(July 14, 2025 at 8:59 pm)Thumpalumpacus Wrote:(July 14, 2025 at 6:15 pm)Ravenshire Wrote: How could aliens up to 200 light-years away detect signals (radar) that weren't broadcast until the 1930s?!? Even if you count all the way back to the first radio broadcast ever, you only get to the the closing days of the 19th century, Dec. 23rd, 1900.
Our radio transmission bubble is just 125 light-years in radius, at a maximum. Due to signal attenuation, the effective detectable bubble is likely considerable less than that.
Even given an antenna that could pick up those very first radio signals, it'll be Dec. 2100 before they'll even reach an ET 200 light-years away.
I don't think the point is that putative aliens may have already detected us at 200 ly, I think the point is that they may well do so going forward. Because if their tech is sufficiently advanced, these signals will be available at least from the 1950s (and the advent of NORAD or its Soviet counterpart) up through today. Even that bubble, 140 ly across, encompasses what is clearly a lot of planets suitable for life even if we haven't found any life itself so far.
It should be remembered too that reception is a bit easier than transmission.
Fair enough, but there's also this:
If you threw a dart at the map of the Milky Way, and wherever that dart landed is where an advanced alien species resides, there would be a cosmically small probability that they live close enough to be aware of our existence. Even if you threw 100 darts, it's a near certainty that none would land in the little blue bubble of our radio waves.
A 200 ly bubble, while it is a mind bendingly large volume of space at human scale, is a mere rounding error at the galactic scale.
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