Sorry in advance for my lack of physics knowledge, but I have a question as relates to the theory of Alcubierre drives and warp bubbles. If I understand this I might be able to "get it".

Let's assume you have a spaceship with an Alcubierre drive, and we're heading a trillion miles away, and we're going to get there in one hour. Our ship's initial speed in flat space is a safe 55 MPH.

Now let's say every mile in our path there is a coin like in Mario Brothers that you want to collect. The coins are lined up dead in the path for a trillion miles.

From what I understand, inside the bubble the ship traverses flat space according to its original speed of 55 MPH that it had before the warp bubble activated.

When we get to the end of the trillion miles, we should have collected a trillion coins. But if the space inside the bubble is only going by at 55 MPH, we'd only have 55 coins by then.

So how many coins does it collect, and if it's less than one trillion what happens to all the extra coins?

(If they just somehow materialize behind the ship, then assume instead that the ship is eating a piece of spaghetti like in Lady and the Tramp... did we consume a trillion or 55 miles of spaghetti?)

  • $\begingroup$ The coins will not just stand there when they interact with the bubble. McMonigal et al. consider what will happen to massive objects when they enter and exit it:"The increase in energy for massive and null particles is calculated in terms of v_s, the global ship velocity, and v_p, the initial velocity of the particle with respect to the rest frame of the origin/destination of the ship." $\endgroup$
    – Conifold
    Commented Aug 9, 2017 at 21:58

1 Answer 1


As I have been led to understand, your question touches upon one of the many points of contention regarding the Alcubierre bubble. Theoretically, assuming the presence of a locally-generated tachyonic field ahead of your vehicle, many believe the mass of your "coins" would accumulate along the event horizon of your bubble. This would not only increase your effective mass as a whole, but when you reach the endpoint of your travel would become a bit problematic.

Upon deceleration (i.e., de-energizing and collapsing the field) the problem of what to do with all the accrued mass rears its ugly head. Theoretically, you will have more or less "collected" your trillion coins only to vomit them ahead of you when you stop (at the same actual velocity as your bubble) essentially obliterating ANYTHING in a cone before your craft; you might get where you were going, but you'd create a catastrophic release of both mass and energy when you did. NOT a very tasty prospect.


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