title: Rick DiPietro

text: DiPietro attended Saint Sebastian's School. He played one season (1999–2000) with Boston University in the National Collegiate Athletic Association (NCAA)'s Hockey East. In that one year, DiPietro was named to the All-Rookie Team, named Second Team All-Hockey East, awarded the team's co-MVP and was named Hockey East's Rookie of the Year. In addition, DiPietro nearly set the NCAA record for most saves in a game when he stopped 77 out of 80 shots in a 3–2 quadruple overtime loss to St. Lawrence University during the NCAA regional final. In his one and only Beanpot Tournament, DiPietro was named MVP and won the Eberly Trophy awarded to the tournament's top goaltender.


title: Rick DiPietro

text: DiPietro was drafted first overall by the New York Islanders in the 2000 NHL Entry Draft, out of Boston University. Islanders general manager Mike Milbury traded incumbent goalie Roberto Luongo to create room for the highly touted DiPietro, who was known for his mobility and puckhandling skills. DiPietro became the fourth American to occupy the top draft position in the NHL Entry Draft.


title: Rick DiPietro

text: A groin injury during training camp resulted in DiPietro starting the season with the Bridgeport Sound Tigers, the Islanders minor league affiliate in the American Hockey League (AHL). He was subsequently called up twice to join the Islanders, but did not play a game until January 27, 2001, when he debuted against the Buffalo Sabres. DiPietro's NHL debut was widely anticipated, but in 20 games in the 2000–01 season he managed just three wins against 15 losses for a struggling Islanders team. He played ten games the next season, as well as one playoff game, before being called up permanently in the 2003–04 season. His goals against average (GAA) improved from 3.49 in the 2000–01 season to 2.36 in the 2003–04 season.


title: Rick DiPietro

text: On September 12, 2006, DiPietro signed a 15-year, $67.5 million contract with the Islanders, topping former teammate Alexei Yashin's contract signed before the start of the 2001–02 season of 10 years. "Newsday" reported that the team offered him a 15-year contract in September 2005, but the NHL front office discouraged the Islanders from making such an offer. Instead, DiPietro had signed on a one-year deal with the Islanders.


title: Rick DiPietro

text: DiPietro's contract, the longest under the 2005 NHL collective bargaining agreement, was nearly surpassed during the 2010 off-season, when the New Jersey Devils attempted to sign Ilya Kovalchuk to a 17-year contract, but that offer was rejected by the NHL on the grounds of salary cap circumvention.


title: Rick DiPietro

text: On March 5, 2007, DiPietro broke an Islanders franchise record by making 56 saves in a 2–1 shootout loss to the New York Rangers. The previous record was 55 saves, held by both Félix Potvin and Billy Smith. The record was later broken by Dwayne Roloson in 2009.


title: Rick DiPietro

text: On March 13, 2007, DiPietro suffered a concussion after a collision with Montreal Canadiens forward Steve Bégin, when DiPietro raced out to poke check a puck at the blueline at 15:41 of the first period. DiPietro returned for four games but then missed the rest of the regular season after he sustained another concussion in game against the Rangers. He returned to play games two through five of the Islanders' first round playoff series against the Buffalo Sabres.


title: Rick DiPietro

text: The concussion was the start of a string of injuries. DiPietro underwent surgery in the 2007 off season to fix a torn labrum in his hip.


title: Rick DiPietro

text: In 2007, DiPietro expressed a desire to become more of a team leader. He said, "I'm a competitive person, and I have a tendency to have a short fuse with guys sometimes. That's something, as a leader, that you just can't do."


title: Rick DiPietro

text: On November 19, 2007, DiPietro recorded his 100th NHL career win when the Islanders beat the New York Rangers 2–1.


title: Rick DiPietro

text: DiPietro was selected to appear in his first and only All-Star Game in 2008 as a reserve, but was later named the starter after New Jersey Devils goaltender Martin Brodeur dropped out. During the skills competition the night before, DiPietro injured his hip during the shootout competition. DiPietro continued to play until the Islanders no longer had a chance to make the playoffs and on March 19, it was announced that DiPietro would miss the remainder of the 2007–08 season because of the hip surgery.


title: Rick DiPietro

text: On June 3, 2008, DiPietro went on a Sirius satellite radio show being hosted by "Bubba the Love Sponge," where he told Bubba he would be undergoing knee surgery later that day. The surgery was done on the meniscus in his left knee. DiPietro sat out the first four games of the 2008–09 season (or, controversially, was on the bench as the backup) before starting the team's fifth game in Florida. He played two games after that, but left after the first period his third game back. After that, he was placed on injured reserve for an "undisclosed lower body injury." On November 1, it was announced DiPietro had undergone another knee surgery after injuring his meniscus. It is unknown whether it is the same knee that was operated on earlier that year. DiPietro returned to the team on December 26, 2008. He won his first game back and earned an assist, which broke Billy Smith's team record for points by a goaltender. On January 20, 2009, Islanders general manager Garth Snow announced that DiPietro would miss the rest of the 2008–09 season due to post-arthroscopic surgical swelling in his right knee.


title: Rick DiPietro

text: On January 8, 2010, DiPietro returned from injury in a 4–3 loss to the Dallas Stars. His last start of 2010 came against the Carolina Hurricanes on February 6. He earned his fifth loss in seven starts, as the Islanders fell 3–1. On February 13, he was listed as day-to-day with the flu, and less than a month later, swelling in his left-knee caused him to be placed on the injured reserve list effective March 2, 2010; he did not return for the rest of the season.


title: Rick DiPietro

text: DiPietro started the 2010–11 season apparently healthy and worked in a "platoon" tandem with Dwayne Roloson. On December 21, 2010, he was placed on injured reserve, however, due to knee swelling. He returned in December, though due to the strong play of Roloson, he was primarily used as a backup. He made his first start since returning on December 29 in a game against the Pittsburgh Penguins. DiPietro and the Islanders defeated Pittsburgh in a 2–1 shootout decision behind the sharp play of DiPietro. On December 31, the Islanders traded Roloson to the Tampa Bay Lightning, confirming the starting job for DiPietro. On February 2, 2011, In his first game against the Penguins since his shootout win, DiPietro engaged in a rare "goaltender fight" against Pittsburgh's Brent Johnson in the final seconds of the game. He was knocked out and had his jaw broken by a single punch to the face by Johnson. The injuries kept him off the ice for weeks. It is not known if the knee swelling was from the fight or another reason. DiPietro returned shortly to finish the season, wearing the old helmet and cage combo worn by former Islanders goaltender Chris Osgood.


title: Rick DiPietro

text: The start of the 2011–12 season featured DiPietro in a three-way tandem with Al Montoya and Evgeni Nabokov. Due to a strong pre-season and his performances in DiPietro's absence the previous year, Montoya started the first two games and DiPietro was the backup. During practice for the Islanders' third game, DiPietro took a hard shot to his mask from Brian Rolston, which concussed him and sidelined him indefinitely. DiPietro returned to action in late October, returning to the more conventional one piece goaltender mask he sported for the majority of his career. On November 5, 2011, DiPietro made 25 saves to earn his first win of the 2011–12 season. Shortly after, he injured his groin and was again out indefinitely; he later required surgery to repair a hernia in the area, sidelining him for the remainder of the season.


title: Rick DiPietro

text: After playing only three games in the lockout shortened 2012–13 season, DiPietro was waived by the Islanders and was sent to their AHL affiliate, the Bridgeport Sound Tigers. He had eight years remaining on his NHL contract. DiPietro started his first game as a member of the Sound Tigers on March 1, 2013. He allowed two goals on the first two shots of the game and five in the first period. He did not return from the locker room for the second period of play as the game eventually ended 7–3 in favor of the opposing Connecticut Whale.


title: Rick DiPietro

text: DiPietro's series of injuries during the latter part of his NHL career earned him the nickname "Rickety".


title: Rick DiPietro

text: On July 1, 2013, the Islanders announced that DiPietro would be placed on unconditional waivers and have the remainder of his contract bought out on a compliance. The buyout was completed 2 days later with DiPietro agreeing to be paid 2/3s of the $36 million he would have been owed over the next 8 years at a rate of $1.5 million per year over the next 16 years. DiPietro signed a professional tryout contract on October 25, 2013 with the Carolina Hurricanes' AHL affiliate, Charlotte Checkers, playing his first game 5 days later in which he stopped 25 of 29 shots in a 5–2 loss to the Grand Rapids Griffins. He was cut by the Checkers on November 26.


title: Rick DiPietro

text: After retiring DiPietro turned to radio broadcasting. He is a co-host of "DiPietro and Rothenberg" with Dave Rothenberg from 5-8 AM each weekday morning on WEPN-FM (98.7 ESPN NY)


title: Rick DiPietro

text: In 2019, DiPietro was named the Head Boys' Hockey Coach at the Portledge School. He was officially announced as an analyst on National Hockey League (NHL) telecasts on ESPN beginning with the upcoming season on June 29, 2021.


title: Rick DiPietro

text: DiPietro made his international debut at the junior level for the United States at the 1999 IIHF World U18 Championships. He would then play in the two following World Junior Championships in 2000 and 2001, awarded in the former as the tournament's best goaltender and selected to the All-Star Team.


title: Rick DiPietro

text: He made his full international debut soon after his WJC experience with the United States at the 2001 World Championships. He would go on to compete for Team USA in the 2004 World Cup of Hockey and the 2005 World Championships.


title: Rick DiPietro

text: Along with former Islanders teammates Jason Blake and Mark Parrish, DiPietro was named to the United States national hockey team at the 2006 Winter Olympics in Turin, Italy, in February 2006. DiPietro was the U.S.' number one goaltender for the tournament, starting four of the team's six games. DiPietro played well, sporting a 2.28 GAA, but went 1–3 in the men's tournament.


title: Foxfire

text: Foxfire, also called fairy fire and chimpanzee fire, is the bioluminescence created by some species of fungi present in decaying wood. The bluish-green glow is attributed to a luciferase, an oxidative enzyme, which emits light as it reacts with a luciferin. The phenomenon has been known since ancient times, with its source determined in 1823.


title: Foxfire

text: Foxfire is the bioluminescence created by some species of fungi present in decaying wood. It occurs in a number of species, including "Panellus stipticus", "Omphalotus olearius" and "Omphalotus nidiformis". The bluish-green glow is attributed to luciferin, which emits light after oxidation catalyzed by the enzyme luciferase. Some believe that the light attracts insects to spread spores, or acts as a warning to hungry animals, like the bright colors exhibited by some poisonous or unpalatable animal species. Although generally very dim, in some cases foxfire is bright enough to read by.


title: Foxfire

text: The oldest recorded documentation of foxfire is from 382 B.C., by Aristotle, whose notes refer to a light that, unlike fire, was cold to the touch. The Roman thinker Pliny the Elder also mentioned glowing wood in olive groves.


title: Foxfire

text: Foxfire was used to illuminate the needles on the barometer and the compass of "Turtle", an early submarine. This is commonly thought to have been suggested by Benjamin Franklin; a reading of the correspondence from Benjamin Gale, however, shows that Benjamin Franklin was only consulted for alternative forms of lighting when the cold temperatures rendered the foxfire inactive.


title: Foxfire

text: After many more literary references to foxfire by early scientists and naturalists, its cause was discovered in 1823. The glow emitted from wooden support beams in mines was examined, and it was found that the luminescence came from fungal growth.


title: Foxfire

text: The "fox" in "foxfire" may derive from the Old French word , meaning "false", rather than from the name of the animal. The association of foxes with such fires is widespread, however, and occurs also in Japanese folklore.


title: Dating sim

text: Dating sims are often dialog-heavy and focus on time management. The player must befriend and carefully build and maintain a relationship with one or more characters. The gameplay is largely dependent on statistics. These games also often involve raising stats that reflect the player's skills and can be combined with other genres. Series such as "Sakura Wars" and "Persona" combine RPG gameplay with dating sim gameplay.


title: Dating sim

text: The term "dating sim" is also sometimes used incorrectly in English as a generic term for , especially visual novels focused on romance. This can lead to confusion, as visual novels are considered a subgenre of adventure games and are not included in the dating sim genre. While the two genres often share a common visual presentation, dating sims are considered to be more statistically based, whereas visual novels focus on telling a branching story.


title: Dating sim

text: The first game that set the standard for the dating sim genre was "Dōkyūsei" (1992), which relied more on timed events than dialogue choices. However, "Tokimeki Memorial" (1994) truly popularized dating sims in Japan, in which the player, a high school student has the ability to date a dozen different girls. Games such as "Sakura Wars" and "Persona" (both series started in 1996) are RPGs with dating sim elements.


title: Dating sim

text: In a typical dating sim, the player controls a male avatar surrounded by female characters. The gameplay involves conversing with a selection of girls, attempting to increase their internal "love meter" through correct choices of dialogue. The game lasts for a fixed period of game time, such as one month or three years. When the game ends, the player either loses the game if he failed to properly win over any of the girls, or "finishes" one of the girls, often by having sex with her, marrying her (as in Magical Date), and/or achieving eternal love. This gives the games more replay value, since the player can focus on a different girl each time, trying to get a different ending.


title: Dating sim

text: Dating sims often revolve almost entirely around relationship-building, usually featuring complex character interactions and branching dialogue trees, and often presenting the player's possible responses word-for-word as the player character would say them. Dating sims such as "Tokimeki Memorial", and some role-playing games with similar relationship based mechanics to the genre such as "Persona", often give choices that have a different number of associated "mood points" which influence a player character's relationship and future conversations with a non-player character. These games often feature a day-night cycle with a time scheduling system that provides context and relevance to character interactions, allowing players to choose when and if to interact with certain characters, which in turn influences their responses during later conversations.


title: Dating sim

text: While bishōjo games make up the bulk of dating sims, other types of games exist. Games where the player character is female and potential objects of affection are male are known as GxB or otome games. Homosexual relationships are also possible, as there are games with no specific gender lines ("all pairings"). There are also Girls' Love games, which focus on female/female relationships, and Boys' Love games, which focus on male/male pairings.


title: Dating sim

text: There are many variations on this theme: high-school romances are the most common, but a dating sim may also take place in a fantasy setting and involve such challenges as defending one's girl from monsters.


title: Dating sim

text: One game series that often includes dating, with the goal of marriage, is the farming sim series "Harvest Moon". The subplot of dating is more focused towards choosing one of several girls or guys (dependent on the player character's gender) and offering them presents or joining them on events in the game. The "Star Ocean" series of RPGs also feature dating sim elements in a similar manner.


title: Dating sim

text: Some Japanese dating sims may allow the player to have romantic or sexual relationships with characters in their teens. The degree of sexual content varies, but may often include intercourse. Sexually explicit dating sims may fall into the category of H Game or Eroge. Eroge only gets released to PC because large Japanese game companies do not want to release games with sexual content on their game consoles. Because of this, Eroge companies make a censored all-ages (15+) version of the PC version for various consoles. Censored versions often contain additional endings and added scenes to compensate for the absence of sexual scenes.


title: Liquid fluoride thorium reactor

text: The liquid fluoride thorium reactor (LFTR; often pronounced "lifter") is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based, molten, liquid salt for fuel. In a typical design, the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.


title: Liquid fluoride thorium reactor

text: Molten-salt-fueled reactors (MSRs) supply the nuclear fuel mixed into a molten salt. They should not be confused with designs that use a molten salt for "cooling" only (fluoride high-temperature reactors, FHRs) and still have a solid fuel. Molten salt reactors, as a class, include both burners and breeders in fast or thermal spectra, using fluoride or chloride salt-based fuels and a range of fissile or fertile consumables. LFTRs are defined by the use of fluoride fuel salts and the breeding of thorium into uranium-233 in the thermal neutron spectrum.


title: Liquid fluoride thorium reactor

text: The LFTR concept was first investigated at the Oak Ridge National Laboratory Molten-Salt Reactor Experiment in the 1960s, though the MSRE did not use thorium. The LFTR has recently been the subject of a renewed interest worldwide. Japan, China, the UK and private US, Czech, Canadian and Australian companies have expressed the intent to develop, and commercialize the technology.


title: Liquid fluoride thorium reactor

text: LFTRs differ from other power reactors in almost every aspect: they use thorium that is turned into uranium, instead of using uranium directly; they are refueled by pumping without shutdown. Their liquid salt coolant allows higher operating temperature and much lower pressure in the primary cooling loop. These distinctive characteristics give rise to many potential advantages, as well as design challenges.


title: Liquid fluoride thorium reactor

text: By 1946, eight years after the discovery of nuclear fission, three fissile isotopes had been publicly identified for use as nuclear fuel:


title: Liquid fluoride thorium reactor

text: Th-232, U-235 and U-238 are primordial nuclides, having existed in their current form for over 4.5 billion years, predating the formation of the Earth; they were forged in the cores of dying stars through the r-process and scattered across the galaxy by supernovas. Their radioactive decay produces about half of the Earth's internal heat.


title: Liquid fluoride thorium reactor

text: For technical and historical reasons, the three are each associated with different reactor types. U-235 is the world's primary nuclear fuel and is usually used in light water reactors. U-238/Pu-239 has found the most use in liquid sodium fast breeder reactors and CANDU Reactors. Th-232/U-233 is best suited to molten salt reactors (MSR).


title: Liquid fluoride thorium reactor

text: Alvin M. Weinberg pioneered the use of the MSR at Oak Ridge National Laboratory. At ORNL, two prototype molten salt reactors were successfully designed, constructed and operated. These were the Aircraft Reactor Experiment in 1954 and Molten-Salt Reactor Experiment from 1965 to 1969. Both test reactors used liquid fluoride fuel salts. The MSRE notably demonstrated fueling with U-233 and U-235 during separate test runs. Weinberg was removed from his post and the MSR program closed down in the early 1970s, after which research stagnated in the United States. Today, the ARE and the MSRE remain the only molten salt reactors ever operated.


title: Liquid fluoride thorium reactor

text: In a nuclear power reactor, there are two types of fuel. The first is fissile material, which splits when hit by neutrons, releasing a large amount of energy and also releasing two or three new neutrons. These can split more fissile material, resulting in a continued chain reaction. Examples of fissile fuels are U-233, U-235 and Pu-239. The second type of fuel is called fertile. Examples of fertile fuel are Th-232 (mined thorium) and U-238 (mined uranium). In order to become fissile these nuclides must first absorb a neutron that's been produced in the process of fission, to become Th-233 and U-239 respectively. After two sequential beta decays, they transmute into fissile isotopes U-233 and Pu-239 respectively. This process is called breeding.


title: Liquid fluoride thorium reactor

text: All reactors breed some fuel this way, but today's solid fueled thermal reactors don't breed enough new fuel from the fertile to make up for the amount of fissile they consume. This is because today's reactors use the mined uranium-plutonium cycle in a moderated neutron spectrum. Such a fuel cycle, using slowed down neutrons, gives back less than 2 new neutrons from fissioning the bred plutonium. Since 1 neutron is required to sustain the fission reaction, this leaves a budget of less than 1 neutron per fission to breed new fuel. In addition, the materials in the core such as metals, moderators and fission products absorb some neutrons, leaving too few neutrons to breed enough fuel to continue operating the reactor. As a consequence they must add new fissile fuel periodically and swap out some of the old fuel to make room for the new fuel.


title: Liquid fluoride thorium reactor

text: In a reactor that breeds at least as much new fuel as it consumes, it is not necessary to add new fissile fuel. Only new fertile fuel is added, which breeds to fissile inside the reactor. In addition the fission products need to be removed. This type of reactor is called a breeder reactor. If it breeds just as much new fissile from fertile to keep operating indefinitely, it is called a break-even breeder or isobreeder. A LFTR is usually designed as a breeder reactor: thorium goes in, fission products come out.


title: Liquid fluoride thorium reactor

text: Reactors that use the uranium-plutonium fuel cycle require fast reactors to sustain breeding, because only with fast moving neutrons does the fission process provide more than 2 neutrons per fission. With thorium, it is possible to breed using a thermal reactor. This was proven to work in the Shippingport Atomic Power Station, whose final fuel load bred slightly more fissile from thorium than it consumed, despite being a fairly standard light water reactor. Thermal reactors require less of the expensive fissile fuel to start, but are more sensitive to fission products left in the core.


title: Liquid fluoride thorium reactor

text: There are two ways to configure a breeder reactor to do the required breeding. One can place the fertile and fissile fuel together, so breeding and splitting occurs in the same place. Alternatively, fissile and fertile can be separated. The latter is known as core-and-blanket, because a fissile core produces the heat and neutrons while a separate blanket does all the breeding.


title: Liquid fluoride thorium reactor

text: Oak Ridge investigated both ways to make a breeder for their molten salt breeder reactor. Because the fuel is liquid, they are called the "single fluid" and "two fluid" thorium thermal breeder molten salt reactors.


title: Liquid fluoride thorium reactor

text: The one-fluid design includes a large reactor vessel filled with fluoride salt containing thorium and uranium. Graphite rods immersed in the salt function as a moderator and to guide the flow of salt. In the ORNL MSBR (molten salt breeder reactor) design a reduced amount of graphite near the edge of the reactor core would make the outer region under-moderated, and increased the capture of neutrons there by the thorium. With this arrangement, most of the neutrons were generated at some distance from the reactor boundary, and reduced the neutron leakage to an acceptable level. Still, a single fluid design needs a considerable size to permit breeding.


title: Liquid fluoride thorium reactor

text: In a breeder configuration, extensive fuel processing was specified to remove fission products from the fuel salt.


title: Liquid fluoride thorium reactor

text: In a converter configuration fuel processing requirement was simplified to reduce plant cost. The trade-off was the requirement of periodic uranium refueling.


title: Liquid fluoride thorium reactor

text: The MSRE was a core region only prototype reactor. The MSRE provided valuable long-term operating experience. According to estimates of Japanese scientists, a single fluid LFTR program could be achieved through a relatively modest investment of roughly 300–400 million dollars over 5–10 years to fund research to fill minor technical gaps and build a small reactor prototype comparable to the MSRE.


title: Liquid fluoride thorium reactor

text: The "two fluid" reactor has a high-neutron-density core that burns uranium-233 from the thorium fuel cycle. A separate blanket of thorium salt absorbs neutrons and slowly converts its thorium to protactinium-233. Protactinium-233 can be left in the blanket region where neutron flux is lower, so that it slowly decays to U-233 fissile fuel, rather than capture neutrons. This bred fissile U-233 can be recovered by injecting additional fluorine to create uranium hexafluoride, a gas which can be captured as it comes out of solution. Once reduced again to uranium tetrafluoride, a solid, it can be mixed into the core salt medium to fission. The core's salt is also purified, first by fluorination to remove uranium, then vacuum distillation to remove and reuse the carrier salts. The still bottoms left after the distillation are the fission products waste of a LFTR.


title: Liquid fluoride thorium reactor

text: One weakness of the two-fluid design is the necessity of periodically replacing the core-blanket barrier due to fast neutron damage. ORNL chose graphite for its barrier material because of its low neutron absorption, compatibility with the molten salts, high temperature resistance, and sufficient strength and integrity to separate the fuel and blanket salts. The effect of neutron radiation on graphite is to slowly shrink and then swell it, causing an increase in porosity and a deterioration in physical properties. Graphite pipes would change length, and may crack and leak.


title: Liquid fluoride thorium reactor

text: Another weakness of the two-fluid design is its complex plumbing. ORNL thought a complex interleaving of core and blanket tubes was necessary to achieve a high power level with acceptably low power density. ORNL chose not to pursue the two-fluid design, and no examples of the two-fluid reactor were ever constructed.


title: Liquid fluoride thorium reactor

text: However, more recent research has questioned the need for ORNL's complex interleaving graphite tubing, suggesting a simple elongated tube-in-shell reactor that would allow high power output without complex tubing, accommodate thermal expansion, and permit tube replacement. Additionally, graphite can be replaced with high molybdenum alloys, which are used in fusion experiments and have greater tolerance to neutron damage.


title: Liquid fluoride thorium reactor

text: A two fluid reactor that has thorium in the fuel salt is sometimes called a "one and a half fluid" reactor, or 1.5 fluid reactor. This is a hybrid, with some of the advantages and disadvantages of both 1 fluid and 2 fluid reactors. Like the 1 fluid reactor, it has thorium in the fuel salt, which complicates the fuel processing. And yet, like the 2 fluid reactor, it can use a highly effective separate blanket to absorb neutrons that leak from the core. The added disadvantage of keeping the fluids separate using a barrier remains, but with thorium present in the fuel salt there are fewer neutrons that must pass through this barrier into the blanket fluid. This results in less damage to the barrier. Any leak in the barrier would also be of lower consequence, as the processing system must already deal with thorium in the core.


title: Liquid fluoride thorium reactor

text: The main design question when deciding between a one and a half or two fluid LFTR is whether a more complicated reprocessing or a more demanding structural barrier will be easier to solve.


title: Liquid fluoride thorium reactor

text: An LFTR with a high operating temperature of 700 degrees Celsius can operate at a thermal efficiency in converting heat to electricity of 45%. This is higher than today's light water reactors (LWRs) that are at 32–36% thermal to electrical efficiency.


title: Liquid fluoride thorium reactor

text: In addition to electricity generation, concentrated thermal energy from the high-temperature LFTR can be used as high-grade industrial process heat for many uses, such as ammonia production with the Haber process or thermal Hydrogen production by water splitting, eliminating the efficiency loss of first converting to electricity.


title: Liquid fluoride thorium reactor

text: The Rankine cycle is the most basic thermodynamic power cycle. The simplest cycle consists of a steam generator, a turbine, a condenser, and a pump. The working fluid is usually water. A Rankine power conversion system coupled to a LFTR could take advantage of increased steam temperature to improve its thermal efficiency. The subcritical Rankine steam cycle is currently used in commercial power plants, with the newest plants utilizing the higher temperature, higher pressure, supercritical Rankine steam cycles. The work of ORNL from the 1960s and 1970s on the MSBR assumed the use of a standard supercritical steam turbine with an efficiency of 44%, and had done considerable design work on developing molten fluoride salt – steam generators.


title: Liquid fluoride thorium reactor

text: The Brayton cycle generator has a much smaller footprint than the Rankine cycle, lower cost and higher thermal efficiency, but requires higher operating temperatures. It is therefore particularly suitable for use with a LFTR. The working gas can be helium, nitrogen, or carbon dioxide. The low-pressure warm gas is cooled in an ambient cooler. The low-pressure cold gas is compressed to the high-pressure of the system. The high-pressure working gas is expanded in a turbine to produce power. Often the turbine and the compressor are mechanically connected through a single shaft. High pressure Brayton cycles are expected to have a smaller generator footprint compared to lower pressure Rankine cycles. A Brayton cycle heat engine can operate at lower pressure with wider diameter piping. The world's first commercial Brayton cycle solar power module (100 kW) was built and demonstrated in Israel's Arava Desert in 2009.


title: Liquid fluoride thorium reactor

text: Fission products left in the reactor absorb neutrons and thus reduce neutron economy. This is especially important in the thorium fuel cycle with few spare neutrons and a thermal neutron spectrum, where absorption is strong.


title: Liquid fluoride thorium reactor

text: Removal of fission products is similar to reprocessing of solid fuel elements; by chemical or physical means, the valuable fissile fuel is separated from the waste fission products. Ideally the fertile fuel (thorium or U-238) and other fuel components (e.g. carrier salt or fuel cladding in solid fuels) can also be reused for new fuel. However, for economic reasons they may also end up in the waste.


title: Liquid fluoride thorium reactor

text: On site processing is planned to work continuously, cleaning a small fraction of the salt every day and sending it back to the reactor. There is no need to make the fuel salt very clean; the purpose is to keep the concentration of fission products and other impurities (e.g. oxygen) low enough. The concentrations of some of the rare earth elements must be especially kept low, as they have a large absorption cross section. Some other elements with a small cross section like Cs or Zr may accumulate over years of operation before they are removed.


title: Liquid fluoride thorium reactor

text: As the fuel of a LFTR is a molten salt mixture, it is attractive to use pyroprocessing, high temperature methods working directly with the hot molten salt. Pyroprocessing does not use radiation sensitive solvents and is not easily disturbed by decay heat. It can be used on highly radioactive fuel directly from the reactor.


title: Liquid fluoride thorium reactor

text: Having the chemical separation on site, close to the reactor avoids transport and keeps the total inventory of the fuel cycle low. Ideally everything except new fuel (thorium) and waste (fission products) stays inside the plant.


title: Liquid fluoride thorium reactor

text: One potential advantage of a liquid fuel is that it not only facilitates separating fission-products from the fuel, but also isolating individual fission products from one another, which is lucrative for isotopes that are scarce and in high-demand for various industrial (radiation sources for testing welds via radiography), agricultural (sterilizing produce via irradiation), and medical uses (Molybdenum-99 which decays into Technetium-99m, a valuable radiolabel dye for marking cancerous cells in medical scans).


title: Liquid fluoride thorium reactor

text: The more noble metals (Pd, Ru, Ag, Mo, Nb, Sb, Tc) do not form fluorides in the normal salt, but instead fine colloidal metallic particles. They can plate out on metal surfaces like the heat exchanger, or preferably on high surface area filters which are easier to replace. Still, there is some uncertainty where they end up, as the MSRE only provided a relatively short operating experience and independent laboratory experiments are difficult.


title: Liquid fluoride thorium reactor

text: Gases like Xe and Kr come out easily with a sparge of helium. In addition, some of the "noble" metals are removed as an aerosol. The quick removal of Xe-135 is particularly important, as it is a very strong neutron poison and makes reactor control more difficult if unremoved; this also improves neutron economy. The gas (mainly He, Xe and Kr) is held for about 2 days until almost all Xe-135 and other short lived isotopes have decayed. Most of the gas can then be recycled. After an additional hold up of several months, radioactivity is low enough to separate the gas at low temperatures into helium (for reuse), xenon (for sale) and krypton, which needs storage (e.g. in compressed form) for an extended time (several decades) to wait for the decay of Kr-85.


title: Liquid fluoride thorium reactor

text: Compared to classical PUREX reprocessing, pyroprocessing can be more compact and produce less secondary waste. The pyroprocesses of the LFTR salt already starts with a suitable liquid form, so it may be less expensive than using solid oxide fuels.


title: Liquid fluoride thorium reactor

text: However, because no complete molten salt reprocessing plant has been built, all testing has been limited to the laboratory, and with only a few elements. There is still more research and development needed to improve separation and make reprocessing more economically viable.


title: Liquid fluoride thorium reactor

text: Uranium and some other elements can be removed from the salt by a process called fluorine volatility: A sparge of fluorine removes volatile high-valence fluorides as a gas. This is mainly uranium hexafluoride, containing the uranium-233 fuel, but also neptunium hexafluoride, technetium hexafluoride and selenium hexafluoride, as well as fluorides of some other fission products (e.g. iodine, molybdenum and tellurium). The volatile fluorides can be further separated by adsorption and distillation. Handling uranium hexafluoride is well established in enrichment. The higher valence fluorides are quite corrosive at high temperatures and require more resistant materials than Hastelloy. One suggestion in the MSBR program at ORNL was using solidified salt as a protective layer. At the MSRE reactor fluorine volatility was used to remove uranium from the fuel salt. Also for use with solid fuel elements fluorine volatility is quite well developed and tested.


title: Liquid fluoride thorium reactor

text: Another simple method, tested during the MSRE program, is high temperature vacuum distillation. The lower boiling point fluorides like uranium tetrafluoride and the LiF and BeF carrier salt can be removed by distillation. Under vacuum the temperature can be lower than the ambient pressure boiling point. So a temperature of about 1000 °C is sufficient to recover most of the FLiBe carrier salt. However, while possible in principle, separation of thorium fluoride from the even higher boiling point lanthanide fluorides would require very high temperatures and new materials.


title: Liquid fluoride thorium reactor

text: The chemical separation for the 2-fluid designs, using uranium as a fissile fuel can work with these two relatively simple processes:


title: Liquid fluoride thorium reactor

text: Uranium from the blanket salt can be removed by fluorine volatility, and transferred to the core salt. To remove the fissile products from the core salt, first the uranium is removed via fluorine volatility. Then the carrier salt can be recovered by high temperature distillation. The fluorides with a high boiling point, including the lanthanides stay behind as waste.


title: Liquid fluoride thorium reactor

text: The early Oak Ridge's chemistry designs were not concerned with proliferation and aimed for fast breeding. They planned to separate and store protactinium-233, so it could decay to uranium-233 without being destroyed by neutron capture in the reactor. With a half-life of 27 days, 2 months of storage would assure that 75% of the Pa decays to U fuel. The protactinium removal step is not required per se for a LFTR. Alternate solutions are operating at a lower power density and thus a larger fissile inventory (for 1 or 1.5 fluid) or a larger blanket (for 2 fluid). Also a harder neutron spectrum helps to achieve acceptable breeding without protactinium isolation.


title: Liquid fluoride thorium reactor

text: If Pa separation is specified, this must be done quite often (for example, every 10 days) to be effective. For a 1 GW, 1-fluid plant this means about 10% of the fuel or about 15 t of fuel salt need to go through reprocessing every day. This is only feasible if the costs are much lower than current costs for reprocessing solid fuel.


title: Liquid fluoride thorium reactor

text: Newer designs usually avoid the Pa removal and send less salt to reprocessing, which reduces the required size and costs for the chemical separation. It also avoids proliferation concerns due to high purity U-233 that might be available from the decay of the chemical separated Pa.


title: Liquid fluoride thorium reactor

text: Separation is more difficult if the fission products are mixed with thorium, because thorium, plutonium and the lanthanides (rare earth elements) are chemically similar. One process suggested for both separation of protactinium and the removal of the lanthanides is the contact with molten bismuth. In a redox-reaction some metals can be transferred to the bismuth melt in exchange for lithium added to the bismuth melt. At low lithium concentrations U, Pu and Pa move to the bismuth melt. At more reducing conditions (more lithium in the bismuth melt) the lanthanides and thorium transfer to the bismuth melt too. The fission products are then removed from the bismuth alloy in a separate step, e.g. by contact to a LiCl melt. However this method is far less developed. A similar method may also be possible with other liquid metals like aluminum.


title: Liquid fluoride thorium reactor

text: Thorium-fueled molten salt reactors offer many potential advantages compared to conventional solid uranium fueled light water reactors:


title: Liquid fluoride thorium reactor

text: LFTRs are quite unlike today's operating commercial power reactors. These differences create design difficulties and trade-offs:


title: Liquid fluoride thorium reactor

text: The FUJI MSR was a design for a 100 to 200 MWe molten-salt-fueled thorium fuel cycle thermal breeder reactor, using technology similar to the Oak Ridge National Laboratory Reactor Experiment. It was being developed by a consortium including members from Japan, the United States, and Russia. As a breeder reactor, it converts thorium into nuclear fuels. An industry group presented updated plans about FUJI MSR in July 2010. They projected a cost of 2.85 cents per kilowatt hour.


title: Liquid fluoride thorium reactor

text: The IThEMS consortium planned to first build a much smaller MiniFUJI 10 MWe reactor of the same design once it had secured an additional $300 million in funding, but IThEMS closed in 2011 after it was unable to secure adequate funding. A new company, Thorium Tech Solution (TTS), was founded in 2011 by Kazuo Furukawa, the chief scientist from IThEMS, and Masaaki Furukawa. TTS acquired the FUJI design and some related patents.


title: Liquid fluoride thorium reactor

text: The People's Republic of China has initiated a research and development project in thorium molten-salt reactor technology. It was formally announced at the Chinese Academy of Sciences (CAS) annual conference in January 2011. Its ultimate target is to investigate and develop a thorium based molten salt nuclear system in about 20 years. An expected intermediate outcome of the TMSR research program is to build a 2 MW pebble bed fluoride salt cooled research reactor in 2015, and a 2 MW molten salt fueled research reactor in 2017. This would be followed by a 10 MW demonstrator reactor and a 100 MW pilot reactors. The project is spearheaded by Jiang Mianheng, with a start-up budget of $350 million, and has already recruited 140 PhD scientists, working full-time on thorium molten salt reactor research at the Shanghai Institute of Applied Physics. An expansion of staffing has increased to 700 as of 2015. As of 2016, their plan is for a 10MW pilot LFTR is expected to be made operational in 2025, with a 100MW version set to follow in 2035.


title: Liquid fluoride thorium reactor

text: At the end of August 2021, the Shanghai Institute of Applied Physics (SINAP) completed the construction of a 2MW (thermal) experimental thorium molten salt reactor in Wuwei, Gansu, known as the TMSR-LF1.


title: Liquid fluoride thorium reactor

text: Kirk Sorensen, former NASA scientist and Chief Nuclear Technologist at Teledyne Brown Engineering, has been a long-time promoter of thorium fuel cycle and particularly liquid fluoride thorium reactors. He first researched thorium reactors while working at NASA, while evaluating power plant designs suitable for lunar colonies. Material about this fuel cycle was surprisingly hard to find, so in 2006 Sorensen started "energyfromthorium.com", a document repository, forum, and blog to promote this technology. In 2006, Sorensen coined the "liquid fluoride thorium reactor" and "LFTR" nomenclature to describe a subset of molten salt reactor designs based on liquid fluoride-salt fuels with breeding of thorium into uranium-233 in the thermal spectrum. In 2011, Sorensen founded Flibe Energy, a company that initially intends to develop 20–50 MW LFTR small modular reactor designs to power military bases; Sorensen noted that it is easier to promote novel military designs than civilian power station designs in the context of the modern US nuclear regulatory and political environment. An independent technology assessment coordinated with EPRI and Southern Company represents the most detailed information so far publicly available about Flibe Energy's proposed LFTR design.


title: Liquid fluoride thorium reactor

text: Thorium Energy Generation Pty. Limited (TEG) was an Australian research and development company dedicated to the worldwide commercial development of LFTR reactors, as well as thorium accelerator-driven systems. As of June 2015, TEG had ceased operations.


title: Liquid fluoride thorium reactor

text: The Alvin Weinberg Foundation was a British charity founded in 2011, dedicated to raising awareness about the potential of thorium energy and LFTR. It was formally launched at the House of Lords on 8 September 2011. It is named after American nuclear physicist Alvin M. Weinberg, who pioneered the thorium molten salt reactor research.


title: Liquid fluoride thorium reactor

text: ThorCon nuclear reactor is a proposed floating molten salt reactor, by the US-based Thorcon company. The two-reactor unit is designed to be manufactured on an assembly line in a shipyard, and to be delivered via barge to any ocean or major waterway shoreline. The reactors are to be delivered as a sealed unit and never opened on site. All reactor maintenance and fuel processing is done at an off-site location.


title: Liquid fluoride thorium reactor

text: On 5 September 2017, The Dutch Nuclear Research and Consultancy Group announced that research on the irradiation of molten thorium fluoride salts inside the Petten high-flux reactor was underway.


title: Names of the United States

text: Several names of the United States of America are in common use. Formal alternatives to the full name include the "United States", "America", as well as the initialisms "U.S." and the "U.S.A."; colloquial names include "the States" and the "U.S. of A."


title: Names of the United States

text: It is generally accepted that the name "America" derives from the Italian explorer Amerigo Vespucci. The term dates back to 1507, when it appeared on a world map created by the German cartographer Martin Waldseemüller, in honor of Vespucci, applied to the land that is now Brazil. The full name "United States of America" was first used during the American Revolutionary War, though its precise origin is a matter of contention. The newly formed union was first known as the "United Colonies", and the earliest known usage of the modern full name dates from a letter written between two military officers. The Articles of Confederation, prepared by John Dickinson, and the Declaration of Independence, drafted by Thomas Jefferson, both contain the phrase "United States of America." The name was officially adopted by the second Continental Congress on .


title: Names of the United States

text: The earliest known use of the name "America" dates to 1505, when German poet Matthias Ringmann used it in a poem about the New World. The word is a Latinized form of the first name of Italian explorer Amerigo Vespucci, who first proposed that the West Indies discovered by Christopher Columbus in 1492 were part of a previously unknown landmass, rather than the eastern limit of Asia. On , the map "Universalis Cosmographia", created by German cartographer Martin Waldseemüller, was published alongside this poem. The map uses the label "America" for what is now known as South America. In 1538, the Flemish cartographer Gerardus Mercator used the name "America" on his own world map, applying it to the entire Western Hemisphere.


title: Names of the United States

text: Alternative theories suggest that "America" derives from the Amerrisque Mountains of Nicaragua, or from the surname of wealthy Anglo-Welsh merchant Richard Amerike.


title: Names of the United States

text: The first documentary evidence of the phrase "United States of America" dates from a , letter written by Stephen Moylan, Esquire, to George Washington's aide-de-camp Joseph Reed. Moylan was fulfilling Reed's role during the latter's absence. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the Revolutionary War effort. The first known publication of the phrase "United States of America" was in an anonymous essay in "The Virginia Gazette" newspaper in Williamsburg, Virginia, on . It is commonly mistaken that Thomas Paine coined the term in his pamphlet "Common Sense", published in January 1776, but he never used the final form.


title: Names of the United States

text: The second draft of the Articles of Confederation, prepared by John Dickinson and completed no later than , declared "The name of this Confederation shall be the 'United States of America'." The final version of the Articles, sent to the states for ratification in late 1777, stated that "The Stile of this Confederacy shall be 'The United States of America'." In June 1776, Thomas Jefferson wrote "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence. This draft of the document did not surface until , and it is unclear whether it was written before or after Dickinson used the term in his June 17 draft of the Articles of Confederation. In any case, the Declaration of Independence was the first official document to use the nation's new title.


title: Names of the United States

text: In the early days of the American Revolution, the colonies as a unit were most commonly referred to as the "United Colonies". For example, president of the Continental Congress Richard Henry Lee wrote in a June 7, 1776 resolution: "These United Colonies are, and of right, ought to be, free and independent States." Before 1776, names for the colonies varied significantly; they included "Twelve United English Colonies of North America", "United Colonies of North America", and others. On September 9, 1776, the Second Continental Congress officially changed the nation's name to the "United States of America".


title: Names of the United States

text: In the first few years of the United States, however, there remained some discrepancies of usage. In the Treaty of Alliance (1778) with France, the term "United States of North America" was used. In accordance with this usage, when the Congress was drawing bills of exchange for French commissioners on May 19, 1778, they decided to use this term. President of the Continental Congress Henry Laurens even wrote that "Congress have adopted the Stile of the Treaties of Paris, 'the United States of North America'." Congress, however, reconsidered this change on July 11, 1778 and resolved to drop "North" from the bills of exchange, making them consistent with the name adopted in 1776.


title: Names of the United States

text: Since the Articles of Confederation, the concept of a Perpetual Union between the states has existed, and "Union" has become synonymous with "United States". This usage was especially prevalent during the Civil War, when it referred specifically to the loyalist northern states which remained part of the federal union.


title: Names of the United States

text: The term "America" was seldom used in the United States before the 1890s, and rarely used by presidents before Theodore Roosevelt. It does not appear in patriotic songs composed during the eighteenth and nineteenth centuries, including "The Star-Spangled Banner", "My Country, 'Tis of Thee", and the "Battle Hymn of the Republic", although it is common in 20th-century songs like "God Bless America". The name "Columbia", popular in American poetry and songs of the late 18th century, derives its origin from Christopher Columbus. Many landmarks and institutions in the Western Hemisphere bear his name, including the country of Colombia and the District of Columbia.


title: Names of the United States

text: Circa 1810, the term Uncle Sam was "a cant term in the army for the United States," according to a 1810 edition "Niles' Weekly Register." Uncle Sam is now known as a national personification of the United States.


title: Names of the United States

text: The phrase "United States" was originally plural, a description of a collection of independent states—e.g., "the United States are"—including in the Thirteenth Amendment to the United States Constitution, ratified in 1865. The singular form became popular after the end of the Civil War, and is now standard. However, the plural form is retained in the idiom "these United States". The difference is more significant than usage; it is a difference between a collection of states and a unit.


title: Names of the United States

text: The transition from plural to singular was gradual. In a May 4, 1901, column in the "New York Times" titled "ARE OR IS? Whether a Plural or Singular Verb Goes With the Words United States", former Secretary of State John W. Foster noted that early statesmen such as Alexander Hamilton and Daniel Webster had used the singular form, as well as the Treaty of Paris (1898) and Hay–Pauncefote Treaty of 1900; conversely, most Supreme Court decisions still used the plural form. He concludes that "since the civil war the tendency has been towards [singular] use." Mark Liberman of the University of Pennsylvania found that, in the corpus of Supreme Court opinions, the transition to singular usage occurred in the early 1900s. Among English-language books, the transition happened earlier, around 1880.


title: Names of the United States

text: The name "United States" is unambiguous; "United States of America" may be used in titles or when extra formality is desired. However, "United States" and "U.S." may be used adjectivally, while the full name cannot. English usage of "America" rarely refers to topics unrelated to the United States, despite the usage of "Americas" as the totality of North and South America. Colloquial names include the "U.S. of A." and, internationally, "the States". Even more informal names include "Murica" and "Merica", which imply a jocular and sometimes derogatory tone; these names come from stereotypical white southerners' pronunciation of the word.


title: Names of the United States

text: The official U.S. Government Publishing Office Style Manual prescribes specific usages for "U.S." and "United States". In treaties, congressional bills, etc., "United States" is always used. In a sentence containing the name of another country, "United States" must be used. Otherwise, "U.S." is used preceding a government organization or as an adjective, but "United States" is used as an adjective preceding non-governmental organizations (e.g. United States Steel Corporation).


title: Names of the United States

text: Style guides conflict over how various names for the United States should be used. The "Chicago Manual of Style", until the 17th edition, required "US" and "U.S." to be used as an adjective; it now permits the usage of both as a noun, though "United States" is still preferred in this case. The "Associated Press Stylebook" permits the usage of "US" and "U.S." as both adjectives and nouns, though "US" (without the periods) is only allowed in headlines. "APA Style", in contrast, only allows "U.S." to be used as an adjective, and disallows "US".


title: Names of the United States

text: In Spanish, the U.S. is known as "Estados Unidos", literally "United States." The Americas are known simply as "América". Spanish uses "estadounidense" and "americano" for the adjectival form, with the latter being mostly proscribed. In Chinese, the U.S. is known as 美国 (, traditional: 美國). Literally "beautiful country," it in fact comes from the second character of the transliteration of America as "亚美利加" (, traditional: 亞美利加). The Americas are known as 美洲 (), with the same etymology. In Japanese, the U.S. is known as アメリカ (Hepburn: "amerika") and 米国 (Hepburn: beikoku), borrowing from Chinese. In Hindi, the U.S. is transliterated to अमेरिका ("amerika"). In Esperanto, the United States of America is known as "Usono", borrowing from English "Usonia". In Burmese, the United States of America is known as အမေရိကန်ပြည်ထောင်စု ("amerikan pyedaungsu"), literally "American Union." In Kannada, the United States is known as "ಅಮೇರಿಕ ಸಂಯುಕ್ತ ಸಂಸ್ಥಾನ", literally "America's Union of States."


title: Jan Nisar Akhtar

text: Jan Nisar Akhtar (18 February 1914 – 19 August 1976) was an Indian poet of Urdu ghazals and nazms, and a part of the Progressive Writers' Movement, who was also a lyricist for Bollywood.


title: Jan Nisar Akhtar

text: He was son of Muztar Khairabadi and great grandson of Fazl-e-Haq Khairabadi his career spanned four decades during which he worked with music composers including C. Ramchandra, O.P. Nayyar, Datta Naik also credited as N. Datta and Khayyam and wrote 151 songs. Notable among them were songs from his breakthrough film, AR Kardar's "Yasmin" (1955), "Aankhon hi Aankhon Mein" in Guru Dutt's "CID" (1956), "Yeh dil aur unki nigahon ke saaye" in Prem Parbat (1974) and "Aaja re" in "Noorie" (1979) and his last song, "Ae Dil-e-naadaan", in Kamal Amrohi's "Razia Sultan" (1983).


title: Jan Nisar Akhtar

text: His poetry works include "Nazr-e-Butaan", "Salaasil", "Javidaan", "Pichali Pehar", "Ghar Angan" and "Khaak-e-dil". The latter ("The Ashes of Heart") was a poetry collection for which he was awarded the 1976 Sahitya Akademi Award in Urdu by Sahitya Akademi, India's National Academy of Letters.


title: Jan Nisar Akhtar

text: Jan Nisar passed his matriculation from Victoria Collegiate High School, Gwalior, and in 1930 joined Aligarh Muslim University, from where he gained his B.A. Honours and M.A. degrees. He started his doctoral work, but had to return to Gwalior due to family conditions.


title: Jan Nisar Akhtar

text: In 1949, he resigned from his job, moved to Bombay to write lyrics for Urdu/Hindi movies besides ghazals and nazms for general publication. Once in Bombay, he came in touch with other progressive writers, like Mulk Raj Anand, Krishan Chander, Rajinder Singh Bedi and Ismat Chugtai, who often met at Bombay's Silver Fish Restaurant, and subsequently came to be known as 'Bombay Group of Writers'. Success came his way quite late as a film lyricist, till then he was supported by his wife who had stayed back in Bhopal, though she died prematurely of cancer in 1953. Finally he had a career breakthrough, with "Yasmeen" (1955), with music by C. Ramchandra. His association with Madan Mohan, the music director resulted in many memorable movie songs. Some of his notable lyrics were, " Meri Neendon Mein Tum" in "Naya Andaz" (1956) by Kishore Kumar, Shamshad Begum, "Garib Jan Key Hamko Naa Tum Daga Dena" sung by Mohd. Rafi in "Chhoo Mantar", the hit "Piya piya piya..." in "Baap Re Baap" (1955) music by O.P. Nayyar, " Aap Yun Faaslon Se" by Lata Mangeshkar in "Shankar Hussain" (1977).


title: Jan Nisar Akhtar

text: His poetry was secular and like many of progressive writers of his generation talked of freedom, dignity, economic exploitation and other issues gleaming of the leftist leanings. Even his romanticism which was amply displayed in his ghazals, was replete with references to household and family life. His notable books include "Nazr-e-Butaan", "Salaasil", "Javidaan", "Ghar Angan" and "Khaak-e-Dil" (all Urdu titles). One of his many famous couplets is :


title: Jan Nisar Akhtar

text: He wrote and produced a film, "Bahu Begum" (1967), starring Pradeep Kumar and Meena Kumari. During the period of four-year to his death he published three collections of his works most important of them being, "Khak-e-Dil" (The Ashes of Heart"), which has his representative poems from 1935 to 1970, and which won him the Sahitya Akademi Award (Urdu) in 1976. Jan Nisar was commissioned by the first Prime Minister of India, Jawaharlal Nehru to collate the best Hindustani poetry of last 300 years, and later the first edition of the book titled "Hindustan Hamara" (Our Hindustan) in two volumes was released by Indira Gandhi. It contained Urdu verses on a topics, ranging from love and praise for India and its history, to festivals like Holi and Diwali, on Indian rivers like the Ganges, Yamuna and the Himalayas.


title: Jan Nisar Akhtar

text: He died in Bombay on 19 August 1976, while he was still working on Kamal Amrohi's film, "Razia Sultan" (1983). He was nominated posthumously for 1980 Filmfare Best Lyricist Award for "Aaja Re Mere Dilbar" from the film, "Noorie".


title: Jan Nisar Akhtar

text: In 1943, he married Safia, sister of the poet Majaz. Safia worked as a school teacher at an Urdu-medium "madarsa" (Muslim school). She was meeting a practical necessity, to work outside her home, because Jan Nisar's income was at best sporadic, and it was necessary for her to work to support her children. Thus, when Jan Nisar moved to Mumbai to try his luck at earning a living as a film lyricist, Safia stayed back in Gwalior with their children, and wrote her absent husband a series of letters in Urdu. A collection of these letters, written between 1 October 1943 to 29 December 1953 penned, were first published in 1955 in two volumes under the title, "Harf-e-Aashna" and "Zer-e-Lab." Professor Asghar Wajahat, former Head of the Hindi Department, Jamia Millia Islamia, translated these letters into Hindi and this was published under the title "Tumhare Naam" in 2004.


title: Jan Nisar Akhtar

text: Safia Akhtar died of cancer on 17 January 1953, less than ten years after her wedding, and left behind two very small sons. Jan Nisar left the children in the care of relatives while he pursued his hobbies of writing poetry and hobnobbing with various luminaries and socialites in Mumbai. Three years after Safia's death, Jan Nisar got married again on 17 September 1956, to Khadija Talat. His children by Safia did not have a good relationship with their step-mother, and his relations with them was likewise dysfunctional.


title: After the Thrones

text: After the Thrones is an American live television aftershow that premiered on April 25, 2016, and ended on June 28, 2016. It was hosted by Andy Greenwald and Chris Ryan who discussed episodes of the HBO television series "Game of Thrones". The talk show was executive produced by Bill Simmons and Eric Weinberger. Greenwald and Ryan previously hosted a podcast version of the show titled "Watch the Thrones" on Simmons' Grantland website. A similar talk show called "Thronecast" aired on British channel Sky Atlantic, which also discussed episodes of "Game of Thrones".


title: After the Thrones

text: The talk show was made available to HBO and HBO Now subscribers, and airs on the Monday following each episode of "Game of Thrones". After the show's cancellation, Greenwald and Ryan, along with Simmons, made a similar live stream video podcast for distribution on Twitter called "Talk the Thrones". Although it covers the same subject matter, it is a different production.


title: After the Thrones

text: The series features hosts Andy Greenwald and Chris Ryan from the upcoming sports and pop culture website, "The Ringer" created by Bill Simmons, discussing episodes of the HBO fantasy drama "Game of Thrones". Following the success of similar shows such as "Talking Dead", which serves as a network sanctioned discussion of the show, HBO decided to introduce its own version of the format in which the hosts provide a "lively, humorous and sophisticated look" at the previous night's episode. The show airs on the stand-alone streaming service HBO Now on the Monday following each episode of the show's sixth season, which itself airs on Sundays. Greenwald and Ryan previously hosted a similar version of the show for Simmons' now-defunct sports and pop culture website Grantland, titled "Watch the Thrones", in a podcast format. Previous "Watch the Thrones" guests Mallory Rubin and Jason Concepcion are also part of the show.


title: After the Thrones

text: The series began on Monday, April 25, 2016, on HBO Now, HBO Go, HBO On Demand and HBO. The stated purpose of the show is to "recap the latest episode, explaining the who, what, when and where, exploring the complicated politics and history of "Thrones", and offering absurd and not-so-absurd theories about future episodes."


title: After the Thrones

text: For the seventh season of "Game of Thrones", the after show changed its name to Talk the Thrones and moved from HBO to the social media site Twitter, where it will stream live every week after an episode airs. Simmons said that "We love Game of Thrones and we love the way Twitter is thinking about content right now, so we jumped at the chance to blow out our Thrones show into an interactive multimedia experience — something that reacts immediately to what just happened, almost like a postgame show in sports - Nobody is equipped to do that better than Twitter. It's the natural evolution of what we had already established with Chris, Andy, Mallory and Jason."


title: After the Thrones

text: These episodes discuss season six of "Game of Thrones". Starting from the first episode, "The Red Woman".


title: Oregon City-class cruiser

text: The Oregon City class was a class of heavy cruisers of the United States Navy. Although it was intended to build ten, only four were completed – one of those as a command ship. The three ships completed as cruisers were in commission from 1946 to 1970.


title: Oregon City-class cruiser

text: The "Oregon City"-class cruisers were a modified version of the previous design; the main difference was a more compact pyramidal superstructure with single trunked funnel, intended to improve the arcs of fire of the anti-aircraft (AA) guns. The same type of modification also differentiated the and classes, and to a lesser degree the and classes of light cruisers.


title: Oregon City-class cruiser

text: Ten ships were authorized for the class with three being completed and the fourth suspended during construction. The final six ships were cancelled, five after being laid down. Construction on the incomplete fourth ship was resumed in 1948 and the ship served as a command ship . All three completed cruisers were commissioned in 1946. "Oregon City" was decommissioned after only 22 months of service, one of the shortest active careers of any World War II-era cruiser. "Albany" was later converted into a guided missile ship, becoming the lead ship of the and served until 1980. A similar conversion was planned for "Rochester" but was cancelled.


title: Aptera Motors

text: Aptera Motors (formerly Accelerated Composites) is an American startup high-efficiency car company based in Carlsbad, California.


title: Aptera Motors

text: In 2019, Aptera Motors was re-formed by the original founders, Chris Anthony and Steve Fambro, as Aptera Motors Corp. It used a crowdfunding campaign to restart development of what is touted as the most highly efficient road vehicle in the world.


title: Aptera Motors

text: The original Aptera Motors' design was a three-wheeled two-seat vehicle named the Aptera 2 Series. The marketed fuel efficiency of , when plugged in every , would have made it one of the most fuel-efficient passenger vehicles in the world.


title: Aptera Motors

text: As of 2019, the Aptera had been redesigned to be a pure battery-powered electric vehicle (BEV) using under 100Wh per mile on the EPA test cycle, with a marketed EPA test-cycle range of , with solar panels that could add up to 40 miles of range per day. This makes the Aptera the most efficient and the longest-range motor vehicle ever designed for mass production.


title: Aptera Motors

text: On December 4, 2020, the company revealed the new Aptera EV prototype, releasing model and option details with prices, and opened pre-orders. Within eight days they received deposits for over 3,000 Aptera vehicles, valued at over $100,000,000. Within 7 weeks the company received deposits for over $200,000,000 worth of vehicles.


title: Aptera Motors

text: In their December 2021 video update, the company revealed they had over 15,000 reservation holders, over 8,000 investors, had started construction in their newly acquired 80,000 square foot factory space, and were "confident we will be able to begin supplying vehicles in the later part of 2022."


title: Aptera Motors

text: A month later in January 2022 the San Diego Business Journal reported their reservations had grown to over 16,000, their employees had doubled to 60 and they were looking to hire 470 more by the end of the year. In October 2022 they announced the number of reservations had grown to over 35,000.


title: Aptera Motors

text: In May of 2022, Aptera Motors' released their 2021 Annual Report. In it they stated that have 103 full- and part-time employees and over 18,000 reservations for their solar electric vehicle. Also as of the end of 2021 they reported they had $23,259,441 in total assets (compared to $1,201,072 in 2020) and a net loss of $18.9 million in 2021 (compared to a loss of $4.2 million in 2020).


title: Aptera Motors

text: As of 2019, the first planned production Aptera is a two-seat, three-wheeled passenger battery electric vehicle (BEV). Its design includes two, 50 KW wheel hub motors with an EPA-test-cycle estimated range of over , from a 100 kWh battery pack.


title: Aptera Motors

text: This estimated range was achieved by using lightweight resin composite materials in a body with a unique aerodynamic design. The resulting vehicle is estimated to require less than 100 Wh of energy per mile, making it about 2.5 times as energy efficient as a Tesla Model 3, with half the Model 3's passenger capacity but more cargo space than the Model 3.


title: Aptera Motors

text: Embedded solar cells have been designed to contribute an estimated additional per day from sunlight under optimal conditions. Since most drivers drive less than 30 miles per day, many drivers would seldom or never have to charge. The Aptera was therefore promoted as the world's first "Never Charge" EV. The company's web site features a calculator to estimate how often their owners would need to charge an Aptera, based on where they live and how much they drive.


title: Aptera Motors

text: Multiple solar panel, motor, and battery configurations are planned, with estimated ranges from , initially priced from $25,900 to over $47,000.


title: Aptera Motors

text: Aptera Motors published on their WeFunder page an investor presentation, dated July, 2020, with a production plan projecting Aptera first availability in the 2nd quarter of 2021. On December 4, 2020, Aptera Motors revealed the first solar-powered Aptera prototype. On the same day, Chris Anthony wrote, "Delivery for early orders is end of 2021". On January 11, 2021, he added, "If we can raise funds effectively and COVID doesn't continue to be a significant impediment, we should be able to deliver 4 to 6 thousand units in 2022." However, in September Chris Anthony stated that COVID did cause delays getting parts for the prototypes and getting the prototypes built.


title: Aptera Motors

text: In January 2022, Pablo Ucar, Aptera's Vice President of Production and Procurement, was quoted saying "We’ll start by producing our first few hundred vehicles, our Paradigm Editions. As our supply chain becomes more established, we’ll ramp to 250 per month, and eventually reach our target of producing 40 vehicles per day.". The company's Frequently Asked Question page states first customer deliveries as happening in "late 2022" for the Paradigm Edition. In February 2022, Aptera updated most of the over 16,000 reservation holders to a delivery window of 2023–2024.


title: Aptera Motors

text: A webinar was hosted by Aptera Motors on June 14, 2022 in which they outlined the company's progress on some component systems as well as a revised interior and exterior design with slightly more interior room and efficiency. At this webinar the team announced completion of its third generation (Gamma) prototype design and is aiming to complete its build of the first Gamma prototype in about 4 to 6 weeks. After that, the fourth generation (Delta) pre-production prototype design "will take several more months" to complete. First customer delivery was still aiming for "the end of the year" (2022). Pre-orders surpassed 25,000 during the live streaming of the webinar. They plan to produce 1,000 vehicles in the first few months of production. As 40% of pre-orders are for the nominal 400-mile range (41 kWh battery) version, those first 1000 vehicles will all be that 400-mile range version. First deliveries will be made to customers near to their headquarters in San Diego County, California.


title: Aptera Motors

text: As of that September over 30,000 vehicles had been reserved, worth about a billion dollars in sales. At Aptera's Gamma prototype reveal on September 10, 2022, Chief Designer Jason Hill said he expected the production intent prototype named Delta to be completed in November. Anthony mentioned crash testing of the first production intent vehicles would likely be completed, and videos of the them released, in the second quarter of 2023, so first customer availability would be soon after that time.


title: Aptera Motors

text: Aptera Motors has stated in the timeline on its web site that it will begin design of a full-sized 6-passenger vehicle in the second half of 2020. However, in February 2020, the founders said their next vehicle will be a 4-wheeled, 5 passenger car. There has been no further production plans of 4 wheeled versions shared publicly.


title: Aptera Motors

text: The company was founded by Steve Fambro in 2006 and was originally named "Accelerated Composites"; Fambro had formerly worked at Illumina as an electrical engineer. Fambro hired Chris Anthony to be the COO shortly after founding the company.


title: Aptera Motors

text: In 2006, the company announced it had a three-wheeled car design that would get an estimated at and in March 2007, it showed a prototype called the typ-1 at the TED Conference. The typ-1 model had been classified as a motorcycle. By that time the company had changed its name to "Aptera", which is Greek for "wingless", a nod to their light-aircraft-inspired design and construction techniques. However, Aptera Motors maintains that "Aptera" translates to "wingless flight". Later that year, Aptera signed up to participate in the Progressive Insurance Automotive X Prize. It planned to offer an all-electric vehicle and a hybrid.


title: Aptera Motors

text: In 2008, Aptera Motors hired several industry veterans to oversee engineering and production as well as marketing, and raised $24 million from Google, Idealab, Esenjay, the Simons family, and the Beall Family Trust. When the company announced the funding, it said it would start to sell its car by the end of the year. Near the end of year, it hired Paul Wilbur as CEO, and Fambro stepped down as CEO and assumed the title of Chief Technical Officer. Shortly after Wilbur joined the company, it announced that the launch of the car would be delayed until 2009. By that time, it was calling the "typ-1" the "2e".


title: Aptera Motors

text: In March 2009, the U.S. government denied loans to Aptera Motors under the Advanced Technology Vehicles Manufacturing Loan Program, due to wording that limited loans to four-wheeled-vehicle research and production. After successfully lobbying to change the regulations, in October 2009, the company reapplied for a $184 million loan. In November 2009 the company laid off employees, and both Fambro and Anthony left the company.


title: Aptera Motors

text: The automotive X-prize competition was held in 2010 and Aptera's car entered but didn't finish the 50-lap trial, as its car overheated after 30 laps.


title: Aptera Motors

text: On August 12, 2011, Aptera Motors started to return deposits from customers. and in December 2011, it announced that it was going out of business because it was running out of money; it said that the Department of Energy had offered it a $150 million low interest loan conditioned on the company raising the same amount from the private sector, but the company was not able to raise the matching funds. A New York Times reporter contacted the DoE, which said that it had not committed to loaning the company any money. By that time, the company had abandoned the three-wheeled model and was working on a mid-sized four-wheeled four-door sedan. Also by the time, 60,000 people had expressed interest to the company in buying a 2e, and 2,000 of them had paid a $500 deposit.


title: Aptera Motors

text: In April 2012, the Chinese automaker Zhejiang Jonway Group purchased the intellectual property of Aptera from creditors, and in May, it announced that it would start manufacturing the 2e at its factory in Shanghai and intended to ship chassis to a small assembly plant, initially employing 15-20 people, that it would set up in Santa Rosa, with sales commencing in early 2013. Jonway was a major investor in Zap Jonway, which had been working on electric cars in Santa Rosa since the mid-1990s. The company originally was going to name the US company "Zaptera USA" and it displayed a prototype 2e next to a Zap Jonway car at the Beijing Motor Show; the close association with Zap was met with protest by electric-car enthusiasts and by May, the company said it would call the company Aptera USA and would keep it separate from Zap Jonway.


title: Aptera Motors

text: In June 2013, Zaptera USA said it would split into two companies: the existing Jonway-owned Zaptera USA, and an independent Aptera USA; Zaptera would make the all-electric 2e and Aptera would make a gasoline-powered version called the 2g. However, by mid-May the following year, those new Aptera companies had gone silent.


title: Aptera Motors

text: In 2019, Aptera Motors was re-formed under the leadership of the original founders, Chris Anthony and Steve Fambro, as Aptera Motors Corp. It then began a crowdfunding campaign to restart development and production of what is touted to be the most efficient road vehicle in the world.


title: Aptera Motors

text: In February 2020, the company announced it had raised enough funding to see the Aptera EV into production by the end of 2020. In a May 2020 update, the company announced it had increased its engineering team from 15 to 60 people worldwide, in 5 locations around the US and in 5 countries around the world. In December 2020, they revealed the first solar-powered Aptera prototype and started taking reservations for it.


title: Aptera Motors

text: In 2021 the company built 3 more engineering prototypes, revised the Aptera design to give it more interior room and an improved suspension, and raised over $39 million in funding. They also acquired 3 buildings in Carlsbad, CA, with a combined space of over 100,000 square feet. This space meets their needs for R&D space, for test vehicle building and for manufacturing space for up to 40 vehicles per day (10,000 vehicles per year).


title: Aptera Motors

text: Aptera Motors' vehicle design has undergone several design revisions, summarized here. The first two vehicles were intended as concept cars for soliciting investment money rather than production vehicles. The third vehicle, the Aptera 2e, was intended for production, but the funding required was not achieved.


title: Aptera Motors

text: Aptera's introductory press release stated their design would achieve 330 mpg, and included computer renderings of the proposed vehicle. The body shape was initially estimated to have a , and would have sported a diesel engine and a permanent magnet DC motor. The design also called for a CVT and ultracapacitors, and sell for under US$20,000.


title: Aptera Motors

text: The Mk-0 technology-demonstration vehicle was built to confirm the effectiveness of the design, and in the words of co-founder Chris Anthony, “just to show people that we weren't full of crap.” Due to its higher-than-expected drag coefficient of 0.11, it only achieved at . The target price was unchanged at “around $20,000.”


title: Aptera Motors

text: In September 2007, the Aptera Motors website was updated with information on the new Aptera design (dubbed the Aptera Typ-1), and the Mk-1 pre-production prototype was unveiled. The Mk-0 prototype was redesigned by Jason Hill, who worked on the Smart Fortwo and Porsche Carrera GT and engineered by Nathan Armstrong,


title: Aptera Motors

text: with a finished interior and new body styling. At this time, Aptera Motors started to take reservations from residents of California for its pilot models – then called the Typ-1e and Typ-1h. A gasoline engine was used, due to the way diesel emissions are calculated.


title: Aptera Motors

text: In late 2008, Aptera announced that the Aptera Typ-1 would receive several design changes and would be renamed the "Aptera 2e". Differences included front-wheel drive, the addition of side-view mirrors, a redesigned interior, and consolidating the rear-view cameras into a wide-angle “fin” on the roof.


title: Aptera Motors

text: The Aptera 2 Series was to be a two-seat, three-wheeled passenger vehicle. It was planned to be available in both all-electric (2e) and series hybrid (2h) configurations, at prices ranging from mid-twenty to mid-forty thousand dollars. By mid-2008, aerodynamic optimization using simulations and light-weight composite construction yielded a prototype which allegedly consumed only 80 Wh/mi (watt hours per mile) (50 Wh/km) at , less than half the energy needed to propel either the EV1 or any existing Tesla . The April 14, 2010 press release revised the design-intent vehicle-efficiency estimate to about 200 Wh/mi (125 Wh/km), range from a full 20 kWh battery pack, or around equivalent. On the hybrid vehicle, it led to projections of on gasoline alone, or if plugged in every . Since then, the vehicle underwent a series of redesigns, including the addition of side mirrors and expansion of the interior space, however, retaining its three-wheel configuration and its aerodynamic teardrop shape. At the Automotive X-Prize, the entered prototype had a tested efficiency of 200 MPGe.


title: Aptera Motors

text: Aptera Motors emphasized that safety was not traded off for efficiency, citing crash-test simulations and component-crush testing as indicating excellent survivability — on par with more conventional vehicles. The company folded before real-world crash test results were made.


title: Aptera Motors

text: The Aptera 2 Series featured optional roof-mounted solar panels for running a heat pump, always-on climate control, and keyless ignition and entry. An in-car touch-screen computer served as entertainment, navigation, and communication system. Side mirrors replaced rear-view cameras on the final prototypes, though one center-mounted camera remained.


title: Aptera Motors

text: By the time of the original company's liquidation in 2011, the company had abandoned development of the Aptera 2e and had started to design a 5-passenger, 4-wheeled EV sedan with a lightweight composite body and a projected 130-mile range. However, no body and only a few test mules for such a car were ever built.


title: Gravitational redshift

text: In physics and general relativity, gravitational redshift (known as Einstein shift in older literature) is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well (seem to) lose energy. This loss of energy corresponds to a decrease in the wave frequency and increase in the wavelength, known more generally as a "redshift". The opposite effect, in which photons (seem to) gain energy when travelling into a gravitational well, is known as a gravitational blueshift (a type of "blueshift"). The effect was first described by Einstein in 1907, eight years before his publication of the full theory of relativity.


title: Gravitational redshift

text: Gravitational redshift can be interpreted as a consequence of the equivalence principle (that gravity and acceleration are equivalent and the redshift is caused by the Doppler effect) or as a consequence of the mass-energy equivalence and conservation of energy ('falling' photons gain energy), though there are numerous subtleties that complicate a rigorous derivation. A gravitational redshift can also equivalently be interpreted as gravitational time dilation at the source of the radiation: if two oscillators (attached to transmitters producing electromagnetic radiation) are operating at different gravitational potentials, the oscillator at the higher gravitational potential (farther from the attracting body) will seem to ‘tick’ faster; that is, when observed from the same location, it will have a higher measured frequency than the oscillator at the lower gravitational potential (closer to the attracting body).


title: Gravitational redshift

text: To first approximation, gravitational redshift is proportional to the difference in gravitational potential divided by the speed of light squared, formula_1, thus resulting in a very small effect. Light escaping from the surface of the sun was predicted by Einstein in 1911 to be redshifted by roughly 2 ppm or 2 × 10. Navigational signals from GPS satellites orbiting at 20,000 km altitude are perceived blueshifted by approximately 0.5 ppb or 5 × 10, corresponding to a (negligible) increase of less than 1 Hz in the frequency of a 1.5 GHz GPS radio signal (however, the accompanying gravitational time dilation affecting the atomic clock in the satellite "is" crucially important for accurate navigation). On the surface of the Earth the gravitational potential is proportional to height, formula_2, and the corresponding redshift is roughly 10 (0.1 part per quadrillion) per meter of change in elevation and/or altitude.


title: Gravitational redshift

text: In astronomy, the magnitude of a gravitational redshift is often expressed as the velocity that would create an equivalent shift through the relativistic Doppler effect. In such units, the 2 ppm sunlight redshift corresponds to a 633 m/s receding velocity, roughly of the same magnitude as convective motions in the sun, thus complicating the measurement. The GPS satellite gravitational blueshift velocity equivalent is less than 0.2 m/s, which is negligible compared to the actual Doppler shift resulting from its orbital velocity. In astronomical objects with strong gravitational fields the redshift can be much greater; for example, light from the surface of a white dwarf is gravitationally redshifted on average by around 50 km/s/c (around 170 ppm).


title: Gravitational redshift

text: Observing the gravitational redshift in the solar system is one of the classical tests of general relativity. Measuring the gravitational redshift to high precision with atomic clocks can serve as a test of Lorentz symmetry and guide searches for dark matter.


title: Gravitational redshift

text: Einstein's theory of general relativity incorporates the equivalence principle, which can be stated in various different ways. One such statement is that gravitational effects are locally undetectable for a free-falling observer. Therefore, in a laboratory experiment at the surface of the earth, all gravitational effects should be equivalent to the effects that would have been observed if the laboratory had been accelerating through outer space at "g". One consequence is a gravitational Doppler effect. If a light pulse is emitted at the floor of the laboratory, then a free-falling observer says that by the time it reaches the ceiling, the ceiling has accelerated away from it, and therefore when observed by a detector fixed to the ceiling, it will be observed to have been Doppler shifted toward the red end of the spectrum. This shift, which the free-falling observer considers to be a kinematical Doppler shift, is thought of by the laboratory observer as a gravitational redshift. Such an effect was verified in the 1959 Pound–Rebka experiment. In a case such as this, where the gravitational field is uniform, the change in wavelength is given by


title: Gravitational redshift

text: where formula_4 is the change in height. Since this prediction arises directly from the equivalence principle, it does not require any of the mathematical apparatus of general relativity, and its verification does not specifically support general relativity over any other theory that incorporates the equivalence principle.


title: Gravitational redshift

text: On Earth's surface (or in a spaceship accelerating at 1g), the gravitational redshift is approximately 1.1 × 10, the equivalent of a 3.3 × 10 m/s Doppler shift, for every meter of height differential.


title: Gravitational redshift

text: When the field is not uniform, the simplest and most useful case to consider is that of a spherically symmetric field. By Birkhoff's theorem, such a field is described in general relativity by the Schwarzschild metric, formula_5, where formula_6 is the clock time of an observer at distance "R" from the center, formula_7 is the time measured by an observer at infinity, formula_8 is the Schwarzschild radius formula_9, "..." represents terms that vanish if the observer is at rest, formula_10 is Newton's gravitational constant, formula_11 the mass of the gravitating body, and formula_12 the speed of light. The result is that frequencies and wavelengths are shifted according to the ratio


title: Gravitational redshift

text: In the case where neither the emitter nor the observer is at infinity, the transitivity of Doppler shifts allows us to generalize the result to formula_18. The redshift formula for the frequency formula_19 is formula_20. When formula_21 is small, these results are consistent with the equation given above based on the equivalence principle.


title: Gravitational redshift

text: The redshift ratio may also be expressed in terms of a (Newtonian) escape velocity formula_22 at formula_23, resulting in the corresponding Lorentz factor:


title: Gravitational redshift

text: For an object compact enough to have an event horizon, the redshift is not defined for photons emitted inside the Schwarzschild radius, both because signals cannot escape from inside the horizon and because an object such as the emitter cannot be stationary inside the horizon, as was assumed above. Therefore, this formula only applies when formula_16 is larger than formula_8. When the photon is emitted at a distance equal to the Schwarzschild radius, the redshift will be "infinitely" large, and it will not escape to "any" finite distance from the Schwarzschild sphere. When the photon is emitted at an infinitely large distance, there is no redshift.


title: Gravitational redshift

text: In the Newtonian limit, i.e. when formula_16 is sufficiently large compared to the Schwarzschild radius formula_8, the redshift can be approximated as


title: Gravitational redshift

text: where formula_30 is the gravitational acceleration at formula_16. For Earth's surface with respect to infinity, "z" is approximately 7 × 10 (the equivalent of a 0.2 m/s radial Doppler shift); for the Moon it is approximately 3 × 10 (about 1 cm/s). The value for the surface of the sun is about 2 × 10, corresponding to 0.64 km/s. (For non-relativisitc velocities, the radial Doppler equivalent velocity can be approximated by multiplying "z" with the speed of light.)


title: Gravitational redshift

text: The z-value can be expressed succinctly in terms of the escape velocity at formula_16, since the gravitational potential is equal to half the square of the escape velocity, thus:


title: Gravitational redshift

text: It can also be related to the circular orbit velocity formula_36 at formula_16, which equals formula_38, thus


title: Gravitational redshift

text: For example, the gravitational blueshift of distant starlight due to the sun's gravity, which the Earth is orbiting at about 30 km/s, would be approximately 1 × 10 or the equivalent of a 3 m/s radial Doppler shift. However, the Earth is in free-fall around the sun, and is thus an inertial observer, so the effect is not visible.


title: Gravitational redshift

text: For an object in a (circular) orbit, the gravitational redshift is of comparable magnitude as the transverse Doppler effect, formula_40 where "β"="v"/"c", while both are much smaller than the radial Doppler effect, for which formula_41.


title: Gravitational redshift

text: A number of experimenters initially claimed to have identified the effect using astronomical measurements, and the effect was considered to have been finally identified in the spectral lines of the star Sirius B by W.S. Adams in 1925. However, measurements by Adams have been criticized as being too low and these observations are now considered to be measurements of spectra that are unusable because of scattered light from the primary, Sirius A. The first accurate measurement of the gravitational redshift of a white dwarf was done by Popper in 1954, measuring a 21 km/s gravitational redshift of 40 Eridani B. The redshift of Sirius B was finally measured by Greenstein "et al." in 1971, obtaining the value for the gravitational redshift of 89±16 km/s, with more accurate measurements by the Hubble Space Telescope, showing 80.4±4.8 km/s.


title: Gravitational redshift

text: James W. Brault, a graduate student of Robert Dicke at Princeton University, measured the gravitational redshift of the sun using optical methods in 1962. In 2020, a team of scientists published the most accurate measurement of the solar gravitational redshift so far, made by analyzing Fe spectral lines in sunlight reflected by the moon; their measurement of a mean global 638 ± 6m/s lineshift is in agreement with the theoretical value of 633.1 m/s. Measuring the solar redshift is complicated by the Doppler shift caused by the motion of the sun's surface, which is of similar magnitude as the gravitational effect.


title: Gravitational redshift

text: In 2011 the group of Radek Wojtak of the Niels Bohr Institute at the University of Copenhagen collected data from 8000 galaxy clusters and found that the light coming from the cluster centers tended to be red-shifted compared to the cluster edges, confirming the energy loss due to gravity.


title: Gravitational redshift

text: In 2018, the star S2 made its closest approach to Sgr A*, the 4-million solar mass supermassive black hole at the centre of the Milky Way, reaching 7650 km/s or about 2.5% of the speed of light while passing the black hole at a distance of just 120 AU, or 1400 Schwarzschild radii. Independent analyses by the GRAVITY collaboration (led by Reinhard Genzel) and the KECK/UCLA Galactic Center Group (led by Andrea Ghez) revealed a combined transverse Doppler and gravitational redshift up to 200 km/s/c, in agreement with general relativity predictions.


title: Gravitational redshift

text: In 2021, Mediavilla (IAC, Spain) & Jiménez-Vicente (UGR, Spain) were able to use measurements of the gravitational redshift in quasars up to cosmological redshift of z~3 to confirm the predictions of Einstein's Equivalence Principle and the lack of cosmological evolution within 13%.


title: Gravitational redshift

text: The effect is now considered to have been definitively verified by the experiments of Pound, Rebka and Snider between 1959 and 1965. The Pound–Rebka experiment of 1959 measured the gravitational redshift in spectral lines using a terrestrial Fe gamma source over a vertical height of 22.5 metres. This paper was the first determination of the gravitational redshift which used measurements of the change in wavelength of gamma-ray photons generated with the Mössbauer effect, which generates radiation with a very narrow line width. The accuracy of the gamma-ray measurements was typically 1%.


title: Gravitational redshift

text: An improved experiment was done by Pound and Snider in 1965, with an accuracy better than the 1% level.


title: Gravitational redshift

text: A very accurate gravitational redshift experiment was performed in 1976, where a hydrogen maser clock on a rocket was launched to a height of 10,000 km, and its rate compared with an identical clock on the ground. It tested the gravitational redshift to 0.007%.


title: Gravitational redshift

text: Later tests can be done with the Global Positioning System (GPS), which must account for the gravitational redshift in its timing system, and physicists have analyzed timing data from the GPS to confirm other tests. When the first satellite was launched, it showed the predicted shift of 38 microseconds per day. This rate of the discrepancy is sufficient to substantially impair the function of GPS within hours if not accounted for. An excellent account of the role played by general relativity in the design of GPS can be found in Ashby 2003.


title: Gravitational redshift

text: In 2020 a group at the University of Tokyo measured the gravitational redshift of two strontium-87 optical lattice clocks. The measurement took place at Tokyo Tower where the clocks were separated by approximately 450 m and connected by telecom fibers. The gravitational redshift can be expressed as


title: Gravitational redshift

text: where formula_43 is the gravitational redshift, formula_44 is the optical clock transition frequency, formula_45 is the difference in gravitational potential, and formula_46 denotes the violation from general relativity. By Ramsey spectroscopy of the strontium-87 optical clock transition (429 THz, 698 nm) the group determined the gravitational redshift between the two optical clocks to be 21.18 Hz, corresponding to a "z"-value of approximately 5 × 10. Their measured value of formula_46, formula_48, is an agreement with recent measurements made with hydrogen masers in elliptical orbits.