This week I had a look-see at the wonders that are ‘wormholes’, the handy-dandy space tunnels that let people and objects travel through space faster than the speed of light. Or so it seems.
Wormholes allow superluminal (faster-than-light) travel by making sure the speed of light is not exceeded locally. While travelling through a wormhole subluminal speeds are used, so if two points are connected by a wormhole the time taken to travel through it would be less than it would take a beam of light to make the journey if it took a path through the space outside the wormhole.
However, a beam of light traveling through a wormhole would always reach the destination before the traveler. As an analogy, if you ran around the base of mountain you would reach the other side after someone who walked through a tunnel that cut through the middle. But obviously if they ran through the tunnel while you walked, they would get to the other side first.
Wormholes are also known as ‘Einstein-Rosen Bridges’, here’s why:
- 1916 – Albert Einstein introduced his theory of General Relativity, which became the standard model for gravitation.
- 1936 – Einstein and long-time collaborator Nathan Rosen published a paper showing that a curved-space structure that can join two distant regions of space-time through a tunnel-like curved spatial shortcut is implicit in the general relativity formalism.
The purpose of the paper was not to promote superluminal or inter-universal travel, but to attempt to explain fundamental particles (such as electrons) as space-tunnels threaded by electrical lines of force.
- 1962 – John Wheeler discovered that the Einstein-Rosen bridge space-time structure was dynamically unstable in field-free space. If such a wormhole was to open, it would close up again before a single photon could be transmitted through it.
Wheeler’s research led to two classifications of wormholes: Lorentzian and Euclidean.
Lorentzian wormholes are shortcuts through space-time but close instantaneously unless held open by negative energy. Small amounts of negative energy can be produced in a lab using a principle known as the Casimir Effect, however it would not be sufficient to hold open a wormhole.
A by-product of Lorentzian wormholes is that objects passing through them would be moved temporally as well as spatially (assuming the existence of parallel universes).
There are two types of Lorentzian wormholes: Inter-universe (from one universe to another) and Intra-Universe (within the one universe).
Euclidean wormholes live in an ‘imaginary time’ and are intrinsically virtual quantum mechanical processes. Euclidean wormholes are part of quantum field theory.
The cool thing about the use of wormholes in sci-fi is that writers adopted the Einstein-Rosen theory to get around the constrictions inflicted by Einstein’s earlier theory of General Relativity. However, the Einstein-Rosen theory did not allow for the possibility of objects larger than electrons being able to pass through the tunnel.
In The Beginning
- 1865 – Charles Dodgson’s Alice in Wonderland, in which Alice chases the White Rabbit through a hole that could now be described as an Einstein-Rosen Bridge. However, as Dodgson would not have known what scientific devices would allow Alice to enter another universe, he essentially pre-empted the wormhole.
- 1895 – H.G.Wells’ The Time Machine, in which the Time Travellers uses what is essentially a chair with spinning parts and a lever to travel from 1900 to 802,701. The film adaptation is the only film to accurately describe time as the fourth dimension, although these days space and time are combined in to one metric called ‘spacetime’. It also follows the true physics of time travel by not allowing travel in to the past beyond the invention of the machine. This would not be possible because it is the device that creates the effect.
- 1968 – Planet of the Apes, in which astronaut Taylor goes to a future Earth that is ruled by apes. The film talks about real scientific theories, mainly Einstein’s special theory of Relativity. “…for a space traveler traveling close to the speed of light, that this effect will happen dramatically. A few years will pass for those on board, but when the rocket lands, decades will have passed on Earth,” explains Ron Mallett. Getting a ship close to the speed of light is the practical challenge in this case, but very plausible in theory.
- 1985 – Carl Sagan’s Contact (1997 movie of the same name), in which a crew make a trip to the centre of the Milky Way using a series of wormholes.
- Babylon 5 – ‘Jump points’ are artificial wormholes that serve as entrances and exits to hyperspace, allowing for faster-than-light travel. The series mainly uses Lorentzian wormholes, however the exit point is not defined at the time of entry. Ships can hide, and get lost, in hyperspace. An extra-universal wormhole also appears in a story called The Lost Tales: Thirdspace.
- Sliders – a method is found to create intra-universal Lorentzian wormholes. People or objects that travel through the wormhole start and end in the same location both geographically and chronologically. The seriers presumes that we exist as part of a multiverse. The same premise is used in the ST:OS episode The Alternative Factor (1967) and the ST:TNG episode Parallels.
- Star Wars – hyperspace travel featured in most Star Wars media is actually a trajectory calculated through wormholes.
- Star Trek – The space station Deep Space Nine is located near the Bajoran wormhole, which is unique because of its stability. It is established in ST: TNG that wormholes are generally unstable on one/both ends. The Bajoran wormhole is stable on both ends and opens consistantly, providing passage to the Gamma Quandrant.
- Stargate – The ring-shaped Stargates generate artificial wormholes that allow one-way matter transmission and two-way radio communication between gates when the correct spatial coordinates are ‘dialled’. The water-like event horizon breaks down matter, converts it to energy and restores it to its original state at the destination. When they need to return, the gates must be closed and reopened. The one-way nature of the device helps to defend the gate from unwanted incursions. The Stargates can only sustain wormholes for 38 minutes.
- Primeval – Professor Nick Cutter leads an investigation into the appearance of space-time continuum anomalies (called ‘earthquakes in time’). At first the anomalies lead the team to prehistoric times and allow animals from those times through to modern England. Later in the series anomalies appear that lead to the future and the team learn that they created their own past in a piece of Doctor Who-esque wibbly-wobbly-timey-whimey storytelling.
Sadly, Einstein-Rosen bridges are purely theoretical, and there’s not really any way to test their existence. And unfortunately, according to the true physics of time travel we can’t hope for time-travelers from the future to come back and share the secrets of artificial time travel devices. At least, not until we’ve figured out how to build one ourselves, and by that time we won’t need any help.
There is an interesting theory floating about that states that while wormholes allowing for travel forward in time could be possible, going backwards in time would so hazardous that nature wouldn’t allow it to happen.
What is you’re favourite use of wormholes in sci-fi?