studiot

Which is what I said if you read my post properly. However that does not mean that reflections will not cause standing waves. Yes they will die away exponentially but you claimed an absolute - that they will not exist. Perhaps more cooperation and less confrontation will lead to a more informative thread?

Well obviously the university I went to counts differently from yourself. I learned, in rather quaint terms, that the whole point of of Newtons first law is that it is qualitative, not quantitative. So there is no doubt as to what I am referring I mean, in modern parlance, "A body will continue in its state of motion or rest unless acted upon by a force" go well

So?

Thank you for your thoughts. I take it that you have read the whole thread (it is not very long) and can therefore find answers to the above in my previous responses. I am particularly proud of the fact that many have contributed to this thread and that it has not descended into the all-to-common ya-boo squabble.

Unless the transient is 100% absorbed at the end of a DC line there will certainly be standing waves due to impedance mismatch induced reflections. Depending whether we accept our copper wire to have zero or actual resistance such standing waves will not or will gradually die away.

There is another effect in play at the distances considered. Even 'across a continent' the distances are only of the same order as the wavelength (approx 5,000 km for 50/60 Hz) of powerline frequencies. So the transmission of disturbances such as switching on or off is between a single pair of nodes and continuous and the velocity of transmission is close c, since the transmitting wave is largely surface. If it were not for the skin effect and the electricity actually travelled through the copper wire it would slow dramatically. Powerline frequencies have a velocity of 300,000,000 m/s in air (skin effect velocity) and 3 m/s in pure copper. However at 900,000 km there will be a significant number of complete standing waves.

@Eugene Morrow. I am sorry you chose to merely repeat your spiel about keeping it simple, rather than actually reply to my point. The second time round it becomes condescending and patronising. I see from your profile you studied maths at university. I too have a degree in (applied) maths, along with other technical qualifications, including postgrad level. So please pitch your replies accordingly.

Strictly speaking I don't see that the observable fact of living fish demonstrates there is or is not gas dissolved in water. You need other evidence or knowledge, from biology, to make that deduction. You can, of course, design a series of experiments to prove that fish need oxygen and will die when the dissolved supply is exhausted. Incidentally there is a quantity in environmental science called the 'biological oxygen demand' (BOD) which is used in conjunction with a dissolved oxygen meter to measure water quality.

Good morning, Bignose, I do believe a gentleman called Newton accepted your challenge in sixteen forty something when he enunciated what we now call his first law. go well

I think it is interesting at this point to compare other technical uses of the word evolution. (the original use) In nautical terms it refers to the process whereby a sailing ship starts with bare masts and ends up wiht all sails set. ie running through the full range of a process from start to finish. In mathematical terms it refers to the raising to a power. In chemistry terms it refers to the production of a gas during a reaction. In many other disciplines it refers to development/consolidation eg astrogeoscience "the evolution of the solar system".

Not quite sure I understood this sentence, but yes we can agree It's complicated. As a matter of interest to DH, I was thinking of humans, not finches when I asked about coexistance. White people and black people for instance, though I am not sure who evolved from whom, or whether there was 'parallel evolution' or what.

Good morrow, Eugene (pun intended). I do not want to seem ungracious about the considerable length of your reply to my question, but it was pitched at far too simplistic a level. However I have found a copy of Little's paper and have been reading it for myself. I note he refers to the exact question I asked Whilst there is some mathematics in the paper it disintegrates into mysticism at the point of my question One issue is the continues reliance on the mathematics of continuous functions, when it is far from proven that the real world is continuous not granular. another is the fact that all our equations are models that bump into discontinuities somewhere and often fail to descibe conditions on the other side of the discontinuity. I note that Bignose has already asked for an explanation of why you think qm requires waves travelling in any direction. I too had always understood the analogy in terms of standing waves.

I don't have a problem, but I'm glad I stimulated discussion because the discussion has brought out many interesting aspects, and made several think seriously rather than just quibbling. Thank you for your analogy, quite interesting as well as the concept of process rather than event. The bottom line is that good definitions are a pre-requisite for good communication, no matter how difficult that may be. Otherwise discussion so often ends up as a squabble over definition and the meat gets lost in process. I started out with an unclear and wooly idea of biological evolution and have learned a good deal from this thread. Thanks to all those who contributed.

So are we going to add take over or displace as condition 7 or not ?

So you wish to place the restriction that the former population must die out for the change to be considered evolution. Why can both the old and new not coexist?

Which begs the question of 'take over' ?

Thank you for confirming my analysis thus far.

Thank you for your input, it has different material from that of others. So far I have heard the ideas that (not all yours) 1)A change must be involved. 2)The change must be genetically transmissible. 3)There is a minimum acceptable % of the population that change, regardless? of whether it is permanent. 4)The change must take place over some(undefined) timescale. 5)It is generally argued that the pre change and post change entity must be 'alive' 6) No restriction has so far been placed on the agent (stimulus) of change.

OK so I have two identical petri dishes, containing identical samples of Staph A, with identical evolutionary histories, ie they have both evolved from non methicillin resistant to methicillin resistant. How long do I have to wait before destroying the second one, to say that it too has evolved? A millisecond, an hour, a day, a year?

Why on earth should I be ignoring you, you are doing your best to offer discussion, for which I thank you. I very clearly acknowledged your post#4, repeating your phraseology for just that reason. However nowhere in this thread did I refer to pre-life. The example I gave refers to some very much alive organisms. The phrase I borrowed was from Bignose in his thread about advances by 'unknowns', nothing to do with a recent thread about the speed of evolution, which I admit prompted this current thread. Every science, including biology, needs to have logically consistent definitions. I am simply trying to examine (collectively if others will cooperate) the logical implications of what has been said about the definition, coupled with my own research. Everyone is welcome to offer their own material.

No I'm trying to nail down the definition of biological evolution, to borrow a phrase from another thread. Here is an example of what I mean. Suppose I have 50 dishes of culture of palin old fashioned staphylococcus aureus and I 'tease' them with doses of methicillin. After a time at least two of the dishes will have developed the strain MRSA that now creates havoc in our hospitals. In dish #1 I allow successive generations of MRSA to develop. I treat dish#2 with a flame thrower so ther are no successive generations. Do I count both dishes as having evolved, even if I subsequently wipe one out? Or do I say that only in the dish I allowed to continue has the Staph Areus evolved?

Actually I didn't say there was no change. I said that there was change in both (in perhaps the same timescale - is timescale necessary or is this another extraneous variable?).

Is physically passing on the evolved characteristic to a subsequent generation necessary for the change to be classified as evolution? Or is just the appearance of the change itself enough? An does this term only aplly to the first time the change occurs or can it also apply to any instance of this change? For instance if I take two petri dishes of culture and allow (stimulate) identical (evolutionary ?) changes in each and prove that they are transmitted to the next generation by allowing this to happen in one dish, but prevent transmission in the second by killing all the culture or otherwise. Do both instances qualify as being called an evolutionary change?

Swansont only does this to increase his green score. I understand the owners had to apply for more server space to accomodate it.

Mike, One last try to explain. I have drawn three figures of a frictionless block attached to a rope. In Elevation 1 the block is pulled along a horizontal ice surface at a steady speed by the rope so there is no friction. What forces would you say are acting on the block ? I say that the downward weight of the block is balanced by the upward reaction of the ice and that there is zero tension in the rope and that no other forces are acting. ************** In Elevation2 the block is now being accelerated by the pull in the rope but everything else is as before. Again what forces would you say are acting on the block ? I say that the downward weight of the block is still balanced by the upward reaction of the ice. However there is now a tension in the rope causing the acceleration and that no other forces are acting. Would you say there is any other force in this situation? ************************** Now in Plan 3 the block is being swung around by the rope, still on the ice. Note that fig3 is a plan view. So I say that the downward weight of the block is still balanced by the upward reaction of the ice. I have shown the situation where we believe that there is a centripetal tension in the rope pulling on the block, balanced by a centrifugal force, acting outwards on the block. If this is true the the resultant of the centripetal force and the centrifugal force is zero. Since the resultant is zero why does the block whirl in circle and not continue in a straight line?