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Friday, May 2, 2025

Physics and Star Wars

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Physics_and_Star_Wars

The interstellar space opera epic Star Wars uses science and technology in its settings and storylines. The series has showcased many technological concepts, both in the movies and in the expanded universe of novels, comics and other forms of media. The Star Wars movies' primary objective is to build upon drama, philosophy, political science and less on scientific knowledge. Many of the on-screen technologies created or borrowed for the Star Wars universe were used mainly as plot devices.

The iconic status that Star Wars has gained in popular culture and science fiction allows it to be used as an accessible introduction to real scientific concepts. Many of the features or technologies used in the Star Wars universe are not yet considered possible. Despite this, their concepts are still probable.

Tatooine's twin stars

A NASA depiction of a theoretical viewpoint from Kepler-16b's orbit of its two stars

In the past, scientists thought that planets would be unlikely to form around binary stars. However, recent simulations indicate that planets are just as likely to form around binary star systems as single-star systems. Of the 3457 exoplanets currently known, 146 actually orbit binary star systems (and 39 orbit multiple star systems with three or more stars). Specifically, they orbit what are known as "wide" binary star systems where the two stars are fairly far apart (several AU). Tatooine appears to be of the other type — a "close" binary, where the stars are very close, and the planets orbit their common center of mass.

The first observationally confirmed binary — Kepler-16b — is a close binary. Exoplanet researchers' simulations indicate that planets form frequently around close binaries, though gravitational effects from the dual star system tend to make them very difficult to find with current Doppler and transit methods of planetary searches. In studies looking for dusty disks—where planet formation is likely—around binary stars, such disks were found in wide or narrow binaries, or those whose stars are more than 50 or less than 3 AU apart, respectively. Intermediate binaries, or those with between 3 and 50 AU between them, had no dusty disks. In 2011 it was reported by The Guardian that NASA space telescope Kepler had discovered a planet, named Kepler-16b, with twin suns as seen in the Star Wars films.

Certified astrophysicist and Star Wars fan Jeanne Cavelos explains that scientists have been skeptical about the likelihood of binary star systems such as Tatooine since the gravity of one star may prevent planets from developing around the other. Two stars of different masses orbiting one another would cause gravity fields to shift, causing potential instabilities in the orbits of any planets in their system.

According to her, even planets in more stable orbits of a binary star system would suffer other kinds of problems such as climatic problems. As an example, a planet in a binary star system orbiting the larger star would be drawn closer to its gravitational field, causing the planet to endure heat of great temperatures during this period. As the planet passes its larger star and reaches the orbit of its smaller star, the gravitational field of that star would give the planet more distance from it. The distance (perhaps along with the smaller solar projection of the star) would send the planet into extreme frigid temperatures.

According to Cavelos, astronomers hypothesize at least two possible solutions to these problems exist and that even life supporting binary star systems could exist. One scenario could be two stars billions of kilometres apart. A planet or planets would be able to orbit one star while at minimum influence of the other. A star known as Proxima Centauri, or Alpha Centauri C, is about one trillion kilometres away from its sister stars, Alpha Centauri A and B. Also according to Cavelos, astronomers believe that Proxima Centauri could have planets of its own. If so, they would be minimally influenced by Proxima Centauri's sister stars due to the vast distance between them and these sister stars. Assuming the existence of planets around Proxima Centauri, from these planets the sister suns would appear as bright stars in the sky.

Another scenario would be two stars that would be closer to one another at a distance of only a few million kilometres. A planet orbiting far enough away would be affected by their gravitational fields almost as if there were one. If the distance between the two stars was a small fraction of the distance between them and the planet, it would be stable for the planet. Dawn and dusk would occur on such a planet as they would on Tatooine.

Blaster bolts

Star Wars makes heavy use of blaster and ion weaponry, attributed to laser, plasma, or particle based bolts of light. Characters can be seen escaping, or even dodging those bolts, and the blaster bolts themselves can be seen flying at a moderate-fast speed. Dodging a laser bolt would be nearly impossible, as it would travel at the speed of light. Due to that, it is reasonable the blaster fire would pass like a sparkle, and hit its target. Sometimes, characters will call the bolts "laser bolts" that, while they do not travel at light speed, are made of intense light energy.

However, many official canonical Star Wars sources state that blaster technology is different from real lasers. According to official canon, they are a form of particle beam. This is supported by how "magnetically sealed" walls deflect them.

The Polish Academy of Sciences in collaboration with the University of Warsaw managed to film an ultra short laser pulse by using cameras that produce billions of frames per second. These laser pulses were so powerful that they almost instantly ionized the atoms they encountered, resulting in the formation of a plasma fiber filament.

The effects of a blaster on a live target were portrayed more or less the same in every part of the Star Wars series. Since blaster bolts consist of light or particle based energy, the bolts would burn through the flesh of a target, with some even exploding against their target, exerting great force. The latter effect was usually from a blaster with greater size. Blasters have even been shown to have plasma energy as ammunition, which is portrayed as blue bolts. As of The Force Awakens, these blue bolts rupture and damage flesh with little to no burning, which causes bleeding injuries, as Poe shot a Stormtrooper with a blaster that caused him to bleed until death. Another instance of a blaster causing bleeding was when Chewbacca shot Kylo Ren with his Bowcaster, the small explosion against his body causing a bleeding injury coupled with burns. In many modern showings of blaster fights, someone hit by a blaster has cinders and soot outlining the area where they were shot. Also blasters hit with great amounts of friction and kinetic energy, enough to cause sparks to fly off the target, make the target burst into flames, or kill a target on impact, even if the target is not penetrated by the bolt, as it is when some targets are armored against blasters.

Vibration in vacuum

Star Wars is famously known for its epic space dogfights. Blaster, engine, and explosion sounds can be heard in those space scenes. Space is a vacuum, however, and since sound requires matter to propagate, the audience should not hear any sound.

This has been explained in some Star Wars media as the result of a sensor system that creates three-dimensional sound inside the cockpit or bridge matching the external movement of other vessels, as a form of multimodal interface, although the audience is still able to hear sound even from a perspective that is in space. In the canon novel Lords of the Sith it is explained that the characters in a galaxy far, far away indeed do not hear any sound in space if no longer confined by their vessels:

[Vader's] interceptor streaked toward the gun bubble, aimed directly at it. Content with the trajectory, he unstrapped himself, overrode the interceptor's safeties, threw open the cockpit hatch, and ejected into space.

Immediately he was spinning in the zero-g, the ship and stars alternating positions with rapidity. Yet he kept his mental hold on the air-lock handle, and his armor, sealed and pressurized, sustained him in the vacuum. The respirator was loud in his ears.

His ship slammed into the gun bubble and the transport, the inability of the vacuum to transmit sound causing the collision to occur in eerie silence. Fire flared for a moment, but only a moment before the vacuum extinguished it.

Therefore, the ability to hear sound in a vacuum by the audience is not heard by the iconic characters, but only to the audience as an interpretation to imagine what sounds we hear in the films as out-of-universe artifacts.

Asteroid field in Episode V

In The Empire Strikes Back, after the Battle of Hoth, the Millennium Falcon is pursued by Imperial ships through a dense asteroid field. The chunks of rock in the field are moving at rapid speeds, constantly colliding, and densely packed. Ordinarily, an asteroid field or belt is unlikely to be so densely packed with large objects, because collisions reduce large objects to rubble. About the only way for an asteroid belt to maintain itself would be to "balance destructive high-speed collisions with constructive soft collisions", but it is unclear whether this is happening in the film.

In contrast to Star Wars, the ship featured in 2001: A Space Odyssey, Discovery One, had a course that took it directly through the asteroid belt in the novel, without real fear of collision on the part of the mission organizers. However, the Solar System's Asteroid Belt is far less dense and several real spacecraft have passed through it without harm.

On the other hand, the so-called Trojan asteroid fields, named after the asteroids found in Jupiter-Sun Lagrange points, are known to be packed much more densely. The Solar System contains two such fields, the Greek Trojans and the Trojan Trojans, and two more (Neptune's trojans) have been discovered recently, but little is known about them currently.

Also, contained within this scene is a portion in which Han and Leia emerge from the Millennium Falcon, and are seen wearing only a facemask for air. The lack of pressure would have likely caused rapid decompression of their bodies, as the asteroid likely did not have an atmosphere. (See Effect of spaceflight on the human body.)

Flight dynamics

Unlike the true flight dynamics of space, those seen in Star Wars closely mirror the familiar dynamics of flying in Earth's atmosphere. For example, fixed-wing aircraft must make banked turns because they use air pressure to operate. Yet, in the airless vacuum of space in Star Wars, the spaceships always (unnecessarily) bank when turning. Physicist Lawrence M. Krauss says this is for a simple reason: "it looks good." By banking, the center of gravity would be maintained so up is still up but the g forces generated at such speeds would surely injure the occupants. This is handled in the films by devices known as "inertial compensators".

In order to turn in non-atmospheric flight, some force must still be applied to the craft, presumably by some sort of thruster or generated force field wave, the location of which (in relation to the craft's centre of gravity) will dictate the orientation of the ship, or bank angle, required to make the turn.

Destruction over Endor

Following the events of Return of the Jedi, there has been widespread speculation that the destruction of the second Death Star as seen in the film would cause a radiation spread on the forest moon of Endor's atmosphere and surface, given that the explosion was caused by an attack on its (nuclear) core reactor.

The phenomenon has been around supposedly since 1997 following a number of comic book productions on Star Wars beyond the original trilogy (of unknown canonicity, although like most other works it has been declared non-canonical and part of the distinct Star Wars Legends continuity in 2014) and has been known as "The Endor Holocaust". It came about from a rational analysis in multiple commentaries of the aftermath of the second Death Star's destruction and its hypothetical effects on the forest moon and its living inhabitants. Based on all the information from the stories, it has been concluded that a nuclear fallout would cause radioactive contamination on the surface of the planet (or moon), leading to widespread death and destruction.

More recent analysis by physicists has supported the theory from a scientific perspective.

Studying and analyzing the second Death Star's destruction, physicists hypothesize its results and consequences. Astrophysicist and Star Wars fan Dave Mosher covers the film's events in a 10,000 word essay. His first argument is the Death Star explosion resulting from the rebel attack on its nuclear reactor, the whole space station would be reduced to a large number of fine metallic pieces raining down on Endor. The debris would burn up in Endor's atmosphere turning into toxic soot and spark planetary firestorms.

Another scientist, Sarah Stewart, reanalyzes the situation and theorizes the moon's previous state after some environmental cleanup from the Death Star's fallout.

Matija Cuk, who studies orbital dynamics, theorizes the Death Star's reactor blowing up in one second, sending enormous chunks of debris at about 220,000 miles per hour. He argues the energy carried by the debris would not be sufficient to destroy the moon, but erode the side facing the Death Star. He also argues all ships near the Death Star at the time of its explosion would be destroyed by it. He also adds the rebels witnessing the explosion from the planet's surface would be killed by the radiation released from the explosion even before the debris reaches them.

He concludes the debris following the explosion would strike the moon's surface and would send rocks on the surface to the far side of the moon. In his analysis, the extinction of the Ewoks is inevitable.[16]

Planetary physicist Erik Asphaug, who also studies giant impacts on moons and planets opposes these theories. He argues the Death Star would not be reduced to tiny bits following explosion. He argues that all nuclear explosions in rock would vaporize matter near it, but break matter a further distance away into pieces. The further away the pieces, the less they would break. He concludes large chunks of the Death Star would hit the forest moon's surface, some even creating craters. The most problematic result in his analysis is the fire caused by the large radioactive debris that would set the moon's forests ablaze.

A detailed analysis to the aftermath of the Death Star explosion in Return of the Jedi by planetary scientist Dave Minton, concludes all the Ewoks would have died as a result. Using the information provided from the holograms in the briefing scene aboard the giant cruiser Home One in Episode VI, Minton estimates the diameter of the Death Star (or Death Star II to distinguish it from the first Death Star in Episode IV: A New Hope) is about three hundred forty three kilometers or about seven percent the diameter of Endor.

This would make Endor slightly larger than Mars but about 15% the size of Earth. He also notes that in diameter, Endor would still be smaller than Mars, but denser in mass by his measurement formula. Endor's composition being smaller would be unusual, but not impossible according to him.

He applies this data to the orbital dynamics problem. Discounting the possibility of the second Death Star being preserved in Endor's orbit by the use of anti-gravitational repulsors (a commonality in the Star Wars galaxy), Minton instead compares the Death Star in the forest moon's orbit to that of a satellite in Earth's orbit. Applying Kepler's Third Law, he determines an orbital period as exactly one day. But applying this law, he determines astrophysical problems with the Death Star using Endor's gravity to sustain itself in the forest moon's orbit. For simplicity, he assumes a day on Endor as 24 hours.

Minton also argues the explosion of the second Death Star in Episode VI is lighter than that of the first one in Episode IV. His argument is drawn from the two films where the one in A New Hope explodes instantaneously; wheres the second one in Return of the Jedi explodes in a longer time period, allowing the rebel pilots to escape alive and their ships unharmed by the explosion. The film specifically shows Wedge Antilles and Lando Calrissian hitting two main sections of the core reactor from an X-wing fighter and the Millennium Falcon (co-piloted by Nien Nunb), causing the reactor to collapse and start a chain explosion and resulting in the Death Star blowing up from a series of internal explosions and collapses.

Minton therefore concludes there would be little vaporization of remaining material and that the explosion would move a lot slower than what is required to keep them in orbit, which he estimates is about 212 miles per second. Using the equation representing orbital velocity of the Death Star, he theorizes the fragments would need to be orbiting at about 4.5 kilometers per second to maintain orbit at the same altitude the Death Star had been. Since this does not happen, he argues the remains of the former Death Star would fall straight into the area where the shield generator has been on the moon's surface.

To estimate the effects of the second Death Star, Minton looks into its mass. According to estimated data from some students of Lehigh University, the steel mass needed for building one would be around 770 kilograms times the mass cubed in weight ⁠— ⁠this would give the Death Star a mass of about 1019 kg. Using this data, Minton produces equations that lead him to conclude the fragments would hit the moon's surface so hard it would cause craters almost four times the size of the Chicxulub crater in Mexico. This impact would cause a planetary firestorm and vaporize all lifeforms on the moon.

Hyperspace travel

The hyperspace travel in the Star Wars franchise requires two elements, light speed travel and hyperspace. Ships in the Star Wars Universe have engines capable of propelling them to the speed of light. However, current physical theory states that it is impossible for any physical object to attain that speed, as long as the object has a non-zero mass, because an infinite amount of energy would be required to accelerate the mass to such a speed ⁠— ⁠a logical impossibility in our universe. Moreover, even if one were traveling at light speed, it would still take thousands of years to travel even a moderately sized galaxy. It is for these reasons that Star Wars space vessels use a "hyperdrive".

This is explained by having the ships warp to another "dimension", presumably a brane universe with different physical laws. Gravity supposedly reaches between branes. In Star Wars, gravity in real spaces forms gravitational "mass shadows" in hyperspace. Hyperspace in Star Wars is unrelated to the presumed space between universal "bubbles" in real life physics.

Hyperspace travel has also been noted to have some form of air resistance, as seen in "Deal No Deal", an episode of the Star Wars: the Clone Wars TV series. Trace Martez – smuggler and friend of Ahsoka Tano – apologises for flight turbulence on her heavily modified Nebula-class freighter, nicknamed the "Silver Angel", having "left the air brakes on". This would be normal, if Martez was encountering air resistance in the atmosphere of Coruscant - the planet she had just left. However, she only encountered turbulence once she entered hyperspace, which suggests that hyperspace has some form of gaseous atmosphere, for lack of a better term.

Planets, moons and planetoids

Map of the Star Wars galaxy

In the Star Wars franchise, almost everyone can breathe and move on many planets, and these, as well as the star systems, are treated as small places. Both defects have an accurate explanation.

The Star Wars Expanded Universe states that many of the planets of the galaxy were colonized and adapted to the atmosphere and gravity of the most populated species, and there are also many species—such as Kel Dor and Skakoans—that need to use devices like breathing masks or pressurized suits. In the other case, since the Star Wars franchise develops itself to the intergalactic level, it is assumed that almost all the planets on it are planetary civilizations, a theory well-based in reality and that could possibly happen in a distant future.

The novelization of A New Hope, ghostwritten by Alan Dean Foster, mentions that humans colonized Tatooine in the section introducing the Tusken Raiders. The section implies that humans colonized the planet and settled in the more remote areas of the much sparsely populated planet, which did not give much chance of contact between the Tusken Raiders and the human colonists, who settled on the planet in small numbers.

Also in the same novel, the section introducing the planet Yavin describes it as uninhabitable. Its satellite moons are described as planet sized. The fourth moon called "Yavin IV" as it was named by early human colonizers is described rich with plant and animal life. It describes an ancient civilization that once existed in the jungles of the moon but disappeared centuries before human explorers ever set foot on the moon. The only evidence of their existence the ancient architectural sites and monuments they left behind (as seen in the film), most of which were mysteriously built. At the time the Rebel Alliance used territory on Yavin as their hidden base, the only thing left on the moon was plant, insect and animal life.

Jeanne Cavelos points to the Tales of the Jedi comic book series that document the early colonization of much of the populated Star Wars galaxy. Her argument is that the humans in the Star Wars galaxy being a single species, as well as appearing and living like human beings on Earth, likely originated from a single Earth-like planet, though the exact origin or home world of the human species in the Star Wars universe is not exactly known. She suggests that to be able to colonize other planets, the humans of the Star Wars galaxy could not have been genetically altered. She points to the fact that Luke Skywalker lived his life on Tatooine but did not require any genetic altering to adapt to Hoth, a planet with a climate estimately the opposite of Tatooine.

There are also problems with the possibility of humans altering the climate of the planet they colonize. She mentions the fact that there are native species on planets that humans live on, such as the Jawas alongside the Tusken Raiders on Tatooine who survive in the same climate as humans live on. If they lived in another climate prior to human colonization and environmental modification/alternation, such as terraforming, they are unlikely to survive.

Another possibility she suggests is the use of artificial aids that would help the colonists adapting to life on a newly settled planet before gradually adapting to life there. Some variations in climate and gravity would be adaptable to the colonists over a few generations as long as the variations are not too great. Through a period of generations, the colonists would evolve and adapt, even perhaps by evolutionary mutations.

There is also the unlikelihood of other planets having air just like Earth's and automatically being breathable according to other scientists, Cavelos claims. Only a small number of such planets probably exist. The chances are greater of finding planets with similar atmospheres that would require minimal atmospheric modification, but unlikely to be identical to Earth's that arriving humans could simply survive on them.

Another issue amongst this is that if human species would be unlikely to encounter a planet with an exact Earth-like environment, it would be even more unlikely for so many different alien species to be of the same environmental background and surviving in the same environmental conditions as seen at the Mos Eisley cantina in A New Hope.

Lightsabers

Green lightsaber

Often, lightsabers are said to be composed of lasers. However, using lasers raises several issues:

  • The necessity of something to reflect the end of the beam.
  • Having a compact and powerful enough power source.
  • Lasers do not clash when their beams cross.
  • Lasers are silent.
  • There are some materials that can withstand a lightsaber, and some can even deactivate one upon contact. 

Earlier forms of the weapon were known as "protosabers" in the Star Wars galaxy that required battery packs which were connected to the lightsaber hilt through a power cord. The battery pack was attached to a belt worn by the Jedi using the lightsaber, similar to how a flamethrower is worn, but was not ideal as it restricted the Jedi's movements during combat.

Lightsabers have been generally explained as plasma kept in a force field, usually an electric or magnetic field. The force field could not be magnetic, because the field contains heat, something a magnetic field is incapable of doing. Thus, the force field must be a shield not known by modern technology. Additionally, when two plasma blades would come into direct contact, it would almost certainly result in magnetic reconnection, causing an explosive release of the plasma contained in both sabers.

The problems with lightsabers that use actual light blades mentioned at the beginning of this section are not all insurmountable. For instance, it is mentioned that "Lasers do not clash when their beams cross", which is a statement based on our day-to-day experience with light. But Euler and Heisenberg have shown in 1936 that, for sufficiently high intensities, light can actually interact with itself (an effect due to quantum fluctuations of the vacuum). Given this, then it is possible to imagine a scenario of two lightsabers clashing in which photons coming from the hilt of one lightsaber are scattered toward the hilt of the other lightsaber (the scattering is done in the region where the two lightsabers overlap). Since photons have momentum, those scattered photons would exert radiation pressure on the hilt of the other lightsaber. Using techniques from ultrahigh intensity lasers, it has been shown that for lasers with an electric field strength of the order of 1015 V/m, the force felt in the hilt of each lightsabers is approximately 10 N (roughly the weight of a one kilogram object). This force due to scattered photons would give an impression of blade solidity when the two lightsabers clash. An incredible amount of energy is necessary to power such a lightsaber. For instance, powering a lightsaber with an electric field strength of 1015 V/m for one minute requires 1025 J, or ten times less than the total energy output of the Sun in one second. If the energy source is nuclear fusion, such a lightsaber would require 1011 kg of nuclear fusion fuel to operate for one minute. In other words, one would need to fit the equivalent of ten Great Pyramid of Giza-s of nuclear fusion fuel in the hilt to operate such a lightsaber for one minute.

Thursday, May 1, 2025

Materials science

From Wikipedia, the free encyclopedia
A diamond cuboctahedron showing seven crystallographic planes, imaged with scanning electron microscopy
Six classes of conventional engineering materials.
Six classes of conventional engineering materials

Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries.

The intellectual origins of materials science stem from the Age of Enlightenment, when researchers began to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in metallurgy and mineralogy. Materials science still incorporates elements of physics, chemistry, and engineering. As such, the field was long considered by academic institutions as a sub-field of these related fields. Beginning in the 1940s, materials science began to be more widely recognized as a specific and distinct field of science and engineering, and major technical universities around the world created dedicated schools for its study.

Materials scientists emphasize understanding how the history of a material (processing) influences its structure, and thus the material's properties and performance. The understanding of processing -structure-properties relationships is called the materials paradigm. This paradigm is used to advance understanding in a variety of research areas, including nanotechnology, biomaterials, and metallurgy.

Materials science is also an important part of forensic engineering and failure analysis – investigating materials, products, structures or components, which fail or do not function as intended, causing personal injury or damage to property. Such investigations are key to understanding, for example, the causes of various aviation accidents and incidents.

History

A late Bronze Age sword or dagger blade

The material of choice of a given era is often a defining point. Phases such as Stone Age, Bronze Age, Iron Age, and Steel Age are historic, if arbitrary examples. Originally deriving from the manufacture of ceramics and its putative derivative metallurgy, materials science is one of the oldest forms of engineering and applied science. Modern materials science evolved directly from metallurgy, which itself evolved from the use of fire. A major breakthrough in the understanding of materials occurred in the late 19th century, when the American scientist Josiah Willard Gibbs demonstrated that the thermodynamic properties related to atomic structure in various phases are related to the physical properties of a material. Important elements of modern materials science were products of the Space Race; the understanding and engineering of the metallic alloys, and silica and carbon materials, used in building space vehicles enabling the exploration of space. Materials science has driven, and been driven by, the development of revolutionary technologies such as rubbers, plastics, semiconductors, and biomaterials.

Before the 1960s (and in some cases decades after), many eventual materials science departments were metallurgy or ceramics engineering departments, reflecting the 19th and early 20th-century emphasis on metals and ceramics. The growth of material science in the United States was catalyzed in part by the Advanced Research Projects Agency, which funded a series of university-hosted laboratories in the early 1960s, "to expand the national program of basic research and training in the materials sciences." In comparison with mechanical engineering, the nascent material science field focused on addressing materials from the macro-level and on the approach that materials are designed on the basis of knowledge of behavior at the microscopic level. Due to the expanded knowledge of the link between atomic and molecular processes as well as the overall properties of materials, the design of materials came to be based on specific desired properties. The materials science field has since broadened to include every class of materials, including ceramics, polymers, semiconductors, magnetic materials, biomaterials, and nanomaterials, generally classified into three distinct groups: ceramics, metals, and polymers. The prominent change in materials science during the recent decades is active usage of computer simulations to find new materials, predict properties and understand phenomena.

Fundamentals

The materials paradigm represented in the form of a tetrahedron

A material is defined as a substance (most often a solid, but other condensed phases can be included) that is intended to be used for certain applications. There are a myriad of materials around us; they can be found in anything from new and advanced materials that are being developed include nanomaterials, biomaterials, and energy materials to name a few.

The basis of materials science is studying the interplay between the structure of materials, the processing methods to make that material, and the resulting material properties. The complex combination of these produce the performance of a material in a specific application. Many features across many length scales impact material performance, from the constituent chemical elements, its microstructure, and macroscopic features from processing. Together with the laws of thermodynamics and kinetics materials scientists aim to understand and improve materials.

Structure

Structure is one of the most important components of the field of materials science. The very definition of the field holds that it is concerned with the investigation of "the relationships that exist between the structures and properties of materials". Materials science examines the structure of materials from the atomic scale, all the way up to the macro scale. Characterization is the way materials scientists examine the structure of a material. This involves methods such as diffraction with X-rays, electrons or neutrons, and various forms of spectroscopy and chemical analysis such as Raman spectroscopy, energy-dispersive spectroscopy, chromatography, thermal analysis, electron microscope analysis, etc.

Structure is studied in the following levels.

Atomic structure

Atomic structure deals with the atoms of the materials, and how they are arranged to give rise to molecules, crystals, etc. Much of the electrical, magnetic and chemical properties of materials arise from this level of structure. The length scales involved are in angstroms (Å). The chemical bonding and atomic arrangement (crystallography) are fundamental to studying the properties and behavior of any material.

Bonding

To obtain a full understanding of the material structure and how it relates to its properties, the materials scientist must study how the different atoms, ions and molecules are arranged and bonded to each other. This involves the study and use of quantum chemistry or quantum physics. Solid-state physics, solid-state chemistry and physical chemistry are also involved in the study of bonding and structure.

Crystallography
Crystal structure of a perovskite with a chemical formula ABX3

Crystallography is the science that examines the arrangement of atoms in crystalline solids. Crystallography is a useful tool for materials scientists. One of the fundamental concepts regarding the crystal structure of a material includes the unit cell, which is the smallest unit of a crystal lattice (space lattice) that repeats to make up the macroscopic crystal structure. Most common structural materials include parallelpiped and hexagonal lattice types. In single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically, because the natural shapes of crystals reflect the atomic structure. Further, physical properties are often controlled by crystalline defects. The understanding of crystal structures is an important prerequisite for understanding crystallographic defects. Examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter-stitials, and more that are linear, planar, and three dimensional types of defects. New and advanced materials that are being developed include nanomaterials, biomaterials. Mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. Because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. Most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. Polymers display varying degrees of crystallinity, and many are completely non-crystalline. Glass, some ceramics, and many natural materials are amorphous, not possessing any long-range order in their atomic arrangements. The study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties.

Nanostructure

Buckminsterfullerene nanostructure

Materials, which atoms and molecules form constituents in the nanoscale (i.e., they form nanostructures) are called nanomaterials. Nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit.

Nanostructure deals with objects and structures that are in the 1 – 100 nm range. In many materials, atoms or molecules agglomerate to form objects at the nanoscale. This causes many interesting electrical, magnetic, optical, and mechanical properties.

In describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale.

Nanotextured surfaces have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm.

Nanotubes have two dimensions on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length could be much greater.

Finally, spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) often are used synonymously although UFP can reach into the micrometre range. The term 'nanostructure' is often used, when referring to magnetic technology. Nanoscale structure in biology is often called ultrastructure.

Microstructure

Microstructure of pearlite

Microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25× magnification. It deals with objects from 100 nm to a few cm. The microstructure of a material (which can be broadly classified into metallic, polymeric, ceramic and composite) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature behavior, wear resistance, and so on. Most of the traditional materials (such as metals and ceramics) are microstructured.

The manufacture of a perfect crystal of a material is physically impossible. For example, any crystalline material will contain defects such as precipitates, grain boundaries (Hall–Petch relationship), vacancies, interstitial atoms or substitutional atoms. The microstructure of materials reveals these larger defects and advances in simulation have allowed an increased understanding of how defects can be used to enhance material properties.

Macrostructure

Macrostructure is the appearance of a material in the scale millimeters to meters, it is the structure of the material as seen with the naked eye.

Properties

Materials exhibit myriad properties, including the following.

The properties of a material determine its usability and hence its engineering application.

Processing

Synthesis and processing involves the creation of a material with the desired micro-nanostructure. A material cannot be used in industry if no economically viable production method for it has been developed. Therefore, developing processing methods for materials that are reasonably effective and cost-efficient is vital to the field of materials science. Different materials require different processing or synthesis methods. For example, the processing of metals has historically defined eras such as the Bronze Age and Iron Age and is studied under the branch of materials science named physical metallurgy. Chemical and physical methods are also used to synthesize other materials such as polymers, ceramics, semiconductors, and thin films. As of the early 21st century, new methods are being developed to synthesize nanomaterials such as graphene.

Thermodynamics

A phase diagram for a binary system displaying a eutectic point

Thermodynamics is concerned with heat and temperature and their relation to energy and work. It defines macroscopic variables, such as internal energy, entropy, and pressure, that partly describe a body of matter or radiation. It states that the behavior of those variables is subject to general constraints common to all materials. These general constraints are expressed in the four laws of thermodynamics. Thermodynamics describes the bulk behavior of the body, not the microscopic behaviors of the very large numbers of its microscopic constituents, such as molecules. The behavior of these microscopic particles is described by, and the laws of thermodynamics are derived from, statistical mechanics.

The study of thermodynamics is fundamental to materials science. It forms the foundation to treat general phenomena in materials science and engineering, including chemical reactions, magnetism, polarizability, and elasticity. It explains fundamental tools such as phase diagrams and concepts such as phase equilibrium.

Kinetics

Chemical kinetics is the study of the rates at which systems that are out of equilibrium change under the influence of various forces. When applied to materials science, it deals with how a material changes with time (moves from non-equilibrium to equilibrium state) due to application of a certain field. It details the rate of various processes evolving in materials including shape, size, composition and structure. Diffusion is important in the study of kinetics as this is the most common mechanism by which materials undergo change. Kinetics is essential in processing of materials because, among other things, it details how the microstructure changes with application of heat.

Research

Materials science is a highly active area of research. Together with materials science departments, physics, chemistry, and many engineering departments are involved in materials research. Materials research covers a broad range of topics; the following non-exhaustive list highlights a few important research areas.

Nanomaterials

A scanning electron microscopy image of carbon nanotubes bundles

Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 1000 nanometers (10−9 meter), but is usually 1 nm – 100 nm. Nanomaterials research takes a materials science based approach to nanotechnology, using advances in materials metrology and synthesis, which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, or mechanical properties. The field of nanomaterials is loosely organized, like the traditional field of chemistry, into organic (carbon-based) nanomaterials, such as fullerenes, and inorganic nanomaterials based on other elements, such as silicon. Examples of nanomaterials include fullerenes, carbon nanotubes, nanocrystals, etc.

Biomaterials

The iridescent nacre inside a nautilus shell

A biomaterial is any matter, surface, or construct that interacts with biological systems. Biomaterials science encompasses elements of medicine, biology, chemistry, tissue engineering, and materials science.

Biomaterials can be derived either from nature or synthesized in a laboratory using a variety of chemical approaches using metallic components, polymers, bioceramics, or composite materials. They are often intended or adapted for medical applications, such as biomedical devices which perform, augment, or replace a natural function. Such functions may be benign, like being used for a heart valve, or may be bioactive with a more interactive functionality such as hydroxylapatite-coated hip implants. Biomaterials are also used every day in dental applications, surgery, and drug delivery. For example, a construct with impregnated pharmaceutical products can be placed into the body, which permits the prolonged release of a drug over an extended period of time. A biomaterial may also be an autograft, allograft or xenograft used as an organ transplant material.

Electronic, optical, and magnetic

Negative index metamaterial

Semiconductors, metals, and ceramics are used today to form highly complex systems, such as integrated electronic circuits, optoelectronic devices, and magnetic and optical mass storage media. These materials form the basis of our modern computing world, and hence research into these materials is of vital importance.

Semiconductors are a traditional example of these types of materials. They are materials that have properties that are intermediate between conductors and insulators. Their electrical conductivities are very sensitive to the concentration of impurities, which allows the use of doping to achieve desirable electronic properties. Hence, semiconductors form the basis of the traditional computer.

This field also includes new areas of research such as superconducting materials, spintronics, metamaterials, etc. The study of these materials involves knowledge of materials science and solid-state physics or condensed matter physics.

Computational materials science

With continuing increases in computing power, simulating the behavior of materials has become possible. This enables materials scientists to understand behavior and mechanisms, design new materials, and explain properties formerly poorly understood. Efforts surrounding integrated computational materials engineering are now focusing on combining computational methods with experiments to drastically reduce the time and effort to optimize materials properties for a given application. This involves simulating materials at all length scales, using methods such as density functional theory, molecular dynamics, Monte Carlo, dislocation dynamics, phase field, finite element, and many more.

Industry

Beverage containers of all three materials types: ceramic (glass), metal (aluminum), and polymer (plastic).

Radical materials advances can drive the creation of new products or even new industries, but stable industries also employ materials scientists to make incremental improvements and troubleshoot issues with currently used materials. Industrial applications of materials science include materials design, cost-benefit tradeoffs in industrial production of materials, processing methods (casting, rolling, welding, ion implantation, crystal growth, thin-film deposition, sintering, glassblowing, etc.), and analytic methods (characterization methods such as electron microscopy, X-ray diffraction, calorimetry, nuclear microscopy (HEFIB), Rutherford backscattering, neutron diffraction, small-angle X-ray scattering (SAXS), etc.).

Besides material characterization, the material scientist or engineer also deals with extracting materials and converting them into useful forms. Thus ingot casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. Often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. For example, steels are classified based on 1/10 and 1/100 weight percentages of the carbon and other alloying elements they contain. Thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced.

Solid materials are generally grouped into three basic classifications: ceramics, metals, and polymers. This broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. An item that is often made from each of these materials types is the beverage container. The material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. Ceramic (glass) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. Metal (aluminum alloy) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. However, the cans are opaque, expensive to produce, and are easily dented and punctured. Polymers (polyethylene plastic) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass.

Ceramics and glasses

Si3N4 ceramic bearing parts

Another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. Many ceramics and glasses exhibit covalent or ionic-covalent bonding with SiO2 (silica) as a fundamental building block. Ceramics – not to be confused with raw, unfired clay – are usually seen in crystalline form. The vast majority of commercial glasses contain a metal oxide fused with silica. At the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. Windowpanes and eyeglasses are important examples. Fibers of glass are also used for long-range telecommunication and optical transmission. Scratch resistant Corning Gorilla Glass is a well-known example of the application of materials science to drastically improve the properties of common components.

Engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. Alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. Hot pressing provides higher density material. Chemical vapor deposition can place a film of a ceramic on another material. Cermets are ceramic particles containing some metals. The wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties.

Ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. This process involves the strategic addition of second-phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. This approach enhances fracture toughness, paving the way for the creation of advanced, high-performance ceramics in various industries.

Composites

A 6 μm diameter carbon filament (running from bottom left to top right) sitting atop the much larger human hair

Another application of materials science in industry is making composite materials. These are structured materials composed of two or more macroscopic phases.

Applications range from structural elements such as steel-reinforced concrete, to the thermal insulating tiles, which play a key and integral role in NASA's Space Shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re-entry into the Earth's atmosphere. One example is reinforced Carbon-Carbon (RCC), the light gray material, which withstands re-entry temperatures up to 1,510 °C (2,750 °F) and protects the Space Shuttle's wing leading edges and nose cap. RCC is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. After curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a vacuum chamber, and cured-pyrolized to convert the furfuryl alcohol to carbon. To provide oxidation resistance for reusability, the outer layers of the RCC are converted to silicon carbide.

Other examples can be seen in the "plastic" casings of television sets, cell-phones and so on. These plastic casings are usually a composite material made up of a thermoplastic matrix such as acrylonitrile butadiene styrene (ABS) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for added strength, bulk, or electrostatic dispersion. These additions may be termed reinforcing fibers, or dispersants, depending on their purpose.

Polymers

The repeating unit of the polymer polypropylene
Expanded polystyrene polymer packaging

Polymers are chemical compounds made up of a large number of identical components linked together like chains. Polymers are the raw materials (the resins) used to make what are commonly called plastics and rubber. Plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. Plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride (PVC), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. Rubbers include natural rubber, styrene-butadiene rubber, chloroprene, and butadiene rubber. Plastics are generally classified as commodity, specialty and engineering plastics.

Polyvinyl chloride (PVC) is widely used, inexpensive, and annual production quantities are large. It lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. Its fabrication and processing are simple and well-established. The versatility of PVC is due to the wide range of plasticisers and other additives that it accepts. The term "additives" in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties.

Polycarbonate would be normally considered an engineering plastic (other examples include PEEK, ABS). Such plastics are valued for their superior strengths and other special material properties. They are usually not used for disposable applications, unlike commodity plastics.

Specialty plastics are materials with unique characteristics, such as ultra-high strength, electrical conductivity, electro-fluorescence, high thermal stability, etc.

The dividing lines between the various types of plastics is not based on material but rather on their properties and applications. For example, polyethylene (PE) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium-density polyethylene (MDPE) is used for underground gas and water pipes, and another variety called ultra-high-molecular-weight polyethylene (UHMWPE) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low-friction socket in implanted hip joints.

Metal alloys

Wire rope made from steel alloy

The alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steels) make up the largest proportion of metals today both by quantity and commercial value.

Iron alloyed with various proportions of carbon gives low, mid and high carbon steels. An iron-carbon alloy is only considered steel if the carbon level is between 0.01% and 2.00% by weight. For steels, the hardness and tensile strength of the steel is related to the amount of carbon present, with increasing carbon levels also leading to lower ductility and toughness. Heat treatment processes such as quenching and tempering can significantly change these properties, however. In contrast, certain metal alloys exhibit unique properties where their size and density remain unchanged across a range of temperatures. Cast iron is defined as an iron–carbon alloy with more than 2.00%, but less than 6.67% carbon. Stainless steel is defined as a regular steel alloy with greater than 10% by weight alloying content of chromium. Nickel and molybdenum are typically also added in stainless steels.

Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have been known for a long time (since the Bronze Age), while the alloys of the other three metals have been relatively recently developed. Due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. The alloys of aluminium, titanium and magnesium are also known and valued for their high strength to weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. These materials are ideal for situations where high strength to weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications.

Semiconductors

A semiconductor is a material that has a resistivity between a conductor and insulator. Modern day electronics run on semiconductors, and the industry had an estimated US$530 billion market in 2021. Its electronic properties can be greatly altered through intentionally introducing impurities in a process referred to as doping. Semiconductor materials are used to build diodes, transistors, light-emitting diodes (LEDs), and analog and digital electric circuits, among their many uses. Semiconductor devices have replaced thermionic devices like vacuum tubes in most applications. Semiconductor devices are manufactured both as single discrete devices and as integrated circuits (ICs), which consist of a number—from a few to millions—of devices manufactured and interconnected on a single semiconductor substrate.

Of all the semiconductors in use today, silicon makes up the largest portion both by quantity and commercial value. Monocrystalline silicon is used to produce wafers used in the semiconductor and electronics industry. Gallium arsenide (GaAs) is the second most popular semiconductor used. Due to its higher electron mobility and saturation velocity compared to silicon, it is a material of choice for high-speed electronics applications. These superior properties are compelling reasons to use GaAs circuitry in mobile phones, satellite communications, microwave point-to-point links and higher frequency radar systems. Other semiconductor materials include germanium, silicon carbide, and gallium nitride and have various applications.

Relation with other fields

Google Ngram Viewer-diagram visualizing the search terms for complex matter terminology (1940–2018). Green: "materials science", red: "condensed matter physics" and blue: "solid state physics".

Materials science evolved, starting from the 1950s because it was recognized that to create, discover and design new materials, one had to approach it in a unified manner. Thus, materials science and engineering emerged in many ways: renaming and/or combining existing metallurgy and ceramics engineering departments; splitting from existing solid state physics research (itself growing into condensed matter physics); pulling in relatively new polymer engineering and polymer science; recombining from the previous, as well as chemistry, chemical engineering, mechanical engineering, and electrical engineering; and more.

The field of materials science and engineering is important both from a scientific perspective, as well as for applications field. Materials are of the utmost importance for engineers (or other applied fields) because usage of the appropriate materials is crucial when designing systems. As a result, materials science is an increasingly important part of an engineer's education.

Materials physics is the use of physics to describe the physical properties of materials. It is a synthesis of physical sciences such as chemistry, solid mechanics, solid state physics, and materials science. Materials physics is considered a subset of condensed matter physics and applies fundamental condensed matter concepts to complex multiphase media, including materials of technological interest. Current fields that materials physicists work in include electronic, optical, and magnetic materials, novel materials and structures, quantum phenomena in materials, nonequilibrium physics, and soft condensed matter physics. New experimental and computational tools are constantly improving how materials systems are modeled and studied and are also fields when materials physicists work in.

The field is inherently interdisciplinary, and the materials scientists or engineers must be aware and make use of the methods of the physicist, chemist and engineer. Conversely, fields such as life sciences and archaeology can inspire the development of new materials and processes, in bioinspired and paleoinspired approaches. Thus, there remain close relationships with these fields. Conversely, many physicists, chemists and engineers find themselves working in materials science due to the significant overlaps between the fields.

Emerging technologies

Emerging technology Status Potentially marginalized technologies Potential applications Related articles
Aerogel Hypothetical, experiments, diffusion,

early uses

Traditional insulation, glass Improved insulation, insulative glass if it can be made clear, sleeves for oil pipelines, aerospace, high-heat & extreme cold applications
Amorphous metal Experiments Kevlar Armor
Conductive polymers Research, experiments, prototypes Conductors Lighter and cheaper wires, antistatic materials, organic solar cells
Femtotechnology, picotechnology Hypothetical Present nuclear New materials; nuclear weapons, power
Fullerene Experiments, diffusion Synthetic diamond and carbon nanotubes (Buckypaper) Programmable matter
Graphene Hypothetical, experiments, diffusion,

early uses

Silicon-based integrated circuit Components with higher strength to weight ratios, transistors that operate at higher frequency, lower cost of display screens in mobile devices, storing hydrogen for fuel cell powered cars, filtration systems, longer-lasting and faster-charging batteries, sensors to diagnose diseases Potential applications of graphene
High-temperature superconductivity Cryogenic receiver front-end (CRFE) RF and microwave filter systems for mobile phone base stations; prototypes in dry ice; Hypothetical and experiments for higher temperatures Copper wire, semiconductor integral circuits No loss conductors, frictionless bearings, magnetic levitation, lossless high-capacity accumulators, electric cars, heat-free integral circuits and processors
LiTraCon Experiments, already used to make Europe Gate Glass Building skyscrapers, towers, and sculptures like Europe Gate
Metamaterials Hypothetical, experiments, diffusion Classical optics Microscopes, cameras, metamaterial cloaking, cloaking devices
Metal foam Research, commercialization Hulls Space colonies, floating cities
Multi function structures[43] Hypothetical, experiments, some prototypes, few commercial Composite materials Wide range, e.g., self-health monitoring, self-healing material, morphing
Nanomaterials: carbon nanotubes Hypothetical, experiments, diffusion,

early uses

Structural steel and aluminium Stronger, lighter materials, the space elevator Potential applications of carbon nanotubes, carbon fiber
Programmable matter Hypothetical, experiments Coatings, catalysts Wide range, e.g., claytronics, synthetic biology
Quantum dots Research, experiments, prototypes LCD, LED Quantum dot laser, future use as programmable matter in display technologies (TV, projection), optical data communications (high-speed data transmission), medicine (laser scalpel)
Silicene Hypothetical, research Field-effect transistors

Subdisciplines

The main branches of materials science stem from the four main classes of materials: ceramics, metals, polymers and composites.

There are additionally broadly applicable, materials independent, endeavors.

There are also relatively broad focuses across materials on specific phenomena and techniques.

Professional societies

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