# Concepts > The ideas the research turns on, defined in the site's own words, with every answer and method that uses them. Source: https://mysteriesdept.com/concepts Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) --- Concepts # 59 concepts The ideas the research turns on, defined in the site's own words, with every answer and method that uses them. Any field [Any field](https://mysteriesdept.com/concepts)[Cryptography](https://mysteriesdept.com/concepts?role=cryptography)[Linguistics](https://mysteriesdept.com/concepts?role=linguistics)[Astronomy](https://mysteriesdept.com/concepts?role=astronomy)[Writing systems](https://mysteriesdept.com/concepts?role=writing-systems)[Archaeometry](https://mysteriesdept.com/concepts?role=archaeometry)[Archaeology](https://mysteriesdept.com/concepts?role=archaeology)[Oceanography](https://mysteriesdept.com/concepts?role=oceanography)[Imaging](https://mysteriesdept.com/concepts?role=imaging)[Geology](https://mysteriesdept.com/concepts?role=geology)[Evidence](https://mysteriesdept.com/concepts?role=evidence)[Manuscript studies](https://mysteriesdept.com/concepts?role=manuscript-studies)[Radio astronomy](https://mysteriesdept.com/concepts?role=radio-astronomy)[Geophysics](https://mysteriesdept.com/concepts?role=geophysics)[Method](https://mysteriesdept.com/concepts?role=method) [All](https://mysteriesdept.com/concepts)[A](https://mysteriesdept.com/concepts?letter=A)[B](https://mysteriesdept.com/concepts?letter=B)[C](https://mysteriesdept.com/concepts?letter=C)[D](https://mysteriesdept.com/concepts?letter=D)[E](https://mysteriesdept.com/concepts?letter=E)[F](https://mysteriesdept.com/concepts?letter=F)[G](https://mysteriesdept.com/concepts?letter=G)[H](https://mysteriesdept.com/concepts?letter=H)[I](https://mysteriesdept.com/concepts?letter=I)J[K](https://mysteriesdept.com/concepts?letter=K)[L](https://mysteriesdept.com/concepts?letter=L)[M](https://mysteriesdept.com/concepts?letter=M)[N](https://mysteriesdept.com/concepts?letter=N)[O](https://mysteriesdept.com/concepts?letter=O)[P](https://mysteriesdept.com/concepts?letter=P)Q[R](https://mysteriesdept.com/concepts?letter=R)[S](https://mysteriesdept.com/concepts?letter=S)[T](https://mysteriesdept.com/concepts?letter=T)[U](https://mysteriesdept.com/concepts?letter=U)[V](https://mysteriesdept.com/concepts?letter=V)W[X](https://mysteriesdept.com/concepts?letter=X)Y[Z](https://mysteriesdept.com/concepts?letter=Z)# ## A 6 [A **Abjad** An alphabet that writes consonants only and leaves vowels to the reader. ](https://mysteriesdept.com/concepts/CPT0DEEBDB6Z0HG/abjad)[A **Acrophony** Giving a picture-sign the sound value of the first sound of the word for what it depicts. ](https://mysteriesdept.com/concepts/CPT0DEEBCCZWYE4/acrophony)[A **Airburst** A meteor exploding in the air before reaching the ground. ](https://mysteriesdept.com/concepts/CPT0DECW04CQFHJ/airburst)[AD **Ancient DNA** Genetic material recovered from old remains, read to tell who someone was and who they were related to. ](https://mysteriesdept.com/concepts/CPT0DECW01SRPE2/ancient-dna)[A **Archaeoastronomy** Testing whether a monument was aligned on the sky, and how. ](https://mysteriesdept.com/concepts/CPT0DECW06BRKCY/archaeoastronomy)[AF **Archaeological forgery** An object made or altered in modern times and presented as an ancient find, usually by planting it in the ground or in a collection. ](https://mysteriesdept.com/concepts/CPT0DEDZB86XVEY/archaeological-forgery) ## B 4 [BL **Ball lightning** A reported luminous sphere that floats for seconds during thunderstorms, not yet reproduced in the laboratory. ](https://mysteriesdept.com/concepts/CPT0DECW07S9ZXB/ball-lightning)[B **Bathymetry** The measured shape and depth of the sea floor. ](https://mysteriesdept.com/concepts/CPT0DECW07EH90Y/bathymetry)[BT **Bilingual text** The same text in two scripts or languages, the standard key to an unread one. ](https://mysteriesdept.com/concepts/CPT0DECW026HWD1/bilingual-text)[B **Boustrophedon** Writing in which the direction alternates line by line, right to left then left to right, often with the letters mirrored on the reversed li ](https://mysteriesdept.com/concepts/CPT0DEECXNF8DQC/boustrophedon) ## C 5 [CC **Calibration curve** The correction that turns a radiocarbon measurement into a calendar date. ](https://mysteriesdept.com/concepts/CPT0DECW019N8HS/calibration-curve)[CO **Chain of custody** The record of who held a piece of evidence, and when, from its finding to now. ](https://mysteriesdept.com/concepts/CPT0DECW073M56Z/chain-of-custody)[C **Codicology** The study of a book as an object: its parchment, quires, binding and marks of use. ](https://mysteriesdept.com/concepts/CPT0DECW064SH8S/codicology)[CM **Combinatory method** Working out what words in an unknown language mean from where they occur, what they occur with and how their endings change across many text ](https://mysteriesdept.com/concepts/CPT0DEECXD4TKNE/combinatory-method)[C **Crib** A piece of plaintext known or guessed to sit at a particular place in a cipher text. ](https://mysteriesdept.com/concepts/CPT0DECW00XAZGK/crib) ## D 5 [D **Decipherment** Working out how an unread script records a language, so that its texts can be read. ](https://mysteriesdept.com/concepts/CPT0DECW01ZWFP5/decipherment)[D **Dendrochronology** Dating wood by matching the pattern of its growth rings to a known sequence. ](https://mysteriesdept.com/concepts/CPT0DECW08CF5JB/dendrochronology)[DM **Dispersion measure** The delay of a radio burst's low frequencies, which tells how much plasma it crossed. ](https://mysteriesdept.com/concepts/CPT0DECW040R5CS/dispersion-measure)[DM **Drift modelling** Working back from where debris washed up to where it entered the water. ](https://mysteriesdept.com/concepts/CPT0DECW07M22AX/drift-modelling)[DS **Dyson sphere** A hypothetical structure built around a star to capture its energy. ](https://mysteriesdept.com/concepts/CPT0DECW03DJM9T/dyson-sphere) ## E 3 [ER **Electrical resistivity tomography** Imaging the ground by how it resists an electric current between electrodes. ](https://mysteriesdept.com/concepts/CPT0DECW04R3MN9/electrical-resistivity-tomography)[E **Entropy** A measure of how unpredictable a text's next sign is, given what came before. ](https://mysteriesdept.com/concepts/CPT0DECVZZSAC8F/entropy)[ET **Eyewitness testimony** What people say they saw, and what is known about how well that matches what happened. ](https://mysteriesdept.com/concepts/CPT0DECW06XVBA5/eyewitness-testimony) ## F 1 [FA **Frequency analysis** Reading a cipher by counting how often each sign appears and matching the counts to a language. ](https://mysteriesdept.com/concepts/CPT0DECVZZJW77N/frequency-analysis) ## G 2 [GC **Gromark cipher** A cipher that shifts each letter by a running numeric key made from a short seed. ](https://mysteriesdept.com/concepts/CPT0DECW00HS0D8/gromark-cipher)[GR **Ground-penetrating radar** Mapping what lies under the ground by bouncing radio pulses off buried surfaces. ](https://mysteriesdept.com/concepts/CPT0DECW04JAPJM/ground-penetrating-radar) ## H 2 [HT **Held-out test** Checking a reading or model on data that was not used to build it. ](https://mysteriesdept.com/concepts/CPT0DECW06RF522/held-out-test)[HS **Homophonic substitution** A cipher in which one plaintext letter can be written as any of several cipher signs. ](https://mysteriesdept.com/concepts/CPT0DECVZY0W38A/homophonic-substitution) ## I 1 [IH **Impact hypothesis** The proposal that a comet or asteroid strike caused a past event on Earth. ](https://mysteriesdept.com/concepts/CPT0DECW046HBQE/impact-hypothesis) ## K 1 [KA **Keyed alphabet** A cipher alphabet that starts with a key word and continues with the letters not yet used. ](https://mysteriesdept.com/concepts/CPT0DECW00PYYD3/keyed-alphabet) ## L 3 [LI **Language isolate** A language with no demonstrated relative, so its words and grammar cannot be worked out by comparison with a known family. ](https://mysteriesdept.com/concepts/CPT0DEEBNN2HBN9/language-isolate)[LC **Light curve** A star's brightness plotted against time. ](https://mysteriesdept.com/concepts/CPT0DECW02VSSXN/light-curve)[LS **Logographic script** A writing system whose signs stand for words or morphemes. ](https://mysteriesdept.com/concepts/CPT0DECW02H879M/logographic-script) ## M 1 [MI **Multispectral imaging** Photographing a surface in many bands of light to bring out what the eye cannot see. ](https://mysteriesdept.com/concepts/CPT0DECW04XSKZP/multispectral-imaging) ## N 4 [NS **Narrowband signal** A radio signal confined to a very small range of frequencies, which nature rarely makes. ](https://mysteriesdept.com/concepts/CPT0DECW03SJNS9/narrowband-signal)[N **Nomenclator** A cipher that pairs a substitution alphabet with a list of code groups for whole words and names. ](https://mysteriesdept.com/concepts/CPT0DECVZZ6JH82/nomenclator)[NA **Non-gravitational acceleration** A push on a body in orbit that gravity alone does not account for. ](https://mysteriesdept.com/concepts/CPT0DECW031ZQ1N/non-gravitational-acceleration)[NM **Null model** What the data would look like if nothing were going on, used to judge whether something is. ](https://mysteriesdept.com/concepts/CPT0DECW06JED24/null-model) ## O 1 [O **Outgassing** Gas escaping from a body as it warms, which can push it and make a tail. ](https://mysteriesdept.com/concepts/CPT0DECW037EHK5/outgassing) ## P 3 [P **Palaeography** Dating and placing a manuscript by the forms of its letters and the habits of its scribes. ](https://mysteriesdept.com/concepts/CPT0DECW05E35K0/palaeography)[P **Plasma** Gas hot or charged enough that its atoms have come apart into ions and electrons. ](https://mysteriesdept.com/concepts/CPT0DECW07YBYFA/plasma)[P **Proto-writing** A sign system that records information without recording the sounds or words of a language. ](https://mysteriesdept.com/concepts/CPT0DEDY0RSVT00/proto-writing) ## R 3 [RD **Radiocarbon dating** Dating organic material by how much of its carbon-14 has decayed. ](https://mysteriesdept.com/concepts/CPT0DECW013KR34/radiocarbon-dating)[RP **Rebus principle** Using the sign for one thing to write a different word that sounds the same. ](https://mysteriesdept.com/concepts/CPT0DEDY1N5MN91/rebus-principle)[RC **Running-key cipher** A polyalphabetic cipher whose key is a long text rather than a repeating word. ](https://mysteriesdept.com/concepts/CPT0DECW006275C/running-key-cipher) ## S 4 [SS **Side-scan sonar** Mapping the sea floor by sweeping it with sound from a towed instrument. ](https://mysteriesdept.com/concepts/CPT0DECW079FQPY/side-scan-sonar)[S **Steganography** Hiding a message so that nobody knows there is one, as distinct from making it unreadable. ](https://mysteriesdept.com/concepts/CPT0DECW0855NN3/steganography)[S **Stratigraphy** Reading the order of events from the order of the layers in the ground. ](https://mysteriesdept.com/concepts/CPT0DECW01M0SC0/stratigraphy)[S **Syllabary** A writing system whose signs stand for syllables rather than single sounds. ](https://mysteriesdept.com/concepts/CPT0DECW02C55EK/syllabary) ## T 5 [T **Tablature** Notation that says which strings or finger positions to play, not which pitches sound. ](https://mysteriesdept.com/concepts/CPT0DEE951HKQ42/tablature)[T **Technosignature** Any observable sign of technology beyond Earth. ](https://mysteriesdept.com/concepts/CPT0DECW03KAJAY/technosignature)[TD **Thermoluminescence dating** Dating fired clay or burnt stone by the light it stores since it was last heated. ](https://mysteriesdept.com/concepts/CPT0DECW01EV5D0/thermoluminescence-dating)[TP **Transit photometry** Finding and measuring things that pass in front of a star by the dip in its light. ](https://mysteriesdept.com/concepts/CPT0DECW02PHXR7/transit-photometry)[TC **Transposition cipher** A cipher that keeps the plaintext's letters and changes their order. ](https://mysteriesdept.com/concepts/CPT0DECVZZD5M0G/transposition-cipher) ## U 1 [UO **UD.GAL.NUN orthography** A spelling system in Early Dynastic Sumerian literary tablets that replaces common signs by others according to rules, named after three of ](https://mysteriesdept.com/concepts/CPT0DEDZ5HH5Q47/ud-gal-nun-orthography) ## V 2 [VC **Vigenère cipher** A substitution cipher that shifts each letter by a key word's letters in turn. ](https://mysteriesdept.com/concepts/CPT0DECW00CABZA/vigenere-cipher)[VU **Virtual unwrapping** Reading a rolled or damaged scroll from a CT scan without opening it. ](https://mysteriesdept.com/concepts/CPT0DECW058H0D6/virtual-unwrapping) ## X 1 [XF **X-ray fluorescence** Telling what elements a surface contains from the X-rays it gives off when illuminated. ](https://mysteriesdept.com/concepts/CPT0DECW0531CR4/x-ray-fluorescence) ## Z 1 [ZS **Zipf's law** In natural text, a word's frequency falls off in proportion to its rank. ](https://mysteriesdept.com/concepts/CPT0DECVZZZVP1M/zipfs-law)