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A relativistic fluid consists of actual discrete particles, although the quantities you can calculate will be be continuous approximations (very accurate ones).
by contravariant 11y ago
A relativistic fluid consists of actual discrete particles, although the quantities you can calculate will be be continuous approximations (very accurate ones). So, basically it is possible to make something discrete, with some associated length scale, but which looks the 'same' for all observers.
Even I am not entirely sure how to imagine such an object though, Lorentz boosts are difficult to wrap your head around.
By the way, I just realised it's a bit unclear what 'freezing it in place' means. Basically I meant that you just fix all trajectories of all particles, since there are no interactions you'll basically end up with some random straight lines. The distribution of these lines (i.e. their direction / position) will be the same for all observers.
- danbruc 11y agoI now see how that could work. I imagine creating two particle trajectories so that the distance between the particles is Lorentz invariant, i.e. it looks the same for all observers. Once you managed that you can kind of fill space with many copies making sure that the relation holds for all possible pairs. I never thought about that and it I would probably naively have dismissed the idea that you can even have two trajectories that are Lorentz invariant let alone fill space that way. And it is even more unintuitive to me that you end up with something as well behaved as a fluid and not some totally unphysical mess. Now I would really like to see a visualization of two or three such trajectories, assuming I am picturing that at least somewhat right.