"Science progresses best when observations force us to alter our preconceptions." -Vera Rubin I want you to think about the Universe. The whole thing; about everything that physically exists, both visible and invisible, about the laws of nature that they obey, and about your place in it.
It's a daunting, terrifying, and simultaneously beautiful and wondrous thing, isn't it?
(Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team.)
After all, we spend our entire lives on one rocky world, that's just one of many planets orbiting our Sun, which is just one star among hundreds of billions in our Milky Way galaxy, which is just one galaxy among hundreds of billions that make up our observable Universe.
Yes, we've learned an awful lot about what's out there and our place in it. As best as we can tell, we've learned what the fundamental laws are that govern everything in it, too!
(Image credit: Mark Garlick / SPL, retrieved from the BBC.)
As far as gravitation goes, Einstein's theory of general relativity explains everything from how matter and energy bend starlight to why clocks run slow in strong gravitational fields to how the Universe expands as it ages. It is arguably the most well-tested and vetted scientific theory of all time, and every single one of its predictions that has ever been precision-tested has been verified to be spot-on.
(Image credit: Contemporary Physics Education Project.)
On the other hand, we've got the standard model of elementary particles and interactions, which explains everything known to exist in the Universe, and all the other (nuclear and electromagnetic) forces that they experience. This, also, is arguably the most well-tested and vetted scientific theory of all time.
And you would think that if our understanding of things were perfect, if we knew all about the structure of the Universe, the matter in it, and the laws of physics that it obeyed, we'd be able to explain everything. Why? Because all you'd have to do is start out with some set of initial conditions -- immediately following the Big Bang -- for all the particles in the Universe, apply those laws of nature that we know, and see what it turns into over time! It's a hard problem, but in theory, it should be not only possible to simulate, it should give us a sample Universe that looks just like the one we have today.
(Image credit: NASA / WMAP Science Team.)
But this doesn't happen. In fact, this doesn't happen at all. This picture I painted for you above is all true, on the one hand, but we also know that it isn't the whole story. There are other things going on that we don't fully understand.
Here, as best as I can present the full history in a single blog post, is the whole story.
(Visualizations & Simulations: Ralf Kähler, Tom Abel, and Oliver Hahn (KIPAC).)
As we come forward from the event of the Big Bang, our Universe expands, cools, while the entire time experiencing the irresistible force of gravity. Over time, a number of extremely important events happen, including, in chronological order:
- the formation of the first atomic nuclei,
- the formation of the first neutral atoms,
- the formation of stars, galaxies, clusters, and large-scale structure,
- and how the Universe expands over its entire history.
- what nuclei form and when in the early Universe,
- what the radiation from the last-scattering-surface, when the first neutral atoms are formed, looks like in great detail,
- what the structure of the Universe, from large scales down to small scales, looks like both today and at any moment in the Universe's past,
- and how the scale, size, and number of objects in the observable Universe have evolved over its history.
(Image credit: NASA / Goddard Space Flight Center / WMAP101087.)
What we consider to be normal matter, that is, stuff made up of atoms, is highly constrained by a variety of measurements. Before any stars formed, the nuclear furnace of the very early Universe fused the first protons and neutrons together in very specific ratios, depending on how much matter and how many photons there were at the time.
What our measurements tell us, and they've been verified directly, is exactly how much normal matter there is in the Universe. This number is incredibly tightly constrained to be -- in terms that might be familiar to you -- about 0.262 protons + neutrons per cubic meter. There could be 0.28, or 0.24, or some other number in that range, but there really couldn't be more or less than that; our observations are too solid.
(Image credit: Ned Wright.)
After that, the Universe continues to expand and cool, until eventually the photons in the Universe -- which outnumber the nuclei by more than a billion-to-one -- lose enough energy that neutral atoms can form without immediately being blasted apart.
When these neutral atoms finally form, the photons are free to travel, uninhibited, in whatever direction they happened to be moving last. Billions of years later, that leftover glow from the Big Bang -- those photons -- are still around, but they've continued to cool, and are now in the microwave portion of the electromagnetic spectrum. First observed in the 1960s, we've now not only measured this Cosmic Microwave Background, we've measured the tiny temperature fluctuations -- microKelvin-scale fluctuations -- that exist in it.
These temperature fluctuations, and the magnitudes, correlations and scales on which they appear, can give us an incredible amount of information about the Universe. In particular, one of the things they can tell us is what the ratio of total matter in the Universe is to the ratio of normal matter. We would see a very particular pattern if that number were 100%, and the pattern we do see looks nothing like that.
Here's what we find.
(Image credit: Pavel Kroupa.)
The necessary ratio is about 5:1, meaning that only about 20% of the matter in the Universe can be normal matter. This doesn't tell us anything what this other 80% is. From the Cosmic Microwave Background alone, we only know that it exerts a gravitational influence like normal matter, but it doesn't interact with electromagnetic radiation (photons) like normal matter does.
You can also imagine that we've got something wrong about the laws of gravity; that there's some modification we can make to it to mimic this effect that we can re-create by putting in dark matter. We don't know what sort of modification could do that (we haven't successfully found one, yet), but it is conceivable that we've just got the laws of gravity wrong. If a modified theory of gravity could explain the fluctuations of in the Microwave Background without any dark matter at all, that would be incredibly interesting.
But if there really is dark matter, it could be something light, like a neutrino, or something very heavy, like a theorized WIMP. It could be something fast-moving, with a lot of kinetic energy, or it could be something slow-moving, with practically none. We just know that all of the matter can't be the normal stuff we're used to, and that we've come to expect. But we can learn more about it by simulating how structure -- stars, galaxies, clusters, and large-scale structure -- forms in the Universe.
(Video credit: DEUS Consortium.)
Because the types of structures you get out -- including what types of galaxies, clusters, gas clouds, etc. -- exist at all times in the Universe's history. These differences don't show up in the Cosmic Microwave Background, but they do show up in the structures that form in the Universe.
What we do is take a look at the galaxies that form in the Universe and see how they cluster together: how far away from a galaxy do I have to look before I see a second galaxy? How early in the Universe do large galaxies and clusters form? How quickly do the first stars and galaxies form? And what can we learn about the matter in the Universe from this?
(Image credit: E.M. Huff; SDSS-III; South Pole Telescope / Zosia Rostomian.)
Because if the dark matter -- which doesn't interact with light or normal matter -- has lots of kinetic energy, it will delay the formation of stars, galaxies, and clusters. If the dark matter has some but not too much, it makes it easier to form clusters, but still hard to form stars and galaxies early on. If the dark matter has virtually none, we should form stars and galaxies early. Also, the more dark matter there is (relative to normal matter), the more smooth the correlations will be between galaxies on different scale, while the less dark matter there is means that the differences in correlations between different scales will be very stark.
The reason for this is that early on, when clouds of normal matter starts to contract beneath the force of gravity, the radiation pressure increases, causing the atoms to "bounce back" on certain scales. But dark matter, being invisible to photons, wouldn't do this. So if we see how big these "bouncing features" are, known as baryon acoustic oscillations, we can learn whether there's dark matter or not, and -- if it's there -- what its properties are. The thing we construct, if we want to see this, is just as powerful as the graph of the fluctuations in the microwave background, a couple of images above. It's the much lesser-known but equally important Matter Power Spectrum, shown below.
(Image credit: W. Percival et al. / Sloan Digital Sky Survey.)
As you can clearly see, we do see these "bouncing" features, as those are the wiggles in the curve, above. But they're small bounces, consistent with 20% of the matter being "normal" matter and the vast majority of it being smooth, "dark" matter. Again, you might wonder if there isn't some way we could modify gravity to account for this type of measurement, rather than introducing dark matter. We haven't found one yet, but if such a modification were found, it would be awfully compelling. But we'd have to find a modification that works for both the matter power spectrum and the cosmic microwave background, the way that a Universe where 80% of the matter is dark matter works for both.
This is from the structure data on large scales; we can also look on small scales, and see whether small clouds of gas, in-between us and very distant, bright objects from the early Universe, are thoroughly gravitationally collapsed or not; we look at the Lyman-alpha forest for this.
(Image credit: Bob Carswell.)
These intervening, ultra-distant clouds of hydrogen gas teach us that, if there is dark matter, it must have very little kinetic energy. So this tells us that either the dark matter was born somewhat cold, without very much kinetic energy, or it's very massive, so that the heat from the early Universe wouldn't have much of an effect on the speed it was moving millions of years later on. In other words, as much as we can define a temperature for dark matter, assuming it exists, it's on the cold side.
But we also need to explain the smaller-scale structures that we have today, and examine in gory detail. This means when we look at galaxy clusters, they, too, should be made of 80% dark matter and 20% normal matter. The dark matter should exist in a big, diffuse halo around the galaxies and the clusters. The normal matter should be in a couple of different forms: the stars, which are extremely dense, collapsed objects, and the gas, diffuse (but denser than the dark matter) and in clouds, populating the interstellar and intergalactic medium. Under normal circumstances, the matter -- normal and dark -- is all held together, gravitationally. But every once in a while, these clusters merge together, resulting in a collision and a cosmic smash-up.
The dark matter from the two clusters should pass right through one another, because dark matter doesn't collide with normal matter or photons, as should the stars within the galaxies. (The stars not colliding is because the cluster collision is like firing two guns loaded with bird-shot at one another from 30 yards away: every single pellet should miss.) But the diffuse gas should heat up when they collide, radiating energy away in the X-ray (shown in pink) and losing momentum. In the Bullet Cluster, above, that's exactly what we see.
Ditto for the Musket Ball Cluster, a slightly older collision than the Bullet Cluster, that's just recently analyzed. But others are more complicated; cluster Abell 520, for example, below, appears to have too much gravity associated with a location that ought to have only normal matter and not dark matter.
(Image credit: NASA / CXC / CFHT / UVic. / A. Mahdavi et al.)
If we look at the individual components, you can see where the galaxies are (which is also where the dark matter ought to be), as well as the X-rays, which tell us where the gas is, you'd expect the lensing data -- which is sensitive to the mass (and hence, dark matter) -- to reflect that.
(Image credit: NASA, ESA, CFHT, CXO, M.J. Jee and A. Mahdavi.)
Instead, we see evidence for the gas creating a large amount of lensing, which shouldn't be. So, perhaps something funny is going on here. Maybe this is evidence in favor of modified gravity and against dark matter, as some contend. Or, perhaps, there's an explanation consistent with dark matter, and we simply have an unusual mass distribution in this type of smash-up.
But we can go to even smaller scales, and look at individual galaxies on their own. Because around every single galaxy, there should be a huge dark matter halo, comprising approximately 80% of the mass of the galaxy, but much larger and more diffuse than the galaxy itself.
(Image credit: ESO/L. Calçada.)
Whereas a spiral galaxy like the Milky Way might have a disc 100,000 light-years in diameter, its dark matter halo is expected to extend for a few million light-years! It's incredibly diffuse because it doesn't interact with photons or normal matter, and so has no way to lose momentum and form very dense structures like normal matter can.
What we don't yet have any information about, however, is whether dark matter interacts with itself in some way. Different simulations give very different results, for example, as to what the density of one of these halos ought to look like.
(Image credit: R. Lehoucq et al.)
If the dark matter is cold and doesn't interact with itself, it should have either an NFW or a Moore-type profile, above. But if it is allowed to thermalize with itself, it would make an isothermal profile. In other words, the density doesn't continue to increase as you get close to the core of a dark matter halo that's isothermal.
Why a dark matter halo would be isothermal isn't certain. Dark matter could be self-interacting, it could exhibit some sort of exclusion rule, it could be subject to a new, dark-matter-specific force, or something else that we haven't thought of yet. Or, of course, it could simply not exist, and the laws of gravity that we know could simply need modification. On galactic scales, this is where MOND, the theory of Modified Newtonian Dynamics, really shines.
(Image credit: University of Sheffield.)
While the NFW and Moore profiles -- the ones that come from the simplest models of Cold Dark Matter -- don't really match up with the observed rotation curves very well, MOND fits individual galaxies perfectly. The isothermal halos do a better job, but lack a compelling theoretical explanation. If we only based our understanding of the "missing mass" problem -- whether there was extra, "dark" matter, or whether there was a flaw in our theory of gravity -- on individual galaxies, I would likely side with the MOND-ian explanation.
So when you see a recent headline like Serious blow to dark matter theories?, you already have a hint that they're looking at individual galaxies. Let's see what this is about.
(Image credit: ESO/L. Calçada.)
A paper released just two days ago took a look at stars relatively close to our solar neighborhood, and looked for evidence of this inner distribution of mass from the theoretical dark matter halo. You'll notice, looking a couple of images up, that only the simplest, completely collision-less models of Cold Dark Matter give that large effect in the cores of dark matter halos.
So let's take a look at what the survey shows.
(Image credit: C. Moni Bidin et al., 2012.)
Indeed, the simple (NFW and Moore) halo profiles are highly disfavored, as many studies before have shown. Although this is interesting, because it demonstrates their insufficiency on these small scales in a new way.
So you ask yourself, do these small-scale studies, the ones that favor modified gravity, allow us to get away with a Universe without dark matter in explaining large-scale structure, the Lyman-alpha forest, the fluctuations in the cosmic microwave background, or the matter power spectrum of the Universe? The answers, at this point, are no, no, no, and no. Definitively. Which doesn't mean that dark matter is a definite yes, and that modifying gravity is a definite no. It just means that I know exactly what the relative successes and remaining challenges are for each of these options. It's why I unequivocally state that modern cosmology overwhelmingly favors dark matter over modified gravity. But I also know -- and freely admit -- exactly what it will take to change my scientific opinion of which one is the leading theory. And you're free to believe whatever it is you like, of course, but there are very good reasons why the modifications to gravity that one can make to have gravity succeed so well without dark matter on galactic scales fail to address the other observations without also including dark matter.
And we know what it isn't: it isn't baryonic (normal matter), it isn't black holes, it isn't photons, it isn't fast-moving, hot stuff, and it probably isn't simple, standard, cold and non-interacting stuff either, like most WIMP-type theories hope for.
(Image credit: Dark Matter Candidates, retrieved from IsraCast.)
I think it's likely to be something more complicated than the leading theories of today. Which isn't to say that I think I know exactly what dark matter is or how to find it. I'm even sympathetic to certain degrees of skepticism expressed on that account; I don't think I would claim to be 100% certain that dark matter is right and our theories of gravity are also right until we can verify dark matter's existence more directly. But, if you want to reject dark matter, there's a whole host of things you'll need to explain some other way. Don't completely ignore large-scale structure and the need to address it; that's a surefire way to fail to earn my respect, and the respect of every cosmologist who studies it.
And that's, as best as I can express it in a single blog post, the whole story on dark matter. I'm sure there are plenty of comments; let the fireworks begin!Read the comments on this post...
This post was written by Brookhaven Lab science writer Justin Eure.
Let's start with a number, by chance a palindrome: 1441. Imagine taking that many photographs of a single object, a soccer ball, say - obsessively capturing it from every angle to expose all the details. Those 1441 images provide all the evidence needed to illustrate and understand the three dimensional structure of that soccer ball. Each shot reveals another curve of the sphere, another line in the checkered pattern, another scuff or scratch along the surface.
That's the challenge that a team at Brookhaven National Laboratory overcame with a new transmission x-ray microscope (TXM), which successfully combined 1441 images of a lithium-ion battery electrode into a detailed 3D structure. The TXM, hooked up to an x-ray beamline at Brookhaven's National Synchrotron Light Source, generates unparalleled image resolutions, as demonstrated in a new paper published in Applied Physics Letters. Read the rest of this post... | Read the comments on this post...
I have not watched these yet myself, but will do as soon as I download and convert them for my iPhone, but I have no doubt they are up to Peter Sinclair's usual high standards.
Embedded below are part's 1 and 2 of Weird Winter - Mad March. Enjoy, discuss!Read the rest of this post... | Read the comments on this post...
Yesterday's post on applying intro physics concepts to the question of how fast and how long football players might accelerate generated a bunch of comments, several of them claiming that the model I used didn't match real data in the form of race clips and the like. One comment in particular linked to a PDF file including 10m "splits" for two Usain Bolt races, including a complicated model showing that he was still accelerating at 70m into the race. How does this affect my argument from yesterday?
Well, that document is really a guide to fancy fitting routines on some sort of graphing calculator or something. Which is fine as far as it goes, but I think it attributes too high a degree of reality to those unofficial split times, which are obtained from some unidentified web site. They proceed to fit a bunch of complicated functions to the data, but I think they're overthinking it.
Let's look at the actual data, graphed in more or less the way you would expect to see it in an intro physics class: as a plot of position vs. time:
The black circles represent the times from a race in 2008, the white circles times from a race in 2009. They're practically right on top of each other, because in absolute terms, the difference in times is pretty tiny.
Their first step is to fit a straight line to the data, which works remarkably well, even though it can't possibly be right. Looking at the graph, though, it does look awfully linear, particularly if you threw out the first point or two. That seems pretty consistent with the "accelerate to a maximum speed and stay there" model I assumed in the previous post, especially given that we don't know anything, really, about how these numbers were obtained.
Of course, the real test is to look at the speed as a function of time:Read the rest of this post... | Read the comments on this post...
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The European Space Agency has made its selection for the next Large Mission to be flown by ESA, with a launch window in about 2022
Over at Grantland, Bill Barnwell offers some unorthodox suggestions for replacing the kickoff in NFL games, which has apparently been floated as a way to improve player safety. Appropriately enough, the suggestion apparently came from Giants owner John Mara, which makes perfect sense giving that the Giants haven't had a decent kick returner since Dave Meggett twenty years ago, and their kick coverage team has lost them multiple games by giving up touchdowns to the other team.
Anyway, one of Barnwell's suggestions invoked physics, in a way that struck me as puzzling:
Idea 3: The receiving team's returner is handed the ball on his own goal line. His blockers must be positioned on the 20-yard line. The "kicking" team's players are positioned on the opposition's 40-yard line. Once the whistle blows, it's a traditional kick return.
Advantages: Everyone on the field will still be colliding, but because the kick-coverage team will have been running for 20 yards as opposed to 45, there won't be anywhere near as much momentum in those collisions. That should produce fewer injuries.
Now, if you know anything about introductory physics, you know that momentum is mass times velocity (for speeds much less than the speed of light). This doesn't have any direct relationship to the distance somebody has run to get to that point, unless they're accelerating the whole time. But it seems awfully unlikely to me that any of the whack jobs covering kicks in the NFL are actually speeding up appreciably between 20 and 45 yards-- they probably hit their top speed well before that.
Ah, but is there a way to use our knowledge of introductory physics to test this idea? That is, can we estimate the distance over which an NFL player is likely to be accelerating? Well, I would hardly be posting this if I didn't have a model for this sort of thing, so let's have a run at it (heh).Read the rest of this post... | Read the comments on this post...
"Truth is mighty and will prevail. There is nothing wrong with this, except that it ain't so." -Mark Twain
"It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong." -Richard Feynman Every day that you set forth in the world is a new opportunity to learn something about it. Every new observation that you make, every new test you perform, every novel encounter or piece of information you pick up is a new chance to be a scientist.
(Image credit: Alan Chen.)
You have a conception of how things work in this world. You've pieced it together as a combination of your experiences, your knowledge, and the working hypotheses that you've accepted as the best mirror of reality. And every new shred of evidence you pick up about reality interrogates these hypotheses, daring your picture of reality to hold up to this level of scrutiny.
No matter who you are, no matter how smart you are, no matter how brilliantly you've drawn the conclusions you've drawn from the evidence you've gathered, there will come an instance where the evidence you encounter will be irreconciliable with the picture of reality you presently hold. And when that moment happens, your response will mean absolutely everything.
(Image credit: Glennbeck.com.)
Because there is the possibility that your view of reality -- the way you make sense of things -- is flawed in some way. You have to open your self up to at least the possibility that you are wrong. It is a humbling admission, that you may be wrong, but it's also the most freeing thing in the world. Because if you can be wrong about something, then you can learn.
(Image credit: Dave Koerner at Northern Arizona University.)
The discovery that planets move about the Sun in ellipses required exactly that; were it not for Kepler and his ability to accept that his earlier models were flawed, and then abandon them and create new and improved ones, physics and astronomy would likely have been set back an entire generation. And if you, yourself, can do this in your own life, you can find a better explanation for the phenomena you encounter in this world. You can bring your understanding of the world more closely in line with what reality actually is. In other words, you can do what all good scientists do, and in the end, learn something amazing.
(Image credit: NASA, retrieved from Universe Today.)
But if you can't admit that you might be wrong, if your picture of reality is unchangeable despite any evidence to the contrary, if you refuse to assimilate new information and new knowledge and re-evaluate your prior stance on an issue, then you will never learn.
Perhaps as an adult you're entitled to that right; you are, after all, free to believe whatever you want. But if you're a student in school? Your job is to learn. If you don't do your job, particularly if you don't even try to do your job, it's your teachers duty -- and I would say responsibility -- to fail you.
At least, it should be. Recently, some incredibly appalling things have been happening in education that completely undermine this, including the banning of the words 'dinosaur' and 'evolution' from standardized tests and the passage of Tennessee's "academic freedom" bill that allows teachers to teach counterfactual scientific information to their students about biological evolution and climate science, among other topics.
(Image credit: Listverse / Mike Devlin.)
And this is unfathomable to me. See that creature above? That's a black wolf. Know what's interesting to me about it? The black wolf doesn't occur in nature! The mutation for black fur did not occur until after the domestic dog had been in existence for thousands of years. If ever you see a black wolf, that tells you that at some point in their lineal history, there was a wolf that engaged in breeding with a domestic dog that had that (dominant) black fur mutation.
Biology, of course, doesn't stop with evolution. What I just explained to you is an explanation that requires genetics to understand, which is encoded in an organism's DNA. But before you get to DNA, before you even get to genetics, at a more basic level you must have an understanding of evolution. If you want to understand disease: evolution. If you want to understand whales and dolphins: evolution. (I mean come on, they've got freakin' leg bones!)
(Image credit: retrieved from distraff at selectsmart.com.)
Same deal with global warming; there are plenty of people asserting that the Earth isn't warming anymore (yes, there really are), despite all studies showing that it totally is, if you look at the data without cheating. For example, last year (2011) was "only" the 11th-warmest year on record since records began in 1880. But last year was also a La Niña year, which is characterized by cooler temperatures. It was also the hottest La Niña year of all time, since 1880.
The question I always ask people who dig in even deeper when their view on an issue is challenged by new data is the following: What evidence would it take to change your mind on this issue? For the "Is the Earth continuing to warm" question, you may very well get your wish in 2012 or 2013; one of the next two years could easily become the new warmest-year-on-record.
(Image credit: NASA / GISS global average temperature data.)
Believe it or not, it's actually harder for many of us to admit that we could be wrong about something the less we know about it! Why's that? A neat little psychological effect known as the Dunning-Kruger effect. In a nutshell, it says that people who are incompetent at something (e.g., biology, climate science, etc.) lack the very skills necessary to evaluate the fact that they are incompetent!
This results in people who know almost nothing about a particular topic who are willing to opine at length, argue with experts, and declare -- incorrectly -- that they are right and you are an idiot. Here's the original graph from the original Dunning-Kruger paper, illustrating exactly that.
(Image credit: Justin Kruger and David Dunning, 1999.)
But if we recognize that our present understanding may not be the final answer, and we can absorb that ego-bruise from possibly not being in the right when we thought we were, we can step forward. There are plenty of people working to help make it easier for us all to do exactly that. I'm not exempt from this either, even in areas where my knowledge actually is far above average. Last week, I wrote about when ultramassive stars die, and a number of people challenged some of the contentions I made. Yes, some of them may have been jerks about it, but they also had information that I didn't. Despite being a theoretical astrophysicist, I don't know all there is to know about all aspects of astrophysics, and I never will.
(Image credit: NASA / CXC / M. Weiss.)
So I went out and learned what it was that I didn't know, and now my picture of how supermassive stars die is -- while possibly still imperfect -- improved over what it was. And the next time I go to explain it, there will be at least two things that I can do a better, more accurate job of explaining, and there will be at least one misstep I won't make again.
It doesn't make me any less of a person or any less of a scientist that I didn't get everything right the first time I put it all together; on the contrary, it makes me human. I've been refining what I know and how things make sense to me my entire life, and I'll continue to do that tomorrow. There is no part of that picture of reality that I hold so dear that overwhelming evidence to the contrary couldn't change my mind. I would be surprised at a great number of things, but I wouldn't be stuck.
I know exactly what types of evidence would change my mind about the theories, hypotheses and ideas that make up my world view. Remember the words of Carl Sagan: When you make the finding yourself -- even if you're the last person on Earth to see the light -- you'll never forget it. I hope that I never reach the point where I think I'm always right; I hope I can always gather new information and knowledge, have that crisis when my preconceptions conflict with new data, and admit when I was wrong. Because I don't want to ever stop learning; no matter how much I know, there's always going to be a whole Universe out there to explore.Read the comments on this post...
My Google vanity search for my name and the book titles is really frustratingly spotty, often missing things in major news outlets that I later find by other means. For example, I didn't get a notification about this awesome review in the Guardian, from their children's book section:
I am a ten year old who likes Physics. What is Physics, you might ask! Well, Physics is the science of pretty much everything around you. It asks big questions like where did we come from? How long ago was the Big Bang? Quantum Physics is the part of physics which talks about atomic and sub atomic particles, basically very very small particles. It is a little tricky to understand the behaviour of these particles. So I decided to buy How to Teach Quantum Physics to your Dog. It is an extremely funny book in which Chad Orzel, the writer, teaches his pet dog, Emma, Quantum Physics. Emma loves to chase bunnies and squirrels in the garden, but the problem is that she cannot predict where they will be so they are able to dodge her every time. Now this is also a problem we have in Quantum Physics. So learning Quantum Physics should help Emma catch bunnies...
(The replacement of "Emmy" with "Emma" is a really persistent problem, even among adults, so I just shrug that off. I suspect it's the work of over-zealous copy editors who haven't read the book.)
He goes on to call it "one of the most amazing books I have read." I wonder if I can get that on the jacket? "'One of the most amazing books I have read' -- 'Tintin,' age 10."Read the comments on this post...
Bob Madigan - WTOP's "Man About Town" Broadcasts from a Nifty Fifty Presentation! [USA Science and Engineering Festival: The Blog]
Rockville High School in Rockville, MD was visited by Dr. April Croxton, Marine Biologist from the National Oceanic and Atmospheric Administration (NOAA). Dr. Croxton is one of the AT&T Sponsored Nifty Fifty X 2 Speakers. WTOP's "Man About Town" Bob Madigan was on hand to broadcast Dr. Croxton's presentation and even catch some student comments about this inspiring event.
Listen to WTOP's coverage with Bob Madigan here.
The USA Science & Engineering Festival's AT&T Sponsored Nifty Fifty Program sends more than 100 top scientists and engineers to DC-area schools leading up to the the FREE Expo which will take place at the DC Convention Center on April 28-29. The program has been a huge success this year and we are so grateful to all of our Nifty Fifty Speakers! We believe it is so important for students to hear from real live scientists and engineers to see the potential they can reach with STEM.
We hope to see you at the Festival in 2 weeks!
"If we knew what it was we were doing, it would not be called research, would it?" -Albert Einstein Our galaxy is but one among hundreds of billions in the cosmos, nearly all of which contain supermassive black holes at the center. Ours happens to be "only" a few million times as massive as our Sun, as well as quiet.
(Image credit: ESO, R. Genzel et al. at MPI fur Extraterrestrische Physik.)
In other words, our galaxy's supermassive black hole is behaving right now, by not viciously shooting off high-energy jets of particles and light at some poor, innocent passers-by.
But other galaxies are not so well-behaved.
(Image credit: NASA and the Hubble Heritage Team / STScI / AURA.)
For example, some 53 million light-years away in the Virgo Cluster, the galaxy Messier 87 shoots a jet some 5,000 light-years long out of its central supermassive black hole. This behemoth has the advantage of having a black hole a few billion times as massive as our Sun (rather than a few million), and happens to be in the process of devouring a large amount of matter at the moment.
These supermassive black holes possess some of the strongest and largest magnetic fields in the Universe, and as matter falls in -- whether its from stars, planets, asteroids, gas or dust -- it gets broken apart into individual atoms, which become ionized. Like all charged particles, they get accelerated by these magnetic fields, resulting in, among other things, the intense emission of radiation along the magnetic-axis of the black hole!
Galaxies with these powerful, collimated jets emitted from their central black holes are known as Active Galaxies, and this radiation covers the entire spectrum, from gamma-rays through visible light all the way down to radio frequencies. Nearly always, this radiation comes off in an extremely narrow beam, so that any one particular Active Galactic Nucleus (AGN) is very unlikely to fry us, here on Earth.
(Image credit: NASA / JPL-Caltech.)
But, keep in mind, there are hundreds of billions of galaxies out there in the Universe, and that even with a tiny percentage of them containing active nuclei and an even tinier percentage pointing right at us, it is a very big Universe. And for those of you who've come by here recently, you'll recall that we've just completed surveying the entire Universe in the infrared, imaging -- literally -- hundreds of millions of these galaxies.
(Image credit: NASA / JPL-Caltech / WISE Team / UCLA.)
With the entire sky imaged by the infrared WISE satellite in four wavelengths -- higher energies in blue and lower energies progressing through green and into red -- hotter objects like stars and galaxies should pretty much always show up with a blue or greenish-blue color. Very dusty regions will show up as red or green, as that gas is heated up by stars to be much warmer than the interstellar medium, but still far too cold to give off visible light.
But remember, nearly half of the "points of light" imaged by WISE are galaxies, some of which are active. And every once in a very rare while, these active galaxies have a jet pointed right at us.
(Image credit: NASA / GSFC Conceptual Image Lab.)
These rare but fascinating objects are known as Blazars, because they're "blazing quasars." Normally found with Gamma-Ray telescopes, you wouldn't necessarily think that an infrared telescope would be a great Blazar-finding tool. But Francesco Massaro and his team have done exactly that, with great success. Here's how:
(Image credit: NASA / JPL-Caltech / Kavli.)
With a uniquely flat spectrum across WISE's four color filters, Blazars appear white compared to everything else. Why white? Unlike practically every other point of light in the image, which shows up colored based on the thermal temperature of the emitting objects (hotter appear blue, cooler appear red), the light from Blazars comes from that characteristic radiation of charged particles being accelerated by their black hole's magnetic field: synchrotron radiation! The synchrotron radiation shows up with a roughly equal brightness in all four of WISE's filters, giving it a whitish appearance compared to all other compact object.
These objects are very rare and normally hard-to-find, but because of their unique and easily identifiable appearance to WISE's eyes, more than 200 new blazars have been seen and thousands of old ones confirmed, with estimates that thousands more are in the all-sky image, just waiting to be discovered. This is particularly remarkable, considering that there only are around three thousand known Blazars in the entire Universe! (3,081 as of October, to be more precise.)
(Image credit: Gene Smith's Astronomy Tutorial at UCSD.)
In other words, this infrared satellite could, if we're lucky, wind up doubling the number of known Blazars! As the study's lead author notes: Blazars are extremely rare because it's not too often that a supermassive black hole's jet happens to point towards Earth. We came up with a crazy idea to use WISE's infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped. What an unexpected, serendipitous use for an infrared satellite: as a gold-mine for Blazars, which just happen to be some of the most interesting objects in the Universe.
This is part of the beauty of doing an All-Sky Survey; if you can just learn one new technique for finding/identifying one class of object, you're suddenly going to catch every single one in the Universe that your instrument is sensitive to.
And that's how a simple infrared satellite can capture thousands of the most energetic cosmic cannons in the Universe!Read the comments on this post...
As threatened a little while ago, this is the first of ten hopefully weekly posts looking back at the ten years this blog has been in operation. This one covers the period from the very first post on June 22, 2002 to June 21, 2003.
When I started doing this look back, I was more than a little afraid that it would prove cringe-inducing. It's been ten years, after all, and in that time I've gone from a wet-behind-the-ears, recently married assistant professor to a tenured father of two and a published author. That's enough external change that I was expecting my early posts to seem, well, pretty juvenile.
That wasn't the case, though. I mean, there are some definite changes in the general style of the blog, but all in all I was pleasantly surprised at how well a lot of it held up. Some of the pieces I wrote in the early days are a surprisingly good match to stuff I've written recently on the same topics. Which either means that I've always been brilliant, or that I've plateaued as a writer, I'm not sure which.
The tagline of the blog from the very beginning has been "Physics, Politics, Pop Culture," so I'll use those as headings to organize the recap of noteworthy posts.Read the rest of this post... | Read the comments on this post...
A Night of Celestial Excitement: Join Us April 28 at the Stargazing Party! [USA Science and Engineering Festival: The Blog]
Under the guidance of some of the top astronomy experts in the country, explore our amazing Universe - including up close views of the Earth's moon, Jupiter and other mysterious planetary objects - at the Stargazing Party, an exciting educational collaboration between the Festival, the Smithsonian's National Air & Space Museum (NASM), telescope manufacturer Celestron and other partners, on Saturday, April 28 at NASM in Washington, DC.
A hit with visitors at the inaugural Festival in 2010, the Stargazing Party is returning to the Festival Expo with an equally impressive lineup of evening celestial activities which include Bill Nye the Science Guy in a live recorded broadcast by Planetary Radio with host Mat Kaplan who will inspire other young astronomers to make their own unbelievable discoveries!
In addition, don't miss presentations by such prominent astronomy educators as Drs. Jeffrey Bennett and Jeff Goldstein who will give walking tours of the celebrated Voyage Scale Solar Model System located just outside the NASM and later discuss other fascinating facets of our quest to explore the universe.
Celestron will add hand-on excitement to this night with telescopes set up around NASM's Public Observatory to accommodate visitors' celestial viewing enjoyment.
April 28, 2012- 06:30 PM to 10:30 PM
Smithsonian Institution's National Air and Space Museum on the National Mall
6:30 pm - 7:45 pm: Walking Tours of the Voyage Scale Model Solar System (space is limited, sign up for one of the 3 thirty-minute tours at the museums info desk when you arrive)
7:30 pm: Telescopes ready for viewing around NASM's Public Observatory
7:45 pm: Doors open for Stargazing Party!
8:00 pm: Program in Moving Beyond Earth gallery, including welcome by Bill Nye the Science Guy and remarks by Celestron, and the Planetary Radio Live program
8:10 - 10:20 pm: Check out "Scale of the Universe" and "Human Exploration: the Journey Continues" in Milestones of Flight, plus "Forces of Flight" in How Things Fly, and look for hands-on Discovery Stations throughout the first floor of the Museum!
In it's increasingly bizarre need to inflict it's animal rights morality on everybody, PETA's Ingrid Newkirk has criticized Jennifer Lawrence for scenes in Winter's Bone and the Hunger Games, which show her hunting and eating animals.The actress was dubbed "the coolest chick in Hollywood" by Rolling Stone, and in the magazine's latest issue she recounts her on-screen squirrel-skinning scene in the 2010 movie "Winter's Bone."
"I should say it wasn't real, for PETA. But screw PETA," she told the magazine.
In response to the actress's comment, PETA president Ingrid Newkirk told Gothamist, "[Lawrence] is young and the plight of animals somehow hasn't yet touched her heart. As Henry David Thoreau said, 'The squirrel you kill in jest, dies in earnest.' We are told that this squirrel was hit by a car, but when people kill animals, it is the animals who are 'screwed,' not PETA, and one day I hope she will try to make up for any pain she might have caused any animal who did nothing but try to eke out a humble existence in nature."
Gag me with a spoon. Lawrence's initial instincts were correct. Screw PETA. In these scenes and movies characters are grappling with survival in the face of starvation and poverty. PETA seems to think the appropriate ending for Katniss would have been a moral vegan death from starvation in district 12 rather than being a life-affirming, kickass hunter. And I guess Ree should have morally died from exposure in the Ozarks. The producers bought her a squirrel from a local hunter, and she realistically portrayed the skinning of an animal by hunters for food. I think what really upsets PETA about these portrayals is that they realistically show what humans will do to survive, that hunting and eating animals comes naturally to us, and there's nothing wrong with hunting for food.
Let's hope Lawrence doesn't back down, for some reason I think she won't:The actress, who spent a month in Missouri with a rural family learning to shoot rifles and chop wood in preparation for "Winter's Bone," and was trained by four-time Olympic archer Khatuna Lorig for her role as Katniss in "The Hunger Games," also told Rolling Stone, that when she is done with her next movie she is "thinking about buying a house. And a big dog. And a shotgun."
I'm liking her more and more.Read the comments on this post...
I'm re-instituting the quota system for the moment-- no blogging until I make some substantive progress on the current work-in-progress-- but I'll throw out a quick post here to note a media appearance: Physics World has a podcast about books on quantum physics up today:
Since its inception in the early part of the 20th century, the theory of quantum mechanics has consistently baffled many of the great physicists of our time. But while the ideas of quantum physics are challenging and notoriously weird, they seem to capture the public imagination and hold an enduring appeal. Evidence of this comes in part from the numerous popular-science books that have been written on the topic over the years. This episode in the Physics World books podcast series looks at the popularity of quantum mechanics in science writing.
This features some comments from a telephone interview I did with them, about why I thought it was worth writing yet another book about quantum physics. They also talked with Marcus Chown and Robert Crease, and go a little bit into the great Brian Cox argument.
So, if you've got 20 minutes to kill, check it out.Read the comments on this post...
Perennial Aard favourites N-A. Mörner and B.G. Lind have published another note in a thematically unrelated journal. It's much like the one they snuck past peer review into Geografiska Annaler in 2009 and which Alun Salt and I challenged in 2011. The new paper is as usual completely out of touch with real archaeology, misdating Ales stenar by over 1000 years and comparing it to Stonehenge using the megalithic yard. No mention is made of the fact that this unit of measurement was dreamed up by professor of engineering cum crank archaeoastronomer Alexander Thom and has never had any standing in academic archaeology. The megalithic yard does not exist.
At first I thought, damn, they've managed to game the system again. But then I looked into the thing some more and came to the conclusion that this time, Mörner & Lind have been scammed, poor bastards.
The journal they've published in is named the International Journal of Astronomy and Astrophysics. It's an on-line Open Access quarterly, and though it has an ISSN number for a paper version as well, this is not held by any Swedish library. This may not be cause for suspicion, because the journal is new: its first four issues appeared last year. The Head Editor is professor of astronomy at a young English university that is quite highly ranked within the UK.
So far, it may look like Mörner & Lind have simply published in a low-impact but legit academic venue. But let's have a look at the publishers of IJAA, Scientific Research Publishing (SCIRP). This outfit publishes from Irvine, CA, but its web site is registered in Wuhan, China, where its president Huaibei "Barry" Zhou is based. He is apparently a physicist. According to a 2010 statement by Zhou to Nature News, he co-founded SCIRP in 2006 or 2007. In the five or six years since, the firm has launched over 150 on-line Open Access journals. Uh-oh.
Suspicions about SCIRP began to gather in December 2009, when Improbable Research, the body behind the IgNobel Prize, said the publisher might offer "the world's strangest collection of academic journals". Improbable Research pointed out that at the time, SCIRP's journals were repurposing and republishing decade-old papers from bona-fide journals, sometimes repeating the same old paper in several of its journals, and offering scholars in unrelated fields places on editorial boards.
This was taken up by Nature News in January 2010, when they contacted Zhou and received the explanation that the old papers had appeared on the web site by mistake after having been used to mock up journals for design purposes. "They just set up the website to make it look nice", said Zhou. While he had otherwise represented himself as president of SCIRP, Zhou now told Nature News that he helped to run the journals in a volunteer capacity. The piece reports that SCIRP had listed several scholars on editorial boards without asking them first, in some cases recruiting the names of people in completely irrelevant fields. In other cases, scholars had agreed to join because a SCIRP journal's name was similar to that of a respected publication in their field. Recruitment efforts by e-mail had apparently been intensive and scattershot.
Now, what is this really about? Why is SCIRP cranking out all of these fly-by-night fringe journals that anybody can read for free? The feeling across the web is that it's most likely a scam utilising a new source of income: the "author pays" model built into bona fide Open Access publishing. A kinder way to put it would be that SCIRP is a pseudo-academic vanity press.
Instead of charging a subscription fee, many Open Access journals charge authors a publication fee once their manuscripts have gone through peer review and been accepted. This gets research out of the stranglehold of the big publishing houses (Elsevier et al.), making it available to tax payers and scholars in poor countries. Instead of putting huge money into their libraries to buy expensive journal subscriptions, universities can distribute smaller amounts among their faculty to pay Open Access publication fees.
But Mörner & Lind's new paper has clearly not been vetted by any competent scholar. This suggests that anybody can publish anything in SCIRP's International Journal of Astronomy and Astrophysics as long as they pay the fee. Its Head Editor tells me by e-mail that he is "concerned about the refereeing process and should investigate".
And as for the other 150 SCIRP journals? Well, what can you tell me, Dear Reader?
(SCIRP has a few other lines of business too. One is apparently scam conferences. Beware of the International Conference on Internet Technology and Applications.)
Update 16 April: Michael D. Smith, Professor of Astronomy at the University of Kent, stands by his journal. He wrote me today:I have checked - the article was indeed refereed properly.
I also note that your blog contains many many errors and also draws on selected information taken out of context.
I believe few academics would agree with him regarding the quality of the peer review in this case -- be they astronomers, archaeologists or archaeoastronomers.Read the comments on this post...
"We were left with a picture of part of the sky with no stars or galaxies, but it still had this infrared glow with giant blobs that we think could be the glow from the very first stars." -John Mather When you look out at the night sky, you're limited by the light pollution from your surroundings, the imperfections of our atmosphere, the light-blocking gas and dust throughout the interstellar and intergalactic medium, and the capabilities of your eyes. Still, what one can see is truly a sight to behold.
What if you didn't have those limitations, though?
You could get rid of the light pollution entirely by heading into outer space, where there's no competing light sources to the night sky. You could soar above the atmosphere, where the paths to the stars becomes so pristine that they cease to twinkle. You could even look with infrared cameras instead of your eyes, seeing past the galaxy's light-blocking dust. And if you could do that, for years and years, photographing the entire visible Universe in the infrared from space, you'd be NASA's WISE mission.
(Image credit: NASA / Berkeley Labs, retrieved from here.)
Well, here we are, 2.7 million images, four wavelengths of light and an unbelievable 15 trillion bytes of data later. There have been some great discoveries along the way, but what NASA's gone and put together has literally left me breathless.
Without further ado, here's WISE's view of the entire 360 sky.
(Image credit: NASA / JPL-Caltech / UCLA / WISE team.)
Over half a billion objects were imaged in this survey, including hundreds of millions of stars, hundreds of millions of galaxies, and tens of thousands of asteroids, a large fraction of which had never been seen before.
You can zoom in on the image yourself, download the 170 megapixel version, or just check out some of the highlights I've pulled out, shown side-by-side with their visible light counterparts. Notice, in every case, how different the infrared view (at left) is from what you can see with visible light (on the right). Let's start with Omega Centauri, the largest and most massive globular cluster in the galaxy.
In one of the most coincidental alignments in our part of the Universe, we've got a close, active star forming region just 420 light-years away, known as the Coronet Cluster, paired in the sky with a distant globular cluster, NGC 6723, around 29,000 light years distant! In visible light, the star forming region is all but obscured, but its inner workings are laid bare by the infrared power of WISE!
(Visible light image: retrieved from LowOhm.com.)
But perhaps we need to look outside of our own galaxy to help give a greater perspective; let's look at our small, nearby satellite galaxy, the Small Magellanic Cloud. In visible light, the pink belies the star formation it's undergoing. But with WISE's infrared eyes, you can see so much more than that.
(Image credit: Stéphane Guisard, retrieved from APOD.)
And, perhaps most strikingly, the Andromeda galaxy, the Milky Way's sister and nearest neighbor to us, whose dusty warm gas tracing out its spiral arms is revealed by WISE in a way that visible light -- and our eyes -- can simply not uncover.
(Visible image credit: Jason Ware.)
But most spectacular to me, as you well know, is being able to scroll through the plane of the galaxy. We did it before in visible light here, now hang onto your hats and take a look at our home galaxy, in great detail, in the infrared!
That's the whole Universe, as you'd only be able to see it from outer space, with infrared eyes far superior to those of any living creature! And if you made it all the way down here, perhaps you want one more chance to download the entire infrared sky, courtesy of WISE; enjoy!Read the comments on this post...
A passing mention in last week's post about impostors and underdogs got me thinking about Michael Faraday again, and I went looking for a good biography of him. The last time looked, I didn't find any in electronic form, probably because the Sony Reader store has a lousy selection. I got a Nook for Christmas, though, and this time, Alan Hirshfeld's 2006 biography, The Electric Life of Michael Faraday was right there, so I picked it up and read it over the weekend.
It was a fast read, both because this is a short popular biography-- 250-odd pages-- and because Faraday's life story makes for compelling reading. He was born to a poor family in 1791, and seemed destined for life as a bookbinder, a prospect he found very depressing. While reading manuscripts sent to the shop where he was an apprentice, though, he developed two passions that would shape the rest of his life: a relentless drive for self-improvement, and a deep fascination with science.
Together, these brought him into contact with Sir Humphrey Davy, one of the stars of British science at that time, and through a great stroke of luck, Faraday managed to get hired on as Humphrey's assistant and sometimes valet. And the rest, as they say, is history: his incredible gift for experimental science quickly made him an essential part of the Royal Institution, where he worked for the remainder of his life, and where he made essential contributions to physics, chemistry, and materials science, among others. Faraday was famously one of three scientists whose portrait Einstein kept in his office (the others were Newton and Maxwell), and Hirshfeld does a nice job of laying out the discoveries that justified that high regard.Read the rest of this post... | Read the comments on this post...
"Science, Danger, and Progress" a Talk by Featured Author William Gurstelle [USA Science and Engineering Festival: The Blog]
The USA Science and Engineering Festival will really heat up when Popular Science and Make Magazine writer William Gurstelle speaks at the Family/Hands-on Science Stage on Sunday morning. Gurstelle, who wrote the bestselling DIY science book Backyard Ballistics, will be reading from his newest book, The Practical Pyromaniac. The book is a hands-on guidebook to playing with fire and narrates the story of humankind's long-coming understanding of the most important chemical reaction on the planet.
In addition to his talk, William will join a number of other well-known science authors including Homer Hickam, Theo Gray, and Robin Cook for a panel discussion on Saturday night to discuss how current science writing is reinvigorating interest in the sciences among young people. The Featured Author Panel Discussion "Science Stories in Society & School: Using Narrative to Bridge the Gap" will take place at 8 pm at the George Washington University Lisner Auditorium. Click here for free tickets to this event.
William's Sunday morning's talk is entitled "Science, Danger, and Progress". The three decade period preceding the year 1800 was a time of incredible scientific progress. Led by scientists such as Benjamin Franklin, John Dalton, Henry Cavendish, Joseph Priestly, and Antoine Lavoisier, the understanding of the physical world radically changed. The old theories of nature - the four elements, alchemy, and phlogiston, among others - were swept aside and new scientific understanding based on real chemistry and physics took hold. These men - The Practical Pyromaniacs - led lives filled with science, danger, and progress.Read the comments on this post...