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Jun
3
2019

What is hard science fiction? -- by Douglas Phillips

Science fiction is a pretty broad genre, and seems to get wider every year. Novels are categorized as dystopian, first contact, military, space opera, steampunk, horror, space western - and on and on. But another way to subdivide science fiction uses a scale that ranges from hard (a story closely tied to reality, as we currently understand it) to soft (a story with plenty of hand waving and few explanations).

My favorite scale of hardness uses time travel as an example:

In soft SF: "You sit in this seat, set the date you want, and pull that lever."
In medium SF: "You sit in this seat, set the date you want, and drive to 88 mph."
In hard SF: "A good question with an interesting answer. Please have a seat while I bring you up to speed on the latest ideas in quantum theory, after which I will spend a chapter detailing an elaborate, yet plausible-sounding connection between quantum states, the unified field theory, and the means by which the brain stores memory, all tied into theories from both Albert Einstein and Stephen Hawking."
In really hard SF: "It doesn't. Time travel to the past is impossible."

Of course, there are gradations. For example, I start my books as firmly in the hard category as I can, but loosen a bit toward medium when the story needs more traction. You might call this a medium-hard approach.

The science fiction hardness scale tells you something about the style of the book, but bears no relation to its success in entertaining readers. A hard science fiction story is not "better" than soft, it could be so bound by real-world limitations that it becomes deathly boring. Likewise, soft is not "bad". Star Wars is certainly soft science fiction, with X-Wing fighters screaming and banking through the vacuum of space as though flying through air. But it's hard to argue with the movie's ability to entertain, so we set aside our overly-analytic brains and simply enjoy the ride.

Posted by Douglas Phillips 3 Jun at 01:47
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Responses to this blog

Ophelie 3 Jun at 07:09  
Very interesting article!

One of the questions I had is if it's considered hard SF when the scientific concepts are grounded in reality but you don't take the time to explain how they work?

For example, if you have self-driving electric cars, which are close to being a reality, but you don't explain how they work, is that still hard SF?
Dougp 3 Jun at 12:37  
Glossing over how something works could still be hard sci-fi if that thing didn't really need much explanation. Some authors might write a detailed info dump that explains a technology used in the story. If that technology is integral to the story, this might be desirable, even entertaining for all the nerds out there that love futuristic technology! But every author should be careful to avoid info dumps (long-winded explanations of how something works) if that explanation slows the story, or is not critical for the reader's buy-in to the plot. I think we all recognize that self-driving electric cars are on the horizon, so that's a case where there wouldn't be any need to explain their function unless, for example, the plot relies on a failure in that technology. Other cases where minimal explanation is required might be exoskeletons, or simple cyborg technology like an eyeball that can see infrared. These are things are on the horizon and we can easily imagine how they will work. But the deeper you go into advanced technology, the more likely you need to explain how it works. If you do too much hand-waving, then you drop to medium or soft sci-fi. Again, nothing wrong with that! Just know who your audience is and write accordingly.

Another example: Artificial-gravity is a common sci-fi technology in space operas, but I'm not sure I've ever read any book that describes how it works. But since it's usually not a major plot element (it's purely to keep characters from floating around) you still might have a soft or medium-hard sci-fi story that describes how a space blaster works, but ignores the artificial gravity. Personally, I wouldn't call that kind of story "hard", unless it either described the artificial gravity or used spacecraft with a rotating wheel to keep people firmly on the floor.
Rellrod 4 Jun at 18:39  
That entertaining scale of SF "hardness" ("the Mohs Scale of Science Fiction Hardness") can be found at TV Tropes. It's one of my favorite analyses too!

Rick
Kenoshakid 4 Jun at 23:17  
Dougp

Another example: Artificial-gravity is a common sci-fi technology in space operas, but I'm not sure I've ever read any book that describes how it works. But since it's usually not a major plot element (it's purely to keep characters from floating around) you still might have a soft or medium-hard sci-fi story that describes how a space blaster works, but ignores the artificial gravity. Personally, I wouldn't call that kind of story "hard", unless it either described the artificial gravity or used spacecraft with a rotating wheel to keep people firmly on the floor.
A film, not a book, but 2001: A Space Odyssey has a pretty viable artificial gravity based on centrifugal forces which has bern reused dozens of times if not hundreds.

__________________
Only a different reality, whatever it is, may be substituted for the reality one wishes to convey. — Jose Saramago

Beorckano 6 Jun at 17:11  
Kenoshakid
Dougp

Another example: Artificial-gravity is a common sci-fi technology in space operas, but I'm not sure I've ever read any book that describes how it works. But since it's usually not a major plot element (it's purely to keep characters from floating around) you still might have a soft or medium-hard sci-fi story that describes how a space blaster works, but ignores the artificial gravity. Personally, I wouldn't call that kind of story "hard", unless it either described the artificial gravity or used spacecraft with a rotating wheel to keep people firmly on the floor.
A film, not a book, but 2001: A Space Odyssey has a pretty viable artificial gravity based on centrifugal forces which has bern reused dozens of times if not hundreds.
This makes me think of a mechanism for artificial gravity that is tied to a very small black hole that is appropriately contained in the center of a starship. The gravity of the black hole would recreate the gravitational pull of a planet in a considerably smaller volume. Perhaps the black hole is kept in check by some sort of energetic field or bombardment. It could also be a part of the propulsion system, creating a gravitational ripple in spacetime that the ship rides forward the same way a surfer will ride a wave in the ocean. If the ship were somehow holding the black hole a set distance away from itself, as it moved forward, it would push the black hole further and thus propagate the wave.

Stopping might be tough...
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Rellrod 6 Jun at 18:47  
The "gravitational ripple" propulsion method sounds rather like the much-debated Alcubierre drive.

It does seem to me it'd take some pretty ferocious technology to tame a black hole, though . . .

Rick
Beorckano 6 Jun at 18:56  
That does seem similar, though it seems to work more off of the compression/expansion of timespace than the harnessing of a gravity well.

However, I must admit that I am starting to stretch my understanding of theoretical physics. I am, after all, a lowly fantasy writer; my solution to the dilemmas is to wave my hands in frustration and say, "F*** it! Magic did it! Get bent!"
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Kenoshakid 6 Jun at 23:59  
Rellrod

It does seem to me it'd take some pretty ferocious technology to tame a black hole, though . . .
We could maybe create one in situ by that point.
__________________
Only a different reality, whatever it is, may be substituted for the reality one wishes to convey. — Jose Saramago

Beorckano 7 Jun at 00:35  
Kenoshakid
Rellrod

It does seem to me it'd take some pretty ferocious technology to tame a black hole, though . . .
We could maybe create one in situ by that point.
That was sort of what I had in mind. A very low-mass-approximating temporary gravity well. When turned off, there might be a 'gravity springboard' effect.

Which... could be a disastrously wonderful plot device.
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Blandcorp 7 Jun at 02:17  
I'm very fond of propagating the idea that spaceships need black holes, though for a different reason than a speculative warp-like drive: Hawking radiation as propellant.

I mean, sure, the tech needed to implement a starship propelled by Hawking radiation is still a bit far off, if it is even possible, but let's say my spidey sense tells me this is a bit less speculative (or in thread-appropriate terms, harder-SF) than space warping.

Nothing against space warping, mind you. It's just that every once in a while I come across a speculative physics concept that for once just sounds right to me, and I need to climb to the rooftops and shout to the world, "excuse me, do you have some time to talk about the Lord?".

Cheers.
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Blandcorp 7 Jun at 02:38  
About black holes to recreate a planet's gravity: that's a cute idea, but does it check out?

I'm assuming more or less regular physics here. To someone outside the event horizon, and modulo some weird and significant effects like Hawking radiation, the black hole is a mass like any other. If it has 1 million tons of mass, it's going to have the gravitational pull of a million tons of mass.

For comparison, the Earth has ~6*10^21 tons of mass if I understand it correctly. Doing my usual Fermi-style calculations, you get the good ol' 1g from ~10^22 tons of mass whose center is 6000km away.

Alternatively (because of that M/r squared thing), you can get the same 1g from 1 million tons of mass whose center is 0.00006km away. This seems a bit too close for comfort.

Note however also that this gravitational pull will change drastically over short distances. At 0.00012km away from the center we're looking at a mere 0.25g already— and that's just by taking a 0.00006km step away (that's 6cm, or a little over 2inches) from the center.

This doesn't mean your astronauts will be ripped by tidal forces necessarily, but it is confusing and uncomfortable to have such different gravitational pulls from foot to head.

The above of course can be ameliorated by increasing the size of the black hole. 1 million tons is not enough, obviously. Eyeballing it, I don't think a gigaton will be enough either, and that's not an insignificant amount of stuff.

There is a simple way to get 1g in the ship: have the motor provide 1g of thrust

And the other simple way is the one Kenoshakid mentioned, the good ol' fashioned centrifuge. Make the centrifuge big so tide-like effects don't get the astronauts dizzy, and this is definitely a workable system.

(Disclaimer: I wasn't very careful with the arithmetic so please check things out for yourself if so inclined, but I think I got within a few orders of magnitude of the numbers )

Cheers.

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Blandcorp 7 Jun at 02:41  
Dougp
Another example: Artificial-gravity is a common sci-fi technology in space operas, but I'm not sure I've ever read any book that describes how it works.
We used to watch ST:TNG, my Dad and me. He would joke they should build the ship out of whatever the artificial gravity system was built out of, because regardless of how low the shields or engine power or whatever got, that thing never failed.

Cheers.
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Kenoshakid 7 Jun at 03:09  
Beorckano

That was sort of what I had in mind. A very low-mass-approximating temporary gravity well. When turned off, there might be a 'gravity springboard' effect.

Which... could be a disastrously wonderful plot device.
So you couldn't get that warp-like ripple effect with just a black hole, since the mass of a black hole is always positive, meaning the force is always negative, directed radially inwards towards the centre of the black hole. Switching it off would just stop that inward force happening; the BH itself wouldn't move.

Maybe a normal BH at the front of the ship and a negative-mass one at the back would work
__________________
Only a different reality, whatever it is, may be substituted for the reality one wishes to convey. — Jose Saramago

Kenoshakid 7 Jun at 03:26  
Blandcorp

This doesn't mean your astronauts will be ripped by tidal forces necessarily, but it is confusing and uncomfortable to have such different gravitational pulls from foot to head.
Indeed. We'd all be a lot taller, and we'd need to make our furniture curved else it'll snap.

Some improvement would be a planar array of small black holes. Ideally you'd like to simulate the almost constant acceleration at the Earth's surface, so an array would get you there. Pretty strong rig required.
__________________
Only a different reality, whatever it is, may be substituted for the reality one wishes to convey. — Jose Saramago

Blandcorp 7 Jun at 03:32  
Ah, that British understatement.

Those black holes will be hot (assuming Hawking radiation is a thing).

Cheers.

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Blandcorp 7 Jun at 08:44  
Just for fun (because people even tangentially connected to hard SF have a weird concept of fun), I scribbled a bit to estimate how massive a black hole should be to comfortably approximate Earth's gravitational pull.

Note, this assumes the black hole is allowed to be a point mass in the center of the ship, and the habitats and such are built around it. Notice also the fudge factor "comfortably". For a nice round number, I took "comfortably" to mean that, at 100meters away from the black hole, the gravitational acceleration it causes is 1g. And in that 100 meters you have enough magic screening material to shield you from the Hawking radiation and whatnot.

This also has the nice side effect that 3 meters above that (so at 103 meters away) you would feel a 0.94g acceleration from the black hole. It's still going to decrease fairly rapidly with distance, as you can see, but probably not so fast that it's too upsetting.

The approxithmetic comes down to 10 thousand GigaTons. To put some intuition on that number (the dreaded "but how much is that in football fields" approach of popsci):

— it is about 200 thousand Titanics
— it is about a tenth of 253 Mathilde

What this means is, such a black hole is much, much more massive than structures we have built so far— but that's not that unexpected. If one really considers cosmic space, one needs to think big. And maybe one has their hands on some magical implosion technology that can munch an asteroid and spit out a black hole and presto.

Incidentally, the blackhole starships I'm fond of: the guys from that paper do some maths to estimate how big they should be based on radiation considerations: you want the black hole to radiate at a certain highish level to be a good propulsion system but not so high that it basically evaporates in an instant, and the figures they get are on the order of 1 million tons. That's ... quite a bit lower than what this artificial gravity needs, but in any case it shows some interesting space exploration ideas really need ya to find ways to convert phat tonnage into black holes

Cheers.
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Beorckano 7 Jun at 08:54  
Kenoshakid
Beorckano

That was sort of what I had in mind. A very low-mass-approximating temporary gravity well. When turned off, there might be a 'gravity springboard' effect.

Which... could be a disastrously wonderful plot device.
So you couldn't get that warp-like ripple effect with just a black hole, since the mass of a black hole is always positive, meaning the force is always negative, directed radially inwards towards the centre of the black hole. Switching it off would just stop that inward force happening; the BH itself wouldn't move.

Maybe a normal BH at the front of the ship and a negative-mass one at the back would work
Oh, absolutely. I'm under no illusions that my brainfart is viable for real applications of any sort. The concept I had in my mind as a 'what if' was, say for example, one were to picture the classic representation of a black hole gravity well, such as this;

BHGW

Now, imagine that you've got a craft that is circling and accelerating around the gravitational 'dip' created by said black hole like so. Normally, once it hits the event horizon, it would be devoured and added to said black hole's mass. However, if you can develop a stable orbit around said black hole, you could skate the edge and stay out of the singularity.

If there were also a way to, say, propel said black hole in a desired direction while staying in the edge of said gravitational grip, you could use the 'slope' of the gravity well to accelerate as if you were coasting down a hill. Very little energy expended since the /bottom/ of the hill is always moving away from you, while the 'top' of the hill is always chasing you. With the right balance you would always be halfway down the hill, never at the bottom, and never at the top, always coasting, always accelerating. One would have to, then, only use thrusters to keep oneself an appropriate distance away from the event horizon, which would be a significant conservation of energy as opposed to achieving near-light-speed acceleration.

My brain wants to call that balance point a Lagrange point, but I know that's not what a Lagrange point is (Lagrangian points are the points near two large bodies in orbit where a smaller object will maintain its position relative to the large orbiting bodies), but my grey matter is telling me it's a similar concept as relating to orbital stability and inertia. However, as mentioned before, I'm a fantasy writer; hard science fiction is not my forte.

I am well aware that such a system creates WAY more issues than it solves, but I had fun with the theoretics of it.

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Blandcorp 7 Jun at 09:41  
That setup puts me in mind of the well-established slingshot maneuver, and that doesn't even need a black hole.

The way a slingshot maneuver works is, loosely speaking, that as a ship passes a planet, the planet "drags" the ship for a bit and an exchange of orbital energy is had, often by the ship taking some energy away from the planet.

The difference to your setup is that the slingshot maneuver happens relatively briefly, and there's no establishing of an orbit around the body that the ship uses for the slingshot. This is because, if you orbit that body, then basically you go where it goes. That is also a workable setup (the Earth orbits the Sun and whizzes through space dragged by it as we speak), but at that point you replace the problem of controlling and thrusting for the ship with the problem of controlling and thrusting for the larger body that the ship orbits.

Usually, that's not a good deal. Slingshots are a good deal because the planets are already there and we can sometimes use them to "hop" cleverly like over stones in a river, without needing those stones/planets to be placed exactly, or go exactly where we want.

Besides, if there is a large cosmic body that happens to go where you want to go, and you have the resources to put yourself in orbit around it, then you probably have the resources to put yourself in the same orbit that body follows anyway. And following orbits through space is as cheap as it gets.

Cheers.
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Beorckano 7 Jun at 10:45  
Absolutely 100% agreed.

However, if one were to have a decent amount of Unobtanium/Phlebotinum and were sufficiently versed in Quantum Hypersciencism, one could -create- those gravity wells and manufacture multiple slingshots in a row.
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Kenoshakid 7 Jun at 10:50  
Set up arrays of alternating black holes and negative mass black holes throughout the cosmos and just slingshot around em all! I love an array, me.
__________________
Only a different reality, whatever it is, may be substituted for the reality one wishes to convey. — Jose Saramago

Gfrank 7 Jun at 11:29  
In soft SF: "You sit in this seat, set the date you want, and pull that lever."
So is HG Wells THE TIME MACHINE Soft or medium Sci-fi? At least he did one thing that is not common in most time-travel stories.. he had the traveler move in an analog way forward or backward in time, like fast forwarding or reversing as apposed to just *Pop* you are there. By moving fast forward it takes into account that he is geographically in the same place just moving forward or backward in time quickly. As apposed to Pow you are there... because in reality, if you only moved in TIME... your location would change while the earth rotates, orbits the sun, the sun orbits the galaxy and the galaxy flys away from the rest of the galaxies... you might time travel into deep space if you were not tied to that spot on the earth.


Blandcorp 7 Jun at 11:50  
Kenoshakid
Set up arrays of alternating black holes and negative mass black holes throughout the cosmos and just slingshot around em all! I love an array, me.
It's the spacetravel equivalent of a highway.

Cheers.
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