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open_problems [2018/04/08 17:22]
georgefarr
open_problems [2019/02/08 09:24] (current)
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 Our present understanding of nature is far from complete. Our present understanding of nature is far from complete.
  
-In addition ​to **unexplained observed phenomena**,​ like dark matter or dark energy, there are also many **technical problems** in our existing [[theories|theories]]. An example for such a technical problem is the [[open_problems:​hierarchy_problem|hierarchy problem]]+Real problems are things related ​to **unexplained observed phenomena**,​ like dark matter or dark energy.
  
-Moreover, there are things that we can describe but do not understand. These are not really problems but rather **puzzles**. Examples are the still not understood masses and mixing angles of the elementary particles. ​+In addition, there are things that we can describe but do not understand. These are not really problems but rather **[[http://​jakobschwichtenberg.com/​problems-vs-puzzles/​|puzzles]]**. Examples are the [[open_problems:​flavour_puzzle|still not understood masses and mixing angles]] of the elementary particles ​or also the [[open_problems:​hierarchy_puzzle|hierarchy puzzle]] and the question why strong interactions [[open_problems:​strong_cp_puzzle|do not violate]] [[advanced_notions:​cp_symmetry|CP symmetry]]
  
  
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 +**The 5 Great Problems**
 +
 +  - __The problem of quantum gravity.__ This is the problem of combining general relativity and quantum theory into one theory. Such a theory would be able to describe all known interactions of nature. ​
 +  - __The problem of quantum theories.__ This is the problem of understanding quantum such that it makes sense and solve its fundamental problems. ​
 +  -  __The unification of the particles and forces.__ Still no theory exists that unifies all known particles and interactions into a single fundamental entity. ​
 +  -  __Explain the constants of nature.__ The standard model of particle physics has 20+ free parameters that need to be inferred from experiments. It is an open problem to understand how these values are "​chosen"​ by nature.
 +  - __Explain dark matter and dark energy.__ If they really exists, as suggested by experiments,​ we need to understand what they consists of. In addition, the constants of the standard model of cosmology need the be explained.  ​
 +
 +For more information,​ see the chapter "The Five Great Problems in Theoretical Physics"​ in the book "Time Reborn"​ by Lee Smolin.
  
 ===== Lists of Open Problems ===== ===== Lists of Open Problems =====
  
  
 +  * [[https://​arxiv.org/​abs/​1804.08730|Life,​ the universe, and everything - 42 fundamental questions]] by Roland E. Allen, Suzy Lidström
   * http://​math.ucr.edu/​home/​baez/​physics/​General/​open_questions.html   * http://​math.ucr.edu/​home/​baez/​physics/​General/​open_questions.html
   * https://​en.wikipedia.org/​wiki/​List_of_unsolved_problems_in_physics   * https://​en.wikipedia.org/​wiki/​List_of_unsolved_problems_in_physics
open_problems.1523200952.txt.gz · Last modified: 2018/04/08 15:22 (external edit)