Hello Terry,
No, I had not supplied a diagram, partly because there would be very little in it. All it would show would be two observers at a time approaching each other at a given speed (or two different speeds) relative to the air through which they were passing. Two, or possibly three, arrows labelled with numbers and pointing generally in opposite directions. It hardly struck me as worth inclusion!
I recommend that you begin by drawing opposing arrows some distance apart and pointing at each other. Label each of them 0.5M, you might like to put in a double headed arrow labelled 1M to show the speed at which they were approaching each other. Now draw (or imagine) a line from one arrow to the other, representing the path of a sound wave. The source of the sound is travelling at only 0.5M remember, so the sound gains on it quite handily in fact also by 0.5 M, and gaining a considerable Doppler effect from the point of view of any stationary or indeed oncoming observer in front. In any case, it will reach the oncoming observer well before they meet. What is more, if the oncoming observer is carrying a convenient reflector, it will then reverse its path, incidentally intensifying the Doppler effect, and travel back to its (by now much closer) source before the two participants meet. It is clear I hope, if you look at it in such terms, that auditory communication between two such travellers is in principle possible. Note: I said nothing about practical communication!
Very well, if you have followed me so far. Now try similar exercises with the other speeds that I mentioned. In particular suppose that one bat is travelling at Mach 1 and the other perching stationary. If we were speaking in terms of light in vacuum this would not be substantially different from the earlier example, but for sound in air things are different. If the flying bat shouted, the message would not be separate from the sonic boom, whereas if the stationary one shouted, the message would indeed reach the approaching speed maniac.
Have I dented the visualisation problem? If not, feel welcome to ask again for elaboration.
>I am reading from the above that for example :if the train is coming towards me the pitch of its whistle remains the same whether I move toward it or stay still. i.e. I do not compound the Doppler effect by moving toward the train.<
I am not sure what I said to give you this impression. There would be a most decided Doppler response to any change in velocity affecting the rate of mutual approach or departure. In fact in one example I gave in this instalment, you will have seen the Doppler effect, not merely in approaching, but also in reflecting the sound. It might help you to imagine the Doppler effect in terms of changes in frequency such as one would find in approaching or retreating from ripples on the surface of smooth water. The Doppler effect is exactly analogous to the change in the number of ripples that you pass in any given second.
>I have actually experienced the "holiday driver "example when I attended an air show. The mirage jets of the time approached from the rear and I had hardly recognized the silent jet that appeared in my vision before the sound wave frightened the life from me.<
To my no doubt warped mind, there is something unspeakably beautiful about the ghostly silence in which modern jets can manoeuvre, complicatedly and impressively, only to express their appalling power in the blast of the sound when it reaches you. It recalls Wilfred Owen's "Only the monstrous anger of the guns..." but without the tragedy.
>But back to the crux of what I was attempting to suggest by the question; If we (the bat community) had no facility to experience electromagnetic sensation then we would measure everything by sound wave reflection .We could have our bat Newton and we could envisage super heavy objects.(Electromagnetic waves are only entertained by the loony taro card mob)<
But Terry, we (the human community) have no physiological ability to experience say, radio waves any more than bats do, and yet it did not change the way things worked when Maxwell deduced and Herz demonstrated their existence and nature. How we measure things is not directly limited by how we perceive those things. As soon as the loony Tarot card mob begin to make material predictions that sceptics can verify and control for themselves, then it does not matter what we or the sceptics can personally perceive, only what we can demonstrate physically and logically. And in particular, when the demonstrations work independently of the experimenter.
How has your cell phone been working lately, or if you are above such mundane modern toys, the cell phones of your less worthy acquaintances?
>Unfortunately mathematicians in studying, what could happen when an object accelerated under the force of gravity towards a massively heavy dense object, ran into problems with infinities!As the velocity increased toward the velocity of sound calculations showed that A body would be stretched towards infinite length and density!?<
You would appear to have been frequenting the haunts of mathematicians other than those who move in my circles. My own pet mathematicians do not speak of bodies being stretched to infinite anything, only being torn apart by tidal forces. Length was limited, and density was hardly relevant. And when that happened it had nothing to do with the velocity of the body as such, but the greater acceleration experienced by those parts of the body deepest in the gravitational well. The only infinities involved were beyond the event horizon. Better have a stern word with those mathematicians of yours!
>What I am attempting to illustrate Jon ,is that we are no more able to declare that there is nothing outside the electro magnetic experience than our bat community could suggest there was nothing outside the sound experience.<
Well now, that is not quite the same thing. In the case of the bats, you and I are in the fortunate position of being able to see all kinds of practical reasons why they do not live in a world in which the speed of sound has much fundamental philosophical significance. The question of how much of a similar dilemma we face in making sense of our own perceptions of the world is a very different question indeed!
It certainly is a very important question. Late 19th century scientists (some of them anyway) were pretty dismissive about the future of science. Those who knew it all (basically the physicists) reckoned that from then on it would be a tedious matter of eyeing the crocks and treeing the brocks or something. And then some silly upstarts with ludicrous names like Heisenberg and Einstein queered the pitch no end. Now, I am not one of those who insists that there never will be an end to our discovery of new fundamentals. For all I can tell we may yet be on the brink of discovering GUTs and TOEs. However, I was deeply sceptical when in the 80s and 90s, some big name physicists (can't remember who, maybe their names were not so memorable after all) began to echo the chorus of their predecessors of a century ago. Without the slightest theoretical or practical support, I remain equally sceptical today, but with increasing rather than decreasing confidence.
Apart from everyday practicalities, there is a strong philosophical basis for claiming that, even if we do achieve working GUTs and TOEs, we never can prove that our theories, no matter how successful, are ultimately correct. The first thing to recognise is the fundamental nature of science. To begin with, it is necessary to see naïve Popperism in a healthy perspective, a perspective that includes not-so-naïve induction in its own proper perspective. Falsification, as a mantra, is no better than Om mani padme hum, and a good deal less restful. The only philosophically viable basis for science that I have seen so far is to compare the predictive success of formulations of rival hypotheses concerning objects under study, and select the strongest current candidate in the light of available evidence and logic. At all stages, before, during, and after, it is open to all practitioners to accept, reject, doubt, or reserve judgement. Proof, absolute proof, never happens. For one thing, there is always the possibility of a mistake; it has happened time and again and in many forms in every discipline. People prate of "consensus", but the louder they shout the more obsessively I count my spoons. I do not reject the opinions of the mainstream on principle, but several times I have been revoltingly smug about having reserved judgement. There comes a time when it is unreasonable to persist in rejecting what is hard to understand and hard to believe, and some say that "scientific proof" amounts to achieving that state for any particular theory. But that is not a formal proof. It is a practical expedient. Practical expedients are not to be belittled, and I do not belittle them, but neither are they to be seen as sacred objects to be protected from profanation by the holy anger of the theocracy.
For one thing, we never can prove that we have identified all relevant hypotheses. We cannot even prove that the set that we have identified includes the correct one or even that it includes anything meaningful in terms of "reality".
>Calculations for us with sound are observed through a field of a higher order and consequently we can do all our calculations without a problem with infinities. Bats cannot.<
What infinities do you see as troubling any Chiropteran mathematician in particular?
Go well
Jon
