basenji

Hardness is how close it is to how science actually works as we currently understand it.

0: Just repeat to yourself "It's just a show. You should really just relax." Anything with magic, whether or not it's called magic, fits here. Examples: Star Trek (in any form), Barbarella, Star Wars, Futurama, Lexx, Neon Genesis Evangelion, Farscape, most non-literary science fiction.
1: There are technologies that break some law of physics, but we have no idea how they work, or they appear to appease some higher power. Examples: Stargate, Animorphs, Cthulhu mythos.
2: The laws of physics are broken in some way, but it is explained. Expect hundred-page dissertations from fans. Examples: Babylon 5, The Matrix.
3: The only break from reality is faster-than-light travel. Examples: Contact, Avatar.
4: No FTL travel. Can be a 1 or 2 otherwise, but the physicists allow it to appease their Einstein worship. Examples: Firefly, Cowboy Bebop, Max Headroom.
5; Contains theoretical but plausible elements. No FTL travel in any way, shape, or form. Examples: Gattaca, Ghost in the Shell.
6: Real life plus space travel. The only way to grade it within 6 is based on age; newer is generally harder. Home of Zeerust: One can always tell when science and/or technology marches on. Examples: Destination Moon, 2001: A Space Odyssey, Moon just because of the "sound in space" and cloning.
7: Just like real life, but some technologies are more accessible or more efficient. Examples: The Boys From Brazil, GI Joe.
8: Real life: The world's largest MMO, which has spawned its own spinoff genre, known as "the documentary".

Nothing wrong with being a 0, of course. But many fans of mainstream SF like to imagine theirs as at least a 5.

It's so bad it's horrible.