For a captivating exploration of these same ideas in contemporary fiction, try Liu Cixin's The Three Body Problem. As a tip, I enjoyed it much better having not even read the blurb on the back of the book. It spoils events that don't truly unfold until far into the story.
The Three Body Problem is officially the most overrated book on Hacker News. I am trying to understand why. It has no soul, the "science" is garbage, not a single character is memorable, it's way, way too long for what it is.
His vision of the future is bleak in the extreme. His characters are naively constructed and occasionally make incomprehensible choices.
The worst sin is he's unsure whether he wants to write hard sci-fi or just mostly "fi" with a thin veneer of "sci". Occasionally he seems like he wants to stick to solid science with a few extra assumptions (in the best tradition of hard sci-fi); but then he veers off into some cartoonish "science" that's quite jarring. In the end, you get the impression he just tries to brag about how much science he "understands".
In the end I was reading it the way some folks watch a bad movie - to make fun of it.
If you want cosmic scale hard sci-fi, try Stephen Baxter. He can be a bit dry at times, but that's his only fault.
How funny, a friend recommended it to me last week and I just started reading it yesterday. I'm only in the beginning, but I must say I really like it so far.
I was going to say something similar about the Xeelee stories (I also love the The Three Body Problem) but remembered that humanity in those stories only manages to have weaponized neutron stars in a feeble attempt to fight the Xeelee.
I love Centauri Dreams. It's hopeful, makes me feel perspective, and realize how small and primitive we are.
We fret every day about consumption, waste, and energy, and here are some people discussing methods of moving planet-sized objects. It's a kind of optimism that's so rare it almost feels outdated.
> We fret every day about consumption, waste, and energy,...
I'm afraid we have to keep fretting. In the Numberphile video about the number of particles in the Universe (https://youtu.be/lpj0E0a0mlU?t=378), they take an interesting diversion to ask "How long until every particle in the Universe is inside a human being?" In other words, when will we reach the ultimate limit to growth? Well, at the current annualized population growth, it's less than 9000 years! And that scenario involves every human being at that future time floating around naked in the vacuum of space. There is no food to eat, water to drink, nor air to breathe left over.
Practically, this means a couple of things that are less than obvious. First, the best case is that we will reach a point where the growth in volume of the space we occupy will exceed the speed of light. In other words, "long" before 9000 years from now, we will either establish some sort of equilibrium, or we will run up against a hard Malthusian limit. We will absolutely be concerned about "consumption, waste, and energy" in a way that is far more focused than it is now. (The only economic models that are permitted to work are zero-growth models, practically speaking.) Second, to give you an idea of how soon this is coming, the Universe is much larger than 9000 light-years across. That is to say, even if we could manage the resource usage of our 1.011% growth rate optimally, we could never actually fill the Universe in that time frame, as it would take about 15 billion years or so if we were all flinging ourselves outward at very near the speed of light. (n retrospect, these two are restatements of the same idea.)
Finally, and most dismally, the analogous calculation for the Solar System (an infinitely more reasonable calculation to perform) must be abysmally worse and monumentally more urgent. To give you an idea, the current doubling time of human population is something like 60 years. That means, for example, that if we were to anticipate that we'd run out of meaningful room on Earth in 60 years' time, we'd have to start working on our "second home" now, to have it ready. Once it was ready, we'd have to be working on two more. Then four, and so on. Good luck with that!
(Note: After we have consumed the Earth and converted it to habitats, we will have to consume Jupiter in a similar way in about 500 years. This gets out of hand very quickly.)
EDIT: El-oh-el at the few people who's fee-fees were hurt enough by this back-of-the-envelope analysis of growth rates and resource use to downvote it. Keep fighting the good fight, no matter how lonely!
Although this article doesn't make it clear, the underlying concepts (like the light slingshot / "halo drive") are explored in more detail in a previous article:
The problem with firing lasers at a black hole light years away is beam spread. Using the biggest best telescopes we currently have, at our admittedly miserable technology level, the tightest beams we can project on as close a target as the moon are kilometres across. Even if we were to create a mirror as wide as a planet to create a beam, it would be many, many times that wide by the time it reached the binary system. It would be further diverged by the slingshot round the black hole (or neutron star), and diverge further again on it’s way back to the spacecraft. I don't see any way such a system could be made practical.
> Such concepts obviously imply an interstellar civilization capable of reaching the objects in the first place. But once there, the energies to be exploited would be spectacular.
The paper discussed in these articles is not proposing that we puny current Earthlings fire lasers at the closest binary black hole systems. It's exploring the possibility of getting close enough to such a system to make this technique useful.
If you have the technology to reach the nearest binary blackhole ("you just have to pay the one-time fee of the cost to reach the nearest binary black hole system", at 16:12 min in this video: https://youtu.be/rFqL9CkNxXw?t=972 ), you can most likely deal with the mirror/energy harvesting problem as well.
You would have to be fairly close to the black hole in question to do this. A distance of r=3 MG/c² according to Stuckey '93 [1], which is referred to in the paper referenced [2] in the article. Skimming the articles, I can't see any reference to how sensitive to error in aiming this would be.
Interesting concept. Why couldn't we do this with matter?
Instead of firing light off at black holes, why not fire some material around a gravity well and allow it to strike the spacecraft in a way that it A) imparts the inertia it has gathered from whatever body you shot it around and B) is captured to be fired again at a new angle according to your new position?
I know there are a ton of logistics to wade through with this, but it should be at least hypothetically possible. It's the same concept as in the article, save for the fact that we are now firing matter around objects we actually can reach in our lifetimes rather than light around black holes that would take an exceedingly long time to propagate.
You're proposing to fire some material around a planet in such a way that it comes back to a mothership with more momentum than it started with. Now imagine that instead of going "there and back", you find a trajectory that sends it from planet A, to planet B, then back to the mothership. You're coming back even faster now! Why stop at two planets? Find a trajectory so you can do planet A, planet B, planet C, perhaps planet A again... and so on.
Now just delete the mothership from this picture; the 'material' is the spacecraft itself.
This is a gravity assist, and by stacking enough of them you can basically pick up as much extra delta-V as you want (at least until you reach Solar escape velocity).
The main drawback is that it can take decades of flying a convoluted series of gravity assists before you get to where you need to go, and that's all within one system.
(The two-body idea you proposed has the same problem. The mothership has to sit there and wait while the matter flies back and forth on multi-year long orbits. Also now you have to figure out how to 'catch' a hypervelocity projectile...)
So: shoot ourselves, catch the bullet, shoot again?
I think the logistic issues of catching a bullet are probably the limiting factor here. Light at least _wants_ to be absorbed. Matter just wants to go through you.
>Remember the methodology: A spacecraft emits a beam of energy at a black hole that is moving towards it, choosing the angles so that the beam returns to the spacecraft (along the so-called ‘boomerang geodesic’). With the beam making the gravitational flyby rather than the spacecraft, the vehicle can nonetheless exploit the kinetic energy of the black hole for acceleration.
> Light acts the same way, but light cannot return faster than the speed of light. Instead, in gaining momentum from the black hole, the light blueshifts.
Blueshifted light has more energy (and momentum) than it did before the blueshift. If it returns to your spacecraft blueshifted, you can get more energy and momentum out of it than you used in sending it. The change in momentum can be used for propulsion.
So if I shoot a beam of, let's say, a movie or live feed of myself typing this comment around a black hole some 50 light years away precisely enough to have it land back here on earth 100 years in the future, would an observer see back into the past 100 years? ...in the same thread if I observe precisely enough a position near a black hole some N light years away could I see what was happening on the earth N*2 years in the past?
Based on other comments, and my own very limited knowledge of the relevant physics, there's no way to do this from Earth; all of the black holes (and binary block hole systems) are too far away for us to reliably aim a laser beam to slingshot around the black hole as is being described.
But the general form of what you're describing isn't any more outlandish than a time capsule, i.e. 'transmitting information into the future'.
But no, sorry, you can't see the past with the paucity of black holes near the Earth (and ignoring all of the other impediments to such a thing happening).
Yes, this is just a special case of the fact that when you look at something N light years away, you're seeing the object as it was N years ago. You're always seeing the past, never the present! Most of the time in everyday life it's infinitesimally close to the present, though.
A question for a physicist from a layman. All objects in the universe are connected to each other through gravity, no matter how distant. So what happens to the energy or mass of an object (or total energy/mass) in the expanding universe? As space inflates, the distances are greater between objects, so where the excess of gravitational radiation went to? Can that account for the dark energy?
Gravity is not radiation. The expansion of the universe does work against gravity but there are limits. Gravity decreases with distance. So if the universe is expanding fast enough (it is) it will overcome gravity. Imagine setting a bomb off between two asteroids. Use a small bomb and they move apart but eventually drift back. Gravity wins. But use a big enough bomb and they both hit escape velocity. Gravity looses. The objects are moving away from each other fast enough that the force of gravity falls away so fast that it will never turn them around let alone bring them back together.
Dark energy is the concept that while the universe is expanding, gravity wins / everything is at escape velocity, it shouldn't be expanding faster. Dark energy is the fact that the two asteroids separated by the bomb (the big bang) aren't just at escape velocity, something is causing them to accelerate.
You reabsorb the beam which now has even more energy because it's been blue-shifted, which means you can actually charge your batteries as well as accelerate.
[+] [-] eckmLJE|7 years ago|reply
[+] [-] ohaideredevs|7 years ago|reply
[+] [-] Florin_Andrei|7 years ago|reply
His vision of the future is bleak in the extreme. His characters are naively constructed and occasionally make incomprehensible choices.
The worst sin is he's unsure whether he wants to write hard sci-fi or just mostly "fi" with a thin veneer of "sci". Occasionally he seems like he wants to stick to solid science with a few extra assumptions (in the best tradition of hard sci-fi); but then he veers off into some cartoonish "science" that's quite jarring. In the end, you get the impression he just tries to brag about how much science he "understands".
In the end I was reading it the way some folks watch a bad movie - to make fun of it.
If you want cosmic scale hard sci-fi, try Stephen Baxter. He can be a bit dry at times, but that's his only fault.
[+] [-] littlestymaar|7 years ago|reply
[+] [-] arethuza|7 years ago|reply
[+] [-] ethbro|7 years ago|reply
Aka "the last 100 pages, where something actually happens."
[+] [-] kristianp|7 years ago|reply
[+] [-] LastZactionHero|7 years ago|reply
We fret every day about consumption, waste, and energy, and here are some people discussing methods of moving planet-sized objects. It's a kind of optimism that's so rare it almost feels outdated.
[+] [-] wallace_f|7 years ago|reply
Unlike most of what is for sale in this world, which happens to be uninspiring garbage.
[+] [-] theothermkn|7 years ago|reply
I'm afraid we have to keep fretting. In the Numberphile video about the number of particles in the Universe (https://youtu.be/lpj0E0a0mlU?t=378), they take an interesting diversion to ask "How long until every particle in the Universe is inside a human being?" In other words, when will we reach the ultimate limit to growth? Well, at the current annualized population growth, it's less than 9000 years! And that scenario involves every human being at that future time floating around naked in the vacuum of space. There is no food to eat, water to drink, nor air to breathe left over.
Practically, this means a couple of things that are less than obvious. First, the best case is that we will reach a point where the growth in volume of the space we occupy will exceed the speed of light. In other words, "long" before 9000 years from now, we will either establish some sort of equilibrium, or we will run up against a hard Malthusian limit. We will absolutely be concerned about "consumption, waste, and energy" in a way that is far more focused than it is now. (The only economic models that are permitted to work are zero-growth models, practically speaking.) Second, to give you an idea of how soon this is coming, the Universe is much larger than 9000 light-years across. That is to say, even if we could manage the resource usage of our 1.011% growth rate optimally, we could never actually fill the Universe in that time frame, as it would take about 15 billion years or so if we were all flinging ourselves outward at very near the speed of light. (n retrospect, these two are restatements of the same idea.)
Finally, and most dismally, the analogous calculation for the Solar System (an infinitely more reasonable calculation to perform) must be abysmally worse and monumentally more urgent. To give you an idea, the current doubling time of human population is something like 60 years. That means, for example, that if we were to anticipate that we'd run out of meaningful room on Earth in 60 years' time, we'd have to start working on our "second home" now, to have it ready. Once it was ready, we'd have to be working on two more. Then four, and so on. Good luck with that!
(Note: After we have consumed the Earth and converted it to habitats, we will have to consume Jupiter in a similar way in about 500 years. This gets out of hand very quickly.)
EDIT: El-oh-el at the few people who's fee-fees were hurt enough by this back-of-the-envelope analysis of growth rates and resource use to downvote it. Keep fighting the good fight, no matter how lonely!
[+] [-] Footkerchief|7 years ago|reply
https://www.centauri-dreams.org/2019/03/05/investigating-the...
[+] [-] simonh|7 years ago|reply
[+] [-] survivaletc|7 years ago|reply
As it says in that article,
> Such concepts obviously imply an interstellar civilization capable of reaching the objects in the first place. But once there, the energies to be exploited would be spectacular.
The paper discussed in these articles is not proposing that we puny current Earthlings fire lasers at the closest binary black hole systems. It's exploring the possibility of getting close enough to such a system to make this technique useful.
[+] [-] _Microft|7 years ago|reply
[+] [-] kristianp|7 years ago|reply
[1] The Schwarzschild black hole as a gravitational mirror https://sci-hub.se/https://doi.org/10.1119/1.17434 [2] http://coolworlds.astro.columbia.edu/halodrive_preprint.pdf
[+] [-] 781|7 years ago|reply
[+] [-] arisAlexis|7 years ago|reply
[+] [-] Rooster61|7 years ago|reply
Instead of firing light off at black holes, why not fire some material around a gravity well and allow it to strike the spacecraft in a way that it A) imparts the inertia it has gathered from whatever body you shot it around and B) is captured to be fired again at a new angle according to your new position?
I know there are a ton of logistics to wade through with this, but it should be at least hypothetically possible. It's the same concept as in the article, save for the fact that we are now firing matter around objects we actually can reach in our lifetimes rather than light around black holes that would take an exceedingly long time to propagate.
[+] [-] lodi|7 years ago|reply
Now just delete the mothership from this picture; the 'material' is the spacecraft itself.
This is a gravity assist, and by stacking enough of them you can basically pick up as much extra delta-V as you want (at least until you reach Solar escape velocity).
https://en.wikipedia.org/wiki/Interplanetary_Transport_Netwo...
The main drawback is that it can take decades of flying a convoluted series of gravity assists before you get to where you need to go, and that's all within one system.
(The two-body idea you proposed has the same problem. The mothership has to sit there and wait while the matter flies back and forth on multi-year long orbits. Also now you have to figure out how to 'catch' a hypervelocity projectile...)
[+] [-] ajkjk|7 years ago|reply
I think the logistic issues of catching a bullet are probably the limiting factor here. Light at least _wants_ to be absorbed. Matter just wants to go through you.
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] JohnJamesRambo|7 years ago|reply
> Light acts the same way, but light cannot return faster than the speed of light. Instead, in gaining momentum from the black hole, the light blueshifts.
How do you get propulsion from blueshifted light?
[+] [-] AnimalMuppet|7 years ago|reply
[+] [-] mrfusion|7 years ago|reply
Wouldn’t it be a wash?
[+] [-] dmitrygr|7 years ago|reply
Maybe this way?
[+] [-] ConcernedCoder|7 years ago|reply
[+] [-] saagarjha|7 years ago|reply
[+] [-] aeorgnoieang|7 years ago|reply
But the general form of what you're describing isn't any more outlandish than a time capsule, i.e. 'transmitting information into the future'.
But no, sorry, you can't see the past with the paucity of black holes near the Earth (and ignoring all of the other impediments to such a thing happening).
[+] [-] lutorm|7 years ago|reply
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] mudil|7 years ago|reply
[+] [-] sandworm101|7 years ago|reply
Dark energy is the concept that while the universe is expanding, gravity wins / everything is at escape velocity, it shouldn't be expanding faster. Dark energy is the fact that the two asteroids separated by the bomb (the big bang) aren't just at escape velocity, something is causing them to accelerate.
[+] [-] wiml|7 years ago|reply
[+] [-] not_kurt_godel|7 years ago|reply
I don't believe this is correct, as gravitational force/bending of spacetime moves at the speed of light.
[+] [-] edem|7 years ago|reply
[+] [-] JumpCrisscross|7 years ago|reply
Wouldn't fuel need to be expended on the ship to generate the beam? Or is the beam reflected back to the black hole for re-energisation?
[+] [-] MuncleUscles|7 years ago|reply
[+] [-] jacobush|7 years ago|reply
[+] [-] dana321|7 years ago|reply
[+] [-] edem|7 years ago|reply