Traversable Wormhole Exotic Matter Calculator

Overview

This calculator implements a highly idealised, educational model of a traversable Morris–Thorne wormhole. It estimates the amount of exotic matter (negative energy) required to hold the wormhole throat open, together with an effective negative mass and an approximate traversal time.

The model is not a design tool for real wormholes. It is a way to explore how exotic energy requirements might scale with the size of the throat in standard general relativity, using a simple, static spacetime geometry.

Morris–Thorne wormhole in simple terms

In general relativity, the geometry of spacetime is described by a metric. For a simple, static, spherically symmetric wormhole, Morris and Thorne wrote the spacetime line element in the form:

ds² = -c² dt² + 
       \frac{dr²}{1 - b(r)/r} +
       r² (d\theta² + \sin^2\theta\, d\phi²)

Here:

• c is the speed of light,
• t is time,
• r, \theta, \phi are spherical coordinates,
• b(r) is the shape function that controls the geometry of the wormhole throat.

The throat is located at a radius r = r0 where b(r0) = r0. A common simple choice for the shape function is:

b(r) = \frac{r_0^2}{r}

This geometry flares out smoothly to nearly flat space on both sides of the throat.

Energy conditions and exotic matter

In general relativity, the stress–energy tensor T\mu\nu describes how matter and energy curve spacetime. Ordinary matter normally satisfies the null energy condition (NEC), which in compact notation requires:

T\mu\nu k\mu k\nu \ge 0

for any null (lightlike) vector k\mu. Traversable wormhole throats, however, require the NEC to be violated. In other words, there must be regions where the effective energy density is negative as measured by some observers. This kind of matter is referred to as exotic matter.

Quantum field theory does allow negative energy densities in restricted situations (for example, in the Casimir effect between conducting plates), but maintaining large, macroscopic amounts of negative energy over extended regions is far beyond anything currently known to be physically achievable.

Energy density and total exotic energy

For the simple choice of shape function above, and assuming a static configuration, the energy density \rho(r) in the wormhole throat region can be written (in units where we keep c and G explicit) as:

\rho(r) = - \frac{r_0^2}{8 \pi G r^4}

This is negative for all r near the throat, showing explicitly that exotic matter is required.

An approximate total exotic energy can be obtained by integrating this energy density over the throat volume, from the throat radius r_0 to r_0 + L, where L is a characteristic throat length. A simple approximation for the total negative energy E is:

E \approx - \frac{c^4 r_0^6}{G} \left(1 - \frac{r_0}{r_0 + L}\right).

This expression is not exact, but it captures the main scaling behaviour: larger throats and longer wormhole segments require vastly more negative energy.

MathML representation

The same approximate energy relation can be expressed in MathML as:

(Here r is to be understood as the throat radius r0 in the context of this calculator.)

From energy to effective negative mass

Once the total exotic energy E has been estimated, it is natural to define an effective negative mass by dividing by c^2:

M = \frac{E}{c^2}.

Because E is negative, this effective mass M is also negative. In this simplified context it is a bookkeeping device: it tells you how much energy, expressed in mass units, would have to be negative to support the wormhole geometry. It does not imply that conventional negative-mass particles exist.

Traversal time through the throat

Given a throat length L and a traversal speed v (taken here as a fraction of the speed of light, v = \beta c with 0 \le \beta \le 1), a simple estimate for the proper traversal time is:

t \approx \frac{L}{v} = \frac{L}{\beta c}.

For the modest distances and velocities you are likely to explore with this tool, relativistic time dilation between different observers is a second-order effect, so this Newtonian-looking estimate is usually adequate as an order-of-magnitude guide.

How this calculator uses your inputs

The calculator takes three main inputs and uses them in the following way:

• Throat radius (meters): this is the radius r0 of the wormhole throat. Larger values increase the cross-sectional area of the throat and make the wormhole more spacious for a hypothetical traveler. In the model, increasing the throat radius dramatically increases the required exotic energy.
• Throat length (meters): this is an approximate geometric length L of the wormhole’s interior region. Longer throats mean that negative energy must be sustained over a greater distance, which also increases the total exotic energy requirement.
• Traversal speed (fraction of c): this is the dimensionless parameter \beta = v/c. The calculator mainly uses this to estimate the traversal time t = L/(\beta c). In this simple toy model, changing the traversal speed does not change the exotic energy requirement, which is determined entirely by the static spacetime geometry.

Internally, the tool:

1. Interprets your throat radius and length as r0 and L in the approximate Morris–Thorne energy formula.
2. Computes the total negative exotic energy E in joules.
3. Converts this energy to an effective negative mass M = E/c^2, typically reported in kilograms.
4. Uses the traversal speed to estimate the one-way crossing time of the throat.

Interpreting the results

The outputs you see are order-of-magnitude estimates. For many realistic-seeming throat radii and lengths (for example, metres to kilometres), the required exotic energy and effective negative mass will be extraordinarily large in human terms, often far beyond the total energy content of planets or stars.

When interpreting the numbers, keep the following points in mind:

• Sign: energies and masses will be reported as negative values. This reflects the requirement of negative energy density to keep the wormhole throat open.
• Magnitude: a value such as -1030 joules should be read as “ten to the thirty joules of negative energy”. Compare this with familiar energy scales (for example, the yearly energy consumption of human civilization is of order 1020 joules).
• Traversal time: the time is essentially L / v. For short throats and relativistic speeds, the crossing can be very quick; for very long throats and modest speeds, it can be substantial.
• Physical plausibility: the calculator does not tell you whether such a wormhole could actually be constructed. It simply extends the classical equations to a hypothetical regime where sufficient exotic matter is available.

Worked example

Suppose you enter the following values:

• Throat radius: 100 metres
• Throat length: 1000 metres
• Traversal speed: 0.5 (half the speed of light)

In the simplified model:

1. Set r0 = 100 m and L = 1000 m in the approximate energy expression. The calculator evaluates the numerical factors involving c and G and the geometric term 1 - r0 / (r0 + L).
2. The result for E will be a large negative number in joules, scaling roughly as r06. Doubling the throat radius would increase the exotic energy requirement by a factor of about 64 in this toy model.
3. The effective negative mass M will be E / c^2, which will also be a large negative number in kilograms.
4. The traversal time is t = L / (\beta c) = 1000 / (0.5 c) \approx 6.7 \times 10-6 seconds, or a few microseconds, because you are effectively covering one kilometre at half the speed of light.

Even with fairly modest geometric dimensions by astronomical standards, the exotic energy requirement is enormous. This illustrates how demanding traversable wormholes are within classical general relativity.

Comparison of parameter choices

The table below summarises qualitatively how changing each input affects the outputs in this approximate model.

Assumptions and limitations

This calculator is based on a collection of strong simplifying assumptions. They are important for interpreting the results correctly:

• Static, spherically symmetric model: the wormhole is assumed to be unchanging in time and perfectly symmetric. Realistic astrophysical environments would introduce rotation, external fields, and time dependence that are ignored here.
• Specific shape function: choosing b(r) = r_0^2 / r is mathematically convenient but not unique. Different choices lead to different energy profiles and total exotic energy requirements.
• Approximate energy integral: the formula used for the total exotic energy is an approximation intended to capture scaling behaviour, not an exact solution tailored to engineering constraints.
• Classical general relativity: the underlying description treats gravity classically and adds quantum effects only in a very hand-waving way (by allowing negative energy densities). A full quantum gravity treatment might change the picture substantially.
• No stability analysis: the calculator does not check whether the wormhole would be dynamically stable, how it would respond to perturbations, or how long it could remain open.
• No engineering feasibility: there is no known mechanism to produce or confine the amounts of exotic matter indicated here. The results are not engineering specifications and should not be interpreted as such.
• Educational use only: the primary purpose is to help students and enthusiasts visualise how exotic energy requirements scale with wormhole size within a simple theoretical framework.

FAQ

Is exotic matter real?

Quantum field theory predicts that negative energy densities can occur in specific, tightly constrained situations, such as the Casimir effect. However, there is currently no experimental evidence for bulk exotic matter that could be engineered to hold open a traversable wormhole. In that sense, exotic matter as used in wormhole models is a theoretical extrapolation.

Does this calculator show something physically achievable?

No. The calculator explores what classical general relativity says under very optimistic assumptions about the availability of negative energy. It does not claim that such wormholes can actually exist or be constructed with any known or foreseeable technology.

Why are the energy numbers so huge?

Holding open a macroscopic wormhole requires spacetime curvature effects comparable to those near very compact astrophysical objects, but with the sign of the energy reversed. This naturally leads to energy scales that are enormous compared with everyday technologies, even for relatively small throat sizes.

Does changing traversal speed change the exotic matter requirement?

In this simple, static model, the exotic matter requirement depends only on the wormhole geometry, parameterised by the throat radius and length. Traversal speed affects only the travel time estimate, not the total negative energy or effective mass.

Using this tool responsibly

The idea of traversable wormholes is fascinating and inspiring for science fiction and theoretical physics alike. This calculator is designed to make some of the underlying equations more tangible, while clearly signalling that it is a toy model built on speculative assumptions. Use it as a learning aid and a way to build physical intuition about how extreme spacetime geometries behave, rather than as a blueprint for real-world construction.