The UniverseAnswer
Can a Planet Orbit Two Stars?
Two stars can circle each other while a planet travels around them both. Astronomers confirmed it by watching the moving stars dim.
THE QUESTION LIBRARY THE UNIVERSE
What would happen if you could send a message faster than light?
Light cones distinguish ordinary causal connections from spacelike-separated events.
THE SHORT ANSWER
Hypothetical controllable faster-than-light replies in moving senders’ own frames could precede the original send. No device is demonstrated. A quickly moving pattern alone is not such a message.
- Observers in relative motion can disagree about distant simultaneity.
- Both signal legs must be permitted.
- Even a tiny speed excess allows a loop with sufficient relative motion in this setup.
- Fast-moving patterns need not carry chosen information.
WHERE THE EVIDENCE STANDS
How sure are we?
- One reversed distant event order proves a messaging loop.The antitelephone also needs an available, controllable return leg.
- A tiny speed excess avoids the puzzle.Under the reciprocal setup, sufficient relative motion can still yield a loop.
- A sweeping light spot transmits messages between successive positions.A moving illumination pattern need not carry chosen information along its apparent path.
WHAT WE DON’T KNOW YET
Whether these reciprocal signaling permissions are physically available remains open.
WHAT WOULD CHANGE THIS ANSWER
A claimed communication channel needs evidence that chosen information is transmitted, not merely a fast-moving pattern.
Einstein’s special relativity relates the clock coordinates of observers moving relative to one another. Distant events can have different time orderings; this is about synchronized clocks, not delayed images. Could a reply return before transmission?
Here message means information a sender can choose. A rapidly sweeping light spot or shadow does not pass information between its successive positions, as Gibbs’s FAQ explains. Apparent speed is not enough.
THE LONG ANSWER
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Keep asking
Why is the speed of light the universe's speed limit?
Because space and time obey rules that give every local observer the same speed for light in a vacuum: exactly 299,792,458 meters per second.
New here?
God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Words worth knowing (4)
- Antitelephone
- A hypothetical two-signal exchange returning information before the first transmission.
- Inertial frame
- Coordinates for an observer moving without acceleration.
- Light cone
- The boundary between ordinary light-accessible futures or pasts and spacelike-separated events.
- Controllable message
- Information whose content a sender can choose, rather than a moving pattern alone.
Sources & further reading
(4) · Checked Oct 2, 2026
- Relativity (Kinematics), Chapter 11 ↗David Morin (2007 draft)Lorentz clock transformations; conditional worked exchange derived from them.
- Faster-than-c signals, special relativity, and causality ↗Stefano Liberati, Sebastiano Sonego and Matt Visser (2002)Reciprocal loop permissions and restricted signaling.
- Spacetime ↗Einstein Online, Max Planck Institute for Gravitational Physics (undated)Light cones and coordinate relations, distinct from a returned reply.
- Is Faster-Than-Light Travel or Communication Possible? ↗Philip Gibbs (1997–1998); UC Riverside hostingSelected message-versus-pattern definitions only.
See a mistake? Report a problem. Corrections are made openly.
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