[ExI] Our radar means ET knows we're here

[Jason Resch]

On Wed, Jul 9, 2025, 5:21 AM BillK via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> Like it or not, radar means ET knows we're here
> By David Szondy       July 08, 2025
>
> <https://newatlas.com/space/radar-means-et-knows-were-here/>
> Quote:
> It turns out that when it comes to high-powered directional radar
> signals, the Earth is screaming like a banshee and has been since the
> early years of the Cold War in the 1950s. According to the study, the
> combined civilian radar signals from our planet add up to a whopping
> 2x1016 watts, with military systems adding in a more focused and
> directional signal of 1x1014 watts. And it generates a radio signature
> that screams artificial technology.
>


In Sagan's "Contact" it was our television transmissions.

But I think the more obvious (and much farther propagating) signal is the
spectral reflections of light from Earth's atmosphere, which would be
screaming the presence of life for billions of years to anyone bothering to
look in our direction. Similar to how we recently detected biogenic gases
on nearby explanets.

https://www.cnn.com/2025/04/17/science/k218b-potential-biosignature-webb


> This leakage from the Earth's air traffic and defense systems means
> that we are extremely visible to anyone within 200 light years of us
> that has a radio telescope equivalent to the Green Bank Telescope in
> West Virginia. If we take into account earlier studies that included
> larger, more powerful telescopes like the defunct Arecibo Observatory
> that limit extends to over 60,000 light years.


Eventually, but there are caveats.

This estimate assumes a similar sized antenna (as arecibo) pointed at the
same direction of earth waiting for arecibo's message, and within the path
of the highly directional transmission. And so far it's only had 51 years
to propagate, so the detection range is so far only 51 light years.


-------------------------
>
> OK, so maybe ET knows we're here. But we haven't detected similar
> radar signals coming from nearby stars.
> That means ET is not at the same stage of development as us and
> doesn't use similar radar systems.


We've only had radio ~130 years and we've already largely switched to fiber
optic and spread spectrum radio transmissions which are much harder to
distinguish from background noise. The window for obvious (incidental)
broadcasts of radio signals is therefore quite short when compared to
evolutionary time scales.


ET, like us, is still faced with
> the problem of the huge distances between star systems. When a star is
> 200 light years away, just saying "Hi" and getting a reply takes 400
> years. Actually visiting would take far, far longer.
> How to deal with the huge distances between star systems is a problem
> for all ETs.
>

On evolutionary time scales, it doesn't take long for an intelligent
civilization to spread throughout the galaxy and be everywhere at once. Von
Neumann probes can spread to reach every star system in the Galaxy in just
a million years. Moreover, with the computing capacity available to such
civilizations, it is also possible such probes could carry the uploaded
minds of every member of that civilization. Thus, they could all be
everywhere, and they would give no obvious signal of their presence (they
live in VR, running on comoutrobium on something no larger than a school
bus, not on far off planets blasting radio signals). In fact, every
intelligent civilization that's ever arisen in the Galaxy (and survived
long enough) could be everywhere already.

For a short story based on this idea, see:
http://FromBob.to

Jason
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