On Wed, Apr 19, 2017 at 06:33:50PM -0400, Jeffrey Schwartz wrote:
> "With negative mass, if you push something, it accelerates toward you,"
>
> Potentially M-Drives too.  Would a rocket motor with negative mass
> exhaust be able to recover the propellant?

If you had balanced positive and negative masses, then any force
between the two would accelerate both of them in the same direction at
the same rate.  Apart from some rather nasty instabilities internally,
it could behave much like some sort of cross between a reactionless
drive, and the inertialess drive of the Lensman stories.

Unfortunately the "negative mass" fluid reported recently does not
actually have negative mass.  It has positive mass, but carefully set
up so that the net effect of certain interactions within those limited
conditions is similar in some ways to something with negative mass.
It is certainly worth studying, because the dynamics of this state is
not well known and there are definitely some counterintuitive
features.  It does not have any applications for warp drives or
antigravity, though if something with truly negative mass is ever
discovered, these sorts of experiments would likely give us a better
idea of how it behaves and what we could try to do with it.

It's similar to other articles in that past that reported that a
particular arrangement of supersonic flow was an "artificial black
hole".  There was some tenuous justification, since sound can't get
out against the flow, and there is an analogy between a type of noise
resulting from this and the predicted Hawking radiation from a real
black hole where light can't escape.  For the very narrow and limited
purposes of their experiment, it behaves like a black hole should, and
the outcomes of the experiment give some clues as to how those
annoyingly inaccessible real black holes might behave.

- Tim