I finally got a copy of Cox and Forshaw's The Quantum Universe, and a little time to read it, in hopes that it would shed some light on the great electron state controversy. I haven't finished the book, but I got through the relevant chapter and, well, it doesn't, really. That is, the discussion in the book doesn't go into all that much more detail than the discussion on-line, and still requires a fair bit of work to extract a coherent scientific claim.
The argument basically boils down to the idea that the proper mathematical description of a universe containing more than one fermion is a many-particle wavefunction that is overall antisymmetric under the exchange of any two electrons. That is, if you numbered every electron in the universe, you would write the wavefunction down one way, and if you swapped the numbers on two of the electrons, then re-wrote the wavefunction, you would get the same thing you had the first time, but with an overall negative sign. Thus in seeking to make a quantum model of a hydrogen atom in your living room, you would need to write down some sort of 1090x1090 Slater determinant (or whatever the actual total number of electrons in the universe is) to get the proper state of the many-(many-many-many...)-body system. The total energy of this state will depend on the energy of all of the individual electrons, and some complicated overlap integrals between every single electron state and every single other electron state, so I hope you have a lot of paper or a really fast (quantum?) computer to help you work it out.Read the rest of this post... | Read the comments on this post...
Seems like all the action is in Norway these last few years...
Meteorite crashes through roof in Oslo
from Verdens Gang
Fist size meteorite smashes through roof in Oslo suburb
Nice looking chunk - be worth a pretty penny, as one of the few meteorites with confirmed provenance of hitting a structure.
see also Fireball over Norway - at VG
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By Joe Schwarcz PhD, Author, USASEF Expo Performer, AT&T Sponsored Nifty Fifty Program Speaker
Yellowstone National Park's iconic "Old Faithful" geyser is pretty faithful. It can be counted on to erupt every 50-90 minutes. Iceland's "Great Geysir," from which all other geysers get their name is less reliable. It was mostly dormant for sixty five years before it began semi-regular eruptions again in 2000 thanks to an earthquake. But in New Zealand, you can set your watch by the eruption of the Lady Knox Geyser, named after a former Governor of the country. At exactly 10:15 AM every day a spectacular plume of water and steam bursts into the air to a height of up to twenty meters. How can a natural phenomenon be so predictable? Well, in this case nature gets a little help from chemistry.
At the appointed time, a detergent solution is poured down the channel from which the water erupts. This has the effect of reducing the surface tension of the water that deep within the shaft has been heating up to boiling temperatures due to underground volcanic activity. Surface tension refers to the attractive force between water molecules, and is in fact responsible for water being a liquid at ordinary temperatures. Liquids are characterized by the close proximity of their component molecules, while in gases the distance between molecules is much greater. If the surface tension of a liquid is decreased, the H2O molecules can separate from each other with greater ease, with the result that the liquid turns into a gas. Molecules of "surfactants," a class of substances that encompasses soaps and detergents, wiggle their way in-between water molecules, allowing the boiling liquid to instantly turn into steam. The steam then forces the water that has collected in the channel to burst upwards, and we have an eruption.
The possibility of making a geyser erupt artificially was discovered by accident in New Zealand in 1901 when an "open prison" was established at Waiotapu for criminals who were deemed not to be a danger to society. It so happens that this is one of the most volcanically active areas of the world and the prisoners took advantage of the hot water seeping up from the natural thermal springs to wash their clothes. One day one of them must have used just the right amount of soap and triggered an eruption when the soap solution found its way down the fissures in the rock into the chambers in which underground water had pooled. This is the concept used today to stimulate eruption of the Lady Knox Geyser although detergents have replaced soap because they have been found to be less damaging to the geyser's internal natural plumbing. On occasion Iceland's Great Geysir has also been "soaped" but this is now prohibited for environmental concerns.
Long before the prisoners made their accidental discovery, the science of geyser eruptions had been worked out by none other than Robert Bunsen, of burner fame. Actually Bunsen did not invent the famous burner but did improve upon existing equipment by showing that mixing the combustible gas with just the right amount of air led to a high temperature non-luminous flame. Such a flame was very useful in the development of Bunsen's most famous discovery, the spectroscope. In collaboration with physicist Gustav Kirchoff, Bunsen designed an instrument that would pass the light emitted from a sample heated by his burner through a prism. The "spectrum" of light produced was found to be characteristic of the element found in the sample. Before long Kirchoff and Bunsen had identified cesium and rubidium as new elements and paved the way to the identification of thallium, indium, gallium, scandium by others through spectroscopy.
In 1845, during his tenure as Professor of chemistry at Marsburg University, Bunsen was invited by the Danish government on a geological trip to Iceland following the eruption of Mount Hekla. Bunsen had a lifelong interest in geology and used the occasion to study the gases released from volcanoes and performed analyses on volcanic rocks. He also became interested in Iceland's abundant geysers, especially "The Great Geysir" that propelled water to a height of some fifty meters. Bunsen hypothesized that eruption occurred when a column of underground water was heated around its middle by volcanic activity. In the true spirit of science, Bunsen constructed an artificial geyser in the laboratory consisting of a basin of water from which a long tube filled with water extended upwards. He heated the tube at various points and showed that it was when the water in the middle reached its boiling point that an eruption occurred just like in a natural geyser.
Geysers can do more than excite tourists. In Iceland hot water from geysers is used to heat homes and warm greenhouses, allowing food to be grown in an otherwise inhospitable climate. The accumulation of steam deep within the ground that makes geysers possible can also be tapped by geothermal power plants to produce electricity. Geothermal energy is a great source of electricity but drawing off the steam can lead to the destruction of geyser activity.
Not all geysers gush steam and hot water. In the case of cold-water geysers the eruptions are driven by carbon dioxide gas that forms as limestone, calcium carbonate, decomposes. The gas becomes trapped in underground aquifers until it builds up enough pressure to explode towards the surface through cracks in the strata propelling water into the air. Some of the gas remains in the water in the form of small bubbles so that the geyser actually dispenses soda water.
If you want to experience a mini-cold-water geyser, just drop a couple of Mentos into a bottle of Diet Coke. But do it outside. It makes a mess. If you use a special tube (available from Steve Spangler Science) that can simultaneously drop 7-10 Mentos into the bottle, you'll be treated to a true spectacle as the liquid bursts to the stunning height of about ten meters. That's still some 490 meters short of the super eruptions once produced by the Waimangu Geyser in New Zealand between 1900 and 1904 before the natural plumbing was destroyed by a landslide. The world's tallest geyser now is Yellowstone's Steamboat Geyser that propels water some ninety meters into the air. Unfortunately its eruptions are not predictable. Except on YouTube.Read the comments on this post...
The Links Dump item about software patents this morning includes a lament that there are so many silly little software patents, organized so badly, that finding one you might be infringing would take forever. This may or may not be a convincing argument against them, but for a physics geek like me, my first reaction was "You just need a quantum computer running Grover's algorithm for searching an unsorted database." And I suppose there's a background element for a satirical SF novel in that-- quantum computers ultimately being developed not by banks or the NSA, but by lawyers looking to speed the process of document discovery.
Of course, this in turn reminded me that I have a bunch of quantum-related tabs open in Chrome, and I really ought to do something with those. So, here's a special quantum-themed links dump sort of post:
-- Scott Aaronson, a noted critic of the quantum computing claims by D-Wave, who famously (well, nerd-famously) declared their supposed quantum processor about as useful as a roast beef sandwich, made a visit to their facility, and moderates his stance somewhat.
-- Every few weeks, there's a story about some new promising quantum computing technology. The most recent is the demonstration of topological error correction, which might be essential for making quantum processors that can withstand the noise that inevitably creeps into any real system. This would be good fodder for a ResearchBlogging post, if I had the time to understand it in detail, but I don't. So you get this passing mention.
-- Matt Leifer has written another article about the theorem ruling out some kinds of interpretations that made a bunch of news a little while back. It's for the "Quantum Times," the newsletter of an APS group on quantum information, so it's not exactly at the level your dog might want to read, but if you know a little about it, and want to know more, it's a good piece.
And that's three browser tabs closed. Only 20-odd left...Read the comments on this post...
The patterns of the dark craters on the near side of the Moon have spurred the imagination of observers from all cultures: Some visualize a woman, others a rabbit, or, like most of us, they see the "Man in the Moon."
The explanation as to why we always see the Man in the Moon - that is, why we only see one side - is that tidal forces caused the Moon to slow its spin until it reached the present point. It now takes the same amount of time to rotate around its own axis as it does to revolve around Earth. It is this synchronous rotation that causes the moon to "lock" with Earth, with one hemisphere constantly facing us.
But Prof. Oded Aharonson of the Weizmann Institute's Center for Planetary Science, together with Prof. Peter Goldreich of the California Institute of Technology and Prof. Re'em Sari of the Hebrew University of Jerusalem wanted to know whether there is a reason why this particular half of the Moon locked with Earth or if it is pure luck that it didn't turn its "back" on us?
Read the comments on this post...
Unlike the near side, which is covered in dense craters, the far side is made up of more mountainous regions, and these differences affect the Moon's gravitational energy. Taking this into consideration, the scientists, through careful analysis and simulations, have shown that it is not coincidence but rather, the Moon's geophysical properties that determine its orientation. Their findings have recently been published in Icarus. A more detailed description can also be found on our website: http://wis-wander.weizmann.ac.il/why-do-we-see-the-man-in-the-moon-oded-aharonson
"They call it a great wonder
That the Sun would not
though the sky was cloudless
Shine warm upon the men." -Sighvald, Icelandic poet A couple of times a year, during the New Moon, the Sun, Moon, and Earth all line up in the same plane. As seen from Earth, the Sun's disc appears blocked, either in whole or in part, by the Moon. As The Beta Band would have told you, this creates an
Depending on how close the Moon and Sun are to the Earth, either the Moon's shadow will fall on the Earth, creating a total solar eclipse, or the shadow will end before it ever reaches Earth, in which case we get to see an annular solar eclipse.
(Image credit: Total Solar Eclipse in Russia.)
Back in 1994, I was living in New York; this was the last time an annular eclipse happened anyplace close to where I was living. From where I was, about 87% of the Sun's disk was blocked by the Moon, and there were two very interesting (and obvious) things that happened:
- The Sun remained incredibly, blindingly bright to look at, but gave off virtually no warmth, and
- shadows looked, well, really weird.
I didn't have the fun kitchen skimmer that Philippe Haake had, above, but I discovered that, with my back towards the Sun, if I held my fingers, crossed together, over my head, the shadows produced by the tiny spaces in between my fingers would produce miniature eclipses Suns.
But if I had been in a more fortuitous location, where there actually was a full annular eclipse, those tiny little apertures would have produced images of the ringed annulus, such as the rings Steve G.S. saw shining through the tree leaves in 2005.
(Image credit: Steve G.S., from the 2005 annular eclipse in Spain.)
Well, I live on the West Coast of the United States now, and I'm finally getting another chance to see an annular eclipse! This May 21st/May 20th, depending on which side of the international date line you're on, is our planet's next eclipse. Those of you in Hong Kong, Taipei, Tokyo and other areas will get to see the annular eclipse shortly after sunrise on the 21st, but those of you in the west/southwest United States are in for an extra special treat.
(Image credit: Google Maps / NASA.)
In the waning hours of the day on May 20th, as Sun descends in the west, the Moon will pass in front of it, creating the first annular eclipse in the United States since 1994!
This time, I'm going to be prepared.
First off, I'm going to make sure I have a pinhole camera with me. A pinhole camera is as simple as having a piece of cardboard with a pinhole poked in it and a white screen behind it. As the sunlight passes through the pinhole, the (inverted) image of the Sun's disk gets displayed on the screen in the back.
If the Sun's disk is partially blocked, then what shows up on the display screen is the eclipsed Sun, completely safe for viewing. There are a number of quality, ultra-low-tech options readily available for your display screen.
(Image credit: Shree Nayar of BigShotCamera.org.)
Because the eclipse is happening late in the day -- in the Pacific Time Zone, it starts at about 5:10 PM and ends at around 7:30 PM -- I'll want to make sure I have a clear view to the west, where the Sun will be descending. I am taking no chances, and will be staking out a spot along the coast. With over 200 miles of prime viewing coastline available, I'm even hoping for a little solitude while it happens.
(Image credit: Craig Wolf Photography.)
The ocean is sure to provide me with very little in the way of obstacles that will obscure the Sun's view. The only possible interference will come from the astronomer's nemesis: clouds.
I also plan on photographing the Sun, directly, during the eclipse! Although I'm not a skilled photographer by any stretch, anything from a pair of welder's goggles to the interior of a 3.5" floppy disk, placed over the lens of your camera, will allow you to successfully photograph the Sun during an eclipse!
(Image credit: Chin-Yu Hsu, who was in high school with me during the 1994 eclipse, of the 2009 solar eclipse, from Taiwan, using a 3.5" floppy filter.)
I won't, however, be looking at the Sun through the 3.5" floppy disk; welder's goggles are okay (as are some other types of protective eyewear), but be careful! You won't feel the damage the Sun can do to your eyes until it's too late; make sure if you're going to look at the Sun directly that you get the proper equipment to protect your eyes.
I'm hoping to get some images as good as the ones taken by Steve G.S. with his solar filter in 2005. (Yeah, right!)
(Image credit: Steve G.S.)
The United States will get a shot at a total solar eclipse -- perhaps the only sight more spectacular than an annular eclipse -- on August 21, 2017. But for those of you with a chance to go out and view this one, including those of you just crazy enough to be eclipse chasers (which may include me, now), start planning for it now.
You won't get another chance at an annular eclipse in the USA until 2023, so don't miss it!Read the comments on this post...
"Is no one inspired by our present picture of the Universe? This value of science remains unsung by singers, you are reduced to hearing not a song or poem, but an evening lecture about it. This is not yet a scientific age." -Richard Feynman Back in 2008, Time Magazine interviewed Neil de Grasse Tyson, and asked him, " What is the most astounding fact you can share with us about the Universe?" His answer was indeed a very good, true, and astounding fact about the Universe: that all the complex atoms that make up everything we know owe their origins to ancient, exploded stars, dating back billions of years.
(Image credit: NASA, ESA, HEIC, Hubble Heritage Team (STScI/AURA).)
It's a great fact, and it's definitely on the short list of the most remarkable things we've learned about the Universe. But if I were to choose the most astounding fact about the Universe, I'd want you to consider something else.
It didn't have to be this way.
Not just the trees, the mountains, the skies and the oceans. Not merely everything on this Earth, mind you. Not even everything in the entire Universe.
(Image credit: R. Jay Gabany.)
The way it all turned out, no doubt, is absolutely wondrous. Just here, in our own little corner of the Universe, we find ourselves in a forgotten, non-descript little group of galaxies no more or less special than any of the billions out there.
(Image credit: Wikimedia user Azcolvin429.)
But when we look out at the Universe, whether we look at the internal structure of matter, probing things down to the tiniest subatomic scales...
(Image credit: CERN / Lucas Taylor, via simulation.)
...or out into the expansive abyss of deep space, billions of light years away, at the largest scales visible to an observer within our Universe, there is one fact that stands out as the most astounding.
(Image credit: NASA, ESA, the ACS Science Team and N. Benitez et al.)
The entire Universe,
on all scales,
in all places,
and at all times,
obeys the same fundamental laws of nature.
(Image credit: M. Csele/Niagara College, retrieved from here.)
From the weakest photon of light to the largest galaxy ever assembled, from the unstable atoms of Uranium decaying in the Earth's core to the neutral hydrogen atoms forming for the first time 46 billion light years away, the laws that everything in this Universe obey are the same.
(Image credit: Nancy Ellen Abrams and Joel R. Primack.)
This is the most remarkable thing of all.
Imagine an existence where nature behaves randomly and unpredictably, where gravity turns on-and-off on a whimsy, where the Sun could simply stop burning its fuel for no apparent reason, where the atoms that form you could spontaneously cease to hold together.
(Image credit: Karim Fakoury.)
A Universe like this would truly be frightening, because it could never be understood. The things you learn here and now might not be true later, or even five feet away.
But the Universe isn't like this at all.
(Image credit: U.S. DOE, NSF, CPEP and LBNL, retrieved from here.)
The Universe is a place where the matter and energy in it can change, the spacetime itself that we all occupy can change, but the fundamental laws -- that everything is subject to -- are constant.
Because what that means is that we can observe the Universe, experiment with the Universe, assemble and disassemble the things we find in it, and learn.
(Image credit: NASA, ESA and the Hubble Heritage Team (STScI / AURA).)
Only if the fundamental laws of the Universe are the same everywhere and at all times can we learn what they are today, and use that knowledge to figure out what the Universe -- and everything in it -- was doing in the past, and what it will be doing in the future.
In other words, it is this one fact, this most astounding fact, that allows us to do science, and to learn something meaningful, at all.
(Image credit: xkcd.)
In short, the most astounding fact about the Universe is that it can be understood at all.
But Neil's answer was pretty good, too.
Read the comments on this post...
Yes, folks, it's YouTube Weekend! (Our daycare is closed and it's convention/caucus season in Minnesota and I've got a candidate!)Read the comments on this post...
Yesterday was a really grueling day, and I'm home with The Pip today, so no substantive blogging. But here's a song about the universe, written and performed by one of my colleagues:
If this becomes the next LHC Rap, remember you heard it here first.
By a weird coincidence, we've been watching our Animaniacs DVD's with SteelyKid, and just a couple of days ago got to this one:Read the rest of this post... | Read the comments on this post...
"Be careful. People like to be told what they already know. Remember that. They get uncomfortable when you tell them new things. New things...well, new things aren't what they expect. They like to know that, say, a dog will bite a man. That is what dogs do. They don't want to know that man bites a dog, because the world is not supposed to happen like that. In short, what people think they want is news, but what they really crave is olds...Not news but olds, telling people that what they think they already know is true." -Terry Pratchett We all like to think that our opinions are the result of years of hard-earned accumulation of knowledge. That we've gone and aggregated all of the relevant facts on a particular issue, put them together in the most sensible way, and that's how we've arrived at our picture of the world.
But, of course, that isn't the way we work at all.
(Image credit: Scott Adams, 2011.)
Known as confirmation bias, it's the very human tendency to, once we've formed an opinion, place our faith in the new evidence that appears to support that position, but to look for holes in the evidence that undermines or disagrees with that opinion.
In other words, changing our minds -- especially once we've made our minds up -- is extraordinarily difficult. The way we often deal with this, in the case of a divisive issue, is to think that the other side on an issue is (any combination of) misinformed, ignorant, foolish, or conspiring against the truth. And we often miss no opportunity to present them (and their position) as inferior to our own.
When was the last time you saw someone who held a passionate position on one side or another of a divisive issue actually change their mind and switch to the other side in the face of overwhelming evidence? It doesn't happen very frequently, does it?
You may not see it very frequently in your own life, in politics, or most places that you look, but it happens all the time in science. Not for everyone, of course, but science is one of the only places where you'll see a vast majority of scientific experts in their field change their mind on an issue based on the evidence that comes in.
(Image credit: retrieved from the CCCB LabZine.)
When a uniform-temperature, all-sky microwave radiation background was discovered in the 1960s by Penzias and Wilson (above), it provided overwhelming scientific evidence supporting the Big Bang picture of the Universe, and disfavoring alternative explanations such as the Steady State theory. A few notable exceptions held out, but modern cosmology simply does not make sense without the Big Bang, and this was the observation that sealed it.
(Image credit: University of Bristol, Sharon Mooney et al.)
Same deal with evolution. Without it, modern biology -- including genetics, DNA, and modern medicine -- makes no sense. Evolution was an amazing idea that came in multiple variants for a time, but when the archaeological evidence of transitional fossils started pouring in, it became clear that all living things on the planet were descended from previous generations of living things dating back at least hundreds of millions of years. (We know that's longer, now.) Even transitional forms for organisms like whales and dolphins exist, and when this type of evidence started rolling in, even the most skeptical of competent scientists started changing their minds.
(Image credit: Associated Press, retrieved from here.)
And in a very notable recent example, climate science skeptics such as Richard Muller, above, are overwhelmingly concluding that there is a link between the observed rising temperatures of the Earth and the effects of human activity, once again in the face of overwhelming scientific evidence. As always, there are holdouts, but that does not change the scientific facts or conclusions.
My favorite example, though, of a scientist who held strong convictions on an issue, but changed their mind, dates back more than 400 years!
(Image credit: Johannes Kepler, 1610, Public Domain image.)
Towards the end of the 16th Century, after the death of Tycho Brahe, Johannes Kepler, pictured above, was -- perhaps along with Galileo -- the foremost astronomer in all of Europe. Much like Galileo, Kepler was intimately familiar with the work of Copernicus, and recognized how beautiful the possibility of a heliocentric Universe was.
After all, it could explain the retrograde motion of the planets -- how some planets appeared to reverse direction with respect to the fixed stars -- in their motion from night-to-night!
(Image credit: Tunc Tezel, of Mars in retrograde.)
Instead of a stationary Earth, where the planets orbit the Earth in a superposition of circular orbits, occasionally reversing course and appearing to move backwards, the heliocentric model had the outer planets (Mars, Jupiter, Saturn, etc.) move backwards because the Earth, in its faster orbit around the Sun, overtook the outer planets in their position! (Mars, for those of you astutely watching it, is finishing up its retrograde motion as I write this!)
This is nearly a hundred years before Newton's gravity, so there was the great question of how these orbits came to be. And Kepler's idea was nothing short of genius. Sheer, unbridled, and beautiful genius.
(Image credit: Mysterium Cosmographicum, J. Kepler's notebook, retrieved here.)
Envisioning the six planets as being supported by the five Platonic solids with spheres inscribed/circumscribed upon them, the orbits would be defined by the circumferences of these spheres. It was a beautiful idea, with very explicit predictions for the ratios of the scales of the planetary orbits. Because there are only five Platonic solids and were only (at the time) six planets, this scheme was beautiful, compelling, and created an incredible buzz amongst scholars.
But unlike Galileo, Kepler had access to the finest data in the world: the observations of his predecessor, Tycho Brahe. And the data simply did not agree with Kepler's theory. The orbits were all wrong.
Not by that much, mind you, but by enough that it clearly didn't fit. At the time, there was tremendous prejudice in favor of the circle being the only acceptable shape for an orbit, but -- ever the scientist -- Kepler followed the data to its logical conclusion. He even rejected his beautiful Mysterium Cosmographicum, creating, instead, the model we use today.
(Image credit: Phillip Brown and James Braselton.)
They're not circles, or a superposition of a number of circles at all; the orbits are ellipses! Planets move around the Sun with the Sun at one focus of an ellipse; the first of Kepler's three laws of planetary motion!
And so Kepler was able to throw away the most beautiful idea he ever had, and in place of it, discover the way the Universe actually worked. And that's my favorite example of defeating your own confirmation bias; from more than 400 years ago! That's the reward of being honest with yourself, one of the most difficult things, apparently, for us, as humans, to do.
So let me ask you; what's your favorite example, from your own life, of when you changed your mind on an issue, based on the new evidence that you learned and couldn't ignore?Read the comments on this post...
So, the news of the moment in high-energy physics is the latest results being reported from a conference in Europe. The major experimental collaborations are presenting their newest analyses, sifting through terabyte-size haystacks of data looking for the metaphorical needle that is the Higgs boson.
And what are those results? It sort of depends on who you ask. Tommaso Dorigo points at the final data from the Tevatron and claims victory; Matt Strassler thinks the lack of evidence at the LHC is almost as important, though there is progress there in excluding some new regions. The net result is a step of size dx in the general direction of progress, but still a long way from anything conclusive. I think.
My primary reaction to this is relief. I'm partly relieved that I'm not an experimental particle physicist, but mostly relieved that they didn't discover the Higgs in a way that would make me look foolish for not talking more about it in How to Teach Relativity to Your Dog. The current results make me feel better about being vague and equivocal about the Higgs in the book. And since this is my blog, the really important thing is how I feel about the whole thing...
Also, here's me and Emmy talking about the canine version of particle physics, just because:
No sign of the Bacon Boson, either, but Emmy's still hopeful.Read the comments on this post...
by Fred Bortz, author of Meltdown! The Nuclear Disaster in Japan and Our Energy Future (Twenty-First Century Books, 2012)
A year ago this week, on March 11, 2011, the biggest earthquake in Japan's history devastated the Tohoku region, 320 kilometers northeast of Tokyo. In the huge tsunami that followed, more than 13,000 people drowned, and thousands of buildings and homes were reduced to rubble.
Within hours, horrifying photos and videos spread around the world. But the most frightening news was yet to come. The Fukushima Dai'ichi nuclear power plant was seriously damaged and three of its reactors were heading for meltdowns.
Over the next few days, explosions and fires released radioactivity into the air, and the Japanese government declared a 20-kilometer evacuation zone. It was the world's worst nuclear disaster since the Chernobyl explosion in 1986.
I knew something about meltdowns. I had previously written about Chernobyl and the accident at Three Mile Island in a chapter of my 1995 book Catastrophe! Great Engineering Failure--and Success. I knew the arguments for and against nuclear power.
After Fukushima, those arguments resounded with added urgency. If engineers know how to build safe reactors, why did the Fukushima reactors fail? But if we stop building nuclear reactors, how can we replace enough fossil fuel plants to limit global warming?
I knew I had to share those questions for middle grade readers. The result was Meltdown! The Nuclear Disaster in Japan and Our Energy Future, just published by Twenty-First Century Books. I'm delighted to have the opportunity to discuss that book as a Featured Author at the 2012 USASEF Book Fair.
The new book is out, which means it's time for lots of promotional efforts and links to radio shows and news articles and that sort of thing. Such as this one: I'll be talking about relativity and dog physics tomorrow night, Wednesday the 7th, on the Big Science radio program(me) at 9pm London time (in the frame of reference in which London is at rest, anyway). This'll be the first radio show for the new book, though I've done a few phone interviews for print publications (links as they become available...).
If you're in London, and have nothing better to do, tune in. (We are, after all, more popular than call girls in London...) Or listen via the Internet. Or don't. It's all good.Read the comments on this post...
My course on the history and science of timekeeping has reached the home stretch, with students giving presentations in class for the remainder of the term. My portion of the course was wrapped up with two lectures on "quantum timkeeping," as it were: a lecture on the development of quantum mechanics:
And one on the development of atomic clocks:
These are pretty fast-moving, but by this point in the course, students were already working on their final projects, so these are mostly cultural sorts of presentations. The idea is to give them a bit of the flavor of quantum physics and how it plays into timekeeping, not for them to be able to solve problems relating to any of these topics.Read the rest of this post... | Read the comments on this post...
"I soon became convinced... that all the theorizing would be empty brain exercise and therefore a waste of time unless one first ascertained what the population of the Universe really consists of." -Fritz Zwicky You very likely know that there are four fundamental forces in the Universe: gravity, electromagnetism, and the weak and strong nuclear forces. While only some particles experience the nuclear and electromagnetic forces, anything with mass or energy -- which is everything we know of -- is subject to gravity.
(Image credit: CountInfinity by Ananth.)
The strong nuclear force binds all the nuclei heavier than hydrogen together, the weak force is responsible for radioactive decays and the (incredibly rare) neutrino interactions, but the two you're most familiar with are gravity and electromagnetism. Operating practically everywhere in the Universe, the two of them are the reason you can sit where you are right now as you read this.
(Image credit: SPH4C Physics.)
The reason that you are safely anchored down to the ground is the force of gravity, accelerating everything at Earth's surface downwards at 9.8 m/s2. But you are (most likely) not accelerating downwards, and that's because your body is composed of these electromagnetically-interacting particles -- atoms -- that the floor/ground/chair pushes back up on you at with an equal and opposite force to gravity.
The net result is that the electromagnetic force and the gravitational force cancel out, and so you remain where you are. When you toss a ball, it makes a parabola, as it gets accelerated down due to gravity. But once the ball hits the ground, it interacts electromagnetically, preventing it from falling through the floor. But imagine, hypothetically, that you instead tossed a neutrino, an object which doesn't interact electromagnetically? What happens then?
(Image credit: Donald E. Simanek.)
Because the neutrino doesn't interact electromagnetically or via the strong force, but does interact gravitationally, it would follow the same parabolic path that the ball did, until it ran into the surface of the Earth. At that moment, while the atoms in the Earth would collide with the atoms in the ball (and that's an electromagnetic interaction), because neutrinos don't interact electromagnetically, the neutrino would simply pass through the Earth's atoms, as though they weren't even there. It would plummet in an orbit -- a nearly perfect ellipse (nearly, because the Earth isn't a point mass concentrated at its very core) -- and would eventually return to its starting point. This is the same way a comet has an elongated, elliptical orbit with the Sun at one focus of the ellipse: due to the force of gravity alone.
The lack of strong and electromagnetic interactions, a vital characteristic of neutrinos, is also a characteristic of dark matter! What would happen if we took two giant blobs of matter -- a mix of dark and normal matter -- and let them go in space? What would happen?
(Image credit: NASA / CXC / M. Weiss.)
Shown above is the results from such a simulation. In pink is the normal matter, made up of atoms, while in blue is dark matter. Initially, both the dark and normal matter move together, accelerating towards the other blob. When they first collide, the atoms smash into one another, slowing down and heating up! But collisions are electromagnetic interactions, so dark matter doesn't do it. Instead, the dark matter passes right through everything: through the normal matter in its own blob, through the other blob's dark matter, through the other blob's normal matter. So what we should see, shortly after a collision like this between, say two galaxy clusters in space, should be a separation in space between the dark matter (observable through the effect of weak gravitational lensing) and the normal matter (observable through the hot X-ray emissions that should come from the colliding gas).
(Image credit: X-ray, Optical, Lensing composite, courtesy NASA / CXC / CfA / M.Markevitch et al. / STScI / Magellan / U. Arizona / ESO WFI / D.Clowe et al.)
These colliding clusters -- known as the Bullet Cluster -- strongly support a picture where galaxy clusters are made up predominantly of a large, diffuse halo of dark matter with a much smaller amount of normal matter in the form of collapsed, star-containing structures and gas.
We can then go back to the beginning of the Universe and simulate how galaxies should form in a Universe filled with dark matter, dark energy, and normal matter in the proportions we think are present.
(Image credit: V. Springel et al., for the Millenium Simulation, retrieved here.)
And we can compare it to the galaxies that are actually there in the observed Universe, and see how well the simulations agree with the data!
(Image credit: 2dF Galaxy Redshift Survey.)
The answer is extremely well, of course, but we don't merely rely on a visual inspection. Rather, we do our analysis quantitatively, and see what the best fit cosmological model is to this data. What do we find?
(Image credit: Cole et al. (2005), for the 2dFGRS.)
A Universe, dominated by dark energy, where 17% of the matter is normal matter and 83% is dark matter. The "wiggles" you see in the power spectrum, above, come from normal (baryonic / atomic) matter, which would go all the way down to the bottom of the graph were there no dark matter. This is one of the strongest arguments against a Universe without dark matter, and has been made even stronger in recent years by better observations by the Sloan Digital Sky Survey.
But the Bullet Cluster is not the only cosmic smash-up between galaxy clusters in the Universe, although it might be the simplest, earliest-stage one we've observed. Things are much less easy to decipher in, say, cluster Abell 520.
(Image credit: Optical/Lensing via NASA / CXC / CFHT / UVic. / A. Mahdavi et al.)
With the X-ray and lensing data clearly more complicated than in the Bullet Cluster, it is difficult to piece together exactly what's going on here. Perhaps this is an intermediate stage in a cluster merger? Perhaps something unusually violent is happening here? Or, spectacularly, perhaps dark matter is not behaving the way all other indicators are pointing?
The above image was released in 2007, and what you want to make sure to do is check that your observational data is solid. So they went back, got to use the Hubble Space Telescope to improve their observations, and got even better data, which was just released a few days ago. What -- in a new set of false-colors -- did they find?
(Image credit: NASA, ESA, CFHT, CXO, M.J. Jee and A. Mahdavi.)
What are we looking at here? From the NASA site itself: Starlight from galaxies, derived from observations by the Canada-France-Hawaii Telescope, is colored orange. The green-tinted regions show hot gas, as detected by NASA's Chandra X-ray Observatory. The gas is evidence that a collision took place. The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. So in this case, the optical presence of the galaxies (orange), so well-aligned with the dark matter in the Bullet cluster, are independent of both the gas, in green, and the dark / overall matter, dominated by the blue color. Perhaps this is easier to see if we look at each of these components separately.
(Image credit: Same as above, retrieved from CFHT.)
There's some overlap of the dark matter with the luminous galaxies, which ought to move together with the dark matter, but there's also substantial overlap of the dark matter with the hot gas, which is an unexpected surprise!
Does this mean that dark matter's doing something weird? My first instinct -- mostly because the evidence for the standard theory dark matter is so overwhelming from so many different sources -- is to wonder whether this isn't either a later-stage collision, and/or if there isn't enough cool gas mixed in with the central hot gas to obscure a group of galaxies at the center that are actually there, but behind the gas? (This cosmic catastrophe, after all, is about 2.4 billion light-years away, and in three dimensions.) The jury is still out: "This result is a puzzle," said astronomer James Jee of the University of California, Davis, leader of the Hubble study. "Dark matter is not behaving as predicted, and it's not obviously clear what is going on. Theories of galaxy formation and dark matter must explain what we are seeing." If I make a composite of the three separate image components -- luminosity, mass, and X-ray emissions -- without those distracting background galaxies, what do we find?
Something very puzzling is going on here. If this is as young a collision as the Bullet Cluster, it's conceivable that dark matter is doing something very weird. We have very few examples of high-speed galaxy cluster collisions in the Universe, with Abell 520 and the Bullet Cluster being the two best measured ones, and yet they appear -- at first glance -- to be inconsistent with one another!
I'll definitely be following this story to see if there's a resolution, but if it turns out that this is as young a collision as the Bullet Cluster, there are no hiding galaxies, and the current picture of dark matter cannot explain what these galaxy clusters are doing, we may be learning an awful lot more than we bargained for awfully soon. Some are betting that's what will happen; I am by far more cautious, and would still happily bet on the standard picture of dark matter, with perhaps some complex kinematics -- maybe involving multiple mergers -- for the collision. For the time being, I'm content to agree with Ray Sanders, and say that the dark matter core of Abell 520 is mysterious. What's the solution to the mystery? I've made my wager; what's yours?Read the comments on this post...
Science and Engineering Education: What Happens in the Home Is Just as Important as the Classroom [USA Science and Engineering Festival: The Blog]
By Larry Bock
Founder and organizer, USA Science & Engineering Festival
Encouraging and motivating kids early in science and engineering via exciting, hands-on interactions in discovery may be one of the most important steps to boosting their interest and performance in these fields.
But if you think this job falls to teachers alone, you're wrong. Parents can, and should, play an active and frequent role outside the classroom, especially in creative ways that keep children's innate sense of curiosity and exploration alive.
"Kids love the chance to try experiments, visit zoos, or watch science fiction movies," says Pendred Noyce, a physician, education advocate, and children's author. "Parents can keep excitement alive with activities that help kids develop a sense of science mastery, autonomy, and purpose."
Noyce knows well of what she speaks. Besides her aforementioned credentials, she is also a parent, and was herself inspired by her father, Robert Noyce, co-inventor of the integrated circuit (computer chip) and one of the founders of Intel. Today, as president of Tumblehome Learning, Inc., she creates science-related adventure books, biographies and hands-on learning kits for children.
We are proud to have Noyce as a featured author this April at the USA Science & Engineering Festival and Book Fair hosted by Lockheed Martin (the nation's largest celebration of science and engineering). Below, she shares five ways that parents can keep kids interested and motivated in science and engineering discovery:
1. Read great science books together -- fiction and non-fiction. Better yet, start a parent-child science book and activities club. Read about a topic and explore it further through experiments. This is the idea behind Tumblehome Learning -- great science stories coupled with hands-on exploration.
2. Visit as many museums, aquaria, and zoos as possible. Public libraries often provide patrons with free admissions tickets. Look for museum classes and opportunities for kids to become peer "explainers."
3. Create projects together, from birdhouses to burglar alarms. Making real things builds physical intuition, 3D perception, and confidence. A five-year-old girl who knows a flat-head from a Phillips-head screwdriver will dare to imagine a career in engineering.
4. Research summer programs or college outreach days. Better yet, let the kids do the research. The more their autonomy, the deeper their commitment.
5. Become a family of citizen scientists. Explore "Citizen Science" on the Web and join a project on anything from bird migration to protein folding to tracking invasive species. Your kids can experience the authentic excitement of contributing to the march of scientific knowledge.
The USA Science & Engineering Festival, with its exciting hands-on approach to inspiring kids in technology and innovation, will be encapsulating key elements of Noyce's timely advice this spring.
A truly world-class event, the Festival -- known widely for its unforgettable array of technology, innovators, science celebrities, Nobel Laureates, its nationwide satellite events, as well as amazing interactive exhibits and stage shows -- has rapidly evolved into a must-attend gathering for families and others.
The month-long Festival culminates the weekend of April 28-29 with a massive Expo celebration in Washington, DC, replete with over 2,500 interactive exhibits and more than 150 live performances by science celebrities, space explorers, best-selling authors, innovative entrepreneurs and world-renowned experts.
A virtual playground of learning and discovery for kids, the Expo adroitly integrates science and engineering in so many interesting ways that they are sure to inspire parents with "citizen scientists" ideas to explore with their kids at home. What's more, the event is free!
Here are just a few examples of the excitement that awaits families at the Festival Expo:
Meet Science Celebrities: Well-known personalities such as these will be on hand to help science come alive: Bill Nye the Science Guy; real-life neuroscientist Mayim Bialik who stars in the hit TV comedy The Big Bang Theory; Jamie Hyneman and Adam Savage of the MythBusters; Jeff Lieberman, host of Discovery Channel's Time Warp, and science-of-illusion maestro Apollo Robbins.
Award-Winning Authors: In addition to Pendred Noyce, meet and hear prominent and inspiring science authors such as: Homer Hickam, autobiographer of Rocket Boys (the book that formed the basis of the Hollywood movie October Sky); nationally-acclaimed children's science book writers Seymour Simon and Joy Hakim, and science fiction writer Robin Cook.
Tinkerers and Inventors: From demonstrations by MakerBot Industries, Fab Lab DC and others at the Expo (and at the partnering Robot Fest and DIY Pavilion), you'll see and experience the amazing technology that is spurring the DIY, or Do It Yourself, movement. This movement is making inventing easier and more cost effective for the average person, and inspiring future engineers!
Space Heroes and Heroines: Be inspired by such role models as: John Mace Grunsfeld, Ph.D., a five-time Space Shuttle astronaut; electrical engineer Anousheh Ansari, who in 2006 became the first female private space explorer, and legendary computer video game innovator Richard Garriott who became the sixth private citizen to journey into Earth's orbit.
Cutting-Edge Scientists and Engineers: Learn from leading scientists and engineers at the Expo's Career Pavilion about the joys and challenges of their work and the preparation needed. The Pavilion will also give students the chance to investigate these careers on their own as well as colleges, scholarships, internships, mentorships and after-school programs available.
Innovative Entrepreneurs: These are just some of the exciting entrepreneurs you'll meet who are changing the course of technology: Elon Musk, creator of rocket manufacturer SpaceX and co-founder of Pay Pal (the world's largest internet payment system), and George Whitesides, CEO and president of Virgin Galactic, the pioneering U.S.-based space tourism company.
Myriad Stage Performances and Exhibits: And from exciting presentations in music, magic and illusion, comedy, Hollywood movies, comic book superheroes, robotics and other frontiers, you'll discover that science is truly all around us.
It's true: Inspiring the next generation of innovators, as well as future "science citizens," depends as much on what happens outside the classroom with parents as it does inside our schools with teachers.Read the comments on this post...