Light and radio transmissions are the same thing, just using different frequencies.
How is it reasonable that I can transmit with a radio using the energy of a low energy light bulb (10 watts), and easily chat with someone 1800km away?
Even if you imagine a perfectly dark world, where the only light bulb is a 10W bulb in Sweden; How is it even possible that this could be seen in Italy? It’s not even a spotlight! It’s only vaguely aimed away from east-west, in favour of up, north, and south.
My little light bulb (radio) could be seen in (approximately) all of Europe. ~750 million people potentially could have received it at the same time. With 10 watts.
“Blink blink” — All of Europe can see my little lightbulb.
And this isn’t some specialized super duper antenna, nor was it set up by an expert, fine tuning everything. I just put up the antenna in a PVC pipe and connected it. We can’t even credit fancy computers digging signals out of the noise. This was not FT8, this was PSK31. I’m sure voice would also have worked.
I also used FT8 with these same 10W to check off country after country. Not even a challenge.
This is not close to a record, or even a personal record. I’ve been heard in the US, and even in Brazil. 10W has even been used by amateurs to bounce signals off the moon! (though that took more effort with directional antennas)
This is completely unreasonable, and it’s great. Amateur radio is fun!
If I can do this with amateur radio, then it’s more understandable (but of course even more amazing) that NASA can talk to a probe more than 22 light-hours away.
This is the modest setup I used to chat over 1800km using 10 watts: