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> the arbitrary nature "Sci-fi" already tells you what's the fictional part of the story: the science/tech, and maybe some fundamental rules around those. Fant

> the arbitrary nature "Sci-fi" already tells you what's the fictional part of the story: the science/tech, and maybe some fundamental rules around those. Fantasy is where you get to rewrite the basic rules of the universe. In the span of a few decades we went from no planes to flying at almost Mach 10 in air (X-43) and 600.000km/h in space (Parker probe), and from AM radio to a super-computer in everyone's pocket. So you can bet any person can reasonably imagine that in a few centuries we could be advanced enough to build today's sci-fi. That's because they have a few real anchor points in the history of human civilization or even their own lifetime and an easy assessment of the progress of science between them. Most people also actually think asteroid belts are that dense. But that's because even basic concepts about gravity aren't immediately apparent from day to day experience. Basic grasp of gravity will never allow you to believe it naturally "wears off" in an asteroid field so the chunks stay close enough to even collide but magically never clump together, or that 1000 years "in the future" will change what was constant for billions of years. It only seems arbitrary if you don't bother to think about it.

everforward 2y ago
I feel like most people grasp the decay of gravity because of space, and because the moon doesn’t crash into us, etc. I would wager it’s because the space involved is incomprehensible. It’s not obvious why rocks being 600k miles apart forms any kind of feature. That’s 24 trips around the circumference of the earth. I had honestly presumed they were closer. Not sci-fi movie close, but maybe a few miles in between? Space is incomprehensibly large to me.
- haccount 2y ago
  If they grasp how gravity is "decaying" because things are in orbit then they've failed to understand both orbital mechanics and how gravity drops off at distance.
adastra22 2y ago
I think what you're saying is right but the explanation is backwards. I think of "science fiction" as being fiction in which the science is held constant--the universe works more or less the same way, but with humanity and their technology exploring a different landscape of the possibility space. So the science is real, not fictional. The plot is fiction. Of course this assumes we're talking about hard sci-fi, which doesn't include stuff like Star Wars.
- woooooo 2y ago
  Most hard sci-fi breaks the rules too unless it's strictly near future on earth with no space stuff. Ramscoops don't actually work, you lose velocity collecting the mass. Everything else is subject to the tyranny of the rocket equation unless we're inventing new physics.
  - adastra22 2y ago
    Citation for ramscoops not working? Losing velocity is sometimes the point (it works as a sort of magnetic sail / parachute), but I believe the kinetic energy loss is less than the potential energy represented by using the hydrogen as fusion fuel.
    - woooooo 2y ago
      I found a paper when I deepdived after reading "A deepness in the sky" but I couldn't find it just now, sorry. IIRC, it had to do with taking a velocity hit at like 0.9c and then the best you can do is send that atom out at 0.999c out the back. And also the scoop size was gigantic to get mass in sparse interstellar space.

everforward 2y ago

I feel like most people grasp the decay of gravity because of space, and because the moon doesn’t crash into us, etc. I would wager it’s because the space involved is incomprehensible. It’s not obvious why rocks being 600k miles apart forms any kind of feature. That’s 24 trips around the circumference of the earth. I had honestly presumed they were closer. Not sci-fi movie close, but maybe a few miles in between? Space is incomprehensibly large to me.

haccount 2y ago
If they grasp how gravity is "decaying" because things are in orbit then they've failed to understand both orbital mechanics and how gravity drops off at distance.

adastra22 2y ago

I think what you're saying is right but the explanation is backwards. I think of "science fiction" as being fiction in which the science is held constant--the universe works more or less the same way, but with humanity and their technology exploring a different landscape of the possibility space. So the science is real, not fictional. The plot is fiction. Of course this assumes we're talking about hard sci-fi, which doesn't include stuff like Star Wars.

woooooo 2y ago
Most hard sci-fi breaks the rules too unless it's strictly near future on earth with no space stuff. Ramscoops don't actually work, you lose velocity collecting the mass. Everything else is subject to the tyranny of the rocket equation unless we're inventing new physics.
- adastra22 2y ago
  Citation for ramscoops not working? Losing velocity is sometimes the point (it works as a sort of magnetic sail / parachute), but I believe the kinetic energy loss is less than the potential energy represented by using the hydrogen as fusion fuel.
  - woooooo 2y ago
    I found a paper when I deepdived after reading "A deepness in the sky" but I couldn't find it just now, sorry. IIRC, it had to do with taking a velocity hit at like 0.9c and then the best you can do is send that atom out at 0.999c out the back. And also the scoop size was gigantic to get mass in sparse interstellar space.