[bumby]

Why must the velocity vector have a constant length?

[CydeWeys]

Now that's the billion dollar question, isn't it.

But it's true.

[magicalhippo]

As the sibling comment alludes to, it's otherwise they wouldn't behave according to what we measure.

For a deeper "why", see Feynman[1].

edit: it's related to how spacetime with a finite speed of light is represented mathematically. There's some discussion here[2] which might shed some light.

[1]: https://fs.blog/richard-feynman-on-why-questions/

[2]: https://en.wikipedia.org/wiki/Imaginary_time#In_cosmology

[numpad0]

So to preoccupy your mind with simulation hypothesis and inter-node bandwidth estimation for the cluster we’re on.

edit: wait, if the Vector4.magnitude == 1, are dense objects actually just fast/hot?

[anticensor]

With constant magnitude vectors, you can eliminate one of the numbers out of the motion simulation for each particle. Huge optimisation indeed.