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Thursday, June 26, 2025

Google Earth

From Wikipedia, the free encyclopedia
 
Google Earth
Original author(s)Keyhole, Inc.
Developer(s)Google
Initial releaseJune 10, 2001; 24 years ago
Stable release(s) [±]
Pro (Linux, macOS, and Windows)7.3.6 (Build 10201) / 14 January 2025; 5 months ago
Android10.83.0.1 / 12 June 2025; 13 days ago
iOS10.83.0.0 / 25 June 2025; 0 days ago
Web10.83.0.1 / 12 June 2025; 13 days ago
Preview release(s) [±]
Written inC++, Dart
Operating system
Available inVarious languages
TypeVirtual globe
LicenseFreeware
Websiteearth.google.com

Google Earth is a web and computer program created by Google that renders a 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposing satellite images, aerial photography, and GIS data onto a 3D globe, allowing users to see cities and landscapes from various angles. Users can explore the globe by entering addresses and coordinates, or by using a keyboard or mouse. The program can also be downloaded on a smartphone or tablet, using a touch screen or stylus to navigate. Users may use the program to add their own data using Keyhole Markup Language and upload them through various sources, such as forums or blogs. Google Earth is able to show various kinds of images overlaid on the surface of the Earth and is also a Web Map Service client. In 2019, Google revealed that Google Earth covers more than 97 percent of the world.

In addition to Earth navigation, Google Earth provides a series of other tools through the desktop application, including a measure distance tool. Additional globes for the Moon and Mars are available, as well as a tool for viewing the night sky. A flight simulator game is also included. Other features allow users to view photos from various places uploaded to Panoramio, information provided by Wikipedia on some locations, and Street View imagery. The web-based version of Google Earth also includes Voyager, a feature that periodically adds in-program tours, often presented by scientists and documentarians.

Google Earth has been viewed by some as a threat to privacy and national security, leading to the program being banned in multiple countries. Some countries have requested that certain areas be obscured in Google's satellite images, usually areas containing military facilities.

History

The core technology behind Google Earth was originally developed at Intrinsic Graphics in the late 1990s. At the time, the company was developing 3D gaming software libraries. As a demo of their 3D software, they created a spinning globe that could be zoomed into, similar to the Powers of Ten film. The demo was popular, but the board of Intrinsic wanted to remain focused on gaming, so in 1999, they created Keyhole, Inc., headed by John Hanke. Keyhole then developed a way to stream large databases of mapping data over the internet to client software, a key part of the technology, and acquired patchworks of mapping data from governments and other sources. The product, called "Keyhole EarthViewer", was sold on CDs for use in fields such as real estate, urban planning, defense, and intelligence; users paid a yearly fee for the service. Despite making several capital deals with Nvidia and Sony, the small company was struggling to pay and retain employees.

Fortunes for the company changed in early 2003 during the 2003 invasion of Iraq, when Dave Lorenzini (Director at Keyhole) enticed CNN, ABC, CBS and other major news networks to use their sophisticated 3D flyby imagery to illustrate Baghdad activities for viewers, in exchange for on-air attribution. During the invasion, It was used extensively by Miles O'Brien and other on-air broadcasters, allowing CNN and millions of viewers to follow the progress of the war in a way that had never been seen before. Public interest in the software exploded and Keyhole servers were not able to keep up with demand. Keyhole was soon contacted by the Central Intelligence Agency's venture capital firm, In-Q-Tel, and the National Geospatial-Intelligence Agency, for use with defense mapping databases, which gave Keyhole a much-needed cash infusion. Intrinsic Graphics was sold in 2003 to Vicarious Visions after its gaming libraries did not sell well, and its core group of engineers and management including Brian McClendon and Michael Jones transitioned to Keyhole with Hanke remaining at the head.

At the time, Google was finding that over 25% of its searches were of a geospatial character, including searches for maps and directions. In October 2004, Google acquired Keyhole as part of a strategy to better serve its users. Keyhole's Earth Viewer was the foundation for what became Google Earth in 2005 while other aspects of its core technology were integrated into Google Maps.

In 2021, Google replaced its layers feature with a new one on its Google Earth software. This replacement consolidated some layers, but also removed some layers and features.

Imagery

Google Earth's imagery is displayed on a digital globe, which displays the planet's surface using a single composited image from a far distance. After zooming in far enough, the imagery transitions into different imagery of the same area with finer detail, which varies in date and time from one area to the next. The imagery is retrieved from satellites or aircraft. Before the launch of NASA and the USGS's Landsat 8 satellite, Google relied partially on imagery from Landsat 7, which suffered from a hardware malfunction that left diagonal gaps in images. In 2013, Google used datamining to remedy the issue, providing what was described as a successor to the Blue Marble image of Earth, with a single large image of the entire planet. This was achieved by combining multiple sets of imagery taken from Landsat 7 to eliminate clouds and diagonal gaps, creating a single "mosaic" image. Google has since used myriad sources to provide imagery in a higher quality and with greater frequency. Imagery is hosted on Google's servers, which are contacted by the application when opened, requiring an Internet connection.

Imagery resolution ranges from 0.15 to 15 meters (0.49 to 49.21 ft) except for the ocean floor, which ranges from 100 to 1,000 meters (330 to 3,280 ft). For much of the Earth, Google Earth uses digital elevation model data collected by NASA's Shuttle Radar Topography Mission. This creates the impression of three-dimensional terrain, even where the imagery is only two-dimensional.

Google asserts that every image created from Google Earth using satellite data provided by Google Earth is a copyrighted map. Any derivative from Google Earth is made from data that Google claims copyright under United States Copyright Law. Google grants license to this data allowing, among other things, non-commercial personal use of the images (e.g., on a personal website or blog) as long as copyrights and attributions are preserved. By contrast, images created with NASA's globe software WorldWind use The Blue Marble, Landsat, or USGS imagery, each of which is in the public domain.

In version 5.0, Google introduced Historical Imagery, allowing users to view earlier imagery. Clicking the clock icon in the toolbar opens a time slider, which marks the time of available imagery from the past. This feature allows for observation of an area's changes over time. Utilizing the timelapse feature allows for the ability to view a zoom-able video as far back as 38 years.

3D imagery

Countries with 3D coverage in Google Earth as of May 2024:
  Countries with 3D coverage (55, including Hong Kong and Macau)
  Countries without 3D coverage
3D imagery in the iOS version of Google Earth, seen here at Wisconsin Dells, Wisconsin

Google Earth shows 3D building models in some cities, including photorealistic 3D imagery made using photogrammetry. The first 3D buildings in Google Earth were created using 3D modeling applications such as SketchUp and, beginning in 2009, Building Maker, and were uploaded to Google Earth via the 3D Warehouse. In June 2012, Google announced that it would be replacing user-generated 3D buildings with an auto-generated 3D mesh. This would be phased in, starting with select larger cities, with the notable exception of cities such as London and Toronto which required more time to process detailed imagery of their vast number of buildings. The reason given is to have greater uniformity in 3D buildings and to compete with Nokia Here and Apple Maps, which were already using this technology. The coverage began that year in 21 cities in four countries. By early 2016, 3D imagery had been expanded to hundreds of cities in over 40 countries, including every U.S. state and encompassing every continent except Antarctica.

In 2009, in a collaboration between Google and the Museo del Prado in Madrid, the museum selected 14 of its paintings to be photographed and displayed at the resolution of 14,000 megapixels inside the 3D version of the Prado in Google Earth and Google Maps.

Street View

On April 15, 2008, with version 4.3, Google fully integrated Street View into Google Earth. Street View displays 360° panoramic street-level photos of select cities and their surroundings. The photos were taken by cameras mounted on automobiles, can be viewed at different scales and from many angles, and are navigable by arrow icons imposed on them.

Using Street View on Google Earth, users can visit and explore 30 UNESCO World Heritage Sites with historical context and pins for each. The sites include the Great Pyramid, the Taj Mahal, Sagrada Família, the Dolomites, the Royal Botanic Gardens, Kew, and the Great Sphinx.

In 2019, Walt Disney World and Pixar partnered with Google to create Pixar Street View. A unique activation that enabled viewers to search for hidden Pixar Easter eggs inside Toy Story Land at Disney's Hollywood Studios through street view. This creative collaboration elevated Pixar's iconic tradition of hiding Easter eggs in films and introduced it to an immersive new platform.

Water and ocean

Introduced in Google Earth 5.0 in 2009, the Google Ocean feature allows users to zoom below the surface of the ocean and view the 3D bathymetry. Supporting over 20 content layers, it contains information from leading scientists and oceanographers. On April 14, 2009, Google added bathymetric data for the Great Lakes.

In June 2011, Google increased the resolution of some deep ocean floor areas from 1-kilometer grids to 100 meters. The high-resolution features were developed by oceanographers at Columbia University's Lamont–Doherty Earth Observatory from scientific data collected on research cruises. The sharper focus is available for about 5 percent of the oceans. This can be seen in the Hudson off New York City, the Wini Seamount near Hawaii, and the Mendocino Ridge off the U.S. Pacific coast.

Outer space

A picture of Martian landscape
Google Earth in sky-viewing mode
Apollo 11 lunar module Eagle and Tranquility Base as portrayed in Google Moon

Google has programs and features, including within Google Earth, allowing exploration of Mars, the Moon, the view of the sky from Earth and outer space, including the surfaces of various objects in the Solar System.

Google Sky

Google Sky is a feature that was introduced in Google Earth 4.2 on August 22, 2007, in a browser-based application on March 13, 2008, and to Android smartphones, with augmented reality features. Google Sky allows users to view stars and other celestial bodies. It was produced by Google through a partnership with the Space Telescope Science Institute (STScI) in Baltimore, the science operations center for the Hubble Space Telescope. Alberto Conti and his co-developer Carol Christian of STScI planned to add the public images from 2007, as well as color images of all of the archived data from Hubble's Advanced Camera for Surveys. Then-newly released Hubble pictures were added to the Google Sky program as soon as they were issued.

New features such as multi-wavelength data, positions of major satellites and their orbits as well as educational resources are provided to the Google Earth community and also through Christian and Conti's website for Sky. Also visible on Sky mode are constellations, stars, galaxies, and animations depicting the planets in their orbits. A real-time Google Sky mashup of recent astronomical transients, using the VOEvent protocol, is provided by the VOEventNet collaboration. Other programs similar to Google Sky include Microsoft WorldWide Telescope and Stellarium.

Google Mars

Google Mars is an application within Google Earth that is a version of the program for imagery of the planet Mars. Google also operates a browser-based version, although the maps are of a much higher resolution within Google Earth, and include 3D terrain, as well as infrared imagery and elevation data. There are also some extremely high-resolution images from the Mars Reconnaissance Orbiter's HiRISE camera that are of a similar resolution to those of the cities on Earth. Finally, there are many high-resolution panoramic images from various Mars landers, such as the Mars Exploration Rovers, Spirit and Opportunity, that can be viewed in a similar way to Google Street View.

Mars also has a small application found near the face on Mars. It is called Meliza, a robot character the user can speak with.

Google Moon

Originally a browser application, Google Moon is a feature that allows exploration of the Moon. Google brought the feature to Google Earth for the 40th anniversary of the Apollo 11 mission on July 20, 2009. It was announced and demonstrated to a group of invited guests by Google along with Buzz Aldrin at the Newseum in Washington, D.C. Google Moon includes several tours, including one for the Apollo missions, incorporating maps, videos, and Street View-style panoramas, all provided by NASA.

Other features

Google Earth has numerous features that allow the user to learn about specific places. These are called "layers", and include different forms of media, including photo and video. Some layers include tours, which guide the user between specific places in a set order. Layers are created using the Keyhole Markup Language, or KML, which users can also use to create customized layers. Locations can be marked with placemarks and organized in folders; For example, a user can use placemarks to list interesting landmarks around the globe, then provide a description with photos and videos, which can be viewed by clicking on the placemarks while viewing the new layer in the application.

In December 2006, Google Earth added a new integration with Wikipedia and Panoramio. For the Wikipedia layer, entries are scraped for coordinates via the Coord templates. There is also a community layer from the project Wikipedia-World. More coordinates are used, different types are in the display, and different languages are supported than the built-in Wikipedia layer. The Panoramio layer features pictures uploaded by Panoramio users, placed in Google Earth based on user-provided location data. In addition to flat images, Google Earth also includes a layer for user-submitted panoramic photos, navigable in a similar way to Street View.

Google Earth includes multiple features that allow the user to monitor current events. In 2007, Google began offering users the ability to monitor traffic data provided by Google Traffic in real-time, based on information crowdsourced from the GPS-identified locations of cell phone users.

Flight simulators

Downtown Toronto as seen from an F-16 Fighting Falcon during a simulated flight

In Google Earth 4.2, a flight simulator was added to the application. It was originally a hidden feature when introduced in 2007, but starting with 4.3, it was given a labeled option in the menu. In addition to keyboard control, the simulator can be controlled with a mouse or joystick. The simulator also runs with animation, allowing objects such as planes to animate while on the simulator.

Another flight simulator, GeoFS, was created under the name GEFS-Online using the Google Earth Plug-in API to operate within a web browser. As of September 1, 2015, the program now uses the open-source program CesiumJS, due to the Google Earth Plug-in being discontinued.

Liquid Galaxy

Liquid Galaxy is a cluster of computers running Google Earth creating an immersive experience. On September 30, 2010, Google made the configuration and schematics for their rigs public, placing code and setup guides on the Liquid Galaxy wiki. Liquid Galaxy has also been used as a panoramic photo viewer using KRpano, as well as a Google Street View viewer using Peruse-a-Rue Peruse-a-Rue is a method for synchronizing multiple Maps API clients.

Versions

Google Earth has been released on macOS, Linux, iOS, and Android. The Linux version began with the version 4 beta of Google Earth, as a native port using the Qt toolkit. The Free Software Foundation considers the development of a free compatible client for Google Earth to be a High Priority Free Software Project. Google Earth was released for Android on February 22, 2010, and on iOS on October 27, 2008. The mobile versions of Google Earth can make use of multi-touch interfaces to move on the globe, zoom or rotate the view, and allow to select the current location. An automotive version of Google Earth was made available in the 2010 Audi A8. On February 27, 2020, Google opened up its web-based version of Earth to browsers like Firefox, Edge, and Opera.

Version history
Version Release date Changes
1.0 June 10, 2001
1.4 January 2002
1.6 February 2003
1.7.2 October 2003
2.2 August 2004
  • Last version to support Windows 98 and ME
3.0 June 2005
  • The first version was released after Google acquired Keyhole, Inc.
4.0 June 2006
4.1 May 2007
4.2 August 2007
  • Google Sky was introduced
  • A flight simulator was added
4.3 April 2008
  • First release to implement KML version 2.2
  • Google Street View was added
  • Last version to support Windows 2000
  • Last version to support Mac OS X 10.3 Panther (PPC)
5.0 May 2009
  • Google Ocean was introduced
  • Historical Imagery was introduced
5.1 November 2009
5.2 July 2010
  • Last version to support Mac OS X 10.4 Tiger (PPC & Intel) and 10.5 Leopard (PPC)
6.0 March 2011
  • 3D Trees were added
6.1 October 2011
6.2 April 2012
  • Last version to support Mac OS X 10.5 Leopard (Intel)
7.0 December 2012
  • Support for 3D Imagery data was introduced
  • Tour Guide was introduced
7.1 April 2013
  • Last version to support Mac OS X 10.6 Snow Leopard and Mac OS X 10.7 Lion
  • Last version to support Windows XP and Windows Vista
7.3 July 2017
  • Google Earth Pro became the standard version of the desktop program. (A free license key was also publicly provided by Google for all the earlier Pro versions.)
  • The desktop application continues to be Google Earth Pro 7.3, with infrequent updates.
8.0 October 2014
  • Android-only update with new 3D rendering engine and feature to import KML files from Google Drive.
9.0 April 2017
  • Redesign of the mobile and web apps featuring Voyager, "I'm Feeling Lucky" button, and 3D mode.
  • iOS received update in August 2017.
10.0 September 2023
  • Mobile and web apps updated to latest Material Design theme with support for project creation. Voyager was removed from app.

Google Earth Pro

Google Earth running on Android

Google Earth Pro was originally the business-oriented upgrade to Google Earth, with features such as a movie maker and data importer. Up until late January 2015, it was available for $399/year, though Google decided to make it free to the public. Google Earth Pro is currently the standard version of the Google Earth desktop application as of version 7.3. The Pro version includes add-on software for movie making, advanced printing, and precise measurements, and is available for Windows, macOS, and Linux.

Google Earth Plus

Discontinued in December 2008, Google Earth Plus was a paid subscription upgrade to Google Earth that provided customers with the following features, most of which have become available in the free Google Earth. One such feature was GPS integration, which allowed users to read tracks and waypoints from a GPS device. A variety of third-party applications have been created which provide this functionality using the basic version of Google Earth by generating KML or KMZ files based on user-specified or user-recorded waypoints.

Google Earth Enterprise

Google Earth Enterprise is designed for use by organizations whose businesses could take advantage of the program's capabilities, for example by having a globe that holds company data available for anyone in that company. As of March 20, 2015, Google has retired the Google Earth Enterprise product, with support ended on March 22, 2017. Google Earth Enterprise allowed developers to create maps and 3D globes for private use, and host them through the platform. GEE Fusion, GEE Server, and GEE Portable Server source code was published on GitHub under the Apache2 license in March 2017.

Google Earth Studio

Google Earth Studio is a web-based version of Google Earth used for animations using Google Earth's 3D imagery. As of June 2021, it is preview-only and requires signing up to use it. It features keyframe animation, presets called "Quick-Start Projects", and 3D camera export.

Google Earth 9

Google Earth 9 is a version of Google Earth first released on April 18, 2017, having been in development for two years. The main feature of this version was the launching of a new web version of Google Earth. This version added the "Voyager" feature, whereby users can view a portal page containing guided tours led by scientists and documentarians. The version also added an "I'm Feeling Lucky" button, represented by a die, which takes the user to a random location on Earth along with showing them a "Knowledge Card" containing a short excerpt from the location's Wikipedia article.

Google Earth Plug-in

The Google Earth API was a free beta service, allowing users to place a version of Google Earth into web pages. The API enabled sophisticated 3D map applications to be built. At its unveiling at Google's 2008 I/O developer conference, the company showcased potential applications such as a game where the player controlled a milktruck atop a Google Earth surface. The Google Earth API has been deprecated as of December 15, 2014, and remained supported until December 15, 2015. Google Chrome ended support for the Netscape Plugin API (which the Google Earth API relies on) by the end of 2016.

Google Earth VR

On November 16, 2016, Google released a virtual reality version of Google Earth for Valve's Steam computer gaming platform. Google Earth VR allows users to navigate using VR controllers, and is currently compatible with the Oculus Rift and HTC Vive virtual reality headsets. On September 14, 2017, as part of Google Earth VR's 1.4 update, Google added Street View support.

Google Earth Outreach

Google Earth Outreach is a charity program, through which Google promotes and donates to various non-profit organizations. Beginning in 2007, donations are often accompanied by layers featured in Google Earth, allowing users to view a non-profit's projects and goals by navigating to certain related locations. Google Earth Outreach offers online training on using Google Earth and Google Maps for public education on issues affecting local regions or the entire globe. In June 2008, training was given to 20 indigenous tribes in the Amazon rainforest, such as the Suruí, to help them preserve their culture and raise awareness for the problem of deforestation.

Non-profit organizations featured in Google Earth via the Outreach program include Arkive, the Global Heritage Fund, WaterAid, and the World Wide Fund for Nature.[95][96]

Google Earth Engine

The Forest Landscape Integrity Index, created in Google Earth Engine

Google Earth Engine is a cloud computing platform for processing satellite imagery and other geospatial and observation data. It provides access to a large database of satellite imagery and the computational power needed to analyze those images. Google Earth Engine allows observation of dynamic changes in agriculture, natural resources, and climate using geospatial data from the Landsat satellite program, which passes over the same places on the Earth every sixteen days. Google Earth Engine has become a platform that makes Landsat and Sentinel-2 data easily accessible to researchers in collaboration with the Google Cloud Storage. Google Earth Engine provides a data catalog along with computers for analysis; this allows scientists to collaborate using data, algorithms, and visualizations. The platform provides Python and JavaScript application programming interfaces for making requests to the servers, and includes a graphical user interface for developing applications.

An early prototype of Earth Engine, based on the Carnegie Institute for Science's CLASlite system and Imazon's Sistema de Alerta de Desmatamento (SAD) was demonstrated in 2009 at COP15, and Earth Engine was officially launched in 2010 at COP16, along with maps of the water in the Congo Basin and forests in Mexico produced by researchers using the tool.

In 2013, researchers from University of Maryland produced the first high-resolution global forest cover and loss maps using Earth Engine, reporting an overall loss in global forest cover. Other early applications using Earth Engine spanned a diverse variety of topics, including: Tiger Habitat Monitoring, Malaria Risk Mapping, Global Surface Water, increases in vegetation around Mount Everest, and the annual Forest Landscape Integrity Index. Since then, Earth Engine has been used in the production of hundreds of scientific journal articles in many fields including: forestry and agriculture, hydrology, water quality monitoring and assessment, natural disaster monitoring and assessment, urban mapping, atmospheric and climate sciences and soil mapping.

Earth Engine has been free for academic and research purposes since its launch, but commercial use was prohibited until 2021, when Google announced a preview of Earth Engine as a commercial cloud offering and early adopters that included Unilever, USDA and Climate Engine.

Controversy and criticism

The software has been criticized by a number of special interest groups, including national officials, as being an invasion of privacy or posing a threat to national security. The typical argument is that the software provides information about military or other critical installations that could be used by terrorists. Google Earth has been blocked by Google in Iran and Sudan since 2007, due to United States government export restrictions. The program has also been blocked in Morocco since 2006 by Maroc Telecom, a major service provider in the country.

Blurred out image of the Royal Stables in The Hague, Netherlands. This has since been lifted.

In the academic realm, increasing attention has been devoted to both Google Earth and its place in the development of digital globes. In particular, the International Journal of Digital Earth features multiple articles evaluating and comparing the development of Google Earth and its differences when compared to other professional, scientific, and governmental platforms. Google Earth's role in the expansion of "Earth observing media" has been examined to understand how it is shaping a shared cultural consciousness regarding climate change and humanity's capacity to treat the Earth as an engineerable object.

Defense

National security

Other concerns

  • Operators of the Lucas Heights nuclear reactor in Sydney, New South Wales, Australia, asked Google to censor high-resolution pictures of the facility. They later withdrew the request.
  • In 2009, Google superimposed old woodblock prints of maps from 18th- and 19th-century Japan over Japan today. These maps marked areas inhabited by the burakumin caste, formerly known as eta (穢多), literally "abundance of defilement", who were considered "non-humans" for their "dirty" occupations, including leather tanning and butchery. Descendants of members of the burakumin caste still face discrimination today and many Japanese people feared that some would use these areas, labeled etamura (穢多村 "eta village"), to target current inhabitants of them. These maps are still visible on Google Earth, but with the label removed where necessary.
  • Late 2000s versions of Google Earth require a software component running in the background that will automatically download and install updates. Several users expressed concerns that there is not an easy way to disable this updater, as it runs without the permission of the user.
  • In February 2014, the Berlin-based ART+COM charged that Google Earth products infringe U.S. Patent No. RE44,550, entitled "Method and Device for Pictorial Representation of Space-related Data" and had remarkable similarity to Terravision which was developed by ART+COM in 1993 and patented in 1995. The court decided against Art+Com both at trial and on appeal because trial testimony showed that Art+Com was aware of an existing, substantially similar invention that it failed to mention as "prior art" in its patent application, thereby invalidating their patent. Stephen Lau, a former employee of federally funded, not-for-profit Stanford Research Institute ("SRI") testified that he helped develop SRI Terravision, an earth visualization application, and that he wrote 89% of the code. He further testified that he shared and discussed SRI Terravision code with Art+Com. Both systems used a multi-resolution pyramid of imagery to let users zoom from high to low altitudes, and both were called Terravision. Art+Com agreed to rename their product because SRI's came first. Stephen Lau died from COVID-19 in March 2020.

Google Earth is featured prominently in the 2021 German miniseries The Billion Dollar Code, which serves as a fictionalized account of a 2014 patent infringement lawsuit brought against Google by the German creators of Terravision. The series, which was shown on Netflix is prefaced by an episode of interviews with the ART+COM developers of Terravision and their legal representative.

One of the co-founders of Keyhole has published a first-hand account claiming to debunk the origins, timelines and interpretations depicted in the fictionalized miniseries. Not shown in the mini-series was that the patent owned by ART+COM and used to challenge Google was completely invalidated, after it was shown that another so-called TerraVision, this one at the Stanford Research Institute, predated ART+COM's ideas by several years.

Analytical engine

From Wikipedia, the free encyclopedia
Portion of the calculating machine with a printing mechanism of the analytical engine, built by Charles Babbage, as displayed at the Science Museum (London)

The analytical engine was a proposed digital mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage. It was first described in 1837 as the successor to Babbage's difference engine, which was a design for a simpler mechanical calculator.

The analytical engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete. In other words, the structure of the analytical engine was essentially the same as that which has dominated computer design in the electronic era. The analytical engine is one of the most successful achievements of Charles Babbage.

Babbage was never able to complete construction of any of his machines due to conflicts with his chief engineer and inadequate funding. It was not until 1941 that Konrad Zuse built the first general-purpose computer, Z3, more than a century after Babbage had proposed the pioneering analytical engine in 1837.

Design

Two types of punched cards used to program the machine. Foreground: 'operational cards', for inputting instructions; background: 'variable cards', for inputting data

Babbage's first attempt at a mechanical computing device, the difference engine, was a special-purpose machine designed to tabulate logarithms and trigonometric functions by evaluating finite differences to create approximating polynomials. Construction of this machine was never completed; Babbage had conflicts with his chief engineer, Joseph Clement, and ultimately the British government withdrew its funding for the project.

During this project, Babbage realised that a much more general design, the analytical engine, was possible. The work on the design of the analytical engine started around 1833.

The input, consisting of programs ("formulae") and data, was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. For output, the machine would have a printer, a curve plotter, and a bell. The machine would also be able to punch numbers onto cards to be read in later. It employed ordinary base-10 fixed-point arithmetic.

There was to be a store (that is, a memory) capable of holding 1,000 numbers of 40 decimal digits each (ca. 16.6 kB). An arithmetic unit (the "mill") would be able to perform all four arithmetic operations, plus comparisons and optionally square roots. Initially (1838) it was conceived as a difference engine curved back upon itself, in a generally circular layout, with the long store exiting off to one side. Later drawings (1858) depict a regularised grid layout. Like the central processing unit (CPU) in a modern computer, the mill would rely upon its own internal procedures, roughly equivalent to microcode in modern CPUs, to be stored in the form of pegs inserted into rotating drums called "barrels", to carry out some of the more complex instructions the user's program might specify.

The programming language to be employed by users was akin to modern day assembly languages. Loops and conditional branching were possible, and so the language as conceived would have been Turing-complete as later defined by Alan Turing. Three different types of punch cards were used: one for arithmetical operations, one for numerical constants, and one for load and store operations, transferring numbers from the store to the arithmetical unit or back. There were three separate readers for the three types of cards. Babbage developed some two dozen programs for the analytical engine between 1837 and 1840, and one program later. These programs treat polynomials, iterative formulas, Gaussian elimination, and Bernoulli numbers.

In 1842, the Italian mathematician Luigi Federico Menabrea published a description of the engine in French, based on lectures Babbage gave when he visited Turin in 1840. In 1843, the description was translated into English and extensively annotated by Ada Lovelace, who had become interested in the engine eight years earlier. In recognition of her additions to Menabrea's paper, which included a way to calculate Bernoulli numbers using the machine (widely considered to be the first complete computer program), she has been described by many as the first computer programmer, although others have challenged this view.

Construction

Late in his life, Babbage sought ways to build a simplified version of the machine, and assembled a small part of it before his death in 1871.

In 1878, a committee of the British Association for the Advancement of Science described the analytical engine as "a marvel of mechanical ingenuity", but recommended against constructing it. The committee acknowledged the usefulness and value of the machine, but could not estimate the cost of building it, and were unsure whether the machine would function correctly after being built.

Henry Babbage's analytical engine mill, built in 1910, in the Science Museum (London)

Intermittently from 1880 to 1910, Babbage's son Henry Prevost Babbage was constructing a part of the mill and the printing apparatus. In 1910, it was able to calculate a (faulty) list of multiples of pi. This constituted only a small part of the whole engine; it was not programmable and had no storage. (Popular images of this section have sometimes been mislabelled, implying that it was the entire mill or even the entire engine.) Henry Babbage's "analytical engine mill" is on display at the Science Museum in London. Henry also proposed building a demonstration version of the full engine, with a smaller storage capacity: "perhaps for a first machine ten (columns) would do, with fifteen wheels in each". Such a version could manipulate 20 numbers of 25 digits each, and what it could be told to do with those numbers could still be impressive. "It is only a question of cards and time", wrote Henry Babbage in 1888, "... and there is no reason why (twenty thousand) cards should not be used if necessary, in an analytical engine for the purposes of the mathematician".

In 1991, the London Science Museum built a complete and working specimen of Babbage's Difference Engine No. 2, a design that incorporated refinements Babbage discovered during the development of the analytical engine. This machine was built using materials and engineering tolerances that would have been available to Babbage, quelling the suggestion that Babbage's designs could not have been produced using the manufacturing technology of his time.

In October 2010, John Graham-Cumming started a "Plan 28" campaign to raise funds by "public subscription" to enable serious historical and academic study of Babbage's plans, with a view to then build and test a fully working virtual design which will then in turn enable construction of the physical analytical engine. As of May 2016, actual construction had not been attempted, since no consistent understanding could yet be obtained from Babbage's original design drawings. In particular it was unclear whether it could handle the indexed variables which were required for Lovelace's Bernoulli program. By 2017, the "Plan 28" effort reported that a searchable database of all catalogued material was available, and an initial review of Babbage's voluminous Scribbling Books had been completed.

Many of Babbage's original drawings have been digitised and are publicly available online.

Instruction set

Plan diagram of the analytical engine from 1840

Babbage is not known to have written down an explicit set of instructions for the engine in the manner of a modern processor manual. Instead he showed his programs as lists of states during their execution, showing what operator was run at each step with little indication of how the control flow would be guided.

Allan G. Bromley has assumed that the card deck could be read in forwards and backwards directions as a function of conditional branching after testing for conditions, which would make the engine Turing-complete:

...the cards could be ordered to move forward and reverse (and hence to loop)...

The introduction for the first time, in 1845, of user operations for a variety of service functions including, most importantly, an effective system for user control of looping in user programs. There is no indication how the direction of turning of the operation and variable cards is specified. In the absence of other evidence I have had to adopt the minimal default assumption that both the operation and variable cards can only be turned backward as is necessary to implement the loops used in Babbage's sample programs. There would be no mechanical or microprogramming difficulty in placing the direction of motion under the control of the user.

In their emulator of the engine, Fourmilab say:

The Engine's Card Reader is not constrained to simply process the cards in a chain one after another from start to finish. It can, in addition, directed by the very cards it reads and advised by whether the Mill's run-up lever is activated, either advance the card chain forward, skipping the intervening cards, or backward, causing previously-read cards to be processed once again.

This emulator does provide a written symbolic instruction set, though this has been constructed by its authors rather than based on Babbage's original works. For example, a factorial program would be written as:

N0 6
N1 1
N2 1
×
L1
L0
S1
–
L0
L2
S0
L2
L0
CB?11

where the CB is the conditional branch instruction or "combination card" used to make the control flow jump, in this case backward by 11 cards.

Influence

Predicted influence

Babbage understood that the existence of an automatic computer would kindle interest in the field now known as algorithmic efficiency, writing in his Passages from the Life of a Philosopher, "As soon as an analytical engine exists, it will necessarily guide the future course of the science. Whenever any result is sought by its aid, the question will then arise—By what course of calculation can these results be arrived at by the machine in the shortest time?"

Computer science

From 1872, Henry continued diligently with his father's work and then intermittently in retirement in 1875.

Percy Ludgate wrote about the engine in 1914 and published his own design for an analytical engine in 1909. It was drawn up in detail, but never built, and the drawings have never been found. Ludgate's engine would be much smaller (about 230 L (8.1 cu ft) than Babbage's, and hypothetically would be capable of multiplying two 20-decimal-digit numbers in about six seconds.

In his work Essays on Automatics (1914) Leonardo Torres Quevedo, inspired by Babbage, designed a theoretical electromechanical calculating machine which was to be controlled by a read-only program. The paper also contains the idea of floating-point arithmetic. In 1920, to celebrate the 100th anniversary of the invention of the arithmometer, Torres presented in Paris the electromechanical arithmometer, which consisted of an arithmetic unit connected to a (possibly remote) typewriter, on which commands could be typed and the results printed automatically.

Vannevar Bush's paper Instrumental Analysis (1936) included several references to Babbage's work. In the same year he started the Rapid Arithmetical Machine project to investigate the problems of constructing an electronic digital computer.

Despite this groundwork, Babbage's work fell into historical obscurity, and the analytical engine was unknown to builders of electromechanical and electronic computing machines in the 1930s and 1940s when they began their work, resulting in the need to re-invent many of the architectural innovations Babbage had proposed. Howard Aiken, who built the quickly-obsoleted electromechanical calculator, the Harvard Mark I, between 1937 and 1945, praised Babbage's work likely as a way of enhancing his own stature, but knew nothing of the analytical engine's architecture during the construction of the Mark I, and considered his visit to the constructed portion of the analytical engine "the greatest disappointment of my life". The Mark I showed no influence from the analytical engine and lacked the analytical engine's most prescient architectural feature, conditional branchingJ. Presper Eckert and John W. Mauchly similarly were not aware of the details of Babbage's analytical engine work prior to the completion of their design for the first electronic general-purpose computer, the ENIAC.

Comparison to other early computers

If the analytical engine had been built, it would have been digital, programmable and Turing-complete. It would, however, have been very slow. Luigi Federico Menabrea reported in Sketch of the Analytical Engine: "Mr. Babbage believes he can, by his engine, form the product of two numbers, each containing twenty figures, in three minutes". By comparison the Harvard Mark I could perform the same task in just six seconds (though it is debatable that computer is Turing complete; the ENIAC, which is, would also have been faster). A modern CPU could do the same thing in under a billionth of a second.

Name First operational Numeral system Computing mechanism Programming Turing complete Memory
Difference engine Not built until the 1990s (design 1820s) Decimal Mechanical Not programmable; initial numerical constants of polynomial differences set physically No Physical state of wheels in axes
Analytical engine Not built (design 1830s) Decimal Mechanical Program-controlled by punched cards Yes (design; not built, yet) Physical state of wheels in axes
Ludgate's analytical engine Not built (design 1909) Decimal Mechanical Program-controlled by punched cards Yes (not built) Physical state of rods
Torres' analytical machine 1920 Decimal Electro-mechanical Not programmable; input and output settings specified by patch cables No Mechanical relays
Zuse Z1 (Germany) 1939 Binary floating point Mechanical Not programmable; cipher input settings specified by patch cables No Physical state of rods
Bombe (Poland, UK, US) 1939 (Polish), March 1940 (British), May 1943 (US) Character computations Electro-mechanical Not programmable; cipher input settings specified by patch cables No Physical state of rotors
Zuse Z2 (Germany) 1940 Binary fixed point Electro-mechanical (mechanical memory) Program-controlled by punched 35 mm film stock (no conditional branch) No Physical state of rods
Zuse Z3 (Germany) May 1941 Binary floating point Electro-mechanical Program-controlled by punched 35 mm film stock (but no conditional branch) In theory (1998) Mechanical relays
Atanasoff–Berry computer (US) 1942 Binary Electronic Not programmable; linear system coefficients input using punched cards No Regenerative capacitor memory
Colossus Mark 1 (UK) December 1943 Binary Electronic Program-controlled by patch cables and switches No Thermionic valves (vacuum tubes) and thyratrons
Harvard Mark I – IBM ASCC (US) May 1944 Decimal Electro-mechanical Program-controlled by 24-channel punched paper tape (but no conditional branch) Debatable Mechanical relays
Colossus Mark 2 (UK) 1 June 1944 Binary Electronic Program-controlled by patch cables and switches Conjectured
Zuse Z4 (Germany) March 1945 (or 1948) Binary floating point Electro-mechanical Program-controlled by punched 35 mm film stock In 1950 Mechanical relays
ENIAC (US) December 1945 Decimal Electronic Program-controlled by patch cables and switches Yes Vacuum tube triode flip-flops
Manchester Baby (UK) June 1948 Binary Electronic Binary program entered into memory by keyboard (first electronic stored-program digital computer) Yes Williams cathode ray tube
EDSAC (UK) May 1949 Binary Electronic Five-bit opcode and variable-length operand (first stored-program computer offering computing services to a wide community). Yes Mercury delay lines
  • The cyberpunk novelists William Gibson and Bruce Sterling co-authored a steampunk novel of alternative history titled The Difference Engine in which Babbage's difference and analytical engines became available to Victorian society. The novel explores the consequences and implications of the early introduction of computational technology.
  • Moriarty by Modem, a short story by Jack Nimersheim, describes an alternative history where Babbage's analytical engine was indeed completed and had been deemed highly classified by the British government. The characters of Sherlock Holmes and Moriarty had in reality been a set of prototype programs written for the analytical engine. This short story follows Holmes as his program is implemented on modern computers and he is forced to compete against his nemesis yet again in the modern counterparts of Babbage's analytical engine.
  • A similar setting to The Difference Engine is used by Sydney Padua in the webcomic The Thrilling Adventures of Lovelace and Babbage[ It features an alternative history where Ada Lovelace and Babbage have built the analytical engine and use it to fight crime at Queen Victoria's request. The comic is based on thorough research on the biographies of and correspondence between Babbage and Lovelace, which is then twisted for humorous effect.
  • The Orion's Arm online project features the Machina Babbagenseii, fully sentient Babbage-inspired mechanical computers. Each is the size of a large asteroid, only capable of surviving in microgravity conditions, and processes data at 0.5% the speed of a human brain.
  • Charles Babbage and Ada Lovelace appear in an episode of Doctor Who, "Spyfall Part 2", where the engine is displayed and referenced.

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