A Step Closer To The Alcubierre Drive!

[Anton P. Nym]

Ah, wait hang on! I see the link! There were some experimental drives that worked on magnetohydrodynamic principles. That's what the Red October was supposed to have used in the book and film of the same name. They're not actually used, because they're desperately slow and inefficient.

To get completely nerd-tastic in the book Red October's super-quiet drive had acoustically-baffled ducted propellers running the length of the boat. Still desperately slow and inefficient (and to the authour's credit, depicted as such) but less Buck-Rodgers-y.

Looking at the drive in that wiki, well, I wouldn't exactly start buying stock in the companies involved myself. The design (if it works...) would be very useful for reaction control on long-duration missions, but with 1N of thrust on 3kW of power it's not going to get spacecraft moving between planets any time soon.

-- Steve

[Scotius]

Oh, i'm not so sure about that. Remember, real life is not like KSP. Such thruster does have almost infinite amount of Isp. It can work as long as it has power and nothing breaks down - for years if needed. Point it in the right direction, start that virtual plasma churning out - and after one year of continuous thrust this ship can leave Dawn and Voyagers in the dust.

[Fractal_UK]

1N of thrust, even for 3KW of input power, is an outrageous amount of thrust, that's really respectable. Attach a large nuclear reactor producing gigawatts and you have many kilonewtons of thrust. With a high density power source like antimatter, you could get continuous 1g acceleration, which is pretty much the holy grail of space travel.

Even without such large power sources, real life isn't KSP, who cares if your burn lasts a month or two, it'll still likely get you to the destination faster than anything available today. Ion engines today are accomplishing interplanetary missions on micronewtons of thrust.

[Wesreidau]

All life on Earth feeds on other life, and Man is a beast of prey. I see no reason to think it is different elsewhere.

[Scotius]

Because alien life elsewhere evolved differently than on Earth? Just because "Eat or be eaten" is prevalent here, it does not mean it's the ultimate rule to which all life conforms.

[magnemoe]

Because alien life elsewhere evolved differently than on Earth? Just because "Eat or be eaten" is prevalent here, it does not mean it's the ultimate rule to which all life conforms.

We can be pretty sure it will as long as its not just plants, yes the system might be different, perhaps most higher animals are omnivores, but the predator role has evolved so many times independently its pretty much an rule.

Also has some issue understanding post you answered to.

However if you are an pure predator with no or very few animals who can be domesticated like in Africa and North and South America you would stay hunter gatherer.

[Seret]

Because alien life elsewhere evolved differently than on Earth? Just because "Eat or be eaten" is prevalent here, it does not mean it's the ultimate rule to which all life conforms.

Of course, we can't be sure. But organisms have to get their energy from somewhere. On Earth almost everything falls into two categories: organisms that get their energy from sunlight, and organisms that get their energy from those ones. It's a very effective evolutionary strategy (look at the metabolic rates of consumers compared to producers). It's reasonable to think it's not unique.

[SargeRho]

Life needs energy. Unless the entire population of life gets its energy from photosynthesis, eat or be eaten will be the rule.

[jwenting]

All life on Earth feeds on other life, and Man is a beast of prey. I see no reason to think it is different elsewhere.

Actually, Man is an omnivore. Just like baboons and other primates, most bears, etc. etc.

[Wahgineer]

-snip of opening post-

Take THAT, KSP FTL haters!

Seriously though, I always wondered why people would rather have a 1000+ part ship that takes either hours worth of gametime to take a ONE WAY TRIP to a star at MAX TIME WARP in KSP, when you can have a 100-165+ part ship take 20-35 minutes one way on 1x time warp, and have cool visuals.

For me, a warp drive in KSP is more practical and sane, even if it may sacrifice a little realism. Also, what is with people saying that just because it's being studied doesn't make it feasible/possible/practical. They (NASA) wouldn't study if it wasn't practical/feasible/possible in the first place! And to boot, saying that implies that every study on different forms of interstellar travel doesn't make them feasible, either!

the whole gist of this post: we can either listen to the STL fanboys who give no exceptions for nonrealism and have computer-melting ships that take hours to get to a star, or listen to the more open m

[m4v]

Also, what is with people saying that just because it's being studied doesn't make it feasible/possible/practical. They (NASA) wouldn't study if it wasn't practical/feasible/possible in the first place! And to boot, saying that implies that every study on different forms of interstellar travel doesn't make them feasible, either!

Experimenting with crazy ideas is sometimes worthwhile, but anybody believing that these experiments will get us closer an alcubierre drive is a fool, until White can get something with negative mass for experiment on the alcubierre drive will never leave the realm of science fiction. Edited October 9, 2013 by m4v

[Dispatcher]

See ya star side!

[-Velocity-]

They (NASA) wouldn't study if it wasn't practical/feasible/possible in the first place!

This is an incorrect assumption. You are assuming that the bureaucrats who assign funding to research projects actually know what they are doing. I am in academia right now, and I've seen a fair share of useless, hopeless research projects. I mean, the money isn't wholly wasted, sometimes some topic or concept that appears useless turns out not to be, or it has an unexpected alternative function/use.

Using a warp drive to exceed the speed of light, allowing for FTL communcation is wholly against the underpinnings of the universe (such as causality), and you can make contradictory impossible situations with FTL communcation. So, it seems that warp drive FTL must be impossible, and we just haven't figured out why yet (however, some researchers have recently claimed that FTL warp drives would be nearly instantly destroyed by Hawking radiation, so maybe that's at least part of why they can't exist). But who knows, maybe there's some small possibility that a warp drive is possible, but you just have to use it to go less than light speed. That would still be very useful.

the whole gist of this post: we can either listen to the STL fanboys who give no exceptions for nonrealism and have computer-melting ships that take hours to get to a star, or listen to the more open m

It's important to be open-minded, but not so open-minded that your brain falls out In more exact terms, be open minded, but use reason to eliminate the impossible and highly unlikely.

Honestly, I'd like to see two options of KSP interstellar travel, a "realistic" mode using very high time compression and things like pulsed fusion drives, and a non-realistic mode using warp drives. That should satisfy everyone and end this silly debate.

Edited October 9, 2013 by |Velocity|

[Drunkrobot]

Experimenting with crazy ideas is sometimes worthwhile, but anybody believing that these experiments will get us closer an alcubierre drive is a fool, until White can get something with negative mass for experiment on the alcubierre drive will never leave the realm of science fiction.

What if these experiments get us closer to something, that then gets us closer to an alcubierre drive? We didn't go from "piece of amber and a feather" straight to "electric turbine", in one step. Science is about observing the universe, performing "useless" experiments, forming models on how the universe works, perform more ambitious experiments, improve the model, THEN do something practical with that knowledge.

Trust me, there is nothing that a good scientist does that doesn't get humanity closer to warp drives, colonies on the Moon, robot servants and jetpacks.

[m4v]

What if these experiments get us closer to something, that then gets us closer to an alcubierre drive? We didn't go from "piece of amber and a feather" straight to "electric turbine", in one step. Science is about observing the universe, performing "useless" experiments, forming models on how the universe works, perform more ambitious experiments, improve the model, THEN do something practical with that knowledge.

Trust me, there is nothing that a good scientist does that doesn't get humanity closer to warp drives, colonies on the Moon, robot servants and jetpacks.

Which is why I said "experimenting with crazy ideas sometimes is worthwhile", the problem here is that they are calling it "warp drive" research and selling it off as if it were feasible technology, when the whole thing depends on the existence of matter with negative mass. Maybe you're okay with wasting NASA's budget in pursuing pipe dreams but I'm not.

[SargeRho]

Actually it doesn't depend on the existence of matter with negative mass. It depends on the ability to create negative energy density in a certain area behind the ship. We know negative energy density is possible already.

[m4v]

Actually it doesn't depend on the existence of matter with negative mass. It depends on the ability to create negative energy density in a certain area behind the ship. We know negative energy density is possible already.

As I understand it, the Casimir effect reduces energy to very small negative levels only in the space between two plates, which are made of normal matter. Since the negative energy is so small and surrounded by normal stuff the net energy is still positive, you need net negative energy for this. Maybe it can be exploited but is all very dubious.

Why don't we see what Alcubierre himself thinks about all this?

Edited October 10, 2013 by m4v

[magnemoe]

This is an incorrect assumption. You are assuming that the bureaucrats who assign funding to research projects actually know what they are doing. I am in academia right now, and I've seen a fair share of useless, hopeless research projects. I mean, the money isn't wholly wasted, sometimes some topic or concept that appears useless turns out not to be, or it has an unexpected alternative function/use.

Using a warp drive to exceed the speed of light, allowing for FTL communcation is wholly against the underpinnings of the universe (such as causality), and you can make contradictory impossible situations with FTL communcation. So, it seems that warp drive FTL must be impossible, and we just haven't figured out why yet (however, some researchers have recently claimed that FTL warp drives would be nearly instantly destroyed by Hawking radiation, so maybe that's at least part of why they can't exist). But who knows, maybe there's some small possibility that a warp drive is possible, but you just have to use it to go less than light speed. That would still be very useful.

It's important to be open-minded, but not so open-minded that your brain falls out In more exact terms, be open minded, but use reason to eliminate the impossible and highly unlikely.

Honestly, I'd like to see two options of KSP interstellar travel, a "realistic" mode using very high time compression and things like pulsed fusion drives, and a non-realistic mode using warp drives. That should satisfy everyone and end this silly debate.

First I do not understand how FLT breaks causality, read about it but don't makes sense to me. Yes traveling with an speed higher than c will also move you backward in time but it impossible for multiple other reasons.

On the other hand an warp drive or quantum entanglement does never travel faster than light, first compress the space time, second don't travel but you have to move the entanglement atoms to target first and it would be hard to use in transmitting information.

However say you could use quantum entanglement for communication, you send an bunch of entangled atoms to Mars for real time communication with an rover. You will have not only a bandwidth restriction but also an fixed amount of data you can transmit. You send an signal to the rover and the rover responds back, it would be no way for the entanglement signal to arrive earlier in time than it was sent so you will not have an grandfather paradox. Say the rover drove off a cliff as the video signal and other high bandwidth data arrives 15 minutes later. You could not undo this, only get the FTL readings from the acceleration sensor at once.

Warp drive probably don't work or is impossible to build for lots of other reasons, but even if you could not travel faster than light with it might be useful.

NASA/ JET has an research program for such low chance/ high payoff projects.

------

Regarding KSP and traveling to other stars. Main weakness with an slower than light star starship is that its engine would make travel inside the solar system a joke, because you can not warp under burn you could not use an low trust/ high isp engine either.

The orion mod lets you reach any body in the system in less than 1-3 month depending on how long you bother to burn and virtual unlimited payload. Yes it would also work as an practical interstellar drive, more so if distances to stars are smaller, no need to have the stars more than 50-100 times the diameter of the solar system anyway.

benefit of an warp/ jump drive is that you avoid overpowered engines. You could also treat the new solar system as an separate level, no need to update the other systems real time, just calculate positions on load, you would only need to simulate items who might get into other SOI.

It will also avoid the inaccuracy you get if you travel very far from the solar system, doing so tend to deorbit things in low orbits.

[K^2]

magnemoe, the problem is with simultaneity in relativity. Order of two events that are space-like separated is frame-dependent. So if according to you event A took place before event B, there can be somebody traveling on a rocket for whom event B came before event A. This isn't a problem when signals travels slower than light. Space-time separated means that two events are too far apart in space and too close together in time for signal from event A to reach event B in time. That means, B cannot be casually related to A. They are independent events, and then it doesn't matter if A comes first or B comes first.

But now, suppose I have means of sending information from one location to another faster than light. Then I can set it up so that A and B are still space-like separated, but A actually triggers B. Furthermore, I can have event A be truly and absolutely random, like a thousandth click of a Geiger Counter, or some other quantum event. Then event B can be something simple, like turning on a light because you got instruction from event A to do so. But now the traveler on the rocket will see the light come on before the Geiger Counter registered its thousandth click. In fact, before the atom that resulted in radiation that produced the click even decayed. And that's a perfectly random process. It cannot be predicted. Yet, if you have faster than light communication, it is predicted by the traveler on the rocket. This is causality violation.

Strictly speaking, it isn't a huge problem, because it can also be resolved via entanglement. But this is something that absolutely requires quantum physics. Classically, it is an impossibility leading to all sorts of bad paradoxes. Of course, all that this tells you is that once you start describing space time with a field theory (General Relativity), you need to be describing the rest of the world from perspective of field theory as well. (E.g., Quantum Field Theory.) The unfortunate side of things is that we do not have mutually consistent field theories to describe both matter and gravity. There are approximations one can do, like QFT in curved space-time, but they do not describe all possibilities. And things like Second-Quantized Gravity just flat out fail. Which is why search for Quantum Gravity, or some alternative (strictly speaking, unified field theory need not be quantum) is so important.

[magnemoe]

K^2: its the frame or rather the restriction I don't get.

Put an clock at the geiger counter at the light and in the rocket.

At 2:00:00 the counter is triggered and send the signal to the light, as the signal goes 100 times faster than light the light goes on say 10 seconds later.

As the rocket is 2 light minutes from the light and 10 from the counter they see the light goes on at 2:02:10 and get the radio signal from the counter at 2:10:00.

However its no way the crew can do anything with the information, they can not call the geiger counter and stop it from triggering the light even with instant communication or any hard paradoxes. Traveling close to the speed of light does not change this except that one signal has to catch up and the other will be intercepted.

And as you say it will not crash the system but will be possible to include in theories.

Feel more like someone take Einstein to far, relativity breaks down with faster than light.

---

regarding fast communications, you can do something with an communication link faster than anybody believes is possible.

Some gamblers managed to scam an club or casino in Florida around world war one.

You could bet on major horse races from other states, the club got the results by telegraph and betting was open until they got the results.

Some guy claimed he could communicate with an ghost at the New York racetrack so he bet at their races just before the telegram came in.

Worked well until the club lost to much and started checking.

Radio in truck on an hill outside the racetrack, it could watch the winner or even the horse who would win outside of accidents. They sent an message to wife at the hotel room who used an smaller transmitter who sent morse signals to the man who used this to bet on.

The telegram was delayed as first the winner had to be verified, result taken to the telegraph room and wait until the message to the club was sent.

[K^2]

Actually, if they have the FTL communication ability on the ship, they can send the signal to the Geiger Counter to tell them that the light has turned on, informing them of said fact before the measurement happens. Because in the ship's coordinate system they see the light go on, but the measurement event has not actually taken place. And if it has not yet taken place, a FTL message can still reach the destination before it does happen.

[Garek]

But that's the part I also don't understand:

say, at 00:00 the geiger triggers and near-instantly triggers the light via FTL communication

at 00:02 the ship sees the light go on and stops the geiger via FTL communication

at 00:10 the ship recieves the measurement from the geiger via lightspeed communication

what exactly makes the stop signal from the ship arrive at the geiger counter before 00:00?

EDIT: to clarify: I don't understand why the fact that a lightspeed signal needs 10 seconds from A to B makes a FTL signal from B to A go 10 seconds back in time? Okay, that doesn't clarify anything but my brain slightly melts when I think about reference frames with different times interacting, so I would be happy if someone could explain this to me

EDIT2: maybe this clarifies the point where I'm confused: I understand that from the perspective of the ship it sends the stop signal before the measurement happened. But why does the order of events as observed by the counter depend on the order of events as observed by the ship?

Edited October 10, 2013 by Garek

[Winter Man]

I always assumed the thing that made FTL violate causality wasn't the fact that something arrived there before light (slower than instantaneous), but that it was an artifact of applying the laws of general relativity to said 'something' and assuming it arrives by travelling the same path as the photon would, forcing it to travel backwards in time. Warp drives have their own separate bubble of space-time and are by default not taking the same route as the photon (unless it's on for the ride in which case it'll get to the destination 'faster than light' too), they're taking a shortcut kind of like, but topologically completely different to how, a wormhole does.

[Kerbart]

Well from warping Photons to a Galaxy class starship should be a small step.

[-Velocity-]

First I do not understand how FLT breaks causality, read about it but don't makes sense to me...

Reposted from like a month and a half ago:

Here's something I wrote up somewhere else, I'll repost it here with some modifications:

Considering that FTL would break causality (allowing time travel to be possible and allowing the universe contradict itself), FTL is impossible. Even if warp drives are possible, the universe must have some way to prevent them from going FTL, otherwise, the basis of our physical reality- causality- breaks down.

There are some relatively simple thought experiments you can perform that proves this to be the case. Imagine a flat bed train car. In the center of the car, there is a light source, a light detector, and a bomb. The light source sends out two beams of light at the same time, one towards the front of the train car, and the other towards the back of the train car. At each end of the train car is a mirror that reflects the light back towards the source/detector/bomb. As the source, detector, and bomb are in the center of the flatbed car, the two beams of light return to and strike the detector at the same time. The detector is configured so that if the return beams of light strike it a different time, the bomb detonates.

Remember that no matter your frame of reference, the speed of light is always measured to be the same. So, we put the flatbed car in motion down the train track, and set up two observers, one observer on a train that is running parallel to the flatbed car, and one observer who is standing on the ground and watching as the train flatbed car passes by.

In the first experiment, we simply fire a beam of light in both directions. Let's say that the flatbed car is moving at 10 m/s down the track on a foggy morning where it is possible to actually see the beams of light as they travel through the air. The observer on the ground sees both beams of light travelling 3x10^8 m/s relative to the landscape upon which he is standing (his inertial reference frame) of course, but relative to the flatbed car above which they are travelling, the beam of light moving in the direction of the car's motion is going 3x10^8 m/s - 10 m/s, and the beam of light going in the opposite direction of the flatbed car's motion is going 3x10^8 m/s + 10 m/s. Thus, the observer on the ground witnesses the beams of light strike the two mirrors at different times. However, on the return trip, the beams of light are now travelling the opposite directions, so the one that was going 10 m/s slower than the speed of light relative to the flatbed car is now going 10 m/s faster than the speed of light relative to the flatbed car, and vice versa. So they make up the "time lost" on the return trip, and end up striking the detector in the center of the flatbed car at the same time. Thus, the bomb does not go off.

In this experiment, the observer travelling on the train that is paralleling the flatbed car and matching its speed sees exactly what you would expect- the beams of light both move at 3x10^8 m/s relative to the flatbed car (which shares his inertial reference frame), the beams of light strike the two mirrors at the same time, and return to strike the detector at the same time, preventing the bomb blast.

So now, let's say that instead of a mirror at each end of the train flatbed car, we have replaced each of the mirrors with a light detector and an instantaneous communicator. Instead of a beam of light returning to the central detector from each end of the flatbed car, an instantaneous signal will be sent.

So, the observer on the train paralleling the flatbed car, sharing the flatbed car's inertial frame of reference, witnesses the two beams of light leave the emitter, travelling at the same speed relative to the flatbed car, strike the detectors at the same time, which sends the instantaneous signals to the central detector at the exact same time, preventing the bomb from detonating.

But now, what does the stationary observer on the ground see? As already stated, he sees the two beams of light travelling at different speeds relative to the flatbed car- the one going in the direction of the flatbed car's motion is going 10 m/s slower than the speed of light relative to the flatbed car, and the one going the opposite direction of the flatbed car's motion is going 10 m/s faster than the speed of light relative to the flatbed car. (But of course, relative to the landscape on which this observer is standing, both beams of light are going the speed of light, 3x10^8 m/s.)

So the observer on the ground sees the beam of light travelling opposite the flatbed car's motion reach the back detector/instantaneous communicator BEFORE the other beam of light arrives at the front detector/instantaneous communicator. The observer on the ground witnesses the two signals from the two instantaneous communicators arrive at different times to the central detector/bomb. The bomb EXPLODES, killing the observer on the train who just witnessed the bomb not explode. What happens when the observer on the train tries to get off the train and shake hands with the guy who just saw him get blown into tiny pieces?

The fact is, the two observers would observe very different things happening, and yet, still be in the same universe with each other. They would be experiencing different realities, yet, be in the SAME reality. How can this be possible? Easy answer: it's not. FTL communication is a fantasy that will never become reality, because the very nature of our reality denies its possibility.

This is why it is impossible to send anything faster than the speed of light. Any such device could be used to create a scenario similar to the one I detailed above. Two observers won't even be able to agree that the same events happened, and will experience different physical realities while being in the same physical reality, which is, obviously, impossible.

But it gets worse. The simplest example, as I give above, using instantaneous communicators, but the exact same thing would happen if they had used tiny warp drive ships operating at 2X the speed of light instead of instantaneous communicators. The chances of FTL travel or communication being possible one day are about the same chance as there actually being a Santa Claus. Less chance, in fact, as flying reindeer are not expressly prohibited by the laws of physics, but FTL IS.

Simply put- warp drives travelling faster than the speed of light are a fantasy, PERIOD, and we have repeated experimental verification of this. We have, time and time again, measured and confirmed that the speed of light is always measured to be 3x10^8 meters per second no matter what your reference frame is!

It might even be that warp drives are POSSIBLE, and it's just that travelling faster than the speed of light with them is impossible. That is, in fact, what some researchers have claimed:

http://www.universetoday.com/28549/warp-drives-probably-impossible-after-all/

Basically- warp drives would be destroyed by Hawking radiation coming off the inside of the warp bubble once they reached the speed of light and tried to exceed it. So no, funding into warp drives is not necessarily wasted. I'm not sure if they are possible or not. If we could use one to go just 20% the speed of light, that would still open up the stars to colonization- they don't have to travel at FTL speeds to be useful!

And finally, I just wanted to add that the speed of light isn't really the speed of light- it's the maximum speed at which two spatially separated events/things can possibly affect each other. Electromagnetism operates at this speed, as does gravity, the strong force, and, (maybe?) the weak force. We really should be calling it the "speed of causality", not the "speed of light". Calling it the "speed of light" defines it much more narrowly than the fundamental limit that it really represents, and helps to contribute to the misguided thinking that it could ever be broken.

Anyway, please consider the above thought experiment, and you will see why FTL communication would violate the very foundations of the universe and reality.

Edited October 10, 2013 by |Velocity|