Ellis-Uara wormhole

From BHH Wiki
Jump to: navigation, search

Ellis-Uara wormholes were large, fixed portals in interstellar space that facilitated faster-than-light travel between star systems. They were discovered in 400 AHE by an Evonian scientist, Inioluae Ridztire Uara. The number of Ellis-Uara wormholes was (at least relatively) fixed; it was ambiguous whether Uara had discovered a pre-existing network of wormholes that no-one knew how to expand, or found a way to create them that was not repeated for safety or technical reasons, though the former was often implied. The name "Ellis-Uara wormholes" referred to the in-universe scientist Uara and to the real-world scientific concept of the Ellis wormhole, a traversable wormhole with no gravitational field.

The discovery of Ellis-Uara wormholes was an important point on the timeline and the last fixed date before the ambiguity associated with the BHH dating problem. Ellis-Uara wormholes cut the time taken to travel between adjacent star systems from years to hours or days, allowing for the emergence of an "astropolitical system".

Physics[edit | edit source]

The Ellis wormhole exists as a solution of the Einstein field equations, specifically the vacuum field equations, discovered by H. G. Ellis in 1969. The Einstein field equations explain how spacetime acts as a field for gravity by connecting the maths for the 'curvature of spacetime' (i.e. how much it has been bent by mass at a given point) with the maths for energy, momentum and stress, the values used in the Newtonian equations for classical gravity. Think of them as the tool to translate between Einstein's theory of spacetime and 'normal' physics about gravity.

The vacuum field equations are a special set of equations within the Einstein field equations where a value called the 'energy–momentum tensor' is set to zero. The energy–momentum tensor describes the amount of stress and momentum associated with a piece of a matter at a given moment—it is what causes spacetime to be curved. Therefore, it is the source of gravity. When the energy–momentum tensor is zero, spacetime is not curved, so there is no gravitational force.

The Ellis wormhole is a type of wormhole that exists as a solution of the vacuum field equations. The wormhole metric has the proper-time form (give the maths symbols a few seconds to load—they'll get there):

<math>

c^2 d\tau^2 = c^2 dt^2 - d\sigma^2 \, ,

</math>

where

<math>

\begin{align} d\sigma^2 &= d\rho^2 + r^2(\rho) \, d\Omega^2 \\

         &= d\rho^2 + \left(\rho^2 + n^2\right) \, d\Omega^2 \\                                 
         &= d\rho^2 + \left(\rho^2 + n^2\right) \, \left[d\vartheta^2 + (\sin \vartheta)^2 \, d\varphi^2\right] \;\;

\end{align}

</math>

and <math>n</math> is the parameter from Ellis' solution for a normal wormhole that survives after the parameter <math>m</math>—equivalent to the whole energy–momentum tensor thingy from above—is set to 0 to stop the ether flow and thereby eliminate gravity.

Negative mass[edit | edit source]

Ellis himself said that an Ellis wormhole could exist naturally in the universe without the need for "exotic" matter (matter that is not consistent with the currently-understood laws of physics and is therefore not currently believed to exist). At no point in BHH was exotic matter ever mentioned, aside from the unrelated magically charged material. However, the physicists M. S. Morris and K. S. Thorne argue that an Ellis wormhole could only work with negative matter. Though the maths are beyond me (and Ellis found the maths unpersuasive), the logic is intuitively simple: in order to "counteract" gravity, which is "triggered" by positive matter, you would need "negative matter" to "balance it out".

Some physicists have claimed that the Casimir effect—from quantum theory rather than Einstein's work—might count as "negative mass." The Casimir effect entails two metal plates very slightly repelling each other if they are placed very close to one another in a vacuum. The scientists who link this to negative mass refer to the vacuum between the plates as a region of "negative pressure density", i.e. implying that the gap between them is what pushes them out because the gap has something like negative mass. Unfortunately, this is just headline-grabbing nonsense and not really relevant to making Ellis-Uara wormholes work with Morris and Thorne's objections.

See also[edit | edit source]