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How an Advanced Civilization Could Stop Dark Energy From Preventing Their Future Exploration
For the sake of his study, which recently appeared online under the title "Life Versus Dark Energy: How An Advanced Civilization Could Resist the Accelerating Expansion of the Universe", Dr. Dan Hooper considered how civilizations might be able to reverse the process of cosmic expansion. In addition, he suggests ways in which humanity might looks[sic] for signs of such a civilization.
[...] This harvesting, according to Dr. Hooper, would consist of building unconventional Dyson Spheres that would use the energy they collected from stars to propel them towards the center of the species' civilization. High-mass stars are likely to evolve beyond the main sequence before reaching the destination of the central civilization and low-mass stars would not generate enough energy (and therefore acceleration) to avoid falling beyond the horizon.
For these reasons, Dr. Hooper concludes that stars with masses of between 0.2 and 1 Solar Masses will be the most attractive targets for harvesting. In other words, stars that are like our Sun (G-type, or yellow dwarf), orange dwarfs (K-type), and some M-type (red dwarf) stars would all be suitable for a Type III civilization's purposes.
[...] Based on the assumption that such a civilization could travel at 1 – 10% the speed of light, Dr. Hooper estimates that they would be able to harvest stars out to a co-moving radius of approximately 20 to 50 Megaparsecs (about 65.2 million to 163 million light-years). Depending on their age, 1 to 5 billion years, they would be able to harvest stars within a range of 1 to 4 Megaparsecs (3.3 million to 13 million light-years) or up to several tens of Megaparsecs.
In addition to providing a framework for how a sufficiently-advanced civilization could survive cosmic acceleration, Dr. Hooper's paper also provides new possibilities in the search for extra-terrestrial intelligence (SETI). While his study primarily addresses the possibility that such a mega-civilization will emerge in the future (perhaps it will even be our own), he also acknowledges the possibility that one could already exist.
Kardashev scale. One parsec is equivalent to a distance of approximately 3.26156 light years. Corrections made above.
(Score: 4, Informative) by Immerman on Friday June 22 2018, @03:38AM (15 children)
Routinely making an assumption isn't the same as it being a safe assumption. Unless you're just talking about your professional reputation, in which case yes - you're far safer avoiding challenging any widely accepted assumptions.
Ignoring the possibility of FTL does certainly makes things simpler - the existence of FTL would mean that either special relativity or the concept of inviolate causality is flawed, but general relativity offers several possible FTL mechanisms anyway. And we don't really have any evidence to suggest that causality is actually inviolate - it's just one of those things everyone assumes because that's how it seems from our perspective. But then we also used to believe such utterly ridiculous things as matter existing as finite particles that had a definite position and velocity. A completely reasonable assumption from our limited perspective, but also utterly wrong. It proved not to be a remotely safe assumption - except of course when dealing in realms where the difference truly didn't matter.
(Score: 2) by takyon on Friday June 22 2018, @06:42AM (1 child)
If FTL is real, aliens are watching you in the bathroom with a cloaked phase-shifted infrared tracking nanodrone. This is during the times in which they are not probing your orifices. They have command and control ships stationed beyond the Kuiper belt and have enacted zoo containment protocol for the entire solar system. They already gave the Golden Record a listen, put it back, and rated it a 7.2/12.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 1) by tftp on Friday June 22 2018, @04:30PM
(Score: 1) by khallow on Friday June 22 2018, @11:57AM (12 children)
What we do have is an enormous lack of evidence for FTL. That's the wet blanket for your speculation.
(Score: 2) by Immerman on Friday June 22 2018, @01:57PM (10 children)
Pretty much all the solutions suggested within GR would require conscious intent (and incredible technology) to create, so we would only expect to find them in the presence of an intelligent species far more technologically advanced than ourselves. And thus far not one of the advanced alien races we've discovered has lacked FTL - so that's hardly a good argument.
Moreover - exactly what evidence would you expect to see for FTL being used at interstellar, or even intergalactic distances away from us?
Note that I am in fact moderately confident that FTL is impossible, but we have exactly zero evidence to support that position, and a firm theoretical basis to assume it *is* possible, so calling its impossibility a "safe assumption" is greatly overstating things.
(Score: 2) by VLM on Friday June 22 2018, @02:05PM (8 children)
Note that your debate strategy is straying into territory near "... and that's why we use classical astrology to design our space probe orbits". Some things, like astrology being real, can't be wished into existence without a whole lot of other things becoming bothersome.
FTL is usually synonymous with magic, magic in the sense of Tolkien anyway, so there's that minefield too. Too much magic and you've got no narrative in general "It was a dark and stormy night .. then the wizard waved his wand and all was right with the world, The End" now wheres the participation trophy I'm entitled to? What you say my story doesn't meet the modern requirements of politically correct sci fi? Well ... I'll make the wizard a gay minority trans wizard,THEN the industry awards can roll in.
(Score: 2) by Immerman on Friday June 22 2018, @02:15PM (7 children)
FTL in storytelling is certainly plot-advancing "magic". However, in reality it would be essentially invisible from a distance, and is firmly supported by one of the most well-tested and widely supported theories in our play-book (GR). Denying its potential existence amounts to assuming that either GR is flawed, or other physics we currently have no inkling of would prevent it from working. And our evidence against it basically amounts to "but that would make time travel possible"
(Score: 2) by maxwell demon on Friday June 22 2018, @03:11PM (6 children)
First: As far as I know, all known solutions to GR that would enable FTL involve matter or fields with negative energy density. Not only have we never found any such matter or fields, there are also good theoretical reasons to assume the non-existence of those.
Second: We already know that GR almost certainly won't be the last word, as it is incompatible with quantum mechanics, and all attempts to unify both so far have implied deviations from GR.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by Immerman on Friday June 22 2018, @03:54PM (5 children)
I want to say we have actually observed very low (near zero) negative energy densities, but I can't think of where I've heard it, so I won't make any claim of validity. Otherwise, yes, that would seem to be a stumbling block. Though great strides have been made in reducing the required negative energy densities by several orders of magnitude, and finding a way to eliminate them entirely isn't beyond the scope of possibility.
Secondly - the conflict with QM could indicate a flaw in either theory (or both), and we're increasingly certain that we're missing something important in QM for completely unrelated reasons. Whereas the only major problem we've found with GR is that is that it conflicts badly with QM on some key (currently unmeasurable) predictions.
(Score: 2) by ElizabethGreene on Friday June 22 2018, @04:08PM (4 children)
"I want to say we have actually observed very low (near zero) negative energy densities."
Yes, we have observed these in the field of optics, in metamaterials IIRC.
(Score: 2) by Immerman on Friday June 22 2018, @05:11PM (3 children)
That's certainly one of the more recent examples, unfortunately like so many things in metamaterial science, there's seems to be a lot of "behavior within a context" discussion going on - a relatively negative energy density stored within a physical substrate (an immense positive energy density concentration) isn't necessarily reflective that an actual absolute negative energy density (relative to empty space) is possible.
If you can think of any examples of possibly absolute negative energy densities I'd love to hear it though.
(Score: 2) by ElizabethGreene on Friday June 22 2018, @05:37PM (2 children)
>> a relatively negative energy density stored within a physical substrate
(I am not an expert on this topic.)
For an Alcubierre drive I don't know if that's a show stopper or not. You do need both the positive and negative energy density, a massive metamaterial structure might be the ticket. If you can achieve the desired effect with a low enough frequency (wavelength in tens of meters) it's not inconceivable to make the spacecraft in or part of the resonator.
It would be cool to see a 10 Megahertz multi-gigawatt split-ring resonator (from a safe distance)(assuming it didn't rattle the fillings out of your head)(and give your cancer cancer).
(Score: 2) by Immerman on Friday June 22 2018, @05:57PM (1 child)
I'm no expert either, and while I understand the basic geometries involved, I have only the vaguest concept of why negative energies are absolutely required to create them.
However, if negative energies are necessary, then I strongly suspect that any substantial quantity of matter, with it's incredible positive energy density, in those regions that require a negative energy density would render them unsuitable. Moreover, you're talking about regions of space that are folded in on themselves with such extreme curvature that even subatomic particles would be torn apart by the immense tidal forces - I doubt any physical metamaterials could survive (though perhaps some sort of "metaenergy" structure could.
Another potential problem is that the entire metastructure would have to exist *within* the "warp field", since anything outside the field will be left far behind as soon as you start moving FTL.
(Score: 2) by VLM on Friday June 22 2018, @07:22PM
There are other LARP issues with FTL such that traditionally its inside a ship that can control it, but its sometimes pretty tricky to control a field from inside it. Think of how easy it is to charge two capacitor plates using all kinds of gadgetry from the outside of the plates, and its a bit trickier to charge two plates from between two plates without generating an even stronger tidal field in between the plates than exists outside it. Of course "FTL field" might be as simple as manipulating a magnetic field, although I suspect it would not.
My guess is a FTL thingie would be more stargate like, a huge and energetically expensive space station, where small stuff goes in a big object and magically disappears, reappearing perhaps FTL hopefully a really long distance away.
Something often mentioned is how poor of a job solar cells do further away than earth orbit. Yet, if you can keep them cool (which can be tricky) then solar cells within the orbit of Mercury or something really pump out the watts.
If I were doing realistic hard sci fi I'd put my theoretical solar powered star gate around Mercury.
Also some of those solar systems with extremely large planets in extremely close to their star orbits would probably look absolutely delicious as a resource provider for a solar powered star gate civilization.
Now the point of this ramble is if I were doing SETI stuff, assuming solar powered star gates exist, THEN I'd be pointing my SETI antenna at those recently discovered planetary systems with huge planets in close orbit to stars.
Assuming of course we're not all being fooled by the oldest "Warp drive" trick in the sci fi book, that being close to grav fields screws up warp travel.
Also I would assume that any research on this is classified. Something that can go faster than light outside normal space ... is not just faster than light, but is outside normal space and that would make it awesome (well, from some perspectives) for everything from logistics to weapons of mass destruction to paratrooper delivery service.
So mixing this all up, we can "prove" grav fields do or do not F up solar powered star gates by pointing SETI antennas at likely exo species Space Marine base locations to determine if those otherwise ideal locations are, or are not, swarming with alien space marines. Assuming we can identify space marines from this distance. Extrapolating from my experience in the Army with Marines, admittedly a long time ago, we would need to detect excessive quantities of pr0n liquor and hooah.
(Score: 1) by khallow on Saturday June 23 2018, @02:11AM
Or particles slamming into each other at high energies. That explores a large portion of the "solutions" you speak of.
Widespread Dyson swarms, for example.
Absence of evidence is indeed evidence of absence.
(Score: 2) by Immerman on Friday June 22 2018, @02:06PM
As a follow-up, wormholes are probably one of the few avenues of FTL that just might occur naturally (if they can exist at all of course). And probably also one of the most dramatic. Now, you tell me exactly what sort of evidence you would expect to see of their existence from a distance of 1000 light years? Either end would essentially look like a (probably very low mass) black hole without an event horizon - so utterly invisible, without even the incidental radiation from the annihilation of infalling matter. You wouldn't be able to see anything passing through it unless it was ejecta from a supernova - and even that would be iffy.