3 ms·

I don't get the excitement for the Alcubierre drive. It requires negative mass, something that doesn't exist. (It's not like dark matter, something we know ex

I don't get the excitement for the Alcubierre drive. It requires negative mass, something that doesn't exist. (It's not like dark matter, something we know exists but don't understand -- it is something that we have no evidence for its existence at all.) I feel like they were just playing with models, entered a nonsensical value (negative value for mass), and discovered a warp drive. If you're going to do that, just enter negative time and invent time travel while you're at it.

JumpCrisscross 5y ago
> negative mass, something that doesn't exist We don’t know this. And this isn’t a “can’t prove a negative” argument. The origin of mass is frontier physics. More directly, one can explore why negative mass is needed, and whether there are other phenomena that produce that effect. Worst case: the math is interesting.
WJW 5y ago
It's not so strange to understand the excitement when you think about how many people would really REALLY like FTL travel to be possible. Not only does it invoke romantic ideas about exploring the stars and lets people dream about becoming captain of their own starship on day, it also helpfully distracts from having to confront the extremely difficult social issues that hinder saving the Earth from it's myriad problems. Without FTL you take all those dreams away, so it's no wonder people are extremely interested in anything that even looks like a "solution".
zionic 5y ago
Does it require negative _mass_ or negative space-time compression? We know gravity waves exist, so space time can oscillate between 0 and N where N is positive right? Are we so sure there is not a -N < 0 < N? Not even close to an expert in this stuff.
mabbo 5y ago
They explain part of that in the article > Today, however, it’s recognized that what’s needed isn’t necessarily negative mass or negative energy; that was simply the way that Alcubierre recognized one could induce the needed “opposite type” of curvature to space from what normal mass or energy causes. There's other options, and also we aren't 100% certain negative mass/energy can't exist (but probably not...) Edit: changed my tone because I was being a snarky jerk.
otrahuevada 5y ago
It does not need /negative matter/ or energy, though. What is needed, in the original, non-scammer-friendly version by Alcubierre is /something/ that can push spacetime in the opposite direction that mass and energy do. At least the original Alcubierre solution, he basically lays out the mechanism and says, paraphrasing: "hey, the numbers do work out. We just need something that doesn't make sense, or something that makes /the thing/ happen" We see then that, just as it happens with wormholes, one needs exotic matter to travel faster than the speed of light. However, even if one believes that exotic matter is forbidden classically, it is well known that quantum field theory permits the existence ofregions with negative energy densities in some special circumstances (as, for example, inthe Casimir effect [4]). The need of exotic matter therefore doesn’t necessarily eliminate the possibility of using a spacetime distortion like the one described above for hyper-fast interstellar travel. https://arxiv.org/pdf/gr-qc/0009013.pdf https://arxiv.org/pdf/gr-qc/0009013.pdf The excitement here is partly due to the fact that this is both a trekkie thing and one that was previously not even supposed to numerically make sense. It's likely this "not requiring any specific fringe-physics thing" is what is causing the idea to catch on and continue to be ellaborated, because having specificed this mechanics well enough, then maybe and only maybe it might be possible to cause at least an analogue of it to exist and that'd be awesome.
- BizarroLand 5y ago
  Any real warp drive is going to be kind of like setting off a bomb in the middle of a lake and then surfing the water to the center on a jetski, and hoping you can jump off the jetski before you hit the other stuff that is also rushing in with the water on the other side.
Maursault 5y ago
> It's not like dark matter, something we know exists but don't understand No one knows that dark matter exists, as it is only hypothesized. It is quite possible that dark matter does not exist.
dogma1138 5y ago
We don’t know that Dark Matter exists other than we know there is (a lot of) mass missing which is needed to reconcile our observations (or we need to modify our theories around gravity which is where things like MOND come into play). Dark Matter is just a placeholder term for that missing mass with a lot of candidates ranging from normal (baryonic) matter to more and more exotic things. Negative mass does not contradict existing theories such as the standard model in fact it’s somewhat built into them. But overall yes we haven’t found any evidence of it actually existing we know that anti matter (probably one of the best candidates for it) has positive inertial mass from experimentation we didn’t experimentally proven that it’s gravitational mass is also positive but it most likely is as if it isn’t it would be probably the most interesting discovery since it would violate the equivalence principle. In general you’ll find people getting excited about any possibility for an FTL means of transport since otherwise we are unlikely to ever be able to explore the universe with anything other than telescopes. I fore one hope that we do find a way around the pesky speed limit because if not it seems that it’s quite a bit of waste of space otherwise.
BreakfastB0b 5y ago
Tell me you didn’t read the article without telling me you didn’t read the article. The paper uses the Casimir effect to avoid the need for negative mass.

JumpCrisscross 5y ago

> negative mass, something that doesn't exist We don’t know this. And this isn’t a “can’t prove a negative” argument. The origin of mass is frontier physics. More directly, one can explore why negative mass is needed, and whether there are other phenomena that produce that effect. Worst case: the math is interesting.

WJW 5y ago

It's not so strange to understand the excitement when you think about how many people would really REALLY like FTL travel to be possible. Not only does it invoke romantic ideas about exploring the stars and lets people dream about becoming captain of their own starship on day, it also helpfully distracts from having to confront the extremely difficult social issues that hinder saving the Earth from it's myriad problems. Without FTL you take all those dreams away, so it's no wonder people are extremely interested in anything that even looks like a "solution".

zionic 5y ago

Does it require negative _mass_ or negative space-time compression? We know gravity waves exist, so space time can oscillate between 0 and N where N is positive right? Are we so sure there is not a -N < 0 < N? Not even close to an expert in this stuff.

mabbo 5y ago

They explain part of that in the article > Today, however, it’s recognized that what’s needed isn’t necessarily negative mass or negative energy; that was simply the way that Alcubierre recognized one could induce the needed “opposite type” of curvature to space from what normal mass or energy causes. There's other options, and also we aren't 100% certain negative mass/energy can't exist (but probably not...) Edit: changed my tone because I was being a snarky jerk.

otrahuevada 5y ago

It does not need /negative matter/ or energy, though. What is needed, in the original, non-scammer-friendly version by Alcubierre is /something/ that can push spacetime in the opposite direction that mass and energy do. At least the original Alcubierre solution, he basically lays out the mechanism and says, paraphrasing: "hey, the numbers do work out. We just need something that doesn't make sense, or something that makes /the thing/ happen" We see then that, just as it happens with wormholes, one needs exotic matter to travel faster than the speed of light. However, even if one believes that exotic matter is forbidden classically, it is well known that quantum field theory permits the existence ofregions with negative energy densities in some special circumstances (as, for example, inthe Casimir effect [4]). The need of exotic matter therefore doesn’t necessarily eliminate the possibility of using a spacetime distortion like the one described above for hyper-fast interstellar travel. https://arxiv.org/pdf/gr-qc/0009013.pdf https://arxiv.org/pdf/gr-qc/0009013.pdf The excitement here is partly due to the fact that this is both a trekkie thing and one that was previously not even supposed to numerically make sense. It's likely this "not requiring any specific fringe-physics thing" is what is causing the idea to catch on and continue to be ellaborated, because having specificed this mechanics well enough, then maybe and only maybe it might be possible to cause at least an analogue of it to exist and that'd be awesome.

BizarroLand 5y ago
Any real warp drive is going to be kind of like setting off a bomb in the middle of a lake and then surfing the water to the center on a jetski, and hoping you can jump off the jetski before you hit the other stuff that is also rushing in with the water on the other side.

Maursault 5y ago

> It's not like dark matter, something we know exists but don't understand No one knows that dark matter exists, as it is only hypothesized. It is quite possible that dark matter does not exist.

dogma1138 5y ago

We don’t know that Dark Matter exists other than we know there is (a lot of) mass missing which is needed to reconcile our observations (or we need to modify our theories around gravity which is where things like MOND come into play). Dark Matter is just a placeholder term for that missing mass with a lot of candidates ranging from normal (baryonic) matter to more and more exotic things. Negative mass does not contradict existing theories such as the standard model in fact it’s somewhat built into them. But overall yes we haven’t found any evidence of it actually existing we know that anti matter (probably one of the best candidates for it) has positive inertial mass from experimentation we didn’t experimentally proven that it’s gravitational mass is also positive but it most likely is as if it isn’t it would be probably the most interesting discovery since it would violate the equivalence principle. In general you’ll find people getting excited about any possibility for an FTL means of transport since otherwise we are unlikely to ever be able to explore the universe with anything other than telescopes. I fore one hope that we do find a way around the pesky speed limit because if not it seems that it’s quite a bit of waste of space otherwise.

BreakfastB0b 5y ago

Tell me you didn’t read the article without telling me you didn’t read the article. The paper uses the Casimir effect to avoid the need for negative mass.