# Alcubierre Drive and interacting with matter

What would happen when there is the warping of space occupied by matter? For example, if there is a ship propelled by the Alcubierre Drive, what would happen if it collided with something with mass? And how (if it does) would that differ from normal physics?

Baryonic matter by necessity occupies spacetime, but since the theoretical Alcubierre drive warps spacetime, there wouldn't actually be any travel through it and no additional interaction with baryonic matter would occur due to it. Miguel Alcubierre's proposal for warp drive does call for exotic matter to create a distortion in spacetime, when perceived as Euclidean space, but it's often misunderstood as faster-than-light (FTL) travel. Theoretical Alcubierre drive does not violate general relativity, but achieves perceived FTL via local expansion and contraction of spacetime, behind and in front of the spacecraft, respectively.

If we simplify it with an analogy, if we'd have to fold a sheet of paper to demonstrate theoretical travel through a wormhole, Alcubierre drive would analogously create a local ripple (pardon my choice of words, some call it a bubble) in this sheet of paper, our 2-dimensional representation of spacetime. This could look something like this:

Two-dimensional visualization of the Alcubierre drive, showing the opposing regions of expanding and contracting spacetime
that displace the central region (Source: Wikipedia on Alcubierre drive)

This 2-dimensional representation of spacetime shows that it would exclude interaction with any baryonic matter between outside and inside of the ripple while such drive would be able to warp spacetime around it, but at the same time does not prohibit normal interaction with matter inside it. This means that, unless you've created a ripple large enough to include in it an object already on collision course with your spaceship before you turned your Alcubierre drive on, or turned your drive off at an inconvenient place, you wouldn't have to fear collision. Well, that's to my understanding at least, it's not an easy idea to wrap one's head around.