Theoretically possible inventions you would like to see?

[Rashiminos]

Sure there are theoretical alternatives to general relativity, but name me an alternative to general relativity which contains wormholes which does not reduce to special relativity in the low gravity limit. It would be rather weird, as spacetime, which wormholes are topological features of, is an inherently relativistic concept.

I'm thinking of a (short) bridge between two events (for instance, the same place at two drastically different times) that can be traversed. If I recall correctly, special relativity has some additional stipulations about the kind of events that can be bridged, and the physics around the events. I don't think relativity allows for a wormhole where physical "laws" change between the two events. What are you thinking of, exactly?

You seem to be citing relativity as some sort of necessary condition for wormholes. Support (I would say prove, but that's not what science does) it, or drop language like "inherently."

Spacetime is not inherently a relativistic concept as relativity prescribes various properties of spacetime which are not generally required of a 4-dimensional model. You could argue that a relativistic wormhole concept is the more realistic conception of a wormhole from available evidence, but that's a separate argument from saying the concepts spacetime and wormholes require the concept of relativity. Weirdness is not grounds for prejudice.

What I see here is a semantic argument over the meaning of wormhole, without both of the participants previously having realized the semantic issue. You two may talking of two different things, or at least two different descriptions of the same thing (which does not imply that either is correct nor incorrect).

Edit: and by support it, I mean show me a wormhole found or created through knowledge of the theory of relativity...

If special relativity is false, then general relativity is false as well, as a theory whose approximations are false is also false. In such a case, the theoretical phenomenon of wormholes would be false as well.

No. If the theories were false, it means that the relativistic description of the wormhole's existence is also false. Whether the wormhole exists (or could never exist) for another reason yet remains.

A stool is a stool. It might have 3 legs, or it might have 4. If we can show that it is impossible for the stool to have 4 legs, that would not prove there is no stool, only that there are no 4-legged stools.

Of course, G-man could rename his concept and leave Bill with his precious.

 

[RedRalph]

Are you from Essex county too?

Buh??

 

[El_Machinae]

I dunno. If FTL were theoretically possible (but is currently unknown to human theory), then Fermi's Paradox becomes a lot stranger. As it is, advanced civilizations are still limited in their exponential expansion by the speed of light. With FTL, they'd not be.

 

[The_J]

Flying cars

Boring, they already exist, see here.

 

[SS-18 ICBM]

Is there a strategic bomber in the form of a UAV yet?

 

[Lillefix]

Is there a strategic bomber in the form of a UAV yet?

There's one planned for 2037.

http://en.wikipedia.org/wiki/2037_Bomber

 

[uppi]

Correct me if I'm wrong, but the drive would require either negative matter or negative energy. The former has never been proven to exist. The second, however, has (though only found in very small quantities).

What do you mean with negative energy? Whatever you mean I am pretty sure that it is not the kind of matter/energy needed for such a device.

Yes, I have read the article, thank you. Assuming the calculation is correct, and also assuming that one cannot protect against these extremely high temperatures, Hawking radiation would destroy everything inside the bubble and possibly destabilize the bubble itself once traveling at/over light speed. So far this remains a problem. The point, however, remains. Despite its problems (such as generating the warp bubble itself, or acquiring exotic matter), in theory, the Alcubierre drive could be used for FTL speeds.

No, in theory such a device cannot exist at FTL velocities, because it would destroy itself. Hypothetically, if we were in a universe, where such a thing would be stable, it could be used for FTL travel. However, according to current theory this is impossible in our universe. There is always a chance that the theory is wrong and that it is possible, but if you have rely on the theory being wrong you have left the realm of in theory.

 

[El_Machinae]

For the technology that I think is 'possible' but 'outlandish', I would have to go with shared consciousness.

Right now, I'm 'me' sitting in my jar. With advances in brain understanding and instantaneous communication, we could develop such that I could clone myself and 'share' a consciousness. Both bodies would be 'me'. We already have a version of this, in that we consider both hands to be 'ours', both eyes to be 'ours'. This would merely be extended to multiple bodies in multiple locations.

That, and computer integration of the brain. Memories, calculations, etc. stored digitally and available for subconscious recovery. When I ask you about your mom, a detailed memory is brought to consciousness, even though parts of the memory were stored digitally.

 

[Narz]

How would you access your clone's brain? Wirelessly somehow?

Seems dangerous. If the brain becomes more & more digital &/or wirelessly connected it would also become vulnerable to viruses. Someone could infect you with a torture virus which would give you massive pain until it finally fries your circuits. Worse, it could slow down your processor speed so the torture feels like it's going on & on for ages.

 

[El_Machinae]

Yeah, probably wirelessly for some of it. Similar to how the left and right hemispheres of our brain communicate. It's cheating a bit (because it's ignoring subconscious/brainstem processes) but our two hemispheres are connected by only ~ 200 million neurons with a firing rate of less than 100 firings per second. If we figure a 100x encoding for neuronal firings (reeaaally generous), so that there are 100 'flavours' of firing, then there're roughly 1 trillion bytes per second going between our hemispheres. And that's an incredibly overgenerous estimation.

If we thought about doing that today, though, we'd want some type of hard connection

 

[Rashiminos]

How would you access your clone's brain? Wirelessly somehow?

Seems dangerous. If the brain becomes more & more digital &/or wirelessly connected it would also become vulnerable to viruses. Someone could infect you with a torture virus which would give you massive pain until it finally fries your circuits. Worse, it could slow down your processor speed so the torture feels like it's going on & on for ages.

You use two hands, don't you?

 

[Hehehe]

What do you mean with negative energy? Whatever you mean I am pretty sure that it is not the kind of matter/energy needed for such a device.

Ok then, please enlighten me. But what has been confirmed is, that when two metal plates are pushed together by Casimir effect, it is possible to extract energy from them, and therefore their energy is less than zero. This concept of negative energy is also present in the Hawking radiation of black holes, though experimental support for that is still somewhat lacking as far as I know.

No, in theory such a device cannot exist at FTL velocities, because it would destroy itself. Hypothetically, if we were in a universe, where such a thing would be stable, it could be used for FTL travel. However, according to current theory this is impossible in our universe. There is always a chance that the theory is wrong and that it is possible, but if you have rely on the theory being wrong you have left the realm of in theory.

Using Hawking radiation to prove that FTL travel is impossible in theory is a bit moot point. Hawking radiation kicks in at FTL speeds, so if a sufficiently advanced civilization were to send a spaceship using Alcubierre drive (ignoring all the other problems for a second), and the spaceship would be fried, then that would mean it traveled faster than light, yes?

Warp drives are very interesting configurations in general relativity: At least theoretically, they provide a way to travel at superluminal speeds, albeit at the cost of requiring exotic matter to exist as solutions of Einstein’s equations. However, even if one succeeded in providing the necessary exotic matter to build them, it would still be necessary to check whether they would survive to the switching on of quantum effects. Semiclassical corrections to warp-drive geometries have been analyzed only for eternal warp-drive bubbles traveling at fixed superluminal speeds. Here, we investigate the more realistic case in which a superluminal warp drive is created out of an initially flat spacetime. First of all we analyze the causal structure of eternal and dynamical warp-drive spacetimes. Then we pass to the analysis of the renormalized stress-energy tensor (RSET) of a quantum field in these geometries. While the behavior of the RSET in these geometries has close similarities to that in the geometries associated with gravitational collapse, it shows dramatic differences too. On one side, an observer located at the center of a superluminal warp-drive bubble would generically experience a thermal flux of Hawking particles. On the other side, such Hawking flux will be generically extremely high if the exotic matter supporting the warp drive has its origin in a quantum field satisfying some form of quantum inequalities. Most of all, we find that the RSET will exponentially grow in time close to, and on, the front wall of the superluminal bubble. Consequently, one is led to conclude that the warp-drive geometries are unstable against semiclassical backreaction.

Hawking radiation might make it practically impossible to use such a drive if there is no way to protect against those huge temperatures.

 

[Narz]

You use two hands, don't you?

What chu talkin' 'bout?

 

[Ayatollah So]

I'd like a microwave that doesn't suck.

Get a job and buy one.

First, someone would have to invent a microwave that doesn't suck. One that actually penetrates beyond the first few mm of your food.

 

[SS-18 ICBM]

There's one planned for 2037.

http://en.wikipedia.org/wiki/2037_Bomber

Oh, what's better than a drone raining destruction upon one's enemies?

Hmm, a drone tank would be nice...

 

[uppi]

Ok then, please enlighten me. But what has been confirmed is, that when two metal plates are pushed together by Casimir effect, it is possible to extract energy from them, and therefore their energy is less than zero. This concept of negative energy is also present in the Hawking radiation of black holes, though experimental support for that is still somewhat lacking as far as I know.

Ah, so negative energy means less energy than the vacuum energy (whatever that one is, at this point the theorists start doing really dirty tricks, making any experimentalist cringe and any mathematician scream). So assuming that the vacuum energy really is infinite, we would need to extract an nearly infinite amount of energy from it. That would require a material that almost perfectly reflects any wavelength of the electromagnetic field (I would call it "supermirror" if that term was not already taken). Such a material would be the holy grail of material science and would be able to perform miracles, but unfortunately I can think of several reasons why such a material is probably impossible. However, I begin to see why a theorist who is not concerned with the physical reality might do calculations with these assumptions.

Using Hawking radiation to prove that FTL travel is impossible in theory is a bit moot point. Hawking radiation kicks in at FTL speeds, so if a sufficiently advanced civilization were to send a spaceship using Alcubierre drive (ignoring all the other problems for a second), and the spaceship would be fried, then that would mean it traveled faster than light, yes?


Hawking radiation might make it practically impossible to use such a drive if there is no way to protect against those huge temperatures.

No, the spaceship itself is not the problem (and if you had access to the miracle material mentioned above, shielding against the radiation should be quite easy). No, the keyword here is "unstable" which basically means, that the drive would destroy itself once it begins to go over light speed. So might get a tiny bit above light speed, but only a short amount of time before the drive either goes back to subluminal speeds or spectacularly fails. If physics was consistent (but that is just a guess), the excess over the light speed would fall in the Heisenberg uncertainty window and would thus not even be measurable.

And all this assumes that we have infinite energy at our disposal, while in reality energy is limited at least by the total energy of the universe.

 

[Gamemaster77]

IS it possible to recreate the gills of a fish. And instead of divers having oxygen tanks, they would have a filtering device on their back, so that the could theoretically stay in the water forever.

 

[SS-18 ICBM]

I don't think that's possible. Keep in mind that gills are heavily dependent on CO2-O2 diffusion between two liquids.

It's probably not feasible for a breathing apparatus based on a gaseous phase.

 

[NetGear]

A cel phone that frickin works like its supposed to would be nice for a starter. (dropped calls, 3G coverage, etc)

 

[Hehehe]

Ah, so negative energy means less energy than the vacuum energy (whatever that one is, at this point the theorists start doing really dirty tricks, making any experimentalist cringe and any mathematician scream). So assuming that the vacuum energy really is infinite, we would need to extract an nearly infinite amount of energy from it. That would require a material that almost perfectly reflects any wavelength of the electromagnetic field (I would call it "supermirror" if that term was not already taken). Such a material would be the holy grail of material science and would be able to perform miracles, but unfortunately I can think of several reasons why such a material is probably impossible. However, I begin to see why a theorist who is not concerned with the physical reality might do calculations with these assumptions.

Infinite energy? You just solved all the energy problems then

Exotic matter with negative energy density may be required to stabilize a wormhole. Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time, and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel. See also the Scharnhorst effect.

Of course, the small magnitude of this effect might limit the usefulness of it.

No, the spaceship itself is not the problem (and if you had access to the miracle material mentioned above, shielding against the radiation should be quite easy). No, the keyword here is "unstable" which basically means, that the drive would destroy itself once it begins to go over light speed. So might get a tiny bit above light speed, but only a short amount of time before the drive either goes back to subluminal speeds or spectacularly fails. If physics was consistent (but that is just a guess), the excess over the light speed would fall in the Heisenberg uncertainty window and would thus not even be measurable.

Like I've said, if the calculations are correct and there's no way to avoid it, it might make it practically impossible.

And all this assumes that we have infinite energy at our disposal, while in reality energy is limited at least by the total energy of the universe.

I thought we established this already, the amount of energy required by Alcubierre drive is huge but still finite.