[enkid]

IIRC, we wouldn't be able to pick up our own broadcasts from Alpha Centauri because of the loss of radio transmission power. I doubt we would know if an alien civilization was transmitting at us, even if it was trying to get our attention.

[sjy]

The Breakthrough Listen initiative claims that it is sensitive to “Earth-leakage” levels of radio transmission from all 43 stars within 5 parsecs: https://breakthroughinitiatives.org/news/3

[notsuoh]

Attenuation of radio waves (long membrane) is way too high, that's true, but radio isn't the only way to transmit that we could theoretically pick up. Gravity waves for example would be a way to transmit across the whole universe.

[enkid]

Gravity waves would still have similar issues. The only gravity waves we can pick up right now are from extremely dense bodies colliding with each other. Not exactly a feasible means for intergalactic communication.

[halfdan]

Unless your hobby involves collecting black holes and smashing them into each other...