Bits and Bytes
I am back from 16 days abroad. It is good to be back, even if it is for a short while. While I was away, I collected a couple of links and here they are...
Photographing buildings and other things
I was surprised to learn that taking a photo of the Eiffel Tower at night, when lit up - would technically require a royalty if I published it. So, I looked around and found this link. Now obviously that only applies in the USA, but it was interesting none the less. I can photograph buildings to my hearts content.
Teach Yourself Programming in 10 years
I don't know if it takes ten years, but it certainly will take more than "a week", or "24 hours". Now, in defense of some of these books - like a "Learn Pascal in Three Days" - if you were a seasoned programmer, you could probably learn much of Pascal in three days and be useful with it.
But then again, since when do seasoned programmers buy "Learn in three days" :) They just dive in.
I definitely agree with the sentiment espoused there however. It takes time to become really experienced at something, at anything. TIME. It really does.
Irony
This is almost certainly a joke. But a pretty funny one!
Things we think we know...
I give a short keynote-ish type of talk "Things we think we know". I'll have to verify these are all correct first, but they might make a nice addition. Hey - this is going to be nice, by linking to it, people will read it and tell me if they are wrong :) How easy is that...
posted by Thomas Kyte at 5:50 PM
11 Comments:
Tom,
Just a bit relieved to know the fact#4 that today's nuclear reactors can not meltdown like a nuclear bomb as i l happen to live nearby one of them:)
Though to be fair to them , nuclear plant administration always says here that 90% of their own staff lives within 5 km radius of the plant and that should be a proof enough of their safety...
I am happy that you noted that you would have to verify the "facts" listed on that page before accepting them (Ronnie's old "trust but verify" mantra). All the content presented there is anecdotal making it very hard to believe without verifiation.
Steve
regarding #4...
Nuclear bombs don't really meltdown. And actually nuclear plants do have similar quantities of fissile material to a smaller bomb, but the material is arranged in a geometric configuration optimal for nuclear power generation, but it is impossible for a bomb-like reaction to occur, not just highly unlikely, but impossible.
Also, Chernobyl wasn't a meltdown, but rather a reaction that occurred, through poor design and gross human mistakes, at a rate so fast that the power spike resulted in turning the water into steam almost instantaneously that a steam "explosion" occured, i.e. expanded fast increasing pressure that destroyed the reactor pressure vessel.
Our nuclear reactors are not designed the same and cannot have a Chernobyl style incident.
I grew up nearby a nuclear plant (and have relatives who work there) and always felt safe.
Always knew that degree in physics would come in handy.
#1 is right, in a strict sense. It is really about your "point of view". As an observer in an accelerated reference frame (going in a circle) you will 'feel' a force throwing you to the outside. This is commonly interpreted as 'centrifugal force' but is really just you going in a straight line until the side of the car gets in the way. No force is really pushing you outwards...just your intertia.
#2 is right. The ocean is blue because the sky is blue because of Raleigh scattering. Classic reversal of cause and effect!
#3. Yeah, but...string theory holds for multiple dimensions, and these are really just like another "axis" that can locate a point-in-space. BUT string theory (and a number of other Grand Unifying Theories) allows for parallel universes...and it is in one of these you might find your alter ego!
#4. "Explode like a bomb." Well, explode like what kind of bomb? Chernobyl exploded "like a bomb" caused by a buildup of pressure inside a containment building not built to deal with that pressure. Think "inflate a balloon until it pops."
Mark is right...you need to achieve a critical density of fissile material in order to have an "atomic bomb" explosion and no nuclear power plant (not even breeders designed to make nuclear bomb materials) can achieve this density.
"Western" reactors are far safer designs than "Soviet" reactors, but they're by no means "100% safe". Nuclear power died in the US because of a little 'boo boo' called Three Mile Island.
The problem with *any* water-cooled reactor is managing pressure. Failure to do this will result in "explosive decompression" which could sound like a very small bomb.
New (experimental) reactor designs employ liquid sodium as coolant and run at atmospheric pressure. This Elimiates the pressure problem but introduces new ones (corrosion and water).
#5. Well. Kinda hard to prove. Can a microwave give you cancer? They've been trying to figure that out with cell phones and results have been inconclusive. I'd agree with the assessment that your overall radiation exposure from "the background" (namely the earth and space) is much (much) higher than your exposure from microwaves (and cell phones). BUT that is decidedly different than saying "they won't give you cancer".
The right way to put it is: Microwaves are much less likely to give you cancer than the natural environment. (And the natural environment is less likely to give you cancer than man-made chemicals you're exposed to.)
This is a bit like "buffer cache hit ratio". In the absence of good insturmentation, pick a scapegoat.
Too bad we don't know how to access God's human body "wait event" interface.
#6? Eh.
The reasoning gets weaker as the number of examples gets higher. Case of reasoning fatigue?
And regarding #4 comments:
If you believe that if people live near something dangerous makes it not so dangerous, you should consider people living in earthquake areas, tornado areas or well below sea level, like myself. If you reason about it, it is totally insane. But a lot of us do it. Does that make it safe?
As a reply to the Daily Irreverence pointed out, the sun is yellow because of the particular temperature it is currently at, which has peak radiation in the yellow part of the spectrum. But see this.
And for #4, fission reactions are not required for something to "explode like a bomb." As pointed out, steam reactions can be very explosive, and adding radioactive material is the very definition of a dirty bomb. US Federal regulations recognize concentric areas around nuclear plants called the Emergency Planning Zone (10 mile radius) and Public Education Zone (10-20 mile radius). Residents in those areas get pamphlets explaining what to do if the plant blows up. do you tell people not to open a nuclear waste site for 10000 years? Read any 10000 year old languages lately?
"Basic safety issues have not been resolved in that the potential for catastrophic accidents remains."
I read an article somewhere (unfortunately cannot find it now) that discussed in detail what happened at Chernobyl. Apparently, the operators were running some tests, and had disabled some 15 to 20-odd different and/or redundant safety mechanisms in order to run these tests. Overriding warning signals in the process as well. Within seconds of when the last of the safety mechanisms was disabled, the place blew up (with steam, not a nuclear reaction)
The article was probably the May 1987 issue of National Geographic - highlighting the contributing human elements and the design flaws of the RBMK-1000 reactor...positive void coefficient, control rod riders, etc. ("features" which are not permitted by the US NRC).
The above comments, and the referenced article, emphasize "Caveat emptor", or whatever the Latin equivalent is of "Let the reader beware".
When I read things, (absent reasons not to) I often make an implicit assumption that the author knows what they are talking about, and is presenting an unbiased version. But that is almost never the case. I have learned to always ask myself, what is the author's knowledge and particularly experience, and more importantly, from what point of view is the author coming from...what are their biases.
That doesn't (or shouldn't) cause me to dismiss out of hand what they are saying, but to take that into consideration when I file it away.
Disclosure - I was in the US Navy nuclear submarine service for 8 years, and can understand the nuclear issues.
Scientific American just had an article about a couple of scientists found a ay to make reactors safer and put out more power. THe nuclear fuel is put into rods and the rods generate heat int he 1200 Degree F. range. (high pressure water reactor). These guys changed the solid rods to rods with a hole in the center. Now their is more surface area and the rods can stay cooler (closer to 800 degrees F) and thus safer.
Anyway interesting.
Well I for one have never met anyone who thought that the sky was blue because of the Ocean - maybe we just have better high school physics in the UK (or did 25 years ago- ouch that hurt to work out).
But its the extra dimensions things that get me, they are always being described as being "curled up small" which doesn't help me at all - it's such a 3d analogy, and anyway we don't experience "curled up small" dimensions - for the moment I can satisfy myself that string theory has made very very few empirical predictions (I was corrected a while back when I said none) and that so far none have been observed.
I found Peter Norvig's comments on taking ten years to learn to program interesting, but I think that the best thing he has ever done is his PPT version of the Gettysburg Address.
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