The other end of the wormholewhat traversable wormholes need

Traversable wormholes are allowed by general relativity but need negative energy. The real physics behind the Cosmos Era ending “The other end of the wormhole”.

Traversable wormholes are solutions allowed by general relativity, but they need negative energy, and both mouths must first be moved into place at sublight speed. These two limits are the real basis of the game's ending “The other end of the wormhole”: faster-than-light travel is not allowed, so a wormhole mouth must first be towed slowly to a distant place before you can pass through.

This page first explains how to unlock the ending, then covers the real conditions for a wormhole and an interesting episode in the history of science between Carl Sagan and Kip Thorne. It ends with real research on spacetime and black holes and how each item relates to this ending.

How to unlock it

  • Hint: A wormhole can only connect to places you have been. So why does the sky at the other end look so familiar?
  • Condition: Unlock “Through the wormhole”, then witness the end of the universe.
  • Reward: One planet card in the album gets an extra "afterwards" story.

The ending belongs to the Spacetime category. The node “Through the wormhole” means the mouth has been towed to your farthest probe and the throat is about to open. Sagan wrote a similar scene in Contact, but a real wormhole can only connect to places your ship has been.

The real conditions

  • Allowed by general relativity: Traversable wormholes are solutions allowed by general relativity.
  • Needs negative energy: This kind of wormhole requires negative energy.
  • Mouths must be moved into place first: Both mouths must first be moved into place at sublight speed, so a wormhole will not take you instantly to somewhere you have never been.

The hint "a wormhole can only connect to places you have been" simply restates the third point above: because you moved the mouth there yourself, the other end can only be a place you have been. As for why the sky at the other end looks so familiar, the game gives no scientific explanation. That is fictional plot.

A paper born from a novel

Sagan's Contact (1985) tells of a radio astronomer who receives a string of prime-number signals from Vega that hides the blueprint of a machine, and the person who builds it is sent far away. The book has an unusual scientific background: Sagan consulted the physicist Thorne for it, which directly led to the 1988 paper on traversable wormholes.

Game lore, not real

A wormhole connecting to another universe is fiction. The game's “Through the wormhole” node says that the sky at the other end of the wormhole looks like somewhere you have seen before.

The studies below concern general relativity, spacetime and black holes. They are related real science, not evidence that wormholes exist.

  • Friedmann's universe: Friedmann derived from general relativity that the universe can expand or contract, seven years before observational evidence appeared (Friedmann, Zeitschrift für Physik, 1922).
  • Special relativity: Time and space are not absolute (Einstein, Annalen der Physik, 1905).
  • The warp drive: General relativity allows a "warp bubble" that compresses space ahead and stretches it behind, but it needs negative energy that may not exist in reality (Alcubierre, Classical and Quantum Gravity, 1994). The game's rule is that faster-than-light travel is not allowed. This item only shows that the "negative energy" condition keeps coming up in general relativity.
  • Black holes evaporate: Quantum effects make black holes radiate energy slowly, and black holes will eventually evaporate (Hawking, Nature, 1974).
  • The shadow of a black hole: Radio telescopes around the world formed an Earth-sized "virtual telescope" and imaged the shadow of the black hole at the center of galaxy M87 (Event Horizon Telescope Collaboration, The Astrophysical Journal Letters, 2019).
  • Gravitational waves: Two black holes merged 1.3 billion years ago, and humanity finally heard the ripples in spacetime (Abbott et al., LIGO and Virgo, Physical Review Letters, 2016).
  • The last chapter of the universe: The fate of the universe trillions of years from now and beyond: stars burn out, protons may decay, and black holes eventually evaporate (Adams and Laughlin, Reviews of Modern Physics, 1997).

Want to read the originals? Search these titles

  • Friedmann (1922): "Über die Krümmung des Raumes", roughly "On the curvature of space"
  • Einstein (1905): "Zur Elektrodynamik bewegter Körper", roughly "On the electrodynamics of moving bodies"
  • Alcubierre (1994): "The warp drive: hyper-fast travel within general relativity"
  • Hawking (1974): "Black hole explosions?"
  • Event Horizon Telescope (2019): "First M87 Event Horizon Telescope Results. I. The shadow of the supermassive black hole"
  • Abbott et al. (2016): "Observation of gravitational waves from a binary black hole merger"

Real basis

  • Traversable wormholes are solutions allowed by general relativity, but they need negative energy; both mouths must first be carried into place at sublight speed.

  • Through the wormhole: The wormhole mouth has been carried to the farthest probe, and the throat is about to open. Sagan wrote a similar scene in Contact, but a real wormhole can only connect to places your ship has been.

  • Contact (Carl Sagan, 1985), the science: Sagan consulted the physicist Thorne for this book, which directly led to the 1988 paper on traversable wormholes.

Related research

These studies relate to this topic but are not direct proof of this page.

  • Friedmann's universe: Friedmann derived from general relativity that the universe can expand or contract, seven years before the observational evidence.

    Source: Friedmann, Zeitschrift für Physik 1922, "Über die Krümmung des Raumes"

  • Shadow of a black hole: Radio telescopes around the world formed an Earth-sized “virtual telescope” and photographed the shadow of the black hole at the center of M87.

    Source: Event Horizon Telescope Collaboration, The Astrophysical Journal Letters 2019, "First M87 Event Horizon Telescope Results. I. The shadow of the supermassive black hole"

  • Gravitational waves: Two black holes merged 1.3 billion years ago, and ripples in spacetime were finally heard by humans, confirming Einstein's prediction from a century earlier.

    Source: Abbott et al. (LIGO & Virgo), Physical Review Letters 2016, "Observation of gravitational waves from a binary black hole merger"

  • Special relativity: Time and space are not absolute. A junior clerk at a patent office published four physics-changing papers in a single year.

    Source: Einstein, Annalen der Physik 1905, "Zur Elektrodynamik bewegter Körper"

  • Black holes evaporate: Quantum effects make black holes radiate energy slowly. Black holes are not eternal and will eventually evaporate.

    Source: Hawking, Nature 1974, "Black hole explosions?"

  • Warp drive: General relativity allows a “warp bubble” that compresses space ahead and stretches it behind, but it needs negative energy that may not exist in reality.

    Source: Alcubierre, Classical and Quantum Gravity 1994, "The warp drive: hyper-fast travel within general relativity"

  • The last chapter of the universe: Worked out the fate of the universe over trillions of years and beyond: stars go out, protons perhaps decay, and black holes finally evaporate.

    Source: Adams & Laughlin, Reviews of Modern Physics 1997, "A dying universe: the long-term fate and evolution of astrophysical objects"

Game lore (fictional)

  • A wormhole connecting to another universe is fiction.
  • Node “Through the wormhole”: The stars on the other side of the wormhole look like somewhere you’ve seen before.
  • Summary of the novel Contact: A radio astronomer receives a string of prime-number signals from Vega that hides the blueprint for a machine. The people who build it are sent far away.
See it in the game