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Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 10:51 am UTC
by Fungo4
When I peeked ahead at the end, my brain didn't parse the rest of the sentence and interpreted the final ultra-massive candidate as "SPACE HEAVY".

Can we... Can we just call dark matter Space Heavy from now on?

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 11:17 am UTC
by cellocgw
speising wrote:
sotanaht wrote:
Pfhorrest wrote:Dyson spheres would emit black body radiation of the average temperature of themselves and their contents, and so glow detectably and not be dark.

So we think. Anyone advanced enough to actually build a Dyson Sphere though might have technology that effectively "cloaks" them

if you can defeat thermodynamics, you don't need no puny Dyson sphere.


You don't have to defeat StatisticalMechanics ("thermodynamics is sooooo 1920s), just go with it. The external surface of the Dyson sphere is perfectly reflecting. This means its emissivity is zero. It gives off zero photons. Now, you might say (and I can hear it before you read this), "But then it would be shiny and we'd see it." But first: it's a sphere, so the reflective cross-section (see "Radar Cross-Section" in your choice of reference sources) is relatively small. And space is really big [HGTTG quote redacted]. The teeny glint from the sphere doesn't register on our sensors.

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 11:55 am UTC
by Rossegacebes
Dark matter is not dark at all. It's transparent. It's the most transparent matter in the universe.

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 1:54 pm UTC
by DanD
speising wrote:
sotanaht wrote:
Pfhorrest wrote:Dyson spheres would emit black body radiation of the average temperature of themselves and their contents, and so glow detectably and not be dark.

So we think. Anyone advanced enough to actually build a Dyson Sphere though might have technology that effectively "cloaks" them

if you can defeat thermodynamics, you don't need no puny Dyson sphere.


But you don't need to defeat thermodynamics. After all, you have a ton of energy for refrigeration and such. You just need to choose to radiate all your waste heat in a direction that does not point at us. If the average dyson "sphere" is only a 99% complete toroid, and waste heat is radiated at the poles, the likelihood of that head being pointed at us in an observable direction is on the low end. (Yes, I know this is not the likely explanation, but it is possible).

Also, to add to the list above, dark matter is mostly socks that disappeared out of the wash.

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 3:02 pm UTC
by Quizatzhaderac
jgh wrote:And as we perceive dips in space-time as a gravity well, and declare that a gravity well is due to mass pushing down the rubber sheet, we see a dip in the rubber sheet with no mass and declare that there must be some invisible mass there instead.
The wiser response to perceiving dips in space-time would clearly be to go get some chips in space-time.

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 4:42 pm UTC
by SuicideJunkie
Unfortunately there's almost no air in the bag to protect them, and someone went and broke all the space-time chips into 10-35m fragments.

Re: 2035: "Dark Matter Candidates"

Posted: Tue Aug 21, 2018 9:26 pm UTC
by Archgeek
SuicideJunkie wrote:Unfortunately there's almost no air in the bag to protect them, and someone went and broke all the space-time chips into 10-35m fragments.

Mmmm, Planck chips.

Re: 2035: "Dark Matter Candidates"

Posted: Wed Aug 22, 2018 10:04 pm UTC
by Imposter
Rossegacebes wrote:Dark matter is not dark at all. It's transparent. It's the most transparent matter in the universe.


Hmmph! Anyone could see through that argument...

Re: 2035: "Dark Matter Candidates"

Posted: Wed Aug 22, 2018 11:32 pm UTC
by gmalivuk
keldor wrote:
You can run a simple N-body simulation on your own computer to verify this.

If your frictionless collisionless n-body simulation results in all the bodies clumping together at the barycenter, it's not a very good simulation and you should probably double check your programming.

DanD wrote:
speising wrote:
sotanaht wrote:
Pfhorrest wrote:Dyson spheres would emit black body radiation of the average temperature of themselves and their contents, and so glow detectably and not be dark.

So we think. Anyone advanced enough to actually build a Dyson Sphere though might have technology that effectively "cloaks" them

if you can defeat thermodynamics, you don't need no puny Dyson sphere.


But you don't need to defeat thermodynamics. After all, you have a ton of energy for refrigeration and such.

No, you don't, unless you're letting the energy out through a gradient to make it do work.

cellocgw wrote:
The external surface of the Dyson sphere is perfectly reflecting.

Sure, and if I had an infinitely rigid stick I could use it to communicate instantaneously.

Positing physically impossible materials as a way around physical laws doesn't actually work.

Re: 2035: "Dark Matter Candidates"

Posted: Thu Aug 23, 2018 1:40 pm UTC
by DanD
gmalivuk wrote:
DanD wrote:
But you don't need to defeat thermodynamics. After all, you have a ton of energy for refrigeration and such.

No, you don't, unless you're letting the energy out through a gradient to make it do work.


Highly efficient mirror over the majority of wavelengths on the interior surface. This essentially becomes a giant solar concentrator. Your heat engine is located at the single outlet, with directional waste heat radiation. Some of the energy from that is used to cool the remaining outer surface of your sphere to local ambient. Net energy is still generated, radiation is in a limited cone away from the heat engine.

Re: 2035: "Dark Matter Candidates"

Posted: Sun Aug 26, 2018 4:09 am UTC
by Cougar Allen
Why? Supposing it's possible to cool the outer surfaces of all those Dyson spheres to near absolute zero, why would they? Just to fool Earthlings into thinking there's some kind of nonbaryonic dark matter?

I also doubt the "space is big" argument. If there are enough stars hidden inside Dyson spheres to account for the missing mass, is space really big enough to hide all those directional heat jets?

Re: 2035: "Dark Matter Candidates"

Posted: Sun Aug 26, 2018 4:13 pm UTC
by rmsgrey
Cougar Allen wrote:Why? Supposing it's possible to cool the outer surfaces of all those Dyson spheres to near absolute zero, why would they? Just to fool Earthlings into thinking there's some kind of nonbaryonic dark matter?

I also doubt the "space is big" argument. If there are enough stars hidden inside Dyson spheres to account for the missing mass, is space really big enough to hide all those directional heat jets?


The obvious comparison is pulsars - which there are definitely enough of that those directional radiation beams don't all miss Earth. On the other hand, it's at least semi-plausible that the cold spheres' jets are aimed, particularly if they're being cooled for concealment purposes - if there's a culture out there capable of constructing cold Dyson spheres, then there's at least one culture out there capable of destroying any Dyson spheres they can find... Of course, anyone whose records pre-date the construction of a sphere can still find it just by looking for missing stars.

Re: 2035: "Dark Matter Candidates"

Posted: Sun Aug 26, 2018 5:23 pm UTC
by Pfhorrest
That’s why you fly your concealed Dyson sphere somewhere else than where it was built.

By that tech level “star ship” means a ship that IS a star.

Re: 2035: "Dark Matter Candidates"

Posted: Sun Aug 26, 2018 5:57 pm UTC
by ijuin
In that case, the jet is a Shkadov thruster, forming a major component of the sphere’s propulsion.

As far as thermal camouflage goes, anybody advanced enough to be a threat to a Kardashev type 2.0 or higher civilization would be able to detect and track Dyson Spheres by their gravitation rather than by their electromagnetic radiation.

Re: 2035: "Dark Matter Candidates"

Posted: Mon Aug 27, 2018 6:06 pm UTC
by SuicideJunkie
Instead of trying to hide it as a cold blackbody, why not light up the surface and look like a cooler star, pocketing the energy difference?
Mosey on over to where you want to be inconspicuously, and use "solar flares" to slightly twerk your approach so as to "naturally" use other stars for gravity assists.

Real spies blend in with the neighbours, rather than trying to be invisible Hollywood Ninjas after all.

Re: 2035: "Dark Matter Candidates"

Posted: Mon Aug 27, 2018 9:57 pm UTC
by Old Bruce
Fungo4 wrote:When I peeked ahead at the end, my brain didn't parse the rest of the sentence and interpreted the final ultra-massive candidate as "SPACE HEAVY".

Can we... Can we just call dark matter Space Heavy from now on?

After a great deal of thought and much debate I will join you in calling dark matter space heavy.