Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel
theconversation.com
theconversation.com
He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable. Now this isn't to say there isn't one that's say, 600 million light years away that built their first Dyson sphere 500 million years ago although, in practice, this doesn't really change the probabilities that much.
If there's FTL then that billion light year practical limit really goes out the window as you can effectively get anywhere in the universe, making the volume of absence be many, many times the size of the observable universe.
I'm not sure why the author is talking about gravity ripping you apart in a black hole. It Is Known [tm] that larger black holes have pretty gentle event horizons.
I'm not sure why it matters that a black hole would be spinning. You can pretty much assume every significant mass in the universe is spinning to some degree (a state of zero spin being highly unlikely over even small amounts of time).
The author talks about the inner event horizon and I guess that's the point. But all of that is highly theoretical. Nothing is known about the inner workings of a black hole. It's all highly theoretical and beyond the ability of general relativity to describe. No other theory has been able to adequately explain or describe gravity let alone extreme gravity so your view on what's within the event horizon probably depends on which unproven theory (eg string theory) you subscribe to.
So this is speculation based on speculation.
Even if we ignore the ponies and rainbows of wormhole travel, if you want to travel to a plain black hole to use the magic teleporter, the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY. If you buy into the article's assertion that you won't get burned or spaghettified on your way to becoming a nucleon paste, and you want a heavier BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.
Anyway, to travel between the teleporter and Earth, we're talking most of the resources of a planet to accelerate a mass to substantial fractions of c. Then you've got thousands of years of collisions, radiation, and maybe (assumption?) cultural and biological challenges of living in space for aeons, plus needing another planet's worth of resources to slow down at the destination. All this makes it hard enough even to get a dozen LY to our nearest start system.
My opinion is we're in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.
If we have fusion power, durable permanent space habitats, and the technology to harvest materials from asteroids, then traveling to the next star system doesn't seem so far-fetched anymore. If we could just reach 0.1c, we could make it to Alpha Centauri in less than 50 years. Once we make it there, if we're already comfortable living in space, we don't even need to worry about terraforming or anything lengthy and complicated like that, we can just harvest asteroids and build more space stations and ships.
Not a physicist, but I see Project Orion could have reached 0.33% of the speed of light. Would it be realistic to extend that design to accelerate to 0.1c?
Bear in mind that we were certain colonizing Mars was just around the corner after landing on the Moon... about 60 years ago. In the interim, we lost the capability to land anything but probes beyond low earth orbit and are basically starting from scratch with private enterprise.
Not only is technological progress not always consistent, but it takes more time and effort to recover from regressions the further along the curve of advancement you happen to be. By which time, goals and priorities may have changed significantly to alter the trajectory of that progress.
So I would be wary of extrapolations that make it seem as if progress into space is like climbing a ladder. It seems more like building a Jenga tower as you climb it.
It's interesting to consider that maybe life on earth is in fact a colonization effort from long ago. Sending probes with the base ingredients for life across the universe millions of years ago might've been a survival strategy. It feels meaningless without information to go along with it, but it's likely that information has either been lost, forgotten, or attributed to early humans instead of something Out There.
Not to mention all the fuel you'd need to decelerate so you can actually stop at your destination.
We are already capable of that now. The issues are politics and economics and not science/engineering.
If I'm not wrong the USA spent like $1T on building a fighter plane, and something like double digits trillion dollars and ongoing on wars since the past 20 years alone.
You can mine asteroids for a part of that kind of budget already.
Going down gravity wells of planets makes no sense, space colonies are the way forward, and there is no shortage of resources in space for that.
The nearest known ones, that is. They were detected due to their gravitational effect on binary companions we could more easily detect. By that token, it is quite possible there are nearer ones - it's just that detecting them directly if they don't have a binary companion is tough.
I mean, looking at our own planet, it seems this might be extremely unlikely.
To the best of my knowledge, another Planet Earth could possibly be within a few hundred ly of us(0.000000001 of known universe), and we'd have no idea(1)..?
1-https://www.centauri-dreams.org/2012/05/31/is-our-civilizati...
[1] Section V of this paper https://arxiv.org/abs/0908.1803
Let us hope so.
If you're going to pick a fictional hyperspace "framework," there are many to choose from, all of which are equally nonsensical.
How do we know an advanced technology would absolutely use Dyson spheres?
I'm not asking to challenge but in serious inquiry. Off the top of my head it just seems a highly advanced civilization might be able to come up with something completely different to meet their energy needs.
This depends on what question you're trying to answer.
The Fermi Paradox is a good one because you don't need to ask "would a civilization always use Dyson spheres?" It takes just one to use them within a billion years to be a sufficient counterexample. Would they be universally used? Who knows?
Dyson spheres are such an attractive idea because there's no new physics required here (like negative mass for wormholes and warp drives). It's largely just an engineering problem. Now it does require a fairly economical method of getting off-world but all of this seems relatively likely within the next 100-200 years.
So it's (relatively) low tech and attractive in terms of providing living area for unit mass (many, many orders of magnitudes better than living on planets).
It's worth noting that you don't even need nuclear fusion to make this all work (although that makes it much easier) and it's not a given that we'll have practical nuclear fusion.
If you don't have nuclear fusion, what is your energy source? The alternatives other than harnessing solar output are much, much higher technologies like using black holes (which is also theorized about as a starship drive).
To me it seems that if you take an infinite number of civilisations, you should find a lot of rings and barely any full spheres. But a ring is a lot harder to detect: if it blocks the star from our point of view it's as obvious as a dyson sphere, but in most orientations it would be seen as a very thin band that radiates much less energy than the parent star, making it basically impossible to detect with current technology (none of our methods of finding exoplanets seems applicable, and emissions would be too low to be seen directly)
What you're talking about I think is a ringworld, popularized by Larry Niven's "Ringworld" series. They have the same problem a Dyson shell does: the centrifugal force would tear the ring apart and there's no known material that could handle that.
A Dyson swarm has basically all the advantages of living area a shell or ring does with none of the material problems. It can also be built incrementally, one habitat at a time. And that too is important.
This is why a Dyson swarm is seen by many futurists as near inevitable:
- Can be built out of modern materials like stainless steel
- Can be built incrementally, one habitat at a time
- Is orders of magnitude more efficient in terms of living area per unit mass than planets
- It avoids large gravity wells, which are a problem for getting off planets
- It can take advantage of the full energy output of a star
Maybe multiple rings would form for political reasons, but that just makes the individual rings proportionally thinner.
Whenever an object would intersect the sphere, the nearest heliostats alter the angle of their mirrors/sails to drift away and make a hole. Then they drift back to close it after it passes.
There's nothing to say that they can't also have an orbital velocity component, as it takes quite a lot of delta-v to decelerate from a near-circular solar orbit, and orbital velocity can make up for lack of sail area.
Not if our brightest minds are trying to make people click more ads.
I think I finally know the answer to the Fermi Paradox.
Is this true? The mass required would generate forces that would rip apart any materials we've encountered. A Dyson belt could just be in some unstable sort of orbit, but a Dyson sphere has to be strong enough to hold itself in shape.
A Dyson sphere/swarm is simple a sufficient cloud of habitats orbiting the star as to essentially block out the vast majority of its light, kind of like how droplets of water block light in a fog.
I dunno where your remark about salt comes from either; a lot of salt intended for consumption is dug up from the ground (salt mines).
FTL makes that 100%, from beyond out cosmic horizons, even if it turns out that FTL isn’t automatically also a time machine like we currently think it is.
Pocket universes might help? I don’t know though, I’m saying that only because I’ve not seen them ruled out.
Unless you can violate the laws of thermodynamics.
We always imagine they have very advanced physics and engineering, to do things like take apart planets to build mega-structures and things like that, but usually don't think about their other sciences.
My guess is that by the time they have gotten that far in physics, they have also gotten way ahead of us in biology. They'll have wiped out disease and illness, stopped aging, and only die by choice or accident. They'll have figured out geology and ecology and climatology and psychology.
I suspect that the final steady state for most civilizations that don't end up wiping themselves out by doing something stupid is a relatively small (by our standards) population of essentially immortal beings, living on a world they have restored to a largely pre-civilization state, using less energy by far that we are using but using it way more efficiently.
Also, a huge laser can certainly direct energy in a direction that nobody will notice. Unfortunately, creating the laser beam also creates waste heat, and that waste heat can be seen. Even collecting waste heat generates waste heat that you cannot collect.
On the other hand, if you want a huge laser for some other purpose (such as vaporizing distant planets), then a Dyson Sphere is the ideal way to create one.
https://groups.google.com/forum/#!msg/sci.space.tech/uh5iB9X...
Actually, we've never seen one so we have no idea how one might be engineered! It could for example be a "fog" of worlds that extends out past several local AU and to us would look nothing more like a dust cloud obscuring their local star. There wouldn't be a telltale signal of a Dyson Sphere, just another star with a big dust cloud.
Imagine a civilization like this, those closer to the star get more power literally, and those on the outskirts and in the shadows of the other worlds become dependent on the more inner worlds to re-radiate their absorbed energy, or to condense and lase the energy outwards to the shadow worlds...at some cost that limitless free energy can't pay for.
Beyond some distance the worlds become so cold that the inhabitants freeze to death and exile of your entire world at the whims of the inners becomes a real punishment. Dead worlds are recycled for mass for the growing population of the inners, or repurposed for other things.
There are billions of such worlds. Perhaps they are customarily shaped as small ringworlds and rotate in a complex manner to produce gravity and a daynight cycle. Dead or frozen worlds may have a reflective sail hoisted along the inner opening and expeditionary generation ships are sent out to nearby stars powered by lasers collected from hundreds of inner worlds.
Successful colonies may start to immediate transform the mass of nearby planetary systems into new "dust" clouds rather than settle on the planetary surfaces. Many adjacent Dyson spheres may look to us like just interstellar gases between several stars containing an unusual amount of organic molecules but could be the exchange of trillions of generation ships moving mass and energy back and forth between stars.
Such a civilization could eventually become nomadic in a way, moving from star to star as they burn out, leaving behind frozen husks of trillions of dead ringworlds.
Unless maybe it's storing everything on blockchain.
But the article isn't about what happens at the event horizon. It's about what happens at the singularity, well inside of the event horizon for astrophysical black holes.
Or that making a dyson sphere is harder than FTL, or it isn't economically viable to build one. There's no reason to assume a Dyson sphere would be a logical step after achieving FTL
I would modify your sentence to say that the speed of light is a hard limit through space. Space on the other hand does not seem to have that limitation [1]
I’m not claiming that the warp drive is around the corner, I’m just saying: we do not yet know enough to rule it out.
A bit unrelated, my pet theory is that a dwindling of some quantity creates the things we're measuring as acceleration. My naive intuition is that celestial bodies aren't flying away from each other accelerated by some unseen energy so much as getting smaller. If two things shrink in place, the distance between them grows.
Maybe there's some obvious reason why that couldn't be the case, i'd be interested to know!
(This leads to another problem: why don’t the photons shrink too?)
The metric expansion of space appears to be an extremely weak, small effect. It just adds up to something measurable in the vast gulfs between galaxies.
Furthermore the amount of acceleration away from us is proportional to the distance from us (farther things are accelerating away faster). The shrinking hypothesis only makes sense of that data if it posits that we are the center of the universe.
(I’m really tired right now, forgive me if this is a dumb question)
If a civilization has the intelligence and foresight to build a Dyson sphere, how much more intelligence and foresight does it need to hide one?
For example, consider a perfectly insulating black box with small hole. Observers on the opposite side from the hole will not observe any radiation from the interior of the box.
I don't think there's any physical limit on collimating the outgoing radiation to hide from everyone outside a narrow beam. It's "just an engineering problem".
The lower the temperature, the longer the wavelength and the wider the beam (given fixed emitter geometry). So there's a tradeoff between hiding your Dyson sphere vs extracting the most energy from the source.
Unless that heat energy itself is also caught and used.
I suspect that civilisations that make it to the Dyson swarm stage are on average a little biased towards environmentalism in order to survive past their terrestrial industrial stage.
Doesn't make sense to put a giant target on yourself until you can discount the dark forest hypothesis either, especially not when you've just beaten incredible odds to become a near-immortal truly space-faring civilisation.
I personally find the dark forest interesting not because I think it is likely but because even giving it a very small probability of being true would be enough for near immortal high tech civilisations to move very cautiously.
what credentials does he have?
> Put me firmly in the camp that believes the speed of light is a hard limit on the universe
the speed of light isn't a limit in the sense that nothing can be greater than it. it is a crossover point that can't be crossed over for things above or below it to the other side.
> I'm not sure why it matters that a black hole would be spinning.
black holes that spin are much different than non-spinning holes and have more complicated dynamics. if they are spinning, they are dragging space-time along with them. see this paper that shows some actual visuals of what a spinning black hole might look like and what it does to the light around it.
Hell, we're assuming that Dyson spheres are even possible with such a conjecture. I'm not convinced they are (not without materials that border if not cross outright into magic). It's also not certain if they're necessary to build to sustain any size of spacefaring civilization (artificial nuclear fusion would kinda defeat the point).
A Dyson swarm (the original Dyson sphere) is a cloud of independently orbiting habitats/bodies/structures.
Even if a civilization's capable of building that many stations to surround a star in a deliberate sort of Kessler syndrome, it ain't clear that a civilization would ever need to do so.
I guess the human civilization doesn't count as "sentient" because we don't have a Dyson sphere yet...
Also how "unmissable" is a dyson sphere? Do we have the means to survey every single star within one billion light year radius? Hell, we know neutron stars are real, same for blackholes, but does that mean we observed every single one of them and didn't miss a single one?
- Secret Aliens [1]
- Hidden Aliens [2]
Basically you can't hide from a K2 civilization in your same galaxy so there's really no point in trying.
Because of frame dragging.
It is entirely possible that advanced sentient civilizations have realized that there is such a thing as 'enough technology', learned enough to permanently liberate themselves from basic needs, and found other kinds of fulfillment and amusement.
Since we've been unable to detect the telltale signatures of such a megastructure, it either means that none of the civilizations within range have gone this route or there are none. Given what we know about the benefits of a Dyson swarm and how relatively low-tech it is, the idea that no one has gone that route becomes increasingly unlikely with the more civilizations there are.
I think there's a real question of whether anyone would actually want one. The sun's total power output per person on earth is 5.5e+16W. That's 3000 times total human energy usage, _per person_. Even if you assume a system population in the trillions, that's still a pointlessly large amount of energy per capita (and again, current population trends don't support that, and we may reasonably assume that most Dyson sphere builders will figure out birth control).
Most possible hypothetical uses for them seem to be things like converting all the mass in a solar system into a computer or similar, but again there's a real question of whether there's any market for that.
I'm also not convinced we could necessarily detect one. A super-high-tech magic one would capture most of the available energy, leaving a largely invisible thing with mass, which sounds quite a lot like a neutron star. And if you had a lower-tech one that leaked most of the energy, well, that might look distinctive, but if you're throwing most of the energy away you probably don't need a complete Dyson sphere.
And in any case, organised searches for Dyson spheres are pretty new, and are small efforts. We might have the data to support them right now, it's just that no-one's noticed yet...
In 2019, we've solved the food problem, at least in the developed world, mostly. If you need food in a hurry you don't need a magic table - you need a diner, or a restaurant, or a fast food place, or some wrapped sandwiches.
Dyson Spheres are a Steampunk version of the fairy tale, a relic of an energy-poor and slightly overcrowded culture. OMG all that energy! All that space! You could use it for computing! Or... something else!
In reality by the time we got to the point where building a Dyson Swarm was a realistic possibility, we'd most likely have moved far beyond needing one, or having any interest in needing one.
It’s certainly easier than capturing a star’s total output!
When you say on algebraic solution exists, that doesn’t mean no solution exists?
How easy are they to miss?
The only thing such a trip could be used for is to see the end of the universe. As every object getting near the event horizon experiences the time slowing down compared with the outside a person on board a ship could probably see stars going out etc as billions of years passed. The time slows down so much one could never "pass through" a black hole as reaching the singularity would require the time to stop. So as the ship approaches the singularity the black hole would get smaller and smaller as it evaporated during those billions of years until it eventually disappeared. However, a ship wouldn't survive the disappearance as when the black hole is getting smaller the tidal forces increase eventually ripping the ship to shreds.
> The fate of an astronaut who falls into a black hole depends not just on the latter’s properties (such as the intrinsic parameters, i.e., the mass and spin angular momentum, and the external perturbation fields) but also on the former’s worldline. ... However, astronauts with positive energy and low angular momentum (including counterrotating ones) arrive at the outgoing leg of the black hole’s inner horizon ("outgoing inner horizon", henceforth, OIH).
> The properties of spacetime at the OIH have been proposed to be those of an effective shock wave singularity. Specifically, it was proposed in [2] that daughters of a family of free-falling astronauts whose geodesics intersect with the OIH, and who are separated only by time translations (and labeled by the advanced time values at which they cross the event horizon (EH) [symbols]) experience a change of order unity in typical metric perturbations, and that these changes occur over a lapse of proper time that drops like [symbols] with increasing [symbols], where [symbols] is the surface gravity of the OIH. Sufficiently late-falling daughters therefore experience an effective shock wave singularity, the Marolf-Ori singularity ("outflying singularity").
I have no clue what that means. Anyone?
0) Burko and Khanna (2019) The Marolf-Ori singularity inside fast spinning black holes, https://arxiv.org/pdf/1901.03413.pdf
As for the time distortion: Yes, you see the end of the universe regardless of the black hole size. Yet, your clock continues to tick along just fine and you still fall in. Per our current understanding of physics, you get to see everything in the universe blue shift to infinity. In smaller black holes, since the Lorenz transform is so curved, all of space gets warped to directly in front of you, all the incoming radiation gets blue shifted to infinity. Essentially, every quark and electron gets blasted by pure radiation of infinitely small frequency. Think standing in front of a train in a dark tunnel with a bright light on the front. For larger black holes the Lorenz transform is less curved, so the cosmic Train Collision happens closer to the event horizon; but you still get blasted. (Note: I don't actually know if this is due to the Lorenz transform, but the best way to get a right answer on the internet is to give out the wrong answer :) )
If you are thinking that none of this makes sense and are saying "yes, but what about..." then you are thinking correctly. Black holes are very poorly understood and we're just at the beginning of trying to figure them out.
One very important ratio to remember is: 5 : 20 : 75 .
In the universe, everything that you are made of, all the matter, is only 5% of our known universe and most of that matter is locked up in stars. We're actually only a very small fraction of the universe.
Dark matter is ~20% of the stuff in the universe. About all we currently know about dark matter is that it falls down. Does it have a temperature? No clue. Does it interact with matter? More data is needed. Does it interact with itself? We haven't any idea, would you like more tea? Dark matter is ~4x the amount of stuff we are, and we haven't a clue what it does.
That said, Dark Energy is ~75% of the stuff in the universe and it ... falls up? Honestly, we're completely lost. We have no idea how it works, we just know the universe is flying away from itself and it's gas pedal is firmly glued to the floor. We haven't any remotely serious idea how to probe it outside of looking at galaxies and hoping we get lucky and see something funny.
So, before we get all high and mighty and try to think we have any idea what is going on in a black hole, we've got to figure out what the other 95% of the universe is doing, as it's very likely to have really important things going on. Hyperspace? I mean, sure, why not? It's just about as strange a thing as Dark Energy is.
So, I think the consensus is that: More research funding is needed.
Also, it's pretty much certain that wherever there appears infinity in physical model you can be sure it's a limitation of the model, not actual physics of the object. We do not observe infiities, even though pretty much every of our models has some.
Those would be two basic hunches against stuffing matter into infinity without consequences. Some kind of exit seems natural, the question is how destructive it would be.
Er, no. Travelling at c, it would take 4.5 years to get to our nearest star. The nearest (known) black hole is V616, 3,000 years of travel away if travelling @ c.
The nearest star is a little over 4 light years away, not 100.
v(t) = at (velocity at time t)
∫v(t)dt = 0.5 a t^2 (distance traveled at time t)
0.5 a t^2 = 0.5 d ==> t = sqrt(d/a) (time to halfway point)
Plugging in d=4.5ly and a=9.81m/s yields 2.07 years to the halfway point, so that's just over 4 years total travel time at 1G.
You'd reach 95% of the speed of light, which would take 4 gigatons of TNT[1] (and 4 more to decelerate) if it's just you and your ship and energy source weight nothing. That's definitely science fiction. 100 years is optimistic.
[0] http://convertalot.com/relativistic_star_ship_calculator.htm...
[1] https://www.omnicalculator.com/physics/relativistic-ke?v=v:....
But looks like you forgot about relativity and that starts having a pretty big impact.
For the record, I think your questioning of "what black holes really are" is prudent. The OP article is not prudent, firstly because any of its implications won't be realized for at least 3,000 years. Secondly because our challenge as a society is very much not speculating about this thing Hawking wrote about, and very much is trying to make any of these scenarios useful to us.
Which leads to my fringe opinion that we should try really hard to build a black hole, even if we're worried about it ending us.
"Fuckin' magnets. HOW DO THEY WORK?"
Or maybe it's because he proposed we dedicate our resources to violating the laws of thermodynamics ("free energy"...)
As I understand it, the idea is simply impractical. But there's a huge Tesla fan base among the intersection of conspiracy theorists and amateur (pseudo)scientists who believe that Tesla's idea was scuttled and suppressed by Big Electric to protect their monopoly on generating electricity in harder ways.
What could possibly go wrong with that idea?