The ability to solve n-body aside they are limited in accuracy to what they know about the begining conditions and the ability to account for all mass at as close to the atomic scale as possible. By using.0003 of the hubble mass divided into 10 billion points they create a limit to their accuracy right there.
I'm and engineering-physics undergraduate with a strong interest in programming, but astronomy is just a small hobby (I think I wrote astrology somewhere; <embarrassed>). Could you explain that again?
I don't see how this is supposed to even lead to a coarse model for understanding how the system behaves. IE if the coarse model dosn't behave roughly like the system you can't derive trends from it.... its just chaos inherrent in the method * inherrent error of the the unknown factors of the begining of the universe compounded over billions of years worth of modeling the 10 billion points interactions which equals nothing relavent to reality.
Can't that argument be applied to simulations of weather patterns? And they are reasonably predictive right now. Why do you think that cosmological simulations are different?
If you have a license to use Apple's patents on anti-aliased fonts, then you can rebuild FreeType's Font Engine to support pretty fonts. They switched it off due to legal uncertanities, but it is still included with the source code. You have to edit an header file, determine where your Linux desktop distribution stores FreeType's libraries, remake, and install it (as root) to enable it. That sounds complicated, but it is actually really easy to do. Just follow the instructions; you don't have to be a hacker to do it!
Note: I had a well written response; however, I lost it due to some slash bugs.:-( Kinda demoralizing
It just seems silly to me to attempt a N = 10 billion problem when we can't solve an N = ~70 ( roughly known objects in the solar system )
If you had a solution to N>3 problems, then you wouldn't need a simulation. The n-body problem involves getting exact equations of motion (e.g. x(t)=some polynomial) for non-trivial systems involving more than two particles (with only initial conditions and a few laws of physics as guides). If you could get a solution-equation, then just plug and chug until you get the answer you seek.
Simulations help when you can only find approximate solutions (using things like, say, Euler's Method). They help you see general trends since you can't derive them. The point is to figure out the general trends and behavior of a system - not an accurate model of any kind.
No need to insult me. My question was a suggestion as well as a query for some discussion.
As for phishing caller-id, I'd tell them that I would call them back to confirm that their caller-id was legit. Wouldn't that provide enough security against fraud? You have the oppertinuty to confirm their identity then call them back to continue the conservation.
"The primary goal for computer simulations such as these are to understand how and why they don't work - not to test current theories."
And yet current theory is what has to be used to set up the simulation.
While I find this excercise interesting I also find it a tad ridiculose. So many simplifications have to be made to even attempt it and the whole thing is based on some assumptions that are not necesarrily cold hard fact...
The primary goal for computer simulations such as these are to understand how and why they don't work - not to test current theories.
For instance, many different attempts had be conducted before an computer model of Earth's magnetic field exibited magnetic field reversal - and even then, it wasn't exactly like how the geological evidence shows. However, it suggests a basic model that can be adjusted to more accurately describe our planet's core.
It is the same with this attempt to simulate a Universe. The goal is to understand how things interact, how the simulated universe differs from our Universe, and why it differed. Some things would be due to problems running computer simulations with a Von Neuman Machine (such as the "three body problem"). Other errors will be caused by problems with our current model. If the two effect can be seperated and analysed, then advancements could be done in both computer science (e.g. weather forcasting) and cosmology. That's the point of this excersize.
Why didn't you look up your bank in the phone book to verify it was their number? Wouldn't that have given you confirmation as well?
Re: The reason PBRs are safer than PWRs.
on
China Goes Nuclear
·
· Score: 1
With a bead reactor, you have to have the coolant to have a reaction, so if you lose the coolant (which is pretty much your most likely failure in a power plant), all that happens is your reaction grinds to a halt and cools down. No super critical, no meltdown.
As I previously explained in a post about The Causes of the Chernobyl Accident, PWR reactors also require coolant for any reaction to proceed. This is because they require a relatively large number of slow neutrons to be absorbed by relatively averagely refined fuel rods.
Pebble bed reactors tend to be safer because of a simpler design, more modern failsafes, a better ability to quickly scale power generation, and chemically unreactive coolant. Furthermore, a PBR can't support a chain reaction at the required higher temperatures due. Those are some reasons why I agree that they have a better design.
However, nuclear fission reactions in both a PWR and a PBR tend to "fiss out" with loss of coolant. They just do it each by a different mechanism.
Modern bead reactors of the type the chinese are building are VASTLY less likely to meltdown than any reactor currently running in the US. The coolant in a bead reactor actually catalyses the reaction, so without coolant, there is no reaction.
I agree with your premise; however, I disagree with your logic. How does the fact that coolant in a pebble bed reactor help catalyse the reaction make them safer than American PWRs? After all, most American PWRs (because of a PWR's design) use coolant as a moderator; in other words, it helps catalyse the nuclear reaction by slowing neutrons so they can be absorbed.
It should be illegal to ask about your gender or race on an application.
While I agree in principle, I don't think it is practical.
For instance, there is nothing wrong with gathering demographic data about race and gender applicants for statistical purposes (such as a check that the "system" is working). There could be a required step where the data on the applicant's race or gender is filtered out for the people who make the decisions. Same effect.
However, many people discriminate against people who have "female-sounding" or "african-sounding" names. Do you now require everyone being identified by a number? - but that's not necessarily a problem. What about letters of recommendation, essays, awards, and other things that often hint at the applicant's identity/race/gender/age/other discriminatory attribute? It can become a logistical nightmare to keep these thing out of the process!
Here's another possible solution. Why not use affirmative action on the acceptance committee rather than the applicants themselves? If you have a female/male of each an African-American, an European-American, a Native-American, and other groups on the committee, then how can their be discrimination against any one group? Each applicant decides who judges their application, and a random computer decides among the ties. For institutions where illegal discrimination has been shown, wouldn't the above process work well?
(Probably not... but I hope it at least prompts discussion.)
Arthur C. Clark once said that any sufficiently advanced technology is indistinguishable from magic. That was the point of your first three issues with 2001. The idea was that the aliens were so far advanced ahead of us Homo Sapiens that they seemed like Gods. We couldn't begin to comprehend what they were like or how their technology worked.
As for HAL 9000, I think he is more plausible than not. We might not be able to make thinking machines until 3004, but it will happen eventually. And unless you think intelligence and emotions are separate entities (I don't), the computer intelligence will have our faults as well.
Geeze I wish I had a PVR like a TiVo. I am also a little confused by describing Farscape as intelligent. To me, that means the plots and themes inspires the viewer think deeply about issues (like Star Trek) or neat logical dilemmas (like hard sci-fi such as Asimov's book, I, Robot). Sometimes Farscape satifies these requirements, but often the show is just about character development for the sake of character development. What's the point in developing characters in fiction if it doesn't have a deeper meaning? Especially if the said characters aren't likeable!
As for the alien words, they tend to be more distracting than interesting when used so haphazardly. I mean, what's the point? They don't emphanize things at all since the meaing is, well, alien. The novelty wears off fast: as in pilot-of-Battlestar-Galactica-then-annoying fast. That is why non-experts hate technobable as well; you can't communicate well with different vocabularies.
If you watch episodes out-of-order, you will get a bad experience.
Boy, is that true! I never really connected with Farscape since I couldn't figure out what's happening! I'd watch one episode, where everyone on Moya is at each other's throats. Then - in a different episode - the characters like each other. Even within an episode, the plot is often nonlinear so I often get really confused if I was late and haven't seen the first act. Furthermore, the alien words - frell, cycle, etcetera - don't make sence if you don't know what they stand for! I can hardly anticipate if an even is five seconds, hours, or days away.
Now this writing and dialog style would be great for a novel or series of books - or even a movie - but it sucks for a television series. You can control what you read or see in those venues, but television relies on a schedualed affair. In essence, you have to be a diehard fan to understand the series. If you happen to be busy when Sci-fi shows Farscape and can't catch a few episodes, then nothing makes sense in the next show! Farscape is a space soap much more than Bablyon 5 or the last three Star Trek spin-offs.
(Another offtopic complain involves the stories themselves. When the series first came on, I hated all the characters except for Moya, Pilot, and John Criton, and he even tries my tolerance at times. There is simply very little redeaming qualities in most of the others. While a movie, soap opera, or miniseries thrives on such antiheros, it makes a casual viewer turned off of the series as a whole. I cared about Spock and Sinclair. I got disconcected with the characters on Farscape and never cared for them or to see their adventures. That's why that show usually doesn't interest me.)
In particular, Graham claims that terser languages are more powerful, because studies have shown that coders churn out a pretty constant number of lines per day, regardless of the programming language. Java is anything but terse.
That is an insightful essay, but I disagree with a few of Graham's assumptions. For instance:
I think a better measure of the size of a program would be the number of elements, where an element is anything that would be a distinct node if you drew a tree representing the source code. The name of a variable or function is an element; an integer or a floating-point number is an element; a segment of literal text is an element; an element of a pattern, or a format directive, is an element; a new block is an element. There are borderline cases (is -5 two elements or one?) but I think most of them are the same for every language, so they don't affect comparisons much.
I think that this isn't broad enough. Whenever I read an novel or something, I tend to parse the text in discrete blocks. As a programmer, I tend to do the same with source code. It is almost trivial to convert any small code block between any language (normalized for one's familiarity with the language's syntax, of course).
However, the really hard part about programming - the part that requires skill - is understanding what small blocks of code to write and how to connect them together. Languages, which have features that help identify the relationship between code blocks, are easier to read. And I'm more productive in languages where it is easy to reconcile the ever-chaning model in my head with the code on the screen.
So instead of measuring terseness in code-elements, I perfer to use "natural" code-blocks built into each language. It doesn't really matter how many elements are required to implement a loop. In fact, I usually write code with "idiot-proof" variable names and verbose comments (though balanced with convenience). IOW documenting as I write. However, support for tying code blocks together - i.e. functions, objects, classes, prototypes, aspects, iterators, templates, and others chunks of code - is the real power of a language.
Any references? Because I thought that there were other factors required for a nuclear bomb.
A pool of melted fuel rods won't be pure, so it would have to be a larger mass in a smaller area than in a nuclear bomb. Furthermore, I doubt that the rate of reaction from the lava would be fast enough to create for a nuclear explosion.
As the neutron density, and hense about of heat generated, increased, the pool would expand in size and an equilibrum would be established. That's mainly why I'm skeptical of your claims.
The nuclear reaction gets out of control, starts producing too much heat, and before long the fuel melts together to make a nice nuclear bomb.
I don't think a nuclear bomb can be created (in the style of WWIII weapons); however, a radioactive lava (liquid rock and metal from the control and fuel rods and whatever else is in the particular reactor) can form which may melt into the beadrock. Of course, that's the worst case accident - practically impossible in properly designed reactors.
The Chernobyl accident's final precipitator was pulling the control rods *out* too much. The problem is that accumulated xenon (I believe it was xenon, could have been another material) was poisoning the reaction. Then when the xenon finally "burned off", the reactor suddenly had no control rods impeding the reaction. The end result was a steam explosion that blew the lid off the reactor.
Pulling out the control rods allowed the conditions for the accident to occur. However, about nine seconds before the accident the operators tried to put them back in (01:23:40 at The Chernobyl site and accident sequence). I think this event directly caused the explosion in the reactor.
Sorry for double posting; I was just reading my report (co-authored with Nathaniel Hayes). You might find a particular paragraph interesting:
While Reactor IV was shut down for routine maintenance a test was run to see if the reactor's turbine could power the emergency cooling system, in the event of a power outage, before the diesel generators powered up. If the test proved acceptable, this would ensure the core would remain at a safe temperature, as the emergency cooling system - run by the diesel generators - became operational.
As the shutdown began, the power of the reactor was reduce to 720 MW (t) [8], less than one-third its maximum output. And the ECCS - Emergency Core Cooling System - was disabled to allow a further reduction in power. At 12:28 AM [7] the power had reached 500MW (t), which was the amount of power agreed upon for the test. At this time the control of the reactor would be given to the automatic regulating system. But the operator failed to initiate the transfer of control correctly [9] and the power sharply decreased to 30 MW (t).
7 - The Uranium Institute. Retrieved Saturday, September 25, 1999 from the World Wide Web: http://www.uilondon.org
8 - NEA Committee on Radiation Protection and Public Health. "Chernobyl Ten Years On" Nuclear Energy Agency (NEA). Retrieved Monday, September 26, 1999 from the World Wide Web:
http://www.nea.fr/
9 - Sich, Alexander Roman, PhD. "The Chornobyl [sic] accident revisited--source term analysis and reconstruction of events during the active phase" Thesis (Ph. D.), Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1994.
Apparently I have forgotten much - though granted that we wrote the paper five years ago.
Chernobyl was an antiquated design by the time it was built and they were testing what would happen if they did several stupid things at once.... Should you do several stupid things at once in a modern reactor, the reactor will fail in such a way that it shuts down.
IANANP, BIWARPFMEAC*. I'd like to elaborate a little bit on this point:
Fission occurs when a heavy radioactive nucleus (in the control rods) absorbs a neutron and splits into two smaller nuclei and a few extra neutrons. These new neutrons can be absorbed by other heavy nucli, and more fission occurs.
Now most of the neutrons released move too fast to be absorbed by a nucleus; instead, they just bounce off. In order for a sustainable reaction to take place, a material - called the moderator - is required to slow down the neutrons so that they can be absorbed.
Most modern** nuclear reactors are pressure-water reactors. This means that they use water as both a coolant and as a moderator. If the water excapes, then the reaction fissles out.
However, Chernobyl was initially designed with a solid moderator built into the reactor vessel. (I think it was graphite, if I remember correctly.) It used water purely as a coolant. So when the coolant leaked, the reactor kept on fissing atoms and the reaction got out of control (although not fast enough for a thermonuclear reaction).
That wasn't the only problem. The reactor's personal paniced and tried to send the control rods in too quickly. While the control rods were halfway in, neutrons bounced into the bottom of the reactor and formed a critical amount for a chain reaction. At the same time, the heat of the reaction and loss of pressure from the origional malfunction turned the leftover water into steam pockets also in the bottom of the reactor. Soon after, an explosion ruptured the reaction vessel.
Perhaps the primary cause of the accident (and of TMI) was the confusing interface to the equipment! Some devices used red lights to signify emergency conditions, while others used green or another color. Instruments were hard to read and slow to respond. An ergonomical failure contributed to the accident.
Today, most control rooms have learned from the mistakes at TMI and Chernobyl. They are easier and more consistant to use. However, even more improvements are possible with new designs. It is a pity that nobody will allow the old workhorses ot be retired.
* I am not a nuclear physicist, but I wrote a research paper for my Engineering Analysis class.
** "Modern Nuclear Reactor" is somewhat of an oxymoron. Due to NIMBY feelings among the general public, most commercial nuclear reactors are old (60s-70s era) and modern designs are never given a chance despite the improvements in efficiency, safety, and (less) waste production.:-(
Just wait until the day when an athlete's medal is revoked and barred from further competition - not for cheating by drugs or otherwise - for sharing their experiences with others. The public outcry for reasons of either nationalism or 'simple' human decency will not allow it! On that day there shall be such an outcry that no one will ever again strive to participate under the Olympic's current administration.
I disagree. On page 555 of the fourth edition of "Classical Dynamics of Particles and Systems" by Jerry Marion and Stephen Thornton (Harcourt College Publishers, 1995):
The term rest mass resulted from Equation 14.46 when u = 0, and the classical form of momentum was thus retained: p = mu. Scientists spoke of the mass increasing at high speeds. We prefer to keep the concept of mass as an invariant, intrinsic property of an object. The use of the two terms relativistic and rest mass is now considered old-fashioned. We therefore always refer to the mass m, which is the same as the rest mass. The use of the relativistic mass often leads to mistakes when using classical expressions. (emphansis theirs; typos mine)
Slashdot Mirror
Interesting.... A quick google for site:apple.com freetype seems to indicate that Apple seems to be redistributing FreeType - bundled with XFree86 - as an extra add-on to Darwin (note: not in Darwin itself). Does this mean that it has been released under Freetype.org's license?
I think I'll ask /. about this.... Thanks for the inquery! :-D
I'm and engineering-physics undergraduate with a strong interest in programming, but astronomy is just a small hobby (I think I wrote astrology somewhere; <embarrassed>). Could you explain that again?
Can't that argument be applied to simulations of weather patterns? And they are reasonably predictive right now. Why do you think that cosmological simulations are different?
If you have a license to use Apple's patents on anti-aliased fonts, then you can rebuild FreeType's Font Engine to support pretty fonts. They switched it off due to legal uncertanities, but it is still included with the source code. You have to edit an header file, determine where your Linux desktop distribution stores FreeType's libraries, remake, and install it (as root) to enable it. That sounds complicated, but it is actually really easy to do. Just follow the instructions; you don't have to be a hacker to do it!
Note: I had a well written response; however, I lost it due to some slash bugs. :-( Kinda demoralizing
If you had a solution to N>3 problems, then you wouldn't need a simulation. The n-body problem involves getting exact equations of motion (e.g. x(t)=some polynomial) for non-trivial systems involving more than two particles (with only initial conditions and a few laws of physics as guides). If you could get a solution-equation, then just plug and chug until you get the answer you seek.
Simulations help when you can only find approximate solutions (using things like, say, Euler's Method). They help you see general trends since you can't derive them. The point is to figure out the general trends and behavior of a system - not an accurate model of any kind.
No need to insult me. My question was a suggestion as well as a query for some discussion.
As for phishing caller-id, I'd tell them that I would call them back to confirm that their caller-id was legit. Wouldn't that provide enough security against fraud? You have the oppertinuty to confirm their identity then call them back to continue the conservation.
Chill my brother.
Sigh, I hit enter after accidently typing tab and the form was submitted. /. really should make preview the default action for the form. Darnit!
The primary goal for computer simulations such as these are to understand how and why they don't work - not to test current theories.
For instance, many different attempts had be conducted before an computer model of Earth's magnetic field exibited magnetic field reversal - and even then, it wasn't exactly like how the geological evidence shows. However, it suggests a basic model that can be adjusted to more accurately describe our planet's core.
It is the same with this attempt to simulate a Universe. The goal is to understand how things interact, how the simulated universe differs from our Universe, and why it differed. Some things would be due to problems running computer simulations with a Von Neuman Machine (such as the "three body problem"). Other errors will be caused by problems with our current model. If the two effect can be seperated and analysed, then advancements could be done in both computer science (e.g. weather forcasting) and cosmology. That's the point of this excersize.
Why didn't you look up your bank in the phone book to verify it was their number? Wouldn't that have given you confirmation as well?
As I previously explained in a post about The Causes of the Chernobyl Accident, PWR reactors also require coolant for any reaction to proceed. This is because they require a relatively large number of slow neutrons to be absorbed by relatively averagely refined fuel rods.
Pebble bed reactors tend to be safer because of a simpler design, more modern failsafes, a better ability to quickly scale power generation, and chemically unreactive coolant. Furthermore, a PBR can't support a chain reaction at the required higher temperatures due. Those are some reasons why I agree that they have a better design.
However, nuclear fission reactions in both a PWR and a PBR tend to "fiss out" with loss of coolant. They just do it each by a different mechanism.
I agree with your premise; however, I disagree with your logic. How does the fact that coolant in a pebble bed reactor help catalyse the reaction make them safer than American PWRs? After all, most American PWRs (because of a PWR's design) use coolant as a moderator; in other words, it helps catalyse the nuclear reaction by slowing neutrons so they can be absorbed.
So that's why TPTB named the main character of Sliders was named Quinn Mallory?
(Offtopic.) That show is frustrating! So many cool nuancies.... so many bad plots....
While I agree in principle, I don't think it is practical.
For instance, there is nothing wrong with gathering demographic data about race and gender applicants for statistical purposes (such as a check that the "system" is working). There could be a required step where the data on the applicant's race or gender is filtered out for the people who make the decisions. Same effect.
However, many people discriminate against people who have "female-sounding" or "african-sounding" names. Do you now require everyone being identified by a number? - but that's not necessarily a problem. What about letters of recommendation, essays, awards, and other things that often hint at the applicant's identity/race/gender/age/other discriminatory attribute? It can become a logistical nightmare to keep these thing out of the process!
Here's another possible solution. Why not use affirmative action on the acceptance committee rather than the applicants themselves? If you have a female/male of each an African-American, an European-American, a Native-American, and other groups on the committee, then how can their be discrimination against any one group? Each applicant decides who judges their application, and a random computer decides among the ties. For institutions where illegal discrimination has been shown, wouldn't the above process work well?
(Probably not... but I hope it at least prompts discussion.)
Arthur C. Clark once said that any sufficiently advanced technology is indistinguishable from magic. That was the point of your first three issues with 2001. The idea was that the aliens were so far advanced ahead of us Homo Sapiens that they seemed like Gods. We couldn't begin to comprehend what they were like or how their technology worked.
As for HAL 9000, I think he is more plausible than not. We might not be able to make thinking machines until 3004, but it will happen eventually. And unless you think intelligence and emotions are separate entities (I don't), the computer intelligence will have our faults as well.
Geeze I wish I had a PVR like a TiVo. I am also a little confused by describing Farscape as intelligent. To me, that means the plots and themes inspires the viewer think deeply about issues (like Star Trek) or neat logical dilemmas (like hard sci-fi such as Asimov's book, I, Robot). Sometimes Farscape satifies these requirements, but often the show is just about character development for the sake of character development. What's the point in developing characters in fiction if it doesn't have a deeper meaning? Especially if the said characters aren't likeable!
As for the alien words, they tend to be more distracting than interesting when used so haphazardly. I mean, what's the point? They don't emphanize things at all since the meaing is, well, alien. The novelty wears off fast: as in pilot-of-Battlestar-Galactica-then-annoying fast. That is why non-experts hate technobable as well; you can't communicate well with different vocabularies.
Boy, is that true! I never really connected with Farscape since I couldn't figure out what's happening! I'd watch one episode, where everyone on Moya is at each other's throats. Then - in a different episode - the characters like each other. Even within an episode, the plot is often nonlinear so I often get really confused if I was late and haven't seen the first act. Furthermore, the alien words - frell, cycle, etcetera - don't make sence if you don't know what they stand for! I can hardly anticipate if an even is five seconds, hours, or days away.
Now this writing and dialog style would be great for a novel or series of books - or even a movie - but it sucks for a television series. You can control what you read or see in those venues, but television relies on a schedualed affair. In essence, you have to be a diehard fan to understand the series. If you happen to be busy when Sci-fi shows Farscape and can't catch a few episodes, then nothing makes sense in the next show! Farscape is a space soap much more than Bablyon 5 or the last three Star Trek spin-offs.
(Another offtopic complain involves the stories themselves. When the series first came on, I hated all the characters except for Moya, Pilot, and John Criton, and he even tries my tolerance at times. There is simply very little redeaming qualities in most of the others. While a movie, soap opera, or miniseries thrives on such antiheros, it makes a casual viewer turned off of the series as a whole. I cared about Spock and Sinclair. I got disconcected with the characters on Farscape and never cared for them or to see their adventures. That's why that show usually doesn't interest me.)
That is an insightful essay, but I disagree with a few of Graham's assumptions. For instance:
I think that this isn't broad enough. Whenever I read an novel or something, I tend to parse the text in discrete blocks. As a programmer, I tend to do the same with source code. It is almost trivial to convert any small code block between any language (normalized for one's familiarity with the language's syntax, of course).
However, the really hard part about programming - the part that requires skill - is understanding what small blocks of code to write and how to connect them together. Languages, which have features that help identify the relationship between code blocks, are easier to read. And I'm more productive in languages where it is easy to reconcile the ever-chaning model in my head with the code on the screen.
So instead of measuring terseness in code-elements, I perfer to use "natural" code-blocks built into each language. It doesn't really matter how many elements are required to implement a loop. In fact, I usually write code with "idiot-proof" variable names and verbose comments (though balanced with convenience). IOW documenting as I write. However, support for tying code blocks together - i.e. functions, objects, classes, prototypes, aspects, iterators, templates, and others chunks of code - is the real power of a language.
Any references? Because I thought that there were other factors required for a nuclear bomb.
A pool of melted fuel rods won't be pure, so it would have to be a larger mass in a smaller area than in a nuclear bomb. Furthermore, I doubt that the rate of reaction from the lava would be fast enough to create for a nuclear explosion.
As the neutron density, and hense about of heat generated, increased, the pool would expand in size and an equilibrum would be established. That's mainly why I'm skeptical of your claims.
I don't think a nuclear bomb can be created (in the style of WWIII weapons); however, a radioactive lava (liquid rock and metal from the control and fuel rods and whatever else is in the particular reactor) can form which may melt into the beadrock. Of course, that's the worst case accident - practically impossible in properly designed reactors.
Pulling out the control rods allowed the conditions for the accident to occur. However, about nine seconds before the accident the operators tried to put them back in (01:23:40 at The Chernobyl site and accident sequence). I think this event directly caused the explosion in the reactor.
Sorry for double posting; I was just reading my report (co-authored with Nathaniel Hayes). You might find a particular paragraph interesting:
Apparently I have forgotten much - though granted that we wrote the paper five years ago.
FYI, the most complete reference for my research paper was the Ph.D. Thesis for Dr. Alexander Roman Sich when at MIT:
IANANP, BIWARPFMEAC*. I'd like to elaborate a little bit on this point:
Fission occurs when a heavy radioactive nucleus (in the control rods) absorbs a neutron and splits into two smaller nuclei and a few extra neutrons. These new neutrons can be absorbed by other heavy nucli, and more fission occurs.
Now most of the neutrons released move too fast to be absorbed by a nucleus; instead, they just bounce off. In order for a sustainable reaction to take place, a material - called the moderator - is required to slow down the neutrons so that they can be absorbed.
Most modern** nuclear reactors are pressure-water reactors. This means that they use water as both a coolant and as a moderator. If the water excapes, then the reaction fissles out.
However, Chernobyl was initially designed with a solid moderator built into the reactor vessel. (I think it was graphite, if I remember correctly.) It used water purely as a coolant. So when the coolant leaked, the reactor kept on fissing atoms and the reaction got out of control (although not fast enough for a thermonuclear reaction).
That wasn't the only problem. The reactor's personal paniced and tried to send the control rods in too quickly. While the control rods were halfway in, neutrons bounced into the bottom of the reactor and formed a critical amount for a chain reaction. At the same time, the heat of the reaction and loss of pressure from the origional malfunction turned the leftover water into steam pockets also in the bottom of the reactor. Soon after, an explosion ruptured the reaction vessel.
Perhaps the primary cause of the accident (and of TMI) was the confusing interface to the equipment! Some devices used red lights to signify emergency conditions, while others used green or another color. Instruments were hard to read and slow to respond. An ergonomical failure contributed to the accident.
Today, most control rooms have learned from the mistakes at TMI and Chernobyl. They are easier and more consistant to use. However, even more improvements are possible with new designs. It is a pity that nobody will allow the old workhorses ot be retired.
* I am not a nuclear physicist, but I wrote a research paper for my Engineering Analysis class.
** "Modern Nuclear Reactor" is somewhat of an oxymoron. Due to NIMBY feelings among the general public, most commercial nuclear reactors are old (60s-70s era) and modern designs are never given a chance despite the improvements in efficiency, safety, and (less) waste production. :-(
Just wait until the day when an athlete's medal is revoked and barred from further competition - not for cheating by drugs or otherwise - for sharing their experiences with others. The public outcry for reasons of either nationalism or 'simple' human decency will not allow it! On that day there shall be such an outcry that no one will ever again strive to participate under the Olympic's current administration.
I disagree. On page 555 of the fourth edition of "Classical Dynamics of Particles and Systems" by Jerry Marion and Stephen Thornton (Harcourt College Publishers, 1995):