Astrophysics and Cosmology - Discuss the Universe here

[Agent : Orange]

Hmm, so my brain is still cranking away. Another application would be that the warp bubble should be able to convey information faster than light. In which case individual subatomic particles could be sent out as a sort of Morse code; proton, neutron, proton, neutron, proton, proton or something. Thusly, faster than light communications might be a possible use for it, but dealing with even smaller objects than a nanoprobe or the Enterprise. In other words, if White's work pans out, SETI should be looking for tiny warp bubbles carrying particles travelling through space for evidence of E.T. if such a thing would be detectable (I have no clue if it would be). You probably couldn't figure out their message, but if you see a warp bubble you'd know it's artificial (or would it be? Natural warp bubbles?)

So what do you think the energy requirement for sending a proton in a warp field would be? Is that getting down into manageable energy requirements enough for it to be feasible?

That's a great question. I'm not sure how the energy scales with distance or mass inside the bubble, I will have to take a look at the papers again. In order to produce an effect that small though you will need a full quantum gravity description, again. The device is really a demonstration of principle from GR, so anything below the "macro level" would be more complicated (and open the way ahead for some pretty dramatic research opportunities).

The problem with a communication network based on sending individual particles is that each bubble needs a device associated with it, so you're sending single particles attached to a warp drive, which is not efficient. Though you could make a broadcasting device that will relay a speed of light message once it makes it to a destination using a warp.

Some fraction of observed gamma ray bursts observed today could really be alien warp drives turning on and off millions of years ago due to the big particle and EM flux that comes from them

[zeebo]

...Some fraction of observed gamma ray bursts observed today could really be alien warp drives turning on and off millions of years ago due to the big particle and EM flux that comes from them

That just blew my nerd mind.  I've decided it's so cool I'm going to believe it true until proven otherwise.

[Agent : Orange]

That just blew my nerd mind.  I've decided it's so cool I'm going to believe it true until proven otherwise.

haha

[wr250]

That just blew my nerd mind.  I've decided it's so cool I'm going to believe it true until proven otherwise.

it is both true and false simultaneously.

[SciFiAuthor]

That's a great question. I'm not sure how the energy scales with distance or mass inside the bubble, I will have to take a look at the papers again. In order to produce an effect that small though you will need a full quantum gravity description, again. The device is really a demonstration of principle from GR, so anything below the "macro level" would be more complicated (and open the way ahead for some pretty dramatic research opportunities).

The problem with a communication network based on sending individual particles is that each bubble needs a device associated with it, so you're sending single particles attached to a warp drive, which is not efficient. Though you could make a broadcasting device that will relay a speed of light message once it makes it to a destination using a warp.

Some fraction of observed gamma ray bursts observed today could really be alien warp drives turning on and off millions of years ago due to the big particle and EM flux that comes from them

I see, so to create the warp bubble you must also apply continuous energy to maintain it as you warp your way along. I'm rather odd in that faster than light communications are more important to me than faster than light travel. I want to talk to aliens, not contract VD from one. But the gamma ray idea is intriguing. Well, you know, every time we look at the gamma ray spectrum it seems to toss us some new phenomenon that we have to explain. There may yet come some odd burst where an artificial nature might be more likely than a natural one. They would be expending far more energy for something that might be more feasible than aliens just sending out terrawatts of radio signal just for the hell of it.

I wonder what the effect of a passing warp bubble might be on objects nearby. Could half the earth get dosed with fatal levels of gamma radiation just because some alien prick was speeding when passing through the solar system?

[Agent : Orange]

I see, so to create the warp bubble you must also apply continuous energy to maintain it as you warp your way along. I'm rather odd in that faster than light communications are more important to me than faster than light travel. I want to talk to aliens, not contract VD from one. But the gamma ray idea is intriguing. Well, you know, every time we look at the gamma ray spectrum it seems to toss us some new phenomenon that we have to explain. There may yet come some odd burst where an artificial nature might be more likely than a natural one. They would be expending far more energy for something that might be more feasible than aliens just sending out terrawatts of radio signal just for the hell of it.

I think it's a certain amount of energy that's needed to generate the bubble but you need some way of keeping yourself at the center of it. So if you want to just send a particle you have to stick a particle to the drive itself, otherwise it will wander around and eventually get blasted away when you decelerate. It's a specific configuration and amount of mass that keeps the bubble formed but there's nothing keeping you inside the bubble unless you're actually holding onto the device itself. In other words, getting the required amount of matter in one place will allow you to twist up space-time the way you want it, you just have to make sure that you stay nearby that warp. That's basically how Alcubierre came to his conclusions, he found a solution to the metric and then worked backwards, giving a required matter-energy density (which turns out to be negative). All assuming the bubble could be controlled, of course.

Have you ever read "The Light of Other Days" by Clarke and Baxter? That book is a story about using wormholes for communication and the consequences of a faster than light communications network that is not limited by time or space. A really fascinating story that captured my imagination!

I wonder what the effect of a passing warp bubble might be on objects nearby. Could half the earth get dosed with fatal levels of gamma radiation just because some alien prick was speeding when passing through the solar system?

it sounds like that's what McMonegal, Lewis and O'Byrne were suggesting in their paper (
http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2012/02/MatterOfMatter-revised-final.pdf). They discharge particles from the bubble region like bullets when they decelerate so you have to make sure where you're pointed when you stop. It's as if you let a shock wave go from the bubble itself, accelerating all the particles and dust you picked up on your journey.

[Agent : Orange]

Well since we're speculating about warp drives, let me also throw this out there: Ever heard of a Krasnikov tube before?
http://en.wikipedia.org/wiki/Krasnikov_Tube
The space-time subway system!

Read the original paper here
http://arxiv.org/abs/grqc/9511068
and an extension
http://arxiv.org/pdf/gr-qc/9702049v1.pdf

and a nice (but old!) popular summary about the method here
http://www.npl.washington.edu/AV/altvw86.html

This method of transportation requires that a ship moving near the speed of light establish a warp in space-time as it travels (the "tube"). Then once at the destination the traveller that turns around and goes back through the tube again is sure to exit just after they entered! So this would require you to make a trip to some distant object, spend some time out there and then return to your own world and not the world of the far future, effectively erasing the majority of the round trip travel time. This requires you to have a way of travelling close to the speed of light, though, to make the tube in the first place. It does not eliminate one-way travel time but does eliminate most of the round trip travel time, but ensures a time-like separation on enetering and leaving. This means there are no time paradoxes and you cannot exit the tube before you entered it. Like the Alcubierre solution this type of warp drive also needs exotic (negative) matter to establish the warp. If such a tube could be kept stable then it would act like a subway tunnel through space and time.

[Camazotz Automat]

It does not eliminate one-way travel time but does eliminate most of the round trip travel time, but ensures a time-like separation on enetering and leaving. This means there are no time paradoxes and you cannot exit the tube before you entered it. Like the Alcubierre solution this type of warp drive also needs exotic (negative) matter to establish the warp. If such a tube could be kept stable then it would act like a subway tunnel through space and time.

So, if I understand this, it's similar to my being in a theater watching a movie.  The movie has started, then I tell my date to "watch my seat," which she does so dutifully.

I quickly storm the projector booth and turn off the film and wrestle the projectionist to the floor, applying a sleep hold.

I wait a few minutes until he begins to stir awake, at which point, I dash back to my saved seat.

I ask if I've missed much of the movie... she responds, "well actually, you didn't miss anything. Some kind of technical difficulty. We were all just sitting here for nothing."

Thus I have traveled the movie warp tube.

Am I even close metaphorically, if the movie itself equals space-time?

[SciFiAuthor]

I think it's a certain amount of energy that's needed to generate the bubble but you need some way of keeping yourself at the center of it. So if you want to just send a particle you have to stick a particle to the drive itself, otherwise it will wander around and eventually get blasted away when you decelerate. It's a specific configuration and amount of mass that keeps the bubble formed but there's nothing keeping you inside the bubble unless you're actually holding onto the device itself. In other words, getting the required amount of matter in one place will allow you to twist up space-time the way you want it, you just have to make sure that you stay nearby that warp. That's basically how Alcubierre came to his conclusions, he found a solution to the metric and then worked backwards, giving a required matter-energy density (which turns out to be negative). All assuming the bubble could be controlled, of course.

Three kinds of fascinating, you should write popular science books. You're able to concisely explain it without resorting to equations. I find myself imagining what a harrowing experience travelling in the first warp bubble might be. It might be something like hugging and maintaining an orbit around an artificial black hole that's warping through space, all with the risk that you'll end up tossed off and killed or sucked in and killed.

Have you ever read "The Light of Other Days" by Clarke and Baxter? That book is a story about using wormholes for communication and the consequences of a faster than light communications network that is not limited by time or space. A really fascinating story that captured my imagination!

It's one of the few Clarke stories I haven't read yet, actually. I'll bump it up on the reading list.

it sounds like that's what McMonegal, Lewis and O'Byrne were suggesting in their paper (
http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2012/02/MatterOfMatter-revised-final.pdf). They discharge particles from the bubble region like bullets when they decelerate so you have to make sure where you're pointed when you stop. It's as if you let a shock wave go from the bubble itself, accelerating all the particles and dust you picked up on your journey.

Interesting, a space-time equivalent to a sonic boom.

[Agent : Orange]

So, if I understand this, it's similar to my being in a theater watching a movie.  The movie has started, then I tell my date to "watch my seat," which she does so dutifully.

I quickly storm the projector booth and turn off the film and wrestle the projectionist to the floor, applying a sleep hold.

I wait a few minutes until he begins to stir awake, at which point, I dash back to my saved seat.

I ask if I've missed much of the movie... she responds, "well actually, you didn't miss anything. Some kind of technical difficulty. We were all just sitting here for nothing."

Thus I have traveled the movie warp tube.

Am I even close metaphorically, if the movie itself equals space-time?

Hey actually that's pretty good! Then the movie itself is time and the distance you travel is between your seat and the projection booth

[SciFiAuthor]

Well since we're speculating about warp drives, let me also throw this out there: Ever heard of a Krasnikov tube before?
http://en.wikipedia.org/wiki/Krasnikov_Tube
The space-time subway system!

Read the original paper here
http://arxiv.org/abs/grqc/9511068
and an extension
http://arxiv.org/pdf/gr-qc/9702049v1.pdf

and a nice (but old!) popular summary about the method here
http://www.npl.washington.edu/AV/altvw86.html

This method of transportation requires that a ship moving near the speed of light establish a warp in space-time as it travels (the "tube"). Then once at the destination the traveller that turns around and goes back through the tube again is sure to exit just after they entered! So this would require you to make a trip to some distant object, spend some time out there and then return to your own world and not the world of the far future, effectively erasing the majority of the round trip travel time. This requires you to have a way of travelling close to the speed of light, though, to make the tube in the first place. It does not eliminate one-way travel time but does eliminate most of the round trip travel time, but ensures a time-like separation on enetering and leaving. This means there are no time paradoxes and you cannot exit the tube before you entered it. Like the Alcubierre solution this type of warp drive also needs exotic (negative) matter to establish the warp. If such a tube could be kept stable then it would act like a subway tunnel through space and time.

That's a new one on me, it reminds me of a new slant on Sagan's "Contact". I'm particularly floored by the idea that Krasnikov tubes offer a possible solution to the Fermi Paradox. I presume this method would require less energy/mass than the alcubierre drive? Or would you need a very large amount of exotic matter?

Still though, relativistic space has it's uses. It's a perfect alternative to cryonics. Just load the terminally ill onto near-speed of light transport ships, go out to mid-point of however many light years you think the human race needs to cure their diseases, flip the ship around and go home. Voila. And it would be considerably more fun than spending centuries frozen in liquid nitrogen.

[Camazotz Automat]

Hey actually that's pretty good! Then the movie itself is time and the distance you travel is between your seat and the projection booth

What makes my metaphor somewhat nostalgic is using a projector/photons in the equation.

But that poor projectionist.

However, it's all in the name of science, so I'm good!

[Agent : Orange]

Three kinds of fascinating, you should write popular science books. You're able to concisely explain it without resorting to equations. I find myself imagining what a harrowing experience travelling in the first warp bubble might be. It might be something like hugging and maintaining an orbit around an artificial black hole that's warping through space, all with the risk that you'll end up tossed off and killed or sucked in and killed.

If I had the time I would like to try some writing, I think it would be a lot of fun. I have many ideas but other than technical work I haven't had much luck getting anything set down.

It's one of the few Clarke stories I haven't read yet, actually. I'll bump it up on the reading list.

Would be interested to hear your thoughts on it. I really loved the development of the story as I worked my way through it. Things were really excellently set up and taken to their logical conclusions in creative and interesting ways.

Interesting, a space-time equivalent to a sonic boom.

Not quite, all of the stuff that gets blown out of the bubble is pretty much picked up on the way, so your warp bubble gets "loaded" with shrapnel like dust, ions, subnuclear bric-a-brac as you go. Then once you stop all of that stuff gets a big acceleration in the direction of motion of your bubble. Electromagnetic radiation can get into the bubble and it gets badly blueshifted on the way through, making problems for anyone within. The big problem with the alcubierre drive is that it seems you can't get any signals out when you are traveing with a superluminal velocity. I should also say I don't think you can make the literal equivalent of a sonic boom because that requires exceeding c in the vacuum. 

BUT you ask a very interesting question here. Does the bubble also create and scatter gravity waves and can those be red/blue shifted by it's motion as well? There might be big gravitational wave flux as well from using one of these. When I get some free time I might go over McMonigal Lewis O'Byrne paper and try to find the answer to this. It's neither a static nor stationary metric so I would expect gravitational waves should be generated from it but I don't have any feeling for how they would behave.

Interesting questions.

[SciFiAuthor]

So the "What if?" question that ran through my head this time is "What if the warp bubble carrying the Enterprise passes through the positron ejecta of that weird antimatter fountain near the center of the Milky Way?"

http://www.spacetoday.org/DeepSpace/Galaxies/MilkyWay/Antimatter.html

Granted that the positrons are diffuse, but barring that and saying the Enterprise passes though a dense knot of them carrying the flotsam collected around the warp field, what might happen? Incinerated Mr. Spock? Or is he safe? Where would the energy from annihilation go? Does the unlucky Andorian that happens to be near where the Enterprise passed through the positron cloud deal with the effects of that jackass William Shatner warping his ship through it?

Or, might one use a dense area of the positron cloud to provide the energy to slow or stop the warp bubble? Pass close to the source and then it stops. I'm sure that would be fatal to those inside, but I'm speaking hypothetically.

[zeebo]

Hey guys after you get the warp bubble issue squared away, here's some more food for thought for y'all.  Who knows, maybe you can figure some of these out in your spare time.   

http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

[SciFiAuthor]

Hey guys after you get the warp bubble issue squared away, here's some more food for thought for y'all.  Who knows, maybe you can figure some of these out in your spare time.   

http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

Some of those are going to be harder than others. So while Orange will fly in with a superman P emblazoned on his chest and use his voodoo powers of physics to solve them over coffee, and I drunkenly stumble in with my outdated E turned A slathered on my chest in ketchup and ask random weird and quasi-irrelevant questions, the real answers lie with Hoagland. It's in the data, just look at the data. It's Data's head Jorch. Data's head!

[Agent : Orange]

I find myself imagining what a harrowing experience travelling in the first warp bubble might be. It might be something like hugging and maintaining an orbit around an artificial black hole that's warping through space, all with the risk that you'll end up tossed off and killed or sucked in and killed.

Should also add that space inside the bubble wall is as flat as outside the wall, so the 4-velocity of observers inside (at the center, anyway) as well as outside is the same. I think the wall is taken as thin in these papers too. Anyway that means no need to hang on for dear life, riding the warp bubble is as easy as sitting around in flat space as long as you sit at the center. That's why there's no time dilation for the party inside the bubble. It's like when you make the bubble you take a little piece of flat space-time that you started with along with you, that makes the inside of the bubble. Assuming you start in a flat spacetime.

So the "What if?" question that ran through my head this time is ...
... use a dense area ... plasma...

A few initial thoughts come to mind.

First off, it would be nice to see the paths of light rays and material particles entering and interacting with the bubble walls. The MLO paper does the calculation in 1D, but there's no reason why it couldn't be done in two, taking the xy plane through the center of the bubble. It's symmetric anyway so this is easy to code. Then use a 4th order runge-kutta scheme to integrate the light ray paths, the null geodesics and color them according to their gravitational doppler shift. Then do this for a set of time steps t and you get a little movie of what happens when photons run into a warp bubble. You can do it also for material particles on time-like paths. So then you get a visual representation of the situation, where particles gather and bunch up and what they do for various cases of the bubble speed (sub and super luminal). That would be pretty interesting and give a good intuition of how these things behave.

Then you could assume that space is full of plasma, take the simplest case of electrons and their antiparticles. Say the plasma is at a constant densty initially to keep things simple. As the bubble moves around, this plasma should gather around the bubble wall. It's more complicated because the bubble is no longer in vacuum so the equations would get more complicated but it would also be more realistic too. In fact, this would model the case above but taking particle density as continuous instead of discrete. It's interesting because it's known that photons have an effective mass when they travel through plasma (http://adsabs.harvard.edu/abs/1992PhRvD..45..525K). So how does this change the dynamics? And since it's moving through a plasma no photons lower than the plasma frequency can propagate so you would find in this case the photon flux inside the bubble is lower than the vacuum case. 

It's also interesting to think that if the wall collects plasma and miscellany as it goes then that will build up over time and eventually the external space won't be flat anymore around the bubble. What does that mean, and can it disrupt the bubble wall? If so then the range of any such bubble might be limited by the amount of material it can carry. I'd expect this to be huge because it takes a lot of energy to make the bubble in the first place.

The last two scenarios are much more complicated than the first, which I do think could be done with not much difficulty at all for someone that can numerically solve systems of coupled differential equations.

Hey guys after you get the warp bubble issue squared away, here's some more food for thought for y'all.  Who knows, maybe you can figure some of these out in your spare time.   

http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

That list is both terrifying and exciting at the same time.

[Tarbaby]

Crystallized Plutocrat (sorry, I just can't seem to memorize your alias): the problem with your metaphor is… I don't think Sleep holds our legal.

[SciFiAuthor]

Should also add that space inside the bubble wall is as flat as outside the wall, so the 4-velocity of observers inside (at the center, anyway) as well as outside is the same. I think the wall is taken as thin in these papers too. Anyway that means no need to hang on for dear life, riding the warp bubble is as easy as sitting around in flat space as long as you sit at the center. That's why there's no time dilation for the party inside the bubble. It's like when you make the bubble you take a little piece of flat space-time that you started with along with you, that makes the inside of the bubble. Assuming you start in a flat spacetime.

Aw man, can't you cook the numbers or something to add in some turbulence? It won't pass peer review, but the sci fi stories will be more fun. But it does create a question, what would the effect of nearby gravity sources be on the warp bubble? In other words, if a ship in warp bubble passes near a star, does the star's gravitational pull 1. draw the ship in the warp bubble out of the warp bubble or 2. does the warp bubble deviate along with the curve in normal space-time and the ship remain in the center due to the space-time in the bubble also warping from the gravity? This would be interesting to know, since it might provide a way of steering the warp bubble via gravity assist maneuvers or alternatively stopping the ship by bringing it out of the bubble if such a thing would be survivable.

Another thought comes to mind in regards to the flotsam the warp bubble picks up on the way. Does this flotsam actually enter the warp bubble, or adhere to it's surface or inside the wall, or does it collect in front of it? If it collects in front of it, or adheres to the surface, then wouldn't that material be in violation of the constancy of c given that the material is not within the warp bubble itself? Or might it prevent the warp bubble itself from ever exceeding c?

First off, it would be nice to see the paths of light rays and material particles entering and interacting with the bubble walls. The MLO paper does the calculation in 1D, but there's no reason why it couldn't be done in two, taking the xy plane through the center of the bubble. It's symmetric anyway so this is easy to code. Then use a 4th order runge-kutta scheme to integrate the light ray paths, the null geodesics and color them according to their gravitational doppler shift. Then do this for a set of time steps t and you get a little movie of what happens when photons run into a warp bubble. You can do it also for material particles on time-like paths. So then you get a visual representation of the situation, where particles gather and bunch up and what they do for various cases of the bubble speed (sub and super luminal). That would be pretty interesting and give a good intuition of how these things behave.

Go for the gusto, what happens if the warp bubble impacts a planet? But I suppose this would answer my above question. The particles presumably enter the wall and no longer are in normal space-time, and your calculation movie would illustrate how that process unfolds. 

Then you could assume that space is full of plasma, take the simplest case of electrons and their antiparticles. Say the plasma is at a constant densty initially to keep things simple. As the bubble moves around, this plasma should gather around the bubble wall. It's more complicated because the bubble is no longer in vacuum so the equations would get more complicated but it would also be more realistic too. In fact, this would model the case above but taking particle density as continuous instead of discrete. It's interesting because it's known that photons have an effective mass when they travel through plasma (http://adsabs.harvard.edu/abs/1992PhRvD..45..525K). So how does this change the dynamics? And since it's moving through a plasma no photons lower than the plasma frequency can propagate so you would find in this case the photon flux inside the bubble is lower than the vacuum case. 

The warp bubble travelers won't be able to listen to Jorch! If MV reads this, he'll have a warp bubble developed and enveloping bellgab within a week. Yes, it would be more realistic and interesting. Unfortunately the photon flux inside the bubble, while lower, would still all be high energy photons. As I understand it, while you couldn't look outside, you'd still get outside's dangerous radiation.

To go out into the weeds, if you ram the warp bubble into a star, then wouldn't the interior be thermally insulated? If the gravity doesn't collapse the warp field, and assuming the density of the matter surrounding it wouldn't be a problem, then one could theoretically create a warp bubble probe and explore the interior of the sun. I know this one's a bit "do you think asteroids have a brain?" but I'll toss it out there anyway.

It's also interesting to think that if the wall collects plasma and miscellany as it goes then that will build up over time and eventually the external space won't be flat anymore around the bubble. What does that mean, and can it disrupt the bubble wall? If so then the range of any such bubble might be limited by the amount of material it can carry. I'd expect this to be huge because it takes a lot of energy to make the bubble in the first place.

This is why I ask if the material would violate c in some way if it's interacting with normal space still and prevent the bubble from ever going superluminal.

[SciFiAuthor]

If I had the time I would like to try some writing, I think it would be a lot of fun. I have many ideas but other than technical work I haven't had much luck getting anything set down.

That's always the biggest problem: time. Most authors will say that you have to write 6 hours a day, 7 days a week to make it. It's not true. Start with 15 minutes a day. It might take years to complete a novel, but James Joyce took 7 years to write Ulysses. Arthur Clarke's other main collaborator Gentry Lee does that, he's also the chief engineer for the Planetary Flight Systems Directorate at JPL. Asimov, somehow, managed to maintain a professorship in biochemistry at Boston University and somehow manage to be one of the most prolific authors of all time. I guess the key is if one finds writing to be fun and not work.

Would be interested to hear your thoughts on it. I really loved the development of the story as I worked my way through it. Things were really excellently set up and taken to their logical conclusions in creative and interesting ways.

Won't take long. I usually kill at least one book a week, usually two and I'm extremely tired of reading horror novels. My project right now is an attempt at sci-fi horror, so horror's all I've read for the last six months. I could use the break.

Not quite, all of the stuff that gets blown out of the bubble is pretty much picked up on the way, so your warp bubble gets "loaded" with shrapnel like dust, ions, subnuclear bric-a-brac as you go. Then once you stop all of that stuff gets a big acceleration in the direction of motion of your bubble. Electromagnetic radiation can get into the bubble and it gets badly blueshifted on the way through, making problems for anyone within. The big problem with the alcubierre drive is that it seems you can't get any signals out when you are traveing with a superluminal velocity. I should also say I don't think you can make the literal equivalent of a sonic boom because that requires exceeding c in the vacuum.

Sure, c and cAir are different phenomena, but if the matter collected in the wall were not in normal space, but returned to normal space when the warp bubble stopped, they would propagate forward below c, and would remain scrunched up like a sonic boom does as the sound waves propagate outward from the aircraft. It's certainly not literal, of course, but perhaps radiation boom might be a coinable phrase.

BUT you ask a very interesting question here. Does the bubble also create and scatter gravity waves and can those be red/blue shifted by it's motion as well? There might be big gravitational wave flux as well from using one of these. When I get some free time I might go over McMonigal Lewis O'Byrne paper and try to find the answer to this. It's neither a static nor stationary metric so I would expect gravitational waves should be generated from it but I don't have any feeling for how they would behave.

In which case a ship traveling through space would be detectable by its shifted gravitational waves (along with the apparent source of the waves appearing to move faster than light). Since gravitational waves are thought to be detectable and we're already looking for them now, it might be the case that the Alcubierre drive is detected or disproven within our lifetimes before even figuring out the physics. We would either see the effects of alien warp drives or not with an interferometer, maybe even Advanced LIGO.

There's totally a sci-fi story in that. Two researchers having a love affair working at an interferometer that's threatened with having its funds yanked discovering the signature of a warp field. It becomes big news, they get famous, conflict occurs worldwide as the implications are debated. The researchers keep on with studying the phenomena and determine the direction it was moving, and end the book with the answer: it's coming directly towards us.

[jazmunda]

[zeebo]

More warp drives firing off!  Ok ... possibly.

http://phys.org/news/2014-07-radio-burst-discovery-deepens-astrophysics-mystery.html

[Agent : Orange]

More warp drives firing off!  Ok ... possibly.

http://phys.org/news/2014-07-radio-burst-discovery-deepens-astrophysics-mystery.html

Those fast radio bursts are really interesting because the mechanisms behind the radio emission of pulsars is not well understood at all. The article also mentions magnetars which are incredible in every way. I'm guessing these are in some way related to neutron stars or some other kind of compact object.

[Agent : Orange]

Aw man, can't you cook the numbers or something to add in some turbulence? It won't pass peer review, but the sci fi stories will be more fun. But it does create a question, what would the effect of nearby gravity sources be on the warp bubble? In other words, if a ship in warp bubble passes near a star, does the star's gravitational pull 1. draw the ship in the warp bubble out of the warp bubble or 2. does the warp bubble deviate along with the curve in normal space-time and the ship remain in the center due to the space-time in the bubble also warping from the gravity? This would be interesting to know, since it might provide a way of steering the warp bubble via gravity assist maneuvers or alternatively stopping the ship by bringing it out of the bubble if such a thing would be survivable.

Another thought comes to mind in regards to the flotsam the warp bubble picks up on the way. Does this flotsam actually enter the warp bubble, or adhere to it's surface or inside the wall, or does it collect in front of it? If it collects in front of it, or adheres to the surface, then wouldn't that material be in violation of the constancy of c given that the material is not within the warp bubble itself? Or might it prevent the warp bubble itself from ever exceeding c?

Go for the gusto, what happens if the warp bubble impacts a planet? But I suppose this would answer my above question. The particles presumably enter the wall and no longer are in normal space-time, and your calculation movie would illustrate how that process unfolds. 

The warp bubble travelers won't be able to listen to Jorch! If MV reads this, he'll have a warp bubble developed and enveloping bellgab within a week. Yes, it would be more realistic and interesting. Unfortunately the photon flux inside the bubble, while lower, would still all be high energy photons. As I understand it, while you couldn't look outside, you'd still get outside's dangerous radiation.

To go out into the weeds, if you ram the warp bubble into a star, then wouldn't the interior be thermally insulated? If the gravity doesn't collapse the warp field, and assuming the density of the matter surrounding it wouldn't be a problem, then one could theoretically create a warp bubble probe and explore the interior of the sun. I know this one's a bit "do you think asteroids have a brain?" but I'll toss it out there anyway.

This is why I ask if the material would violate c in some way if it's interacting with normal space still and prevent the bubble from ever going superluminal.

All good questions, it looks like the alcubierre metric has only been considered in the flat case with euclidean space in the bubble exterior and interior. The difficulty of some of these problems are that they involve the 2-body interaction, which is difficult to solve in GR at all. You usually have to go to a method called a post-Newtonian parameterization which chops up GR into small corrections that are added to Newton's mechanics to make it approximate GR, so even calculating the details of stellar collisions in full GR can be difficult. I have no real intuition for what would happen to the bubble in any of the cases that involve external interactions. I would guess that the bubble itself is small so you can treat it like a test particle in the field of the Sun. It also requires a specific matter density to establish so if you mess with that density distribution too much then the field should decay and you will begin to decelerate. Material particles can gather in the walls of the bubble but they are not perfectly confined there like a ram, they can pass through as well. So jumping into the Sun with one of these things wouldn't change the result much. Also the real difficulty is in getting a signal from the center of the bubble to the outside, which is what makes steering and controlling the bubble so difficult.

And you will be happy to know that the region of flat space inside the bubble varies as a function of bubble-wall width, and White's modification that NASA is testing involves shrinking the energy requirements by making the walls of the bubble thicker. Only at the very center there will be no gravitational effects... so practical warp drive may have you hanging on after all.

[Agent : Orange]

http://en.wikipedia.org/wiki/David_Berkowitz

Sorry I went so dark

[zeebo]

Hey Agent, the cosmologist on c2c tonite said that they've determined the shape of the cosmos is in fact flat (not spherical or saddle-shaped).   I didn't realize that'd been figured out. 

She also said they know it's infinite as well, so out beyond the edge of the observable universe it just goes on forever. 

Is this right and if so, how do they know?  ( If you can't answer w/o taking too much of your time or writing eighteen pages of equations, please disregard my question.    )

[SciFiAuthor]

Hey Agent, the cosmologist on c2c tonite said that they've determined the shape of the cosmos is in fact flat (not spherical or saddle-shaped).   I didn't realize that'd been figured out. 

She also said they know it's infinite as well, so out beyond the edge of the observable universe it just goes on forever. 

Is this right and if so, how do they know?  ( If you can't answer w/o taking too much of your time or writing eighteen pages of equations, please disregard my question.    )

I heard that and wondered "ok, but, if it goes on forever then what is space-time expanding into?"

I don't care that matter distribution is expanding, I care that space-time is expanding. We can look out and see pretty early into the universe's history. There must be a demarcation line between the line of the big bang's expansion and the line of space-time expansion. Sure, she might mean that if you head out in any direction and cross the universe you'll end up back at the same point. But that's unsatisfying. The rules in the bubble bring you back to where you started, but that doesn't mean that you're not in a bubble.

[Agent : Orange]

It's true it has been measured to be flat within a very large degree by observations of the CMB. This means the matter and energy density is very close to the critical density to keep the universe from collapsing back in on itself. So the question why is it this specific value became very curious and the way out of a "natural-ness" problem is to have something like inflation happen in the early universe. The side effects of inflation may have already been seen in the BICEP2 observations but now these observations are being called into question (rightly so). We've known since the late 90s that the Universe is accelerating and this adds a new wrinkle to our understanding of the shape of the Universe. Which is a whole other topic...

We are limited in what we can see of the Universe because of the speed of light, we can only see events from a certain distance away because it takes light a finite time to get to us. So when we talk about the Universe we really mean the observable Universe which is basically a globe centered on the observer. The boundary is defined by the cosmic microwave background and has a redshift of around 1100. It is this patch of Universe - within this bubble - that we measure to be flat. It's thought the Universe is a lot bigger than this but since we are causally disconnected from regions outside they cannot affect us since we can't get any influence from them due to the finite speed of light. So it's not known what the topology of the larger Universe is, but inflation suggests that it is finite but unbounded - possibly like the surface of a large sphere. Our flat looking patch is then just a very close up "view" of a part of this expanding bubble.


Hope that was not too long winded

[Agent : Orange]

I heard that and wondered "ok, but, if it goes on forever then what is space-time expanding into?"

I don't care that matter distribution is expanding, I care that space-time is expanding. We can look out and see pretty early into the universe's history. There must be a demarcation line between the line of the big bang's expansion and the line of space-time expansion. Sure, she might mean that if you head out in any direction and cross the universe you'll end up back at the same point. But that's unsatisfying. The rules in the bubble bring you back to where you started, but that doesn't mean that you're not in a bubble.

Since it's accelerating and expanding you'd never be able to reach beyond the local horizon even if you left at the speed of light today! You're stuck within our local observable part of the Universe.

And you can't say it's expanding into anything! All time and space are measured with respect to the big bang, so the best we can imagine is that it's expanding like a surface. Sorry I can't get more in depth right now (gotta get in to work!) but this article looks interesting and says what I was trying to in a short period of time.

http://www.universetoday.com/1455/podcast-what-is-the-universe-expanding-into/

[Camazotz Automat]

Crystallized Plutocrat (sorry, I just can't seem to memorize your alias): the problem with your metaphor is… I don't think Sleep holds our legal.

I don't know if they are legal or not across the land, but they have certainly been known to be incorrectly applied by lawn enforcement wherein they crushed the front of the throat instead of applying pressure only to the sides of the neck.

I could upgrade my metaphorical equation and use a taser on that godless projectionist.

Whatever it takes to make sure science marches on. If we're ever going to get off planet, some people are just going to have to straighten up, else we'll be carrying surly projectionists throughout the cosmos like a flickering plague.

The phrase "Crystallized Plutocrat" is pretty damned nifty, btw. I will try not to steal it. But I'm not making any promises.