The natural nuclear reactor formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a nuclear chain reaction took place. The heat generated from the nuclear fission caused the groundwater to boil away, which slowed or stopped the reaction. After cooling of the mineral deposit, short-lived fission product poisons decayed, the water returned and the reaction started again. These fission reactions were sustained for hundreds of thousands of years, until a chain reaction could no longer be supported. Fission of uranium normally produces five known isotopes of the fission-product gas xenon; all five have been found trapped in the remnants of the natural reactor, in varying concentrations. The concentrations of xenon isotopes, found trapped in mineral formations 2 billion years later, make it possible to calculate the specific time intervals of reactor operation: approximately 2 hours and 30 minutes
Nice try Fermi, but Mother Nature got there first.
Due to a mistranslation, Soviet reports on Enrico Fermi claimed that his work was performed in a converted “pumpkin field” instead of a “squash court”, squash being an offshoot of hard racquets.
When the first self-sustained nuclear chain reaction was achieved, a coded phone call was made by one of the physicists, Arthur Compton, to James Conant, chairman of the National Defense Research Committee. The conversation was in impromptu code:
Compton: The Italian navigator has landed in the New World. Conant: How were the natives? Compton: Very friendly.
Pumpkin field, tube alloy, the Italian navigator, the Manhattan Project…the building of the atomic bomb had no shortage of fanciful language.
Update: BLDGBLOG did a post on fossil reactors recently, which is probably where I got the link above in the first place.
Are the problems that have plagued the Large Hadron Collider and previous high-energy efforts (SSC, I’m looking at you here) a result of the Higgs boson travelling back from the future to meddle in its own discovery? A pair of scientists think it’s a possibility.
“It must be our prediction that all Higgs producing machines shall have bad luck,” Dr. Nielsen said in an e-mail message. In an unpublished essay, Dr. Nielson said of the theory, “Well, one could even almost say that we have a model for God.” It is their guess, he went on, “that He rather hates Higgs particles, and attempts to avoid them.”
This malign influence from the future, they argue, could explain why the United States Superconducting Supercollider, also designed to find the Higgs, was canceled in 1993 after billions of dollars had already been spent, an event so unlikely that Dr. Nielsen calls it an “anti-miracle.”
Nothing like a little science on the Moon, I always say.
Astronaut David Scott in 1971, from the Apollo 15 Lunar Surface Journal. Scott was part of the Apollo 15 crew, and applied Galileo’s findings about gravity and mass by testing a falcon feather and a hammer. The film, shown in countless high school physics classes, is the nerdy, oft-neglected cousin of Neil Armstrong’s space paces.
I don’t put people on pedestals very much, especially not physicists. Feynman [who won a 1965 Nobel for his work in particle physics] was pretty good, although not as good as he thought he was. He was too self-absorbed and spent a huge amount of energy generating anecdotes about himself. Fermi [who developed the first nuclear reactor] was good, but again with limitations-every now and then he was wrong. I didn’t know anybody without some limitations in my field of theoretical physics.
I read one such anecdote involving Gell-Mann in a book some years ago:
Richard Feynman, Gell-Mann’s chief competitor for the title of the World’s Smartest Man but a stranger to pretension, once encountered Gell-Mann in the hall outside their offices at Caltech and asked him where he had been on a recent trip; “Moon-TRAY-ALGH!” Gell-Mann responded in a French accent so thick that he sounded as if he were strangling. Feynman — who, like Gell-Mann, was born in New York City — had no idea what he was talking about. “Don’t you think,” he asked Gell-Mann, when at length he had ascertained that Gell-Mann was saying “Montreal,” “that the purpose of language is communication?”
Assuming you’re not in a big lecture hall and the professor shuts the door at the start of class, how long does it take for you and your classmates to deplete the oxygen enough to feel it?
Here’s a taste of the reasoning behind the answer:
So one person needs about 2lb of oxygen a day, or .9 kg. But how many liters is that? Oxygen has a molar mass of 16 grams, so oxygen gas, or O2, has a mass of 32 grams per mole. One mole of gas at standard pressure and temperature takes up 22.4 liters.
I don’t know if they brought this up on physicsbuzz yet, but lack of oxygen isn’t really uncomfortable (though it can kill you). Increase in CO2 is what triggers the apparent need to breath. I am pretty sure the minimum partial pressure of O2 is around 0.16 bar. Actually, that is the min recommended, I don’t know if that is the pass-out limit.
On July 17, 1969, The New York Times issued a correction related to an editorial the paper published in 1920 that dismissed the idea of rocket travel in the vacuum of space. The editorial read, in part:
That Professor Goddard, with his ‘chair’ in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react — to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high school.
The correction stated:
Further investigation and experimentation have confirmed the findings of Issac Newton in the 17th Century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error.
The Times regrets the error! Wish I’d written that next to a few muffed physics exam questions. Here’s a pretty good explanation of why rockets work in vacuums. (via @davidfg)
Law of Gravitation - An Example of Physical Law
The Relation of Mathematics and Physics
The Great Conservation Principles
Symmetry in Physical Law
The Distinction of Past and Future
Probability and Uncertainty - The Quantum Mechanical View of Nature
Seeking New Laws
If I ever write a book, it might have something to do with the two minds that govern creative expertise: the instinctual unconscious mind (the realm of relaxed concentration) and the thinking mind (the realm of deliberate practice). The tension between these two minds is both the key to and fatal flaw of human creativity. From the world of sports1, here’s Rockies pitcher and college physics major Jeff Francis describing the interplay of the minds on the mound:
Even though I do understand the forces and everything, there’s a separation when I’m pitching. If I throw a good pitch, I know what I did to do it, but there has to be a separation between knowing what I did and knowing why what I did helped the ball do what it did, if that makes any sense at all. If I thought about it on the mound, I’d be really mechanical and trying to be too perfect instead of doing what comes naturally.
But you don’t need to be a physics major to wrestle with the consequences of the conflict between the two minds. After an injury and subsequent surgery, Francis’ instinctual mind works to protect his body from further injury:
Francis repeatedly pulled the ball back in preparation to throw. But as he flashed his arm forward, his hand would, mind unaware, bring the ball back toward his ear rather than at full extension. It was his body essentially shortening the axis of his arm to decrease the force on his shoulder, protecting him from pain. And Francis could not stop it.
After his 10th pitch and first muffled groan of pain, he stopped.
“It’s hurting you?” Murayama said.
“Yeah,” Francis said.
“I can tell. You’re getting out ahead of your arm. Slow down, stay back a little more.”
“Does it look like I’m scared to throw a little?”
“Are you scared?”
“Not consciously.”
To fully recover and regain his former effective pitching motion, Francis will utilize his thinking mind to retrain his unconscious mind through deliberate practice to ignore the injury potential. (thx, adriana)
[1] Most of the examples I’ve cited over the years deal with sports, mostly because professional athletes are among the most trained, scrutinized, studied, and optimized creative workers in the world. For a lot of other professions and endeavors, the data and scrutiny just isn’t as evident. ↩
When they are passing in front of their stars, their atmospheres are backlit in a way that can make spectroscopic analysis of the different chemicals in their atmospheres comparatively easy: the wavelengths of light absorbed by the various chemicals will show up, in a tiny way, in the spectrum of the starlight. And this is what makes it possible to imagine looking at them for signs of life.
What scientists would look for are planets with unstable atmospheres, which James Lovelock said was an indication of life.
After the extragalactic planet post this morning, Sam Arbesman sent me a link to systemic, a blog dedicated to the search for extrasolar planets written by Greg Laughlin, one of the scientists involved in the effort. Here are two relevant posts. In Forward, Laughlin says we’re very close to finding a nearby Earth-like planet:
Detailed Monte-Carlo simulations indicate that there’s a 98% probability that TESS will locate a potentially habitable transiting terrestrial planet orbiting a red dwarf lying closer than 50 parsecs. When this planet is found, JWST (which will launch near the end of TESS’s two year mission) can take its spectrum and obtain resolved measurements of molecular absorption in the atmosphere.
In Too cheap to meter, Laughlin presents a formula for the land value of such a discovery that depends on how far away the planet is, the age of the star it orbits, and the star’s visual magnitude.
Applying the formula to an exact Earth-analog orbiting Alpha Cen B, the value is boosted to 6.4 billion dollars, which seems to be the right order of magnitude. And applying the formula to Earth (using the Sun’s apparent visual magnitude) one arrives at a figure close to 5 quadrillion dollars, which is roughly the economic value of Earth (~100x the Earth’s current yearly GDP)…
The idea is to use gravitational microlensing, in which a distant source star is briefly magnified by the gravity of an object passing in front of it. This technique has already found several planets in our galaxy, out to distances of thousands of light years. Extending the method from thousands to millions of light years won’t be easy, says Philippe Jetzer of the University of Zurich in Switzerland, but it should be possible.
The levitation trick works because giant magnetic fields slightly distort the orbits of electrons in the frog’s atoms. The resulting electric current generates a magnetic field in the opposite direction to that of the magnet. A field of 16 teslas created an attractive force strong enough to make the frog float until it made its escape.
After two to three weeks, the team found a small number of “triple tracks” in the plastic — three 8-micrometre-wide pits radiating from a point (see diagram, top right). The team says such a pattern occurs when a high-energy neutron strikes a carbon atom inside the plastic and shatters it into three charged alpha particles that rip through the plastic leaving tracks.
It’ll be interesting to see if this can be replicated and the source of the neutrons verified.
The reality in question — admittedly rather a small part of the universe — was the polarisation of pairs of photons, the particles of which light is made. The state of one of these photons was inextricably linked with that of the other through a process known as quantum entanglement. The polarised photons were able to take the place of the particle and the antiparticle in Dr Hardy’s thought experiment because they obey the same quantum-mechanical rules. Dr Yokota (and also Drs Lundeen and Steinberg) managed to observe them without looking, as it were, by not gathering enough information from any one interaction to draw a conclusion, and then pooling these partial results so that the total became meaningful.
That’s a relief, although the head of one of the group called their results “preposterous”, so perhaps we’re still not really here.
You may remember reading the New Yorker article on Garrett Lisi, a surfer, physicist, and snowboarder who came out of nowhere in 2007 to present a plausible Theory of Everything, “a unifying idea that aims to incorporate all the universe’s forces in a single mathematical framework”. I do but I missed this visualization of Lisi’s theory posted by New Scientist in late 2007. You may want to break out the bong for this one. (thx, matt)
Let me point to the Adjacent Possible of the biosphere. Once there were lung fish, swim bladders were in the Adjacent Possible of the biosphere. Before there were multicelled organisms, the swim bladder was not in the Adjacent Possible of the biosphere. Something wonderful is happening right in front of us: When the swim bladder arose it was of selective advantage in its context. It changed what was Actual in the biosphere, which in turn created a new Adjacent Possible of the biosphere. The biosphere self consistently co-constructs itself into its every changing, unstatable Adjacent Possible.
If the becoming of the swim bladder is partially lawless, it certainly is not entailed by the fundamental laws of physics, so cannot be deduced from physics. Then its existence in the non-ergodic universe requires an explanation that cannot be had by that missing entailment. The universe is open.
We determined that, generally speaking, the gravity in each Mario game, as game hardware has increased, is getting closer to the true value of gravity on earth of 9.8 m/s^2. However, gravity, even on the newest consoles, is still extreme.
In Super Mario 2, Mario experiences a g-force of 11 each time he falls from a ledge, a force that would cause mere humans to black out. In Madden 2006, the game’s fastest cornerbacks can run the 40 in 2.6 seconds. (via waxy)
It’s true that after 300 years, nuclear waste is still about 100 times more radioactive than the original uranium that was removed from the earth. But even this isn’t as scary as it sounds. If the waste is stored underground in such a way that there’s only a 10 percent chance that 10 percent of it will leak — which should be more than doable — the risk will be no worse than if we had never mined the uranium in the first place.
Muller asserts that safe nuclear power is a solved technical problem and that the use of it is a political issue.
It looks like black holes can grow to be as massive as 50 billion suns. How massive is that? It’s approximately 99 duodecillion kilograms….which is a 99 followed by 39 zeros. (Put another way, if you had 99 duodecillion dollars, you could buy as many PlayStation 3s as you wanted. Blows your mind, right?)
On the basis of their measurements, the team concluded that if the photons had communicated, they must have done so at least 100,000 times faster than the speed of light — something nearly all physicists thought would be impossible. In other words, these photons cannot know about each other through any sort of normal exchange of information.
The Higgs Boson: 95%. The Higgs is the only particle in the Standard Model of Particle Physics which hasn’t yet been detected, so it’s certainly a prime target for the LHC (if the Tevatron doesn’t sneak in and find it first). And it’s a boson, which improves CERN’s chances. There is almost a guarantee that the Higgs exists, or at least some sort of Higgs-like particle that plays that role; there is an electroweak symmetry, and it is broken by something, and that something should be associated with particle-like excitations. But there’s not really a guarantee that the LHC will find it. It should find it, at least in the simplest models; but the simplest models aren’t always right. If the LHC doesn’t find the Higgs in five years, it will place very strong constraints on model building, but I doubt that it will be too hard to come up with models that are still consistent.
The list also functions as a nice overview of what’s happening at the edges of our physics understanding. (via 3qd)
Quantum mechanics is the girl you meet at the poetry reading. Everyone thinks she’s really interesting and people you don’t know are obsessed about her. You go out. It turns out that she’s pretty complicated and has some issues. Later, after you’ve broken up, you wonder if her aura of mystery is actually just confusion.
Would like to see the list for men as well. (via snarkmarket)
Physicists of the 20th Century on Banknotes (5 MB PDF), including Marie & Pierre Curie on a short-lived 500 franc note, Niels Bohr on a Danish 500 kroner note, and Nikola Tesla on several notes from Yugoslavia and Serbia. The author of the article is Steve Feller, physics professor at Coe College and my college advisor. Feller has a keen interest in numismatics and recently published a book about the money used in WWII camps.
The element gallium is in very short supply and the world may well run out of it in just a few years. Indium is threatened too, says Armin Reller, a materials chemist at Germany’s University of Augsburg. He estimates that our planet’s stock of indium will last no more than another decade. All the hafnium will be gone by 2017 also, and another twenty years will see the extinction of zinc. Even copper is an endangered item, since worldwide demand for it is likely to exceed available supplies by the end of the present century.
Many of the elements listed above are used in the construction of computer equipment and flat-panel TVs.
The “Pillars of Creation” may be the most iconic Hubble photograph ever taken. “Located in the Eagle Nebula, the pillars are clouds of molecular hydrogen, light years in length, where new stars are being born,” says Aguilar. “However, recent discoveries indicate these pillars were destroyed by a massive nearby super nova some 6,000 years ago. This is a ghost image of a past cosmic disaster that we won’t see here on Earth for another thousand years or so-and a perfect example of the fact that everything we see in the universe is history.”
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