TonyMcC

I use my computer for all the usual things (Email, Bank, Poker, Family History etc.). I like this forum and so whenever I use my computer I have a quick look to see if anything interesting to me has appeared. I am disappointed when due to timing there are only a very few items displayed. I think it would be a good idea to always display a set number of the latest entries - even if that sometimes gives more than a day's ideas and anwers. I suggest always displaying the latest 30 entries. Do you think this is a good idea?

Can I suggest the question would have been clearer if the units were given for resistivity. For instance resistivity of copper is approx 1.7 micro ohms -cm or 17 nano ohms-m.

Ah, but this is an exceptional circuit. One terminal of a battery is connected to the inside of the sphere without needing a hole. The other terminal is connected to the outside of the sphere which is coated with magical material which has no resistance. This will provide the radial current! On a more serious note I am sure this must just be an exersise in integration.

pioneer - I suppose what I am saying is that if you roll a die and it lands on one of its faces the only thing you can be sure of is that you will get a number between 1 and 6. What you are saying is if you know the die's starting point together with all other details such as number of shakes, force of roll, air resistance, smoothness of the landing surface etc. etc. you would be able to forcast the number obtained. I can't argue with that. However, when you think about the number of variables concerned in evolution the mind boggles at the thought of prediction. For example a new species might get its start from a cosmic ray that might alter the DNA of a female egg. I suppose you would have to predict the effect that would be the inevitable consequence for each part(s) of the DNA that might be changed. In order to make that prediction you would need to know about the ever changing environment the new being would be born into. How it would be cared for and that iit would definitely reproduce. You would have to predict right at the start that the number of offspring would be definitely going to have enough influence on the environment to generate a new species. Although what you say is undeniable I think the odds against are so huge that inspection of the DNA of a fertilised egg will only take you a little way along the path to prediction.

I very happy with Darwin in the middle. In fact I suspect that the people presently developing an understanding of evolution will in their turn find themselves "in the middle". Because of the random nature of evolution (random tries with rare successes) I find it hard to believe that solid predictions will ever be possible.

On reflection I have probably read too much into a comment by D H "In a sense, who cares what Darwin said", especially as he completes his sentence with "Darwin was the start, not the pinnacle, of modern biology". In mitigation I would say that this was a response to my understanding of the phrase "Survival of the fittest". At the time I thought I was being informed that my interpretation was either completely wrong or irrelevant. Sorry D H if I have slighted you.

Out of interest I have been reading up a bit on this subject. Wherever I have looked so far I get the impression that the likes of Darwin and Wallace are not believed to have been incorrect in their ideas. The general opinion seems to be that their ideas were not complete and modifications were needed to explain more completely the paths of evolution. The same IMO could be said of the likes of Newton and even Einstein concerning their theories. what puzzles me is why the likes of Newton and Einstein are revered whereas poor old Darwin is ridiculed and despised by so many people.

Sorry - this exchage must be frustrating for you, but surely at the instant the river seperated the population both resulting populations were essentially the same. Perhaps you are saying that since all individuals have a unique DNA pattern, and since at the time of division some individuals would have carried mutated genes, the gene pool of each population is different? Perhaps that gives a different starting potential for each population? I can quite see that if the clock is wound back 600 million years and restarted then due to the random nature of mutations the life content of the world today would be very different. This obviously is a topic which I find interesting but have only a laymans knowledge - thank you for your patience.

I think I understand what you are saying. If the population is unchanged but split in the way you are describing then presumably the two halves (we shall assume split equally) will continue to evolve and in doing so eventually give rise to 2 seperate species. In their two separate territories they will have the same difficulties in surviving - finding nourishment and dodging predators etc.. Thus the trigger point for the arising of these two species was sudden. After the split gradual mutation will again have its place in the development of each species. Some of these mutations will be beneficial and aid survival although most will be detrimental. I hate to put it this way but surely it is true to say some of the mutations will make the mutated individuals "more fit" for survival and most will make mutated individuals "less fit". I don't think you disagree with this - I believe you wanted me to understand that gradual evolution via natural selection was not the only evolutionary pathway. If that was your aim then you have succeeded and I thank you. Although not as sudden and total a start as you have described Darwin's finches show seperate evolution after seperation from the original species.

Would you not say that punctuated equilibrium may well be a possible cause for an abrupt evolutionary change of a species but if that changed species cannot flourish in the environment it finds itself it will probably not succeed? i.e. it must "fit" its environment?

D H - I can't work out whether we are agreeing with each other or arguing some point. I guess you are letting me know that as well as gradualism, evolution can be caused by other means such as punctuated equilibrium. Since both seem probable and since it applies to both scenarios (and any other that I can imagine) it seems to me that explaining the phrase "survival of the fittest" is relevant. If it is relevant then giving credit to the man generally believed to have expressed it seems fair even if at that early stage he did not have the whole picture.

D H - Don't disagree - Birds of Paradise are an example of what you say. But where there are predators survival depends on being able to evade them until offspring can be produced. If a mutation aids that then an advantage is gained. Obviously where life is "easy" being more able to attract a mate becomes an advantage. Evolution is really a "trial and error" situation with, I think, many more failures than sucesses. It certainly is inefficient without planned intelligence of any kind. I do believe Darwin used the word "fittest" in the way I describe?

It's down to what is known as "survival of the fittest". Fittest in this sense means what fits the environment best - not fittest meaning most healthy or strongest. If a mutation gives an advantage for an organism within its environment it has a better chance of survival and reproduction thus passing on the mutation to some of its ofspring. The mutation can be small and yet give a real advantage. A sucesson of mutations can, given enough time, produce something as complicated as the eye. All stages of eye devopment can be seen in some sea creatures. The most basic being light sensitive tissue that just warns of movement. In the land of the blind the one eyed man is king!

Zapatos- Actually I believe you are making reference to an earlier comment of mine. What I actually said was "At the moment of conception the fertilised egg contained all the information.....". In other words in your analogy it would be once the oven had been switched on, not just before it is switched on. I feel that "just before the oven is switched on" there are probably a million or so recipes waiting to have a chance of life. However once one of the "recipes" gets under way the "cake" is forming in response to that particular recipe. All the other "recipes" are discarded.

I know swansont - you'll have to forgive me. I studied a bit of calculus 50 or so years ago. I am now retired and during my lifetimes work I never had recourse to use it - to say I am rusty would be an understatement! However I did wonder if my basic description of what calculus did in this instance would be of some use to anyone struggling with the concept.

You guys seem to have cracked it using calculus. I'm sure that must have been the objective of the questioner because of the impossible situation described. For a practical crack at the problem which would give a good approximation you could do the following:- (This is no doubt what your calculus does more accurately). Consider the sphere as having several layers, like an onion. For each layer calculate a resistance, using the average of outer area and inner area(approximation). If you considered 50 layers you would have 50 resistances. Think whether you should consider these resistances as in series or in parallel and make your simple calculation. I suppose this sphere is coated in some magical material which has no resistance in order to make radial current flow?

I'm wondering how you get connections to both the inside and outside without making a hole in the hollow sphere. This hole will reduce the amount of copper used and its size and shape will have a small bearing on your answer (assuming the hole is small).

I think that once you put the mixed ingredients for your cake in the oven and switch the oven on you are entitled to anticipate eating your cake (have to lol although this is a serious topic)!

AzurePhoenix - Has panspermia been defintely been ruled not viable and so not responsible for life on earth? I only introduced it as possible link between life on this planet and any life to be found elsewhere in the galaxy. I believe the odds have been calculated at 10^24 against panspermia but that is a bit short of infinity!

I suppose what you are saying is, Mr Skeptic, if we go back far enough we will find all animal life on this planet is related. More than that, it is at least possible that if we go back even further than that all life on this planet is related whether animal or vegetable. It may be possible that if life is found anywhere else in this galaxy we will find we are related to that life form. Apparently the "building blocks" of life have been found within meteorites. Some of these meteorites being possibly older than the solar system. I don't disagree with any of that. I just feel I am a unique specimen of life and my uniqueness stems from the moment of my conception. That is where life started for me. Whether one considers that a fact or just an emotional illogical response I leave for others to decide!

I guess this is a topic that many people have differing views about: All of them valid in one way or another. As for me, I am content to feel that I, as a unique human being, came into existence at the moment of conception. Given nourishment and protection throughout my developing years all that I had the possibility of becoming was decided (almost entirely by chance) at that time. If I had been born with a brain limited in ability such that it could keep my body alive but nothing more I would still be a live human being.

I don't really disagree with what Sisyphus says but I am uneasy about one statement. Before the moment of conception there is enough information to make hundreds, perhaps thousands, of different individuals. After conception there is normally only the start of one particular individual. I sometimes think how fortunate for me that the person I know as me was brought into existence. As a simple example if my mother's egg has been fertilised with a different sperm from my father I (or rather the different person born) might have been a female person instead of male. The information concerning the other possible hundreds or thousands of individuals is lost.

I thought the question was "When does life begin" which is quite different to "When can you be considered a human being"?

At the moment of conception the fertilised egg already contains the information about the fully formed person that will develop. Its sex, hair colour, height etc. All this fertlised egg needs from then on is nourishment and protection. Every milestone along the way is just another step in its devlopment. It seems illogical to me to chose some point after conception as a starting point for human existence. Whatever point you chose will, at the least, be debatable.

You could use a multimeter reading d.c. current instead of the bulb. set to a scale which would be too high and increase the sensitivity of the meter until you get a reading. This would provide more information about what is going wrong (if anything).