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Comment by adrianN | Hacker News Reader

You'd be able to detect radio waves from Earth. We can still communicate with the Voyager probes that are further out. We probably can't detect life on Earth from Alpha Centauri with our current technology.

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> We can still communicate with the Voyager probes that are further out.

This is what I mean by "knowing exactly what to look for."

Can we place something at Pluto and have it listen to radio waves from the direction of Earth, and compare it to the background "noise" at that location? How different is it? How much of that perceived difference would be our own bias?

How much evidence about life on Earth is available to our own instruments from this range? -> https://www.bing.com/images/search?q=Pale+Blue+Dot

That's a cosmically trivial distance. Yes we could absolutely detect vast amounts of transmissions at that range, and even figure out how to decode a lot of them. For example video transmissions clearly have a tabular data structure, pixel data structure, timing encoding, serial frames, etc. Theres no way they could be natural. You could even see differences over time as video standards evolve and update. That's just one example. Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data, so determining useful data from vast ranges and quantities of non-encrypted transmissions would be comparatively easy.

> Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data

Yes, but data created and encoded by other humans. We would likely not even know where to begin when encountering data (assuming we even recognized it as such) from beings who may perceive reality completely differently.

99.9999999999999999% of radio waves we get from the rest of the universe is absolute garbage. There would be some kind of pattern with purposeful radio communications. Recognizing purposeful radio communication is a much easier task than interpreting the data. But we don't need to interpret the data to know it came from someone/something we should go and check out, because it could be intelligent life.

Maybe it’s encrypted.

The Voyager probes emit less radiation than your typical cell phone, so the Megawatts of emissions we produce would be very bright on typical radio telescopes on Pluto, I presume.

Voyager transmitters are in 10 watt range. On 2 and 8 GHz bands.

Lots of interesting reading, for those so inclined, at https://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_n...

Planets are not normally radio sources. You can detect Earth as a planet from Pluto, and you can say that this planet is a strong radio source in various bands. As a radio source it has changed over time in interesting ways that are very unlikely to be natural.

Planets can be very strong radio sources; there are astronomers who spend their entire careers recording and studying Jupiter in the 21 MHz band, for example.

https://www.spaceacademy.net.au/spacelab/projects/jovrad/jov...

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