Wormhole

History

The idea appeared almost immediately after the creation of general relativity: in 1916, Ludwig Flamm found something like a tunnel in Einstein's equations. Later, Einstein and Rosen described a 'bridge', and the name 'wormhole' was given by physicist John Wheeler in 1957.

How it works

Imagine a two-dimensional world as a sheet of paper. Curving it, you can punch a hole and connect two distant points with a short tube — that's how a wormhole creates a tunnel in spacetime. To prevent the tunnel walls from collapsing, exotic matter with negative pressure (pushing apart rather than attracting) is needed.

History

The idea appeared almost immediately after the creation of general relativity: in 1916, Ludwig Flamm found something like a tunnel in Einstein's equations. Later, Einstein and Rosen described a 'bridge', and the name 'wormhole' was given by physicist John Wheeler in 1957.

How it works

Imagine a two-dimensional world as a sheet of paper. Curving it, you can punch a hole and connect two distant points with a short tube — that's how a wormhole creates a tunnel in spacetime. To prevent the tunnel walls from collapsing, exotic matter with negative pressure (pushing apart rather than attracting) is needed.

History

In 1916, Ludwig Flamm, interpreting the Schwarzschild solution, proposed the idea of a 'wormhole'. Einstein and Rosen in 1935 described the bridge as a geometrized model of an elementary particle. The term 'wormhole' was introduced by John Archibald Wheeler in 1957 in the context of quantum foam. Modern interest revived after the paper by Morris and Thorne, which showed the possibility of travel provided exotic matter exists.

How it works

Einstein's equations link geometry (the Einstein tensor Gμν) to matter (the energy-momentum tensor Tμν). For a wormhole, the metric is given as ds² = -e^{2Φ(r)}c² dt² + dr²/(1 - b(r)/r) + r² dΩ². The absence of a horizon requires Φ(r) to be finite everywhere. Traversability imposes conditions on b(r) and Φ(r), and also requires violation of the null energy condition (negative energy). Quantum effects, such as the Casimir effect, provide such a possibility.

Open problems & fun facts

The possible form of exotic matter suitable for stabilizing the wormhole is unknown; Travel through the wormhole could lead to causality violation (a time machine); Quantum instability and Hawking radiation could destroy the wormhole

💡 A radio signal that passes through a wormhole would reach its destination faster than a signal sent through ordinary space. However, the speed of light is not locally exceeded: the path through the wormhole is simply shorter.