Stars, planets and other Sci-Fi peeves

IIRC, I mentioned right at the event horizon one something like "whether it can withstand the tidal forces at that distance is another question".

Well, you probably know most of this if you even ask the question, but I'm going to take it slow and long winded anyway.

The short answer is that it depends on your size and the size of the black hole. Since what counts for tidal forces in the gradient of the gravity field, and the distance over which you "feel" that gradient.

Essentially the difference between your closest and farthest point is (1/r12 - 1/r22)MG. For objects that are very small compared to the size of the black hole, or for really approximate back-of-the-napkin calculations, we can pretend it's just the gradient times the size of that object.

Well, the gradient is the derivative in respect to r, of r-2, which is an elementary one. It's -2r-3. So the gradient is inversely proportional to the CUBE of the distance from the centre.

So as you've figured out by now, a small black hole would indeed rip you apart, a supermassive one, probably not so much.

Well, let's do some maths. Sagittarius A*, the biggest black hole in the Milky Way, and the one at the centre of it all, is about 12 million km in radius and has a mass of 4.1 million solar masses.

Well, much as I love screwing up the maths myself, there are gravity calculators out there. I'll use a random one, namely this one: https://www.ajdesigner.com/phpgravity/newtons_law_gravity_equation_force.php#ajscroll

at 12,000,000 kilometres, one killo will weigh: 3778966.7737303 N
at 12,000,001 kilometres, one killo will weigh: 3778966.1439025 N

Of course, in free fall what matters is the difference, which is just a little over half a newton over a whole 1000m distance. Or for you imperials, every pound at the far end of our 1km long ship, would effectively pull back on our hull with a force of about an ounce.

But that's actually not respecting action and reaction, from the point of view of our free falling ship. What it would feel is really a half an ounce pull in each direction. That's what each pound of mass at the very tip or end of our ship contributes.

You can integrate over the length and shape of the ship, but really it's not a whole lot. I mean, sure, it could cause some warping and stretching, but I have doubts that it would actually take apart a hull that's built to resist photon torpedoes.

Of course, most black holes you'll meet will probably be under 10 solar masses or so, which would really rip you apart at the event horizon. Other points in between, well, your mileage may vary.
 
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And now for something completely different

Speaking of black holes and FTL, well, I figured let's try something positive for a change. So rather than complain about a trope, I will present an idea that is actually correct as per GR, but it doesn't seem to be done much.

Namely: Schwarzschild wormholes, also known as Einstein–Rosen bridges. (So you even get to name-drop Einstein. How cool is that?;)

Thing is, on a Penrose diagram, a Blackhole has not one but TWO event horizons. One is the one we see, and one is, well... SOMEWHERE. It would be an universe just like ours, or maybe it IS another place in ours, which observes its own event horizon to the same black hole.

Thing is, you NEED FTL to use it as a wormhole, because both "doors" lead to just inside the event horizon of a black hole. So if you don't have SOME way to get OUT of a black hole (which FTL would do just fine), you're screwed.

And it would have to be a really big one, so the tidal forces don't rip you apart.

So what would happen if you go into such a black hole and out again? Nobody knows, really. You might just exit in the same place. You might end up in a mirror universe. If Susskind is right about entanglement, you might end up half-way across the universe, outside a completely different black hole. Or something entirely different.

Since nobody really has a testable answer, you can actually take your pick.
 
Yeah, cool idea, and I've never actually seen it done.

It's also interesting that getting from the exterior of one black hole to the exterior of the other would also depend on how old they are, as the length of the "bridge" expands at the speed of light.
 
Something else I've never seen done:

In sci-fi we usually see a few kinds of power source: nuclear fusion or anti-matter or just some made up technobabble with no real world counterpart.

An idea I like is using a micro-black hole as a power source. If you have the technology to make a small black hole (maybe in some sort of collider) then it will give off Hawking radiation. Large black holes are extremely cold, but for a small enough black hole you that radiation can be relatively high intensity gamma rays.
At the same time you can feed new matter into the black hole, and if you do it well enough you can make up for the loss of mass through Hawking radiation by the injection of new mass. What that means is you'll basically be turning the energy in any kind of matter you want to toss in directly into gamma rays. Then you just need to harvest that energy to do work.

Of course it's much easier said than done. You'll have to have some way to keep the black hole in place. I'm thinking use a charged black hole and control it with magnets. You'll have to get the new matter in through the stream of high intensity radiation. As you toss it in the forces on that new matter will accelerate it in a way similar to the accretion disk of any other black hole and that will probably lead to problems. If you put too little stuff in your black hole will start losing mass, meaning the energy output will go up leading to less mass, etc. and you can get a catastrophic explosion. Finally I haven't actually done the math to figure out what the maximum power output of such a black hole would be, and it might be that while large it's too small for the purposes of something like star trek, though I suppose you could have many such holes in your engines. I'm sure there are other issues.

Still, given that there's no way that I can think of to actually make large amounts of antimatter this seems to be one of the most viable energy systems for starcraft. Plus it would just be cool. I'm surprised I've never seen it, though I'm sure it's been done in fiction.
 
I think it's cannon in Star Trek that the reason Romulan cloaking devices are so effective is that instead of the matter/anti-matter reaction that most of the major powers use they use an artificial singularity, so while it's possible (although hardly easy) to detect a cloaked Klingon ship via all the various emissions its systems give off, especially if the ship's reactor shielding isn't on point) while a Romulan Ship traveling at cloak only gives off a very tiny amount of Hawkings Radiation (which the Romulans are pretty good at shielding/collecting) which is much harder to detect since you have to be looking for a small amount of a very specific amount of radiation.

Not sure how well it translates to real world physics, but it's a clever enough little plot detail on a technobabble level.
 
Whether there's a direct connection with the cloaking technology or not, it's definitely canon that Romulan warbirds in the TNG era use a "forced singularity" as a power source. It's stated in an explanatory line in a late TNG episode, when a couple of life-forms that live in higher dimensions thought it looked like a good nest to lay their eggs in, and the attempt to do so injured them and screwed up the local intersections of the dimensions, thus radically slowing down time on the ship to an apparent stand-still from the Romulan-human perspective.

The episode was also noteworthy for a few other reasons:
  • They found a use for Troi that fit her background & expertise, when she needed to very quickly assess someone's medical condition and decide what to do about it. (Psychiatrists are medical doctors.)
  • We got to see Picard go all loopy from a side effect of the time-frozen environment on his brain.
  • Worf raised a security concern, it was taken seriously, and his recommendation was carried out. (The Romulans asked for a computer to temporarily replace one of theirs, he told Picard that they must not give away Federation technology, and Picard said they would just need to settle for an older declassified system.)

* * *

In TOS, Scotty got a stolen Romulan cloaking device to cloak the Enterprise. I guess they used the same power source as the Federation back then.
 
Captain_Swoop said:
Why would they need to be crewed at a 'density' similar to a present day Aircraft Carrier?
Lots more automation, service droids etc would mean a smaller crew was required.
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I've not said they do. What I have said is that IF they were, they would have immense crews. And IF they were not, the ships would feel virtually empty.

I'm perfectly happy to believe a mile long spaceship has a crew of 1,000. What then bugs me is that we should then see crews walking around the interior and it would be this creepily empty place where you can wander for hours without ever seeing another person.

In fact, think of Alien. That's exactly the vibe the Nostromo/refinery had, with this huge ship that was basically miles and miles of dark empty corridors.

Instead we almost uniformly see ships with busy corridors, crowded crew quarters, etc -whether it makes sense or not.
 
Seismosaurus said:
I've not said they do. What I have said is that IF they were, they would have immense crews. And IF they were not, the ships would feel virtually empty.

I'm perfectly happy to believe a mile long spaceship has a crew of 1,000. What then bugs me is that we should then see crews walking around the interior and it would be this creepily empty place where you can wander for hours without ever seeing another person.

In fact, think of Alien. That's exactly the vibe the Nostromo/refinery had, with this huge ship that was basically miles and miles of dark empty corridors.

Instead we almost uniformly see ships with busy corridors, crowded crew quarters, etc -whether it makes sense or not.
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As I said earlier most of those ships are portrayed as having some sort of fast transport system to get from place to place inside of them. Why would they build vast hallways for the crew to wander around in when the crew isn't large enough to need that space? They need space to live (crew quarters) and work, and they can use their turbolifts to get from one to the other. The spaces that are built for people should be small and crowded, as anything else is a waste of resources.
 
Roboramma said:
Yeah, cool idea, and I've never actually seen it done.

It's also interesting that getting from the exterior of one black hole to the exterior of the other would also depend on how old they are, as the length of the "bridge" expands at the speed of light.
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Crysis 3 used it.
 
Roboramma said:
As I said earlier most of those ships are portrayed as having some sort of fast transport system to get from place to place inside of them. Why would they build vast hallways for the crew to wander around in when the crew isn't large enough to need that space? They need space to live (crew quarters) and work, and they can use their turbolifts to get from one to the other. The spaces that are built for people should be small and crowded, as anything else is a waste of resources.
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Star Trek has turbolifts, but other franchises generally don't show us anything like that, so we would need to just imagine that they're there around the next corner in the hallways we do see (next to the bathrooms we also don't see). And Star Trek also explicitly shows us diagrams of ships full of hallways which the designers have even admitted must stand empty most of the time because there's just so much space devoted to them.
 
Delvo said:
Star Trek has turbolifts, but other franchises generally don't show us anything like that, so we would need to just imagine that they're there around the next corner in the hallways we do see (next to the bathrooms we also don't see).
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I'm pretty sure they have them in star wars, at least in the Death Star. Babylon 5 had them, at least on the station though. There wasn't that much action taking place on ships that we would necessarily have seen it. I think I remember them from Battlestar Galactica, though I might be making that up. I just recently watched The Expanse and they had them in that.


ETA: It's also not exactly necessary to have turbolifts if the populated part of the ship is all close together.
 
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Actually, I like the Romulan singularity for a lot more reasons than detection.

1. For a start, it has 100% matter-to-energy conversion rate. Matter and anti-matter in a warp core like the Feds use would actually be far less efficient than people think.

And, as usual, let's do some maths. You knew I was gonna do that, right? And before we start, something most probably already know, but just to have all the premises on paper... err... in screen: each particle can only annihilate with its antiparticle version.

Well, electrons and positrons are the happy case. They convert into two gamma photons, so 100% conversion rate. Nice.

The trouble are the protons, which in hydrogen are responsible for almost 1900 times more mass than the electrons. In a proto-antiproton annihilation only 0.5% of the energy goes instantly into gamma rays. It also produces on the average 1.5 neutral pions and 3 charged pions. The neutral ones almost immediately decay into gamma rays, so that's good too. The charged ones decay into muons and neutrinos within 20m or so.

And that's the problem, since you can't actually do much with muons and neutrinos for power production. You can't use neutrinos to heat something or whatever, because they don't interact much with normal matter.

Best you can do, I suppose, since these are charged, is direct them out as propulsion mass. Or, I suppose, it might be why Fed vessels run more on warp-core plasma than straight-up electricity. I assume that that "plasma" is those charged particles directed down conduits.

By comparison, a Romulan singularity gives you straight-up gamma rays, at a 100% conversion rate. Which is less of an engineering problem to get useful energy out of.


2. The micro-singularity IS the energy storage too. You don't have to carry tons of antimatter around.

Not many people seem to realize, but even assuming 100% efficiency, gram of matter and one gram of antimatter you should get 1.8×1014 joules of energy or about 43 kilotons. Sure, it's huge, but when you look at the insane numbers listed for the warp-core power for Fed ships, they would be burning through antimatter like a battleship burns through oil. Quite literally.

In fact, that also answers the question of size to crew ratio: most of the space inside would be just fuel storage.

By way of comparison, a romulan ship would have all its energy inside a cubic micrometre or so.


3. Antimatter is actually a crap way to store energy.

I mean, sure, it has the density, but if you were to, say, convert electricity to antimatter to store that energy, the maximum theoretical efficiency you could POSSIBLY achieve is 50%. Why? Well, the Law of Baryon Number Conservation says that when turning energy into matter, equal amounts of matter and antimatter must be created. So half of your power goes into making more ordinary hydrogen.

By way of comparison, a black hole converts energy into mass also at a 100% efficiency.


4. It's actually easier to control the output than some would think. You don't just have to throw matter in to keep the black hole from shrinking and exploding. You can control it by just supplying photons for it to absorb back.

If it absorbs more than it emits by Hawking radiation, it charges, if not, it's got a positive energy output. And you can control exactly what that difference is.
 
Well, I should probably also add a disadvantage: in case it goes boom, like warp cores tend to do on a regular basis in ST, with a singularity ALL your energy stores would go kablooie inside microseconds. THAT is going to be a more massive explosion than any Fed warp core breach.

Though, I suppose, on the positive side, if you had to eject the warp core, you could probably eject that heavily charged singularity at near relativistic speeds away from your ship. That is, if you built your ship to have a massive accelerator as a way to eject the core. You'll still be dead in the water... err... in space, but it might increase your chances of being dead in space instead of being a giant fireball.
 
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Not sure exactly what the Romulans do with the energy radiated by their singularity. They tend to be a rather secretive bunch ;)
 
HansMustermann said:
Well, I should probably also add a disadvantage: in case it goes boom, like warp cores tend to do on a regular basis in ST, with a singularity ALL your energy stores would go kablooie inside microseconds. THAT is going to be a more massive explosion than any Fed warp core breach.
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What do you mean? How would a black hole go boom? The only downside is that you can't shut it off.
 
Argumemnon said:
What do you mean? How would a black hole go boom? The only downside is that you can't shut it off.
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Quite easily, in fact. The smaller it gets, the faster it evaporates.

A wee little black hole with a mass of 2.28×105 kg, i.e., just 228 tons, would evaporate in almost exactly 1 second. Problem is, all that mass is converted into energy. Namely, 2×1022J or 5×106 megatons of TNT worth of energy.

That thing is literally going to put out as much energy as 100,000 Tsar Bombas, the most hideously overpowered nuke we ever detonated on Earth so far. And all that within a second.

Mind you, just to make it clear, you only need to worry about it for REALLY small black holes. Any black hole with more mass than the Moon or so, is colder than the cosmic background radiation, so essentially it absorbs energy faster than it evaporates.

A black hole with the mass of the moon is just 1mm or so in radius, so anything that you're likely to deal with in SF is probably going to have to be more massive than that.

Edit: anyway, in case it wasn't clear, the ones the Romulans use would have to be really small ones, so they put out a net positive power as they evaporate. Which leads to the problem that if you let them discharge past a point, and can't somehow force an equilibrium, the power output starts pretty much going exponential with time. So, yeah, your reactor gets damaged enough so it can't force that equilibrium any more, it goes boom.
 
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BTW, another rather trivial corolary, is that if you have to power a bigger ship, what you want is not a bigger black hole. You want either an even smaller one, but then it doesn't store as much energy, and poses other engineering challenges, or... several of them. Realistically, to make a bigger Romulan ship, probably the easiest way would be to have several of those singularity warp cores.

Which would probably also have the side effect that if you have to eject one of them, you're not yet dead in the water.
 
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