Science Blogs Physcial Sciences
Over in Twitterland, we have a question from WillyB:
If you had to pick one topic to cover in Physics, which do you think is the most important for the gen. public?
This sounds like a job for the Internet! To the polling machine!
While several of the options allow linear superpositions of solutions, this is a purely classical poll, so you may choose only one answer. Though you should, of course, feel free to bitch about the choices in the comments.Read the comments on this post...
The Festival Expo Map is Ready to View! Start Planning for Your Festival Weekend Today! [USA Science and Engineering Festival: The Blog]
We are excited to share the news that the 2012 USA Science & Engineering Festival Expo Map is out! The Festival will run from 10:00 AM to 6:00 PM on Saturday, April 28th and from 10:00 AM to 4:00 PM on Sunday, April 29th. We will also host free evening shows including the Stargazing Party and our Featured Author Panel Discussion both on Saturday night. The "Largest Celebration of Science" will take place this year in Washington, DC at the Walter E. Washington Convention Center.
The Festival is packed with entertainment for the whole family with 3,000 exhibits and over 150 stage shows. We are thrilled to offer extraordinary hands on activities at the exhibits plus an amazing line up of science celebrities and authors will fill our Festival stages! We have finalized all of the presentation show dates, times and stages so that you may plan ahead to make your Festival experience that much more enjoyable.
Do you want to be entertained by the famous duo Adam Savage and Jamie Hyneman from The Mythbusters? Check them out on Saturday afternoon at 1:00 on the Curie Stage. Are you a fan of Bill Nye the Science Guy? You can see Bill Nye on Saturday afternoon at 3:30 on the Curie Stage. You can have the experience of a lifetime listening to the incredible innovators Elon Musk, George Whitesides and Richard Garriott early Saturday evening at 5:00 also on the Curie Stage. The Icons Legend will help you to choose the stage shows to explore with symbols such as little kids, explosive, music, celebrity and magic!
Our Book Fair stages have been categorized by genre including Teen Non Fiction, Family Science and Hands on Science. Take a look at the map to plan out which Featured Author Presentations with free book signings you would like to visit such as bestselling author of Crater, Homer Hickam or Physicist and author of Knocking on Heaven's Door, Lisa Randall.
Traveling to the Festival with young children? Be sure to visit our very own replica of the Magic School Bus featuring character actresses playing Ms. Frizzle. PBS Kids will also be at the Festival to thrill your budding scientists! And you cannot miss the 2012 National Robot Fest & DIY Expo located in Hall B! Our Meet the Scientists/Engineers in the Career Pavilion is a great place for high school students to explore various careers in science and engineering. Every hour students can conduct in-person interviews with scientists and engineers from different disciplines.
Our map legend makes it simple for you to explore the Festival with symbols for exhibits, stage shows, first aid stations, restrooms and numbers for our major exhibitors. You can also collect your "Festival Stamps" on the Expo Map. Collect stamps when you complete at least 10 exhibits from any of the thematic tracks and then visit the National Academics Exhibit to enter a prize drawing!Read the comments on this post...
"...the publisher wouldn't let us call it the Goddamn Particle, though that might be a more appropriate title, given its villainous nature and the expense it is causing."
-Leon Lederman, author of The God Particle The Higgs Boson: you know the deal. It's the last undiscovered particle in our current picture of all the fundamental particles in the Universe.
(Image credit: Fermilab, retrieved from here.)
If we can find it, we'll either have a big clue as to what the next step to take in physics will be, or we'll be forced to admit that physics works too well, and many of the great hypotheses (supersymmetry, large extra dimensions, etc.) are highly unlikely to be within our reach. It all depends -- if we find it -- on what its properties are.
So how do we go about finding it? We accelerate particles to the highest energies we've ever reached on Earth, smash them into one another at strategic collision points, and observe the debris that results.
(Image credit: CERN / Particle Physics for Scottish Schools.)
These collisions are so frequent at the Large Hadron Collider, numbering about 600 million per second, that we couldn't possibly record them all. Instead, what we do is look for exotic signals, or signals that have quickly measurable indicators that something interesting may be going on, and only record those. This is vital, because each collision shows up looking like this in one of the two main detectors.
(Image credit: AP Photo / CERN / CMS, retrieved from CBS news.)
So what particle physicists looking at this do is try to reconstruct, based on what's showing up in the detector, what was created when these collisions occurred. The difficulty of this is mind-boggling; it makes blood-spatter analysis look like child's play.
We can actually do this, and determine what particles came from what locations with a specific energy at a specific time, for pretty much everything (except neutrinos) that are produced! This is important, because depending on what mass of the Higgs Boson is, and whether it's a normal, standard-model Higgs or something more exciting, the Higgs should decay into different particles of a given energy.
(Image credit: Fermilab's "Higgs Missing Report".)
So when we reconstruct that there were bottom-antibottom quarks leaving a collision, that's interesting. When we see two high-energy photons, that's interesting. When we see a tau-antitau pair, that's interesting, too. And so on.
But the Higgs isn't the only thing that produces those particles. In fact, many other things produce those particles. The big question -- and the reason finding the Higgs is so difficult -- is that we have to figure out how much. It's what makes physics so powerful, the fact that we're a quantitative science. And you may have seen the ATLAS results here just a few months ago, where their combined data provided some very suggestive evidence of a Higgs boson at about 126 GeV/c2.
(Image credit: Fabiola Gianotti for the ATLAS collaboration / CERN.)
The best signal, as you can see in red, comes from looking at what appears to be a Higgs Boson decaying into two photons.
But what does that mean? Where does that graph come from? Well, I don't need to describe it, when the cover of one of last month's issues of Physical Review Letters can show you!
(Image credit: G. Aad et al. for the ATLAS collaboration.)
What this graph is showing you is, with the black data points, the data observed by the ATLAS experiment. This is contrasted with the (red line) theoretical prediction of all the known particles and interactions of the standard model, excepting the Higgs. A deviation from that red line indicates either an experimental fluctuation or some type of new physics.
Let's go in for a closer inspection, with some annotations (in blue) by me.
A visual inspection clearly shows the excess of data peaked at around 125 GeV/c2, but that's hardly an incredibly convincing graph! It should clearly show you why we say we need to take more data before we have successfully convinced ourselves that this is new physics and not simply a fluctuation. The degree of statistical significance we require in this discipline to announce a discovery is five standard deviations; on its own, this study -- the best individual channel searching for the Higgs Boson -- doesn't even reach three.
But this is why we're increasing the energy of the beam, taking more data, and trying to establish exactly what is and what isn't a fluctuation.
And if we can get the data to say that with some degree of certainty, "there is some new physics here," the next step is to ask whether it's a standard model Higgs Boson or not. Because it might be simply be a standard model Higgs Boson at ~125 GeV/c2, and there might not be any new physics beyond that -- in the world-case scenario -- all the way up to the Planck scale! (Of 1019 GeV!)
(Image credit: P. P. Giardino et al, as is the next image.)
If this is the case, we should see a specific excess of signals at an energy corresponding to the Higgs Boson's mass in each channel: bottom-antibottom quarks, two photons, a tau-antitau pair, W-bosons, Z-bosons, etc.
If you take a look at the error bars on the graph, above, you'll see that we are way more likely to wind up on the green line (Standard Model Higgs) than the red line (no new physics), but we may also wind up in... well... a weird place! What do I mean by weird? I mean that the thing we find may not be the Higgs Boson we're looking for, or it may not be a Higgs Boson at all.
What we see, so far, is consistent with a Standard Model Higgs Boson, but that is by no means the only (or, arguably, even the best) interpretation. If I were a betting man, the Standard Model Higgs Boson is what *I* would bet on, but it isn't the only possibility, and we need to take more data to be able to decide.
So be patient. This is how we do science, and this is what it takes to get it right. Above all else, we should all be ecstatic to see that the science is being done properly here; we owe it to everyone doing their job correctly to give them the time to do it right.Read the comments on this post...
Kavli Science Video Contest Top 20 Finalists Have Been Selected- Now Who will Win the "People's Choice" Vote? [USA Science and Engineering Festival: The Blog]
The Kavli Science Video Contest has wrapped up with over 260 entries! Now its time for the People's Choice Vote, in advance of the awards ceremony on April 29, in Washington, DC, as part of the USA Science & Engineering Festival. People's Choice Voting begins April 2 and closes April 13. Voting is easy, just view the videos on YouTube and click 'like" for your favorites. Click here to view the videos.
We will be highlighting the Top 20 Finalists on our blog for the next two weeks. In today's blog get to know the first five of the top 20 Finalists:
SPOTLIGHT ON KAVLI VIDEO CONTEST: TOP 20 FINALISTS
Entrant: Rachit Agarwal, 14
Entry: "Rachit Robot"
Where do you go to school? Roberto Clemente Middle School, Germantown, MD
What are your favorite subjects? Computer Science and Science
Can you tell us what inspired you to make this video? My passion for robotics and scientific curiosity to solve problems
What do you want to study in college? Engineering & Business
Which college? MIT, Stanford, or Harvard
What kind of career do you want to pursue? Engineering Entrepreneur
Entrant: Cameron Quon, 17
Entry: "Solar Power, Saving With Solar
Where do you go to school? Saugus High School in Santa Clarita, California
What are your favorite subjects? TV Production, Science, Math, and English
Can you tell us what inspired you to make this video? 10 of the schools in our district began putting up solar panels over our parking lots this year. Creating a video relating to science and engineering seemed to fit perfectly with this project.
What do you want to study in college? I want to major in broadcast journalism as a pre-med.
What kind of career do you want to pursue?
I want to combine my love for broadcast journalism, my avid interest in medicine, my excitement for traveling abroad, and my love for Jesus into a career as a medical news-correspondent/broadcast-journalist with an active medical practice. I yearn to open the eyes of the world through the eye of the lens.
Entrants: Kevin Liberman,17 Anna Spitz, 17, Amit Silverstein,18, Alex Neiman, 16
Entry: "Saving the World"
Where do you go to school? Tarbut V' Torah (TVT) in Irvine, California
What are your favorite subjects? Math , Physics, Engineering
Can you tell us what inspired you to make this video? I wanted to make a video about promoting alternative fuels because I envision that it will play a large role in making our lives greener and better. (Alex) To help the environment and help our school's engineering club (Anna) I want to help make others aware of possible solutions to our environmental challenges.( Amit) I am passionate about automobiles, alternative fuels and, as a future engineer, I want to make a difference in this world. That is why I enrolled in AP Environmental Science, started a Science and Engineering club at my school, and recruited my friends to make this video with me. I hope you enjoy it! ( Alex)
What kind of career(s) do you want to pursue? Engineering (ALL)
Entrant: Kyle Davis, 17
Entry: Saving the World
Where do you go to school? Oakleaf High School, Orange Park, FL
What are your favorite subjects? Environmental Science, 3D animation
Can you tell us what inspired you to make this video? A movie not out yet called "Chasing Ice" a documentary about ice caps melting and I felt like I could really get the word out through this video contest.
Which college? Full Sail University to study 3-D computer animation
Entrant: Sreya Vangara, 12
Entry: Nuclear Fusion
Where do you go to school? Roberto Clemente Middle School, Germantown, MD
What are your favorite subjects? Science, Math, English, Spanish, Computer Science
Can you tell us what inspired you to make this video? I actually came across this contest while checking out a link to the U.S. Sci. Festival that my science teacher gave to me. We are actually going to the festival on a field trip. I decided to enter the contest, but didn't know what to make the video on. Later, while I was working on a science project on Nuclear Fusion, I decided to make my video on Nuclear Fusion. I mean, why not? I could get my video and project research done at the same time! I went through a lot of trial and error getting the soundtrack (voice) in. But it was worth it!!! I actually had fun doing it! Of course, science is fun...
What do you want to study in college? I want to major in Computer Science, Science (physics), and Math. I really love science! I also want to learn lots of foreign languages so I can travel the world and be a member of UN (I'm on my way! English, Telugu, and some of Spanish down! ) Or, I will major in law so I can be president when I grow up (my dream!) The first woman (and Indian) president.
Thank you to all of the entries for the 2012 Kavli Foundation "Save the World Through Science & Engineering" Video Contest!!
Read the comments on this post...
June 22, 2012 will mark the tenth anniversary of the founding of this blog. While I would like to one day be famous enough to be able to staple together a collection of loosely related blog posts and call it a book, I'm not there yet. This particular arbitrary numerical signifier does, however, seem worth some commemoration. Also, while I have some idea of how the site has evolved over the last ten years, it's been a slow process, so I thought it would be interesting to troll back through the archives and see how things used to be.
Next Friday, appropriately enough the 13th, will be exactly ten weeks short of the ten-year anniversary. So, my vague plan (more of an aspirational goal, really) is to go back through the archives, starting with the original blogger site and highlight some of the most notable stuff from each year of this blog's existence each of the next ten Fridays.
So, why am I mentioning this today, which is not a Friday, in a post which does not contain any outstanding historical bloggage? Well, for one thing, most of my mental processing cycles are currently taken up by unpleasant stuff that I can't blog, but can't stop thinking about. More importantly, though, there's a vast amount of material here, and to go through it quickly will require a lot of skimming, and I might miss some stuff.
So, consider this post both notice of the upcoming series of posts, and also an open forum to suggest things from this blog's past that I ought to keep an eye out for. If there's an old post that you particularly liked, leave a URL in the comments; if there's something you sorta-kinda remember, leave a description and I'll try to find it as I go through old stuff.
And if any publishing types out there would like to buy a shaggy best-of collection of blog posts by a physics professor and midlist-y pop-science writer, email me, and we can talk....Read the comments on this post...
Every other year NASA conducts a Senior Review of its astrophysics missions that have completed their nominal mission and are requesting an extension of their mission.
The 2012 review panel just reported.Read the rest of this post... | Read the comments on this post...
A Confusing Light OPERA: How Does a Loose Fiber Optic Cable Cause a Signal Delay? [Uncertain Principles]
So, the infamous OPERA result for neutrino speeds seems to be conclusively disproven, traced to a problem with a timing signal. Matt Strassler has a very nice explanation of the test that shows that the whole thing can almost certainly be traced to a timing error that cropped up in 2008. This problem is generally described as resulting from a "loose fiber optic cable," and Matthew Francis's reaction is fairly typical
The main culprit was a fiber optic cable that was slightly out of alignment. This is not quite a "loose wire", as it sometimes has been described: it's far more subtle and harder to check than that, but it's still fundamentally a simple technical problem. (My prediction that the effect was due to something really subtle turns out not to be correct!)
As a professional Optics Guy, I would beg to differ a little. Assuming that this hasn't been garbled by some sort of translation issue, this really is something subtle and surprising (albeit in a technical way, not a new physics way). You wouldn't generally expect to get a significant timing delay from a loose fiber optic connector, because of the way that fiber optics work, which is fundamentally different than the way ordinary electrical cables work.Read the rest of this post... | Read the comments on this post...
One of my favorite bloggers, Dana Hunter, who blogs with me at FTB.com, is now also blogging at Scientific American at a new blog called Rosetta Stones.I was five years old, and Mount St. Helens was busy erupting all over my teevee. I made it a get well card. It looked like it hurt. Thus began an ongoing conversation between me and objects people tend to think of as inanimate until they explode, rip apart, or fall down. Read the comments on this post...
In comments to yesterday's post, Andrew G asked:
Speaking of writing, is there an errata list somewhere for "How to teach relativity to your dog"?
No, but there probably should be. I believe there's an error in one of Maxwell's equations (an incorrect sign, though you should've seen the first typeset version...), but given the length and complexity of the book, there are almost certainly other mistakes. So, if you've spotted an error, in physics, grammar, or anything else, leave a comment here, and I'll compile a list of things to fix if we ever get the chance.Read the comments on this post...
Is poetry a driving force of Oceanography?
- Phillipe Diolé
I've written many times, although not recently, about the ocean.
When I first began Universe in 2005, it was practically a ship's log: meandering pieces on narwhal tusks, the accidental poetics of my hero, Rachel Carson, and adolescent screeds on the perils of the Mariana trench. At some point in my career, I ported my energies outward to the cosmos, reasoning, as the ancient alchemists did, that "As Above, So Below."
The movement from the deep to the distant, from sea to space, seemed like a sensible evolution. I saw parallels then, as I do now. They are both cold, forbidding, strange, contain tremulous mysteries, and do not give their secrets readily. Tales of their early exploration contain feats of unspeakable audacity, as well as tragedy. Solitary heroes stand out: Yuri Gagarin in his Vostok spacecraft, Jacques Cousteau developing the Aqua-Lung in order to push deeper underwater, the elite few men and women who have dared venture far above, far below. Listen to a veteran diver discuss the sea and an astronaut space: you'll hear the same hushed tones, the same fearful, learned respect.
After all, what experience does this planet offer us more phenomenologically similar to spacewalking than floating in a deep ocean? Water is the best environment for spacewalk training on Earth; substituting neutral buoyancy for microgravity, NASA Astronauts train at the Neutral Buoyancy Lab in Houston, a giant swimming pool. I've always been delighted by images of this place; if you squint just right, and ignore the scuba divers, it almost looks like outer space is robin's egg blue and dotted with bubbles.
In spite of our egotism, the human organism is delicate. We're only built to tromp around the accommodating portions of the Earth. The moment we're submerged in the ocean, or we ascend too high a peak—to say nothing of outer space—we're out of our league. Yet, in our incorrigible hubris, we've long used technology to wander beyond our territory. Aristotle wrote of diving bells, and (apocryphally) even Alexander the Great explored the deep ocean—in a submarine of white glass, where the fish gathered 'round to pay homage—and returned to pronounce of his experience, "the world is damned and lost." Mercury spacecraft and the early Soviet Vostok capsules may as well have been diving bells; they were so small, it's said that they were worn, not ridden.
"The sea," Captain Nemo pronounces, in one of literature's more glamorous depictions of the deep, 20,000 Leagues Under The Sea, "does not belong to despots. Upon its surface men can still excercise unjust laws, fight, tear one another to pieces, and can be carried away with terrestrial horrors. But at thirty feet below its level, their reign ceases, their influence is quenched, and their power disappears. Ah! Sir, live—live in the bosom of the waters! There only is independence! There I recognise no masters! There I am free!"
This sentiment, an inverted Overview Effect, sounds familiar. Astronauts consistently speak of the irrelevance of borders, even nations, on a planet viewed from space. It's probably the most consistent revelation of spaceflight, the majestic panorama of a whole planet, seen without its despots and ideologues. The Soviet cosmonaut Gherman Titov, only the second man in space and the first to be there for more than 24 hours, described the experience of seeing the Earth from space as "a thousand times more beautiful than anything I could have imagined." After orbiting the planet over a dozen times, Titov replied a call from mission control with the elated cry: "I am Eagle! I am Eagle!"
An Eagle, of course, has no masters.
Today, in cramped cockpits and bathyspheres, astronauts and their aquatic counterparts lie contorted in the same metal cabins, surrounded by death, peering from thick windows into empty, hostile landscapes. Cloaked in metal, they transport light where there has never been any—to what James Cameron, after his much-ballyhooed recent dive to the Challenger Deep, called a "barren, desolate lunar plain," or (more viscerally) which William Beebe, passenger in the world's first bathysphere, described as "the black pit-mouth of hell itself."
This "black pit-mouth" is what interests me. Essentially every culture has a mythological history which includes primal undifferentiated formlessness. The abyss, as much topless as it is bottomless. And the abyss, figuratively speaking, is neither distinctly maritime nor interplanetary. Rather, it's a little of both: Tao, the primal ocean upon which Vishnu slumbered, amorphous being, chaos preceding time. Is this because the ancients knew on a symbolic level what our scientists empirically know now: that the abyss—in both worldly forms—is the seat of our lineage? We are, as Carl Sagan said, "made of starstuff." We're also risen from the sea. The salt in our veins is testament.
Beebe, one of the greatest American explorers, in his book Half-Mile Down, a record of his dive to 3,028 feet in 1934, wrote that it seems "a very wonderful thing, to walk about on land today, vitalized by a bit of the ancient seas swirling through our body. It is somehow of a piece with stars and time and space-something to be very quiet and thoughtful about, and proud of." Indeed, while beneath the waters lies a cruel landscape, and while the cosmos is vast and unforgiving, they are both our birthright. Our impulse to travel far below and above our limits is precisely that of children striving to return to the womb, only to discover that birth is as great a nothingness as death.
Between coral/Silent eel/Silver swordfish
I can't really feel or dream down here
Further Reading:Read the comments on this post...
Here are some excerpts from the introductory sections of the very first drafts of some book chapters:
[BLAH, BLAH, BLAHBITTY BLAH]
[Introductory blather goes here]
Blah, blah, stuff, blather.
There's a good reason for this, based on the basics of scientific writing, namely that the Introduction should give the reader a rough guide to the complete work-- exactly what you're going to say, before you go on and say it. In order to do a good job with the Introduction, you need to have a very solid idea of the shape of the finished product, and exactly what you need to mention up front for everything to hold together.
Which is why the Introduction is pretty much the last section I write. If you try to write it first, you're setting yourself up for a miserable slog, because you don't know just what you need to say in that section, and so you end up typing and retyping the same vague blather over and over, or frittering away hours on researching stuff that you may or may not actually need, because you don't know yet whether it will be relevant to the whole thing.
That's my advice for anyone setting out to write non-fiction, whether it's a term paper, a research article for a journal, a grant application (OK, that might be stretching the term "non-fiction" a bit...), or a pop-science book: Write the Introduction last.Read the rest of this post... | Read the comments on this post...
"A galaxy is composed of gas and dust and stars - billions upon billions of stars."
-Carl Sagan Perhaps the most striking feature of the night sky under truly dark conditions isn't the canopy of those thousands of points of light, but rather the expanse of the Milky Way, streaking across the entire night sky.
(Image credit: Richard Payne, retrieved from here.)
With an estimated 200-400 billion stars contained within our island Universe, the Milky Way is just a regular, run-of-the-mill spiral galaxy compared to the rest of what's out there.
But it's our home. And, despite the tremendous difficulty associated with resolving the individual stars within it, we've been trying to do exactly that since the first modern astronomers took to the skies with their telescopes.
For the first time ever, we've finally gotten up to over one billion stars identified, and stitched together into a single image.
(Image credit: Mike Read (WFAU), UKIDSS/GPS and VVV, as are all images below.)
The European Southern Observatory's VISTA telescope, combined with the UK's Infrared Telescope in Hawaii, have combined forces to create the VISTA Data Flow System project, where the telescopes have been recording up to -- get this -- 1.4 Terabytes of data, per night, which they plan to do for a total of ten years.
This release comes just a fraction of the way into that time, but there have been over a billion stars identified in the space measured, above. Let's zoom into that white box, in the region on the left of the image above, to get a closer, higher-resolution look. (As always, click for the larger version.)
This small fraction of the galaxy contains more than we could possibly count, or even show at this resolution, so let's go in even deeper, to the tiny region indicated by the box above. What do we find, looking at one of the Milky Way's tiny, active star-forming regions?
Over 10,000 stars, in a region far away in the outskirts of the galaxy. For comparison, we could have taken a look towards the galactic center. The dense chaos should provide you with a stark contrast to the image of the outskirts, and should truly help you understand how we get to a billion so quickly!
The incredibly brave (and patient) among you can attempt to download the stitched-together giant TIFF file (which is what I used -- with a lot of patience -- to create the images above and below), but even this huge 150 Megapixel image can't possibly contain all of the data taken by VISTA Data Flow System.
After ten years, we should have somewhere -- depending on clouds -- around a 5 Petabyte image archive of the Milky Way, a literal treasure trove for astronomers. In the meantime, I've flipped the Milky Way on its side, and created one image, viewable below, where you can view nearly the entire stretch of our home galaxy in one convenient scroll. Take your time and enjoy it.
As you look at this magnificent image, as you marvel that we've passed the milestone of counting up one billion stars in our galaxy, keep in mind that this is still less than 1% of the stars in just one galaxy out of hundreds of billions in the Universe.
And all the same, this is home.Read the comments on this post...
Steve Hsu has a post comparing his hand-drawn diagrams to computer-generated ones that a journal asked for instead:
He's got a pretty decent case that the hand-drawn versions are better. Though a bit more work with the graphics software could make the computer ones better.
This reminded me, though, of something I've always found interesting about scientific publishing, namely the evolution in the use of figures through the years. Whenever I need to do literature searching, I always suspect you could guess the approximate date of a paper's publication by looking at the figures.
If you go back far enough, reproducing figures was a very difficult process, so there tend to be relatively few of them. What figures you do get, though, are exquisite:Read the rest of this post... | Read the comments on this post...
"[The black hole] teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as 'sacred,' as immutable, are anything but."
-John A. Wheeler To an astronomer on any other world, the most important object in our Solar System wouldn't be the Earth, but rather our Sun. Just one example of the hundreds of billions of stars in our galaxy, our Sun is a G-type star, burning at around 6,000 Kelvin and with a lifetime of around 10 billion years.
But stars come in a great variety of masses, sizes, temperatures and lifetimes.
(Image credit: user Kieff, retrieved from wikipedia.)
Although they are the rarest type of stars, the bright blue O and B stars are perhaps the most spectacular in all of existence. With masses reaching, twenty, fifty, or even hundreds of times the mass of our Sun, these stars burn hotter and faster than our Sun ever could. Emitting energy often at rates in excess of 100,000 times our Sun's, and frequently living for less than even one million years, these stars build up massive cores through nuclear fusion, and then have no choice but to collapse under the irresistible force of gravity.
Not, mind you, to contract into a white dwarf star, like our Sun will, but to destroy the individual atoms making up the star itself. In the most extreme cases, the stellar corpse will collapse into a black hole: an object so dense not even light itself can escape from it.
(Image credit: NASA / CXC / M. Weiss, retrieved from Discover.)
On its own, you'd probably never even know a black hole like this existed, given the fact that it's likely going to be thousands of light years away. But every once in a while, we get lucky.
If a black hole happens to have a binary companion -- particularly a large-sized binary companion -- it can steal some of the mass from this much less dense star. When it does so, it not only forms an accretion disk around the black hole, but the matter can get accelerated by the black hole's powerful magnetic fields, and shot out in a pair of jets, perpendicular to the disk, moving in opposite directions.
(Image credit: European Space Agency, retrieved from here.)
This acceleration, like all charged particles accelerated by magnetic fields, will cause the emission of light. Not visible light, mind you, but in the case of black holes, powerful X-ray light.
In our own galaxy and very nearby, we've detected a few black holes like this, where the mass of the black hole is only a few times the mass of our Sun. For example, GRO J0422+32, for which an artist's impression is shown, above, has a black hole maybe 10 times the mass of the Sun, and is located about 8,000 light-years away.
One characteristic of these little black holes is that these powerful X-ray sources emit their energy in great bursts, which die down after a few years to become incredibly quiet. The other types of black hole -- the supermassive ones at the centers of galaxies -- do not do this at all!
Centaurus A, located about 11 million light years away, is a giant elliptical galaxy with an unusual dust lane in it. It's also one of the closest active galaxies to us, with two radio jets extending for about a million light years in space, moving at speeds of about half the speed of light in the innermost regions. Needless to say, with this kind of power behind it and a supermassive black hole that's many millions of times the mass of our Sun, these X-ray emissions aren't going anywhere for quite some time.
But a much smaller black hole -- even though it would be much less luminous to X-ray eyes -- can have its intensity drop by a factor of hundreds or even thousands within just a single year, if you happen to be watching at the right time. So far, we've found many stellar-mass-scale black holes this way, but nearly all of them have been within our own galaxy, and none of them have been as far away as Centaurus A.
But let's take a look at Centaurus A itself, in the X-ray.
Yes, the central, supermassive black hole and its jets are easily the most prominent feature in this image, but there are other bright X-ray sources, too. So you don't just look at it once, you look at it many times, separated by long periods of time! What did we find when we did exactly that? The team used the orbiting Chandra X-ray observatory to make six 100,000-second long exposures of Centaurus A, detecting an object with 50,000 times the X-ray brightness of our Sun. A month later, it had dimmed by more than a factor of 10 and then later by a factor of more than 100, so became undetectable.
(Image credit: NASA/Chandra, retrieved from here.)
That would be this object, above. It makes you wonder, of course, what all of these other bright X-ray sources are! Are they also small-ish black holes, ready to drop off in brightness as soon as their fuel is spent? Or are they more robust, long-lasting objects?
But make no mistake, this object just became the most distant, stellar-mass black hole ever discovered! Want some more proof? Take a look at this 2001 X-ray image of Centaurus A, and notice a very suspiciously missing point of light!
(Image credit: NASA/SAO/R.Kraft et al.)
So, if you want to know where the first stellar-mass black hole located more than 10 million light-years from Earth is, it's right here!
Now, that's what I call a little black hole going a long way!Read the comments on this post...
This post was written by Brookhaven Lab science writer Justin Eure.
Imagine looking in the mirror and finding your familiar face reflected back as you've always known it. But as you look more closely, as you precisely examine that mirror image, subtle distortions emerge. The glass itself remains flawless, but real and fundamental differences exist between you and the face that lives on the other side of the looking glass.
Something similar happens in the quantum world when matter is examined against its exotic reflection: antimatter. The analogy is admittedly fanciful, but it's no more dramatic than the dynamics of these almost-twins, which annihilate one another on contact.
Elegance and simplicity suggest that during the Big Bang there were equal numbers of particles and antiparticles - a kind of balanced pure energy. But in reality, we live in a curiously lopsided universe, one in which matter reigns supreme. So what happened? Understanding the mechanism behind that cosmic preference remains one of the great puzzles in science, and physicists are closer than ever to tunneling through the looking glass to seek out the answers.
A new landmark calculation executed by an international team of physicists employed unparalleled experimental results and advanced supercomputers to reveal more about just how and why some fundamental symmetry breaks.Read the rest of this post... | Read the comments on this post...
What are we looking at here? Your answer will depend on the angle with which you approach the problem.
hat tip: Sarah Moglia.Read the comments on this post...
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Many of the Hubble Space Telescope images have never been looked at.
You can now browse the archives and win valuable prizes for finding cool new pics.
"Think binary. When matter meets antimatter, both vanish, into pure energy. But both existed; I mean, there was a condition we'll call 'existence.' Think of one and minus one. Together they add up to zero, nothing, nada, niente, right? Picture them together, then picture them separating--peeling apart. ... Now you have something, you have two somethings, where once you had nothing." -John Updike Looking out at our Universe, at the myriad of stars, galaxies, and, well, "stuff" in our Universe, it's hard not to ask yourself where it all came from.
When we look out at the Universe, each point of light that's out there, whether a planet, star, galaxy, cluster of galaxies or something even bigger, contains the entire history of the Universe as part of its story.
There's a great cosmic spider-web of structure that's traced out by the galaxies in the Universe, with each pixel of light representing the location of a single galaxy.
(Image credit: 2dF Galaxy Redshift Survey.)
When we consider our Universe, sure, it's full of dark matter and dark energy; that's how you make the structure we observe today. Even if we allowed ourselves to modify the laws of General Relativity, there's simply no other way to reproduce/recreate the Universe we have today.
Looking at the matchup between simulations and observations, the cosmic web of great clusters, filaments and empty voids fills the entire modern Universe.
(Video credit: V. Springel et al. (2005), Millenium Simulation.)
How did they get there? It took the billions of years the Universe has been around, the irresistible force of gravity, and the runaway growth of structure in the expanding Universe to bring it all together.
The beautiful simulation below, by Ralf Kähler, scales out the expansion of the Universe so that we can visualize just how matter -- both normal and dark -- collapses over time into galaxies, filaments and clusters.
(Visualization: Ralf Kähler and Tom Abel; Simulation: Oliver Hahn and Tom Abel (KIPAC).)
But it's the normal matter -- the protons, neutrons, and electrons -- that produce the visible light we pick up with our telescopes. The stars and galaxies that we see are all, as best as we can tell, made out of normal matter. And yet, this, itself, is a puzzle.
Because the laws of physics don't allow you to create or destroy matter without also creating or destroying an equal amount of antimatter!
(Image credit: Addison-Wesley, retrieved from J. Imamura / U. of Oregon.)
At least, this is true experimentally and observationally. But it couldn't always have been true, otherwise the Universe would have an equal amount of antimatter in it to the matter that's present.
And it doesn't. In fact, if there were an equal amount of antimatter created to the amount of matter we presently have in the Universe, the Universe would be so sparsely populated that there'd only be about one subatomic particle per cubic kilometer.
It would be less than one-billionth as dense as the Universe we have today.
So let's go back to the very early stages of the Universe, when it was filled with a hot, dense plasma, with equal amounts of matter and antimatter, and see if we can't make the Universe we have today.
(Image credit: me, background by Christoph Schaefer.)
Against the background of this hot, dense, fully ionized plasma, an equal quantity of particles and antiparticle flit back-and-forth. They collide with one another, annihilating, while other particles, like photons, interact with one another, producing equal amounts of matter and antimatter when they do.
If the Universe were of a constant size, a constant temperature, and all the particles and antiparticles in it were stable, it would be impossible to create more matter than antimatter, or vice versa. But in our Universe, none of those things are true!
(Image credit: Ben Moore, retrieved from N. Abrams and J. Primack.)
The Universe is expanding and cooling, and what this means is that -- when the temperature drops below a certain point -- you can no longer create matter/antimatter pairs as quickly as you destroy them! Why's that? Because E = mc2, and once the energy of your Universe drops below the mass necessary to create the particles/antiparticles you're looking to make, the ones that already exist simply go away.
How do they go away? They annihilate away, as only matter and antimatter can. But as they do, it gets more and more difficult for the matter and antimatter particles to find one another. Because the Universe is expanding, the density is dropping, and these particles/antiparticles are disappearing, you reach a point where they can no longer find one another. This "leftover" stuff you get, after all the annihilation the Universe can muster, is called freeze-out.
(Image credit: Ned Wright's Cosmology Tutorial.)
Getting this "frozen out" stuff is a consequence of the Universe being out of thermal equilibrium. For example, for example, at some point, you're going to be left with a Universe that contains a bunch of muons and anti-muons. Like most particles we know how to make, these are unstable, and will decay. For most particles/antiparticles, like muons/antimuons, this isn't a big deal. Whatever the particle decays into, the antiparticle will decay into the anti-counterpart, giving you a net gain of nothing.
But some particles are fundamentally different from their antiparticles, and this difference can create more matter than antimatter in the Universe! Here's how.
Let's imagine the Universe is filled with a new kind of unstable particle, the positively-charged Q+, and its antiparticle, the negatively-charged Q-. Because of certain conservation laws, they have to have the same mass, the opposite charge, and the same total lifetime.
But they don't have to be the same in every way. Let's say the Q+ can decay into either a proton and a neutrino, or into an anti-neutron and a positron. That means the Q- must be allowed to decay into an anti-proton and an anti-neutrino, or into a neutron and an electron.
Although this looks weird, because you sometimes have matter decaying into antimatter and antimatter decaying into matter, there are three important things about this type of decay:
- it allows you to violate the conservation of baryon number. (That is, the number of protons + neutrons combined.)
- This is allowed by the standard model, so long as the number of baryons minus leptons is conserved, and
- it can, if things work out correctly, create more matter than antimatter.
If the percentage of the Q+'s that become protons and neutrinos is the same as the percentage of Q-'s that become anti-protons and anti-neutrinos, this won't help you at all. The protons and anti-protons will be equal in number, and you won't create any more matter than antimatter.
Same deal with the anti-neutrons/positrons and the neutrons/electrons. But although it's possible that these individual percentages are equal, it isn't mandatory. The other possibility is -- and this happens in nature -- that particles will prefer one type of decay, while antiparticles will prefer a different type!
If this happens, then the Q+'s would make more protons and neutrinos than the Q-'s would make anti-protons and anti-neutrinos, while the Q-'s would make more neutrons and electrons than the Q+'s would make anti-neutrons and positrons.
Looking solely at the protons/neutrons/anti-protons/anti-neutrons that result from this decay, what would we wind up with?
More matter than anti-matter! In fact, so long as you fulfill these three famous criteria:
- Out-of-equilibrium conditions,
- Baryon-number-violating interactions, and
- C- and CP-violation (the differences in decays, above),
The title says it all: an animated video of Heisenberg singing about the Uncertainty Principle:
So, you know, there's that. It's pretty good, but he's no Feynman:Read the rest of this post... | Read the comments on this post...