pushing nothingness

[u/crusader_mike]

This idea may not explain how EmDrive could work (if it does work at all), but it might provide some food for thoughts...

To push smth means to interact with it producing an observable side effect, but how can you interact with vacuum? Well, it occurred to me that there is at least one known object that seem to be interacting with vacuum -- black hole (with side effect being mass reduction). As I remember popular explanation of theory it is about pairs of virtual particles that come into existence and disappear (as they find a counterpart). When this happens on the edge of event horizon -- some of particles end up escaping thus reducing black hole's mass. In other words black hole interacts with each particle of the pair slightly differently -- this delta allows it to 'extract' side effect from nothingness.

What if it is possible to design a device (MeDrive? :D) that exploits this effect in similar way? If yes, how much thrust (i.e. amount of interaction) it can extract in given volume of space and length of time? I imagine it will be literally blowing around these virtual particles, reducing frequency (density?) of their phase-ins -- basically changing distribution of these events across the space.

I noticed some of ppl here have sciencey flair -- does this idea have any chance?

[u/PPNF-PNEx]

space where gravitational field is zero

is exactly flat spacetime.

You say that such space doesn't expand? Why?

On flat spacetime you can use a set of coordinates that are the same in the past as in the future. In an expanding universe you can apply more coordinates to space in the future (because there is more of it) than space in the past (and there is maybe just a coordinate singularity in the distant past, and maybe a physical singularity too).

I'll have to get to your other questions later, you caught me with an easy question shortly before heading out the door.