Ah sorry, I probably wasn't clear enough what I meant (and am not super knowledgable here and probably have a western bias). What I meant was civilization defined like this https://en.wikipedia.org/wiki/Cradle_of_civilization not that there weren't any cultures earlier. I basically just wanted to say that 66000 years is a very long time in human time scales

Nothing would beat light as far as transmission goes. Also, the further the shutter the further that doesn't matter. As the galaxy expands you might block light for something that'll have moved away and miss the signal, so it's a pretty big risk to try and position this shutter strategically enough to make that work.

However, a fun thing to think about is, after you make your signal thing to broadcast, by the time that message reaches other galaxies, 33k years is long enough that other life might very well have come into existence and evolved.

Even crazier to think someone out there may have already broadcast their own message and we don't have the means or technology to receive it or notice because they are so many others out there, OR it just hasn't reached us yet. Maybe in another could thousand years.

Sure you can put it farther away, but the sun is massive, it would still need to be pretty big I would guess, but I'm not an astronomer so I don't know the numbers.

As far as I know we don't know of any faster way to send signals. That doesn't make sending the signals impossible, just very impractical.

I am willing enter the dumbass territory here, but - raido waves, being electromagnetic, and light travel at the same speed. Even if there is technically a difference, it is probably insignifact for the amount of distance each would have to cover before it can effectively transmit anything.

The convenience of a radio signal is that the transmitter is much easier to point in different directions, primarily because it's a lot smaller than a star, but also because it can (at least in theory) be pointed in directions normally blocked by other celestial bodies. Given the position and orbital physics of a solar system, it would insanely difficult to position something directly "above" or "below" the Sun, let alone something as big and technologically advanced to block enough light, at an adequate frequency, to transmit any data. While a radio transmitter can be launched into space and positioned sufficiently far from other objects in the solar system to send data into various points of space. There can even be multiple such satellites, for all sorts of directions, coupled with repeaters and everything, while we only have one star in the system.

Of course, radio also depends on the receivers, even regardless of the data transmitted, but I believe in aliens, they'll figure something out.

While radio telescopes are arguably slower then the speed of light, being able to encode and compress data into a radiowave is a faster way to communicate.