Timeline for Need a way for Earth not to detect an extrasolar civilization that has radio
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 5, 2016 at 22:11 | comment | added | AndrejaKo | A transmitter antennas are going to be on top of a large structure, which itself, might be on top of a mountain. Often for broadcasting, antennas which have circular azimuth radiation diagram are used, but the elevation radiation diagram will either be as flat as possible, or even pointing down. | |
| Dec 5, 2016 at 22:09 | comment | added | AndrejaKo | @HDE 226868♦ Lobe flattening is almost always done with broadcast signals. Take a look at the article for Collinear antenna arrays Some fancier applications use Phased arrays and for higher frequencies, there are slotted waveguide antennas. | |
| Dec 5, 2016 at 16:48 | comment | added | kingledion | @MichaelKarnerfors Then you should put all that information in your answer. | |
| Dec 5, 2016 at 16:45 | comment | added | MichaelK | @kingledion And they too are highly directional. Meaning that — taking into account the rotation of this alien planet — we would get a blip at the most as the lobe sweeps past us. And — again — the Inverse-Square law. Geostationary orbit is a few tenths of a light second out, whereas 200 light years is at least 10 billion times the distance. 10 billion times means an attenuation of approximately 200 dB. | |
| Dec 5, 2016 at 16:37 | comment | added | kingledion | However, signals heading outbound to satellites are going right into space... | |
| Dec 5, 2016 at 16:35 | comment | added | HDE 226868♦ | Can you explain how they can shape the lobes? They'd have to do that for every single device that emits a radio wave, and could be more trouble than it's worth. | |
| Dec 5, 2016 at 16:32 | comment | added | MichaelK | @kingledion Satellites if anything have always had highly directional transmissions. Considering the distance and that pesky Inverse-Square Law it has more or less been an absolute necessity to not transmit isotropically when it comes to satellites. And those transmissions are — invariably — aimed right at the ground. | |
| Dec 5, 2016 at 16:28 | comment | added | kingledion | Do they not use satellites for communication? If they use satellites then there will be at least some transmissions going into space. This doesn't provide any analysis of how much and advanced civilization could reduce the amount of energy going into space compared to what we emit now. | |
| Dec 5, 2016 at 13:23 | history | notice added | HDE 226868♦ | Hard Science | |
| Dec 5, 2016 at 8:55 | history | answered | MichaelK | CC BY-SA 3.0 |