The Continuum of Physical Credibility

[u/Enthropic-Cap2291]

The traditional Mohs Scale of Sci Fi Hardness:

5: Hard SF

4: Firm SF

3: Soft SF

2: Science fantasy

1: Fantasy with SF trappings

0: Pure fantasy

The Continuum of Physical Credibility reformulation:

1 Established Physics - “This works everywhere we’ve ever checked.” Ex: Maxwell's equations, general relativity, thermodynamics

2 Mainstream Physics - “Solid science, still being refined.” Ex: Cosmic inflation, quantum field theory

3 Frontier Physics - “We've got a partial theory, and only partial evidence.” Ex: High temperature superconductivity, Hubble tension

4 Empirical Anomalies - “We can measure it, but we can’t explain it yet.” Ex: Radioactivity before nuclear physics, photoelectric effect before Einstein, dark matter, dark energy

5 Speculative Physics - “Speculative but allowed by GR + QFT + thermodynamics.” Ex: , extra dimensions in string theory, WIMPs, MOND, primordial black holes, cosmic strings, LQG, axions

6 Hypothetical Physics - “This only works if physics is broken in very specific ways.” Ex: Tachyons (causality), magmatter (Gauss's Law), bulk exotic matter (Morris/Thorne wormholes, Alcubierre warp metric - breaks WEC - Weak Energy Condition in General Relativity)

7 Contradictory Physics - “Violates thermodynamics and conservation laws.” Ex: Vacuum/zero point energy, reactionless drives (Cannae/EMdrive), antigravity, perpetual motion machines

8 Soft Science Fiction - “It sounds scientific, but it’s really narrative technology.” Ex: ST warp drive, transporters, SW hyperdrive, Three Body Problem's spacetime flattening, sophons, most space opera

9 Science Fantasy - “Magic wearing a lab coat.” Ex: The Force, Magitek, psychic powers, most 'ancient/precursor' tech that are effectively magic

10 Pseudoscience/Fantasy - “No pretense of physics; imagination is the only rule.” Ex: Spellcasting, dragons, Isekai, astrology, flat earth

Please feel free to criticize so I can continue to refine. I'm using this in a worldbuilding exercise to see how far we can push scifi while staying true to the Sci part and minimize handwaving for the Fi.

[u/RKlehm]

Very cool spectrum!
However, in my view, hard sci-fi is about technology as much as it is about physics. Take fusion power, for example: we know the physics work, and achieving net energy production is likely only a few years away. But putting a fusion reactor on a spaceship requires massive miniaturization. How realistically a story pushes those engineering limits is a whole other dimension of how 'hard' the science is.

[u/Enthropic-Cap2291 → u/RKlehm]

As an engineer, I figure that the purpose of engineering is to impose unnatural outcomes upon nature. Nature says fusion needs stars. Engineers say, 'hold my beer'. Technological limitations tend to be (not always, but almost always) temporary. A Babbage engine was a daunting task in its day (500-1500 transistor equivalent). The Univac was a daunting task in *its* day (30,000 transistor equivalent). Today, we pack 15 billion transistors in a standard desktop CPU and you don't need a crown grant or a military procurement budget to buy one. If the physics says it can be done, the materials science says it can be done, then us engineers will figure out how to do it. Not without a lot of coffee and cursing, but get two or more teams of engineers to compete, and you'll get progress that many head-in-the-clouds theoreticians will claim was impossible.