# Question about an Alcubierre warp drive's negative energy requirement

1. Jun 11, 2014

### Algorithmic

I've been reading Dr. Harold G. White's work on recent developments in Warp Field Mechanics, and thought up the following question:
Could a proof of the Alcubierre warp drive concept be made by using a warp bubble energy differential whose flat-space energy density level was positively offset from zero? (Getting rid of the need for negative energy or exotic matter)

From my limited understanding, energy warps space-time with positive energies expanding space and negative energies contracting space to create this warped region. So in basic terms, I think my question can also be stated as: if you expand space on either side of a region, would the space of that middle unaltered region be "effectively" contracted? And if it would, then could you simply simulate the negative energy density required by the Alcubierre warp drive concept as a lack of energy rather than active negative energy? I've drawn a simple picture to illustrate this concept: http://i.imgur.com/angaoIy.png

From what I've read, by using a White-Juday Warp Field Interferometer setup, the presence of a warp in space-time can be detected by measuring a phase shift between split laser beams, and if my idea is correct, by raising the flat-space energy density of a field enclosing the entire interferometer the concept of warp bubbles could be proven.

If this could be accomplished, I've been trying to think of a practical use of this beyond that of a proof of warp bubble theory. And so I thought of a future of interplanetary travel where beam like corridors with high energy densities are transmitted between planets and a spaceship which traverses the beam lowers the energy density in its forward region through destructive wave interference, and raises the energy density in its rear using constructive wave interference. This would cause space-time to warp due to the energy differential created, and allow the ship to achieve faster than light travel within the energy beam. If the energy for this process is easily obtained then this technique could potentially allow for almost instantaneous travel between the planets and beyond, with the condition that the energy beam must travel at the speed of light which therefore limits the distance someone could practically travel if they had to wait for the beam to travel a very large distance before engaging their warp drive. A potential disadvantage of this, is that unlike the Alcubierre warp drive in the canonical form, which requires low energy levels, in part due to the overall energy symmetry, this new technique would need a very high net positive energy expenditure no longer localized to the region of the ship but instead the entire path of travel.

What do you think?

2. Jun 11, 2014

### Staff: Mentor

No. Any kind of "warp drive" requires negative energy/exotic matter.

It's not that simple. First of all, energy affects spacetime, not just space; you have to include the time dimension or you'll get things wrong. Second, the effects aren't as simple as just "expanding" or "contracting" spacetime; there are different effects in different directions. Finally, to the extent that the effects can be thought of as "expanding" or "contracting", you have them backwards: positive energy (i.e., ordinary matter) "contracts" spacetime (it makes freely falling paths converge towards the center of mass of the matter) and negative energy "expands" spacetime (it makes freely falling paths *diverge*).

No.