Broader implications of an FTL Fakedrive?

[aimless]

Fakedrive being an FTL drive that circumvents causality issues not via weird special provisions but by simply saying that the laws of the universe are different than what we think they are. By introducing this FTL drive the universe by implication has a new maximum speed, call it Q, and consequently all the equations of relativity are modified replacing c with Q. This I assume solves all the causality issues (you wouldn't have light cones, you'd have Q cones, formerly skewed reference frames would be much more aligned).

My questions are: is this situation I'm positing logically possible? (not actually possible, since special relativity using c has been tested to a high degree of accuracy).

And if it existed, what would the implications be for our everyday life? Say the maximum speed of the universe is increased by 10. Does that affect walking to my kitchen and making a sandwich? Or any part of our daily life on earth beyond some tweaking of GPS programming? What about at Q = 1000c? (I'm guessing there wouldn't be any everyday changes since we already ignore relativistic effects when making sandwiches) Does E=mc^2 get modified?

(Tangentially, am I correct in assuming that a universe where instant t=0 information transfer was possible then special relativity would simply not exist and things would be more or less Newtonian?)

Sorry if this belongs in OSF (anyone written a sci-fi story dealing with this in depth?).

[Stark]

Oh dear. There are pretty extreme consequences of changing the value of c; it's not JUST a speed-limit you know. Mass-energy equivalence would be massively changed, which I imagine would do bad things to all of physics.

[Patrick Degan]

And how do you change the mechanics of the universe to make this beastie work when you hit the button?

[aimless]

And how do you change the mechanics of the universe to make this beastie work when you hit the button?

Well the idea is that the mechanics of the universe have been changed permanently, or that we're in an alternate universe with these different mechanics. So there wouldn't be any button to push, since to go FTL all you'd have to do was accelerate for long enough (assuming our new max speed was significantly larger than c so that it was practical in a spaceship).

[Kuroneko]

By introducing this FTL drive the universe by implication has a new maximum speed, call it Q, and consequently all the equations of relativity are modified replacing c with Q.

Then the null geodesics in spacetime would have speed Q, rather than c. That's fine, but since c<Q, this means that light travels on timelike geodesics, and consequently photons must have mass. Electromagnetism would have a finite range.

This I assume solves all the causality issues (you wouldn't have light cones, you'd have Q cones, formerly skewed reference frames would be much more aligned).

That's true.

My questions are: is this situation I'm positing logically possible? (not actually possible, since special relativity using c has been tested to a high degree of accuracy).

Experimental limits on photon mass is a very tiny 1E-54 kg, so Q must be extremely close to c.

Does E=mc^2 get modified?

It indeed does get modified, because STR really care that it's talking about light, but rather just some phenomenon with a speed invariant across all inertial reference frames.

What about at Q = 1000c?

There wouldn't be anything in such a universe that you'd recognize, including yourself. The scenario isn't even fully self-consistent, since light would not have a fixed speed in such a universe.

(Tangentially, am I correct in assuming that a universe where instant t=0 information transfer was possible then special relativity would simply not exist and things would be more or less Newtonian?)

Galilean (Newtonian) spacetime is pretty much the simplest possible case for having arbitrarily high speeds, yes.

--
One could also interpret your scenario as the universe having more than one speed of null geodesics. Some time ago I saw a little trick to do this and still preserve the usual relativistic effects, except at those particular speeds. I don't see how to make it causal, though, and it also introduces an absolute frame of reference.

[Patrick Degan]

And how do you change the mechanics of the universe to make this beastie work when you hit the button?

Well the idea is that the mechanics of the universe have been changed permanently, or that we're in an alternate universe with these different mechanics. So there wouldn't be any button to push, since to go FTL all you'd have to do was accelerate for long enough (assuming our new max speed was significantly larger than c so that it was practical in a spaceship).

The problem is that a higher value for c has all sorts of implications as to whether there will actually be anything is said alternate universe to go to. Even if there were, what's to guarantee that the values for relativistic space/time dilation won't also similarly be altered and you're back to the same limitations as before? And how would that facilitate any usage in our universe in which you're still stuck with a 300K km/sec limit? And what would change these values in our own universe? And how would that not radically affect everything in it?

It sounds nice for the premise of Futurama but not for anything that's practicable or even possible in principle.

[Oskuro]

This I assume solves all the causality issues (you wouldn't have light cones, you'd have Q cones, formerly skewed reference frames would be much more aligned).

It wouldn't so much solve as readjust. Even if we assume the rest of the universe remains the same, by changing the value of C you're not chaning the nature of the equations, but just their scale.

There would still be an speed limit, and causality problems beyond that limit, only that it would be 3 orders of magnitude greater, but it would still be there.

In other words, from a starship drive perspective (and again, assuming nothing else changes), this would be similar to just shrinking the universe so the c limit allows us to travel further in less time.

[aimless]

Then the null geodesics in spacetime would have speed Q, rather than c. That's fine, but since c<Q, this means that light travels on timelike geodesics, and consequently photons must have mass. Electromagnetism would have a finite range.

There wouldn't be anything in such a universe that you'd recognize, including yourself. The scenario isn't even fully self-consistent, since light would not have a fixed speed in such a universe.

Freaky. Basically I was trying to find out that if you had a 'a long time ago in a universe far, far away' scenario where the speed limit was a lot higher, would that universe conceivably look mostly like ours with a few interesting wrinkles, or would it be completely fucked up. Sounds like it would be the latter

It wouldn't so much solve as readjust. Even if we assume the rest of the universe remains the same, by changing the value of C you're not chaning the nature of the equations, but just their scale.

Yup. I got interested in this because I was reading through some stuff about FTL causality and the wacky provisions you'd need to get around it, and they didn't talk about this 'option' of simply modifying special relativity...probably because as I'm being told, it wouldn't be simple at all. Conceptually simple..maybe.

In other words, from a starship drive perspective (and again, assuming nothing else changes), this would be similar to just shrinking the universe so the c limit allows us to travel further in less time.

Indeed. If we're positing such brute force universe changing methods to have star travel without causality paradoxes, might as well say all the stars are only .5 light years apart.

So that's my next question...is that a problem for our kind of life to be in a region where stars are only .5 LY apart?

[Junghalli]

So that's my next question...is that a problem for our kind of life to be in a region where stars are only .5 LY apart?

I don't see why it would be a problem. .5 light years is still plenty of room between stars. Our whole solar system up to Pluto is less than a light day across.

One thing I can think of is IIRC that some of the Oort comets are believed to have orbits that take them out to as much as a light year from the sun, so a star coming within .5 light years might disrupt the Oort cloud and send a shower of comets into the inner system. In a place where that was the average distance between stars I imagine the outer Oort cloud would probably be fairly effectively "cleaned up" in a solar system's early history though.

[Ariphaos]

Freaky. Basically I was trying to find out that if you had a 'a long time ago in a universe far, far away' scenario where the speed limit was a lot higher, would that universe conceivably look mostly like ours with a few interesting wrinkles, or would it be completely fucked up. Sounds like it would be the latter

Messing with c is absolutely the wrong way to go if you want FTL in something resembling our Universe. You need a fixed frame that is external to the Universe in some manner.

[EarthScorpion]

Messing with c is absolutely the wrong way to go if you want FTL in something resembling our Universe. You need a fixed frame that is external to the Universe in some manner.

I don't know. It might be quite an interesting sci-fi setting, where you can get c+ motion by changing the local value of c. Of course, it's also completely useless, because the resultant changes in mu-0 and epsilon-0 shreds any matter within the field, thus making it completely useless for travelling FTL, because your device is wrecked by the change in (formerly) universal constants the moment you turn it on.

It'd probably end up being weaponised, while generations of physicists threw their lives' works away trying to find out how to make it actually useful for FTL travel.

[Junghalli]

I don't know. It might be quite an interesting sci-fi setting, where you can get c+ motion by changing the local value of c. Of course, it's also completely useless, because the resultant changes in mu-0 and epsilon-0 shreds any matter within the field, thus making it completely useless for travelling FTL, because your device is wrecked by the change in (formerly) universal constants the moment you turn it on.

I've always thought a similar scenario with "hyperdrive" would have been funny. People like to explain "hyperspace" as some dimension where c is higher, which would be hilarious if they actually found something like that. Sci fi nerds would be having orgasms at FTL being achieved and how we're now going to start exploring the galaxy in 1000 c starships, and then they find out that any matter you drop into this FTL realm disappears in a puff of disassociating atoms (or whatever happens to matter when you increase c by three orders of magnitude), making it totally useless except maybe as a neat way of disposing of garbage.

[Ariphaos]

I don't know. It might be quite an interesting sci-fi setting, where you can get c+ motion by changing the local value of c. Of course, it's also completely useless, because the resultant changes in mu-0 and epsilon-0 shreds any matter within the field, thus making it completely useless for travelling FTL, because your device is wrecked by the change in (formerly) universal constants the moment you turn it on.

It'd probably end up being weaponised, while generations of physicists threw their lives' works away trying to find out how to make it actually useful for FTL travel.

To increase c you would at least need to add energy to the system to compensate. I'm unsure how that is much different than just using sunshine and happiness, unless you are just feeling creative.