Dan9191 Posted November 7, 2018 Share Posted November 7, 2018 How do I i find a wave source (location where its transmited from) if I have where the wave is transmitted to (the destination) and I have the right measuring equipment? Which measuring equipment is needed? Link to comment Share on other sites More sharing options...
Strange Posted November 7, 2018 Share Posted November 7, 2018 You can find the direction it is coming from (for example, from the direction you have to turn your telescope or detector) but you can't find the distance from a single destination. But if you can have two detectors at different locations then you can use the two directions to calculate the distance using triangulation. This is used for navigation, to find the distance to stars, etc. Link to comment Share on other sites More sharing options...
studiot Posted November 7, 2018 Share Posted November 7, 2018 Well I have just logged in and I see that you posted your shouted question less than half an hour ago, but can't be bothered to wait for an answer. You need to tell us more about the situation to get a proper answer. What sort of wave would be a good start? 9 minutes ago, Strange said: You can find the direction it is coming from (for example, from the direction you have to turn your telescope or detector) but you can't find the distance from a single destination. But if you can have two detectors at different locations then you can use the two directions to calculate the distance using triangulation. This is used for navigation, to find the distance to stars, etc. If both you and the source of the waves are on the surface of the Earth, two directions plus the distance apart of the receiving stations will do. If the source is up in the air then a third measurement is required. With certain waves it is possible to measure distance from a single source, to a single receiver, which is why we need to know more. Link to comment Share on other sites More sharing options...
StringJunky Posted November 7, 2018 Share Posted November 7, 2018 11 minutes ago, Strange said: You can find the direction it is coming from (for example, from the direction you have to turn your telescope or detector) but you can't find the distance from a single destination. But if you can have two detectors at different locations then you can use the two directions to calculate the distance using triangulation. This is used for navigation, to find the distance to stars, etc. Just thinking aloud: If you knew the luminosity of the source, couldn't you work with the inverse square law but reverse it to get the distance? Link to comment Share on other sites More sharing options...
Sensei Posted November 7, 2018 Share Posted November 7, 2018 (edited) Quote Finding source of wave (location where its transmited from) while im on the destination with the right equipment If source of light, or source of sound waves, is emitting uniformly, with the same power, and thus obeying inverse-square law, you can use simple triangulation. Two or three detectors are needed if source and detectors are static (not moving). But it can be replaced by single detector, if source is static, but detector will be moving. Samples taken with delay. Assuming there is no reflection or refraction.. Edited November 7, 2018 by Sensei Link to comment Share on other sites More sharing options...
Strange Posted November 7, 2018 Share Posted November 7, 2018 8 minutes ago, studiot said: If the source is up in the air then a third measurement is required. Excellent point. Edit: surely that is only true if you are using omnidirectional receivers? If you have two telescopes, for example, that would give you position and distance ... wouldn't it? 6 minutes ago, StringJunky said: Just thinking aloud: If you knew the luminosity of the source, couldn't you work with the inverse square law but reverse it to get the distance? Also an excellent point. And, if we are considering all possibilities, if the source is at cosmological distance then you can determine the distance using redshift. Link to comment Share on other sites More sharing options...
studiot Posted November 7, 2018 Share Posted November 7, 2018 6 minutes ago, StringJunky said: Just thinking aloud: If you knew the luminosity of the source, couldn't you work with the inverse square law but reverse it to get the distance? Yes, in astronomy they also use relative brightness for known stars. Link to comment Share on other sites More sharing options...
StringJunky Posted November 7, 2018 Share Posted November 7, 2018 20 minutes ago, studiot said: Yes, in astronomy they also use relative brightness for known stars. That's what sparked the thought: standard candles. Link to comment Share on other sites More sharing options...
Sensei Posted November 7, 2018 Share Posted November 7, 2018 (edited) 23 minutes ago, studiot said: Yes, in astronomy they also use relative brightness for known stars. Relative brightness you will get just because of movement of the Earth around the Sun. [math]P_a =\frac{P_0}{4 \pi r_1^2}[/math] [math]P_b =\frac{P_0}{4 \pi r_2^2}[/math] r2 = r1+300 mln km (Earth orbits around the Sun.. half year later is ~300 mln km away) so [math]P_0 = P_a 4 \pi r_1^2 = P_b 4 \pi (r_1+3*10^8)^2[/math] It could be confronted with parallax technique for the closest stars to verify calculations of opposite method. Edited November 7, 2018 by Sensei Link to comment Share on other sites More sharing options...
Strange Posted November 7, 2018 Share Posted November 7, 2018 10 minutes ago, Sensei said: It could be confronted with parallax technique for the closest stars to verify calculations of opposite method. And then the distance ladder for the full range of distances: https://en.wikipedia.org/wiki/Cosmic_distance_ladder Link to comment Share on other sites More sharing options...
Klaynos Posted November 7, 2018 Share Posted November 7, 2018 Just to add even more... If it's a pulse you can use time of arrival differences between multiple sites to do a triangulation. We really do need more information. Link to comment Share on other sites More sharing options...
Strange Posted November 7, 2018 Share Posted November 7, 2018 1 hour ago, Klaynos said: Just to add even more... If it's a pulse you can use time of arrival differences between multiple sites to do a triangulation. We really do need more information. Nice. That is how the sources of gravitational waves have been (roughly) located. Link to comment Share on other sites More sharing options...
Klaynos Posted November 7, 2018 Share Posted November 7, 2018 10 minutes ago, Strange said: Nice. That is how the sources of gravitational waves have been (roughly) located. It is indeed. They use some really cool correlation methods... Link to comment Share on other sites More sharing options...
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