Does Going Faster-Than-Light Always Lead to Time Paradoxes? - I can't understand this Video, I need someone smarter than me.

[Haim Arlosoroff]

Its the Minkowski diagram that's throwing me off. I'm probably a moron. Its a problem of the "STL ship's space axis". I can't wrap my mind around it.

• Why does the Space axis flip about the 45 degree null line for the STL ship? Shouldn't the horizontal line on the bottom be the space axis for everything? Everything is still in the same universe at the end of the day, I understand it is distorted but how does that effect the order of events?​
• Why is the ship beaming shit back in time because its moving away from the earth? Couldn't that crap just be impossible, instantaneous travel between receding objects I mean? Can I forward STL messages backwards in time if the message is initially an FTL message sent to me and I'm moving away from the transmission I'm beaming right back?​
• Why is the Time Slice for the ship at an angle even from the ship's point of view? It can only see things around it from the light getting to it regardless, how does the ship's crew think Vega recieves a warning?​
• If the STL ship's space axis is the ship's location then why isn't that the focal point for all the extra FTL messages? Why aren't they drawn from the ship's location on the space axis rather than the STL ship's time axis?​
• If the FTL message to the ship takes no time and then, let's say, instantly the Earth receives a message back How long did that message take to travel if instant FTL travel from the ship is just throwing shit back in time? Also the message back from the ship to earth, why aren't they both horizontal lines? It makes no sense, why is the ship transmitting back in time in reply? Why MUST the reply follow that STL ship's space axis angle? That seems the whole problem. That red dash line is breaking my head.​
• Why is the first thing that the crew perceive are Vega somehow receiving the message from Earth? How did that information get from Vega to the ship? Was it instantaneous? That makes no sense to me, the Time Paradox only happens if the crew know about Vega receiving the message? Is Vega FTL messaging to them?​

I get that I'm being stupid, but can someone really simply explain why there is a "STL ship's space axis"? I think that's what is breaking my head.

I just want to explore space, and space-time won't let me.​

 

[The Mass Shooter Ron Soye]

I think if you could bend space like the warp drive, there are no time travel issues.

Unless you are one of the few people working on this, there's no use thinking about it right now. Just assume that FTL is off the table forever and bring your dreams down to the level of "asteroid mining baron".

 

[ICametoLurk]

We can’t draw in 4 dimensions, so all 3 dimensions of ordinary space are reduced to the X-axis of the diagram. Motion to the left or right corresponds to movement in space. You’re sitting somewhere right now. You’re not moving. So there’s no motion left or right. But you ARE moving into the future at the rate of 1 second per second. The T axis represents motion in time. With every passing second, you move towards the top of the diagram. Any point in space or time can be shown on this diagram. Motion through space and time is, therefore, a line showing how you got there. This is called your “world line”.

Light travels 300,000 km/sec. A light ray is shown in red and marked C. The diagram has been scaled such that 300,000 km is 10 cm along the X axis and 1 second is 10 cm along the T axis. So the C line is halfway between X and T at 45 degrees. With me so far?

A ship leaves Earth and heads out into space. It travels along the cyan line T’. It is moving slower than light, so at all times a light ray which left Earth when it did is further from Earth than the ship is. Slower than light motion is called Time-like.

The pilot of the ship regards himself as “not moving” once the engines are turned off. He’s just sitting there and it’s the Earth that’s rushing away. That’s a perfectly valid viewpoint and it’s why his path is labeled T’. He’s going straight up HIS time axis.

But ALL observers measure the speed of light to be the same. Light always moves halfway between the T and X axes. If the pilot has a different T axis than you do, he must also have a different X axis. Only way he can measure light to have the same velocity as always. His space-axis is X’

Now, we’ll imagine an ansible has been invented. An ansible is faster-than-light radio. In fact, it’s instantaneous regardless of the distance between transmitter and receiver. Instantaneous is not really necessary. Any faster than light signaling will do, but it makes the diagrams easier to draw.

At 1, you broadcast an important message over the ansible. What does “instantaneous” mean? It means it takes no time to travel any distance in space. So the dashed gray line is horizontal. No motion in time at all. It is received by the space ship at 2.

The pilot sends a reply. How does it travel? Back to 1? No! That’s silly. Why should it retrace the path along your X axis. There’s nothing special about Earth’s motion. To be consistent, it has to go parallel to the ship’s X axis, the one we called X’. So it reaches Earth at 3. This is BEFORE you sent the original message at 1.

If the message sent at 1 was “planes hijacked to crash in New York”, then the police can take action at 3 to foil the plot. So the planes were never hijacked and you never sent the message at 1. We have a paradox!

You can change to any inertial frame you like at any time.



The ship left Earth at 0 and transmitted the message back at 2.
Then it used its motors to head back to Earth and landed there at 4.
Now it's back in the Earth-frame where it started and where the original message came from -- and where it was received at 3.
The ship can't get back in time to do anything about 911, but the superlight message could.

You can equally imagine you stay on Earth the entire time and your twin brother does the traveling (and returns younger than you are.)

tl;dr:

Space-axis (X) runs horizontally, time-axis runs vertically. Usually scaled so an arbitrary unit (like an inch) equals 300,000 km or 1 second. Therefore, light always travels along 45 degree lines.
Something (call it A) which isn't moving (with respect to you) runs straight up the T-axis at 1 (scaled) inch per second. If A IS moving, its vector is the same length, but tilted somewhat. Motion in space comes at the expense of motion in time.
A, of course, always considers himself stationary. His (tilted by your reckoning) path defines HIS T-axis. Call that T-prime since I can't write superscripts here. His X axis also deviates from yours. If you drew his T-prime to point clockwise of your T, then his X-prime is rotated counter-clockwise of your X. Only thus can the velocity of light remain invariant. It always bisects the angle between the X and T axes. Anybody's X and T axis.
That rotation in the "opposite" direction is why the geometry of Relativity is hyperbolic instead of a euclidean rotation. Time is subtracted, rather than added, in computing the Interval between events so all observers measure the same Interval even though they may differ in their separation into space and time.

 

[TheDarknessGrows]

It also turns the pilot into a lizard if you go fast enough.

 

[Iron Jaguar]

The whole "time stops at FTL speeds" is widely misunderstood.
It appears to stop relative to the observer who is a) travelling at FTL speed and b) looking backwards at the place he just left. However, time still carries on naturally for everyone, including the observer, who ages just as he would at sublight speeds.

In short, there is no time travel paradox because there is no time travel.

 

[TheDarknessGrows]

In short, there is no time travel paradox because there is no time travel.

At least not in regards to the speed of light.

There is still the Magneto Device in Alpha Centauri that facilitates time travel through a different means.

 

[Ultrapenguin]

If this is even remotely correct I'm positive someone would've already long since said it, but my completely armchair theoretical physics idea is that people have a flawed view of how movement itself works.

Obviously energy and mass are equivalent, we know coalescences of mass causes time dilation (because of gravitational lensing and whatnot), as such my belief is that movement is actually obtained by redistributing energy in a way that warps spacetime and pulls you, through time, in a given direction, not so much different from how gravitation almost certainly works. Movement and gravitation are fundamentally the same thing.

For example, when you take a step what's really happening is that you're drawing energy up and through you to a point towards the front of your bodily mass, and that focused redistribution of energy produces a pocket of warped spacetime in front of you such that as time flows around you, you're drawn directionally by it.

Perhaps in a way movement/gravity is just your mass lingering longer in a given orientation around you. I could imagine time itself as just a reflection of universal energy decay, and it's the slight manipulation of that by collecting enough decaying energy in one spot that's what we see as gravity and movement.


Normally that wouldn't be that useful a view, but in that context the idea of never being able to exceed the speed of light makes a whole lot more sense because you aren't reaching an upper limit of speed, you're reaching a lower limit of time. You can't ever "travel through time" because the idea of traveling itself can't occur without the forward flow of time in some measure.

The only way "Faster than light" travel could ever happen is by somehow lowering the distance between points, and that's like some Warhammer 40k territory, that's never going to happen.

Or at least that's all my theory as an idiot.

 

[I'm Retarded?]

tbh most of this stuff is just chalkboard math which may or may not be supported by a handful of cosmological observations. although that's not quite as retarded as it sounds as the framework of relativity has proven to be very consistent with real-world observations and therefore very useful as a predictive tool (many cosmological phenomena were mathematically predicted long before they were ever observed, such as black holes). IIRC the time dilation effect of extreme speed was notably observed - although in extremely small quantities - by astronauts on the moon missions.

still, there's always an element of shooting in the dark with this kind of theorizing and I think the way some of this shit, such as the ansible, causes the models to give seemingly impossible output is possibly indicative that the existence of the device itself is impossible. i.e., the reason an ansible creates a time paradox in ICametoLurk's excellent explanation is because at the end of the day you just can't instantaneously transmit signals like that (let's just pretend like quantum entanglement isn't indicating that it might be possible after all). however, the real brainfuck, which I think most people probably understand instinctively, is that sometimes the math looks wrong because our understanding of the mechanics of the universe is incomplete, and it's actually right. the former occurs much more often than the latter, but even so, you'd be surprised how often the latter occurs. sometimes weird shit that should be impossible does actually exist (such as quantum entanglement, lol). so, it's impossible to say. maybe some day it won't even be weird that we have FTL ships in observational orbit around Earth sending warning messages back in time.

the real takeaway from the FTL shit is that space and time seem to be intrinsically related in some unseen physical way. you know that phrase "space-time fabric" that gets thrown around a lot? that's what that means. the easiest way to express this is to note that instantaneous travel is not conventionally possible; the movement of mass in physical space is always a function of both distance and time. there are extreme edge cases where one visibly has a tug on the other, causing bizarre shit to happen, and the STL/FTL interaction is one of the classic ones

 

[Haim Arlosoroff]

But ALL observers measure the speed of light to be the same. Light always moves halfway between the T and X axes. If the pilot has a different T axis than you do, he must also have a different X axis. Only way he can measure light to have the same velocity as always. His space-axis is X’

I think I have the T-Axis labeled correctly? My question is this, how fast is my relay compared to yours? 1 & 3 occur simultaneously from earth's POV and both before 2 from the ship's POV? Do I have that part right too? Any STL ship would always get the FTL message before it was sent from the ship's POV? As soon as you start with the separate X lines, my head melts.

• Does every faster-than-the-ship message arrive before it was sent, do the speeds together have to exceed the hard limit of propagation/entropy in the universe or just the message?
• How fast (or what is the order of events) does my message take? From Earth's and the STL ship's POV, please.

Now, we’ll imagine an ansible has been invented. An ansible is faster-than-light radio. In fact, it’s instantaneous regardless of the distance between transmitter and receiver. Instantaneous is not really necessary. Any faster than light signaling will do, but it makes the diagrams easier to draw.

Couldn't we just say maybe receding objects have no ability to transmit instantly? Only converging objects? WAIT WAIT WAIT..

3a or 3b for your ansible Thingamabob?
T' is the World-line (I think?) of a converging STL ship moving towards earth. Earth transmits an ansible message at 1 and the STL ship transmitted the message back at 2 instantly after receiving it.

Does it's time-slice move 45 degrees in an autistic manner or the manner of a person who has autism the wrong way too? This shit makes no sense.

If there is a separate 'simultaneous' for each and every fucking object in the cosmos , do STL ships really, FUCKING REALLY have to be moving away to transmit faster than 3a using X' as the "STL ship's space axis"? Please tell me I'm wrong, and I'm stupid.

Does a ship, moving towards the earth FTL message slower than a ship moving away from it?

still, there's always an element of shooting in the dark with this kind of theorizing and I think the way some of this shit, such as the ansible, causes the models to give seemingly impossible output is possibly indicative that the existence of the device itself is impossible. i.e., the reason an ansible creates a time paradox in ICametoLurk's excellent explanation is because at the end of the day you just can't instantaneously transmit signals like that (let's just pretend like quantum entanglement isn't indicating that it might be possible after all). however, the real brainfuck, which I think most people probably understand instinctively, is that sometimes the math looks wrong because our understanding of the mechanics of the universe is incomplete, and it's actually right. the former occurs much more often than the latter, but even so, you'd be surprised how often the latter occurs.

The ansible working along time-slices is what fucks with me, does the direction of motion really force a ship to counterweight its message by moving away from who its talking to?

If I move towards an object then the time slice says my message gets there slower even at C or STL-message buoy than if I was moving away from the earth while I was sending it? Moving away from the earth seems to be making the time-paradox via the STL ship's space axis time-slice head-hurt. That's where I am currently with understanding this. I hope I'm wrong on whole "receding ships transmit faster STL message buoys than approaching ships from Earth's POV" bit.