For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years.
Radiocarbon dating measures radioactive isotopes in once-living organic material instead of rock, using the decay of carbon-14 to nitrogen-14.
The atoms of some chemical elements have different forms, called isotopes.
Because of their unique decay rates, different elements are used for dating different age ranges.Sedimentary rock is made of particles derived from other rocks, so measuring isotopes would date the original rock material, not the sediments they have ended up in.However, there are radiometric dating methods that can be used on sedimentary rock, including luminescence dating.a programmable electronic device designed for performing prescribed operations on data at high speed, esp. U., central processing unit, central processor, CPU, mainframe, processor - (computer science) the part of a computer (a microprocessor chip) that does most of the data processing; "the CPU and the memory form the central part of a computer to which the peripherals are attached"micro chip, microchip, microprocessor chip, silicon chip, chip - electronic equipment consisting of a small crystal of a silicon semiconductor fabricated to carry out a number of electronic functions in an integrated circuitdiskette, floppy, floppy disk - a small plastic magnetic disk enclosed in a stiff envelope with a radial slit; used to store data or programs for a microcomputer; "floppy disks are noted for their relatively slow speed and small capacity and low price"Computer parts analogue-digital converter, arithmetic logic unit or ALU, cartridge, case, CD-rewriter, CD-Rom drive, central processing unit or CPU, chip, coaxial cable, console, control key, counter, daisywheel, DDR-RAM, digital audio player, digital camera, digitizer, DIMM, disk, disk drive, disk unit, DRAM, DVD reader, DVD writer, emulator, encoder, flatbed scanner, floppy disk, graphics card, hard drive, integrated circuit, interface, joystick, keyboard, laser printer, LCD panel, line printer, magnetic tape unit or MTU, memory, microprocessor, modem, monitor, motherboard, mouse, MP3 player, multiplexor, optical character reader, optical disk, optical scanner, port, printed circuit board, printer, processor, scanner, screen, SDRAM, SIMM, sound card, speaker, trackball, transistor, USB port, visual display unit or VDU, webcam Computer terms 3D graphics, absolute address, access, access time, address, address bus, ADSL, algorithm, alpha-test, analogue computer, AND gate, applet, application program, architecture, archival storage, area, array, artificial intelligence or AI, ASCII, assemble, assembler, assembly language, audio response, automatic repeat, backbone, backing store, backup, bandwidth, base address, batch processing, beta-test, binary notation, bit or binary digit, black box, Bluetooth, bomb, boot or bootstrap, bottom-up processing, bpi (bits per inch), branch instruction, broadband, buffer, bug, bulletin board, bundle, bus or busbar, bus master, byte, cache memory, capture, CD-Rom, character, chipset, clip art, clock, code, COM, command, command language, communications, compatible, compiler, complex instruction set computer or CISC, computer-aided design or CAD, computer-aided design and manufacture or CADCAM, computer-aided engineering or CAE, computer-aided instruction or CAI, computer-aided (or -assisted) learning or CAL, computer-aided management or CAM, computer-aided manufacture or CAM, computer-aided teaching or CAT, computer aided trading or CAT, computerate, computer-based training or CBT, computer conferencing, computer graphics, computer input on microfilm or CIM, computer integrated manufacture or CIM, computerize, computer science, computer typesetting, concordance, concurrent processing, condition codes, configuration, constant, control commands, cookie, core memory, co-routine, corrupt, crash, cross assembler, cursor, cut and paste, cybercafé, cyberpunk, cyberspace, cycle, DAC, data, data bank, database, database management, databus, data capture, dataflow architecture, data processing, data protection, data structure, Datel (trademark), debugging, decision support system, decision table, default, desktop, desktop publishing or DTP, development system, device, digit, digital computer, digital fount, digital imaging, digital mapping, digital watermark, digitize, direct-access or random-access storage, direct memory access or DMA, directory, disassembler, distributed array processor, distributed logic, dithering, document, document reader, DOS or disk operating system (trademark), dot matrix, download, downsize, down time, dumb terminal, dump, dpi or dots per inch, driver, dump, duplex, EBCDIC or extended binary-coded decimal-interchange code, echo, ecommerce, edit, editor, EEPROM, electronic flight information systems, electronic mail or E-mail, electronic office, electronic publishing, emulator, encryption, error message, escape routine, exclusive OR circuit, exit, expansion slot, expert system, extranet, fail-safe, field, fifth-generation, file, file manager, filename, firewall, Fire Wire, firmware, flag, flops or floating-point operations per second, flowchart, freeware, front-end processor, FTP or file transfer protocol, function, function key, fuzzy, gate, gateway, gif, giga-, gigabyte, global search, graphical user interface, graphics, hacker, hand-held computer, handshake, hard card, hard copy, hardware, hard-wired, help screens, hexadecimal notation, high-level language, host, hot key, housekeeping, HTML, hybrid computer, hypermedia, hypertext, icon, idle time, image enhancement, incremental plotter, incremental recorder, infect, information technology, initialize, input, input device, input/output or I/O, install, instruction, intelligent knowledge-based system or IKBS, intelligent terminal, interactive, interactive video, Internet, interpreter, interrupt, intranet, ISDN, job, jpeg, key in, keyword, kilo-, kilobyte, LAN, language, lapheld, laptop, legacy, linked list, liveware, load, location, local area network, logic bomb, logic circuit, logic programming, login, log in, log out, loop, low-level language, machine code, machine learning, machine readable, machine translation, macro, magnetic bubble, mail bombing, mainframe, main memory, manager, mega-, megabyte, memory mapping, menu, menu-driven, microcomputer, microprocessor, midi, minicomputer, mobile device, module, morphing, MP3, mpeg, multiaccess, multiprogramming, multi-threaded, multi-user, NAND circuit or gate, network, neurocomputer or neural computer, node, NOR gate, notebook computer, NOT gate, object program, OEM or original equipment manufacturer, offline, online, open, operating system, optimize, OR gate, output, overflow, package, packet, packet-switching, palette, palmtop computer, parallel processing, parameter, parity check, parser, password, patch, patch board, PC or personal computer, PDA, pdf, personal computer or PC, pixel, platform, plug compatible, pointer, polymorphic function, portable, power down, power up, printout, procedure, process, program, program generator, programmable read only memory or PROM, programmer, programming language, program statement, prompt, protocol, query language, queue, queuing theory, random access memory or RAM, Random Instruction Set Computer or RISC, read in, read out, read only memory or ROM, real-time processing, reboot, record, remote access, rerun, reserved word, reset, restricted users group, retrieval, RISC or reduced instruction set computer, robustness, routine, run, run time, screensaver, scroll, SCSI or Small Computer Systems Interface, search engine, sense, sequential access, serial access memory or SAM, serial processing, server, SGML, shareware, shell program, skinning, smart card, software, software engineering, sort, source document, source program, speech recognition, spreadsheet, sprite, stack, statement, storage capacity, storage device, store, store and forward, string, subroutine, supercomputer, SWITCH, syntax, system, systems analysis, systems disk, teleprocessing, telesoftware, terabyte, terminal, tetrabyte, text processing, throughput, time out, time sharing, toggle, top-down processing, topology, transcribe, translator, transputer, tristate, turnkey system, underflow, UNIX (trademark), uptime, USB, user-defined key, user group, utility, vaccine, variable, virtual address, virtual memory, virtual reality, virtual storage, virus, visual programming, voice input, voice recognition, voice response, volatile memory, WAN, WAP, warez, webcasting, web development, wild card, window, windows icons menus pointers or WIMP, wizard, word, word processor, work station, World Wide Web, worm, WYSIWIG, XMLComputer scientists Ada, Countess of Lovelace (British), Howard Aiken (U. So why are they still showing up in the campus computer labs?
one housed with or linked to other devices for inputting, storing, retrieving, and displaying the data. S.), Charles Babbage (British), Tim Berners-Lee (English), Seymour Cray (U. When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.