Everything that you state would be true if we were looking at Maxwell’s theory of Electromagnetic radiation as being the accepted modern theory for the propagation of electromagnetic radiation. It is not and the reason that it is not is complicated. It is so complicated that in order to fulfill all of the criteria required by what we know today of the properties of EMR, processes like normalisation, renormalisation and quantization and re-quantization are necessary. Some of the most gifted mathematicians involved with trying to solve this problem such as Dirac, opted out of it because the process involved many subterfuges. He was hounded for stating what he felt was true and denied many responsible posts that he should have had by merit alone. So just putting forward a statement like: "it is all to do with geometry" is ridiculous in the extreme. As for looking up stuff, I suggest you take your own advice because the POV advanced by you here does not make sense , except in the most broad terms.
Directional antenna, are useful even for space transmissions, but are only effective at close range (i.e., terrestrial applications) for instance a 1 cm square beam would spread out, according to the inverse square law, to an area of 6.25 million square kilometres by the time it reached the moon and by the time it reached the sun it would be several trillion square miles in area. Further what about light that does not obey the inverse square law such as collimated light and lasers. A laser can pack in a lot more information than any radio wave, so why not use them for deep space communication ? Ideally deep space communication should use long radio waves because these travel further, unfortunately they can carry little information.
When I was working nuclear power, on of my areas of expertise was Radiation Control. I am not talkiing theoretically here, I have measured the radiation decrease as part of my training. I have measured the energy of the gama rays as part of my training. It is rather odd that you don't seem to get that the inverse square law is a well documented phenomena, AND it is simple geometry to understand why it works.
You do realize that the difference between light and radio waves is just the frequency (or wavelength if you prefer). The reason I ask is because you seen to think that a directional radio wave would follow the inverse square law but a directional light source like a laser would not, when actually neither would.
The inverse square law ONLY applies to a point source. If there is a source such as a long neon tube and you are 5 feet way and then move to 10 feet away the decrease in intensity will NOT follow the inverse square law! Do you know why that is? If you guessed that it is simple geometry, you got the right answer...
Hi Origin,
Thanks for validating your remarks and giving some background. I think we are to a certain extent talking at cross purposes. Obviously the inverse square Law is based on Geometry, it is a way of explaining how light or (EMR ) spreads out as it travels, that point is taken as established. The point of contention seems to be what is the mechanics behind this spreading out of EMR according to the inverse square law, is it because of self sustaining electric and magnetic fields as suggested by Maxwell or is it due to some kind of interaction with 'virtual' particles as suggested by QM or is it due to electromagnetic fields that permeate the whole of the Universe. OR is it due to geometry alone ? I am not clear on what your stand is on this.
The second point we need to clarify is what exactly are we referring to when we speak of the inverse square law, are we talking about the space in your living room or are we talking about space tranmissions. Again, obviously if we are talking about the living room, then a tube light would be regarded as a line source and the radiation would fall off linearly (i.e., twice the distance half the intensity and not one quarter the intensity as would be the case with a point source) on the other hand when huge distances are involved as in deep space transmissions it does all come down to the inverse square law. There are numerous references to this at NASA web sites and in wikipedia ( Look under the sub-heading Computers.) Here is a quote from a power point presentation on satellite communication systems: Free space attenuation is determined by the inverse square law, which states that the power received is inversely proportional to the square of the distance . I hope that this post has clarified any doubts on what was being discussed.
Geometry alone. That is not only my stand but also the stand of science. I supplied you with a link that discussed the equations to obtain the inverse square relationship.
The inverse square law is applicable to your living room or interstellar space (for point sources).
I can only suggest that confirmation is needed from an unbiased source. I am very very clear that deep space transmissions (especially spacecraft to earth) follow the inverse square law. Any antenna gain is insignificant.
I could supply you with more sites that confirm that the inverse square law is simply consequence of geometry but you could simply look them up yourself and you clearly are not interested in that, it appears you want to stick with your preconcieved notioins - fine.
Your own source stated that voyagers directed signals do not follow the inverse square law but you have chosen to ignore your own source - fine.
Not sure why you want to engage in willful ignorance, but what the hell - knock yourself out!
I think we are getting bogged down here in a kind of childish argument 'is' and isn't' kind of thing. No-one disputes that if you extend a solid angle from a point on a sphere, what you get, geometrically is the inverse square law. That is not the point in question, what occupies that geometric space is.
I will ask you again, do you feel that that space (whether it comes under the inverse square law or of a directed beam) is (a) filled (in the case of EMR) according to Maxwell's theory by self sustaining electric and magnetic fields (b) by EM fields that occupy the whole of the Universe OR (c) 'virtual particles' that occupy all of space as in QM ? Again, data rate (that you have quoted) has nothing to do with the intensity of the signal.
Also radio signals from Voyager were only possible because the signal was in effect reflected back from the heliosphere and also to intermediate boosting of the signal by other deep space craft. I have detailed information and will post it soon. I agree that wiki may not be the best source.
(Originally posted by quant)I think we are getting bogged down here in a kind of childish argument 'is' and isn't' kind of thing. No-one disputes that if you extend a solid angle from a point on a sphere, what you get, geometrically is the inverse square law. That is not the point in question, what occupies that geometric space is.
(Posted by origin):Then why in the world did you write this???
Antenna gain, G, is the ratio of surface power radiated by the antenna to the surface power radiated by a hypothetical isotropic antenna.(Posted by Origin): As I have said before parabolic antennas do not follow the inverse square law.
Brilliant !!For example, the data rate used from Jupiter was about 115,000 bits per second. That was halved at the distance of Saturn So clearly these contradict each other! Jupiter is 4.2 AU from earth and Saturn is 8.5 AU from earth so if the inverse square law was in play the bit rate should have been quartered not halved!
Look you seem to have no idea on what I mean by the inverse square law.
Origin wrote
For example, the data rate used from Jupiter was about 115,000 bits per second. That was halved at the distance of Saturn So clearly these contradict each other! Jupiter is 4.2 AU from earth and Saturn is 8.5 AU from earth so if the inverse square law was in play the bit rate should have been quartered not halved!
Quant wrote
Brilliant !!