Sciences - 25 April, 2012 - 15:09

The Sombrero Galaxy's Split Personality: The infrared vision of NASA's Spitzer Space Telescope has revealed that the Sombrero galaxy -- named after its appearance in visible light to a wide-brimmed hat -- is in fact two galaxies in one. It is a large elliptical galaxy (blue-green) with a thin disk galaxy (partly seen in red) embedded within. Previous visible-light images led astronomers to believe the Sombrero was simply a regular flat disk galaxy. Spitzer's infrared view highlights the stars and dust. The starlight detected at 3.5 and 4.6 microns is represented in blue-green while the dust detected at 8.0 microns appears red. This image allowed astronomers to sample the full population of stars in the galaxy, in addition to its structure. The flat disk within the galaxy is made up of two portions. The inner disk is composed almost entirely of stars, with no dust. Beyond this is a slight gap, then an outer ring of intermingled dust and stars, seen here in red. Image credit: NASA/JPL-Caltech

From the Press Release:

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Categories: Education

Ten Years Before the Blog: 2003-2004 [Uncertain Principles]

Science Blogs Physcial Sciences - 24 April, 2012 - 21:29

The schedule called for this to appear last Friday, but as I was just back from a funeral, yeah, not so much. I had already gone through and bookmarked a whole slew of old posts, though, so here's a recap of the 2003-2004 blogademic year (starting and ending in late June).

This year saw a few milestones, though not quite as many as the previous year. I got a grant, passed my third-year reappointment review (the first big hurdle on the way to tenure), and we had a visiting speaker from Yale one week who mentioned in passing an idea that became central to my research program.

Probably the most significant milestone, though it didn't necessarily seem that way at the time, was when we adopted Emmy. If you've read How to Teach Physics to Your Dog, the Introduction includes a dog dialogue sitting on a bench at the Mohawk-Hudson Humane Society, which is, in fact, where I made the decision to take her home. Which has paid off far more literally than I ever would've guessed. As a bonus, this year also includes the very first conversation with Emmy on the blog, though it took a different form than the conversations that would eventually become (nerd) famous.

Other notable posts from the year include:

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Categories: Education

Physics Day Poll: Favorite Physicist? [Uncertain Principles]

Science Blogs Physcial Sciences - 24 April, 2012 - 17:17

Over in Twitter-land, there's a bunch of talk about how this is National Physics Day. I don't know how I missed that, what with all the media coverage and all.

I have too much other stuff to do to generate any detailed physics content today, so we'll settle for an informal poll to mark the occasion:

Who is your favorite physicist, other than Einstein, Newton, or Feynman?

The qualifier is just to knock out the too-obvious answers, and force a little more thought. Everybody likes Einstein and Newton and Feynman, but we hear about them all the time. For a major holiday like Physics Day, let's go a little deeper.

Other than that one restriction, it's wide open: could be living or dead, theorist or experimentalist, whatever. The definition of "favorite" is open as well-- whatever you want that to mean. Though it would be nice if you explained your reasoning in the comments.

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Categories: Education

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