[ExI] [Extropolis] Crosspost

[Keith Henson]

I could go through the math and logic starting with the size of the
dips and the transit times plus why I was strongly biased against
megastructures and why very reluctantly came to the conclusion I did,
plus some of the local long-term consequences for humanity where this
line of thinking led regardless of what we are observing.  But it does
not seem to be worthwhile to do so.

I freely acknowledge my tentative conclusions could be wrong, and hope
they are because they may have dire consequences for the future of
humans and our AI offspring.  I understand why people don't want to
deal with this possibility and I don't blame you,  The local problems
are enough to saturate our worry centers.

Just FYI, the thing that pushed me over the edge was reports that
there are 23 other stars in a cluster that also have light dips like
Tabby's star.  I lack the imagination to understand this as anything
but intentional or to dismiss it.  The closest one is 511 ly.  The
spreading seems to be around 1/3 of c.  Either we will go there, or
they will come to us and we will know.  If we see Vista being turned
into a data center we will know.  Not that we could do anything about
it.

Keith

On Thu, Apr 17, 2025 at 3:51 AM John Clark <johnkclark at gmail.com> wrote:
>
> On Wed, Apr 16, 2025 at 7:05 PM Keith Henson <hkeithhenson at gmail.com> wrote:
>
>>>
>>> > If ET does exist, and I don't think he does, then it would be very surprising if he was only 3000 years ahead of us because the universe is 13.8 billion years old.
>>
>>
>> > Surprising is certainly the right word, not only in the span of time
>> but *close* physically.  1470 ly is practically next door.
>
>
> Doesn't that make you question your theory that ET is responsible for the dimming of Tabby's star?
>
>>
>> > But no matter how unlikely something is, if it happens, that's reality.
>
>
> I don't doubt the reality that Tabby's star is dimming, but I do doubt the reality of your theory about the cause of that dimming.
>
>
>> >>> I doubt they are the right experts. They are, for example, not aware of directional waste heat radiation from thermal power satellite designs which would account for the impossibly low observed temperature of what they think are dust clouds.
>>
>>
>>
>> >> I don't know what you mean by "impossibly low observed temperature".
>>
>> > A natural dust cloud, like a comet tail, will be in thermal
>> equilibrium.  At the distance you can determine from the transit time,
>> it is getting a little over 100 W/m^2.  For incoming and outgoing to
>> balance, the cloud should be at 210 deg K.  It measures 65 K.
>
>
> I have no idea where you got those temperature figures. Real dust clouds around stars can NOT be considered to be blackbodies, things are more complicated than that. The amount of radiation a dust cloud gives off that we are able to detect depends on the total amount of mass in the cloud, the size of the dust particles in the cloud, and the metal content of those particles. In the case of Tabby's star all those factors are very imprecisely known, the best determined is the particle size and even then all we can say is they are between 10^-6 and 10^-7 meters across; we know it can't be a solid object because there is more dimming in the blue and ultraviolet than there is in the infrared, but a solid object would dim all wavelengths equally.
>
>
> And of course the temperature of the cloud depends on how far it is from its sun which is also very imprecisely known. The result of all this is that the temperature estimate of that cloud has huge error bars, between about 100 and 1200 Kelvin.
>
>    John K Clark    See what's on my new list at  Extropolis
> heb
>
>
>
>
>