Danijel Gorupec

Center of the Earth... I have no idea how much compression that makes nor if this would be enough for uranium to go critical. I also guess that at temperaures down there, it would not be possible for sedimentation process to generate pure-enough uranium deposits... Still I had this sci-fi thought that maybe some self-regulating uranium reactor could be possible at the center of the Earth (say, uranium sinks due to its wieght, concentrates and criticality is created. Increased temperature then mixes the concentrated uranium with surrounding iron reducing its concentration and keeping criticality under control. Maybe in a pulse regime...one criticality event every several xy millions of yeras killing dinosaurs... oops, I entered the speculation forum...).

Just thinking.... would unenriched uranium go critical if squeezed enough? At 350GPa, maybe?

Hi Enthalpy... possibly yes. I remember my surprise when I discovered the serious drag at ridiculously low speeds. The clutch was intended to run at only 60RPM so I didn't expect much of eddy-current generated drag. If you say that hysteresis drag is predominant at lower speeds (I did not know about this) then maybe this is the reason. I am only not sure what hysteresis exactly do you have in mind (the clutch was DC powered). I suppose that you are referring to the fact that balls rotate and this is what creates the changeable magnetic field on them? Is this hysteresis effect essentially the same thing as the following effect I have in mind: When a steel ball is immersed into a magnetic field, it gets magnetized in the direction of that magnetic field. If the ball is then quickly rotated for a small angle, its magnetization vector also gets rotated because it takes some short time (energy?) for magnetization to realign. Therefore for this short time the steel ball will generate torque trying to return itself to the original position.... Is this effect I am describing real, and if yes, does it have a name? Hysteresis?

Thanks... I guess, because both of you pointed to the same thing, that this is the answer. I knew about this effect, but I was probably too quick to dismiss it, expecting that it would be negligible... What confused me is the fact that half of the clutch is just a piece of metal that is rotating inside the magnetic field. The drag generated is noticable and I expected it. However this relatively small ball bearing immersed into a relatively lower magnetic field generated several times more drag than the rest of the clutch - that is why I got under impression that maybe something else is happening. I guess that if I run the numbers I would get the result that I observed. In any case, it was surprising to me (I am thinking... balls inside bearing not only circulate around, but are also rotating around themselves - maybe this somehow increases the effect).

How does it happening? Is it enough that stell ball moves through a magnetic field, or must it also rotate to generate the drag? I did not have time at the moment to experiment much, but it seemed as if the drag is present at very low speeds and does not depend on speed - however, I might be wrong on that.

Some two yers ago I was designing a small, cheap electromagnetic clutch. I noticed that magnetic field lines would cross (radially) through a ball bearing, but I didn't expect much problems with that. However, it proved that the magnetic field increased the ball bearing drag much more than I expected. I had to redesign the clutch to include an aluminum ring around the ball bearing to provide some magnetic insulation (this increased complexity of the clutch considerably)... Until now I don't understand why did magnetic field increased the drag that much - forces involved by magnetic field were well under the ball bearing limit (normal mechanical forces of the same magnitude, radial or axial, would not increase the drag noticeably).... What do you think? I have a gut feeling that if I place a steel plate in a magnetic field (parpendicular to the plate) and if then I try to roll a steel ball over that plate, the ball would roll with increased drag. But I have no real idea way would that be. Maybe it is something basic and obvious...

It is my thinking that people invariably drift toward religion. I am not aware if ever such an experiment was conducted, but I believe that if we take an isolated group of people (never before introduced to any religion) the group will soon invent a religion. Larger the group, faster the drift... A major religion, might be the stable end-phase of such a drift (and might thus be a beneficial 'invention'). This is how I explained the prevalence of religion to myself. If you can provide a better explanation, I will be glad to hear because this would relieve me of my unpleasant thinking that 'something went wrong with human-mind design'. "Why not herd them in the direction of rational thought?"... Hmm... you did not give up hope yet? I think I did... There is no comfort in rational thought. And I think that maybe it is the comfort that drives people toward religion. Seeking for comfort is not a far-sighted activity for a person. I think that it is possible that the same 'bug' in our mind is responsible for religion, substance abuse, obesity... all these comfort-seeking activities coming from the same or similar cause... And if my speculation is correct then herding people in direction of rational thought might be a very hard task. (Note: I didn't say that it is easy to herd people any way you want. To herd them easily you must provide comforting ideas to them.)

Recently, much to my surprise, I started thinking that maybe large religions do provide benefit to society. I mean, if we suppose that for most people it is necessity to seek for guidance and that most people naturally herd toward 'promising' ideas, then it is good to keep them gathered in large stable groups. Much better than have them wandering around being easily attracted to any 'leader'... If you 'forcefully' take their religion from those people (majority) they will not suddenly become independent thinkers. Instead they will start wandering and will eventually reach Scientology or whatever.... So, lately I see major religions as beneficial because are lesser of the two evils. (Sorry if I sound disappointed with people. I am not. There is nothing wrong with the herding behavior. But when I see herd-leaders that either don't know how to lead or are leading maliciously, you can be sure that I will criticize.)

Hi Sensei... can you tell me more... Did you calculate with sun-tracking panels or fixed ones? Is this 330kWh/month with or without home heating/cooling? Did you also compute the storage battery capacity that you might need to live, say, 90% of the time off grid?

I don't really get your question... do you allow mechanical energy storage (outside humans body) or not? I mean, the golf club is an energy storage device. Why would you allow to store the energy into a moving mass, but not allow to store it into a spring?

Yes, but activism can also back-fire. I think this is what is happening to me - I somehow got sick of activist people that are constantly trying to scare me. I am not listening to them any more, I am just getting angry when I hear that the future is doomed and we will all die... An activist should be aware of this effect. I do support activism, but only at an intellectual/rational level. As soon as it gets emotional, I am cooling off.... Yes, I know that if we only limit ourselves to a rational activism, then we will never reach wide audience -> but, you see, maybe it is dangerous to even try to reach for people that cannot be reached by rational means.

Sorry iNow, I didn't like your OP wording - too aggressive for my taste. I watched the presentation a bit (not too long because my bandwidth is limited) - very beautiful form!... Is it word of God? You see, this is activism - doesn't have much influence on me. I simply learned to be aware of any activism.

Does it mean that in the USA people often produce power from solar, and then use it in their own homes in order to decrease consumption from the grid? Swansont also said something like that... Does it mean that the home produced solar power in the USA is not significantly subsidized if it is sold to the grid? Maybe those questions sound silly to you, but in my country you always sell everything you produce (because it is heavily subsidized) and then you buy back all the energy you need by a cheaper price. At least that was the situation not that long time ago, but I am not 100% sure if it is still the same.

From the OP: "truly mixed" is hard to define, but I think I understand what the question was about. Moontanman asks if one is genuinely better than the other one (mammals vs dinos), or is it that both actually use the same 'technology' just optimized in somewhat different way.... Or what is it that you wanted to ask by the 'truly mixed', Moon? At least I would like to hear opinions about the above dilemma. Note that because modern mammals are of later design, it does not mean that they are necessarily more advanced. It might be that dinosaurs were very advanced and then... bang - the reset happened and the evolution is now starting from the middle again. BTW, there is one more thing that I read throughout this thread - in what way would one non-coordinated group sustain its dominance over the other group? I don't think dinosaurs were racist pigs that were intentionally suppressing mammals. How could they prevent mammals to slowly take over? What is it that prevents today birds to step down from the trees and slowly take over the land?

Right... We are departing from the theme now, but when I read your post I start thinking that maybe evolution is not as efficient in filing niches as we usually think it is (at least, I was imagining an efficient evolution). Okay, maybe in some cases some 'exotic' species moved in because of environmental changes (like temperature change), but as you said there certainly are many examples where exotic species were just a better fit, or just exploited an unused niche... Still I think that if you choose a random dinosaur and place it here in some random environment (or vice versa) it is unlikely the 'exotic' animal will flourish. But when I consider that the evolution might be inefficient, then I must agree with you that it probably would be possible to find a suitable today's environment for many dinosaur species. ... I also noticed that you said that you believe 'egg laying' is a disadvantage for dinosaurs. Why do you think so? I would be cautious while making such claim because egg laying might give them opportunity to generate much larger number of offspring and this can also be a very successful strategy.

Hmm... I was under impression that this actually happens rarely. I thought that most times the transferred species just die out without anybody noticing it. I thought that such scenario rarely happens if the niche is already taken or non-existing.... I speculate that it only looks like a probable event to us because we only notice successful cases. Anyway, I believe that if we transfer an animal into environment that is different than the environment that created the animal, it is unlikely the animal will manage. Especially if the animal is as complex as a T-Rex.

I would say that we should try to make such 'repairs' only if the new stable state is yet not reached - that is, only while the ecological system is still largely in transition caused by our influence. Once the new stable state is mostly reached, any repair effort should be regarded as a new disruption. This means, I believe, that that there is only a brief time to make any repair. This also means that no repair should be taken if the environmental change happened slowly enough so that the system was always in a stable state.... However in case of some sudden disruption (like an oil spill), we should try to make repairs as quickly as possible. Anyway, I think that the word "prevention" should be the ecological mantra, not the "repair". But I am a great supporter of making lost species live again! Only they should be studied in closed environments - never released.

HRS, I don't know if you are aware, but there are hall sensors and hall switches. I understand you need a sensor (analog output), while switches (digital output) seem more common today. But I don't know if there is any hall analog sensor in a CD/DVD player, sorry.

The three assumptions in the above statement might be questionable. “Nuclear plants make a country more vulnerable to a military attack.” However the opposite might also be true - a country that fails to adopt the nuclear energy might eventually become weaker and thus become an easy target. Adopting this energy source might not be a matter of choice, but a must under competition pressure. The Pandora box might already be open and whoever wants to win will need to adapt, not ignore. “Nuclear plants are valuable military targets.” For an attacker with limited military resources it might be better to first disable target’s abilities to fight back - the radiation pollution bleeds a victim too slowly. Radiation spread might also affect neighbor countries that might not show much sympathy. Finally, if an invasion is planned, attacker’s foot soldiers might suffer too. “It is known what the uninhabitable radiation level is.” In fact, a country will define the uninhabitable radiation level as the lowest figure the country can afford. In a crisis event, the country will simply redefine the uninhabitable radiation level to a higher figure. The real uninhabitable level at which human society cannot progress any more is not known because humans are adaptable creatures. It might be much larger than that of the Pripyat city… In parallel, Lesotho population and GDP numbers can still grow despite the fact that the average life expectancy decreased significantly due to the disease. My personal opinion is that arguments that start like “Peaceful usage of nuclear energy is too dangerous because in the case of war…” sound just weird.

But why would anyone spend a perfectly good bomb such way when there are cities around?

If we are talking about terrorism, it would be easier to hijack a nuclear plant and then blow it away by pushing right buttons, than to hijack an armed military plane and then attack the plant. So, I don't think that the existence of bunker busters changes that much. Generally speaking, compared to other possible safety problems with nuclear plants (inherently bad designs, sloppy maintenance, saving money when one should not, untrained personnel...), terrorism issues seem to me as an "overpriced" argument. Whenever I hear someone is pushing terrorism issues in front of his/her argument list, I get worried that his/her motivation is to produce irrational fear instead to provide rational arguments.

Beautiful observation... until now I was not aware of that.... He he...now I am actually speculating that maybe all advanced civilization guys are actually very small - having their bodies engineered into a submillimeter range.... Such body modification would certainly help us solve some of our own energy problems. (hmm.. and smaller creatures can also probably think faster - there could exist a pressure for an intelligent being to have physically small brain).... Yes, maybe their megastructures are in a ten-meter range

I was referring here to heating homes from a thermal plant waste heat - in a sense that if you already have the thermal electrical plant, then you can cheaply heat homes with that waste heat (PV/Wind do not offer this possibility) - this in a sense increases thermal plant efficiency. I was not referring to price of electricity from nuclear or fossil-u plant. (Btw, I am only partially agree that the nuclear produced energy is more expensive than wind - we can discuss this if you want, but I am afraid this could be off topic here?) I agree that public would not accept home heating from nuclear plant even if it is from its tertiary circle. But I don't think that, technically, there is more radioactivity problem with nuclear plant tertiary circle than it is with geothermal heating... Do you disagree? I mostly accept your other claims.

Nice one... It just occurred to me that we do not see any "show off" from them. We people enjoy erecting large structures just to show how great our nations are.... Compared to us, these advanced civilizations must be very non-existent or very humble. They are not even showing some star-size art. Must be they also have small budgets for culture. .... Btw, I am just thinking about Dyson spheres... I am imagining a whaling ship captain in 1650 who is dreaming about a sailboat capable of transporting 100000 tons of whale oil. He concludes that one day people will have the technology to make such large sailboats. But today we do not use sailboats to transport oil, instead we are using diesel-powered boats. Building such a large oil-carrier sailboat would look a bit silly... That is why I don't expect much Dyson spheres around. It might look like a good and advanced idea to us now, but once when we will have the technology to actually build one... well, it will look just too cumbersome and silly. Our neighbors might ridicule us.

hmm... Is anyone saying that the nuclear energy is not safe already? On what ground? Many kids are truly terrified of the closet monsters, but those kids are never in a real danger. When most people say "how dangerous reactors are", they actually mean "how scary reactors are". Because this is an engineering forum, I expect clear wording here. What is it about nuclear reactors needs an urgent improvement - their safety record or public opinion about them? Yes, I think that we should improve the nuclear reactor safety records a lot! As well as for cars, airplanes, drugs, food and anything else... What causes me a great pain is when I hear an engineer saying "this is bad, throw it away" instead of "this is bad, it should be improved". What kind of an engineer would not like to try to improve something? Nuclear energy is a recent discovery and a new technology - we do not throw away discoveries that easy! New technologies are only found once in a hundred years. I don't think that public opinion about nuclear energy is healthy at the moment. Even if we declare present technology as too dangerous, the "destroy all and stop everything" public stance seems unhealthy. At least some positive attitude to future technology research should be present. We engineers failed to provoke at least that. Anyway, my answer to the OP is: you posted it in the wrong forum. Engineers cannot make that technology appear safe to the public any more - it is too late. Rebranding is needed - please contact the marketing department. Acme, this was hilarious! Did you do it on purpose? It is not that I agree with your quoting, but I still find it funny ... I almost missed it.