Capiert Posted February 16 Share Posted February 16 As far as I know water_waves travel e.g. at c. How do you deal with low frequency RF? Radio_particles? (Radions?) Link to comment Share on other sites More sharing options...
MigL Posted February 16 Share Posted February 16 They would ask "Why is a medium needed ?". They might also ask about the formatting of your posts ... Link to comment Share on other sites More sharing options...
Externet Posted February 16 Share Posted February 16 Radio waves propagate same as light from the sun does without a medium. Low or high frequency mean nothing. Waves in water are a mechanical disturbance, not electromagnetic. Link to comment Share on other sites More sharing options...
John Cuthber Posted February 16 Share Posted February 16 If you are heading towards the transmitter really fast, a radio wave is light. And a vacuum can't tell how fast you are going. Link to comment Share on other sites More sharing options...
Capiert Posted February 16 Author Share Posted February 16 (edited) Thank you, both of you. 1 hour ago, MigL said: They would ask "Why is a medium needed ?". Why do water_waves need a medium? (elastic, mechanically like a flexible_spring). Why do you exclude with electromagentism? Didn't Maxwell (also) calculate the (mechanical) Young's Modulus (~Flexibility) for electromagnetism (too)? 1 hour ago, MigL said: They might also ask about the formatting of your posts ... Why only might? 1 hour ago, Externet said: Radio waves propagate same as light from the sun does without a medium. Can you please explain that to me? A wave of(=on) what? 1 hour ago, Externet said: Low or high frequency mean nothing. Good. I thought a slower frequency might be a bit helpful (simpler) to comprehend & understand. At least for me. 1 hour ago, Externet said: Waves in water are a mechanical disturbance, not electromagnetic. I assume by mechanical you mean a sort of elasticity.(?) If an ion fluid is vibrated then electromagnetic disturbances (such as waves) are also produced! Or at least expected (by me). E.g. Sea_water. (But that effect does NOT have to be with salt.) E.g. (The) Water (molecule) is polar & has a dipole moment. E.g. The photo_acoustic effect producing soundwaves (ultrasound) from light's interaction. I suspect a similar process in reverse is also possible. Perhaps in a crystal. Edited February 16 by Capiert Link to comment Share on other sites More sharing options...
Sensei Posted February 16 Share Posted February 16 Quote How do scientists explain RF waves traveling, without a medium? Philosophy is a pseudoscience. Physics is a real science. Too often you ask philosophical questions.. ask physical questions, such as "how to measure the speed of something", "how to measure some physical quantity", etc., and you will get the right, truthful answers.. 1 hour ago, Capiert said: As far as I know water_waves travel ..one water molecule hits another molecule, which hits another molecule, and there is a momentum transfer between them in all directions, they hit something, while molecule remain at place (plus, minus, a little margin of tolerance (in global scale) ).. 1 hour ago, Capiert said: Radio_particles? (Radions?) They are called photons.. Link to comment Share on other sites More sharing options...
Bufofrog Posted February 16 Share Posted February 16 1 hour ago, Capiert said: As far as I know water_waves travel e.g. at c. What is that supposed to mean? Since you used e.g. which means 'for example', you are saying, "As far as I know water_waves travel [for example] at c." No water waves don't travel at c. 1 hour ago, Capiert said: How do you deal with low frequency RF? EM radiation and water waves are very different things. A water wave is a disturbance in a medium. EM waves are not a disturbance in a medium, they are a disturbance in a field. Link to comment Share on other sites More sharing options...
Capiert Posted February 16 Author Share Posted February 16 Hi John 14 minutes ago, John Cuthber said: If you are heading towards the transmitter really fast, a radio wave is light. That's a good example! 14 minutes ago, John Cuthber said: And a vacuum can't tell how fast you are going. What do you mean there, John? I DON'T think a vacuum can tell us anything. We would need a(nother) speed (as) reference which could be either in or out of the vacuum (to compare speeds). DON'T you think? Link to comment Share on other sites More sharing options...
Sensei Posted February 16 Share Posted February 16 6 minutes ago, Capiert said: Can you please explain that to me? A wave of(=on) what? Wavelength is part of the photon energy equation E=hc/wavelength Link to comment Share on other sites More sharing options...
Capiert Posted February 16 Author Share Posted February 16 7 minutes ago, Sensei said: Philosophy is a pseudoscience. Physics is a real science. Too often you ask philosophical questions.. ask physical questions, such as "how to measure the speed of something", "how to measure some physical quantity", etc., and you will get the right, truthful answers.. Hi Sensei This (thread's) question is a real question expecting real answers. I'm trying to figure it out. "Your" questions DON'T answer "my" question. But they can help. 7 minutes ago, Sensei said: ..one water molecule hits another molecule, which hits another molecule, and there is a momentum transfer between them in all directions, they hit something, while molecule remain at place (plus, minus, a little margin of tolerance (in global scale) ).. You say they hit but Bohr showed us from the very 1st in his younger year that contact is a virtual thing. The atoms do NOT touch each other. They (atoms) interact elastically at a distance with fields. 7 minutes ago, Sensei said: They are called photons.. OK. That's a good place to start. If you have a (single) photon with a wavelength of 21 cm, what does it look like? Is it round like a ball? How big is it really? E.g. what is its diameter? How do I co_relate its intensity to its (physical) size? How much momentum does it have? 20 minutes ago, Bufofrog said: What is that supposed to mean? Since you used e.g. which means 'for example', you are saying, "As far as I know water_waves travel [for example] at c." Yes, water waves travel, they are travelling on or in a medium (called water); & the (traveling=propagation) speed of that medium is typically (the symbol) c (in the formula), which in that case (=example) is 2 m/s. Although sound waves travel 1500 m/s in water (compared to 340 m/s in air). So depending on what kind of wave, then c has different values. 20 minutes ago, Bufofrog said: No water waves don't travel at c. I'm sorry, but water waves (do) travel at c, & "that" value for c is 2 m/s. 20 minutes ago, Bufofrog said: EM radiation and water waves are very different things. Yes, I think so. 20 minutes ago, Bufofrog said: A water wave is a disturbance in a medium. EM waves are not a disturbance in a medium, they are a disturbance in a field. What is a field? Link to comment Share on other sites More sharing options...
Bufofrog Posted February 16 Share Posted February 16 9 minutes ago, Capiert said: This (thread's) question is a real question expecting real answers. As I said before, EM radiation and water waves are very different things. A water wave is a disturbance in a medium. Photons are not a disturbance in a medium, they are a disturbance in a field. 11 minutes ago, Capiert said: If you have a (single) photon with a wavelength of 21 cm, what does it look like? It doesn't look like anything, the question doesn't even make sense. 12 minutes ago, Capiert said: Is it round like a ball? No 14 minutes ago, Capiert said: How big is it really? Depends on what you mean by "really". 15 minutes ago, Capiert said: E.g. what is its diameter? It makes no sense to ask what it's diameter is. 16 minutes ago, Capiert said: How do I co_relate its intensity to its (physical) size? You don't. Link to comment Share on other sites More sharing options...
Capiert Posted February 16 Author Share Posted February 16 1 hour ago, Sensei said: 1 hour ago, Capiert said: Can you please explain that to me? A wave of(=on) what? 1 hour ago, Sensei said: Wavelength is part of the photon energy equation E=hc/wavelength That looks (a bit) like you are avoiding my question Sensei. We KNOW we are dealing with a wave, thus it has a (pretty obvious) wave_"length". But I did NOT ask that. I asked what was the wave "on". Link to comment Share on other sites More sharing options...
exchemist Posted February 16 Share Posted February 16 1 hour ago, Sensei said: Philosophy is a pseudoscience. Physics is a real science. Too often you ask philosophical questions.. ask physical questions, such as "how to measure the speed of something", "how to measure some physical quantity", etc., and you will get the right, truthful answers.. ..one water molecule hits another molecule, which hits another molecule, and there is a momentum transfer between them in all directions, they hit something, while molecule remain at place (plus, minus, a little margin of tolerance (in global scale) ).. They are called photons.. Philosophy is not a pseudoscience. 1 Link to comment Share on other sites More sharing options...
Sensei Posted February 16 Share Posted February 16 (edited) 1 hour ago, Capiert said: OK. That's a good place to start. If you have a (single) photon with a wavelength of 21 cm, It is relative. The one observer will detect it as 21 cm, the other might it detect as 42 cm (red shifted), the other might it detect as 10.5 cm (blue shifted). Actually any wavelength. Because in Special Relativity you have no absolute wavelengths.. https://en.wikipedia.org/wiki/Redshift https://en.wikipedia.org/wiki/Redshift#Blueshift 1 hour ago, Capiert said: what does it look like? Is it round like a ball? None a single particle has the shape.. 1 hour ago, Capiert said: E.g. what is its diameter? Such questions have no sense.. Particle is detected if it interacts ("hits") the other particle. If it hits it, it transfers some physical quantity on the second particle. Therefore we know there was interaction.. The diameter of an atom can be "measured" because scientists use the flux of other particles toward the nucleus. If these are reflected, the "diameter" of the multi-particle entity, called the "nucleus," can be measured by the angles at which the initial particles were reflected. It is called cross section. https://en.wikipedia.org/wiki/Cross_section_(physics) The different isotopes have different cross sections. "If a poacher shoots birds with a shotgun, he will eventually shoot any bird.." 26 minutes ago, Capiert said: That looks (a bit) like you are avoiding my question Sensei. We KNOW we are dealing with a wave, thus it has a (pretty obvious) wave_"length". But I did NOT ask that. I asked what was the wave "on". The wavelength is a property of the particle. Its (kinetic) energy can be mentioned instead of wavelength and get the same results.. e.g. the beam of electrons in vacuum with kinetic energy of 100 keV has similar effects on the matter as beam of photons with 100 keV. e.g. electrons in the matter will be excited and/or ejected (with the exception that other physical quantities such as Lepton number, must be preserved, so electron gives its kinetic energy, and is not disappearing (is not absorbed) ). Instead of saying "green photon" or "photon with a wavelength of 532 nm," you can say "photon with an energy of 2.33 eV." It's all the same. Edited February 16 by Sensei Link to comment Share on other sites More sharing options...
Capiert Posted February 16 Author Share Posted February 16 40 minutes ago, Bufofrog said: As I said before, EM radiation and water waves are very different things. A water wave is a disturbance in a medium. Photons are not a disturbance in a medium, they are a disturbance in a field. I suspect I need a comparison of a field & a medium. 40 minutes ago, Bufofrog said: It doesn't look like anything, the question doesn't even make sense. Yes! (So) We (now) have something that looks like NOTHING. But I suspect you are implying that photons are (particles) too small to see. We would need a particle much smaller than a photon; & the vision apparatus for that smaller particle. Basically, (then) I'm asking for (what is) the "shape" of a photon because (you claim) it is (suppose to be) a (real=physical) particle. Otherwise "your" physics is (still) NOT making sense to me. 40 minutes ago, Bufofrog said: No Well if the photon (particle) is NOT round; then what is its shape. I'm NOT satisfied with pseudoscience. Real particles have real dimensions. They are NOT just imagination dreamt up by pseudo scientists. Science is measurement; NOT (always) its theory (ideas). I.e. Opinions from scientists. 40 minutes ago, Bufofrog said: Depends on what you mean by "really". I have a big gulf (gorge) between talking about a wave_"length" e.g. 21 cm versus something as small as an optical photon. I have difficulty conceiving a real particle with the (conflicting) info (clues, hints given). It does NOT make sense. Thus I am requesting a (more) reasonable example. 40 minutes ago, Bufofrog said: It makes no sense to ask what it's diameter is. If that is because it is NOT round then please describe this real particle's shape. I.e. Photon. 40 minutes ago, Bufofrog said: You don't. Naturally I have NOT co_related the photon's intensity to its size. But why NOT? Link to comment Share on other sites More sharing options...
Genady Posted February 16 Share Posted February 16 In QFT, photon does not have dimensions. Link to comment Share on other sites More sharing options...
swansont Posted February 17 Share Posted February 17 49 minutes ago, Capiert said: Real particles have real dimensions. Not so much. Fundamental particles are point-like. Physical size has little meaning in QM; it’s the interactions that matter. EM radiation requires no medium; electric and magnetic fields can and do exist in a vacuum. Link to comment Share on other sites More sharing options...
Bufofrog Posted February 17 Share Posted February 17 41 minutes ago, Capiert said: I suspect I need a comparison of a field & a medium. Then you need some work to do don't you. 42 minutes ago, Capiert said: But I suspect you are implying that photons are (particles) too small to see. Nope not saying that at all. Most anti-science trolls have some knowledge about science, I guess you are the outlier. 44 minutes ago, Capiert said: I have a big gulf (gorge) between talking about a wave_"length" e.g. 21 cm versus something as small as an optical photon. Yes, that is because you have not spent any time to learn anything. Photons can have a wave length of a kilometer, so you must think those photons are 1 km in size? Maybe this will help the wavelength has nothing to do with the 'size' of a photon. 49 minutes ago, Capiert said: It does NOT make sense. Well if you can't understand it then we must immediately change all of our theories! 52 minutes ago, Capiert said: If that is because it is NOT round then please describe this real particle's shape. I.e. Photon. I think I already said that a photon doesn't look like anything. It makes no sense to think a photon looks like something. 54 minutes ago, Capiert said: Naturally I have NOT co_related the photon's intensity to its size. But why NOT? Because that is nonsense. Link to comment Share on other sites More sharing options...
KJW Posted February 17 Share Posted February 17 2 hours ago, Capiert said: Why do water_waves need a medium? What is a water wave without the water? In the case of an electromagnetic wave, without the medium, one still has the electromagnetic wave. Link to comment Share on other sites More sharing options...
MigL Posted February 17 Share Posted February 17 An Electromagnetic Field is a value and direction ( vector ) associated with each point in space. A Medium is a particle at each point in space, that has an oscillation as part of its motion. A Photon is best described as a point ( dimensionless ) quantum particle that is 'smeared out' over a volume with no distinct edge. But in its other model of a wave, an 'exact' value of its energy will make its wavelength infinitely long, so it is in no way related to its size. You may have gathered, by now, that quantum objects don't act the same as macroscopic objects. So, I ask, again, why do you think quantum particles, like photons, would need a medium like macroscopic objects, such as water waves, do ? Link to comment Share on other sites More sharing options...
John Cuthber Posted February 17 Share Posted February 17 14 hours ago, Capiert said: What do you mean there, John? I mean that it's impossible to define your speed with respect to a vacuum. (This makes life rather difficult for traffic police in interstellar space) Link to comment Share on other sites More sharing options...
geordief Posted February 17 Share Posted February 17 (edited) 1 hour ago, John Cuthber said: mean that it's impossible to define your speed with respect to a vacuum If the vacuum is filled with quantum foam (a big "if" ,as I don't understand what that means) could an object's speed/velocity be referred to different locations in that quantum foam? Does the term "location" not apply ,perhaps wrt quantum foam? Said in another way ,could the quantum foam be considered to be a medium? Edited February 17 by geordief Link to comment Share on other sites More sharing options...
Genady Posted February 17 Share Posted February 17 (edited) deleted Edited February 17 by Genady Link to comment Share on other sites More sharing options...
MigL Posted February 17 Share Posted February 17 Quantum foam 'exists' ( ? ) at a scale where space-time becomes chaotic, and virtual particles b( the ones without a defined position or momentum )pop in and out of existence ( for an undefined time ). How would you specify a position relative to it ? You can consider anything a medium, but what is actually 'waving' ? Link to comment Share on other sites More sharing options...
John Cuthber Posted February 17 Share Posted February 17 12 minutes ago, Genady said: So far, all this quantum stuff, like QFT, is Lorentz invariant, and thus the answer is, no. I'm really glad someone knew the answer. Thanks Link to comment Share on other sites More sharing options...
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