Space is really really big.

[Ray McCarthy]

hen again, perhaps the natural weakening of our own broadcasts is process enough - that no one would necessarily know we are here - and conversely, we'd struggled to detect similar from other civilisations.

Spectroscopic Analysis works at MASSIVE distances as it uses starlight as the "transmitter" and detects the dips caused by different compounds in the atmosphere of planet in transit.
O2 CO2, signatures indicate possible life. Industrialisation causes "signatures" not plausible from any known natural source such as volcanoes, sunlight on atmosphere or under sea vents.

We have only started with Spectroscopic Analysis and need bigger telescopes in space. This will see a huge jump in our knowledge in the coming years just with the planned telescopes. Computer analysis of the existing recent data (over last 20 years) is improving too.

 

[J Riff]

I am happy to hear that the Fermi paradox is not currently active.
Any polarized thinking, as in its A or B and nothing else, could lead to much problemos in a Universe like this one. There's different types of logic happening, and I think I might, maybe, have a vague grip on some of that end of things - but the science and esp. physics has to match up, somehow, eventually, for all currently unexplained phenomenon. Phenomena?
ET must be the only major SF movie I have never seen, this is unexplainable.

 

[Ray McCarthy]

ET must be the only major SF movie

It's more a fairy tale for kids than SF.

 

[Ray McCarthy]

xkcd: Voyager 1

 

[Extollager]

So, Ray: is it that if there are civilizations on other planets it's almost certain we will never know?

 

[Ray McCarthy]

is it that if there are civilizations on other planets it's almost certain we will never know?

We'll suspect that they exist. Maybe inside next 10 years, from spectroscopic analysis. Industrialisation is believed to create a very distinctive spectrograph compared to naturally released or produced chemicals and gasses. The possible range even today is very great.

Will we be able to communicate?
Rapid communication is purely in the realms of speculation and depends on something unexpected in physics being discovered.
We could eventually send a physical probe that might take hundreds or even thousands of years to get there, then they might notice it and send back a physical probe. Though probes are much slower than radio or laser, they have no real distance limitation and can carry a lot of information.
They used to say a station wagon full of computer tapes would beat any data connection (radio or copper). Now a pigeon with a micro SD card can beat a fibre link for data, just the latency is high. At even 20 light days distance the radio or laser communications is slower than old fashioned dial-up of the 1980s! Shannon's Law. Even a very small probe can carry an awesome amount of information.