# kb

id: list-of-unsolved-problems-in-biology-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology-1.md
category: reference
title: List of unsolved problems in biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology
date_saved: 2026-05-05T08:28:05.105952+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-biology-20260505-0
summary:
Biological homochirality. What is the origin of homochirality in living organisms? In biological organisms, amino acids appear almost exclusively in the left-handed form and sugars in the right-handed form. Homochirality is an obvious characteristic of life on Earth, yet extraterrestrial samples contain largely racemic compounds. It is not known whether homochirality existed before life, whether the building blocks of life must have this particular chirality, or whether life must be homochiral at all. What do all the unknown proteins do? Two decades since the first eukaryotes were sequenced, the "biological role" of around 20% of proteins are still unknown. Many of these proteins are conserved across most eukaryotic species and some are conserved in bacteria, indicating a role fundamental for life. Determinants of cell size. How do cells determine what size to grow to before dividing? Golgi apparatus. In cell theory, what is the exact transport mechanism by which proteins travel through the Golgi apparatus? Mechanism of action of drugs. The mechanisms of action of many drugs including lithium, thalidomide, and ketamine are not completely understood. Protein folding. What is the folding code? What is the folding mechanism? Can the native structure of a protein be predicted from its amino


id: list-of-unsolved-problems-in-biology-20260505-2
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology-2.md
category: reference
title: List of unsolved problems in biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology
date_saved: 2026-05-05T08:28:05.105952+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-biology-20260505-0
summary:
== Human biology == Handedness: It is unclear how handedness develops, what purpose it serves, why right-handedness is far more common, and why left-handedness exists. Laughter: While it is generally accepted that laughing evolved as a form of social communication, the exact neurobiological process that leads humans to laugh is not well understood. Yawning: It is yet to be established what the biological or social purpose of yawning is. Heritable components of homosexuality: How to reconcile evolution with the heritable components of human homosexuality? Homosexuality is prevalent across human societies, past and present. These facts constitute an evolutionary puzzle. Decline in average human body temperature since the 19th century: Medical data suggests that the average body temperature has declined 0.6 °C since the 19th century. The cause is unclear although it has been suggested that it has some relation with reduced inflammation from reduced exposure to microorganisms. Why are there blood types? It is unclear what the origin and purpose of having blood types is. It is thought that O blood may be an adaptation to malaria and that different blood types respond to different diseases but this hypothesis has yet to be proven. Why did these antigens develop in


id: list-of-unsolved-problems-in-biology-20260505-3
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology-3.md
category: reference
title: List of unsolved problems in biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_biology
date_saved: 2026-05-05T08:28:05.105952+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-biology-20260505-0
summary:
Paradox of the plankton. The high diversity of phytoplankton seems to violate the competitive exclusion principle. Ediacaran biota. How should Ediacaran biota be classified? Even what kingdom they belong to is unclear. Why were they so decisively displaced by Cambrian biota? Cambrian explosion. What is the cause of the apparent rapid diversification of multicellular animal life around the beginning of the Cambrian, resulting in the emergence of almost all modern animal phyla? Darwin's abominable mystery of botany/plants. What is the exact evolutionary history of flowers and what is the cause of the apparently sudden appearance of nearly modern flowers in the fossil record? Adult form of Facetotecta. The adult form of this animal has never been encountered in the water, and it remains a mystery what it grows into. Origin of snakes. Did snakes evolve from burrowing lizards or aquatic lizards? There is evidence for both hypotheses. Origin of turtles. Did turtles evolve from anapsids or diapsids? There is evidence for both hypotheses. Paleodictyon: What is the origin of this trace fossil and its modern counterparts? Despite many theories proposed, no evidence has been found to confirm any of them. Francevillian biota: were they early multicellular organisms? Snowball Earth: what


id: list-of-unsolved-problems-in-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry-0.md
category: reference
title: List of unsolved problems in chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry
date_saved: 2026-05-05T08:28:06.291916+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-chemistry-20260505-0
summary:
This is a list of unsolved problems in chemistry. Problems in chemistry are considered unsolved when an expert in the field considers it unsolved or when several experts in the field disagree about a solution to a problem. == Physical chemistry problems == Can the transition temperature of high-temperature superconductors be brought up to room temperature? How do the spin–orbit coupling, other relativistic corrections, and inter-electron effects modify the chemistry of the trans-actinides? Is it possible to create a practically useful lithium–air battery? == Organic chemistry problems == What is the origin of homochirality in biomolecules? Why are accelerated kinetics observed for some organic reactions at the water-organic interface? Do replacement reactions of aryl diazonium salts (dediazotizations) predominantly undergo SN1 or a radical mechanism? Can an electrochemical cell reliably perform organic redox reactions? Which "classic organic chemistry" reactions admit chiral catalysts? Is it possible to construct a quaternary carbon atom with arbitrary (distinguishable) substituents and stereochemistry? Can artificial enzymes replace the need for protecting groups when modifying sensitive compounds? == Inorganic chemistry problems == Are there any molecules that certainly contain a phi bond? Is there a less labor- or energy-intensive technique for titanium refinement than the Kroll process? Does


id: list-of-unsolved-problems-in-computer-science-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_computer_science-0.md
category: reference
title: List of unsolved problems in computer science
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_computer_science
date_saved: 2026-05-05T08:28:07.458238+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-computer-science-20260505-0
summary:
This article is a list of notable unsolved problems in computer science. A problem in computer science is considered unsolved when no solution is known or when experts in the field disagree about proposed solutions. == Computational complexity == P versus NP problem – The P vs NP problem is a major unsolved question in computer science that asks whether every problem whose solution can be quickly verified by a computer (NP) can also be quickly solved by a computer (P). This question has profound implications for fields such as cryptography, algorithm design, and computational theory. What is the relationship between BQP and NP? NC = P problem NP = co-NP problem P = BPP problem P = PSPACE problem L = NL problem PH = PSPACE problem L = P problem L = RL problem Unique games conjecture Is the exponential time hypothesis true? Is the strong exponential time hypothesis (SETH) true? Do one-way functions exist? Is public-key cryptography possible? Log-rank conjecture Hartmanis–Stearns conjecture == Polynomial versus nondeterministic-polynomial time for specific algorithmic problems == Can integer factorization be done in polynomial time on a classical (non-quantum) computer? Can the discrete logarithm be computed in polynomial time on a classical


id: list-of-unsolved-problems-in-economics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_economics-0.md
category: reference
title: List of unsolved problems in economics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_economics
date_saved: 2026-05-05T08:28:08.644071+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-economics-20260505-0
summary:
This is a list of some of the major unsolved problems, puzzles, or questions in economics. Some of these are theoretical in origin and some of them concern the inability of orthodox economic theory to explain an empirical observation. == Capital theory == Cambridge capital controversy: The Cambridge capital controversy is a dispute in economics that started in the 1950s. The debate concerned the nature and role of capital goods and a critique of the neoclassical vision of aggregate production and distribution. The question of whether the natural growth rate is exogenous, or endogenous to demand (and whether it is input growth that causes output growth, or vice versa), lies at the heart of the debate. The resolution of the debate has not been agreed upon by economists. Transformation problem: The transformation problem is the problem specific to Marxist economics, and not to economics in general, of finding a general rule by which to transform the values of commodities based on socially necessary labour time into the competitive prices of the marketplace. The essential difficulty is how to reconcile profit in the form of surplus value from direct labour inputs and the ratio of direct labour input to capital input


id: list-of-unsolved-problems-in-economics-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_economics-1.md
category: reference
title: List of unsolved problems in economics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_economics
date_saved: 2026-05-05T08:28:08.644071+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-economics-20260505-0
summary:
Home bias in trade puzzle: The home bias in trade puzzle is an empirical observation that even when factors such as economic size of trading partners and the distance between them are considered, trade between regions within a given country is substantially greater than trade between regions in different countries, even when there are no substantial legal barriers. There is currently no framework to explain this observation. Equity home bias puzzle: This puzzle concerns the observation that individuals and institutions in many countries only hold modest amounts of foreign equity, despite the ability for vast diversification of their portfolios in the global economy. While some explanations do exist, such as that local individuals and firms have greater access to information about local firms and economic conditions, these explanations are not accepted by the majority of economists and have been mostly refuted. Backus–Kehoe–Kydland puzzle: The Backus–Kehoe–Kydland consumption correlation puzzle is the empirical observation that consumption is much less correlated across countries than output. Standard economic theory suggests that country-specific output risks should be collective and domestic consumption growth should not depend strongly on country-specific income shocks. Thus, we should not see the observation that consumption is much less correlated across countries


id: list-of-unsolved-problems-in-fair-division-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division-0.md
category: reference
title: List of unsolved problems in fair division
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division
date_saved: 2026-05-05T08:28:09.846628+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-fair-division-20260505-0
summary:
This page lists notable open problems related to fair division - a field in the intersection of mathematics, computer science, political science and economics. == Open problems in fair cake-cutting == === Query complexity of envy-free cake-cutting === In the problem of envy-free cake-cutting, there is a cake modeled as an interval, and n {\displaystyle n} agents with different value measures over the cake. The value measures are accessible only via queries of the form "evaluate a given piece of cake" or "mark a piece of cake with a given value". With n = 2 {\displaystyle n=2} agents, an envy-free division can be found using two queries, via divide and choose. With n > 2 {\displaystyle n>2} agents, there are several open problems regarding the number of required queries. 1. First, assume that the entire cake must be allocated (i.e., there is no disposal), and pieces may be disconnected. How many queries are required? Lower bound: Ω ( n 2 ) {\displaystyle \Omega (n^{2})} ; Upper bound: O ( n n n n n n ) {\displaystyle O\left(n^{n^{n^{n^{n^{n}}}}}\right)} . 2. Next, assume that some cake may be left unallocated (i.e., there is free disposal), but the allocation must be proportional


id: list-of-unsolved-problems-in-fair-division-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division-1.md
category: reference
title: List of unsolved problems in fair division
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division
date_saved: 2026-05-05T08:28:09.846628+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-fair-division-20260505-0
summary:
=== Approximate maximin-share fairness === The 1-of- n {\displaystyle n} maximin share (MMS) of an agent is the largest utility the agent can secure by partitioning the items into n {\displaystyle n} bundles and receiving the worst bundle. For two agents, divide and choose gives each agent at least his/her 1-of-2 MMS. For n > 2 {\displaystyle n>2} agents, it is almost always, but not always, possible to give each agent his/her 1-of- n {\displaystyle n} MMS. This raises several kinds of questions. ==== 1. Computational complexity ==== What is the runtime complexity of deciding whether a given instance admits a 1-of- n {\displaystyle n} MMS allocation? Upper bound: N P N P {\displaystyle {NP}^{NP}} (which is Σ 2 P {\displaystyle \Sigma _{2}^{P}} - level 2 in the polynomial hierarchy) Lower bound: none (so it may be level 2 or 1 or even 0 of the hierarchy). NOTE: the following related problems are known to be computationally hard: Calculating the 1-of- n {\displaystyle n} MMS of a given agent is NP-hard even if all agents have additive preferences (reduction from partition problem). Deciding whether a given allocation is 1-of- n {\displaystyle n} MMS is co-NP complete for agents with additive


id: list-of-unsolved-problems-in-fair-division-20260505-2
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division-2.md
category: reference
title: List of unsolved problems in fair division
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_fair_division
date_saved: 2026-05-05T08:28:09.846628+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-fair-division-20260505-0
summary:
==== Price of fairness ==== The price of fairness is the ratio between the maximum social welfare (sum of utilities) in any allocation, and the maximum social welfare in a fair allocation. What is the price of EF1 fairness? The upper bound is O ( n ) {\displaystyle O(n)} - by either Round-robin or maximum Nash welfare. The lower bound is O ( n ) {\displaystyle O({\sqrt {n}})} . === Existence of EFx allocation === An allocation is called EFx ("envy-free up to any good") if, for any two agents i {\displaystyle i} and j {\displaystyle j} , and for any good in the bundle of j {\displaystyle j} , if we remove that good from j {\displaystyle j} 's bundle then i {\displaystyle i} does not envy. For three agents with additive valuations, does there always exist an EFx allocation? For n {\displaystyle n} agents with general monotone valuations, can we prove that there does not exist an EFx allocation? Known cases: If at least n − 1 {\displaystyle n-1} valuations are identical: yes. Hence, for two agents: yes. This is true even for general monotone valuations. For three agents: yes, by a recent working paper. === Existence of


id: list-of-unsolved-problems-in-geoscience-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_geoscience-0.md
category: reference
title: List of unsolved problems in geoscience
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_geoscience
date_saved: 2026-05-05T08:28:11.045396+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-geoscience-20260505-0
summary:
This list provides references to notable unsolved problems in geoscience. == Early Earth and the Solar System == Was there ever a collision of Earth with the hypothesized planet of Theia, which gave birth to the Moon? There is compelling evidence, such as measures of a shorter duration of the Earth's rotation and lunar month in the past, that suggests the possibility that Earth's Moon was much closer to Earth during the early stages of Solar System formation. What is the long-term heat balance of Earth? How did its internal temperature decay since it formed by accretion of chondrites? How abundant are radiogenic elements in the interior? Did a "faint young Sun" ever warm a "snowball Earth"? and that is cause it formed on one of the earths langrage sharing it's orbit line == Topography and environment == Can the now widely available topographic data be used to derive past tectonic and climatic conditions (in the multi-million year scale)? Do we know enough about the erosion and transport processes? Does the stochasticity of meteorological and tectonic events reflect in the landscape? How much has life contributed to shape the Earth's surface? Can classical geomorphological concepts such as peneplanation or retrogressive


id: list-of-unsolved-problems-in-information-theory-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_information_theory-0.md
category: reference
title: List of unsolved problems in information theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_information_theory
date_saved: 2026-05-05T08:28:12.210120+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-information-theory-20260505-0
summary:
This article lists notable unsolved problems in information theory. These are separated into source coding and channel coding. There are also related unsolved problems in philosophy. == Channel coding == Capacity of a network: The capacity of a general wireless network is not known. There are some specific cases for which the capacity is known, such as the AWGN channel and fading channel. Capacity of the broadcast channel: The capacity of the broadcast channel, or the case in which a single transmitter is sending information to many receivers, is unknown in general, though it is known for several specific cases. Capacity of the interference channel (Two User): The capacity of the interference channel, in the case where there are two transmitter and receiver pairs that interfere among each other, is unknown in general. Capacity is known in special cases: strong interference regime, injective-deterministic. Capacity is known in approximate sense or within a range for: injective-semi-deterministic, additive white Gaussian noise with per block power constraint. Capacity of the two-way channel: The capacity of the two-way channel (a channel in which information is sent in both directions simultaneously) is unknown. Capacity of Aloha: The ALOHAnet used a very simple access scheme for


id: list-of-unsolved-problems-in-mathematics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-0.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, mathematical logic, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations. Some problems belong to more than one discipline and are studied using techniques from different areas. Prizes are often awarded for the solution to a long-standing problem, and some lists of unsolved problems, such as the Millennium Prize Problems, receive considerable attention. This list is a composite of notable unsolved problems mentioned in previously published lists, including but not limited to lists considered authoritative, and the problems listed here vary widely in both difficulty and importance. == Notable lists == Various mathematicians and organizations have published and promoted lists of unsolved mathematical problems. In some cases, the lists have been associated with prizes for the discoverers of solutions. === Millennium Prize Problems === Of the original seven Millennium Prize Problems listed by the Clay Mathematics Institute in 2000, six remain unsolved to date: Birch and Swinnerton-Dyer conjecture Hodge conjecture Navier–Stokes existence and smoothness P versus NP Riemann hypothesis Yang–Mills


id: list-of-unsolved-problems-in-mathematics-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-1.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Birch–Tate conjecture on the relation between the order of the center of the Steinberg group of the ring of integers of a number field to the field's Dedekind zeta function. Casas-Alvero conjecture: if a polynomial of degree d {\displaystyle d} defined over a field K {\displaystyle K} of characteristic 0 {\displaystyle 0} has a factor in common with its first through d − 1 {\displaystyle d-1} -th derivative, then must f {\displaystyle f} be the d {\displaystyle d} -th power of a linear polynomial? Connes embedding problem in Von Neumann algebra theory Crouzeix's conjecture: the matrix norm of a complex function f {\displaystyle f} applied to a complex matrix A {\displaystyle A} is at most twice the supremum of | f ( z ) | {\displaystyle |f(z)|} over the field of values of A {\displaystyle A} . Determinantal conjecture on the determinant of the sum of two normal matrices. Eilenberg–Ganea conjecture: a group with cohomological dimension 2 also has a 2-dimensional Eilenberg–MacLane space K ( G , 1 ) {\displaystyle K(G,1)} . Farrell–Jones conjecture on whether certain assembly maps are isomorphisms. Bost conjecture: a specific case of the Farrell–Jones conjecture Finite lattice representation problem: is every finite lattice isomorphic to


id: list-of-unsolved-problems-in-mathematics-20260505-2
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-2.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
The Brennan conjecture: estimating the integral powers of the moduli of the derivative of conformal maps into the open unit disk, on certain subsets of C {\displaystyle \mathbb {C} } Fuglede's conjecture on whether nonconvex sets in R {\displaystyle \mathbb {R} } and R 2 {\displaystyle \mathbb {R} ^{2}} are spectral if and only if they tile by translation. Goodman's conjecture on the coefficients of multivalued functions Invariant subspace problem – does every bounded operator on a complex Banach space send some non-trivial closed subspace to itself? Kung–Traub conjecture on the optimal order of a multipoint iteration without memory Lehmer's conjecture on the Mahler measure of non-cyclotomic polynomials The mean value problem: given a complex polynomial f {\displaystyle f} of degree d ≥ 2 {\displaystyle d\geq 2} and a complex number z {\displaystyle z} , is there a critical point c {\displaystyle c} of f {\displaystyle f} such that | f ( z ) − f ( c ) | ≤ | f ′ ( z ) | | z − c | {\displaystyle |f(z)-f(c)|\leq |f'(z)||z-c|} ? The Pompeiu problem on the topology of domains for which some nonzero function has integrals that vanish over every congruent copy Sendov's conjecture:


id: list-of-unsolved-problems-in-mathematics-20260505-3
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-3.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Sudoku: How many puzzles have exactly one solution? How many puzzles with exactly one solution are minimal? What is the maximum number of givens for a minimal puzzle? Tic-tac-toe variants: Given the width of a tic-tac-toe board, what is the smallest dimension such that X is guaranteed to have a winning strategy? (See also Hales–Jewett theorem and nd game) Chess: What is the outcome of a perfectly played game of chess? (See also first-move advantage in chess) Go: What is the perfect value of Komi? Set: What is the largest possible cap set, as a function of n {\displaystyle n} in the n {\displaystyle n} -dimensional affine space over the three-element field? Are the nim-sequences of all finite octal games eventually periodic? Is the nim-sequence of Grundy's game eventually periodic? ==== Games with imperfect information ==== Rendezvous problem === Geometry === ==== Algebraic geometry ==== Abundance conjecture: if the canonical bundle of a projective variety with Kawamata log terminal singularities is nef, then it is semiample. Bass conjecture on the finite generation of certain algebraic K-groups. Bass–Quillen conjecture relating vector bundles over a regular Noetherian ring and over the polynomial ring A [ t 1 , … , t n


id: list-of-unsolved-problems-in-mathematics-20260505-4
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-4.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
The spherical Bernstein's problem, a generalization of Bernstein's problem Carathéodory conjecture: any convex, closed, and twice-differentiable surface in three-dimensional Euclidean space admits at least two umbilical points. Cartan–Hadamard conjecture: can the classical isoperimetric inequality for subsets of Euclidean space be extended to spaces of nonpositive curvature, known as Cartan–Hadamard manifolds? Chern's conjecture (affine geometry) that the Euler characteristic of a compact affine manifold vanishes. Chern's conjecture for hypersurfaces in spheres, a number of closely related conjectures. Closed curve problem: find (explicit) necessary and sufficient conditions that determine when, given two periodic functions with the same period, the integral curve is closed. The filling area conjecture, that a hemisphere has the minimum area among shortcut-free surfaces in Euclidean space whose boundary forms a closed curve of given length The Hopf conjectures relating the curvature and Euler characteristic of higher-dimensional Riemannian manifolds Osserman conjecture: that every Osserman manifold is either flat or locally isometric to a rank-one symmetric space Yau's conjecture on the first eigenvalue that the first eigenvalue for the Laplace–Beltrami operator on an embedded minimal hypersurface of S n + 1 {\displaystyle S^{n+1}} is n {\displaystyle n} . ==== Discrete geometry ==== The big-line-big-clique conjecture on the existence of either


id: list-of-unsolved-problems-in-mathematics-20260505-5
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-5.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Falconer's conjecture: sets of Hausdorff dimension greater than d / 2 {\displaystyle d/2} in R d {\displaystyle \mathbb {R} ^{d}} must have a distance set of nonzero Lebesgue measure The values of the Hermite constants for dimensions other than 1–8 and 24 What is the lowest number of faces possible for a holyhedron? Inscribed square problem, also known as Toeplitz' conjecture and the square peg problem – does every Jordan curve have an inscribed square? The Kakeya conjecture – do n {\displaystyle n} -dimensional sets that contain a unit line segment in every direction necessarily have Hausdorff dimension and Minkowski dimension equal to n {\displaystyle n} ? The Kelvin problem on minimum-surface-area partitions of space into equal-volume cells, and the optimality of the Weaire–Phelan structure as a solution to the Kelvin problem Lebesgue's universal covering problem on the minimum-area convex shape in the plane that can cover any shape of diameter one Mahler's conjecture on the product of the volumes of a centrally symmetric convex body and its polar. In Meissner body): Are the two Meissner tetrahedra the minimum-volume three-dimensional shapes of constant width? Moser's worm problem – what is the smallest area of a shape that can cover every


id: list-of-unsolved-problems-in-mathematics-20260505-6
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-6.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
==== Graph drawing and embedding ==== The Albertson conjecture: the crossing number can be lower-bounded by the crossing number of a complete graph with the same chromatic number Conway's thrackle conjecture that thrackles cannot have more edges than vertices The GNRS conjecture on whether minor-closed graph families have ℓ 1 {\displaystyle \ell _{1}} embeddings with bounded distortion Harborth's conjecture: every planar graph can be drawn with integer edge lengths Negami's conjecture on projective-plane embeddings of graphs with planar covers The strong Papadimitriou–Ratajczak conjecture: every polyhedral graph has a convex greedy embedding Turán's brick factory problem – Is there a drawing of any complete bipartite graph with fewer crossings than the number given by Zarankiewicz? Guy's conjecture on the crossing number for complete graphs – Is there a drawing of any complete graph with fewer crossings than the number given by his upper bound? Universal point sets of subquadratic size for planar graphs ==== Restriction of graph parameters ==== Does there exist a conference graph for every number of vertices v > 1 {\displaystyle v>1} where v ≡ 1 mod 4 {\displaystyle v\equiv 1{\bmod {4}}} and v {\displaystyle v} is an odd sum of two squares? Conway's 99-graph problem: does there


id: list-of-unsolved-problems-in-mathematics-20260505-7
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-7.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
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==== Miscellaneous graph theory ==== Delta-conjecture (1978): consider a complete graph ( V ; E 1 , … , E d ) {\displaystyle (V;E_{1},\dots ,E_{d})} each edge of which is colored by one of d {\displaystyle d} colors such that there exists a triangle Δ {\displaystyle \Delta } colored in three pairwise distinct colors. Then, in each chromatic component ( V , E i ) , i = 1 , … , d {\displaystyle (V,E_{i}),i=1,\dots ,d} , one can choose a maximal independent vertex-set such that the intersection of the obtained d {\displaystyle d} sets is empty. The imbalance conjecture: If the imbalance for each edge of a graph is at least 1, is the multiset of all edge imbalances always graphic? The implicit graph conjecture on the existence of implicit representations for slowly-growing hereditary families of graphs Ryser's conjecture relating the maximum matching size and minimum transversal size in hypergraphs The second neighborhood problem: does every oriented graph contain a vertex for which there are at least as many other vertices at distance two as at distance one? Sidorenko's conjecture on homomorphism densities of graphs in graphons Teschner's bondage number conjecture: is the bondage number of a graph always


id: list-of-unsolved-problems-in-mathematics-20260505-8
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-8.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
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Büchi's problem on sufficiently large sequences of square numbers with constant second difference. Carmichael's totient function conjecture: do all values of Euler's totient function have multiplicity greater than 1 {\displaystyle 1} ? Catalan–Dickson conjecture on aliquot sequences: no aliquot sequences are infinite but non-repeating. Exponent pair conjecture: for all ε > 0 {\displaystyle \varepsilon >0} , is the pair ( ε , 1 / 2 + ε ) {\displaystyle (\varepsilon ,1/2+\varepsilon )} an exponent pair? The Gauss circle problem: how far can the number of integer points in a circle centered at the origin be from the area of the circle? Grimm's conjecture: each element of a set of consecutive composite numbers can be assigned a distinct prime number that divides it. Hall's conjecture: for any ε > 0 {\displaystyle \varepsilon >0} , there is some constant c ( ε ) {\displaystyle c(\varepsilon )} such that either y 2 = x 3 {\displaystyle y^{2}=x^{3}} or | y 2 − x 3 | > c ( ε ) x 1 / 2 − ε {\displaystyle |y^{2}-x^{3}|>c(\varepsilon )x^{1/2-\varepsilon }} . Lehmer's totient problem: if ϕ ( n ) {\displaystyle \phi (n)} divides n − 1 {\displaystyle n-1} , must n {\displaystyle n}


id: list-of-unsolved-problems-in-mathematics-20260505-9
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-9.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
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Leopoldt's conjecture: a p-adic analogue of the regulator of an algebraic number field does not vanish. Stark conjectures (including Brumer–Stark conjecture) Characterize all algebraic number fields that have some power basis. ==== Analytic number theory ==== Beilinson's conjectures about special values of L-functions. Do Siegel zeros exist? Find the value of the De Bruijn–Newman constant. Is Selberg class of Dirichlet series equal to class of automorphic L-functions? Hardy–Littlewood zeta function conjectures Keating–Snaith conjecture concerning the asymptotics of an integral involving the Riemann zeta function Hilbert–Pólya conjecture: the nontrivial zeros of the Riemann zeta function correspond to eigenvalues of a self-adjoint operator. Lindelöf hypothesis that for all ε > 0 {\displaystyle \varepsilon >0} , ζ ( 1 / 2 + i t ) = o ( t ε ) {\displaystyle \zeta (1/2+it)=o(t^{\varepsilon })} The density hypothesis for zeroes of the Riemann zeta function. Location of nontrivial zeros of L-functions, especially conjectures concerning their critical lines: Grand Riemann hypothesis: do the nontrivial zeros of all automorphic L-functions lie on the critical line 1 / 2 + i t {\displaystyle 1/2+it} with real t {\displaystyle t} ? Generalized Riemann hypothesis for Selberg class: do the nontrivial zeros of all functions in Selberg class


id: list-of-unsolved-problems-in-mathematics-20260505-10
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-10.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Littlewood conjecture: for any two real numbers α , β {\displaystyle \alpha ,\beta } , lim inf n → ∞ n ‖ n α ‖ ‖ n β ‖ = 0 {\displaystyle \liminf _{n\rightarrow \infty }n\,\Vert n\alpha \Vert \,\Vert n\beta \Vert =0} , where ‖ x ‖ {\displaystyle \Vert x\Vert } is the distance from x {\displaystyle x} to the nearest integer. Schanuel's conjecture on the transcendence degree of certain field extensions of the rational numbers. In particular: Are π {\displaystyle \pi } and e {\displaystyle e} algebraically independent? Which nontrivial combinations of transcendental numbers (such as e + π , e π , π e , π π , e e {\displaystyle e+\pi ,e\pi ,\pi ^{e},\pi ^{\pi },e^{e}} ) are themselves transcendental? The four exponentials conjecture: the transcendence of at least one of four exponentials of combinations of irrationals Are Euler's constant γ {\displaystyle \gamma } and Catalan's constant G {\displaystyle G} irrational? Are they transcendental? Is Apéry's constant ζ ( 3 ) {\displaystyle \zeta (3)} transcendental? Which transcendental numbers are (exponential) periods? How well can non-quadratic irrational numbers be approximated? What is the irrationality measure of specific (suspected) transcendental numbers such as π {\displaystyle \pi } and γ


id: list-of-unsolved-problems-in-mathematics-20260505-11
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-11.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Fortune's conjecture that no Fortunate number is composite. The Gaussian moat problem: is it possible to find an infinite sequence of distinct Gaussian prime numbers such that the difference between consecutive numbers in the sequence is bounded? Gillies' conjecture on the distribution of prime divisors of Mersenne numbers. Landau's problems Goldbach conjecture: all even natural numbers greater than 2 {\displaystyle 2} are the sum of two prime numbers. Legendre's conjecture: for every positive integer n {\displaystyle n} , there is a prime between n 2 {\displaystyle n^{2}} and ( n + 1 ) 2 {\displaystyle (n+1)^{2}} . Twin prime conjecture: there are infinitely many twin primes. Are there infinitely many primes of the form n 2 + 1 {\displaystyle n^{2}+1} ? Problems associated to Linnik's theorem New Mersenne conjecture: for any odd natural number p {\displaystyle p} , if any two of the three conditions p = 2 k ± 1 {\displaystyle p=2^{k}\pm 1} or p = 4 k ± 3 {\displaystyle p=4^{k}\pm 3} , 2 p − 1 {\displaystyle 2^{p}-1} is prime, and ( 2 p + 1 ) / 3 {\displaystyle (2^{p}+1)/3} is prime are true, then the third condition is also true. Polignac's conjecture: for all positive


id: list-of-unsolved-problems-in-mathematics-20260505-12
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-12.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Does the partition principle (PP) imply the axiom of choice (AC)? (Woodin) Does the generalized continuum hypothesis below a strongly compact cardinal imply the generalized continuum hypothesis everywhere? Does the generalized continuum hypothesis entail ♢ ( E cf ⁡ ( λ ) λ + ) {\displaystyle {\diamondsuit (E_{\operatorname {cf} (\lambda )}^{\lambda ^{+}}})} for every singular cardinal λ {\displaystyle \lambda } ? Does the generalized continuum hypothesis imply the existence of an ℵ2-Suslin tree? If ℵω is a strong limit cardinal, is 2 ℵ ω < ℵ ω 1 {\displaystyle 2^{\aleph _{\omega }}<\aleph _{\omega _{1}}} (see Singular cardinals hypothesis)? The best bound, ℵω4, was obtained by Shelah using his PCF theory. The problem of finding the ultimate core model, one that contains all large cardinals. Woodin's Ω-conjecture: if there is a proper class of Woodin cardinals, then Ω-logic satisfies an analogue of Gödel's completeness theorem. Does the consistency of the existence of a strongly compact cardinal imply the consistent existence of a supercompact cardinal? Does there exist a Jónsson algebra on ℵω? Is OCA (the open coloring axiom) consistent with 2 ℵ 0 > ℵ 2 {\displaystyle 2^{\aleph _{0}}>\aleph _{2}} ? Reinhardt cardinals: Without assuming the axiom of choice, can a


id: list-of-unsolved-problems-in-mathematics-20260505-13
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-13.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
=== Graph theory === Kahn–Kalai conjecture (Jinyoung Park and Huy Tuan Pham, 2022) Blankenship–Oporowski conjecture on the book thickness of subdivisions (Vida Dujmović, David Eppstein, Robert Hickingbotham, Pat Morin, and David Wood, 2021) Ringel's conjecture that the complete graph K 2 n + 1 {\displaystyle K_{2n+1}} can be decomposed into 2 n + 1 {\displaystyle 2n+1} copies of any tree with n {\displaystyle n} edges (Richard Montgomery, Benny Sudakov, Alexey Pokrovskiy, 2020) Disproof of Hedetniemi's conjecture on the chromatic number of tensor products of graphs (Yaroslav Shitov, 2019) Kelmans–Seymour conjecture (Dawei He, Yan Wang, and Xingxing Yu, 2020) Goldberg–Seymour conjecture (Guantao Chen, Guangming Jing, and Wenan Zang, 2019) Babai's problem (Alireza Abdollahi, Maysam Zallaghi, 2015) Alspach's conjecture (Darryn Bryant, Daniel Horsley, William Pettersson, 2014) Alon–Saks–Seymour conjecture (Hao Huang, Benny Sudakov, 2012) Read–Hoggar conjecture (June Huh, 2009) Scheinerman's conjecture (Jeremie Chalopin and Daniel Gonçalves, 2009) Erdős–Menger conjecture (Ron Aharoni, Eli Berger 2007) Road coloring conjecture (Avraham Trahtman, 2007) Robertson–Seymour theorem (Neil Robertson, Paul Seymour, 2004) Strong perfect graph conjecture (Maria Chudnovsky, Neil Robertson, Paul Seymour and Robin Thomas, 2002) Toida's conjecture (Mikhail Muzychuk, Mikhail Klin, and Reinhard Pöschel, 2001) Harary's conjecture on the integral sum number of complete graphs (Zhibo Chen,


id: list-of-unsolved-problems-in-mathematics-20260505-14
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-14.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T08:28:13.399347+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
=== Books discussing unsolved problems === Chung, Fan; Graham, Ron (1999). Erdös on Graphs: His Legacy of Unsolved Problems. AK Peters. ISBN 978-1-56881-111-6. Croft, Hallard T.; Falconer, Kenneth J.; Guy, Richard K. (1994). Unsolved Problems in Geometry. Springer. ISBN 978-0-387-97506-1. Guy, Richard K. (2004). Unsolved Problems in Number Theory. Springer. ISBN 978-0-387-20860-2. Klee, Victor; Wagon, Stan (1996). Old and New Unsolved Problems in Plane Geometry and Number Theory. The Mathematical Association of America. ISBN 978-0-88385-315-3. du Sautoy, Marcus (2003). The Music of the Primes: Searching to Solve the Greatest Mystery in Mathematics. Harper Collins. ISBN 978-0-06-093558-0. Derbyshire, John (2003). Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics. Joseph Henry Press. ISBN 978-0-309-08549-6. Devlin, Keith (2006). The Millennium Problems – The Seven Greatest Unsolved* Mathematical Puzzles Of Our Time. Barnes & Noble. ISBN 978-0-7607-8659-8. Blondel, Vincent D.; Megrestski, Alexandre (2004). Unsolved problems in mathematical systems and control theory. Princeton University Press. ISBN 978-0-691-11748-5. Ji, Lizhen; Poon, Yat-Sun; Yau, Shing-Tung (2013). Open Problems and Surveys of Contemporary Mathematics (volume 6 in the Surveys in Modern Mathematics series) (Surveys of Modern Mathematics). International Press of Boston. ISBN 978-1-57146-278-7. Waldschmidt, Michel (2004). "Open Diophantine Problems" (PDF). Moscow Mathematical Journal. 4 (1):


id: unsolved-problems-in-medicine-20260505-0
file: data/en.wikipedia.org/wiki/Unsolved_problems_in_medicine-0.md
category: reference
title: Unsolved problems in medicine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unsolved_problems_in_medicine
date_saved: 2026-05-05T08:28:14.566300+00:00
instance: kb-cron
parent: unsolved-problems-in-medicine-20260505-0
summary:
This article discusses notable unsolved problems in medicine. Many of the problems relate to how drugs work (the so-called mechanism of action), and to diseases with an unknown cause, the so-called idiopathic diseases. == Definition of "disease" == There is no overarching, clear definition of what a disease is. On one hand, there is a scientific definition which is tied to a physiological process, and on the other hand, there is the subjective suffering of a patient and the loss of their life quality. Both approaches do not need to match, and they can even be contradictory. For example, when a patient seeks medical help because of a severe flu, the doctor will not care about the specific virological and immunological process behind the clearly visible suffering. This is contrasted by many hemochromatosis patients who will neither see suffering nor a change in their life quality, while the disease-causing process is severe and often deadly if left untreated. Similarly, many cancers in their very early stages are asymptomatic (e.g. pancreatic cancer) and the patient still feels healthy, which delays seeking treatment. Sometimes, cultural factors also play a role in defining "disease". Erectile dysfunction was long seen as a negative but


id: list-of-unsolved-problems-in-neuroscience-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_neuroscience-0.md
category: reference
title: List of unsolved problems in neuroscience
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_neuroscience
date_saved: 2026-05-05T08:28:15.768254+00:00
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parent: list-of-unsolved-problems-in-neuroscience-20260505-0
summary:
The following is a list of notable unsolved problems in neuroscience. A problem is considered unsolved if no answer is known or if there is significant disagreement among experts about a proposed solution. == Consciousness == Consciousness: How can consciousness be defined? What is the neural basis of subjective experience, cognition, wakefulness, alertness, arousal, and attention? Binding problem: How exactly is it that objects, background, and abstract or emotional features are combined into a single experience? What is the neural basis of self? Quantum mind: Do quantum mechanical phenomena, such as entanglement and superposition, play an important part in the brain's function and can it explain critical aspects of consciousness? Is there a "hard problem of consciousness"? If so, how is it solved? Vertiginous question: Why is it that a specific subject of experience is "live" from a given perspective? What, if anything, is the function of consciousness? Problem of mental causation: How exactly do mental states cause intentional actions to happen? What is the nature and mechanism behind near-death experiences? How can death be defined? Can consciousness exist after death? If consciousness is generated by brain activity, then how do some patients with physically deteriorated brains suddenly gain a


id: list-of-philosophical-problems-20260505-0
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-0.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
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This is a list of some of the major problems in philosophy. == Philosophy of language == === Counterfactuals === A counterfactual statement is a conditional statement with a false antecedent. For example, the statement "If Joseph Swan had not invented the modern incandescent light bulb, then someone else would have invented it anyway" is a counterfactual, because, in fact, Joseph Swan invented the modern incandescent light bulb. The most immediate task concerning counterfactuals is that of explaining their truth-conditions. As a start, one might assert that background information is assumed when stating and interpreting counterfactual conditionals and that this background information is just every true statement about the world as it is (pre-counterfactual). In the case of the Swan statement, we have certain trends in the history of technology, the utility of artificial light, the discovery of electricity, and so on. We quickly encounter an error with this initial account: among the true statements will be "Joseph Swan did invent the modern incandescent light bulb." From the conjunction of this statement (call it "S") and the antecedent of the counterfactual ("¬S"), we can derive any conclusion, and we have the unwelcome result that any statement follows from any counterfactual


id: list-of-philosophical-problems-20260505-1
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-1.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
summary:
Foundationalism, which posits certain basic beliefs as self-justifying, thus halting the regress. Coherentism, which argues that beliefs are justified by their coherence with other beliefs. Susan Haack's foundherentism is a notable hybrid approach. Infinitism, proposed by Peter D. Klein, which views the infinite regress as unproblematic. Among contemporary epistemologists, reliabilism has emerged as the most widely accepted approach to addressing the problem of the criterion. Developed by philosophers like Alvin Goldman, reliabilism suggests that beliefs can be justified if they are produced by reliable cognitive processes, potentially avoiding the need for infinite justification. This view aligns well with naturalistic approaches to epistemology and has gained significant traction in recent decades. In practice, many philosophers find that there is often a discernible line between sufficient justification and excessive inquiry, allowing for practical epistemological investigations despite the theoretical challenges posed by the problem of the criterion. The debate surrounding this problem remains active, with various approaches offering different insights into the nature of knowledge and justification. === Problem of induction === Scottish philosopher David Hume first formulated the problem of induction, arguing there is no non-circular way to justify inductive reasoning. That is, reasoning based on inferring general conclusions from specific observations.


id: list-of-philosophical-problems-20260505-2
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-2.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
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The problem of universals refers to the question of whether properties exist, and if so, what they are. Properties are qualities or relations or names that two or more entities have in common. The various kinds of properties, such as qualities and relations, are referred to as universals. For instance, one can imagine three cup holders on a table that have in common the quality of being circular or exemplifying circularity, or bear the same name, "circular cup" or two daughters that have in common being the female offsprings of Frank. There are many such properties, such as being human, red, male or female, liquid, big or small, taller than, father of, etc. While philosophers agree that human beings talk and think about properties, they disagree on whether these universals exist in reality or merely in thought, speech and sight. === Principle of individuation === Related to the problem of universals, the principle of individuation is what individuates universals. === Sorites paradox === Otherwise known as the "paradox of the heap", the question regards how one defines a "thing." Is a bale of hay still a bale of hay if you remove one straw? If so, is it still a


id: list-of-philosophical-problems-20260505-3
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-3.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
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The question hinges on whether color is a product of the mind or an inherent property of objects. Whilst most philosophers will agree that color assignment corresponds to spectra of light frequencies, it is not at all clear whether the particular psychological phenomena of color are imposed on these visual signals by the mind, or whether such qualia are somehow naturally associated with their noumena. Another way to look at this question is to assume two people ("Fred" and "George" for the sake of convenience) see colors differently. That is, when Fred sees the sky, his mind interprets this light signal as blue. He calls the sky "blue." However, when George sees the sky, his mind assigns green to that light frequency. If Fred were able to step into George's mind, he would be amazed that George saw green skies. However, George has learned to associate the word "blue" with what his mind sees as green, and so he calls the sky "blue", because for him the color green has the name "blue." The question is whether blue must be blue for all people, or whether the perception of that particular color is assigned by the mind. This extends to


id: list-of-philosophical-problems-20260505-4
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-4.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
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=== Cognition and AI === The philosophy of artificial intelligence and cognition examines the nature and possibility of machine intelligence and consciousness. It intersects with cognitive science, philosophy of mind, and computer science. Major debates concern whether artificial systems can possess genuine understanding, how intelligence should be operationally defined, and whether computational processes can replicate or instantiate mental states. The main question this field confronts is whether an AI is capable of intentionality, or "the capacity to have a mental representation of or about a thing or a state of affairs". The potential answers to these questions have changed as artificial intelligence has advanced much throughout the past decade alone. Artificial intelligence in image recognition began as training the program to search for specific features and separate images into categories. More recently, AI has been developed to "learn" via artificial machine learning (AML), which receives visual data from various photos and then reconstructs an idea of what something looks like based on those original images. If the program itself determines its own idea of what something looks like due to the data it is given, one must consider if this is emblematic of intelligence. The first explorations into these questions


id: list-of-philosophical-problems-20260505-5
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-5.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
summary:
In philosophy, the problem of personal identity is concerned with how one is able to identify a single person over a time interval, dealing with such questions as, "What makes it true that a person at one time is the same thing as a person at another time?" or "What kinds of things are we persons?" A question related to the problem of personal identity is Benj Hellie's vertiginous question. The vertiginous question asks why, of all the subjects of experience out there, this one—the one corresponding to the human being referred to as Benj Hellie—is the one whose experiences are live? (The reader is supposed to substitute their own case for Hellie's.) Hellie's argument is closely related to Caspar Hare's theories of egocentric presentism and perspectival realism, of which several other philosophers have written reviews. Similar questions are also asked repeatedly by J. J. Valberg in justifying his horizonal view of the self. Tim S. Roberts refers to the question of why a particular organism out of all the organisms that happen to exist happens to be you as the "Even Harder Problem of Consciousness". The philosophical issues with personal identity have been extensively discussed by Thomas Nagel in


id: list-of-philosophical-problems-20260505-6
file: data/en.wikipedia.org/wiki/List_of_philosophical_problems-6.md
category: reference
title: List of philosophical problems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_philosophical_problems
date_saved: 2026-05-05T08:28:16.929670+00:00
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parent: list-of-philosophical-problems-20260505-0
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'The problem of demarcation' is an expression introduced by Karl Popper to refer to 'the problem of finding a criterion which would enable us to distinguish between the empirical sciences on the one hand, and mathematics and logic as well as "metaphysical" systems on the other'. Popper attributes this problem to Kant. Although Popper mentions mathematics and logic, other writers focus on distinguishing science from metaphysics. A prominent question in meta-philosophy is that of whether or not philosophical progress occurs and more so, whether such progress in philosophy is even possible. It has even been disputed, most notably by Ludwig Wittgenstein, whether genuine philosophical problems actually exist. The opposite has also been claimed, for example by Karl Popper, who held that such problems do exist, that they are solvable, and that he had actually found definite solutions to some of them. David Chalmers divides inquiry into philosophical progress in meta-philosophy into three questions. The Existence Question: is there progress in philosophy? The Comparison Question: is there as much progress in philosophy as in science? The Explanation Question: why isn't there more progress in philosophy? === Realism === Does a world independent of human beliefs and representations exist? Is such a


id: list-of-unsolved-problems-in-physics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-0.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
The following is a list of notable unsolved problems grouped into broad areas of physics. Some of the major unsolved problems in physics are theoretical, meaning that existing theories are currently unable to explain certain observed phenomena or experimental results. Others are experimental, involving challenges in creating experiments to test proposed theories or to investigate specific phenomena in greater detail. A number of important questions remain open in the area of physics beyond the Standard Model, such as the strong CP problem, determining the absolute mass of neutrinos, understanding matter–antimatter asymmetry, and identifying the nature of dark matter and dark energy. Another significant problem lies within the mathematical framework of the Standard Model itself, which remains inconsistent with general relativity. This incompatibility causes both theories to break down under extreme conditions, such as within known spacetime gravitational singularities like those at the Big Bang and at the centers of black holes beyond their event horizons. == Historical problems and lists == Isaac Newton in his book Opticks (first edition 1704), published a list of 31 queries about light. In 1900, Lord Kelvin in a speech identified two main issues in classical physics that represented "two clouds" for the physics of


id: list-of-unsolved-problems-in-physics-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-1.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
== Quantum gravity == Quantum gravity: Can quantum mechanics and general relativity be realized as a fully consistent theory (perhaps as a quantum field theory)? Is spacetime fundamentally continuous or discrete? Would a consistent theory involve a force mediated by a hypothetical graviton, or be a product of a discrete structure of spacetime itself (as in loop quantum gravity)? Are there deviations from the predictions of general relativity at very small or very large scales or in other extreme circumstances that flow from a quantum gravity mechanism? Black holes, black hole information paradox, and black hole radiation: Do black holes produce thermal radiation, as expected on theoretical grounds? Does this radiation contain information about their inner structure, as suggested by gauge–gravity duality, or not, as implied by Hawking's original calculation? If not, and black holes can evaporate away, what happens to the information stored in them (since quantum mechanics does not provide for the destruction of information)? Or does the radiation stop at some point, leaving black hole remnants? Is there another way to probe their internal structure somehow, if such a structure even exists? The cosmic censorship hypothesis and the chronology protection conjecture: Can singularities not hidden behind an


id: list-of-unsolved-problems-in-physics-20260505-2
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-2.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
Dark matter: What is the identity of dark matter? Is it a particle? If so, is it a WIMP, axion, the lightest superpartner (LSP), or some other particle? Or, are the phenomena attributed to dark matter the result of an alternate theory of gravity separate from general relativity altogether? Despite extensive research, the exact composition of dark matter remains unknown. It is inferred from gravitational effects on visible matter, radiation, and the universe's large-scale structure. Understanding its properties is crucial for a comprehensive understanding of the universe. Dark energy: What is the cause of the observed accelerating expansion of the universe (the de Sitter phase)? Are the observations rightly interpreted as the accelerating expansion of the universe, or are they evidence that the cosmological principle is false? Why is the energy density of the dark energy component of the same magnitude as the density of matter at present when the two evolve quite differently over time; could it be simply that we are observing at exactly the right time? Is dark energy a pure cosmological constant or are models of quintessence such as phantom energy applicable? Dark flow: Is a non-spherically-symmetric gravitational pull from outside the observable universe responsible for


id: list-of-unsolved-problems-in-physics-20260505-3
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-3.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
The QCD vacuum: Many of the equations in non-perturbative QCD are currently unsolved. These energies are the energies sufficient for the formation and description of atomic nuclei. How thus does low energy /non-pertubative QCD give rise to the formation of complex nuclei and nuclear constituents? Generations of matter: Why are there three generations of quarks and leptons? Is there a theory that can explain the masses of particular quarks and leptons in particular generations from first principles (a theory of Yukawa couplings)? Neutrino mass: What is the absolute mass of neutrinos? Are they Dirac or Majorana fermions? Is the mass hierarchy normal or inverted? Is the CP violating phase equal to 0? Reactor antineutrino anomaly: There is an anomaly in the existing body of data regarding the antineutrino flux from nuclear reactors around the world. Measured values of this flux appears to be only 94% of the value expected from theory. It is unknown whether this is due to unknown physics (such as sterile neutrinos), experimental error in the measurements, or errors in the theoretical flux calculations. Strong CP problem and axions: Why is the strong nuclear interaction invariant to parity and charge conjugation? Is Peccei–Quinn theory the solution to


id: list-of-unsolved-problems-in-physics-20260505-4
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-4.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
Solar cycle: How does the Sun generate its periodically reversing large-scale magnetic field? How do other solar-like stars generate their magnetic fields, and what are the similarities and differences between stellar activity cycles and that of the Sun? What caused the Maunder Minimum and other grand minima, and how does the solar cycle recover from a minima state? Coronal heating problem: Why is the Sun's corona (atmosphere layer) so much hotter than the Sun's surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models? Astrophysical jet: Why do only certain accretion discs surrounding certain astronomical objects emit relativistic jets along their polar axes? Why are there quasi-periodic oscillations in many accretion discs? Why does the period of these oscillations scale as the inverse of the mass of the central object? Why are there sometimes overtones, and why do these appear at different frequency ratios in different objects? Diffuse interstellar bands: What is responsible for the numerous interstellar absorption lines detected in astronomical spectra? Are they molecular in origin, and if so which molecules are responsible for them? How do they form? Supermassive black holes: What is the origin of the M–sigma relation between


id: list-of-unsolved-problems-in-physics-20260505-5
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-5.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
Quantum chromodynamics: What are the phases of strongly interacting matter, and what roles do they play in the evolution of the cosmos? What is the detailed partonic structure of the nucleons? What does QCD predict for the properties of strongly interacting matter? What determines the key features of QCD, and what is their relation to the nature of gravity and spacetime? Does QCD truly lack CP violations? Quark–gluon plasma: Where is the onset of deconfinement: 1) as a function of temperature and chemical potentials? 2) as a function of relativistic heavy-ion collision energy and system size? What is the mechanism of energy and baryon-number stopping leading to creation of quark-gluon plasma in relativistic heavy-ion collisions? Why is sudden hadronization and the statistical-hadronization model a near-to-perfect description of hadron production from quark–gluon plasma? Is quark flavor conserved in quark–gluon plasma? Are strangeness and charm in chemical equilibrium in quark–gluon plasma? Does strangeness in quark–gluon plasma flow at the same speed as up and down quark flavours? Why does deconfined matter show ideal flow? Specific models of quark–gluon plasma formation: Do gluons saturate when their occupation number is large? Do gluons form a dense system called colour glass condensate? What are the


id: list-of-unsolved-problems-in-physics-20260505-6
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-6.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
== Plasma physics == Plasma physics and fusion power: Fusion energy may potentially provide power from an abundant resource (e.g. hydrogen) without the type of radioactive waste that fission energy currently produces. However, can ionized gases (plasma) be confined long enough and at a high enough temperature to create fusion power? What is the physical origin of H-mode? The injection problem: Fermi acceleration is thought to be the primary mechanism that accelerates astrophysical particles to high energy. However, it is unclear what mechanism causes those particles to initially have energies high enough for Fermi acceleration to work on them. Alfvénic turbulence: In the solar wind and the turbulence in solar flares, coronal mass ejections, and magnetospheric substorms are major unsolved problems in space plasma physics. Ball lightning: the exact physical nature of this mystery in atmospheric electricity. == Biophysics == Abiogenesis: can life be created from physical processes alone? Stochasticity and robustness to noise in gene expression: How do genes govern our body, withstanding different external pressures and internal stochasticity? Certain models exist for genetic processes, but we are far from understanding the whole picture, in particular in development where gene expression must be tightly regulated. Quantitative study of the


id: list-of-unsolved-problems-in-physics-20260505-7
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics-7.md
category: reference
title: List of unsolved problems in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics
date_saved: 2026-05-05T08:28:18.131755+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-physics-20260505-0
summary:
=== High-energy physics/particle physics === Existence of pentaquarks (1964–2015): In July 2015, the LHCb collaboration at CERN identified pentaquarks in the Λ0b→J/ψK−p channel, which represents the decay of the bottom lambda baryon (Λ0b) into a J/ψ meson (J/ψ), a kaon (K−) and a proton (p). The results showed that sometimes, instead of decaying directly into mesons and baryons, the Λ0b decayed via intermediate pentaquark states. The two states, named P+c(4380) and P+c(4450), had individual statistical significances of 9 σ and 12 σ, respectively, and a combined significance of 15 σ—enough to claim a formal discovery. The two pentaquark states were both observed decaying strongly to J/ψp, hence must have a valence quark content of two up quarks, a down quark, a charm quark, and an anti-charm quark (uudcc), making them charmonium-pentaquarks. Existence of quark-gluon plasma, a new phase of matter was discovered and confirmed in experiments at CERN-SPS (2000), BNL-RHIC (2005) and CERN-LHC (2010). Higgs boson and electroweak symmetry breaking (1963–2012): The mechanism responsible for breaking the electroweak gauge symmetry, giving mass to the W and Z bosons, was solved with the discovery of the Higgs boson of the Standard Model, with the expected couplings to the weak bosons. No


id: list-of-unsolved-problems-in-statistics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_statistics-0.md
category: reference
title: List of unsolved problems in statistics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_statistics
date_saved: 2026-05-05T08:28:19.361016+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-statistics-20260505-0
summary:
There are many longstanding unsolved problems in mathematics for which a solution has still not yet been found. The notable unsolved problems in statistics are generally of a different flavor; according to John Tukey, "difficulties in identifying problems have delayed statistics far more than difficulties in solving problems." A list of "one or two open problems" (in fact 22 of them) was given by David Cox. == Inference and testing == How to detect and correct for systematic errors, especially in sciences where random errors are large (a situation Tukey termed uncomfortable science). The Graybill–Deal estimator is often used to estimate the common mean of two normal populations with unknown and possibly unequal variances. Though this estimator is generally unbiased, its admissibility remains to be shown. Meta-analysis: Though independent p-values can be combined using Fisher's method, techniques are still being developed to handle the case of dependent p-values. Behrens–Fisher problem: Yuri Linnik showed in 1966 that there is no uniformly most powerful test for the difference of two means when the variances are unknown and possibly unequal. That is, there is no exact test (meaning that, if the means are in fact equal, one that rejects the null hypothesis with


id: list-of-hypothetical-technologies-20260505-0
file: data/en.wikipedia.org/wiki/List_of_hypothetical_technologies-0.md
category: reference
title: List of hypothetical technologies
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_hypothetical_technologies
date_saved: 2026-05-05T08:28:20.536514+00:00
instance: kb-cron
parent: list-of-hypothetical-technologies-20260505-0
summary:
Hypothetical technologies are technologies that do not exist yet, but that could exist in the future. They are distinct from emerging technologies, which have achieved some developmental success. Emerging technologies as of 2018 include 3-D metal printing and artificial embryos. Many hypothetical technologies have been the subject of science fiction. The criteria for this list are that the technology: Must not exist yet Is credibly proposed to exist in the future (e.g. no perpetual motion machines) If the technology does not have an existing article (i.e. it is "redlinked"), a reference must be provided for it == Biology == == Engineering and manufacturing == === Computing and robotics === === Megastructures === === Nanotechnology === === Transport === == Minds and psychology == == Physics == === Nuclear energy and weaponry === === Space === == See also == == References ==


id: above-and-beyond-the-encyclopedia-of-aviation-and-space-sciences-20260505-0
file: data/en.wikipedia.org/wiki/Above_and_Beyond:_The_Encyclopedia_of_Aviation_and_Space_Sciences-0.md
category: reference
title: Above and Beyond: The Encyclopedia of Aviation and Space Sciences
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Above_and_Beyond:_The_Encyclopedia_of_Aviation_and_Space_Sciences
date_saved: 2026-05-05T08:28:22.035663+00:00
instance: kb-cron
parent: above-and-beyond-the-encyclopedia-of-aviation-and-space-sciences-20260505-0
summary:
Above and Beyond: The Encyclopedia of Aviation and Space Sciences was the first attempt at creating an encyclopedia of all matters related to the history, technology and aims of the aerospace industry as it existed in the late 1960s. Published in 1967 by New Horizons Publishers, Inc., of Chicago, this fourteen-volume collection was aimed primarily at teens and young adults. == References ==


id: aluminium-the-thirteenth-element-20260505-0
file: data/en.wikipedia.org/wiki/Aluminium:_The_Thirteenth_Element-0.md
category: reference
title: Aluminium: The Thirteenth Element
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aluminium:_The_Thirteenth_Element
date_saved: 2026-05-05T08:28:23.208203+00:00
instance: kb-cron
parent: aluminium-the-thirteenth-element-20260505-0
summary:
Aluminium: The Thirteenth Element (Russian: Алюминий. Тринадцатый элемент) is a Russian encyclopedia completely devoted to aluminium. The encyclopedia is published by United Company RUSAL, at the end of 2007, in both Russian and English. Four thousand copies were printed (240 pages). The encyclopedia covers various areas of aluminium application, starting from car engineering and architecture to jewellery and fashion, recounts how this metal was discovered, and describes technologies of its production, its properties and benefits for various spheres of life. The book consists of 9 chapters, with an index/glossary and name index enclosed at the end. The encyclopedia contains diversified illustrative materials stemming from Russia and from overseas photo archives, museums and private collections. == Contents == Chapter 1. The History of Aluminium Before the 19th Century. Historical background of aluminium in ancient times; archeological findings containing aluminium; first historic mentions of aluminium articles; information about 'alum' – compound substances with chemical structures containing aluminium; production technologies alum and areas of their application in the Ancient Times and Middle Ages. Chapter 2. How the Metal Was Discovered. Scientists and technologies associated with the first attempts to produce pure aluminium; the beginning of the industrial production of the metal and birth


id: american-beetles-20260505-0
file: data/en.wikipedia.org/wiki/American_Beetles-0.md
category: reference
title: American Beetles
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/American_Beetles
date_saved: 2026-05-05T08:28:24.383527+00:00
instance: kb-cron
parent: american-beetles-20260505-0
summary:
American Beetles is a comprehensive description of the beetles of North America north of the tropical area of Mexico. It was started by Ross H. Arnett, Jr. as an update of his classic The Beetles of the United States; along with Michael C. Thomas, he enlisted more than 60 specialists to write treatments of each family. The work outlived Arnett, and was published by CRC Press in 2001 (vol. 1) and 2002 (vol. 2). This is a highly technical book, with extensive references to the literature. The introduction includes a section on beetle anatomy that introduces all the technical terms used later. The bulk of the content consists of treatments of the 130-odd families known to occur in North America (a couple dozen are not known from North America, and are not described); the descriptive material applies worldwide, and there are brief notes about non-North American family members. A family treatment consists of a morphological description, including the larvae if known, habits and habitats, status of the classification, a key to the Nearctic genera (and sometimes species, if the family is small), and short treatments of the subtaxa. Every family gets at least one drawing of a member, and larger


id: encyclopedia-of-anthropology-20260505-0
file: data/en.wikipedia.org/wiki/Encyclopedia_of_Anthropology-0.md
category: reference
title: Encyclopedia of Anthropology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Encyclopedia_of_Anthropology
date_saved: 2026-05-05T08:28:25.512305+00:00
instance: kb-cron
parent: encyclopedia-of-anthropology-20260505-0
summary:
The Encyclopedia of Anthropology is an encyclopedia of anthropology edited by H. James Birx of Canisius College and SUNY Geneseo. The encyclopedia, published in 2006 by SAGE Publications, is in five volumes, and contains over 1,200 articles by more than 300 contributors. Entries include the main people, concepts, and theories, in anthropology, but also relevant topics from other disciplines, such as politics, psychology, linguistics, philosophy, and archaeology. == Sources and external links == H. James Birx [ed.] Encyclopedia of Anthropology (2006, SAGE Publications; ISBN 0-7619-3029-9) Reader's Guide — list of entries (PDF)


id: the-ants-20260505-0
file: data/en.wikipedia.org/wiki/The_Ants-0.md
category: reference
title: The Ants
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Ants
date_saved: 2026-05-05T08:28:26.641033+00:00
instance: kb-cron
parent: the-ants-20260505-0
summary:
The Ants is a zoology textbook by the German entomologist Bert Hölldobler and the American entomologist E. O. Wilson, first published in 1990. It won the Pulitzer Prize for General Nonfiction in 1991. == Contents == This book is primarily aimed at academics as a reference work, detailing the ants' anatomy, physiology, social organization including their caste system, altruistic behaviour, and chemical communication with pheromones, their ecology (vital for turning the soil and controlling insect pests), and natural history. An account of some of Hölldobler and Wilson's most interesting findings, popularized for the layman, can be found in their 1994 book Journey to the Ants. == Reception == The Science magazine reviewer described the book as a "mighty tome" and commented that it would "surely take its place among the greatest of all entomology books", as it was "a wonderful exploration of almost every ramification of evolutionary biology, from developmental biology to the structure of ecological communities". The illustrations are praised as lavish and extremely detailed, with monochrome drawings and 24 colour plates. All the 297 extant genera are illustrated and identifiable with the supplied keys. But "The Ants, like every great book and every ant colony, is much more


id: atlas-of-the-prehistoric-world-20260505-0
file: data/en.wikipedia.org/wiki/Atlas_of_the_Prehistoric_World-0.md
category: reference
title: Atlas of the Prehistoric World
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atlas_of_the_Prehistoric_World
date_saved: 2026-05-05T08:28:27.837231+00:00
instance: kb-cron
parent: atlas-of-the-prehistoric-world-20260505-0
summary:
Atlas of the Prehistoric World is a book written by Douglas Palmer. It was published in 1999 by Random House, Inc. It covers the last 620 million years. == References ==


id: bibliography-of-encyclopedias-biology-20260505-0
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-0.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
This is a list of encyclopedias as well as encyclopedic and biographical dictionaries published on the subject of biology in any language. Entries are in the English language unless specifically stated as otherwise. == General biology == Becher, Anne, Joseph Richey. American environmental leaders: From colonial times to the present. Grey House, 2008. ISBN 9781592371198. Butcher, Russell D., Stephen E. Adair, Lynn A. Greenwalt. America's national wildlife refuges: A complete guide. Roberts Rinehart Publishers in cooperation with Ducks Unlimited, 2003. ISBN 1570983798. Cullen, Katherine E. (2009). Encyclopedia of Life Science. Infobase Publishing. ISBN 978-0-8160-7008-4. Ecological Internet, Inc. EcoEarth.info: Environment portal and search engine. Ecological Internet, Inc. [1]. Encyclopedia of Life Sciences. John Wiley & Sons. 25 May 2007. ISBN 978-0-470-06651-5. Encyclopedia of Life Sciences. Groves Dictionaries Incorporated. 1 November 2001. ISBN 978-1-56159-238-8. Friday, Adrian & Davis S. Ingram. The Cambridge Encyclopedia of Life Sciences. Cambridge, 1985. Gaither, Carl C., Alma E. Cavazos-Gaither, Andrew Slocombe. Naturally speaking: A dictionary of quotations on biology, botany, nature and zoology. Institute of Physics, 2001. ISBN 0750306815. Gibson, Daniel, National Audubon Society. Audubon guide to the national wildlife refuges. Southwest: Arizona, Nevada, New Mexico, Texas. St. Martin's Griffin, 2000. ISBN 0312207778. Goudie, Andrew, David J.


id: bibliography-of-encyclopedias-biology-20260505-1
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-1.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
==== Animals ==== Audubon Society Encyclopedia of Animal Life. Clarkson N. Potter, 1982. Bekoff, Marc, Jane Goodall. Encyclopedia of animal behavior. Greenwood Press, 2004. ISBN 0313327459. Bruce, Jenni. The encyclopedia of animals: A complete visual guide. University of California Press, 2004. ISBN 0520244060. Burton, Maurice, Robert Burton. International wildlife encyclopedia. Marshall Cavendish, 2002. ISBN 0761472665. Encyclopedia of Animal Behavior. Facts on File, 1987. Encyclopedia of Animal Biology. Facts on File, 1987. Encyclopedia of Animal Ecology. Facts on File, 1987. Encyclopedia of Animal Evolution. Facts on File, 1987. Grzimek, Bernhard. Grzimek's Animal Life Encyclopedia. Van Nostrand, 1972–1975. Grzimek's Encyclopedia of Ethology. Van Nostrand, 1972–1977. The Illustrated Encyclopedia of Wildlife. Grey Castle Press, 1991. Knobil, Ernst and Jimmy D. Neill. Encyclopedia of reproduction. Academic Press, 1998. ISBN 0122270207. Macmillan Illustrated Animal Encyclopedia. Macmillan, 1984. Marshall Cavendish International Wildlife Encyclopedia. Marshall Cavendish, 1990. Nowak, Ronald M., David W. Macdonald, Roland W. Kays. Walker's carnivores of the world. Johns Hopkins University Press, 2005. ISBN 0801880335. The Oxford Companion to Animal Behaviour. Oxford, 1987. World Nature Encyclopedia. Raintree/Steck-Vaughn, 1989. ===== Aquatic ===== Banister, Keith & Andrew Campbell. The Encyclopedia of Aquatic Life. Facts on File, 1985. Dakin, Nick. Macmillan Book of the Marine Aquarium. Macmillan,


id: bibliography-of-encyclopedias-biology-20260505-2
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-2.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
===== Mammals ===== Beacham, Walton, Kirk H. Beetz. Beacham's guide to international endangered species. Beacham, 1998–2001. ISBN 0933833342. Elbroch, Mark. Mammal tracks and sign: A guide to North American species. Stackpole Books, 2003. ISBN 0811726266. Folkens, Pieter A., Randall R. Reeves, National Audubon Society. Guide to marine mammals of the world. A. A. Knopf, 2002. ISBN 0375411410. Grzimek, Bernhard. Grzimek's Encyclopedia of Mammals. McGraw-Hill, 2nd ed., 1990. ISBN 0079095089. Macdonald, David. Encyclopedia of Mammals. Facts on File, 2006. ISBN 0816064946. Mammals: A Multimedia Encyclopedia. National Geographic Society/IBM, 1990. Nowak, Ronald. Walker's Mammals of the World. Johns Hopkins University Press, 1991. ISBN 0801857899. Reid, Fiona, National Audubon Society. A field guide to mammals of North America, north of Mexico. Houghton Mifflin, 2006. ISBN 0395935962. Whitaker, John O., National Audubon Society. National Audubon Society field guide to North American mammals. Knopf, 1996. ISBN 0679446311. Wilson, Don E., Sue Ruff, American Society of Mammalogists. The Smithsonian book of North American mammals. Smithsonian Institution Press, 1999. ISBN 1560988452. ====== Canines ====== Alderton, David (September 2008). Encyclopedia of Dogs (Hardcover). Bath: Parragon Inc. p. 384. ISBN 978-1-4075-2438-2. American Kennel Club. The complete dog book: Official publication of the American Kennel Club. Ballantine Books, 2006. ISBN


id: bibliography-of-encyclopedias-biology-20260505-3
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-3.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
==== Plants ==== Bailey, Liberty Hyde & Ethel Zoe Bailey. Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Macmillan, 3rd ed., 1976. Barker, Joan. The encyclopedia of North American wild flowers. Parragon, 2004. ISBN 1405430354. Beckett, Kenneth A. The RHS Encyclopedia of House Plants Including Greenhouse Plants. Salem House, 1987. Brickell, Christopher. The American Horticultural Society Encyclopedia of Garden Plants. Macmillan, 1989. Brickell, Christopher, Trevor J. Cole, American Horticultural Society. American Horticultural Society encyclopedia of plants and flowers. DK Publishing, 2002. ISBN 0789489937. Burrows, George E. Toxic plants of North America. Wiley-Blackwell, 2012. ISBN 978-0-8138-2034-7, doi:10.1002/9781118413425. Dirr, Michael. Dirr's hardy trees and shrubs: An illustrated encyclopedia. Timber Press, 1997. ISBN 0881924040. Flora of North America Association. Flora of North America. Flora of North America Association. [17]. Flora of North America Editorial Committee. Flora of North America North of Mexico. Oxford University Press, 1993–2006. ISBN 0195057139. Gerard, John, Thomas Johnson. The herbal; or, General history of plants. Dover Publications, 1975. ISBN 048623147X. Graf, Alfred Byrd. Exotica Series 4 International: Pictorial Cyclopedia of Exotic Plants from Tropical and Near-Tropical Regions. Scribner's, 12th ed., 1985. Graf, Alfred Byrd. Hortica: A Color Cyclopedia of Garden Flora in All


id: bibliography-of-encyclopedias-biology-20260505-4
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-4.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
=== Biochemistry === Scott, Thomas A. & Mary Brewer. Concise Encyclopedia of Biochemistry. Walter de Gruyter, 2nd ed., 1988. === Bioethics === Post, Stephen Garrard. Encyclopedia of bioethics. Third edition. Macmillan Reference USA, 2003. ISBN 0028657748. ISSN 0950-4125; DOI:10.1108/09504120510573477. (5-Volume Set; 3062 pages). Reich, Warren Thomas Encyclopedia of Bioethics. First edition. New York: Free Press, 1978. ISBN 0029261805. ISBN 978-0029261804. (4-Volume Set; 1933 pages) Reich, Warren Thomas Encyclopedia of Bioethics. Second edition. New York: Free Press, 1982. (5-Volume Set; 2950 pages) Reich, Warren Thomas Encyclopedia of Bioethics. Third edition. New York: Simon & Schuster Macmillan, 1995; London: Simon and Schuster and Prentice Hall International, c1995. Rev. ed. (5-Volume Set; 2950 pages; 464 articles) ISBN 0028973550. ISBN 978-0028973555. === Food, nutrition, and agriculture === ==== Agriculture ==== American Veterinary Medical Association. AVMA: American Veterinary Medical Association. American Veterinary Medical Association, 2006-.[21]. Arntzen, Charles J. and Ellen M. Ritter. Encyclopedia of agricultural science. Academic Press, 1994. ISBN 0122266706. Bailey, Liberty Hyde. Cyclopedia of American agriculture. Macmillan, 1909. Bailey, L. H., Ethel Zoe Bailey, Liberty Hyde Bailey Hortorium. Hortus third: A concise dictionary of plants cultivated in the United States and Canada. Macmillan, 1976. ISBN 0025054708. Bains, William. Biotechnology from A to Z.


id: bibliography-of-encyclopedias-biology-20260505-5
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-5.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
===== Nutrition ===== Ensminger, Audrey H. Foods and Nutrition Encyclopedia. Pegus Press, 1983. Food for Health: A Nutrition Encyclopedia. Pegus Press, 1986. Margen, Sheldon. The Wellness Encyclopedia of Food and Nutrition: How to Buy, Store, and Prepare Every Variety of Fresh Food. Rebus, 1992. Mount Sinai School of Medicine Complete Book of Nutrition. St. Martin's Press, 1990. Tver, David F. and Percy Russell. Nutrition and Health Encyclopedia. 2nd ed., Van Nostrand, 1989. Winick, Myron. The Columbia Encyclopedia of Nutrition. Putnam, 1988. Yudin, John. Penguin Encyclopedia of Nutrition. Viking, 1985. ===== Wines, beers, and spirits ===== Alexis Lichine's New Encyclopedia of Wines and Spirits. 5th ed., Knopf, 1987. Grossman's Guide to Wines, Beers, & Spirits. 7th ed., Scribner's, 1983. Hugh Johnson's Modern Encyclopedia of Wine. 3rd ed., Simon & Schuster, 1991. Hugh Johnson's World Atlas of Wine. 3rd ed., Simon & Schuster, 1985. Robinson, Jancis. The Oxford companion to wine. Oxford University Press, 1999. ISBN 019866236X. Schoonmaker, Frank. The New Frank Schoonmaker Encyclopedia of Wine. Rev. ed., Morrow, 1988. === Health, medicine, and drugs === Adelman, George. Encyclopedia of Neuroscience. Birkhauser Boston, 1987. Fishbein, Morris. Fishbein's Illustrated Medical and Health Encyclopedia. H. S. Struttman, 1983. Who's who in medicine and healthcare.


id: bibliography-of-encyclopedias-biology-20260505-6
file: data/en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology-6.md
category: reference
title: Bibliography of encyclopedias: biology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bibliography_of_encyclopedias:_biology
date_saved: 2026-05-05T08:28:29.061385+00:00
instance: kb-cron
parent: bibliography-of-encyclopedias-biology-20260505-0
summary:
==== Medicine ==== Bailey, Hamilton, W. J. Bishop, Harold Ellis. Bailey and Bishop's notable names in medicine and surgery. Lewis, 1983. ISBN 0718604660. Bendiner, Jessica, Elmer Bendiner. Biographical dictionary of medicine. Facts on File, 1990. ISBN 0816018642. Berkow, Robert. The Merck Manual of Diagnosis and Therapy. 16th ed., Merck, 1992. Bremer, Sydney, Jeffrey H. Miller, William Broughton. Encyclopedia of genetics. Academic Press, 2002. ISBN 0122270800. Bynum, W. F., Helen Bynum. Dictionary of medical biography. Greenwood Press, 2006. ISBN 0313328773. Clayman, Charles B. The American Medical Association Encyclopedia of Medicine. Random House, 1989. Delves, Peter J., Ivan M. Roitt. Encyclopedia of immunology. Academic Press, 1998. ISBN 0122267656. Fischer, Isidor. Biographisches Lexikon der hervorragenden Ärzte der letzten 50 Jahre. 1932–33. Ganten, Detlev, Klaus Ruckpaul. Encyclopedic reference of genomics and proteomics in molecular medicine. Springer, 2005. ISBN 3540442448. Gomez, Joan. Dictionary of Symptoms. Rev. ed., Stein & Day, 1985. Griffith, H. Winter. Complete Guide to Symptoms, Illness & Surgery. 2nd ed., Price Stern Sloan, 1989. Hafner, Arthur Wayne, Fred W. Hunter, B. Michael Tarpey. Directory of deceased American physicians, 1804–1929: A genealogical guide to over 149,000 medical practitioners providing brief biographical sketches drawn from the American Medical Association's Deceased Physician Masterfile. American Medical


