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This is speculation. There are all kinds of examples we have of "ancient" technology that are still in everyday use today - knives, for example. There's no rea

This is speculation. There are all kinds of examples we have of "ancient" technology that are still in everyday use today - knives, for example. There's no reason to think that something else would abandon using EM as a transfer of communication.

CamperBob2 10y ago
That's not what I said. Tune a general-coverage receiver to the frequency of an HDTV station, and what you hear is what the SETI folks will hear, whether there's a signal there or not.
- TeMPOraL 10y ago
  Also, from what I understand, the last several decades of our radio history were spent optimizing everything so that signals keep as much to the ground as possible - emitting TV into space is wasting money.
snowwrestler 10y ago
Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground. And even the terrestrial radio and TV stations still broadcasting are strictly power-limited to reduce geographic overlap. Most long-distance communication travels over wires too--everyone uses fiber backhaul. Phones and computers use EM (cellular, WiFi, Bluetooth) but the range is very short, so the signal power is far too low to report us to the universe. On top of that, most entertainment and communications signals today are digital, and many are encrypted. It's going to sound like noise to a receiver that doesn't know the encoding and/or have the encryption key. The most powerful space-facing EM emissions we make today, as a species, is probably RADAR, not a form of communications.
- dragonwriter 10y ago
  > Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground. Since I don't think its coming from manned satellites where the content is generated, I'm pretty sure there is a space-facing signal involved in satellite TV as well as a ground-facing signal.
  - snowwrestler 10y ago
    My understanding is that the uplink signal's power is much lower than the broadcast power, because each uplink signal is focused on its satellite by a parabolic dish. Sure some of the uplink will make it past the satellite, but that's a fairly low-power beam that would need to intersect an alien antenna to be heard.

CamperBob2 10y ago

That's not what I said. Tune a general-coverage receiver to the frequency of an HDTV station, and what you hear is what the SETI folks will hear, whether there's a signal there or not.

TeMPOraL 10y ago
Also, from what I understand, the last several decades of our radio history were spent optimizing everything so that signals keep as much to the ground as possible - emitting TV into space is wasting money.

snowwrestler 10y ago

Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground. And even the terrestrial radio and TV stations still broadcasting are strictly power-limited to reduce geographic overlap. Most long-distance communication travels over wires too--everyone uses fiber backhaul. Phones and computers use EM (cellular, WiFi, Bluetooth) but the range is very short, so the signal power is far too low to report us to the universe. On top of that, most entertainment and communications signals today are digital, and many are encrypted. It's going to sound like noise to a receiver that doesn't know the encoding and/or have the encryption key. The most powerful space-facing EM emissions we make today, as a species, is probably RADAR, not a form of communications.

dragonwriter 10y ago
> Think about how many people get their TV via a wire today, instead of via antenna. A lot of people get satellite TV, which is a strong signal but pointed toward the ground. Since I don't think its coming from manned satellites where the content is generated, I'm pretty sure there is a space-facing signal involved in satellite TV as well as a ground-facing signal.
- snowwrestler 10y ago
  My understanding is that the uplink signal's power is much lower than the broadcast power, because each uplink signal is focused on its satellite by a parabolic dish. Sure some of the uplink will make it past the satellite, but that's a fairly low-power beam that would need to intersect an alien antenna to be heard.