Danijel Gorupec

Hmm.. except to assist navigation during migrations, which would probably require keeping time for week(s) within one hour, I must admit that I can't really point out some obvious advantage. However, I have a vague feeling that having 'absolute' sense of time is just better than not having it - an animal could better synchronize with others in the pack and thus better use its own time (less checking outs:... my pack leader 'commanded' 1 hour resting time, so I sleep for one hour and wake up just on time... that female was fertile exactly 48.3 days ago, so I don't need to bother sniffing her but because 'it' is not going to happen). So the actual question, IMO, is: is it so 'expensive' to have a clock? Why?

Without looking at my watch and checking other clues, I am fairly incapable to keep the record of time accurately - I close my eyes, cover my ears and then try to guesstimate when one minute passes... I usually miss a lot, but probably not much more than an average human. I am not sure if this is a skill that can be learned? But, maybe there are animals that are much better at this. Is there any reason why some animal could not have a really good innate timekeeping abilities (without looking at outside clues)? I would be kinda disappointed if evolution found no better solution - is timekeeping a useless trait or is this just a hard problem? Is there any research how good are animals at 'internal' timekeeping? Is an accuracy of 5 minutes per day at all achievable for an organism? (I was reading about homing pigeons and was thinking how useful it would be for a pigeon to have a good inside-head-clock so that it roughly knows the longitude... But I am not asking about pigeons.)

Yes, the effect continues past the geosynchronous orbit. (The slow down / speed up of earth rotation as you move the mass up / down the elevator is the same process as when ice skater stretches / withdraws his limbs to control spin speed. A standard elevator in a skyscraper does the same to the earth rotation... You can read more about conservation of angular momentum and Coriolis force.) Yes, excreting a lateral force by some engine will also change the speed/direction of earth rotation (say, a rocket motor is fired outside atmosphere in a direction lateral to the elevator). Any useful space elevator will have to be engineered to cope with some lateral force (as you noticed, such force is generated even when you only move a mass along the elevator) and will thus not collapse if the force is within limits. I guess that a space elevator will act as almost non-dampened pendulum (at least for 'small' amplitude oscillations). I am not sure if this could be a problem nor what would be the best way to deal with it. I suppose that mass transfer up/down will be scheduled so that it acts against oscillations.

LOLy question... I really don't have any problem with this. I don't think there is any injustice about this fact - Americans earned their economic power by hard, smart and organized work. (How is this money divided among American citizens is another question and not much of my concern ). I do however find amusing the fact that Americans try to spread democracy by military actions. It just looks somewhat immature to me. But you have this strong army so I suppose: 'if you have a hammer, all problems look like nails'

If you only need for your personal use (coarse drawings) then you can also use Math-o-mir. I made this in about 10 minutes.

There is one thing that remains unanswered in this thread... It is not obvious to me how can low concentrations of antibiotics create bugs resistant to high concentrations of antibiotics? There are hints in this thread that this is an obvious consequence, but I don't see it clearly. I know very little about antibiotics, so I use following analogy: If some bacteria does very good at 25 degrees Celsius, but I increase temperature to 40 degrees Celsius forcing them to develop coping mechanisms and change themselves - how can this create a super bug that can live in autoclave temperatures? My understanding is that organisms change only as much as needed, not more. To be clear, I do expect that higher-than-natural concentrations of antibiotics will somewhat increase the probability of super-bug creation. How much this probability is increased is an important factor of the problem discussed in this thread. If added antibiotics increase likelihood of super-bug creation only marginally (in comparison to natural likelihood) then maybe it is worth it. ---- Another thing comes in mind: if, as I understood this thread, farmers give antibiotics to animals not for therapeutics effects but for side-effects, wouldn't then be worth investigating this issue a bit further? Can we create a poor antibiotic with nice side-effects for farming usage (because 'gain weight faster while eating less' sounds like useful magic)... And how come those farmers give the whole spectrum of various antibiotics to their animals - why don't they just settle with the cheapest antibiotic type so that they don't rubbish all of them?

Thanks, John, for your explanations.... But just for you to see how things can get wrong when you are not explicit enough: - "Do you think the antibiotics are being used to stop the animals getting sick and dying?"... my understanding was that you are referring to antibiotic overuse - in a sense that it is unnecessarily given for every little bit, but still for medical reasons. - "Then the meat from those animals enters the human food chain." ... my understanding was that you are concerned that it is antibiotics that could be consumed by humans.

@John Cuthber... Thanks for reminding me about this point (I recall now that I heard about it sometime before)... But I am not sure what is the meaning of those big bold letters you use. In your first post you were not clear about what you are talking about - at least I did not get your point. Also, it is clear that meat from those animals enters the human food chain (that's the whole idea)... but you are again not clear why are you mentioning this.

How I see it, super-bugs are not more advanced than ordinary bugs. This 'super' is a bit of misnomer. Super-bugs are resistant to antibiotics, but this does not mean that they are better fit overall. So super-bugs might never evolve if antibiotics are not widely present. That is why restricting antibiotics should work..... In fact, I suspect that without antibiotics, given looong enough time, super-bugs would eventually perish being 'less fit'. Speaking generally, as I understood it, appeals to decrease antibiotic usage is because overuse: - to a farmer it might be cheaper and quicker to administer wide-spectrum high-dosage antibiotics than to make elaborate and time-consuming medical investigation about the most efficient treatment - because of low price, administering antibiotics can be used as a sort of insurance against much worse outcome for a farmer (on a farm, disease can spread quickly) - medical personnel (veterinarians) built habit of being easy on antibiotics (not sure why - is it from laziness or from pressure asserted on them) Obviously, when you look at it from a perspective of a single farmer or veterinarian, administering generous amounts of antibiotics might be beneficial. However from wider perspective, this is a risky behavior. So, my understanding is that there are no serious appeals to remove antibiotics from farming - just to administer them responsibly. Keeping farm animals healthy is important for human health too, so it would be stupid to remove antibiotics completely.

Telepathy - I hate this. Very unrealistic. Fantasy. Machine civilization - yes, realistic. Only I think they are going to be small. Miniatures. It is very cumbersome to carry our big bodies around. Small brains can also think faster. Non-intelligent aliens - by all means. I bet there are many of them within 25.5ly. Aliens parasitic on humans - I hate this. Time travelers; beings from 'other dimension' - I hate this too. Anthropomorphic aliens - Please no. I had enough (unless, of course, they intentionally changed their bodies to look like humans for some good reason). When I was a kid I was very much interested in various alien forms depicted in SF literature. Read a lot of SF, but still have this feeling that I didn't find something seriously novel. However, I must admit that Lem imagined a truly odd creature in Solaris (this one uses some sort of telepathy, but I liked it anyway). Is there anything stranger than that?

After a glance at pictures... It bothers me that the transformer just looks too small for 2500VA (but it is hard to say because there is not much to be used for scale). I hope I am wrong; because if the transformer is substantially weaker than 2500VA, then there is probably nothing you can do. Hmm... If this is a 'constant voltage transformer' technology then I would expect to see some more substantial capacitors (but I never meet such technology, so again I could be wrong). So it seems to me that this is just a multi-tap transformer and two relays to choose taps.

I am not getting what is suggested by OP - that police is brutal or that there are deeper problems in society?

Phi, after I quickly checked your stated age I had to award +1 to you... for the spirit, of course. I hope I will follow your footsteps (I am only 18+ behind you). Unfortunately, in last few years I find it increasingly difficult to keep up the spirit (LOL - let me know if I should be drinking or smoking anything special )... Okay, okay, just few days ago I read that Mother Terese had problems with her faith, so I suppose I am not doing that bad after all... Okay, to say at least something seriously: I find our western civilization very much unfocused, like if we see no problems to solve. So we look for anything to entertain us. That said, I must go now check latest Kim Kardashian Ass pictures (selfie ones!) ... Phy, after I return I would appreciate to hear your personal opinion - were people equally unfocused 40-45 years ago?

I have seen similar effects on pure resistances in practice, but I must admit that I never knew how much of the observed effect was from the transmission line effects as depicted in my previous post, and how much was from (parasitic) inductance of it (as it would be in the A case). In real life, I suppose, the effects I describe would not be as clear (a step-by-step increase in light intensity would probably be smothered somehow), but still I believe that such oscillatory effects are, in general, real even in the pure-resistance case.

When I say that electron 'knows' something, I mean that it feels a force caused by some locally existing field (created by other charged particles that might exist nearby). An electron can only behave according to its surrounding, it cannot act according to something that is happening very far away. An electron in a wire will start moving as soon as it 'feels' a local electric field - it will not wait until the filed is established across the whole wire loop. ... Stop, Hammer time! If one considers an experiment as described in the OP, one must make distinction between two cases: A) The wide loop - an extreme example would be a circular loop of 2ly circumference. In this case the current will create considerable magnetic field and wires will provide considerable inductance (after all, it is a wire loop). B) The narrow loop where two 1ly long wires run parallel, close to each other. An extreme example would be a coaxial cable. Here we could be able to ignore the inductance and energy loss due to EM radiation. I don't know, but I have a gut feeling that these two cases would behave considerably different. For me, the A case is more complex and I don't even know if its large size makes any qualitative difference in comparison to small wire loops - not sure if the same math can be used (I suppose, yes). Anyway, i am only considering the B1 and B2 cases in the following text. As most know, two parallel (or even coaxial) wires make a transmission line (google 'transmission line'). Basically you need to know that a transmission line has some impedance, some signal propagation speed, and some capacitance (per unit of length). Just look at the transmission line - two long parallel wires make a physically long capacitor.... It also needs to be noted here I am talking about uniform transmission line (if not uniform throughout its length, various nasty reflections would happen that could complicate our life). THE B1 CASE At one side of a very long cable there is a battery and a switch. At the other side, there is a lamp (a resistive load). When we close the switch: - current immediately starts flowing from the battery and starts charging the transmission line (imagine zillions of little capacitors between two wires as they are getting charged one after the other as the voltage disturbance front moves at, say, 0.8c) - the strength of this 'charging' current depends, among else, on the impedance of the transmission line - when the front reaches the lamp, say after 1.25 years, the lamp will turn on The story only ends here if the lamp resistance is equivalent to the transmission line characteristic impedance. If not, there will be reflections: - if lamp resistance is smaller that cable impedance, then the lamp will not generate the full light at first. Reflected front of somewhat decreased voltage will be returned toward battery - when it reaches the battery, after 1.25 years, the battery will sense the decreased voltage and will increase its current to compensate. The front will again travel toward lamp, and after additional 1.25 years the lamp intensity will increase for one more step. The reflections will continue, and lamp will increase its intensity, in smaller and smaller steps every 2.5 years. - if lamp resistance is greater than cable impedance, the lamp will reflect front of somewhat increased voltage (and will start shining more luminous than expected - up to twice as much if it has infinite resistance). After every 2.5 years their luminosity will decrease in smaller and smaller steps toward steady state luminosity. THE B2 CASE Here you can see that the far side of the cable is short circuited. This means 100% reflections (-100% actually, as the reflection is inverted). - when circuit is switched on, the lamp immediately starts to shine. Its luminosity depends on its resistance and transmission line impedance. If the lamp has a low resistance, its shine might be barely visible. - when the disturbance front reaches the far side, a near-zero-volt front gets reflected back to the lamp. When this front reaches the lamp, the battery will detect the voltage drop and will increase its current. Lamp increases its light intensity in accordance. - I suppose, if battery+lamp resistance is not equal to cable impedance then reflections will continue further until system reaches some steady state. That is, again the lamp intensity is readjusted in steps every 2.5 years. I must say that I did not investigate much, and made most above statements directly from my head - so be aware of possible errors.

Let me see if I correctly understand your picture: You say that at first, when the switch is switched on, only the electric field starts spreading from the battery through the wire. This electric field front, you say, is generated by electron re-alignment (not by re-positioning). Only after the electric field is generated in the whole circuit (the electric field closes), electrons start their flow. But such a view, as I see it, breaks the principle of locality. How does an electron here knows the moment the electric field is fully established (that is, when two fronts meet at the far side of the circuit) so that it knows it is time to start flowing?

But how do you think the electric field is created inside the wire if not by repositioning electrons (that is, by current)? It is not that electrons just stand still while electric field is being generated - it is electrons that generate the electric field by positional rearrangement. Current flows through battery as the electric field is being generated. Only if you consider wires without capacitance (zero diameter, I suppose), then there would be no current.

@swansont... are you talking about propagation delay of the oscilloscope measurement signal? The oscilloscope can be placed very close to the switch/battery - wires do not have to go straight. Anyway, about the OP experiment: If the switch switches both wires simultaneously: The current will start flowing immediately through battery (possibly stronger than the steady state current). One wire will start charging, the other one discharging. A 'voltage disturbance' will travel from switch through both wires at great speed. Once one of these 'disturbances' (I am sorry, I don't know better English word) reaches a lamp, the lamp will start lighting. Closer lamps will turn on sooner than farther lamps. If a lamp is very close to any battery pole it will start almost immediately... Note: if the lamp is not exactly in the middle of the circuit, then, at first, the lamp light intensity does not have to be the same as the steady state intensity (if the wire has zero resistance, its intensity might change in two steps). If the switch only switches one wire, while the other wire is permanently connected, then the very much same thing happens - again the 'disturbance' moves away from battery through both wires. (In both cases I am placing the switch very close to the battery) An analogy with a water in a long circular trench helps! However, in real circuit there are effect of EM radiation and inductance that are not taken in account in the above picture. The safest thing is to use a coax cable - then you don't have to worry about EM radiation and inductance.

Not sure why are you saying so. 300ns is nothing that special. We did signal propagation experiments in our classes using pulse generators, oscilloscopes and long coaxial cables. (It was fascinating to see that signal pulse arrived in the same shape as it started - then reflected, inverted or non-inverted, deepening on how the coax was terminated)

This topic is just moving into activism territory... and the OP question was clear: "IF IT WERE the goal..." not "IS IT the goal..." IF IT WERE the goal to regulate the planet temperature, then I too would agree that mirrors are better solution than messing with the atmosphere. It is the other question if it will be technically feasible at the time needed. That said, I don't think that we will ever have opportunity to decide anything important about our planet. I am afraid we will resort to doing what needs to be done because there will be no other choice. 7 billion people is just incapable to think in advance.

Lol... when I started this thread I was thinking that adaptive optics is an expensive replacement for image processing. Now it is obvious to me that adaptive optics is one additional step to obtain even clearer images. However I cannot fully agree with your last sentence... You always have the guide star and it roughly tells you what to do with the image. You will be able to roughly place your 'wandering' photon where it belongs.

@John Cuthber... if what you are saying is true, this would clearly make adaptive optics far superior to image processing. But I am (erroneously?) under impression that optical sensors (CCD) can detect one single photon. If so, it would be possible not-to-miss any information even if you make extremely short expositions (and then make integration in the digital domain)... As a kid I was told that human eye can detect one single photon, but maybe this is only an urban legend.

I can see now how information is lost due to limited resolution. For sure, if a detail is degraded (due to atmospheric distortion, perhaps) to a single pixel, nothing much can be made from it. I can also see now how a long-exposition image can be 'infested' by time-varying distortions so that there is no way to make much use of it. However: A) atmospheric distortions vary quickly in time; so if an image detail is degraded to a pixel, in the next moment it might spread to several pixels. Taking many images of the same object (supposing that the object itself is only changing slowly) and doing some decent image processing should reveal high level of details across the whole picture. So yes, image processing is probably inferior to adaptive optics, but I guess only slightly (regarding money invested)... Is this conclusion valid? B) atmospheric distortions vary quickly, but still at some limited speed. If exposition time is short enough there will be no problem with 'integrated noise'... are there limits on how short expositions can be? (Hmm, maybe digital image processing is so common and used in astronomy that nobody is talking about it any more - and this is why it is never mentioned when I read about telescopes.) ... Wow... Only now I see Sensei's post... it confirms that image processing is already heavily used. So I suppose adaptive optics is edge's edge... Thanks for nice pictures.

Can you explain, I don't get it.

I risk to ask a dumb question... Why is adaptive optics better than image processing? I mean, if you know how to adapt a mirror, then you also know how to process image to obtain the same effect.. or? I also read something about a thing called "speckle imaging" but I am not sure if this is what I am talking about. I am not sure if 'guide stars' (natural or artificial) are used with this speckle imaging.