Just so. Hawking radiation isn't too important in astrophysical black holes because the actual space-time curvature (or tidal force) at the horizons is quite small. However, as we have seen, it becomes very important for small (microscopic) black holes, where the curvature and tidal forces at the horizons are strong. Similarly, with an Alcubierre drive, the curvature / tidal force near the edge of the warp bubble is extreme, and so too is the Hawking radiation. By "extreme" we're talking temperatures comparable to the Big Bang.
Source of the post
But assuming that we can get into the proper configuration, I was more thinking how to sustain the property which allows FTL, which requires constant change of the spacetime geometry. The deformation, as viewed from hyperspace, must move.
I'm not sure how to view from hyperspace, but we can just view relative to the surrounding (flat) space. The Alcubierre metric describes the location of a bubble which moves at arbitrary speed through the space, and the interior of which is close to flat, and allows a free-falling particle to move with it.
The FTL behavior of the bubble is thus built directly into the metric, and does not require that the geometry of the bubble itself change. We can consider an "eternal" warp drive -- one which always was and always will be moving at the same FTL speed, and this would be a constant geometry for the bubble. Changing the metric may allow the bubble to trace out any arbitrary path through the space, and this is what Alcubierre first worked out as a generalized warp bubble in his paper.I think what you're aiming toward though is that if the bubble is moving FTL, then how does the signal that causes those elements of space to change get there? There was an argument back in 1998 that the region in front of the bubble is not only space-like separated from the interior of the bubble (meaning signals from inside cannot possibly reach it, which I think is intuitive and means the ship cannot control the bubble after it is formed), but even more severely is also space-like separated from the whole surrounding space-time. In other words, to create an FTL warp bubble, one must first distribute the mass-energy at FTL speeds. This suggests that it is fundamentally impossible to make one. Or to turn it off again, as in your last question. This is one of the most common arguments for why the drive must be impossible, and it sounds reasonable.However, a more recent (2002) study found that this argument is actually wrong.
It is possible to build an Alcubierre space-time which is causally connected in the regions that are relevant to the motion of the ship, and thus the ship can
activate or deactivate the warp bubble from within. Basically this works because even though the leading horizon is causally separated, the rest of the volume of the bubble is not, and signals can be sent there to change the space-time and reduce the strength of the bubble. In other words you can't turn it off all at once, but you can do it in parts.I did also find a paper
which specifically investigates semiclassical corrections (adding in quantum mechanics) for a warp drive that is generated from an initially flat space-time (as opposed to the eternal warp drive). Again they find the Hawking radiation to be thoroughly lethal, but an even more severe problem is that the space-time itself becomes violently unstable, specifically around the horizon in front of the ship which acts like the horizon of a white hole.
In my view this is one of the more compelling reasons for thinking the drive is impossible. A lot of people approach it from simple arguments of relativity, but the reality seems to be more subtle than that, and is what makes investigation of the physics of warp drives interesting to me. I am quite sure the drive is
impossible, but research into their properties promotes deeper understanding of gravitation and quantum mechanics.
Wat, that sounds very "tachyonic"- where particles that move FTL will always move FTL and can never move slower than FTL- the speed of light is the lower boundary for them just like its the upper boundary for us. Adding more energy actually causes tachyonic particles to move slower, not faster. The speed of light then becomes an asymptote, not a limit (like absolute zero.) Same as with absolute zero, when you jump beyond the asymptote, you enter a "bizarro" reality where adding energy actually has the opposite effect of what it does in our universe. Using this model, which I did in some of my writings, actually necessitates the existence of a universe with a different arrow of time compared to ours. The arrow of time would still be forward relative to what's in that universe, but would be backwards compared to us (as ours would be backwards compared to theirs- thus we would both seem tachyonic to the other, with the speed of light being the boundary between both- a luxon wall.) One of the fascinating consequences of this behavior is that while our universe expands, theirs contracts (or appears to), and vice versa.
I actually wrote about this possibility five years before this paper came out.https://supermanbatmanalexthegreatest.s ... y.com/2631http://www.telegraph.co.uk/news/science ... wards.html
woah I am amazed at how much this matches what I had said….
The theoretical claims put forward in the Physical Review Lettersjournal could revolutionise the field of research into the origin and future of the universe.
In the paper titled ‘Identification of a Gravitational Arrow of Time’, an international team of world renowned scientists led by Oxfordshire-based Dr Julian Barbour challenge assumptions about the so called ‘arrow of time’.
The ‘arrow of time’ is the theory that time is symmetric and therefore time moves forward. They contend that there is no scientific reason that a mirror universe could not have been created where time moved in an distinct way from our own.
But in a quirk of science it is thought that if a parallel universe did exist where time moved backward, any sentient beings there would consider that time in our universe in fact moved backwardhttp://www.scientificamerican.com/artic ... ious-past/
Barbour and his colleagues argue that it is gravity, rather than thermodynamics, that draws the bowstring to let time’s arrow fly.
Looks like they also caught on to my idea that gravity and time are directly related since time is just as out of place with the other 3 dimensions as gravity is with the other 3 forces.
Alsohttp://www.dailymail.co.uk/sciencetech/ ... l#comments
What I said a few years ago:https://supermanbatmanalexthegreatest.s ... y.com/2633
note the date and the part about arrows of time flowing opposite relative to each other but forward relative to themselves
Proof of Concept Origin
January 5, 2013
Basically, in my book I conjecture on a new theory of everything; in my theory each dimension can be analoged to a primary color….. in our universe each spatial dimension would be equivalent to an additive primary color (RGB) with time as the background (Black) with a complementary spacetime which consisted of dimensions that analoged to the subtractive primary colors (CMY) with complementary time as the background (White) as one space expanded the other contracts and vice versa (because the arrow of time flows opposite to each other but forward within each), It’s been peer reviewed and it seems there’s some excitement over this as this would solve the dark matter / dark energy problem by unifying the strong nuclear force and gravity (the strong nuclear force is carried by gluons and color charge and analoging dimensions to primary colors is gravity’s version of color charge) so now we have a strong force-gravity unification and an electroweak unification and we just need to combine those dualities. There are four layers to the omniverse, with universes of different dimensions in each layer (the number of dimensions in each layer bear a pythagorean relationship to the other layers and each universe has a parent superverse from whose parent black hole it was created. If you loop through the entire hierarchy of universes you end up back where you started, so the omniverse is not only cyclical time, but also in space. I guess I’ll leave that for a sequel lol.
BTW if there are multiple timelines they would be created right after the big bang, by the force of inflation and be emergent diverging timelines along two dimensions of time (think cartesian coordinates) and if the cyclic model is correct and dark flow does reverse the expansion of space, the time lines would converge once again with a Big Bounce as the universe deflated (rinse and repeat.) The antiverse would have opposing cycles (because the arrow of time was opposite compared to ours) and if there was someway to construct some sort of device (a la star gate) to tap into the barrier which separates the two (consisting of light, which does not experience the passage of time) than both time and long distance space travel would become possible through the second temporal dimension (which keeps each timeline intact)…… according to Einstein the past, present and future all coexist and it is we who move through them, so theoretically this should be possible. He also stated that the universe (or omniverse on a larger scale) created us in order to understand itself better, forming the framework for a cosmic collective mind which encompasses not only humans, but animals, plants, alien life, even whole planets (Gaia Theory, which has been proven multiple times) and even stars and galaxies, the only difference is the density of the level of consciousness, although planets (for example) are much larger than any single life form, their density of consciousness is much less, with their “memories” (fossil record) spread out over a much larger area, so any one spot (on our scale) is seemingly lifeless. But it’s not. The planet consists of a complicated series of checks and balances and delicate interplay between different parts that can and should be considered alive.