# What would happen if an object traveling faster-than-light, with negative mass, crashed into something moving at sub-light speeds? [closed]

The warp drives I have defined for my science fiction setting work by creating a field which gives the ship a net negative mass to allow for faster-than-light travel.

What I want to know is how an object with negative mass, traveling at faster-than-light speeds, would interact with a ship traveling at sub-light speeds or a relatively stationary object; such as a planet or station.

I tried plugging the numbers into a calculator for collisions and got negative energy numbers, but I don't know what a negative energy collision would look like or if it's even possible.

I know what I want to see happen from a writing/worldbuilding standpoint, but I want to hear what would realistically happen to see if it's more interesting.

Clarification: The purpose of this question was to find out whether or not there were existing theories, that I could not find, that already described what would most likely happen in such a scenario. I wanted to make sure the solution I had considered writing in did not contradict any existing theories, models or other information on the subject of negative mass.

• OK, how is this about building fictional worlds? – Mołot Jun 15 '18 at 19:07
• "what would realistically happen" It wouldn't. There's nothing real about the situation, standard calculations don't apply, there is no basis to select a "correct" answer. You might be better off describing what you think is supposed to happen and why and then ask if your solution makes sense for the framework you've provided. – Samuel Jun 15 '18 at 19:09
• @Mołot this definitely does look fictional to me :) – Alexander Jun 15 '18 at 19:09
• Of course, XKCD has what-if.xkcd.com/20 (diamonds) and what-if.xkcd.com/1 (baseballs) for us to consider. – CaM Jun 15 '18 at 19:10
• @Molot I'm trying to find out how they would interact using the warp drives I defined within a fictional setting. – Arvex Jun 15 '18 at 19:15

Mu.

The question is meaningless. We don't know what "negative energy" or "negative mass" would look like. If you're involving either of those, let alone both, you have enough handwavium to fly through space simply by jumping and letting your flapping hands power you. At this point, you can make up whatever you like so long as it sounds good. Just don't involve antimatter - it's been proven that it probably doesn't have negative mass, despite its other properties. Whatever you want it to do in the story is probably fine, as most people don't know enough about what even SOUNDS plausible.

• That's something I was kind of hoping to hear, actually. I had my own plans for what would happen, from a fictional writing standpoint, if there wasn't any prevailing theories on this already in place. I wanted to make sure I wasn't contradicting what theoretical physicists believe might happen if there were already such generally accepted theories or even simulations. – Arvex Jun 15 '18 at 19:48
• – Renan Jun 15 '18 at 20:47
• Actually, I quite like the idea of a cosmos that gives you FTL propulsion from just jumping and flapping your arms. – Spencer Jun 15 '18 at 22:59
• You'll note that the wiki entry for negative mass starts by saying that all the theories have elements of ambiguity to them, because nobody is entirely sure how negative mass works. This concept can rest comfortably in that ambiguous gap without touching the metaphorical sides. – Jacob Jun 18 '18 at 14:29

Realistically, negative mass would not enable FTL travel. You'd have to go with "imaginary mass", which is maybe just slightly more hand-waving. But that changes the parameters of your question.

Quoting from this Quora question (bold is mine): https://www.quora.com/Would-the-existence-of-negative-mass-make-faster-than-light-travel-possible

The formula E=mc^2 is a simplification of a more 'correct' description: E^2=m^2c^4+p^2c^2.

The second one is more general, and is the actual correct one. As you can see, it depends on the mass only through the square. hence having a negative mass wouldn't change anything.

To actually get negative energy (which you could use to achieve FTL if I'm not mistaken), you would need an imaginary mass.

Here things get tricky. Something physical (ie. something we can measure), has to be real (we cannot measure imaginary numbers). So while this would allow for a negative mass, it does not allow an imaginary mass.

However, you can pose the question about mass being something physical. Usually it's used as such, but I do remember once reading an argument that you never quite measure mass, but something very close to it.

In which case, it might be possible to have imaginary mass, thus negative energy, and thus FTL. Time will tell.

• I was under the impression that negative mass was required to make FTL possible. I suppose just negating its mass (0) is all it really needs to do. – Arvex Jun 15 '18 at 19:32
• @Arvex As I understand it, a massless object (like a photon) still can only travel at the speed of light, not above it. – Cadence Jun 15 '18 at 19:47
• @Cadence is correct (physics.stackexchange.com/questions/4740/…) – neophlegm Jun 15 '18 at 20:30
• I know. FTL travel is impossible. This is the only violation of real physics I'm planning to do (though I might play with numbers for energy production.) I just want to make sure that everything else works about 1:1 with the real world where possible for story and gameplay purposes. – Arvex Jun 15 '18 at 20:45