title: Market segmentation

text: Note that these descriptors are merely commonly used examples. Marketers customize the variable and descriptors for both local conditions and for specific applications. For example, in the health industry, planners often segment broad markets according to 'health consciousness' and identify low, moderate, and highly health-conscious segments. This is an applied example of behavioural segmentation, using attitude to product or service as a key descriptor or variable which has been customized for the specific application.


title: Market segmentation

text: Purchase or usage occasion segmentation focuses on analyzing occasions when consumers might purchase or consume a product. This approach customer-level and occasion-level segmentation models and provides an understanding of the individual customers’ needs, behaviour, and value under different occasions of usage and time. Unlike traditional segmentation models, this approach assigns more than one segment to each unique customer, depending on the current circumstances they are under.


title: Market segmentation

text: Benefit segmentation (sometimes called "needs-based segmentation") was developed by Grey Advertising in the late 1960s. The benefits-sought by purchasers enables the market to be divided into segments with distinct needs, perceived value, benefits sought, or advantage that accrues from the purchase of a product or service. Marketers using benefit segmentation might develop products with different quality levels, performance, customer service, special features, or any other meaningful benefit and pitch different products at each of the segments identified. Benefit segmentation is one of the more commonly used approaches to segmentation and is widely used in many consumer markets including motor vehicles, fashion and clothing, furniture, consumer electronics, and holiday-makers.


title: Market segmentation

text: Loker and Purdue, for example, used benefit segmentation to segment the pleasure holiday travel market. The segments identified in this study were the naturalists, pure excitement seekers, escapists.


title: Market segmentation

text: Attitudinal segmentation provides insight into the mindset of customers, especially the attitudes and beliefs that drive consumer decision-making and behaviour. An example of attitudinal segmentation comes from the UK's Department of Environment which segmented the British population into six segments, based on attitudes that drive behaviour relating to environmental protection:


title: Market segmentation

text: One of the difficulties organisations face when implementing segmentation into their business processes is that segmentations developed using a single variable base, e.g. attitudes, are useful only for specific business functions. As an example, segmentations driven by functional needs (e.g. “I want home appliances that are very quiet”) can provide clear direction for product development, but tell little how to position brands, or who to target on the customer database and with what tonality of messaging.


title: Market segmentation

text: Hybrid segmentation is a family of approaches that specifically addresses this issue by combining two or more variable bases into a single segmentation. This emergence has been driven by three factors. First, the development of more powerful AI and machine learning algorithms to help attribute segmentations to customer databases; second, the rapid increase in the breadth and depth of data that is available to commercial organisations; third, the increasing prevalence of customer databases amongst companies (which generates the commercial demand for segmentation to be used for different purposes).


title: Market segmentation

text: A successful example of hybrid segmentation came from the travel company TUI, which in 2018 developed a hybrid segmentation using a combination of geo-demographics, high-level category attitudes, and more specific holiday-related needs. Before the onset of Covid-19 travel restrictions, they credited this segmentation with having generated an incremental £50 million of revenue in the UK market alone in just over two years.


title: Market segmentation

text: Facebook has recently developed what marketing professor Mark Ritson describes as a “very impressive” hybrid segmentation using a combination of behavioural, attitudinal, and demographic data.


title: Market segmentation

text: With a clear break from the traditional paradigm of focusing on a single variable base, many marketers view hybrid segmentation as marking the beginning of a new era in segmentation.


title: Market segmentation

text: In addition to geographics, demographics, psychographics, and behavioural bases, marketers occasionally turn to other means of segmenting the market or developing segment profiles.


title: Market segmentation

text: A generation is defined as "a cohort of people born within a similar span of time (15 years at the upper end) who share a comparable age and life stage and who were shaped by a particular span of time (events, trends, and developments)." Generational segmentation refers to the process of dividing and analyzing a population into cohorts based on their birth date. Generational segmentation assumes that people's values and attitudes are shaped by the key events that occurred during their lives and that these attitudes translate into product and brand preferences.


title: Market segmentation

text: Demographers, studying population change, disagree about precise dates for each generation. Dating is normally achieved by identifying population peaks or troughs, which can occur at different times in each country. For example, in Australia the post-war population boom peaked in 1960, while the peak occurred somewhat later in the US and Europe, with most estimates converging on 1964. Accordingly, Australian Boomers are normally defined as those born between 1945–1960; while American and European Boomers are normally defined as those born between 1946–64. Thus, the generational segments and their dates discussed here must be taken as approximations only.


title: Market segmentation

text: Cultural segmentation is used to classify markets according to their cultural origin. Culture is a major dimension of consumer behaviour and can be used to enhance customer insight and as a component of predictive models. Cultural segmentation enables appropriate communications to be crafted for particular cultural communities. Cultural segmentation can be applied to existing customer data to measure market penetration in key cultural segments by product, brand, channel as well as traditional measures of recency, frequency, and monetary value. These benchmarks form an important evidence-base to guide strategic direction and tactical campaign activity, allowing engagement trends to be monitored over time.


title: Market segmentation

text: Cultural segmentation can be combined with other bases, especially geographics so that segments are mapped according to state, region, suburb, and neighborhood. This provides a geographical market view of population proportions and may be of benefit in selecting appropriately located premises, determining territory boundaries, and local marketing activities.


title: Market segmentation

text: Census data is a valuable source of cultural data but cannot meaningfully be applied to individuals. Name analysis (onomastics) is the most reliable and efficient means of describing the cultural origin of individuals. The accuracy of using name analysis as a surrogate for cultural background in Australia is 80–85%, after allowing for female name changes due to marriage, social or political reasons, or colonial influence. The extent of name data coverage means a user will code a minimum of 99 percent of individuals with their most likely ancestral origin.


title: Market segmentation

text: Online market segmentation is similar to the traditional approaches in that the segments should be identifiable, substantial, accessible, stable, differentiable, and actionable. Customer data stored in online data management systems such as a CRM or DMP enables the analysis and segmentation of consumers across a diverse set of attributes. Forsyth et al., in an article 'Internet research' grouped current active online consumers into six groups: Simplifiers, Surfers, Bargainers, Connectors, Routiners, and Sportsters. The segments differ regarding four customers' behaviours, namely:


title: Market segmentation

text: For example, "Simplifiers" make over 50 percent of all online transactions. Their main characteristic is that they need easy (one-click) access to information and products as well as easy and quickly available service regarding products. Amazon is an example of a company that created an online environment for Simplifiers. They also 'dislike unsolicited e-mail, uninviting chat rooms, pop-up windows intended to encourage impulse buys, and other features that complicate their on- and off-line experience'. Surfers like to spend a lot of time online, thus companies must have a variety of products to offer and constant updates, "Bargainers" are looking for the best price, Connectors like to relate to others, "Routiners" want content, and "Sportsters" like sport and entertainment sites.


title: Market segmentation

text: Another major decision in developing the segmentation strategy is the selection of market segments that will become the focus of special attention (known as "target markets"). The marketer faces a number of important decisions:


title: Market segmentation

text: When a marketer enters more than one market, the segments are often labeled the "primary target market", "secondary target market." The primary market is the target market selected as the main focus of marketing activities. The secondary target market is likely to be a segment that is not as large as the primary market, but has growth potential. Alternatively, the secondary target group might consist of a small number of purchasers that account for a relatively high proportion of sales volume perhaps due to purchase value or purchase frequency.


title: Market segmentation

text: There are no formulas for evaluating the attractiveness of market segments and a good deal of judgment must be exercised. Nevertheless, a number of considerations can be used to assist in evaluating market segments for overall attractiveness. The following lists a series of questions that can be asked.


title: Market segmentation

text: When the segments have been determined and separate offers developed for each of the core segments, the marketer's next task is to design a marketing program (also known as the marketing mix) that will resonate with the target market or markets. Developing the marketing program requires a deep knowledge of key market segments' purchasing habits, their preferred retail outlet, their media habits, and their price sensitivity. The marketing program for each brand or product should be based on the understanding of the target market (or target markets) revealed in the market profile.


title: Market segmentation

text: Positioning is the final step in the S-T-P planning approach; Segmentation → Targeting → Positioning; a core framework for developing marketing plans and setting objectives. Positioning refers to decisions about how to present the offer in a way that resonates with the target market. During the research and analysis that forms the central part of segmentation and targeting, the marketer will have gained insights into what motivates consumers to purchase a product or brand. These insights will form part of the positioning strategy.


title: Market segmentation

text: According to advertising guru, David Ogilvy, "Positioning is the act of designing the company’s offering and image to occupy a distinctive place in the minds of the target market. The goal is to locate the brand in the minds of consumers to maximize the potential benefit to the firm. A good brand positioning helps guide marketing strategy by clarifying the brand’s essence, what goals it helps the consumer achieve, and how it does so in a unique way."


title: Market segmentation

text: The technique known as perceptual mapping is often used to understand consumers' mental representations of brands within a given category. Traditionally two variables (often, but not necessarily, price and quality) are used to construct the map. A sample of people in the target market are asked to explain where they would place various brands in terms of the selected variables. Results are averaged across all respondents, and results are plotted on a graph, as illustrated in the figure. The final map indicates how the "average" member of the population views the brand that makes up a category and how each of the brands relates to other brands within the same category. While perceptual maps with two dimensions are common, multi-dimensional maps are also used.


title: Market segmentation

text: Segmenting business markets is more straightforward than segmenting consumer markets. Businesses may be segmented according to industry, business size, business location, turnover, number of employees, company technology, purchasing approach, or any other relevant variables. The most widely used segmentation bases used in business to business markets are geographics and firmographics.


title: Market segmentation

text: The basic approach to retention-based segmentation is that a company tags each of its active customers on four axes:


title: Market segmentation

text: This analysis of customer lifecycles is usually included in the growth plan of a business to determine which tactics to implement to retain or let go of customers. Tactics commonly used range from providing special customer discounts to sending customers communications that reinforce the value proposition of the given service.


title: Market segmentation

text: The choice of an appropriate statistical method for the segmentation depends on a number of factors including, the broad approach (a-priori or post-hoc), the availability of data, time constraints, the marketer's skill level, and resources.


title: Market segmentation

text: A priori research occurs when "a theoretical framework is developed before the research is conducted". In other words, the marketer has an idea about whether to segment the market geographically, demographically, psychographically or behaviourally before undertaking any research. For example, a marketer might want to learn more about the motivations and demographics of light and moderate users in an effort to understand what tactics could be used to increase usage rates. In this case, the target variable is known – the marketer has already segmented using a behavioural variable – user status. The next step would be to collect and analyze attitudinal data for light and moderate users. The typical analysis includes simple cross-tabulations, frequency distributions and occasionally logistic regression or one of a number of proprietary methods.


title: Market segmentation

text: The main disadvantage of a-priori segmentation is that it does not explore other opportunities to identify market segments that could be more meaningful.


title: Market segmentation

text: In contrast, post-hoc segmentation makes no assumptions about the optimal theoretical framework. Instead, the analyst's role is to determine the segments that are the most meaningful for a given marketing problem or situation. In this approach, the empirical data drives the segmentation selection. Analysts typically employ some type of clustering analysis or structural equation modeling to identify segments within the data. Post-hoc segmentation relies on access to rich datasets, usually with a very large number of cases, and uses sophisticated algorithms to identify segments.


title: Market segmentation

text: The figure alongside illustrates how segments might be formed using clustering; however, note that this diagram only uses two variables, while in practice clustering employs a large number of variables.


title: Market segmentation

text: Marketers often engage commercial research firms or consultancies to carry out segmentation analysis, especially if they lack the statistical skills to undertake the analysis. Some segmentation, especially post-hoc analysis, relies on sophisticated statistical analysis.


title: Market segmentation

text: Marketers use a variety of data sources for segmentation studies and market profiling. Typical sources of information include:


title: 52-hertz whale

text: The 52-hertz whale, colloquially referred to as 52 Blue, is an individual whale of unidentified species that calls at the unusual frequency of 52 hertz. This pitch is at a higher frequency than that of the other whale species with migration patterns most closely resembling the 52-hertz whale'sthe blue whale (10 to 39 Hz) and the fin whale (20 Hz). Its call has been detected regularly in many locations since the late 1980s, and appears to be the only individual emitting a whale call at this frequency. However, the whale itself has never been sighted; it has only been heard via hydrophones. It has been described as the "world's loneliest whale", though potential recordings of a second 52-hertz whale, heard elsewhere at the same time, have been sporadically found since 2010.


title: 52-hertz whale

text: The sonic signature is that of a whale, albeit at a unique frequency. At 52 hertz, it is a little higher than the lowest note on a double bass. The call patterns resemble neither blue nor fin whales, being much higher in frequency, shorter, and more frequent. Blue whales usually vocalize at 10–39 Hz, fin whales at 20 Hz. The 52-hertz calls of this whale are highly variable in their pattern of repetition, duration, and sequence, although they are easily identifiable due to their frequency and characteristic clustering. The calls have deepened slightly to around 50 hertz since 1992, suggesting the whale has grown or matured.


title: 52-hertz whale

text: The migration track of the 52-hertz whale is unrelated to the presence or movement of other whale species. Its movements have been somewhat similar to that of blue whales, but its timing has been more like that of fin whales. It is detected in the Pacific Ocean every year beginning in August–December, and moves out of range of the hydrophones in January–February. It travels as far north as the Aleutian and Kodiak Islands, and as far south as the California coast, swimming between 30 and 70 km each day. Its recorded distance traveled per season has ranged from a low of 708 km to a high of 11,062 km in 2002–03.


title: 52-hertz whale

text: Scientists at the Woods Hole Oceanographic Institution have been unable to identify the species of the whale. They speculate that it could be malformed or a blue whale hybrid. The research team is often contacted by deaf people who wonder whether the whale may also be deaf.


title: 52-hertz whale

text: Whatever biological cause underlies its unusually high frequency voice does not seem to be detrimental to its survival. The fact that the whale has survived and apparently matured indicates it is probably healthy. Still, its call is the only one of its kind detected anywhere and there is only one such source per season. Because of this, the animal has been called the loneliest whale in the world.


title: 52-hertz whale

text: The 52-hertz whale was discovered by a team from the Woods Hole Oceanographic Institution. Its call was first detected in 1989, then again in 1990 and 1991. In 1992, following the end of the Cold War, the U.S. Navy partially declassified the recordings and technical specifications of its SOSUS anti-submarine hydrophone arrays, and made SOSUS available for oceanographic research. , the whale had been detected every year since.


title: 52-hertz whale

text: "The Loneliest", a short mockumentary film about two women searching for the loneliest whale, was made in April 2014 by Lilian Mehrel, with the Alfred P. Sloan Foundation.


title: 52-hertz whale

text: The title of the Taiwanese movie "52Hz, I Love You" (2017) is inspired by the whale, using it as a metaphor for the loneliness experienced when looking for love.


title: 52-hertz whale

text: Stare Yıldırım's 2018 film "My Name is Batlir, Not Butler" features the 52-hertz whale as both a character (mostly represented by a photo and voice-over) and as a metaphor for the loneliness of those who are different.


title: 52-hertz whale

text: The animated short film entitled "The Phantom 52" premiered at the Sundance Film Festival in January 2019. The film is written and directed by Geoff Marslett, and stars Tom Skerritt as the loneliest whale. "The Phantom 52" went on to play at over 60 film festivals worldwide and win a half dozen awards.


title: 52-hertz whale

text: A feature-length documentary entitled "", directed by Joshua Zeman, the director of "Cropsey", and executive producers Leonardo DiCaprio and Adrian Grenier, was commercially released by Bleecker Street on July 9, 2021. The film follows Zeman and a group of five scientists and oceanographers on a quest to find the whale off the coast of California. Funded through a Kickstarter campaign, the film received generally positive reviews among critics, holding an approval rating of 86% based on 35 reviews on Rotten Tomatoes. "Time"'s Stephanie Zacharek called the film "both invigorating and calming to watch," while Katie Walsh wrote in the "Los Angeles Times" that the film is "a modern-day Moby Dick with a conservationist bent" that "surprises, delights and will keep you on the edge of your seat." Sheri Linden of "The Hollywood Reporter" wrote that "the film's epilogue caps the action with a rapturous surprise", referring to the sightingcomplete with film footageof a blue whale-fin whale hybrid, believed to be the source of the 52 Hz calls.


title: 52-hertz whale

text: Ambient artist Andy Othling, under the name of Lowercase Noises, released an EP called "Migratory Patterns" in 2011. The album "is a collection of songs written as a chronicle of the story of the famed 52Hz whale."


title: 52-hertz whale

text: Montreal-based saxophone player and composer Colin Stetson's 2013 album "" included a song entitled "Part of Me Apart From You". Though not explicitly written about the 52-hertz whale, when first performing the song live, he has remarked on at least several occasions that the story of the "loneliest whale" resonated deeply with his composition. "This whale is alone in a large body of water, swimming, singing its song, calling for a likeness it will never find," he said by way of introducing the song at a performance at Toronto's Great Hall on 19 May 2013. "When I play this song, I can't help but think about this whale, who right at this very minute is singing alone."


title: 52-hertz whale

text: South Korean group BTS's 2015 album "The Most Beautiful Moment in Life, Pt. 2" includes the track "Whalien 52", which explicitly uses the 52-hertz whale as a metaphor for the alienation from others often felt by adolescents.


title: 52-hertz whale

text: The English folk duo Kathryn Roberts and Sean Lakeman included the song "52 Hertz" on their 2015 album "Tomorrow Will Follow Today". The song is about the whale and includes the line, "52 Hertz, 52 Hertz, I'm singing a love song that no-one can hear" in the chorus.


title: 52-hertz whale

text: In 2016, No Land (a music group made up of Azerbaijani, Iranian, Kurdish and Turkish musicians) released 52 Hertz Whale - Outro.


title: 52-hertz whale

text: In 2017, Zhou Shen released a song called "A Lonely Blue Whale Living Like an Island" or "化身孤岛的鲸", inspired by the whale.


title: 52-hertz whale

text: In 2020, a Vtuber known as Bao released a song called "52-Hearts," which is a play on words for the 52-hertz whale.


title: 52-hertz whale

text: In 2021, instrumental post rock band Gilmore Trail released a song called "Echoes of Solitude", using their instruments to create their own interpretation of the sounds of the lonely whale.


title: 52-hertz whale

text: In 2007, Agnieszka Jurek (ed.) and 30 international artists, musicians, filmmakers and journalists published a book titled "52 Hertz Whale - he sounded different than he should".


title: 52-hertz whale

text: In 2019, Lynne Kelly published a book titled "Song for a Whale", about a deaf girl who tries to find the whale.


title: 52-hertz whale

text: In 2020, Japanese novelist Sonoko Machida published a novel titled "52-Hertz Whales", in which the anomalous whale serves as a metaphor for "voiceless" lonely people who find each other by chance.


title: 52-hertz whale

text: In 2020, an illustrated children's book was published by Umbrelly Books Publishing, called "52, A Tale of Loneliness."


title: 52-hertz whale

text: The book was written by Johnny DePalma, Illustrated by Kyle Brown and has an available companion audiobook, as read by Patton Oswalt.


title: Solar irradiance

text: Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.


title: Solar irradiance

text: Solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment (joule per square metre, J/m) during that time period. This integrated solar irradiance is called solar irradiation, solar exposure, solar insolation, or insolation.


title: Solar irradiance

text: Irradiance may be measured in space or at the Earth's surface after atmospheric absorption and scattering. Irradiance in space is a function of distance from the Sun, the solar cycle, and cross-cycle changes.


title: Solar irradiance

text: Irradiance on the Earth's surface additionally depends on the tilt of the measuring surface, the height of the Sun above the horizon, and atmospheric conditions.


title: Solar irradiance

text: The study and measurement of solar irradiance have several important applications, including the prediction of energy generation from solar power plants, the heating and cooling loads of buildings, climate modeling and weather forecasting, passive daytime radiative cooling applications, and space travel.


title: Solar irradiance

text: The SI unit of irradiance is watts per square metre (W/m = Wm). The unit of insolation often used in the solar power industry is kilowatt hours per square metre (kWh/m).


title: Solar irradiance

text: The Langley is an alternative unit of insolation. One Langley is one thermochemical calorie per square centimetre or 41,840J/m.


title: Solar irradiance

text: The average annual solar radiation arriving at the top of the Earth's atmosphere is about 1361W/m. This represents the power per unit area of solar irradiance across the spherical surface surrounding the Sun with a radius equal to the distance to the Earth (1AU). This means that the approximately circular disc of the Earth, as viewed from the Sun, receives a roughly stable 1361W/m at all times. The area of this circular disc is , in which is the radius of the Earth. Because the Earth is approximately spherical, it has total area formula_2, meaning that the solar radiation arriving at the top of the atmosphere, averaged over the entire surface of the Earth, is simply divided by four to get 340W/m. In other words, averaged over the year and the day, the Earth's atmosphere receives 340W/m from the Sun. This figure is important in radiative forcing.


title: Solar irradiance

text: The distribution of solar radiation at the top of the atmosphere is determined by Earth's sphericity and orbital parameters.


title: Solar irradiance

text: Insolation is essential for numerical weather prediction and understanding seasons and climatic change. Application to ice ages is known as Milankovitch cycles.


title: Solar irradiance

text: Distribution is based on a fundamental identity from spherical trigonometry, the spherical law of cosines:


title: Solar irradiance

text: where "a", "b" and "c" are arc lengths, in radians, of the sides of a spherical triangle. "C" is the angle in the vertex opposite the side which has arc length "c". Applied to the calculation of solar zenith angle Θ, the following applies to the spherical law of cosines:


title: Solar irradiance

text: The separation of Earth from the sun can be denoted R and the mean distance can be denoted R, approximately 1 astronomical unit (AU). The solar constant is denoted S. The solar flux density (insolation) onto a plane tangent to the sphere of the Earth, but above the bulk of the atmosphere (elevation 100 km or greater) is:


title: Solar irradiance

text: The average of "Q" over a day is the average of "Q" over one rotation, or the hour angle progressing from "h" = π to "h" = −π:


title: Solar irradiance

text: Let "h" be the hour angle when Q becomes positive. This could occur at sunrise when formula_12, or for "h" as a solution of


title: Solar irradiance

text: If tan(φ)tan(δ) > 1, then the sun does not set and the sun is already risen at "h" = π, so h = π. If tan(φ)tan(δ) < −1, the sun does not rise and formula_15.


title: Solar irradiance

text: Let θ be the conventional polar angle describing a planetary orbit. Let "θ" = 0 at the vernal equinox. The declination δ as a function of orbital position is


title: Solar irradiance

text: where ε is the obliquity. (Note: The correct formula, valid for any axial tilt, is formula_20.) The conventional longitude of perihelion ϖ is defined relative to the vernal equinox, so for the elliptical orbit:


title: Solar irradiance

text: With knowledge of ϖ, ε and "e" from astrodynamical calculations and S from a consensus of observations or theory, formula_23can be calculated for any latitude φ and θ. Because of the elliptical orbit, and as a consequence of Kepler's second law, "θ" does not progress uniformly with time. Nevertheless, "θ" = 0° is exactly the time of the vernal equinox, "θ" = 90° is exactly the time of the summer solstice, "θ" = 180° is exactly the time of the autumnal equinox and "θ" = 270° is exactly the time of the winter solstice.


title: Solar irradiance

text: Total solar irradiance (TSI) changes slowly on decadal and longer timescales. The variation during solar cycle 21 was about 0.1% (peak-to-peak). In contrast to older reconstructions, most recent TSI reconstructions point to an increase of only about 0.05% to 0.1% between the 17th century Maunder Minimum and the present.


title: Solar irradiance

text: Ultraviolet irradiance (EUV) varies by approximately 1.5 percent from solar maxima to minima, for 200 to 300 nm wavelengths. However, a proxy study estimated that UV has increased by 3.0% since the Maunder Minimum.


title: Solar irradiance

text: Some variations in insolation are not due to solar changes but rather due to the Earth moving between its perihelion and aphelion, or changes in the latitudinal distribution of radiation. These orbital changes or Milankovitch cycles have caused radiance variations of as much as 25% (locally; global average changes are much smaller) over long periods. The most recent significant event was an axial tilt of 24° during boreal summer near the "Holocene climatic optimum".


title: Solar irradiance

text: Obtaining a time series for a formula_25 for a particular time of year, and particular latitude, is a useful application in the theory of Milankovitch cycles. For example, at the summer solstice, the declination δ is equal to the obliquity ε. The distance from the sun is


title: Solar irradiance

text: For this summer solstice calculation, the role of the elliptical orbit is entirely contained within the important product formula_27, the precession index, whose variation dominates the variations in insolation at 65°N when eccentricity is large. For the next 100,000 years, with variations in eccentricity being relatively small, variations in obliquity dominate.


title: Solar irradiance

text: The space-based TSI record comprises measurements from more than ten radiometers and spans three solar cycles.


title: Solar irradiance

text: All modern TSI satellite instruments employ active cavity electrical substitution radiometry. This technique measures the electrical heating needed to maintain an absorptive blackened cavity in thermal equilibrium with the incident sunlight which passes through a precision aperture of calibrated area. The aperture is modulated via a shutter. Accuracy uncertainties of <0.01% are required to detect long term solar irradiance variations, because expected changes are in the range 0.05–0.15W/m per century.


title: Solar irradiance

text: In orbit, radiometric calibrations drift for reasons including solar degradation of the cavity, electronic degradation of the heater, surface degradation of the precision aperture and varying surface emissions and temperatures that alter thermal backgrounds. These calibrations require compensation to preserve consistent measurements.


title: Solar irradiance

text: For various reasons, the sources do not always agree. The Solar Radiation and Climate Experiment/Total Irradiance Measurement (SORCE/TIM) TSI values are lower than prior measurements by the Earth Radiometer Budget Experiment (ERBE) on the Earth Radiation Budget Satellite (ERBS), VIRGO on the Solar Heliospheric Observatory (SoHO) and the ACRIM instruments on the Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS) and ACRIMSAT. Pre-launch ground calibrations relied on component rather than system-level measurements since irradiance standards at the time lacked sufficient absolute accuracies.


title: Solar irradiance

text: Measurement stability involves exposing different radiometer cavities to different accumulations of solar radiation to quantify exposure-dependent degradation effects. These effects are then compensated for in the final data. Observation overlaps permits corrections for both absolute offsets and validation of instrumental drifts.


title: Solar irradiance

text: Uncertainties of individual observations exceed irradiance variability (∼0.1%). Thus, instrument stability and measurement continuity are relied upon to compute real variations.


title: Solar irradiance

text: Long-term radiometer drifts can potentially be mistaken for irradiance variations which can be misinterpreted as affecting climate. Examples include the issue of the irradiance increase between cycle minima in 1986 and 1996, evident only in the ACRIM composite (and not the model) and the low irradiance levels in the PMOD composite during the 2008 minimum.


title: Solar irradiance

text: Despite the fact that ACRIM I, ACRIM II, ACRIM III, VIRGO and TIM all track degradation with redundant cavities, notable and unexplained differences remain in irradiance and the modeled influences of sunspots and faculae.


title: Solar irradiance

text: Disagreement among overlapping observations indicates unresolved drifts that suggest the TSI record is not sufficiently stable to discern solar changes on decadal time scales. Only the ACRIM composite shows irradiance increasing by ∼1W/m between 1986 and 1996; this change is also absent in the model.


title: Solar irradiance

text: Recommendations to resolve the instrument discrepancies include validating optical measurement accuracy by comparing ground-based instruments to laboratory references, such as those at National Institute of Science and Technology (NIST); NIST validation of aperture area calibrations uses spares from each instrument; and applying diffraction corrections from the view-limiting aperture.


title: Solar irradiance

text: For ACRIM, NIST determined that diffraction from the view-limiting aperture contributes a 0.13% signal not accounted for in the three ACRIM instruments. This correction lowers the reported ACRIM values, bringing ACRIM closer to TIM. In ACRIM and all other instruments but TIM, the aperture is deep inside the instrument, with a larger view-limiting aperture at the front. Depending on edge imperfections this can directly scatter light into the cavity. This design admits into the front part of the instrument two to three times the amount of light intended to be measured; if not completely absorbed or scattered, this additional light produces erroneously high signals. In contrast, TIM's design places the precision aperture at the front so that only desired light enters.


title: Solar irradiance

text: Variations from other sources likely include an annual systematics in the ACRIM III data that is nearly in phase with the Sun-Earth distance and 90-day spikes in the VIRGO data coincident with SoHO spacecraft maneuvers that were most apparent during the 2008 solar minimum.


title: Solar irradiance

text: TIM's high absolute accuracy creates new opportunities for measuring climate variables. TSI Radiometer Facility (TRF) is a cryogenic radiometer that operates in a vacuum with controlled light sources. L-1 Standards and Technology (LASP) designed and built the system, completed in 2008. It was calibrated for optical power against the NIST Primary Optical Watt Radiometer, a cryogenic radiometer that maintains the NIST radiant power scale to an uncertainty of 0.02% (1"σ"). As of 2011 TRF was the only facility that approached the desired <0.01% uncertainty for pre-launch validation of solar radiometers measuring irradiance (rather than merely optical power) at solar power levels and under vacuum conditions.


title: Solar irradiance

text: TRF encloses both the reference radiometer and the instrument under test in a common vacuum system that contains a stationary, spatially uniform illuminating beam. A precision aperture with an area calibrated to 0.0031% (1"σ") determines the beam's measured portion. The test instrument's precision aperture is positioned in the same location, without optically altering the beam, for direct comparison to the reference. Variable beam power provides linearity diagnostics, and variable beam diameter diagnoses scattering from different instrument components.


title: Solar irradiance

text: The Glory/TIM and PICARD/PREMOS flight instrument absolute scales are now traceable to the TRF in both optical power and irradiance. The resulting high accuracy reduces the consequences of any future gap in the solar irradiance record.


title: Solar irradiance

text: The most probable value of TSI representative of solar minimum is , lower than the earlier accepted value of , established in the 1990s. The new value came from SORCE/TIM and radiometric laboratory tests. Scattered light is a primary cause of the higher irradiance values measured by earlier satellites in which the precision aperture is located behind a larger, view-limiting aperture. The TIM uses a view-limiting aperture that is smaller than the precision aperture that precludes this spurious signal. The new estimate is from better measurement rather than a change in solar output.


title: Solar irradiance

text: A regression model-based split of the relative proportion of sunspot and facular influences from SORCE/TIM data accounts for 92% of observed variance and tracks the observed trends to within TIM's stability band. This agreement provides further evidence that TSI variations are primarily due to solar surface magnetic activity.


title: Solar irradiance

text: Instrument inaccuracies add a significant uncertainty in determining Earth's energy balance. The energy imbalance has been variously measured (during a deep solar minimum of 2005–2010) to be , and . Estimates from space-based measurements range +3–7W/m. SORCE/TIM's lower TSI value reduces this discrepancy by 1W/m. This difference between the new lower TIM value and earlier TSI measurements corresponds to a climate forcing of −0.8W/m, which is comparable to the energy imbalance.


title: Solar irradiance

text: In 2014 a new ACRIM composite was developed using the updated ACRIM3 record. It added corrections for scattering and diffraction revealed during recent testing at TRF and two algorithm updates. The algorithm updates more accurately account for instrument thermal behavior and parsing of shutter cycle data. These corrected a component of the quasi-annual spurious signal and increased the signal-to-noise ratio, respectively. The net effect of these corrections decreased the average ACRIM3 TSI value without affecting the trending in the ACRIM Composite TSI.


title: Solar irradiance

text: Differences between ACRIM and PMOD TSI composites are evident, but the most significant is the solar minimum-to-minimum trends during solar cycles 21-23. ACRIM found an increase of +0.037%/decade from 1980 to 2000 and a decrease thereafter. PMOD instead presents a steady decrease since 1978. Significant differences can also be seen during the peak of solar cycles 21 and 22. These arise from the fact that ACRIM uses the original TSI results published by the satellite experiment teams while PMOD significantly modifies some results to conform them to specific TSI proxy models. The implications of increasing TSI during the global warming of the last two decades of the 20th century are that solar forcing may be a marginally larger factor in climate change than represented in the CMIP5 general circulation climate models.


title: Solar irradiance

text: Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361W/m. The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000W/m at sea level on a clear day. When 1361 W/m is arriving above the atmosphere (when the sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m, and global radiation on a horizontal surface at ground level is about 1120 W/m.


title: Solar irradiance

text: The latter figure includes radiation scattered or reemitted by the atmosphere and surroundings. The actual figure varies with the Sun's angle and atmospheric circumstances. Ignoring clouds, the daily average insolation for the Earth is approximately .


title: Solar irradiance

text: The output of, for example, a photovoltaic panel, partly depends on the angle of the sun relative to the panel. One Sun is a unit of power flux, not a standard value for actual insolation. Sometimes this unit is referred to as a Sol, not to be confused with a "sol", meaning one solar day.


title: Solar irradiance

text: Part of the radiation reaching an object is absorbed and the remainder reflected. Usually, the absorbed radiation is converted to thermal energy, increasing the object's temperature. Manmade or natural systems, however, can convert part of the absorbed radiation into another form such as electricity or chemical bonds, as in the case of photovoltaic cells or plants. The proportion of reflected radiation is the object's reflectivity or albedo.


title: Solar irradiance

text: Insolation onto a surface is largest when the surface directly faces (is normal to) the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angle's cosine; see effect of Sun angle on climate.


title: Solar irradiance

text: In the figure, the angle shown is between the ground and the sunbeam rather than between the vertical direction and the sunbeam; hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal. The sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area. Consequently, half as much light falls on each square mile.


title: Solar irradiance

text: This projection effect is the main reason why Earth's polar regions are much colder than equatorial regions. On an annual average, the poles receive less insolation than does the equator, because the poles are always angled more away from the Sun than the tropics, and moreover receive no insolation at all for the six months of their respective winters.


title: Solar irradiance

text: At a lower angle, the light must also travel through more atmosphere. This attenuates it (by absorption and scattering) further reducing insolation at the surface.


title: Solar irradiance

text: Attenuation is governed by the Beer-Lambert Law, namely that the transmittance or fraction of insolation reaching the surface decreases exponentially in the optical depth or absorbance (the two notions differing only by a constant factor of ) of the path of insolation through the atmosphere. For any given short length of the path, the optical depth is proportional to the number of absorbers and scatterers along that length, typically increasing with decreasing altitude. The optical depth of the whole path is then the integral (sum) of those optical depths along the path.


title: Solar irradiance

text: When the density of absorbers is layered, that is, depends much more on vertical than horizontal position in the atmosphere, to a good approximation the optical depth is inversely proportional to the projection effect, that is, to the cosine of the zenith angle. Since transmittance decreases exponentially with increasing optical depth, as the sun approaches the horizon there comes a point when absorption dominates projection for the rest of the day. With a relatively high level of absorbers this can be a considerable portion of the late afternoon, and likewise of the early morning. Conversely, in the (hypothetical) total absence of absorption, the optical depth remains zero at all altitudes of the sun, that is, transmittance remains 1, and so only the projection effect applies.


title: Solar irradiance

text: Assessment and mapping of solar potential at the global, regional and country levels have been the subject of significant academic and commercial interest. One of the earliest attempts to carry out comprehensive mapping of solar potential for individual countries was the Solar & Wind Resource Assessment (SWERA) project, funded by the United Nations Environment Program and carried out by the US National Renewable Energy Laboratory. Other examples include global mapping by the National Aeronautics and Space Administration and other similar institutes, many of which are available on the Global Atlas for Renewable Energy provided by the International Renewable Energy Agency. A number of commercial firms now exist to provide solar resource data to solar power developers, including 3E, Clean Power Research, SoDa Solar Radiation Data, Solargis, Vaisala (previously 3Tier), and Vortex, and these firms have often provided solar potential maps for free. In January 2017 the Global Solar Atlas was launched by the World Bank, using data provided by Solargis, to provide a single source for high-quality solar data, maps, and GIS layers covering all countries.


title: Solar irradiance

text: Solar radiation maps are built using databases derived from satellite imagery, as for example using visible images from Meteosat Prime satellite. A method is applied to the images to determine solar radiation. One well validated satellite-to-irradiance model is the SUNY model. The accuracy of this model is well evaluated. In general, solar irradiance maps are accurate, especially for Global Horizontal Irradiance.


title: Solar irradiance

text: In many countries, the figures can be obtained from an insolation map or from insolation tables that reflect data over the prior 30–50 years.


title: Solar irradiance

text: Different solar power technologies are able to use different components of the total irradiation. While solar photovoltaics panels are able to convert to electricity both direct irradiation and diffuse irradiation, concentrated solar power is only able to operate efficiently with direct irradiation, thus making these systems suitable only in locations with relatively low cloud cover.


title: Solar irradiance

text: Because solar collectors panels are almost always mounted at an angle towards the sun, insolation must be adjusted to prevent estimates that are inaccurately low for winter and inaccurately high for summer.


title: Solar irradiance

text: This also means that the amount of sun falling on a solar panel at high latitude is not as low compared to one at the equator as would appear from just considering insolation on a horizontal surface.


title: Solar irradiance

text: Photovoltaic panels are rated under standard conditions to determine the Wp (watt peak) rating, which can then be used with insolation to determine the expected output, adjusted by factors such as tilt, tracking and shading (which can be included to create the installed Wp rating).


title: Solar irradiance

text: In construction, insolation is an important consideration when designing a building for a particular site.


title: Solar irradiance

text: The projection effect can be used to design buildings that are cool in summer and warm in winter, by providing vertical windows on the equator-facing side of the building (the south face in the northern hemisphere, or the north face in the southern hemisphere): this maximizes insolation in the winter months when the Sun is low in the sky and minimizes it in the summer when the Sun is high. (The Sun's north/south path through the sky spans 47° through the year).


title: Solar irradiance

text: In civil engineering and hydrology, numerical models of snowmelt runoff use observations of insolation.


title: Solar irradiance

text: Irradiance plays a part in climate modeling and weather forecasting. A non-zero average global net radiation at the top of the atmosphere is indicative of Earth's thermal disequilibrium as imposed by climate forcing.


title: Solar irradiance

text: The impact of the lower 2014 TSI value on climate models is unknown. A few tenths of a percent change in the absolute TSI level is typically considered to be of minimal consequence for climate simulations. The new measurements require climate model parameter adjustments.


title: Solar irradiance

text: Experiments with GISS Model 3 investigated the sensitivity of model performance to the TSI absolute value during the present and pre-industrial epochs, and describe, for example, how the irradiance reduction is partitioned between the atmosphere and surface and the effects on outgoing radiation.


title: Solar irradiance

text: Assessing the impact of long-term irradiance changes on climate requires greater instrument stability combined with reliable global surface temperature observations to quantify climate response processes to radiative forcing on decadal time scales. The observed 0.1% irradiance increase imparts 0.22W/m climate forcing, which suggests a transient climate response of 0.6 °C per W/m. This response is larger by a factor of 2 or more than in the IPCC-assessed 2008 models, possibly appearing in the models' heat uptake by the ocean.


title: Solar irradiance

text: Measuring a surface's capacity to reflect solar irradiance is essential to passive daytime radiative cooling, which has been proposed as a method of reversing local and global temperature increases associated with global warming. In order to measure the cooling power of a passive radiative cooling surface, both the absorbed powers of atmospheric and solar radiations must be quantified. On a clear day, solar irradiance can reach 1000 W/m with a diffuse component between 50-100 W/m. On average the cooling power of a passive daytime radiative cooling surface has been estimated at ~100-150 W/m.


title: Solar irradiance

text: Insolation is the primary variable affecting equilibrium temperature in spacecraft design and planetology.


title: Solar irradiance

text: Solar activity and irradiance measurement is a concern for space travel. For example, the American space agency, NASA, launched its Solar Radiation and Climate Experiment (SORCE) satellite with Solar Irradiance Monitors.


title: A Feast for Crows

text: A Feast for Crows is the fourth of seven planned novels in the epic fantasy series "A Song of Ice and Fire" by American author George R. R. Martin. The novel was first published on October 17, 2005, in the United Kingdom, with a United States edition following on November 8, 2005.


title: A Feast for Crows

text: Because of its size, Martin and his publishers split the narrative of the still-unfinished manuscript for "A Feast for Crows" into two books. Rather than divide the text chronologically in half, Martin instead split the material by plot location, resulting in "two novels taking place simultaneously" with different casts of characters. "A Feast for Crows" was published months later, and focuses mainly on southern Westeros. The concurrent novel "A Dance with Dragons", which focuses on other locations such as the North, the Wall and Essos, was advertised for the following year, but was eventually released six years later in 2011. Martin noted that the "A Song of Ice and Fire" series would now likely total seven novels.


title: A Feast for Crows

text: "A Feast for Crows" was the first novel in the series to debut at number one on "The New York Times" Best Seller list, a feat among fantasy writers only previously achieved by Robert Jordan and Neil Gaiman. In 2006 the novel was nominated for the Hugo Award, the Locus Award, and the British Fantasy Society Award. It has since been adapted, along with "A Dance With Dragons", for television as the fifth season of "Game of Thrones", though elements of the novel appeared in the series' fourth and sixth seasons.


title: A Feast for Crows

text: The War of the Five Kings is slowly coming to its end. The secessionist kings Robb Stark and Balon Greyjoy have been killed. One claimant to the throne, Stannis Baratheon, has gone to fight off invading wildling tribes at the northern Wall, where Robb's half-brother Jon Snow has become the 998th Lord Commander of the Night's Watch, the order responsible for guarding the Wall. The eight-year-old King Tommen Baratheon now rules in King's Landing under the regency of his mother, Cersei Lannister. The warrior woman Brienne of Tarth has been sent by Cersei's brother (and lover) Jaime Lannister on a mission to find Robb's sister Sansa Stark. Sansa is hiding in the Vale, protected by her mother's childhood friend Petyr “Littlefinger” Baelish, who has murdered his wife (and her aunt) Lysa Arryn, and named himself Protector of the Vale and guardian of Lysa's son, the eight-year-old Lord Robert Arryn.


title: A Feast for Crows

text: Pate is a young apprentice at the Citadel in Oldtown, training to become a member of the ancient order of scholar-healers known as maesters. At the request of a stranger, he has stolen an important key to a depository of books and records. After turning over the stolen key and receiving the reward of a gold coin, he bites the coin and dies abruptly from poisoning.


title: A Feast for Crows

text: Following the death of Tywin Lannister, the late Hand of the King, Queen Cersei's regency is marked by rampant cronyism, and her councils are staffed with incompetent officials and unreliable sycophants. She disregards advice from her uncle Kevan and her brother Jaime, alienating them both. Making matters worse is Cersei's increasing distrust of the powerful Tyrells, whose alliance is essential to the stability of the Lannister regime — particularly King Tommen's fiancée Margaery, whom Cersei believes to be the subject of a prophecy about a "younger, more beautiful queen" who will take away all that Cersei holds dear.


title: A Feast for Crows

text: Her reckless management raises the kingdom's debts to the Iron Bank of Braavos and the Faith of the Seven. When Cersei defaults the debt owed to the Iron Bank, the Bank's financial retaliation nearly cripples the economy of Westeros. To settle the crown's debts to the Faith, Cersei permits the restoration of that religion's military order, the Faith Militant, ignoring the danger of a re-armed Faith. A scheme to falsely have the Faith put Margaery on trial for adultery backfires when the religious leadership imprisons Cersei herself on similar (correct) charges.


title: A Feast for Crows

text: Cersei dispatches Jaime to the Riverlands to put down the remnants of the late Robb Stark's rebellion. He negotiates with Robb's great-uncle Brynden “the Blackfish” Tully to surrender the castle of Riverrun in exchange for his nephew Edmure‘s life. Though the siege ends bloodlessly, Brynden escapes. Jaime then receives word that Cersei, who has been arrested by the Faith, wants him to defend her in a trial by combat, but Jaime burns her letter and abandons her to her fate.


title: A Feast for Crows

text: Brienne's quest leads her all over the Riverlands, where she witnesses the devastation caused by the war. She acquires Podrick Payne, the former squire of Jaime's brother Tyrion, and Ser Hyle Hunt, a knight who had once mocked her ugliness, as traveling companions. She learns that Sansa's sister Arya Stark has actually survived and escaped King's Landing, and the feared warrior Sandor Clegane is reportedly dead but someone wearing his helmet has massacred the town of Saltpans. She later kills the culprit Rorge but is gravely injured and mutilated by his companion Biter. Eventually, she is captured by the Brotherhood Without Banners, which was once devoted to protecting the smallfolk of the Riverlands but is now commanded by the magically resurrected Catelyn Stark, Sansa's mother. The undead and vengeful Catelyn, who has taken the name Lady Stoneheart, sentences Brienne to death for consorting with the Lannisters, but offers to spare her and her companions if she agrees to kill Jaime.


title: A Feast for Crows

text: In the remote castle of the Eyrie, Sansa poses as Littlefinger’s illegitimate daughter Alayne Stone, befriending the young Lord Robert Arryn, managing the household, and receiving informal training in politics. During this time, Littlefinger appears to be carefully manipulating Robert's bannermen to secure his status as Lord Protector of the Vale. He eventually reveals that he plans to betroth Sansa to Harrold Hardyng, the next heir in line to the Vale; when the sickly Robert dies, Littlefinger intends to reveal Sansa's identity and claim her family stronghold of Winterfell in her name.


title: A Feast for Crows

text: On the Iron Islands, the late Balon Greyjoy's eldest surviving brother Euron returns from exile to claim the throne. To prevent this, his younger brother Aeron, a priest, calls a Kingsmoot to elect the successor. Although Euron's claim is contested by his other younger brother Victarion and Balon's daughter Asha, eventually Euron is chosen as king for his promise to conquer Westeros and control Daenerys Targaryen's dragons with an enchanted horn he possesses. Under Euron's leadership, the Iron Fleet attacks the Reach, threatening House Tyrell's seat at Highgarden. Euron sends Victarion east to propose marriage to Daenerys on his behalf, to thus gain a claim to the Iron Throne; but Victarion secretly decides to woo her for himself instead.


title: A Feast for Crows

text: In the southern region of Dorne, Prince Doran Martell is confronted by three of the Sand Snakes — his brother Oberyn's bastard daughters, who want vengeance for the death of their father. Because they are inciting the commonfolk, Doran has his guard captain Areo Hotah arrest and imprison them in the palace.


title: A Feast for Crows

text: A bold attempt by Doran's daughter Arianne to create a war of succession by crowning Tommen's sister Myrcella as queen of Westeros is thwarted. In the confusion, one of Arianne's co-conspirators, Ser Gerold "Darkstar" Dayne, attempts to kill Myrcella and disfigures her face. Myrcella's guardian, Ser Arys Oakheart, is killed by Areo Hotah. This strains Dorne's new alliance with the Iron Throne. Doran later reveals to his daughter that he has a much grander plan to bring down the Lannisters, and her brother Quentyn has gone east to bring back "Fire and Blood" through an alliance with Daenerys.


title: A Feast for Crows

text: Arriving in the foreign city of Braavos, Arya Stark finds her way to the cult of face-changing assassins known as the Faceless Men. Accepted as a novice, Arya is taught to abandon her previous identity, but her true identity asserts itself in the form of wolf dreams.


title: A Feast for Crows

text: Meanwhile, the Night's Watch lord commander Jon Snow has ordered Samwell Tarly to sail to the Citadel in Oldtown to train as a maester and warn the Seven Kingdoms about the return of the legendary hostile beings known as the Others. Sam is accompanied by the elderly Maester Aemon, the wildling girl Gilly, Gilly's newborn baby, and another Night's Watch member, Dareon. After the voyage is underway, Sam realizes that the child is actually the son of the wildling leader Mance Rayder, swapped with Gilly's real son. The party becomes temporarily stranded in Braavos when Aemon becomes sick, and Dareon absconds with their money. After learning that Daenerys possesses dragons, Aemon concludes that she is destined to fulfill a prophecy, and he needs to go assist her; but shortly after the party finally leaves Braavos, Aemon dies at the age of 102.


title: A Feast for Crows

text: After Sam's party leaves, Arya chances upon Dareon and murders him for deserting the Night's Watch. As punishment for the unauthorized killing, the Faceless Men then feed her a potion that causes blindness.


title: A Feast for Crows

text: At the end of the novel, Sam arrives at the Citadel and is introduced to Archmaester Marwyn. After learning about Aemon's death and the dragon prophecy about Daenerys, Marwyn leaves to find Daenerys himself. Samwell also encounters a fellow apprentice who introduces himself as Pate.


title: A Feast for Crows

text: The story is narrated from the point of view of 12 characters and a one-off prologue point of view. Unlike its predecessors, the fourth novel follows numerous minor characters as well.


title: A Feast for Crows

text: Martin released the first four "Iron Islands" chapters of "A Feast for Crows" as a novella called "Arms of the Kraken", published in the 305th edition of "Dragon" magazine, published in May 2003. Another chapbook featuring three Daenerys chapters was published for BookExpo 2005 although, following the geographical division of the book, these chapters were subsequently moved into the fifth volume in the series, "A Dance with Dragons".


title: A Feast for Crows

text: Martin originally planned for the fourth book to be called "A Dance with Dragons" with the story picking up five years after the events of "A Storm of Swords" (primarily to advance the ages of the younger characters). However, during the writing process, it was discovered that this was leading to an overreliance on flashbacks to fill in the gap. After twelve months or so of working on the book, Martin decided to abandon much of what had previously been written and start again, this time picking up immediately after the end of "A Storm of Swords". He announced this decision, along with the new title "A Feast for Crows", at Worldcon in Philadelphia on September 1, 2001. He also announced that "A Dance with Dragons" would now be the fifth book in the sequence.


title: A Feast for Crows

text: In May 2005, Martin announced that his manuscript for "A Feast for Crows" had hit 1527 completed pages but still remained unfinished, with "another hundred or so pages of roughs and incomplete chapters, as well as other chapters, sketched out but entirely unwritten." As the size of the manuscript for the 2000s "A Storm of Swords", his previous novel, had been a problem for publishers around the world at 1521 pages, Martin and his publishers had decided to split the narrative planned for "A Feast for Crows" into two books. Rather than divide the text in half chronologically, Martin opted to instead split the material by character and location:


title: A Feast for Crows

text: It was my feeling ... that we were better off telling all the story for half the characters, rather than half the story for all the characters. Cutting the novel in half would have produced two half-novels; our approach will produce two novels taking place simultaneously, but set hundreds or even thousands of miles apart, and involving different casts of characters (with some overlap).


title: A Feast for Crows

text: Martin noted that "A Feast for Crows" would focus on "Westeros, King's Landing, the riverlands, Dorne, and the Iron Islands," and that the next novel, "A Dance with Dragons", would cover "events in the east and north." Martin also added that the "A Song of Ice and Fire" series would now likely total seven novels. "A Feast for Crows" was published months later on October 17, 2005, over five years after the previous volume in the series, "A Storm of Swords". The parallel novel "A Dance with Dragons" was released on July 12, 2011.


title: A Feast for Crows

text: Though "A Feast for Crows" was the first novel in the sequence to debut at number one on "The New York Times" Best Seller list, it received more negative reviews in comparison with the previous novels in the series. Martin's decision to halve the plot in terms of character and location was highly controversial; many critics felt that this novel consisted of characters that people were less interested in. "Publishers Weekly" said, "Long-awaited doesn't begin to describe this fourth installment in bestseller Martin's staggeringly epic Song of Ice and Fire. [...]. This is not Act I Scene 4 but Act II Scene 1, laying groundwork more than advancing the plot, and it sorely misses its other half. The slim pickings here are tasty, but in no way satisfying." Salon.com's Andrew Leonard said in 2011, "I don't care how good a writer you are: If you subtract your three strongest characters from your tale, you severely undermine the basis for why readers fell under your spell in the first place. It didn't work. But there was also a sense in "A Feast of Crows" that Martin had lost his way. The characters whose stories he did tell wandered back and forth across a landscape devastated by war and oncoming winter, but didn't seem to be headed anywhere in particular." Remy Verhoeve of "The Huffington Post" noted in their 2011 "A Dance with Dragons" review that the fifth volume had to "repair some of the damage done by "A Feast for Crows", which frankly felt as if it was written by a ghost writer at times." Both books had "the same structural problems", being "sprawling and incoherent", and in her opinion "Feast" has the less interesting characters. "The Atlantic" Rachael Brown said in their "A Dance With Dragons" review that "Feast" was "bleak and plodding" and "sorely missed" Daenerys Targaryen, Tyrion Lannister, and Jon Snow.


title: Gin Blossoms

text: Gin Blossoms is an American alternative rock band formed in 1987 in Tempe, Arizona. They rose to prominence following the 1992 release of their first major label album, "New Miserable Experience", and the first single released from that album, "Hey Jealousy". "Hey Jealousy" became a Top 25 hit and went gold, and "New Miserable Experience" eventually went quadruple platinum; four other charting singles were released from the album. The band's follow-up album, "Congratulations I'm Sorry" (1996), went platinum and the single "As Long as It Matters" was nominated for a Grammy Award. Gin Blossoms broke up in 1997. Since reuniting in 2001, the band has released "Major Lodge Victory" in 2006, "No Chocolate Cake" in 2010, and "Mixed Reality" in 2018.


title: Gin Blossoms

text: During the band's early years, its members included lead guitarist and songwriter Doug Hopkins, bass guitarist Bill Leen, Jesse Valenzuela (lead vocalist at first, later rhythm guitarist and backing vocals), rhythm guitarist Richard Taylor, Taylor's replacement Steven Severson, drummer Chris McCann, McCann's replacement Dan Henzerling, and Severson's replacement Robin Wilson (rhythm guitarist at first, later lead vocalist). The band's name comes from a photo of W.C. Fields in Kenneth Anger's book "Hollywood Babylon", which bore the caption "W.C. Fields with gin blossoms", referring to the actor's telangiectasia-spotted face and rhinophymic nose by the slang term for the skin condition known as rosacea.


title: Gin Blossoms

text: Gin Blossoms became well known around the band's hometown of Phoenix. The band's frequent touring resulted in an increase in popularity. They independently recorded their first full-length album, "Dusted", which was released in December 1989.


title: Gin Blossoms

text: By the early 1990s, Wilson and Valenzuela had switched roles, with Wilson taking on lead vocal duties and Valenzuela concentrating on rhythm guitar and backing vocals. Along with Leen on bass and Hopkins on lead guitar, Phillip Rhodes became the new drummer. After being signed to A&M Records, the band began to work on their first major-label album. Initial attempts faltered and the band released an EP, "Up and Crumbling", instead.


title: Gin Blossoms

text: Gin Blossoms named their second album "New Miserable Experience". In February 1992, while still working to complete it, founding member and lead guitarist/songwriter Hopkins drank heavily and grew increasingly depressed. With the other members hesitant to fire Hopkins, A&M forcefully removed him from the band and withheld $15,000 owed to Hopkins until he agreed to sign over half of his publishing royalties and relinquish his mechanical royalties. Hopkins reluctantly agreed to these demands because of his dire financial situation. Scott Johnson was chosen by the band in December 1992 as Hopkins' stand-in on tour, and became a permanent member in 1994.


title: Gin Blossoms

text: "New Miserable Experience" became the band's breakthrough album. The first single released from the album was "Hey Jealousy", which had been written by Hopkins. The song reached No. 25 on the "Billboard" Hot 100 and No. 4 on "Billboard"s Mainstream Rock Tracks and later went gold, largely fueling the success of "New Miserable Experience". Estranged from the band, Hopkins committed suicide on December 5, 1993, after a reported five previous attempts (including one for which he was hospitalized two weeks prior to his death). The following year, another song by Hopkins, "Found Out About You", also reached No. 25 on the "Billboard" Hot 100 and climbed to No. 1 on "Billboard"s Modern Rock Tracks. "New Miserable Experience" eventually reached quadruple platinum status.


title: Gin Blossoms

text: Between their first and second albums, Gin Blossoms contributed the single "Til I Hear It from You" for the "Empire Records" soundtrack. It reached No. 9 on the "Billboard" Hot 100. Their second major album, "Congratulations I'm Sorry", was released in 1996. Yielding one top-ten hit ("Follow You Down", which peaked at No. 9 "Billboard" Hot 100), the album went platinum. The song "As Long as It Matters" was nominated for a Grammy Award for Best Pop Performance by a Duo or Group with Vocal.


title: Gin Blossoms

text: With chart success came opportunities to appear as musical guests on late-night television. Between 1992 and 1996, Gin Blossoms appeared on shows such as "Late Show with David Letterman" (many times between 1992 and 1996), "The Tonight Show with Jay Leno" (1993, 1994, 1996), "The Jon Stewart Show" (1993), "Late Night with Conan O’Brien" (1996), and as a featured musical act on "Saturday Night Live" (1996). One appearance on the "Late Show With David Letterman" featured a joint performance with Gin Blossoms and the members of Kiss, performing the latter's "Christine Sixteen". Gin Blossoms became a favorite of "Late Show" musical director Paul Shaffer, and their music was often featured as the show cut to and from commercials. The band was also a featured performer in the closing credits of the movie "Wayne's World 2" (1993), performing "Idiot Summer" on-screen as part of the fictional concert "Waynestock".


title: Gin Blossoms

text: Gin Blossoms broke up in early 1997. Wilson and Rhodes launched the Gas Giants while Leen formed a band called Rai and then retired from music to operate a rare book store. Valenzuela fronted a short-lived outfit called the Low Watts, released a solo album, and kept busy writing and producing. Johnson joined another Tempe-based band, Roger Clyne and the Peacemakers. Wilson ventured into producing as well, at his Mayberry Studios in Tempe, Arizona (now called Uranus Studios).


title: Gin Blossoms

text: The Gas Giants announced an "indefinite hiatus" in June 2001. On December 4, 2001, it was announced that Scott was leaving Roger Clyne and the Peacemakers to rejoin Gin Blossoms. The band regrouped and began playing together again in earnest in 2002, having done a couple of one-off shows in the interim. In Wilson's words, "We always said our breakup wasn't forever and right now we're all feeling like we want to be Gin Blossoms again. We make a noise together that we can't make otherwise. We respect and appreciate that we need each other to create that sound. This time we hope to avoid being swallowed by the chaos."


title: Gin Blossoms

text: In preparation for the band's official reunion show, Rhodes suffered a breakdown due to his ongoing battle with alcohol. Shortly after entering rehab, he was formally dismissed from the band. Phil Leavitt of Dada originally took Rhodes's place in the line up, and then Gary Smith (of The Pistoleros, another Tempe band) did. Scott Kusmirek took over drumming for the band from 2002 to 2004. In January 2005, it was announced that Rhodes, who had been sober for over two years, would rejoin the band. The re-entry of Rhodes was short-lived, however. Kusmirek returned to the band, taking Rhodes's place until September 30, 2008, when a press release issued by the band explained that he and the group had parted ways. John Richardson joined as the new drummer.


title: Gin Blossoms

text: The band's fourth album, "Major Lodge Victory", was originally recorded at Wilson's Mayberry Studios in Tempe. However, the album was re-recorded at Ardent Studios in Memphis, where the band had recorded all of their previous albums. "Major Lodge Victory" was released by Hybrid Recordings on August 8, 2006, and "Learning the Hard Way" was the first single. "Major Lodge Victory" entered the "Billboard" 200 album chart at number 159.


title: Gin Blossoms

text: Gin Blossoms released a live album, "Live In Concert", on May 15, 2009. This album contains live recordings of the band's hits such as "Hey Jealousy" and "Follow You Down", as well as more recent singles such as "Learning the Hard Way" and "Long Time Gone", and a live cover version of Elton John's "Rocket Man". The band's fifth studio album, "No Chocolate Cake", was released on September 28, 2010. The first single, "Miss Disarray" was released to radio stations on August 2, 2010. Over the 2010 Thanksgiving holiday the band traveled to Iraq and played a series of shows for American troops stationed there.


title: Gin Blossoms

text: The band announced on its website on March 4, 2012, that Richardson had left the band to pursue other recording and performing projects. The band stated in its news release, "John is a great drummer and all of us support his passion for recording. We all wish him the very best and thank him for all his hard work and dedication." The band also announced that Scott Hessel would be its road drummer. Hessel had been a member of another Tempe band, Let Go. Gin Blossoms joined Everclear, Sugar Ray, Lit, and Marcy Playground on the Summerland Tour 2012, a 31-date nationwide tour that began on June 28 in Saratoga, California and ended on August 11 in Laughlin, Nevada.


title: Gin Blossoms

text: From July 24, 2012 through October 13, 2012, Doug Swartz filled in for Scott Hessel during the Summerland Tour and other performances through the months into the middle of October.


title: Gin Blossoms

text: In 2016, Johnson announced in an interview that the band was expected to begin recording its sixth studio album with producer Mitch Easter in the fall. Two years later, "Mixed Reality" was released on Cleopatra Records on June 15, 2018. The album was produced by Don Dixon.


title: Gin Blossoms

text: In January 2022 the band announced a tour to celebrate the 30th anniversary of "New Miserable Experience". The tour was cut short in March 2022 due to an accident in which bassist Bill Leen broke his arm.


title: Gin Blossoms

text: Gin Blossoms has been described as an alternative rock, jangle pop, power pop, and post-grunge band. According to "Rolling Stone", the band excels at "marrying world-weary lyrics with ebullient melodies." In 2017, the Salina Journal described Gin Blossoms as a "Tempe, Ariz.-based indie band [acclaimed] by critics and fans alike for its chiming guitars, introspective lyrics and catchy pop-rock melodies," adding that "Gin Blossoms has maintained its longevity by being mostly a road band." The group is known for the "Mill Avenue sound", or "southwestern sound", similar to other bands from Arizona such as The Sidewinders, The Refreshments, The Meat Puppets, and Dead Hot Workshop.


title: Sundial

text: A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the "dial") and a gnomon, which casts a shadow onto the dial. As the Sun appears to move through the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of day. The "style" is the time-telling edge of the gnomon, though a single point or "nodus" may be used. The gnomon casts a broad shadow; the shadow of the style shows the time. The gnomon may be a rod, wire, or elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year. The style's angle from horizontal is equal to the sundial's geographical latitude.


title: Sundial

text: The term "sundial" can refer to any device that uses the Sun's altitude or azimuth (or both) to show the time. Sundials are valued as decorative objects, metaphors, and objects of intrigue and mathematical study.


title: Sundial

text: The passing of time can be observed by placing a stick in the sand or a nail in a board and placing markers at the edge of a shadow or outlining a shadow at intervals. It is common for inexpensive, mass-produced decorative sundials to have incorrectly aligned gnomons, shadow lengths, and hour-lines, which cannot be adjusted to tell correct time.


title: Sundial

text: There are several different types of sundials. Some sundials use a shadow or the edge of a shadow while others use a line or spot of light to indicate the time.


title: Sundial

text: The shadow-casting object, known as a "gnomon", may be a long thin rod or other object with a sharp tip or a straight edge. Sundials employ many types of gnomon. The gnomon may be fixed or moved according to the season. It may be oriented vertically, horizontally, aligned with the Earth's axis, or oriented in an altogether different direction determined by mathematics.


title: Sundial

text: Given that sundials use light to indicate time, a line of light may be formed by allowing the Sun's rays through a thin slit or focusing them through a cylindrical lens. A spot of light may be formed by allowing the Sun's rays to pass through a small hole, window, oculus, or by reflecting them from a small circular mirror. A spot of light can be as small as a pinhole in a solargraph or as large as the oculus in the Pantheon.


title: Sundial

text: Sundials also may use many types of surfaces to receive the light or shadow. Planes are the most common surface, but partial spheres, cylinders, cones and other shapes have been used for greater accuracy or beauty.


title: Sundial

text: Sundials differ in their portability and their need for orientation. The installation of many dials requires knowing the local latitude, the precise vertical direction (e.g., by a level or plumb-bob), and the direction to true North. Portable dials are self-aligning: for example, it may have two dials that operate on different principles, such as a horizontal and analemmatic dial, mounted together on one plate. In these designs, their times agree only when the plate is aligned properly.


title: Sundial

text: Sundials may indicate the local solar time only. To obtain the national clock time, three corrections are required:


title: Sundial

text: The principles of sundials are understood most easily from the Sun's apparent motion. The Earth rotates on its axis, and revolves in an elliptical orbit around the Sun. An excellent approximation assumes that the Sun revolves around a stationary Earth on the celestial sphere, which rotates every 24 hours about its celestial axis. The celestial axis is the line connecting the celestial poles. Since the celestial axis is aligned with the axis about which the Earth rotates, the angle of the axis with the local horizontal is the local geographical latitude.


title: Sundial

text: Unlike the fixed stars, the Sun changes its position on the celestial sphere, being (in the northern hemisphere) at a positive declination in spring and summer, and at a negative declination in autumn and winter, and having exactly zero declination (i.e., being on the celestial equator) at the equinoxes. The Sun's celestial longitude also varies, changing by one complete revolution per year. The path of the Sun on the celestial sphere is called the ecliptic. The ecliptic passes through the twelve constellations of the zodiac in the course of a year.


title: Sundial

text: This model of the Sun's motion helps to understand sundials. If the shadow-casting gnomon is aligned with the celestial poles, its shadow will revolve at a constant rate, and this rotation will not change with the seasons. This is the most common design. In such cases, the same hour lines may be used throughout the year. The hour-lines will be spaced uniformly if the surface receiving the shadow is either perpendicular (as in the equatorial sundial) or circular about the gnomon (as in the armillary sphere).


title: Sundial

text: In other cases, the hour-lines are not spaced evenly, even though the shadow rotates uniformly. If the gnomon is "not" aligned with the celestial poles, even its shadow will not rotate uniformly, and the hour lines must be corrected accordingly. The rays of light that graze the tip of a gnomon, or which pass through a small hole, or reflect from a small mirror, trace out a cone aligned with the celestial poles. The corresponding light-spot or shadow-tip, if it falls onto a flat surface, will trace out a conic section, such as a hyperbola, ellipse or (at the North or South Poles) a circle.


title: Sundial

text: This conic section is the intersection of the cone of light rays with the flat surface. This cone and its conic section change with the seasons, as the Sun's declination changes; hence, sundials that follow the motion of such light-spots or shadow-tips often have different hour-lines for different times of the year. This is seen in shepherd's dials, sundial rings, and vertical gnomons such as obelisks. Alternatively, sundials may change the angle or position (or both) of the gnomon relative to the hour lines, as in the analemmatic dial or the Lambert dial.


title: Sundial

text: The earliest sundials known from the archaeological record are shadow clocks (1500 BC or BCE) from ancient Egyptian astronomy and Babylonian astronomy. Presumably, humans were telling time from shadow-lengths at an even earlier date, but this is hard to verify. In roughly 700 BC, the Old Testament describes a sundial—the "dial of Ahaz" mentioned in and . By 240 BC Eratosthenes had estimated the circumference of the world using an obelisk and a water well and a few centuries later Ptolemy had charted the latitude of cities using the angle of the sun. The people of Kush created sun dials through geometry. The Roman writer Vitruvius lists dials and shadow clocks known at that time in his "De architectura". The Tower of Winds constructed in Athens included sundial and a water clock for telling time. A canonical sundial is one that indicates the canonical hours of liturgical acts. Such sundials were used from the 7th to the 14th centuries by the members of religious communities. The Italian astronomer Giovanni Padovani published a treatise on the sundial in 1570, in which he included instructions for the manufacture and laying out of mural (vertical) and horizontal sundials. Giuseppe Biancani's "Constructio instrumenti ad horologia solaria" (c. 1620) discusses how to make a perfect sundial. They have been commonly used since the 16th century.


title: Sundial

text: In general, sundials indicate the time by casting a shadow or throwing light onto a surface known as a "dial face" or "dial plate". Although usually a flat plane, the dial face may also be the inner or outer surface of a sphere, cylinder, cone, helix, and various other shapes.


title: Sundial

text: The time is indicated where a shadow or light falls on the dial face, which is usually inscribed with hour lines. Although usually straight, these hour lines may also be curved, depending on the design of the sundial (see below). In some designs, it is possible to determine the date of the year, or it may be required to know the date to find the correct time. In such cases, there may be multiple sets of hour lines for different months, or there may be mechanisms for setting/calculating the month. In addition to the hour lines, the dial face may offer other data—such as the horizon, the equator and the tropics—which are referred to collectively as the dial furniture.


title: Sundial

text: The entire object that casts a shadow or light onto the dial face is known as the sundial's "gnomon". However, it is usually only an edge of the gnomon (or another linear feature) that casts the shadow used to determine the time; this linear feature is known as the sundial's "style". The style is usually aligned parallel to the axis of the celestial sphere, and therefore is aligned with the local geographical meridian. In some sundial designs, only a point-like feature, such as the tip of the style, is used to determine the time and date; this point-like feature is known as the sundial's "nodus".


title: Sundial

text: The gnomon is usually fixed relative to the dial face, but not always; in some designs such as the analemmatic sundial, the style is moved according to the month. If the style is fixed, the line on the dial plate perpendicularly beneath the style is called the "substyle", meaning "below the style". The angle the style makes with the plane of the dial plate is called the substyle height, an unusual use of the word "height" to mean an "angle". On many wall dials, the substyle is not the same as the noon line (see below). The angle on the dial plate between the noon line and the substyle is called the "substyle distance", an unusual use of the word "distance" to mean an "angle".


title: Sundial

text: By tradition, many sundials have a motto. The motto is usually in the form of an epigram: sometimes sombre reflections on the passing of time and the brevity of life, but equally often humorous witticisms of the dial maker. One such quip is, "I am a sundial, and I make a botch, Of what is done much better by a watch."


title: Sundial

text: A dial is said to be "equiangular" if its hour-lines are straight and spaced equally. Most equiangular sundials have a fixed gnomon style aligned with the Earth's rotational axis, as well as a shadow-receiving surface that is symmetrical about that axis; examples include the equatorial dial, the equatorial bow, the armillary sphere, the cylindrical dial and the conical dial. However, other designs are equiangular, such as the Lambert dial, a version of the analemmatic sundial with a moveable style.


title: Sundial

text: A sundial at a particular latitude in one hemisphere must be reversed for use at the opposite latitude in the other hemisphere. A vertical direct south sundial in the Northern Hemisphere becomes a vertical direct north sundial in the Southern Hemisphere. To position a horizontal sundial correctly, one has to find true North or South. The same process can be used to do both. The gnomon, set to the correct latitude, has to point to the true South in the Southern hemisphere as in the Northern Hemisphere it has to point to the true North. The hour numbers also run in opposite directions, so on a horizontal dial they run anticlockwise (US: counterclockwise) rather than clockwise.


title: Sundial

text: Sundials which are designed to be used with their plates horizontal in one hemisphere can be used with their plates vertical at the complementary latitude in the other hemisphere. For example, the illustrated sundial in Perth, Australia, which is at latitude 32 degrees South, would function properly if it were mounted on a south-facing vertical wall at latitude 58 (i.e. 90–32) degrees North, which is slightly further North than Perth, Scotland. The surface of the wall in Scotland would be parallel with the horizontal ground in Australia (ignoring the difference of longitude), so the sundial would work identically on both surfaces. Correspondingly, the hour marks, which run counterclockwise on a horizontal sundial in the southern hemisphere, also do so on a vertical sundial in the northern hemisphere. (See the first two illustrations at the top of this article.) On horizontal northern-hemisphere sundials, and on vertical southern-hemisphere ones, the hour marks run clockwise.


title: Sundial

text: The most common reason for a sundial to differ greatly from clock time is that the sundial has not been oriented correctly or its hour lines have not been drawn correctly. For example, most commercial sundials are designed as "horizontal sundials" as described above. To be accurate, such a sundial must have been designed for the local geographical latitude and its style must be parallel to the Earth's rotational axis; the style must be aligned with true North and its "height" (its angle with the horizontal) must equal the local latitude. To adjust the style height, the sundial can often be tilted slightly "up" or "down" while maintaining the style's north-south alignment.


title: Sundial

text: Some areas of the world practice daylight saving time, which changes the official time, usually by one hour. This shift must be added to the sundial's time to make it agree with the official time.


title: Sundial

text: A standard time zone covers roughly 15° of longitude, so any point within that zone which is not on the reference longitude (generally a multiple of 15°) will experience a difference from standard time that is equal to 4 minutes of time per degree. For illustration, sunsets and sunrises are at a much later "official" time at the western edge of a time-zone, compared to sunrise and sunset times at the eastern edge. If a sundial is located at, say, a longitude 5° west of the reference longitude, then its time will read 20 minutes slow, since the Sun appears to revolve around the Earth at 15° per hour. This is a constant correction throughout the year. For equiangular dials such as equatorial, spherical or Lambert dials, this correction can be made by rotating the dial surface by an angle equaling the difference in longitude, without changing the gnomon position or orientation. However, this method does not work for other dials, such as a horizontal dial; the correction must be applied by the viewer.


title: Sundial

text: However, for political and practical reasons, time-zone boundaries have been skewed. At their most extreme, time zones can cause official noon, including daylight savings, to occur up to three hours early (in which case the Sun is actually on the meridian at official clock time of 3 pm). This occurs in the far west of Alaska, China, and Spain. For more details and examples, see time zones.


title: Sundial

text: Although the Sun appears to rotate uniformly about the Earth, in reality this motion is not perfectly uniform. This is due to the eccentricity of the Earth's orbit (the fact that the Earth's orbit about the Sun is not perfectly circular, but slightly elliptical) and the tilt (obliquity) of the Earth's rotational axis relative to the plane of its orbit. Therefore, sundial time varies from standard clock time. On four days of the year, the correction is effectively zero. However, on others, it can be as much as a quarter-hour early or late. The amount of correction is described by the equation of time. This correction is equal worldwide: it does not depend on the local latitude or longitude of the observer's position. It does, however, change over long periods of time, (centuries or more,)


title: Sundial

text: because of slow variations in the Earth's orbital and rotational motions. Therefore, tables and graphs of the equation of time that were made centuries ago are now significantly incorrect. The reading of an old sundial should be corrected by applying the present-day equation of time, not one from the period when the dial was made.


title: Sundial

text: In some sundials, the equation of time correction is provided as an informational plaque affixed to the sundial, for the observer to calculate. In more sophisticated sundials the equation can be incorporated automatically. For example, some equatorial bow sundials are supplied with a small wheel that sets the time of year; this wheel in turn rotates the equatorial bow, offsetting its time measurement. In other cases, the hour lines may be curved, or the equatorial bow may be shaped like a vase, which exploits the changing altitude of the sun over the year to effect the proper offset in time.


title: Sundial

text: A "heliochronometer" is a precision sundial first devised in about 1763 by Philipp Hahn and improved by Abbé Guyoux in about 1827.


title: Sundial

text: It corrects apparent solar time to mean solar time or another standard time. Heliochronometers usually indicate the minutes to within 1 minute of Universal Time.


title: Sundial

text: The Sunquest sundial, designed by Richard L. Schmoyer in the 1950s, uses an analemmic inspired gnomon to cast a shaft of light onto an equatorial time-scale crescent. Sunquest is adjustable for latitude and longitude, automatically correcting for the equation of time, rendering it "as accurate as most pocket watches". Similarly, in place of the shadow of a gnomon the sundial at Miguel Hernández University uses the solar projection of a graph of the equation of time intersecting a time scale to display clock time directly.


title: Sundial

text: An analemma may be added to many types of sundials to correct apparent solar time to mean solar time or another standard time. These usually have hour lines shaped like "figure eights" (analemmas) according to the equation of time. This compensates for the slight eccentricity in the Earth's orbit and the tilt of the Earth's axis that causes up to a 15-minute variation from mean solar time. This is a type of dial furniture seen on more complicated horizontal and vertical dials.


title: Sundial

text: Prior to the invention of accurate clocks, in the mid-17th Century, sundials were the only timepieces in common use, and were considered to tell the "right" time. The Equation of Time was not used. After the invention of good clocks, sundials were still considered to be correct, and clocks usually incorrect. The Equation of Time was used in the opposite direction from today, to apply a correction to the time shown by a clock to make it agree with sundial time. Some elaborate "equation clocks", such as one made by Joseph Williamson in 1720, incorporated mechanisms to do this correction automatically. (Williamson's clock may have been the first-ever device to use a differential gear.) Only after about 1800 was uncorrected clock time considered to be "right", and sundial time usually "wrong", so the Equation of Time became used as it is today.


title: Sundial

text: The most commonly observed sundials are those in which the shadow-casting style is fixed in position and aligned with the Earth's rotational axis, being oriented with true North and South, and making an angle with the horizontal equal to the geographical latitude. This axis is aligned with the celestial poles, which is closely, but not perfectly, aligned with the pole star Polaris. For illustration, the celestial axis points vertically at the true North Pole, where it points horizontally on the equator. The world's largest axial gnomon sundial is the mast of the Sundial Bridge at Turtle Bay in Redding, California . A formerly world's largest gnomon is at Jaipur, raised 26°55" above horizontal, reflecting the local latitude.


title: Sundial

text: On any given day, the Sun appears to rotate uniformly about this axis, at about 15° per hour, making a full circuit (360°) in 24 hours. A linear gnomon aligned with this axis will cast a sheet of shadow (a half-plane) that, falling opposite to the Sun, likewise rotates about the celestial axis at 15° per hour. The shadow is seen by falling on a receiving surface that is usually flat, but which may be spherical, cylindrical, conical or of other shapes. If the shadow falls on a surface that is symmetrical about the celestial axis (as in an armillary sphere, or an equatorial dial), the surface-shadow likewise moves uniformly; the hour-lines on the sundial are equally spaced. However, if the receiving surface is not symmetrical (as in most horizontal sundials), the surface shadow generally moves non-uniformly and the hour-lines are not equally spaced; one exception is the Lambert dial described below.


title: Sundial

text: Some types of sundials are designed with a fixed gnomon that is not aligned with the celestial poles like a vertical obelisk. Such sundials are covered below under the section, "Nodus-based sundials".