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 is string theory, and why hasn’t it been tested yet?
A theory needs valid calculations, agreement with measured physics, and a prediction that distinguishes it from alternatives.
THE SHORT ANSWER
String theory describes quantum excitations of one-dimensional strings as particles. Consistency checks decide whether calculations are physically admissible; they do not establish truth. A chosen setup must recover tested physics and predict something distinguishable. The question is too broad: particular consequences can face tests without validating every string construction.
- Consistency is a prerequisite, not an observation.
- A low-energy description must match specified observables and accuracy.
- A framework needs additional choices before giving a particular prediction.
- Some string-inspired scenarios face tests; a result does not settle them all.
WHERE THE EVIDENCE STANDS
How sure are we?
- Beautiful mathematics establishes that a theory describes nature.Elegance can motivate an idea; experiment checks it.
- Any negative quantity in a calculation makes a theory inconsistent.Unphysical intermediate states can occur. They must be excluded from physical processes, rather than mistaken for physical outcomes.
- Every quantum anomaly makes a theory impossible.An anomaly is a quantum failure of a symmetry. Failure of a required descriptive redundancy can be fatal; other physical symmetries can fail consistently.
- The first Advanced LIGO run confirmed cosmic strings.The 2015–2016 search found no burst evidence and constrained specified network models; it did not decide every string construction.
WHAT WE DON’T KNOW YET
Which physical setup, if any, describes nature remains open. Different solutions can give different low-energy physics; mathematical success alone does not select our world.
WHAT WOULD CHANGE THIS ANSWER
A specified model gaining support from a discriminating measurement would strengthen its case. A repeatable mismatch would count against that model under its assumptions.
Can a theory be beautiful and still be wrong? Yes: as a methodological conclusion from Feynman’s account of testing laws, imagination proposes them and experiments check them. Elegant mathematics can guide a search without deciding what nature does.
Three questions need separate answers: are the calculations consistent, do they recover measured physics, and what new observation distinguishes the proposal? The broader unification answer introduces the candidates. Here the focus is what a particular model must do before its success would be evidence.
THE LONG ANSWER
THE LONG ANSWER · ABOUT 3 MINUTES
You’ve read your 3 free long answers this month.
The short answer, how sure we are, what we don’t know, what would change our mind and every source stay free on every page, for everyone.
All Access members read the long answer: the evidence piece by piece, the strongest objections, and how to check it yourself.
Join All Access · $1 a week Or $6 a month
Billed $52 once a year. Cancel anytime in your account.
Until December 4, 11:59 pm Pacific: the Founding rate is $39 a year, and it stays $39 while you stay a member.
Create a free account: 6 long answers a month, email only.
Paying never buys a different answer. Our Paywall Promise
Keep asking
What is a theory of everything, and will we ever have one?
Nobody knows yet.
New here?
God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Words worth knowing (5)
- Physical state
- A state permitted to represent a physical outcome, rather than an unphysical intermediate part of a calculation.
- Gauge anomaly
- A quantum failure of a symmetry needed to keep different descriptions of the same physics equivalent.
- Matching
- Fixing an effective description to reproduce a fuller theory’s low-energy observables at specified accuracy.
- Model versus framework
- A model selects physical choices needed for predictions within broader construction rules.
- Cosmic string
- Hypothetical macroscopic string-like objects: field-theory line defects and cosmic superstrings can have different origins.
Sources & further reading
(6) · Checked Oct 2, 2026
- Lectures on String Theory ↗David Tong (2009 lectures; v3 2012)Excitations and physical-state constraints; not observation of strings.
- Introduction to Superstring Theory ↗John H. Schwarz (2000)Required gauge-symmetry consistency; global anomalies differ.
- Introduction to Effective Field Theory ↗C. P. Burgess (2007)Low-energy matching within specified approximation, not confirmation.
- String theory to the rescue ↗Joseph Polchinski (2015)Historical advocacy and solution dependence, not empirical proof.
- The Feynman Lectures on Physics, Volume I, Chapter 1: Atoms in Motion ↗Richard P. Feynman; Caltech online edition (undated page)Experimental testing and useful approximations.
- Constraints on cosmic strings using data from the first Advanced LIGO observing run ↗LIGO Scientific Collaboration and Virgo Collaboration (2018; O1 2015–2016)Dated O1 search; model assumptions and origin distinctions retained.
See a mistake? Report a problem. Corrections are made openly.
CONTINUE THE THREAD
Where this question leads.
The UniverseAnswer
What Is the Higgs Field, and Why Call Its Particle the “God Particle”?
An everywhere-present field, a fleeting particle and a famous nickname. What did CERN’s experiments actually measure?
The UniverseAnswer
Why do physicists still call the matter-antimatter imbalance unsolved?
Why the matter surplus remains unexplained, what Sakharov's conditions require, and how sphalerons and proposed neutrino mechanisms might connect.