A causal loop is a paradox of time travel. It occurs when a future event is the cause of a past event, which in turn is the cause of the future event. Both events then exist in spacetime, but their origin cannot be known.
Not a paradox[change | change source]
Fermi's so-called paradox is not a paradox, just a question. It does not involve logic, just the practical (empirical) fact that stellar distances are so great, and our ability to collect data from other bodies is limited.
References[change | change source]
- Francisco Lobo (2003). "Time, closed timelike curves and causality". Nato Sci.ser.ii. 95: 289–296. arXiv:gr-qc/0206078. Bibcode:2003ntgp.conf..289L.
- Nicholas J.J. Smith (2013). "Time Travel". Stanford Encyclopedia of Philosophy. Retrieved November 2, 2015.
- Leora Morgenstern (2010), Foundations of a formal theory of time travel (PDF), p. 6, retrieved November 2, 2015
- Klosterman, Chuck (2009). Eating the Dinosaur (1st Scribner hardcover ed.). New York: Scribner. p. 60. ISBN 9781439168486. Retrieved 2 February 2013.
- Fermi paradox: not really a paradox, just a question: see link.
- Jan Faye (2015), "Backward causation", Stanford Encyclopedia of Philosophy, retrieved May 25, 2019