4 ms·

This "law" is only for point (or spherical) sources, i.e. those emitting evenly in all direction - the area is increasing as a square of distance and thus signa

by nuccy 2y ago

This "law" is only for point (or spherical) sources, i.e. those emitting evenly in all direction - the area is increasing as a square of distance and thus signal power drops accordingly. With lasers, directional antennas, phased array antennas [1] the signal won't decay that fast. For instance with lasers it will be just a matter of alignment of internal elements to obtain a parallel light beam which doesn't lose power over distance (obviously there are other factors - atmosphere, particles in the vacuum, et al which will result in diveregence anyway). In fact some billionaires [2] invest into using telescopes with fast sampling cameras (in this case IACT [3] telescopes used normally to detect gamma-rays by their interaction with the atmosphere) to detect flashed of extraterrestrial lasers. [1] https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/Phased_array (see the animation of the radiation pattern) [2] https://www.space.com/are-aliens-flashing-laser-beams.html https://www.space.com/are-aliens-flashing-laser-beams.html [3] https://en.wikipedia.org/wiki/IACT https://en.wikipedia.org/wiki/IACT

shiroiushi 2y ago
>This "law" is only for point (or spherical) sources, i.e. those emitting evenly in all direction We're not talking about lasers and directional antenna here, we're talking about humans using radio communications to talk to each other on Earth over the last 100 years, and whether that's detectable from great distances.
- T-A 2y ago
  There is a reason I included radar in my list. military radar transmissions set up during the Cold War to detect incoming ballistic missiles have the power and frequency characteristics to be detected over hundreds of light-years – and have already broadcast our existence to any aliens within around 60 light-years of the Earth [1] But never underestimate the power of television: The most detectable and useful escaping signals arise in a few ultra-powerful military radar systems and in normal television broad-casting. A model including over 2,000 television transmitters is used to demonstrate the wealth of astronomical and cultural information available from a distant observer’s careful monitoring of frequency and intensity variations in individual video carriers (program material is not taken to be detectable). [2][3] once the Square Kilometer Array is completed in Australia and Africa, it would be able to detect the current TV carrier wave radio leakage at a distance of about fifty lightyears for objects in the southern hemisphere sky [4] [1] https://www.sciencefocus.com/space/how-far-from-earth-could-aliens-detect-our-radio-signals https://www.sciencefocus.com/space/how-far-from-earth-could-... [2] https://link.springer.com/chapter/10.1007/978-94-009-9115-6_20 https://link.springer.com/chapter/10.1007/978-94-009-9115-6_... [3] https://www.science.org/doi/10.1126/science.199.4327.377 https://www.science.org/doi/10.1126/science.199.4327.377 [4] https://www.forbes.com/sites/quora/2017/01/27/how-far-into-space-can-radio-telescopes-hear/?sh=14d03de75de7 https://www.forbes.com/sites/quora/2017/01/27/how-far-into-s...

by nuccy 2y ago

shiroiushi 2y ago

>This "law" is only for point (or spherical) sources, i.e. those emitting evenly in all direction We're not talking about lasers and directional antenna here, we're talking about humans using radio communications to talk to each other on Earth over the last 100 years, and whether that's detectable from great distances.

T-A 2y ago
There is a reason I included radar in my list. military radar transmissions set up during the Cold War to detect incoming ballistic missiles have the power and frequency characteristics to be detected over hundreds of light-years – and have already broadcast our existence to any aliens within around 60 light-years of the Earth [1] But never underestimate the power of television: The most detectable and useful escaping signals arise in a few ultra-powerful military radar systems and in normal television broad-casting. A model including over 2,000 television transmitters is used to demonstrate the wealth of astronomical and cultural information available from a distant observer’s careful monitoring of frequency and intensity variations in individual video carriers (program material is not taken to be detectable). [2][3] once the Square Kilometer Array is completed in Australia and Africa, it would be able to detect the current TV carrier wave radio leakage at a distance of about fifty lightyears for objects in the southern hemisphere sky [4] [1] https://www.sciencefocus.com/space/how-far-from-earth-could-aliens-detect-our-radio-signals https://www.sciencefocus.com/space/how-far-from-earth-could-... [2] https://link.springer.com/chapter/10.1007/978-94-009-9115-6_20 https://link.springer.com/chapter/10.1007/978-94-009-9115-6_... [3] https://www.science.org/doi/10.1126/science.199.4327.377 https://www.science.org/doi/10.1126/science.199.4327.377 [4] https://www.forbes.com/sites/quora/2017/01/27/how-far-into-space-can-radio-telescopes-hear/?sh=14d03de75de7 https://www.forbes.com/sites/quora/2017/01/27/how-far-into-s...