@Mithrandir24601 yeah...I'm not sure what position she'd be in to demand much of anything in the face of someone who dropped the Mountain just like that...
@JoeBloggs I've got a Masters in stuff like that, if that's any use, although it'll maybe take me a few hours to get round to having a look, depending on what it is
@Mithrandir24601 I’ve got a bachelors but I’m rusty as hell. So: Special relativity is the special case where a reference frame isn’t accelerating. It’s easy to show that leads to causality violations if you allow FTL. But if an FTL event causes an accelerative force, can we assume the special case can be broken in all cases?
Ie can we say special relativity can be thrown out in all cases if we know there’s a ubiquitous force accelerating all reference frames?
@JoeBloggs I'd say yes, simply because you're no longer in inertial frames
... But it's very possible that you'd end up with the same result as if you didn't...
@JoeBloggs Although generally, if it's just a not-insane (and maybe even if it is) acceleration on 2 (or n) different frames, but the background is still Minkowski, you can still use SR - is that what you're asking?
If it's not Minkowski, then you might want to start looking at Penrose Diagrams. I'm still not really sure what your actual problem is though
If you're taking the thing as going FTL from A to B, then FTL back to A in such a way that you violate causality, then you need to include the acceleration at B in the same way you do when looking at the twin paradox
Otherwise you've got an infinite acceleration in there, which you haven't taken into account
@Mithrandir24601 I’m considering the most general case I can think of to violate causality, which is ladder in a barn if you assume you can close the doors with an FTL signal.
@JoeBloggs Ah, OK. Forget about FTL signals for the moment and assume that you know the exact moment that the ladder enters the barn in every relevant frame and that you're able to program the doors to open/close in advance, making it appear that there's an FTL signal, only not
@JoeBloggs Yeah, I asked OP for a clarification: what do they want with this? Do they want conflict? Because of so we can adjust the scenario to reach that goal. :)
@JoeBloggs Aha! Try applying what I said above about having a predefined time instead of an FTL signal. If there's still a paradox, then you've made a conceptual error
The trick is that instantaneously in one frame of reference is not instantaneously in another, regardless of how the signal was sent - if you have an FTL signal, there is exactly one frame in which this is instantaneous - in all others it's just FTL and non-instantaneous
@Mithrandir24601 there isn’t a paradox if you predefine the times.
@Mithrandir24601 that’s pretty much exactly my point: but assuming that there’s one frame it’s instantaneous in leads to the temporal paradoxes everyone loves so much. The most general way to show the issue with FTL signals is by saying ‘it’s instantaneous, whichever frame of reference you’re in’ which is essentially the same thing just with fewer steps.
It just leads to a spatial oaradox (the ladder both fits and doesn’t) rather than a temporal one.
question is: can we force all signals into frames of reference where the non-simultaneous FTL signals cannnot go backwards in time by accelerating them?
Oddest sentence I’ve written in a while..
Or, to put it another way, can we use acceleration to force the same results if we assume FTL signals are instantaneous in all frames of reference?
@JoeBloggs Unfortunately, this is wrong though. The problem is actually rarely (if ever) sending a single FTL signal, but sending multiple FTL signals - one from A to B, then another back from B to A, which is where paradoxes actually come in. However, yes, I get the point that we can create paradoxes using FTL signals
@Mithrandir24601 you need two FTL jumps if you assume one reference frame is the one where it’s instant, and why assuming it’s instant in all reference frames is a much faster way to prove that there will be paradoxes.
@JoeBloggs You've sent a signal: therefore you've already defined a frame for that signal. If you don't have one preferred frame of reference, then you've either broken more fundamental physics, or you're talking about some form of quantum relativity and things get much more complicated
again: the assumption there is that the method of sending the FTL signal has a preferred frame. That’s a nice thought, and intuitive, but it’s faster to demonstrate that FTL causes paradoxes if you don’t assume it’s true because, as you say, everything immediately breaks.
The pint is that this is a way to demonstrate why something is broken: the faster you can get it to break the better.
Point*
But: from there it’s obvious that no matter what you do FTL is broken, which is why I turned to acceleration as a way to force FTL capable vessels to share a reference frame as the signal reached them.
Which I now realise requires the force to move faster than the speed of light, so no: general relativity can’t be used..
@JoeBloggs The issue is that why everything breaks is different - if there's no difference in different frames, two different velocities are equal, so acceleration no longer makes sense
@Mithrandir24601 Hmm.. interesting.. in the special case you can trivially show that ‘FTL signals have a starting frame’ is equivalent to ‘FTL signals are simultaneous in all frames’ Using an arbitrary number of FTL jumps. I’m not sure the same is true for the general case..
@Mithrandir24601 assume you have an infinite number of relay stations such that there’s one for every frame of reference. Station A sends an FTL signal instantaneously to all relays. All relays then forward that signal, again instantaneously, to all other relay stations. Now all relay stations at all times have a a copy of the signal, and so all reference frames can be considered to get the signal simultaneously, it’s just a matter of picking the right jumps to do.
@Mithrandir24601 it’s a mathematical trick. The funnier version of it is using an infinite number of relays that all have a finite number of drones: you can still get a signal to every station at all times.
@Mithrandir24601 it’s just a conceptual way to demonstrate that any FTL implies simultaneity if you pick the right frames to flit around in. Acceleration sadly doesn’t apply to that situation as nothing actually changes reference frame but the information: even if it’s a drone flashing past at an appreciable fraction of C you can still pick a path of relays to bounce the signal through until you achieve the equivalent of simultaneous transmission.
@Mithrandir24601 but I’m not sure on is whether if holds true if the relay stations are subject to some acceleration.
@Mithrandir24601 the multiple signals don’t really exist: that’s just a way to show that you can turn any ‘I made many jumps and caused a paradox’ problem into a ‘signals were recieved simultaneously and caused a paradox’ problem, or vice versa
Right.. let’s define an actual problem. I’ve got a ship that can FTL instantaneously. If it can change reference frame mid-jump then it’s pulling infinite g, so it must be jumping, changing reference frame and jumping again.
Anyone wanna take a shot at making me understand the thinking behind that 300rep bounty on this question on the area of a nation? The reason stated is 'that the question has not received enough attention' - but when I look at it it has gathered more and better answers than the average question does on here :/
@dot_Sp0T Will is an eccentric and wants to promote a question with a longer answer of his that has zero points? To be honest, I have no idea, but it's his decision what he wants to do with rep. If he likes the question he can promote it as much as he wants. You can just write a comment under his answer and ask him.
@Mithrandir24601 Not really. In fact the only way I can think of to effect an accelerative effect (hah) on other observers is by warping space. Possibly a wormhole would be a better conceptual bet...
@Mithrandir24601 I tried working through the maths for krasnikov tubes once. Never again,
hang on. Are you trying to solve the infinite relays problem with accelerating relay stations?
or trying to see if there's a way to get around FTL breaking causality by forcing acceleration?
@dot_Sp0T Genuinely not sure, but having dealt with distances, areas and search algorithms based on arbitrary polygonal projections onto a sphere I can attest to the fact that you could write a whole damn paper on the subject without breaking a sweat.
just been wondering because I did not see any correlation between the question and the bounty reason. There would be better suited ones / as well as the possibility of adding an additional reason yourself.
Just thought someone in here might see what I don't :)
I asked a question a little while back
How long could someone with locked in syndrome survive in 1915
While i did not word the question to say "in a 1915 like tech level world"the question would be identical
I also see a questions like this:
How long would it take to travel approximately 170 m...
Hey, @Will, we're looking for a bit of clarification on why you placed the bounty, e.g. what sort of additional details you're looking for in an answer (if that's the case).
@dot_Sp0T You could only ping him if he was here before. I don't think I've seen him around, so mods are the only ones who can summon him. You could have still just wrote a comment under his answer to that question he put the bounty on.
@dot_Sp0T Like Secespitus said, I had to use a mod superping. In theory, we're only supposed to use it for actual moderation issues, but I figure that understanding a bounty counts. ;-)
Unrelated note: Anyone have a space-travel question they want more answers to? I'm unabashedly hunting for that tag badge, and I need one more answer.
Probably spaceships, lasers for sure. space-travel would work if it's about using the system while in space. Although I'm never sure where the line's drawn.
Looking at space-travel questions in the search I see that most of them could do without said tag.... if you want to I can add the tag to my deimos question :)
The Humern Empire is a vast, well established empire that spans the galaxy. Despite having no FTL travel they have kept their empire together with a series of subluminal transport methods.
Heavy cargo loads are moved from system to system using a finely tuned web of Photonic Laser Propulsion bas...
@HDE226868 Not asked it before because I've got a couple of answers myself, but it is an interesting question. I hope I've gotten the question across well enough.
@JoeBloggs What if you have a sort of pyramid structure? A station launches one ship that is then propelled by the ship behind it. That ship is then propelled by the station directly - but is given more of a boost, so it's not pushed backwards by the force of its laser. I'm not 100% sure that's theoretically sound, but it might be.
I'm just writing this here as a sanity check of sorts.
@Mithrandir24601 Precisely, then have each ship 'fly' on a frequency all other ships sails are transparent to, leading to each ship having different coloured sails. :D
@HDE226868 That was my first thought when I came to it too, but with each ship being a much smaller version of the base station so they end up pushing each other in a steady stream
@HDE226868 I think it actually works really well with the photonic methodology because then once you've established each ship in the chain as long as you keep pushing power into the gain medium you can keep pushing.
@dot_Sp0T How would they even do that though? They'd need a project Orion kind of ship just to catch up and slow down again. Unless they hijacked the railway and used a smaller skiff..
@HDE226868 not if each ship acts as a base station in it's own right...
I imagine pirates shipping their own chemical rocketships / spaceyacht aboard one of the cargo liners and booking passage aboard the same or another one
@JoeBloggs well, removing one waggon from the sequence can has terrifying consequences depending on the safe-guards, etc. available. Assuming there is no FTL for anything then at the point when you find out the railway is compromised it is already lost for good
@dot_Sp0T Not only lost for good, but you now have a train of near-relativistic projectiles heading directly for an inhabited system and no real way to stop them past blind luck.
By the time you find out the railway is compromised you're a few weeks away from system-killing bombardment.
@HDE226868 In my Green universe, I introduced beam relays to address the issue of feedback time in aiming. And of course, by absorbing and re-creating the beam you reset the beam's spreading.
And turns out that the "comet" was actually an asteroid.
So, A/2017 U1 (PANSTARRS) is now a thing, rather than C/2017 U1 (PANSTARRS).
Also, gentlemen, I have to ask: during the Invasion, since the States have their election year, what exactly does Pence do about the issue during the Invasion?
I asked a question a little while back
How long could someone with locked in syndrome survive in 1915
While i did not word the question to say "in a 1915 like tech level world"the question would be identical
I also see a questions like this:
How long would it take to travel approximately 170 m...
I couldn't figure out how to search this so:
Is there a list of all the privileges and their reputation caps?
The Factory Floor
The Factory Floor