SkepticLance

To DrDNA The 'law' of cause and effect breaks down at the quantum level. If you fire a photon at a double slit, will it go through left or right? There is no cause and effect answer. There are, instead, answers based on quantum weirdness. Cause and effect is, ultimately, about everyday intuition. I don't know about you, but my everyday intuition does not cope with quantum weirdness. Cause and effect does not apply to all situations at the quantum level.

To iNow "Turtles all the way down?" Are you a Terry Pratchett fan? Anyway, the decay of a nucleus by alpha decay mechanism still appears to be due to quantum randomness. ie. causeless. Similarly, as was mentioned by John, the Casimir Effect is demonstration of vacuum energy. This is pairs of particles popping into existence for no reason at all. ie. Causeless. Those particles, near the horizon of a black hole may attain true reality, and live on (Hawking radiation). Something comes into existence and that has no cause. If you dispute this, you dispute quantum randomness.

To POM As I have pointed out before, the transition will be slow and will take many decades. Sure, oil will peak soon. That simply means that it will go up in price, which will induce industry and individuals to make changes. That is one of the reasons that people will start to buy electric cars. However, the oil will not run out overnight. It will take 30 to 60 years to become uneconomic, and I would think 60 is closer to the truth (because increasing oil prices will stimulate a massive exploration effort). There will also be a big coal to liquid fuels move. Here in NZ we have enough lignite (low grade coal) to supply our vehicles with diesel for hundreds of years, and NZ is by no means unique in this. I mention this because the local newspaper mentioned that a government unit is currently quietly investigating that prospect. I do not agree with coal to liquid fuels, and see it as a backward move. However, I think it is (in the medium term) inevitable. The point is that the move to alternative fuels does not have to occur, as you suggest, in 9 years. It probably has around 50 years, plus or minus a major error factor.

iNow This is science. As a person who likes to think in a scientific way, you will be aware of the fact that each statistic that is derived, no matter what the issue, carries a certain error factor. So when we are speaking statistically, we may say that a measurement is X. What we mean, of course, is that the result is X plus or minus the error factor. This is something you are well aware of. Official statistics show that, over a 20 year period, 35% of all humans deaths by dog attack were caused by Pit Bulls. I accept that there is an error. However, for the statistic to be meaningless, the error must be huge. You have suggested, in effect, that the main cause of this error is misidentification of breed. You have offered no real evidence, just assuming that the official gatherers of data are incompetent when it comes to ascertaining dog breed. Bear in mind that in most cases of fatal dog attack, the dog is rounded up and killed. To fail to know the breed from a defined dog corpse is an unbelievably major lapse of competence. So what is the actual error? I suggested 5 to 10%. The second breed that kills next largest number of people was Rottweiler. At about 20%. Are you suggesting that the officials involved in gathering statistics are so damned incompetent that they allow an error of more than 60%????

To iNow That argument is simply an attempt to evade the statistics. Even if there is an error factor involved in identifying breeds, how much would that error be? 5%. 10% ???? That does not alter the fact that pit bulls are the most dangerous breed.

To POM Not quite a strawman. What you said was : "and if we tried to obtain all our hydrogen from existing freshwater supplies many European rivers would be running dry." OK. This may not have been exactly what you meant, but it is what you said. In fact, there would be no need to desalinate sea water for electrolysis. Works well even with all that salt. Your next statement "exactly where are we going to be driving in these vehicles? They'll rush us silently and cleanly to the next traffic jam." has several answers. For a start, not all cars are used in big cities. Also, proper extra road construction reduces the jams. Finally, new technology already on the drawing board will permit twice as many cars per unit motorway. For example : computer controlled auto-distance to the next car, permitting more cars per 100 metres, and adding to safety with electronic reflexes operating brakes etc. "I WANT a replicator, a matter transmitter, a holodec... hey, let's just say I want a whole Enterprise to myself, as well as eternal youth, prosperity, happiness, and the same for all my friends" Yes, but you don't got them! And these are impossible anyway. Millions of people already have cars, and they know that new technology will permit them to keep cars. They are prepared to pay for them. The laws of economics say they will.

Amazing how dog lovers can ignore any statistic that does not meet with their prejudice. In the USA, pit bulls account for 35% of all fatal attacks on humans. And no, they do NOT constitute 35% of the dog population. There are 74 million dogs in the USA. 35% is 26 million. Do you really think that there are 26 million pit bulls in the USA? http://www.igorilla.com/gorilla/animal/2000/dog_policy_boston.html

To POM As I have said before, and which is pretty obvious from a purely common sense viewpoint, there will not be any one single solution to the problems being discussed. There are probably a thousand research projects under way right now covering some aspect or approach. Most will go the way of the dinosaurs, and a few will survive and become part of 21st Century technology. Electrolysing water to make hydrogen may or may not be a part of the group of technologies that develop. If it fails, it will not be a lack of water that is the cause. After all, there are 1,000,000,000,000,000,000 tonnes of water in the oceans! Electric vehicles definitely should be one of the technologies. In fact, I predict EVs will become important in the very near future - the next few years. Today, many western families have two or more cars. This will continue, and one will be battery operated. Perhaps with a lower top speed and a lower range. But it will be ideal for commuting to work, and for shopping expeditions. It will be cheap to run. I believe that the time has come for the personal EV. One thing I am sure of. The personal motor car will survive in some form or other. Not because it is more sensible or cheaper, or solves society's problems. It will survive because people WANT them.

To DrDNA I have no doubt that some of those men were killed by sharks. What I was talking about was the inevitable exaggerations that follow such incidents. For a start your account talks about it being Tiger Sharks. Sorry guys. Tigers prowl the fringes of coral reefs, and are rare in deep oceanic water. The shark was almost certainly the Oceanic White Tip Shark. This would be the mere beginning of the errors. Those seamen wore kapok life jackets, which are nowhere near as good as modern life jackets. If you are afloat too long, some of the jackets get water logged and can actually drag you down. Your account talks of 5 days drifting - quite long enough for many life jackets to turn lethal. It also talks of the state of mind of dehydrated and exhausted survivors. Their perceptions would be utterly screwed. A person who simply sank would be seen as being a shark attack victim. As for the description of limbs and gore everywhere .... Take that with a VERY BIG pinch of salt. A very well documented aspect of human psychology is the tendency to report dramatic experiences in a more and more exaggerated form as time goes by. The sharks become more numerous, larger, and more fearsome. I can accept that some degree of shark attack would occur, but if you believe that superstitious seamen in that environment would not allow their imaginations to take over and ascribe every drowning to shark attack, then you are naive. If you saw the Blue Planet series (BBC) on TV, you would have seen the results of a serious attack. That was on a bait ball of fish. By the end, no smal fish survived. That was an attack by different kinds of predators, but a massed shark attack on seamen would be no different if it was a genuine major attack. Oceanic White Tips can sense prey across a wide area, and an attack of the sort you describe would attract every shark within several hundred kilometres. I am talking hundreds of sharks. With 5 days before rescue, there would be no survivors.

To DrDNA We get a lot of stories of the sort you mentioned. It is often difficult to separate truth from fiction, since the survivors of such disasters are frequently in shock, and have their stories unclear. It is very common for drownings to be ascribed to shark attack. On the other hand, the shark that comes to such sites is the Oceanic White Tip. It is the only shark that has ever acted aggressively towards me. I have twice been charged by this species - both times when I have been in deep tropical water. Both times the charge was ended by the shark stopping abruptly, turning and fleeing for the horizon. Thus, it is possible that some human deaths have occurred due to attack by this shark. Trying to quantify it is pretty much impossible, since truth and exaggeration are impossible to disentangle. If these sharks were truly serious about those attacks, there would have been no survivors at all from the Indianapolis. In the deep ocean, the shark is the master, and humans are helpless.

To DH You are correct with your equation for acceleration. I should not have used that term. The kinetic energy equation is KE = m.v.v That is, velocity squared. Since kinetic energy increases are equal for both rocket and ejected reaction mass (Newtons third law), the increase in that of the rocket is proportional to the velocity of the ejected mass squared. In this case, kinetic energy can be equated to thrust. If you take an ion drive, and double the speed of the ejected ions, while keeping the mass ejected constant, the thrust will quadruple.

Thank you, swansont, for the clarification.

To Mr Skeptic Acceleration of a rocket (assuming no friction and microgravity) is proportional to the mass of the ejected mass times its velocity squared.

To Mr Skeptic There have been a number of occasions where a shark has bit a human, releasing vast amounts of blood, sometimes enough to kill the person. Yet they do not press home the attack. I doubt their senses are insufficient to sense the blood. Much more likely in my opinion that they identify from the smell that the animal they bit is not part of their normal list of prey, and hence might be toxic. Of course, when you read the accounts of people who survive such attacks, you get a very different account. "The shark stopped attacking because I hit it hard." "I gouged its eyes." etc. etc. etc." Yeah Riiiiight! Shark attack survivors delude themselves that their survival has something to do with their own actions. Where it all happens is in the sea, and the shark is master. if they allow a human to survive, it is because they choose not to press home an attack. Why?

Captain Panic described the basic mechanism very well. I will just make one addition, but which has many consequences. The power of a rocket depends on both the mass of the gas it is firing out, and on the speed that the gas is ejected. You can make a rocket more powerful by having more mass to throw away. You can see this principle in action with the space shuttle when you look at the massive fuel tank that is strapped on. In fact, the mass of the fuel to be ejected far outstrips the mass of the shuttle. However, it is actually more efficient to increase the power by ejecting the fuel at a faster speed. It is an exponential function. Increasing mass is merely linear. That means if you double the mass of the fuel you eject, you double the force. However, if you double the speed at which the fuel is ejected, you increase the force by four times. Triple the speed of ejection, and you get nine times the force. Simple chemical rockets, such as used in the shuttle, have limits of speed of ejection. However, an ion drive uses an accelerator to speed up the fuel going out the back. This makes it really efficient by comparison. Ion drives are not much chop when leaving the Earth, but are great when out in space heading for Mars. A small amount of fuel gives a lot of force to accelerate, and later slow down a space probe.

To the capn. Nice theory, but I doubt it. I have been with sharks that are being fed by dive tourist operators. Whenever these guys go down with a bucket of fish scraps, the sharks are VERY hungry. I counted the species of sharks I have encountered on scuba dives, and got to 18 from memory. I have encountered many of each species. Unless they are being fed, they tend to keep their distance. Some swim in to within about 10 metres of so, apparently out of curiosity, but most like to keep well away from a scuba diver. Out of all the hundreds of sharks I have seen, only twice have I seen aggressive behaviour. Both times it was from an Oceanic White Tip Shark, in very deep water. Even the one time I saw a White Pointer (Jaws) shark, it showed only curiosity. I have dived with Bull Sharks - sometimes said to be the deadliest - and cannot get close enough to take a photo. I always end up chasing them away.

As a mad keen scuba diver, I have always been fascinated by sharks. One aspect of the human/shark encounter that has been very apparent is the extreme rarity of shark attacks. In spite of literally millions of humans swimming in many places in different parts of the world every day, and the fact that sharks must swim nearby and perceive these human swimmers with their very acute senses, only about 4 fatal shark attacks happen each year globally. Of course, there are many more attacks than that - most are non lethal. Almost never is the attack followed up by the shark actually eating the human victim. I have always thought that the real puzzle is not why sharks attack (they are top predators after all) but why the attacks are so rare. This is especially puzzling in comparison with land predators. A lion or tiger will readily attack, kill and eat a human. Not only that, but the pattern appears to be the same with other large marine predators. Near where I live is a woman scientist who has devoted her life to studying Orca. Along with sperm whales, they are the top marine predators. The woman I mentioned has found that each population of Orca have a very limited diet. Here in NZ, it is mostly sharks and rays, with the occasional seal and dolphin. She swims with them regularly and has never experienced the least interest from them of a gastronomic nature! I have formulated a theory, which I would invite comment on. The theory is based on the fact that the sea (as opposed to the land) contains a large range of organisms, and especially fish, that are toxic. Marine predators must quickly learn not to eat just anything, as it may result in seriously nasty symptoms. They settle for a limited range of target organisms. It is as though they swim around with a shopping list in their brains, and eat just what is on the list. So why are people attacked at all? For unprovoked attacks, I suggest that it is for two possible reasons. 1. A shark uses its mouth as people use hands - to investigate the environment. If a curious big shark mouths a human, it is likely to leave nasty - even fatal - wounds. 2. Mistaken identity. A swimmer's hands or feet may flash in the water like a target fish species, and the shark snaps on it by reflex. Sometimes hard enough to amputate. Yet documented cases of people actually being eaten are almost unknown. Any comments?

I recall what happened here in NZ, and I assume something similar occurred in other countries. We had an organisation (DSIR) which had a number of divisions carrying out scientific research. Money was dispensed to those divisions by government according to the perceived importance of the division, and supported a wide range of research. Then the government changed the structure. Today, the DSIR no longer exists -replaced by Crown Research Institutes. Within these, any scientist wanting research funds must make a presentation to the appropriate government stooges, who will award money according to what they see as being in the national interest. These are career politicians and bureaucrats who have no feel for the value of pure research. The result has been a whole bunch of scientists who waste a big chunk of their time in the politics of begging for money, and who are constrained within tight boundaries when doing their research. I would imagine that Brabens ideas would be seriously attractive to them. What is it like in your corner of the world?

Someone correct me if I am wrong. As I understand it, the decay of a single nucleus is essentially causeless, and can be assigned a probability. eg. The chance of it decaying over the next million years is 50%. Otherwise known as the half life. I am not a nuclear physicist and my understanding may be wrong. However, I have always imagined the decay of a single nucleus as a form of quantum tunnelling, based on (say) a neutron. There is a small but finite probability, due to quantum uncertainty, that the neutron will find itself outside the zone in which the strong nuclear force holds it in. As and when that happens, said neutron wanders off on its merry way. And the nucleus falls apart due to the loss of the neutron. When we look at enough such nuclei, and apply probability and statistics, we can say that a certain fraction of those nuclei will suffer this fate in a particular time. Since the basic reason for the decay is quantum uncertainty, then effectively there is no specific cause. Am I wrong?

To swansont and phi for all Ok I was careless in my wording. It is not teenage pregnancy alone that destroys a girls life. It is that pregrancy combined with a lack of a husband or equivalent. Remember that in primitive societies, a pregnant woman and a woman with a young baby or toddler are very vulnerable in terms of getting a living, unless they have a husband to assist. Phi for all talks about a girl becoming a 'slut' and the lousy reputation that accompanies the title. There has to be a reason for that lousy rep. Similarly swansont with his virgins. Why is virginity seen as desirable? Again, there has to be a reason. My idea is that the girl's reputation is related to her loyalty to her husband to be. If she is a 'slut' or has lost her virginity, it is an indication that she may not be sexually faithful when married. There is a serious reason for male sexual jealousy with strong evolutionary pressure. That is : women who are married or the equivalent of marriage do, in fact, play around sexually occasionally - but only some women. Any man who ends up married to such a woman may, without knowing it, raise another man's child as his own. That is counter-adaptive in the evolutionary sense. It is avoiding this situation that makes a man wary of marrying a girl who has shown sexual interest in other men.

To ecoli Attitudes to sex are deeply placed in the human psyche. Parents have been afraid of their children having sex for a long, long time. It is even possible that the fear may be genetically encoded. It is certainly well encoded within cultures. The reason is simple enough. Contraception is recent, and until that happened, teenage sex resulted in pregnacies, which would totally destroy the life of the young woman involved, and in primitive societies result in actual death rather frequently. It may be that the fear is no longer valid (as long as the kids have condoms), but it takes a long time to change behaviours that are well engrained in a culture.

To CDarwin Nobel prize winners don't need a sinecure. The value of the prize is enough to retire on, and the reknown enough to make sure you get lots of opportunities to make money easily, such as on lecture circuits. Your point about age is valid, though. Perhaps the Nobel winners should be required to choose younger scientists that they consider exceptional? They become head hunters.

To severian I think your bank robber analogy is wrong. A condom is a preventative - not an equivalent to a gun. A better analogy is giving bank tellers bullet proof jackets. Would that increase the incidence of bank robberies? I think not.

Atheist: Prof. Braben is a physics professor. Just to quote a paragraph from his article. " The key to scientific and technological productivity is to give creativity full rein. The academic research that spawned almost all the major advances of the 20th century, and which in turn fuelled spectacular global economic growth, was largely unmanaged. Yet in the 1970's, things changed. Since then, scientists have had to aim their funding proposals at specific objectives. Peer review, seen as fundamental to scientific progress by too many researchers, has removed all spontaneity from the process of generating ideas. Such policies have led to a glittering profusion of new technologies, but most of them stem from major discoveries made decades ago. We are living on seed corn." To CDarwin Braben's Plank Club was to be made up of Nobel prize winners or their equivalent. The best of the best in science. Do you think you are one of them? With the greatest of respect, I doubt it. I recall, several decades back, in the Soviet Union, there was to be set up a science town. A place where scientists could live and work together, with all the supports in place to give them a living and get the resources needed for scientific progress. I do not recall it actually happening. Anyone know more about that? I know this is never going to happen. But I would like to see the equivalent set up today. Imagine a number of top scientists, such as Nobel prize winners, offered the chance to go to such a town and carry out research on whatever project they see as most important. Each would have the chance to offer a similar position to, say, five other top scientists to work with them. The town would provide all the services, and all the technician support they needed. Resources would be made available by a team of specialists whose job would be simply to remove barriers to performance by the scientists. I know it would never happen, even though the USA, Russia, China, and the EEC all have the resources to do it. But if it did happen, what discoveries might be made?

Prof Braben suggested that the major discoveries of science were all made by the 1970's and since then we have been essentially filling in details. His view is that academic freedom for top scientists may lead to new discoveries of critical importance. I suspect this is an over-simplification, but maybe someone else has a slant on this. Reminds me of the 'skunk camp' which was a characteristic of McDonnell Douglas in their designing of jet war aircraft. They set up their top designers as a team - the skunk camp - with essentially no restrictions - just a task. Gave them all the resources they needed, and removed any bureaucratic barriers to success. Apparently the system worked very well. Incidentally, the name 'skunk camp' was bestowed by some of the bureaucrats who were disgusted by their freedom. Suggested that the method stank! Could a 'skunk camp' of top scientists lead to new and vital discoveries?