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Campfire

A campfire is a fire at a campsite that provides light and warmth, and heat for cooking. It can also serve as a beacon, and an insect and predator deterrent. Established campgrounds often provide a stone or steel fire ring for safety. Campfires are a popular feature of camping. At summer camps, the word campfire often refers to an event (ceremony, get together, etc.) at which there is a fire. Some camps refer to the fire itself as a campfire.

First campfire
A new analysis of burned antelope bones from caves in Swartkrans, South Africa, confirms that Australopithecus robustus and/or Homo erectus built campfires roughly 1.6 million years ago. Nearby evidence within Wonderwerk Cave, at the edge of the Kalahari Desert, has been called the oldest known controlled fire. Microscopic analysis of plant ash and charred bone fragments suggests that materials in the cave were not heated above about 1,300 F. This is consistent with preliminary findings that the fires burned grasses, brush, and leaves. Such fuel would not produce hotter flames. The data suggests humans were cooking prey by campfire as far back as the first appearance of Homo erectus 1.9 million years ago.

Finding a site
Ideally, campfires should be made in a fire ring. If a fire ring is not available, a temporary fire site may be constructed. Bare rock or unvegetated ground is ideal for a fire site. Alternatively, turf may be cut away to form a bare area and carefully replaced after the fire has cooled to minimize damage. Another way is to cover the ground with sand, or other soil mostly free of flammable organic material, to a depth of a few inches. A ring of rocks is sometimes constructed around a fire. Fire rings, however, do not fully protect material on the ground from catching fire. Flying embers are still a threat, and the fire ring may become hot enough to ignite material in contact with it, or the heat the water to a vapor thereby cracking the rocks.

Safety measures
Campfires can spark wildfires. As such, it is important for the fire builder to take multiple safety precautions, including:
 * Avoiding building campfires under hanging branches or over steep slopes, and clear a ten-foot diameter circle around the fire of all flammable debris.
 * Having enough water nearby and a shovel to smother an out-of-control fire with dirt.
 * Minimizing the size of the fire to prevent problems from occurring.
 * Never leaving a campfire unattended.
 * When extinguishing a campfire, using plenty of water or dirt, then stirring the mixture and add more water, then check that there are no burning embers left whatsoever.
 * Never bury hot coals, as they can continue to burn and cause root fires or wildfires. Be aware of roots if digging a hole for your fire.
 * Making sure the fire pit is large enough for the campfire and there are no combustibles near the campfire, and avoiding the construction of the campfire on a windy day.

Types of fuel
There are three types of material involved in building a fire without manufactured fuels or modern conveniences such as lighters:

 * 1) Tinder lights easily and is used to start an enduring campfire. It is anything that can be lit with a spark and is usually classified as being thinner than your little finger. The tinder of choice before matches and lighters was amadou next to flint and steel. A few decent natural tinders are cotton, birch bark, cedar bark, and fatwood, where available; followed by dead, dry pine needles or grass; a more comprehensive list is given in the article on tinder. Though not natural steel wool make excellent tinder and can be started with steel and flint, or a 9 volt battery without difficulty.
 * 2) Kindling wood is an arbitrary classification including anything bigger than tinder but smaller than fuel wood. In fact, there are gradations of kindling, from sticks thinner than a finger to those as thick as a wrist. A quantity of kindling sufficient to fill a hat may be enough, but more is better. A faggot is a related term indicating a bundle of small branches used to feed a small fire or continue developing a bigger fire out of a small one.
 * 3) Fuel wood can be different types of timber. Timber ranges from small logs two or three inches (76 mm) across to larger logs that can burn for hours. It is typically difficult to gather without a hatchet or other cutting tool. In heavily used campsites, fuel wood can be hard to find, so it may have to purchased at a nearby store or be brought from home. However, untreated wood should not be transported due to the probability that invasive species of bugs will be transported with it. Heat-treated wood such as kiln-dried lumber is safe to transport. In the United States, areas that allow camping, like state parks and national parks, often let campers collect firewood lying on the ground. Some parks do not do this for various reasons, e.g. if they have erosion problems from campgrounds near dunes. Parks almost always forbid cutting living trees, and may also prohibit collecting dead parts of standing trees.

In most realistic cases nowadays, non-natural additions to the fuels mentioned above will be used. Often, charcoal lighters like hexamine fuel tablets or ethyl alcohol will be used to start the fire, as well as various types of scrap paper. With the proliferation of packaged food, it is quite likely that plastics will be incinerated as well, a practice that not only produces toxic fumes but will also leave polluted ashes behind because of incomplete combustion at too-low open fire temperatures.

Construction styles
There are a variety of designs to choose from in building a campfire. A functional design is important in the early stages of a fire. Most of them make no mention of fuelwood—in most designs, fuelwood is never placed on a fire until the kindling is burning strongly.

Teepee
The tipi (or teepee) fire-build takes some patience to construct. First, the tinder is piled up in a compact heap. The smaller kindling is arranged around it, like the poles of a tipi. For added strength, it may be possible to lash some of the sticks together. A tripod lashing is quite difficult to execute with small sticks, so a clove hitch should suffice. (Synthetic rope should be avoided since it produces pollutants when it burns.) Then the larger kindling is arranged above the smaller kindling, taking care not to collapse the tipi. A separate tipi as a shell around the first one may work better. Tipi fires are excellent for producing heat to keep people warm. The gases from the bottom quickly come to the top as you add more sticks.

One downside to a Tipi fire is that when it burns, the logs become unstable and can fall over. This is especially concerning with a large fire.

Log cabin
A log cabin fire-build likewise begins with a tinder pile. The kindling is then stacked around it, as in the construction of a log cabin. The first two kindling sticks are laid parallel to each other, on opposite sides of the tinder pile. The second pair is laid on top of the first, at right angles to it, and also on opposite sides of the tinder. More kindling is added in the same manner. The smallest kindling is placed over the top of the assembly. Of all the fire-builds, the log cabin is the least vulnerable to premature collapse, but it is also inefficient because it makes the worst use of convection to ignite progressively larger pieces of fuel. However, these qualities make the log cabin an ideal cooking fire as it burns for a long period of time and can support cookware.

A variation on the log cabin starts with two pieces of fuelwood with a pile of tinder between them, and small kindling laid over the tops of the logs, above the tinder. The tinder is lit, and the kindling is allowed to catch fire. When it is burning briskly, it is broken and pushed down into the consumed tinder, and the larger kindling is placed over the top of the logs. When that is burning well, it is also pushed down. Eventually, a pile of kindling burns between two pieces of fuelwood, and soon the logs catch fire from it.

Another variation is called the funeral pyre method because it is used for building funeral pyres. Its main difference from the standard log cabin is that it starts with thin pieces and moves up to thick pieces. If built on a large scale, this type of fire-build collapses in a controlled manner without restricting the airflow.

Hybrid
A hybrid fire combines the elements of both the tipi and the log cabin creating an easily lit yet stable fire structure. The hybrid is made by first erecting a small tipi and then proceeding to construct a log cabin around it. This fire structure combines benefits of both fire types: the tipi allows the fire to ignite easily and the log cabin sustains the fire for a long time.

Cross-fire
A cross-fire is built by positioning two pieces of wood with the tinder in between. Once the fire is burning well, additional pieces of wood are placed on top in layers that alternate directions. This type of fire creates coals suitable for cooking.

Lean-to
A lean-to fire-build starts with the same pile of tinder as the tipi fire-build. Then, a long, thick piece of kindling is driven into the ground at an angle, so that it overhangs the tinder pile. The smaller pieces of kindling are leaned against the big stick so that the tinder is enclosed between them.

In an alternative method, a large piece of fuelwood or log can be placed on the ground next to the tinder pile. Then kindling is placed with one end propped up by the larger piece of fuelwood, and the other resting on the ground so that the kindling is leaning over the tinder pile. This method is useful in very high winds, as the piece of fuel wood acts as a windbreak.

Rakovalkea
The traditional Finnish rakovalkea (lit. 'slit bonfire'), or nying in Scandinavian languages, also called by English terms long log fire or gap fire, is constructed by placing one long and thick piece of fuelwood (log) atop another, parallel, and bolstering them in place with four sturdy posts driven into the ground. Traditionally, whole un-split tree trunks provide the fuelwood. Kindling and tinder are placed between the logs in sufficient quantity (while avoiding the very ends) to raise the upper log and allow ventilation. The tinder is always lit at the center so the bolstering posts near the ends do not burn prematurely.

The rakovalkea has two significant features. First, it burns slowly but steadily when lit; it does not require arduous maintenance, but burns for a very long time. A well constructed rakovalkea of two thick logs of two meters in length can warm two lean-to shelters for a whole sleeping shift. The construction causes the logs themselves to protect the fire from the wind. Thus, exposure to smoke is unlikely for the sleepers; nevertheless someone should always watch in case of an emergency. Second, it can be easily scaled to larger sizes (for a feast) limited only by the length of available tree trunks. The arrangement is also useful as beacon fire, i.e. a temporary light signal for ships far in the sea.

Swedish torch
The Swedish torch (Schwedenfackel or Schwedenfeuer) is also known by other names, including Swedish (log) candle, and Swedish log stove.

This fire is unique because it uses only one piece of fair-sized wood as its fuel. The log is either cut (usually only partially, but other variants do include totally splitting) and then set upright (ideally, the log needs to be cut evenly and on a level surface for stability). Tinder and kindling are added to the preformed chamber, from the initial cuts. Eventually, the fire is self-feeding. The flat, circular top provides a surface to place a kettle, or pan for cooking, boiling liquids, etc. The elevated position of the fire can serve as a better beacon than the typical ground-based campfire in some instances.

Keyhole fire
A keyhole fire is made in a keyhole-shaped fire ring, and is used in cooking. The large round area is used to build a fire to create coals. As coals develop, they are scraped into the rectangular area used for cooking.

Top lighter
A "top lighter" fire is built similar to a log cabin or pyre, but instead of the tinder and kindling being placed inside the cabin, it is placed in a tipi on top. The small tipi is lighted on top, and the coals eventually fall down into the log cabin. Outdoor youth organizations often build these fires for "council fires" or ceremonial fires. They burn predictably, and with some practice a builder can estimate how long they will last. They also do not throw off much heat, which isn't needed for a ceremonial fire. The fire burns from the top down, with the layer of hot coals and burning stubs igniting the next layer down.

Another variation to the top lighter, log cabin, or pyre is known by several names, most notably the pyramid, self-feeding, and upside-down [method]. The reasoning for this method are twofold. First, the layers of fuelwood take in the heat from the initial tinder/kindling, therefore, it is not lost to the surrounding ground. In effect, the fire is "off the ground", and burns its way down through its course. And secondly, this fire type requires minimal labor, thereby making it ideal as a fire of choice before bedding down for the evening without having to get up periodically to add fuelwood and/or stoke the fire to keep it going. Start by adding the largest fuelwood in a parallel "layer", then continue to add increasingly smaller and smaller fuelwood layers perpendicularly to the last layer. Once enough wood is piled, there should be a decent "platform" to make the tipi [tinder/kindling] to initiate the fire.

Dakota smokeless pit fire
A Dakota smokeless pit fire is a tactical fire used by the United States military as the flame produces a low light signature, reduced smoke, and is easier to ignite under strong wind conditions. Two small holes are dug in the ground: one vertical for the firewood and the other slanted to the bottom of the first hole to provide a draft of air for nearly complete combustion. Optional are flat stones to partially cover the first hole and provide support for cookery, and a tree over the pits to disperse the smoke.

Star Fire
A Star Fire, or Indian Fire, is the fire design often depicted as the campfire of the old West. Someone lays six or so logs out like the spokes of a wheel (star-shaped). They start the fire at the "hub," and push each log towards the center as the flames consume the ends.

Ignition
Once the fire is built, the tinder is lighted, using one of several methods
 * smoking black powder produced by friction between a stick, or bow drill, or pump drill and a hole or crack on dry wood,
 * a magnifying glass focusing sunlight,
 * smoking material produced by a fire piston,
 * smoking black powder produced by a bamboo fire saw
 * smoking material produced by a fire roll (small amount of cotton mixed with ash or iron rust, rolled vigorously between two flat stones or planks, until it starts smoking),
 * smoking material produced by a piece of flint or ferro-rod struck against steel over amadou or other initial tinder, or
 * an ignition device, such as a match or a lighter.

A reasonably skilful fire-builder using reasonably good material only needs one match. The tinder burns brightly, but reduced to glowing embers within half a minute. If the kindling does not catch fire, the fire-builder must gather more tinder, determine what went wrong and try to fix it.

One of five problems can prevent a fire from lighting properly: wet wood, wet weather, too little tinder, too much wind, or a lack of oxygen. Rain will douse a fire, but a combination of wind and fog also has a stifling effect. Metal fire rings generally do a good job of keeping out wind, but some of them are so high as to impede the circulation of oxygen in a small fire. To make matters worse, these tall fire rings also make it very difficult to blow on the fire properly.

A small, enclosed fire that has slowed down may require vigorous blowing to get it going again, but excess blowing can extinguish a fire. Most large fires easily create their own circulation, even in unfavourable conditions, but the variant log-cabin fire-build suffers from a chronic lack of air so long as the initial structure is maintained.

Once large kindling is burning, all kindling is placed in the fire, then the fuel wood is placed on top of it (unless, as in the rakovalkea fire-build, it is already there).

Activities
Campfires have been used for cooking since time immemorial. Possibly the simplest method of cooking over a campfire and one of the most common is to roast food on long skewers that can be held above red glowing embers, or on the side near the flames (not over flames in order to avoid soot contamination and burnt food). This is a popular technique for cooking hot dogs or toasting marshmallows for making s'mores. This type of cooking over the fire typically consists of comfort foods that are easy to prepare. There is also no clean up involved unlike an actual kitchen. Another technique is to use pie irons—small iron molds with long handles. Campers put slices of bread with some kind of filling into the molds and put them over hot coals to cook. Campers sometimes use elaborate grills, cast iron pots, and fire irons to cook. Often, however, they use portable stoves for cooking instead of campfires.

Other practical, though not commonly needed, applications for campfires include drying wet clothing, alleviating hypothermia, and distress signaling. Most campfires, though, are exclusively for recreation, often as a venue for conversation, storytelling, or song. Another traditional campfire activity involves impaling marshmallows on sticks or uncoiled wire coat hangers, and roasting them over the fire. Roasted marshmallows may also be used for s'mores.

Dangers
Beside the danger of people receiving burns from the fire or embers, campfires may spread into a larger fire. A campfire may burn out of control in two basic ways: on the ground or in the trees. Dead leaves or pine needles on the ground may ignite from direct contact with burning wood, or from thermal radiation. If a root, particularly a dead one, is exposed to fire, it may smoulder underground and ignite the parent tree long after the original fire is doused and the campers have left the area. Alternatively, airborne embers (or their smaller kin, sparks) may ignite dead material in overhanging branches. This latter threat is less likely, but a fire in a branch is extremely difficult to put out without firefighting equipment, and may spread more quickly than a ground fire.

Embers may simply fall off logs and float away in the air, or exploding pockets of sap may eject them at high speed. With these dangers in mind, some places prohibit all open fires, particularly at times prone to wildfires.

Many public camping areas prohibit campfires. Public areas with large tracts of woodland usually have signs that indicate the fire danger level, which usually depends on recent rain and the amount of deadfall or dry debris. Even in safer times, it is common to require registration and permits to build a campfire. Such areas are often kept under observation by rangers, who will dispatch someone to investigate any unidentified plume of smoke.

Extinguishing the fire
Leaving a fire unattended can be dangerous. Any number of accidents might occur in the absence of people, leading to property damage, personal injury or possibly a wildfire. Ash is a good insulator, so embers left overnight only lose a fraction of their heat. It is often possible to restart the new day's fire using the embers.

To properly cool a fire, water is splashed on all embers, including places that are not glowing red. Splashing the water is both more effective and efficient in extinguishing the fire. The water boils violently and carries ash in the air with it, dirtying anything nearby but not posing a safety hazard. Water is continuously poured until the hissing stops, then the ashes are stirred to ensure that water reaches the entire fire, and more water is added if necessary. When the fire is fully extinguished, the ashes are cool to the touch.

If water is scarce, sand is used to deprive the fire of oxygen. Sand works well, but is less effective than water at absorbing heat. Once the fire is covered thoroughly with sand, water is then added over the fire.

When winter or "snow" camping with an inch or more of snow on the ground, neither of the above protocols are necessary—simply douse visible flames before leaving. In lightly used wilderness areas, the area around the campfire is cleaned up to make it look untouched after the fire is extinguished.

Campfire ashes are sometimes used in ceremonies like the Scouting campfire ash ceremony.

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Magnetic susceptibility

In electromagnetism, the magnetic susceptibility (denoted $χ$, chi) is a measure of how much a material will become magnetized in an applied magnetic field. It is the ratio of magnetization $M$ (magnetic moment per unit volume) to the applied magnetic field intensity $H$. This allows a simple classification, into two categories, of most materials' responses to an applied magnetic field: an alignment with the magnetic field, $χ > 0$, called paramagnetism, or an alignment against the field, $χ < 0$, called diamagnetism.

Magnetic susceptibility indicates whether a material is attracted into or repelled out of a magnetic field. Paramagnetic materials align with the applied field and are attracted to regions of greater magnetic field. Diamagnetic materials are anti-aligned and are pushed away, toward regions of lower magnetic fields. On top of the applied field, the magnetization of the material adds its own magnetic field, causing the field lines to concentrate in paramagnetism, or be excluded in diamagnetism. Quantitative measures of the magnetic susceptibility also provide insights into the structure of materials, providing insight into bonding and energy levels. Furthermore, it is widely used in geology for paleomagnetic studies and structural geology.

The magnetizability of materials comes from the atomic-level magnetic properties of the particles of which they are made. Usually, this is dominated by the magnetic moments of electrons. Electrons are present in all materials, but without any external magnetic field, the magnetic moments of the electrons are usually either paired up or random so that the overall magnetism is zero (the exception to this usual case is ferromagnetism). The fundamental reasons why the magnetic moments of the electrons line up or do not are very complex and cannot be explained by classical physics. However, a useful simplification is to measure the magnetic susceptibility of a material and apply the macroscopic form of Maxwell's equations. This allows classical physics to make useful predictions while avoiding the underlying quantum mechanical details.

Volume susceptibility
Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetization of a material in response to an applied magnetic field. A related term is magnetizability, the proportion between magnetic moment and magnetic flux density. A closely related parameter is the permeability, which expresses the total magnetization of material and volume.

The volume magnetic susceptibility, represented by the symbol $ξ$ (often simply $χ_{v}$, sometimes $χ$ – magnetic, to distinguish from the electric susceptibility), is defined in the International System of Units – in other systems there may be additional constants – by the following relationship:

$$\mathbf{M} = \chi_\text{v} \mathbf{H}.$$

Here,
 * $χ_{m}$ is the magnetization of the material (the magnetic dipole moment per unit volume), with unit amperes per meter, and
 * $M$ is the magnetic field strength, also with the unit amperes per meter.

$H$ is therefore a dimensionless quantity.

Using SI units, the magnetic induction $χ_{v}$ is related to $B$ by the relationship

$$\mathbf{B} \ = \ \mu_0\left(\mathbf{H} + \mathbf{M}\right) \ = \ \mu_0\left(1 + \chi_\text{v}\right) \mathbf{H} \ = \ \mu \mathbf{H}$$

where $H$ is the vacuum permeability (see table of physical constants), and $μ_{0}$ is the relative permeability of the material. Thus the volume magnetic susceptibility $(1 + χ_{v})$ and the magnetic permeability $χ_{v}$ are related by the following formula: $$\mu = \mu_0\left(1 + \chi_\text{v}\right).$$

Sometimes an auxiliary quantity called intensity of magnetization $μ$ (also referred to as magnetic polarisation $I$) and with unit teslas, is defined as $$\mathbf{I} = \mu_0 \mathbf{M} .$$

This allows an alternative description of all magnetization phenomena in terms of the quantities $J$ and $I$, as opposed to the commonly used $B$ and $M$.

Molar susceptibility and mass susceptibility
There are two other measures of susceptibility, the molar magnetic susceptibility ($H$) with unit m3/mol, and the mass magnetic susceptibility ($χ_{m}$) with unit m3/kg that are defined below, where $χ_{ρ}$ is the density with unit kg/m3 and $ρ$ is molar mass with unit kg/mol: $$\begin{align} \chi_\rho &= \frac{\chi_\text{v}}{\rho}; \\ \chi_\text{m} &= M\chi_\rho = \frac{M}{\rho} \chi_\text{v}. \end{align}$$

In CGS units
The definitions above are according to the International System of Quantities (ISQ) upon which the SI is based. However, many tables of magnetic susceptibility give the values of the corresponding quantities of the CGS system (more specifically CGS-EMU, short for electromagnetic units, or Gaussian-CGS; both are the same in this context). The quantities characterizing the permeability of free space for each system have different defining equations: $$\mathbf{B}^\text{CGS} = \mathbf{H}^\text{CGS} + 4\pi\mathbf{M}^\text{CGS} = \left(1 + 4\pi\chi_\text{v}^\text{CGS}\right) \mathbf{H}^\text{CGS} .$$

The respective CGS susceptibilities are multiplied by 4$\pi$ to give the corresponding ISQ quantities (often referred to as SI quantities) with the same units: $$\chi_\text{m}^\text{SI} = 4\pi\chi_\text{m}^\text{CGS}$$ $$\chi_\text{ρ}^\text{SI} = 4\pi\chi_\text{ρ}^\text{CGS}$$ $$\chi_\text{v}^\text{SI} = 4\pi\chi_\text{v}^\text{CGS}$$

For example, the CGS volume magnetic susceptibility of water at 20 °C is $0$, which is $0$ using the SI convention, both quantities being dimensionless. Whereas for most electromagnetic quantities, which system of quantities it belongs to can be disambiguated by incompatibility of their units, this is not true for the susceptibility quantities.

In physics it is common to see CGS mass susceptibility with unit cm3/g or emu/g⋅Oe−1, and the CGS molar susceptibility with unit cm3/mol or emu/mol⋅Oe−1.

Paramagnetism and diamagnetism
If $M$ is positive, a material can be paramagnetic. In this case, the magnetic field in the material is strengthened by the induced magnetization. Alternatively, if $χ$ is negative, the material is diamagnetic. In this case, the magnetic field in the material is weakened by the induced magnetization. Generally, nonmagnetic materials are said to be para- or diamagnetic because they do not possess permanent magnetization without external magnetic field. Ferromagnetic, ferrimagnetic, or antiferromagnetic materials possess permanent magnetization even without external magnetic field and do not have a well defined zero-field susceptibility.

Experimental measurement
Volume magnetic susceptibility is measured by the force change felt upon a substance when a magnetic field gradient is applied. Early measurements are made using the Gouy balance where a sample is hung between the poles of an electromagnet. The change in weight when the electromagnet is turned on is proportional to the susceptibility. Today, high-end measurement systems use a superconductive magnet. An alternative is to measure the force change on a strong compact magnet upon insertion of the sample. This system, widely used today, is called the Evans balance. For liquid samples, the susceptibility can be measured from the dependence of the NMR frequency of the sample on its shape or orientation.

Another method using NMR techniques measures the magnetic field distortion around a sample immersed in water inside an MR scanner. This method is highly accurate for diamagnetic materials with susceptibilities similar to water.

Tensor susceptibility
The magnetic susceptibility of most crystals is not a scalar quantity. Magnetic response $χ$ is dependent upon the orientation of the sample and can occur in directions other than that of the applied field $M$. In these cases, volume susceptibility is defined as a tensor: $$ M_i = H_j \chi_{ij} $$ where $i$ and $j$ refer to the directions (e.g., of the $x$ and $y$ Cartesian coordinates) of the applied field and magnetization, respectively. The tensor is thus degree 2 (second order), dimension (3,3) describing the component of magnetization in the $i$th direction from the external field applied in the $j$th direction.

Differential susceptibility
In ferromagnetic crystals, the relationship between $H$ and $M$ is not linear. To accommodate this, a more general definition of differential susceptibility is used: $$\chi^{d}_{ij} = \frac{\partial M_i}{\partial H_j}$$ where $H$ is a tensor derived from partial derivatives of components of $χd ij$ with respect to components of $M$. When the coercivity of the material parallel to an applied field is the smaller of the two, the differential susceptibility is a function of the applied field and self interactions, such as the magnetic anisotropy. When the material is not saturated, the effect will be nonlinear and dependent upon the domain wall configuration of the material.

Several experimental techniques allow for the measurement of the electronic properties of a material. An important effect in metals under strong magnetic fields, is the oscillation of the differential susceptibility as function of $H$. This behaviour is known as the De Haas–Van Alphen effect and relates the period of the susceptibility with the Fermi surface of the material.

An analogue non-linear relation between magnetization and magnetic field happens for antiferromagnetic materials.

In the frequency domain
When the magnetic susceptibility is measured in response to an AC magnetic field (i.e. a magnetic field that varies sinusoidally), this is called AC susceptibility. AC susceptibility (and the closely related "AC permeability") are complex number quantities, and various phenomena, such as resonance, can be seen in AC susceptibility that cannot occur in constant-field (DC) susceptibility. In particular, when an AC field is applied perpendicular to the detection direction (called the "transverse susceptibility" regardless of the frequency), the effect has a peak at the ferromagnetic resonance frequency of the material with a given static applied field. Currently, this effect is called the microwave permeability or network ferromagnetic resonance in the literature. These results are sensitive to the domain wall configuration of the material and eddy currents.

In terms of ferromagnetic resonance, the effect of an AC-field applied along the direction of the magnetization is called parallel pumping.

Sources of published data
The CRC Handbook of Chemistry and Physics has one of the few published magnetic susceptibility tables. The data are listed as CGS quantities. The molar susceptibility of several elements and compounds are listed in the CRC.

Application in the geosciences
In Earth science, magnetism is a useful parameter to describe and analyze rocks. Additionally, the anisotropy of magnetic susceptibility (AMS) within a sample determines parameters as directions of paleocurrents, maturity of paleosol, flow direction of magma injection, tectonic strain, etc. It is a non-destructive tool which quantifies the average alignment and orientation of magnetic particles within a sample.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Magnetic susceptibility


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Talk:What's Opera, Doc?

Music
Is all the music based on Wagner? I thought there was quite a bit of Rossini in there as well, and maybe some others (it's years since I saw it). Maybe I'm thinking of a different cartoon, though. --Camembert

 * I think there was a Barber of Seville cartoon too. Ortolan88

 * That'll probably be it. Ignore me, I'm losing it. --Camembert

 * That would be the Rabbit of Seville. Another classic --Steve Rapaport 18:29, 23 Apr 2005 (UTC)

One small item not mentioned in the article -- doesn't the score include the "Tristan chord" after Bugs is killed?

Availability
It's now available for purchase in the iTunes Store for $1.99 as part of the Bugs Bunny, Vol. 1 collection. But because it's paired with another episode titled "Bugs Bunny Gets the Boid", it's the second show on the track and doesn't start until 7:26. It's nice to have it on my iPod though. --71.9.124.21 (talk) 09:50, 25 December 2007 (UTC)

it is also avaliable for free streaming on the main looney tune website along with a few other that have been deemed as cultrally significant. i have personally copied it to other media for historical preservation and for use as a teaching aid when refrencing the impact of old cartoons on a generation and how it does not affect the mindset. I suspect however that while it is free to watch and there is nothing listed or done to prevent from downloading they may not exactly like people downloading the stream. — Preceding unsigned comment added by 152.91.9.153 (talk) 21:57, 6 September 2012 (UTC)

Elmer's reaction
Why is Elmer sad for "killing the wabbit" when that was his plan the entire time? He was the same way in The Old Grey Hare, when he shoots Old Bugs. NBK1122 (talk) 01:49, 1 March 2008 (UTC)

Other than asking those that conceived and created the character of Elmer Fudd and his personality, one has to assume that since this is a cartoon, and reality isn't a factor, aside from deep psychological evaluations, it's just funny. Elmer is the "mighty hunter" who turns out to be a softy once he actually accomplishes his "misson". "Hunter's Remorse" perhaps, which is the twist that makes for the humor. The once overly armed hunter with his shotgun, or in this case, "spear and magic hewmet" which is infinitely more powerful than his standard firearm, having taken his revenge, now weeps pitiously over his victim. It's Opera, doc! Greenbomb101 (talk) 20:36, 25 April 2008 (UTC)

"SMOG! vs. SCHMUCK!
The text of the article states that when Bugs Bunny's headdress falls off, Elmer becomes enraged, prompting him to command fierce lightning, "typhoons, hurricanes, earthquakes" and, finally, "SMOG!!!" This may well have been the interpretation of the cartoon's words as told to censors and others, but a careful listening, and comparision with the object being parodied, Der Ring des Nibelungen, that the creators wanted to satirize the use of "Götterdämmerung" in Der Ring des Nibelungen. But instead of using a profanity that would be trapped by the censors, they used the borrowed-from-yiddish term "schmuck." Mumon7 (talk) 19:30, 21 November 2009 (UTC)

 * I recently watched the Golden Anniversary DVD for this cartoon, including all the audio commentaries, and could have sworn they described Mel Blanc saying SMOKE!!! I'll watch with closed captioning and see if that will help settle the debate.  Hoof Hearted (talk) 18:54, 15 January 2010 (UTC)

 * Never mind. According to the closed captioning the line is indeed SMOG!!!  Hoof Hearted (talk) 03:31, 16 January 2010 (UTC)

"enormously fat" (the white horse)
Isn't that redundant? NBK1122 (talk) 01:51, 1 March 2008 (UTC)
 * Since fatness occurs by degrees, no. Legionaireb (talk) 16:34, 20 April 2012 (UTC)
 * Let's face it, the Bugs Bunny entrance on the fat horse, and the dance were stolen from Herr meets Hare. — Preceding unsigned comment added by 74.101.160.41 (talk) 14:16, 2 May 2013 (UTC)
 * I've seen both of the cartoons many times, but don't have a copy of either. I'm not completely sure, but I think it's the same horse in both.  If so, this would be a good addition, both here and in the article for Herr Meets Hare.JDZeff (talk) 23:50, 24 July 2014 (UTC)

Academy Award (or lack thereof)
Who cares if the cartoon was not nominated for an Academy Award? It has still stood the test of time. Please, whoever you are, stop inserting "despite not earning an Academy Award nomination" into the article; it's essentially meaningless. Icarus of old (talk) 17:31, 3 July 2008 (UTC)

Maurice Nomidad
Yeah in this article you say in the plot section that the set design was brilliant. This is unbiased information. You are not quoting the words of critic or the cartoon has not won an award for brilliance or anything like that. You are simply stating your own oppinion. This is not allowded. You are supposed to keep a biased point of view only explaining the scenes not actually giving your own thougts about them. Not to be rude but your oppinion does not matter. I would consider removing this information at once. -James Pandora Adams —Preceding unsigned comment added by 71.176.152.59 (talk) 01:25, 18 April 2011 (UTC)

Alternate Voice Track
I clearly remember seeing a version of this cartoon in which Elmer's cry of 'SMOG' is said in his normal voice, rather than in Arthur Bryan's, although I haven't seen that version in ages. Does anyone else have this recollection and if so, can someone find a source for it? Legionaireb (talk) 16:50, 29 June 2011 (UTC)

Bibliography: dead link
The thomasvillecentral.com domain expired and is now in the hands of cybersquatters. I would have fixed it but I don't know how, sorry. — Preceding unsigned comment added by 65.73.181.186 (talk) 00:49, 21 May 2017 (UTC)

External links modified
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Rikard?
Sorry, but Richard isn’t pronounced ”Rikard” in German.94.191.152.0 (talk) 22:40, 16 July 2018 (UTC)

title: Talk:What's Opera, Doc?


text:
The Goldbergs (broadcast series)

The Goldbergs is a comedy-drama broadcast from 1929 to 1946 on American radio, and from 1949 to 1956 on American television. It was adapted into a 1948 play, Me and Molly; a 1950 film The Goldbergs, and a 1973 Broadway musical, Molly. It also briefly spun off a comic strip from June 8, 1944, to December 21, 1945, with art by Irwin Hasen, a comic book artist who worked on various DC Comics titles and would later do the Dondi comic strip.

Radio
The program was devised by writer-actress Gertrude Berg in 1928 and sold to the NBC radio network the following year. It was a domestic comedy featuring the home life of a Jewish family, supposedly located at 1038 East Tremont Avenue in the Bronx. In addition to writing the scripts and directing each episode, Berg starred as bighearted, lovingly meddlesome, and somewhat stereotypical Jewish matriarch Molly Goldberg. The show began as a portrait of Jewish tenement life before later evoking such growing pains as moving into a more suburban setting and struggling with assimilation while sustaining their roots.

The Goldbergs began as a weekly 15-minute program called The Rise of the Goldbergs on November 20, 1929, going daily in 1931. The series moved to CBS in 1936 with the title shortened to The Goldbergs. Like other 15-minute comedies of the day, such as Amos 'n' Andy, Lum and Abner, Easy Aces, Vic and Sade and Myrt and Marge, The Goldbergs was a serial with running storylines. Berg's usual introduction (in character as Molly, hollering); "yoo-hoo! Is anybody...?" became a catchphrase. In the 1940s, this was followed by Bud Collyer announcing; "here she is, folks: that's Molly Goldberg, a woman with a place in every heart and a finger in every pie".

When Gertrude Berg missed a couple of weeks due to illness, stations carrying the popular show were flooded with get-well mail. At the height of the show's popularity, Life wrote: "for millions of Americans, listening to The Goldbergs... has been a happy ritual akin to slipping on a pair of comfortable old shoes that never seem to wear out".

Radio historians Frank Buxton and Bill Owen, in The Big Broadcast 1920–1950, noted the series (which they considered a soap opera as much as a comedy) "differed from most of the other 'soaps' in that its leading characters lived through relatively normal situations. Even though it was the story of a poor Jewish family in the Bronx, New York, it had identification for a wide segment of listeners". Of the 15-minute serial comedies, only Amos 'n' Andy enjoyed a longer radio life than The Goldbergs.

The role of husband Jake Goldberg was originally played by Himan Brown and later, James R. Waters. When Waters died suddenly in 1945, Berg resisted recasting the role. Instead, she simply had Molly refer to Jake, occasionally setting up dialogue in which his reply was not heard when she spoke to him.

Behind the scenes
Berg was not averse to incorporating serious real-world issues which affected Jewish families. One 1939 episode addressed Kristallnacht and Nazi Germany (including a rock through the family window as the Goldbergs had their Passover Seder); other World War II-era episodes alluded to friends or family members trying to escape the Holocaust. But these were sporadic deviations from the show's main theme of family, neighborhood and the balance between old world values and new world assimilation. Molly demonstrates to the audience the strong matriarch she is by constantly helping others with their dilemmas and proving to be the hero time and time again.

The Goldbergs was so popular that performing stars in other arts sought to appear on it. Berg cast Metropolitan Opera star Jan Peerce almost annually to sing on Yom Kippur and Passover. Another famous singer of the day, Ernestine Schumann-Heink, asked Berg personally to appear, and Berg wrote her into three episodes. Regina Resnik (an international soprano, later mezzo who had an international career, including the Met Opera) starred in a TV episode. The radio cast included Roslyn Silber and Alfred Ryder as children Rosalie and Sammy, Menasha Skulnik as Uncle David, Arnold Stang as Seymour Fingerhood, Garson Kanin as Eli Edwards, and Zina Provendie as Sylvia Allison, among others.

Moves into stage and television
In 1948, Berg wrote and staged Me and Molly, a Broadway version of the show. A year later, she brought The Goldbergs to a national audience on television.

Television
The television version ran on CBS Television from 1949 to 1951 and co-starred Philip Loeb as Jake Goldberg. He and Gertrude Berg reprised their roles in a 1950 film of the same name. The show almost didn't get to the small screen at all: CBS executives were uncertain that the show would work on television as well as it did on radio. Berg prevailed, however, and picked up General Foods (Sanka coffee) as its sponsor. Berg, who continued to write every episode, insisted that no studio audience be used and made sure everyday events formed the base for the stories; she was once quoted as saying she avoided "anything that will bother people ... unions, fund raising, Zionism, socialism, intergroup relations. ... I keep things average. I don't want to lose friends." Berg's hard work and determination paid off. In 1950, she won the first Best Actress Emmy Award for her role as Molly on The Goldbergs.

The Goldbergs was destined to spend almost a decade on television—but not without disruptions. In 1950, Philip Loeb was blacklisted and pressure was placed on Berg (who owned the television version as she had the radio original) to fire him. When she refused, General Foods cancelled their sponsorship, and CBS dropped it from their schedule by June 1951.

Eight months later, however, NBC—the show's original broadcasting home—picked up the series for the 1952–53 season, but informed Gertrude Berg that if she persisted in allowing Philip Loeb to remain with the series, it would never be seen on television again. She finally gave in, and the series reappeared in a twice-weekly, early-evening 15-minute format (with another change in title, to Molly, in due course), with Harold Stone and then Robert H. Harris replacing Loeb as Jake, though Berg quietly continued to pay a salary to Loeb. After The Goldbergs ended its CBS run, Tom Taylor replaced Larry Robinson in the role of Molly's son, Sammy. The rest of the television cast included Eli Mintz as Uncle David, Arlene McQuade as Rosalie and Betty Bendyke as Dora Barnett. On radio, Sammy and Rosalie had grown up and gotten married; on television, the characters were revived as teenagers. During this time, Gertrude Berg and Arlene McQuade appeared as their characters of Molly and Rosalie, respectively, when they guested on NBC-TV's Buick-Berle Show starring Milton Berle.

In 1954, the show reverted to a weekly half-hour, moving to the DuMont network for a run from April to October. The series was originally intended to run for six months on DuMont, but, due to financial difficulties, the network was unable to fulfill the $5 million contract, despite Nielsen ratings estimated at ten million viewers. The DuMont shows were aired live.

A final version, aired in syndication, was filmed in 1955 and aired on local stations until 1956. This version moved the Goldbergs from the Bronx to the New York suburb of Haverville. In a way this mirrored the real life journey of many Jewish families from the Bronx to the suburbs and other parts of New York during this period. However, this was considered the death knell of the show, as it was felt that the Goldbergs were only the Goldbergs in the Bronx. Also in 1955, Philip Loeb, beset by depression and unable to find other work, committed suicide. In 1957, Gertrude Berg made her last two appearances as Molly Goldberg: first on an episode of the NBC-TV variety series Washington Square with Ray Bolger, and then on a Kate Smith special that aired on ABC-TV.

Aftermath
Gertrude Berg returned to television six years later in a situation comedy, Mrs. G. Goes to College, playing Sarah Green, a Molly Goldberg-like character. Despite being retitled The Gertrude Berg Show in mid-year, the program was cancelled after one season. The Goldbergs is available to collectors and fans in a large number of surviving radio episodes and some surviving television episodes, many of which have lapsed into the public domain. Aviva Kempner's documentary Yoo-Hoo, Mrs. Goldberg (2009) deals with the show, and to an extent, Gertrude Berg's personal life.

Most of the DuMont episodes survive at the UCLA Film and Television Archive, while the 39 filmed episodes survive intact.

Since 2009, the series can be seen on the JLTV cable network.

Home media
In March 2010, Shout! Factory released The Goldbergs: The Ultimate Goldbergs on DVD via their retail website. The release includes all 71 extant episodes of the television series. Episodes are also available to stream on their ShoutFactoryTV service.

The UCLA Film and Television Archive digitally restored all of the episodes, as well as provided 12 radio episodes for the DVD release and the pilot for the short lived series Mrs. G Goes To College (1961). The box set is available from UCLA. The UCLA archive also holds 130 transcription discs of the radio series, which it has released on YouTube.

Listen to

 * Internet Archive: The Goldbergs
 * Webcast on Gertrude Berg, The Paley Center for Media, "From The Goldbergs to 2005: The Evolution of the Family Sitcom" (November 16, 2005)
 * Free OTR: The Goldbergs (59 episodes)

title: The Goldbergs (broadcast series)


text:
Shipbuilding

Shipbuilding is the construction of ships and other floating vessels. In modern times, it normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history.

Until recently, with the development of complex non-maritime technologies, a ship has often represented the most advanced structure that the society building it could produce. Some key industrial advances were developed to support shipbuilding, for instance the sawing of timbers by mechanical saws propelled by windmills in Dutch shipyards during the first half of the 17th century. The design process saw the early adoption of the logarithm (invented in 1615) to generate the curves used to produce the shape of a hull, especially when scaling up these curves accurately in the mould loft.

Shipbuilding and ship repairs, both commercial and military, are referred to as naval engineering. The construction of boats is a similar activity called boat building.

The dismantling of ships is called ship breaking.

The earliest evidence of maritime transport by modern humans is the settlement of Australia between 50,000 and 60,000 years ago. This almost certainly involved rafts, possibly equipped with some sort of sail. Much of the development beyond that raft technology occurred in the "nursery" areas of the Mediterranean and in Maritime Southeast Asia. Favoured by warmer waters and a number of inter-visible islands, boats (and, later, ships) with water-tight hulls (unlike the "flow through" structure of a raft) could be developed. The ships of ancient Egypt were built by joining the hull planks together, edge to edge, with tenons set in mortices cut in the mating edges. A similar technique, but with the tenons being pinned in position by dowels, was used in the Mediterranean for most of classical antiquity. Both these variants are "shell first" techniques, where any reinforcing frames are inserted after assembly of the planking has defined the hull shape. Carvel construction then took over in the Mediterranean. Northern Europe used clinker construction, but with some flush-planked ship-building in, for instance, the bottom planking of cogs. The north-European and Mediterranean traditions merged in the late 15th century, with carvel construction being adopted in the North and the centre-line mounted rudder replacing the quarter rudder of the Mediterranean. These changes broadly coincided with improvements in sailing rigs, with the three masted ship becoming common, with square sails on the fore and main masts, and a fore and aft sail on the mizzen.

Ship-building then saw a steady improvement in design techniques and introduction of new materials. Iron was used for more than fastenings (nails and bolts) as structural components such as iron knees were introduced, with examples existing in the mid-18th century and from the mid-19th century onwards. This was partly led by the shortage of "compass timber", the naturally curved timber that meant that shapes could be cut without weaknesses caused by cuts across the grain of the timber. Ultimately, whole ships were made of iron and, later, steel.

Pre-history
The earliest known depictions (including paintings and models) of shallow-water sailing boats is from the 6th to 5th millennium BC of the Ubaid period of Mesopotamia. They were made from bundled reeds coated in bitumen and had bipod masts. They sailed in shallow coastal waters of the Persian Gulf.

Ancient Egypt
Evidence from Ancient Egypt shows that the early Egyptians knew how to assemble planks of wood into a ship hull as early as 3100 BC. Egyptian pottery as old as 4000 BC shows designs of early fluvial boats or other means for navigation. The Archaeological Institute of America reports that some of the oldest ships yet unearthed are known as the Abydos boats. These are a group of 14 ships discovered in Abydos that were constructed of wooden planks which were "sewn" together. Discovered by Egyptologist David O'Connor of New York University, woven straps were found to have been used to lash the planks together, and reeds or grass stuffed between the planks helped to seal the seams. Because the ships are all buried together and near a mortuary belonging to Pharaoh Khasekhemwy, originally they were all thought to have belonged to him, but one of the 14 ships dates to 3000 BC, and the associated pottery jars buried with the vessels also suggest earlier dating. The ship dating to 3000 BC was about 75 feet (23 m) long and is now thought to perhaps have belonged to an earlier pharaoh. According to professor O'Connor, the 5,000-year-old ship may have even belonged to Pharaoh Aha.

Austronesia
The Austronesian expansion, which began c. 3000 BC with migration from Taiwan to the island of Luzon in the Philippines, spread across Island Southeast Asia. Then, between 1500 BC and 1500 AD they settled uninhabited islands of the Pacific, and also sailed westward to Madagascar. This is associated with distinctive maritime technology: lashed lug construction techniques (both in outrigger canoes and in large planked sailing vessels), various types of outrigger and twin-hulled canoes and a range of sailing rigs that included the crab claw sail. The origins of this technology is difficult to date, relying largely on linguistics (studying the words for parts of boats), the written comments of people from other cultures, including the observations of European explorers at the time of first contact and the later more systematic ethnographic observations of the types of craft in use. There is only a small body of archaeological evidence available. Since Island Southeast Asia contained effective maritime transport between its very large number of islands long before Austronesian seafaring, it is argued that Austronesians adopted an existing maritime technology from the existing inhabitants of this region.

Austronesian ships varied from simple canoes to large multihull ships. The simplest form of all ancestral Austronesian boats had five parts. The bottom part consists of a single piece of hollowed-out log. At the sides were two planks, and two horseshoe-shaped wood pieces formed the prow and stern. These were fitted tightly together edge-to-edge with dowels inserted into holes in between, and then lashed to each other with ropes (made from rattan or fiber) wrapped around protruding lugs on the planks. This characteristic and ancient Austronesian boatbuilding practice is known as the "lashed-lug" technique. They were commonly caulked with pastes made from various plants as well as tapa bark and fibres which would expand when wet, further tightening joints and making the hull watertight. They formed the shell of the boat, which was then reinforced by horizontal ribs. Shipwrecks of Austronesian ships can be identified from this construction as well as the absence of metal nails. Austronesian ships traditionally had no central rudders but were instead steered using an oar on one side.

Austronesians traditionally made their sails from woven mats of the resilient and salt-resistant pandanus leaves. These sails allowed Austronesians to embark on long-distance voyaging.

The ancient Champa of Vietnam also uniquely developed basket-hulled boats whose hulls were composed of woven and resin-caulked bamboo, either entirely or in conjunction with plank strakes. They range from small coracles (the o thúng) to large ocean-going trading ships like the ghe mành.

Ancient Egypt
Early Egyptians also knew how to assemble planks of wood with treenails to fasten them together, using pitch for caulking the seams. The "Khufu ship", a 43.6-meter vessel sealed into a pit in the Giza pyramid complex at the foot of the Great Pyramid of Giza in the Fourth Dynasty around 2500 BC, is a full-size surviving example which may have fulfilled the symbolic function of a solar barque. Early Egyptians also knew how to fasten the planks of this ship together with mortise and tenon joints.

Indus Valley
The oldest known tidal dock in the world was built around 2500 BC during the Harappan civilisation at Lothal near the present day Mangrol harbour on the Gujarat coast in India. Other ports were probably at Balakot and Dwarka. However, it is probable that many small-scale ports, and not massive ports, were used for the Harappan maritime trade. Ships from the harbour at these ancient port cities established trade with Mesopotamia. Shipbuilding and boatmaking may have been prosperous industries in ancient India. Native labourers may have manufactured the flotilla of boats used by Alexander the Great to navigate across the Hydaspes and even the Indus, under Nearchos. The Indians also exported teak for shipbuilding to ancient Persia. Other references to Indian timber used for shipbuilding is noted in the works of Ibn Jubayr.

Mediterranean
The ships of Ancient Egypt's Eighteenth Dynasty were typically about 25 meters (80 ft) in length and had a single mast, sometimes consisting of two poles lashed together at the top making an "A" shape. They mounted a single square sail on a yard, with an additional spar along the bottom of the sail. These ships could also be oar propelled. The ocean- and sea-going ships of Ancient Egypt were constructed with cedar wood, most likely hailing from Lebanon.

The ships of Phoenicia seem to have been of a similar design.

Austronesia
Austronesians established the Austronesian maritime trade network at around 1000 to 600 BC, linking Southeast Asia with East Asia, South Asia, the Middle East, and later East Africa. The route later became part of the Spice trade network and the Maritime Silk Road.

China
The naval history of China stems back to the Spring and Autumn period (722 BC–481 BC) of the ancient Chinese Zhou dynasty. The Chinese built large rectangular barges known as "castle ships", which were essentially floating fortresses complete with multiple decks with guarded ramparts. However, the Chinese vessels during this era were essentially fluvial (riverine). True ocean-going Chinese fleets did not appear until the 10th century Song dynasty.

Mediterranean
There is considerable knowledge regarding shipbuilding and seafaring in the ancient Mediterranean.

Austronesia
Large multi-masted seafaring ships of Southeast Asian Austronesians first started appearing in Chinese records during the Han dynasty as the k'un-lun po or kunlun bo ("ship of the k'un-lun [dark-skinned southern people]"). These ships used two types of sail of their invention, the junk sail and tanja sail. Large ships are about 50–60 metres (164–197 ft) long, had 5.2 - 7.8 m tall freeboard, each carrying provisions enough for a year, and could carry 200–1000 people. The Chinese recorded that these Southeast Asian ships were hired for passage to South Asia by Chinese Buddhist pilgrims and travelers, because they did not build seaworthy ships of their own until around the 8–9th century AD.

Austronesians (especially from western Island Southeast Asia) were trading in the Indian Ocean as far as Africa during this period. By around 50 to 500 AD, a group of Austronesians, believed to be from the southeastern coasts of Borneo (possibly a mixed group related to the modern Ma'anyan, Banjar, and/or the Dayak people) crossed the Indian Ocean and colonized Madagascar. This resulted in the introduction of outrigger canoe technology to non-Austronesian cultures in the East African coast.

China
The ancient Chinese also built fluvial ramming vessels as in the Greco-Roman tradition of the trireme, although oar-steered ships in China lost favor very early on since it was in the 1st century China that the stern-mounted rudder was first developed. This was dually met with the introduction of the Han dynasty junk ship design in the same century. The Chinese were using square sails during the Han dynasty and adopted the Austronesian junk sail later in the 12th century. Iconographic remains show that Chinese ships before the 12th century used square sails, and the junk rig of Chinese ships is believed to be developed from tilted sails.

Southern Chinese junks were based on keeled and multi-planked Austronesian ship known as po by the Chinese, from the Old Javanese parahu,  Javanese prau, or Malay perahu – large ship. Southern Chinese junks showed characteristics of Austronesian ships that they are made using timbers of tropical origin, with keeled, V-shaped hull. This is different from northern Chinese junks, which are developed from flat-bottomed riverine boats. The northern Chinese junks were primarily built of pine or fir wood, had flat bottoms with no keel, water-tight bulkheads with no frames, transom (squared) stern and stem, and have their planks fastened with iron nails or clamps.

It was unknown when the Chinese people started adopting Southeast Asian (Austronesian) shipbuilding techniques. They may have been started as early as the 8th century, but the development was gradual and the true ocean-going Chinese junks did not appear suddenly. The word "po" survived in Chinese long after, referring to the large ocean-going junks.

Mediterranean
In September 2011, archeological investigations done at the site of Portus in Rome revealed inscriptions in a shipyard constructed during the reign of Trajan (98–117) that indicated the existence of a shipbuilders guild.

Austronesia
Roughly at this time is the last migration wave of the Austronesian expansion, when the Polynesian islands spread over vast distances across the Pacific Ocean were being colonized by the (Austronesian) Polynesians from Island Melanesia using double-hulled voyaging catamarans. At its furthest extent, there is a possibility that they may have reached the Americas. After the 11th century, a new type of ship called djong or jong was recorded in Java and Bali. This type of ship was built using wooden dowels and treenails, unlike the kunlun bo which used vegetal fibres for lashings.

The empire of Majapahit used jong, built in northern Java, for transporting troops overseas. The jongs were transport ships which could carry 100–2000 tons of cargo and 50–1000 people, 28.99–88.56 meter in length. The exact number of jong fielded by Majapahit is unknown, but the largest number of jong deployed in an expedition is about 400 jongs, when Majapahit attacked Pasai, in 1350.

Europe
Until recently, Viking longships were seen as marking an advance on traditional clinker-built hulls where leather thongs were used to join plank boards. This consensus has recently been challenged. Haywood has argued that earlier Frankish and Anglo-Saxon nautical practice was much more accomplished than had been thought and has described the distribution of clinker vs. carvel construction in Western Europe (see map ). An insight into shipbuilding in the North Sea/Baltic areas of the early medieval period was found at Sutton Hoo, England, where a ship was buried with a chieftain. The ship was 26 m long and 4.3 m wide. Upward from the keel, the hull was made by overlapping nine strakes on either side with rivets fastening the oaken planks together. It could hold upwards of thirty men.

Sometime around the 12th century, northern European ships began to be built with a straight sternpost, enabling the mounting of a rudder, which was much more durable than a steering oar held over the side. Development in the Middle Ages favored "round ships", with a broad beam and heavily curved at both ends. Another important ship type was the galley, which was constructed with both sails and oars.

The first extant treatise on shipbuilding was written c. 1436 by Michael of Rhodes, a man who began his career as an oarsman on a Venetian galley in 1401 and worked his way up into officer positions. He wrote and illustrated a book that contains a treatise on shipbuilding, a treatise on mathematics, much material on astrology, and other materials. His treatise on shipbuilding treats three kinds of galleys and two kinds of round ships.

China
Shipbuilders in the Ming dynasty (1368~1644) were not the same as the shipbuilders in other Chinese dynasties, due to hundreds of years of accumulated experiences and rapid changes in the Ming dynasty. Shipbuilders in the Ming dynasty primarily worked for the government, under command of the Ministry of Public Works.

During the early years of the Ming dynasty, the Ming government maintained an open policy towards sailing. Between 1405 and 1433, the government conducted seven diplomatic Ming treasure voyages to over thirty countries in Southeast Asia, India, the Middle East and Eastern Africa. The voyages were initiated by the Yongle Emperor, and led by the Admiral Zheng He. Six voyages were conducted under the Yongle Emperor's reign, the last of which returned to China in 1422. After the Yongle Emperor's death in 1424, his successor the Hongxi Emperor ordered the suspension of the voyages. The seventh and final voyage began in 1430, sent by the Xuande Emperor. Although the Hongxi and Xuande Emperors did not emphasize sailing as much as the Yongle Emperor, they were not against it. This led to a high degree of commercialization and an increase in trade. Large numbers of ships were built to meet the demand.

The Ming voyages were large in size, numbering as many as 300 ships and 28,000 men. The shipbuilders were brought from different places in China to the shipyard in Nanjing, including Zhejiang, Jiangxi, Fujian, and Huguang (now the provinces of Hubei and Hunan). One of the most famous shipyards was Long Jiang Shipyard (zh:龙江船厂), located in Nanjing near the Treasure Shipyard where the ocean-going ships were built. The shipbuilders could build 24 models of ships of varying sizes.

Several types of ships were built for the voyages, including Shachuan (沙船), Fuchuan (福船) and Baochuan (treasure ship) (宝船). Zheng He's treasure ships were regarded as Shachuan types, mainly because they were made in the treasure shipyard in Nanjing. Shachuan, or 'sand-ships', are ships used primarily for inland transport. However, in recent years, some researchers agree that the treasure ships were more of the Fuchuan type. It is said in vol. 176 of San Guo Bei Meng Hui Bian (三朝北盟汇编) that ships made in Fujian are the best ones. Therefore, the best shipbuilders and laborers were brought from these places to support Zheng He's expedition.

The shipyard was under the command of Ministry of Public Works. The shipbuilders had no control over their lives. The builders, commoner's doctors, cooks and errands had lowest social status. The shipbuilders were forced to move away from their hometown to the shipyards. There were two major ways to enter the shipbuilder occupation: family tradition, or apprenticeship. If a shipbuilder entered the occupation due to family tradition, the shipbuilder learned the techniques of shipbuilding from his family and is very likely to earn a higher status in the shipyard. Additionally, the shipbuilder had access to business networking that could help to find clients. If a shipbuilder entered the occupation through an apprenticeship, the shipbuilder was likely a farmer before he was hired as a shipbuilder, or he was previously an experienced shipbuilder.

Many shipbuilders working in the shipyard were forced into the occupation. The ships built for Zheng He's voyages needed to be waterproof, solid, safe, and have ample room to carry large amounts of trading goods. Therefore, due to the highly commercialized society that was being encouraged by the expeditions, trades, and government policies, the shipbuilders needed to acquire the skills to build ships that fulfil these requirements.

Shipbuilding was not the sole industry utilising Chinese lumber at that time; the new capital was being built in Beijing from approximately 1407 onwards, which required huge amounts of high-quality wood. These two ambitious projects commissioned by Emperor Yongle would have had enormous environmental and economic effects, even if the ships were half the dimensions given in the History of Ming. Considerable pressure would also have been placed on the infrastructure required to transport the trees from their point of origin to the shipyards.

Shipbuilders were usually divided into different groups and had separate jobs. Some were responsible for fixing old ships; some were responsible for making the keel and some were responsible for building the helm.

 * It was the keel that determined the shape and the structure of the hull of Fuchuan Ships. The keel is the middle of the bottom of the hull, constructed by connecting three sections; stern keel, main keel and poop keel. The hull spreads in the arc towards both sides forming the keel.
 * The helm was the device that controls direction when sailing. It was a critical invention in shipbuilding technique in ancient China and was only used by the Chinese for a fairly long time. With a developing recognition of its function, the shape and configuration of the helm was continually improved by shipbuilders. The shipbuilders not only needed to build the ship according to design, but needed to acquire the skills to improve the ships.

After 1477, the Ming government reversed its open maritime policies, enacting a series of isolationist policies in response to piracy. The policies, called Haijin (sea ban), lasted until the end of the Ming dynasty in 1644. During this period, Chinese navigation technology did not make any progress and even declined in some aspect.

Indian Ocean
In the Islamic world, shipbuilding thrived at Basra and Alexandria. The dhow, felucca, baghlah, and the sambuk became symbols of successful maritime trade around the Indian Ocean from the ports of East Africa to Southeast Asia and the ports of Sindh and Hind (India) during the Abbasid period.

Bengal
Mughal Empire had a large shipbuilding industry, which was largely centred in the Bengal Subah. Economic historian Indrajit Ray estimates shipbuilding output of Bengal during the sixteenth and seventeenth centuries at 223,250 tons annually, compared with 23,061 tons produced in nineteen colonies in North America from 1769 to 1771. He also assesses ship repairing as very advanced in Bengal.

Shipbuilding in Bengal was advanced compared to European shipbuilding at the time, with Bengal selling ships to European firms. An important innovation in shipbuilding was the introduction of a flushed deck design in Bengal rice ships, resulting in hulls that were stronger and less prone to leak than the structurally weak hulls of traditional European ships built with a stepped deck design. The British East India Company later duplicated the flushed deck and hull designs of Bengal rice ships in the 1760s, leading to significant improvements in seaworthiness and navigation for European ships during the Industrial Revolution.

West Africa
Documents from 1506, for example, refer to watercraft on the Sierra Leone river carrying 120 men. Others refer to Guinea coast peoples using war canoes of varying sizes – some 70 feet in length, 7–8 feet broad, with sharp pointed ends, rowing benches on the side, and quarterdecks or forecastles build of reeds. The watercraft included miscellaneous facilities, such as cooking hearths, and storage spaces for the crew's sleeping mats.

From the 17th century, some kingdoms added brass or iron cannons to their vessels. By the 18th century, however, the use of swivel cannons on war canoes accelerated. The city-state of Lagos, for instance, deployed war canoes armed with swivel cannons.

Europe
With the development of the carrack, the west moved into a new era of ship construction by building the first regular oceangoing vessels. In a relatively short time, these ships grew to an unprecedented size, complexity, and cost.

Shipyards became large industrial complexes, and the ships built were financed by consortia of investors. These considerations led to the documentation of design and construction practices in what had previously been a secretive trade run by master shipwrights and ultimately led to the field of naval architecture, in which professional designers and draftsmen played an increasingly important role. Even so, construction techniques changed only very gradually. The ships of the Napoleonic Wars were still built more or less to the same basic plan as those of the Spanish Armada of two centuries earlier, although there had been numerous subtle improvements in ship design and construction throughout this period. For instance, the introduction of tumblehome, adjustments to the shapes of sails and hulls, the introduction of the wheel, the introduction of hardened copper fastenings below the waterline, the introduction of copper sheathing as a deterrent to shipworm and fouling, etc.

Industrial Revolution
Though still largely based on pre-industrial era materials and designs, ships greatly improved during the early Industrial Revolution period (1760 to 1825), as "the risk of being wrecked for Atlantic shipping fell by one-third, and of foundering by two thirds, reflecting improvements in seaworthiness and navigation respectively." The improvements in seaworthiness have been credited to "replacing the traditional stepped deck ship with stronger flushed decked ones derived from Indian designs, and the increasing use of iron reinforcement." The design originated from Bengal rice ships, with Bengal being famous for its shipbuilding industry at the time. Iron was gradually adopted in ship construction, initially to provide stronger joints in a wooden hull e.g. as deck knees, hanging knees, knee riders and the other sharp joints, ones in which a curved, progressive joint could not be achieved. One study finds that there were considerable improvements in ship speed from 1750 to 1850: "we find that average sailing speeds of British ships in moderate to strong winds rose by nearly a third. Driving this steady progress seems to be the continuous evolution of sails and rigging, and improved hulls that allowed a greater area of sail to be set safely in a given wind. By contrast, looking at every voyage between the Netherlands and East Indies undertaken by the Dutch East India Company from 1595 to 1795, we find that journey time fell only by 10 percent, with no improvement in the heavy mortality, averaging six percent per voyage, of those aboard."

Initially copying wooden construction traditions with a frame over which the hull was fastened, Isambard Kingdom Brunel's SS Great Britain of 1843 was the first radical new design, being built entirely of wrought iron. Despite her success, and the great savings in cost and space provided by the iron hull, compared to a copper-sheathed counterpart, there remained problems with fouling due to the adherence of weeds and barnacles. As a result, composite construction remained the dominant approach where fast ships were required, with wooden timbers laid over an iron frame (Cutty Sark is a famous example). Later Great Britain's iron hull was sheathed in wood to enable it to carry a copper-based sheathing. Brunel's SS Great Eastern represented the next great development in shipbuilding. Built-in association with John Scott Russell, it used longitudinal stringers for strength, inner and outer hulls, and bulkheads to form multiple watertight compartments. Steel also supplanted wrought iron when it became readily available in the latter half of the 19th century, providing great savings when compared with iron in cost and weight. Wood continued to be favored for the decks.

During World War II, the need for cargo ships was so great that construction time for Liberty ships went from initially eight months or longer, down to weeks or even days. They employed production line and prefabrication techniques such as those used in shipyards today. The total number of dry-cargo ships built in the United States in a 15-year period just before the war was a grand total of two. During the war, thousands of Liberty ships and Victory ships were built, many of them in shipyards that did not exist before the war. And, they were built by a workforce consisting largely of women and other inexperienced workers who had never seen a ship before (or even the ocean).

Worldwide shipbuilding industry

After World War II, shipbuilding (which encompasses the shipyards, the marine equipment manufacturers, and many related service and knowledge providers) grew as an important and strategic industry in a number of countries around the world. This importance stems from:
 * The large number of skilled workers required directly by the shipyard, along with supporting industries such as steel mills, railroads and engine manufacturers; and
 * A nation's need to manufacture and repair its own navy and vessels that support its primary industries

Historically, the industry has suffered from the absence of global rules and a tendency towards (state-supported) over-investment due to the fact that shipyards offer a wide range of technologies, employ a significant number of workers, and generate income as the shipbuilding market is global.

Japan used shipbuilding in the 1950s and 1960s to rebuild its industrial structure; South Korea started to make shipbuilding a strategic industry in the 1970s, and China is now in the process of repeating these models with large state-supported investments in this industry. Conversely, Croatia is privatising its shipbuilding industry.

As a result, the world shipbuilding market suffers from over-capacities, depressed prices (although the industry experienced a price increase in the period 2003–2005 due to strong demand for new ships which was in excess of actual cost increases), low profit margins, trade distortions and widespread subsidisation. All efforts to address the problems in the OECD have so far failed, with the 1994 international shipbuilding agreement never entering into force and the 2003–2005 round of negotiations being paused in September 2005 after no agreement was possible. After numerous efforts to restart the negotiations these were formally terminated in December 2010. The OECD's Council Working Party on Shipbuilding (WP6) will continue its efforts to identify and progressively reduce factors that distort the shipbuilding market.

Where state subsidies have been removed and domestic industrial policies do not provide support in high labor cost countries, shipbuilding has gone into decline. The British shipbuilding industry is a prime example of this with its industries suffering badly from the 1960s. In the early 1970s British yards still had the capacity to build all types and sizes of merchant ships but today they have been reduced to a small number specialising in defence contracts, luxury yachts and repair work. Decline has also occurred in other European countries, although to some extent this has reduced by protective measures and industrial support policies. In the US, the Jones Act (which places restrictions on the ships that can be used for moving domestic cargoes) has meant that merchant shipbuilding has continued, albeit at a reduced rate, but such protection has failed to penalise shipbuilding inefficiencies. The consequence of this is that contract prices are far higher than those of any other country building oceangoing ships.

Present day shipbuilding
Beyond the 2000s, the three East Asian manufacturing powerhouses, China, South Korea and Japan, have dominated world shipbuilding by completed gross tonnage. China State Shipbuilding Corporation, China Shipbuilding Industry Corporation, Hyundai Heavy Industries, Samsung Heavy Industries, Daewoo Shipbuilding & Marine Engineering and Imabari Shipbuilding supply most of the global market for large container, bulk carrier, tanker and Ro-ro ships. During the early 2020s, Chinese shipbuilders saw an increase in orders as operators demand greener fleets. , China’s shipbuilding output, newly received orders and orders-on-hand accounted for 50.2%, 66.6% and 55% of the global market share, respectively, with double-digital growth of all three indexes compared to the previous year.

When referring to the ship type, then China, South Korea and Japan are the producing countries of the carrier ships as mentioned above. While Italy, France, Finland, Germany, United Kingdom and other European countries are the makers of cruise ships (the most), icebreakers, crane vessel and so on.

The market share of European ship builders began to decline in the 1960s as they lost work to Japan in the same way Japan most recently lost their work to South Korea and China. Over the four years from 2007, the total number of employees in the European shipbuilding industry declined from 150,000 to 115,000. In 2022, some key shipbuilders in Europe are Fincantieri, Damen Group, Navantia, Naval Group and BAE Systems.

Shipbuilding output of the United States also underwent a similar change. The US is ranked the 10th largest shipbuilder worldwide. The top companies that build large naval vessels, such as aircraft carriers and cruisers, include Huntington Ingalls, Bollinger and General Dynamics. In the small to medium military vessels category, key shipbuilders include Vigor Industrial, and VT Halter Marine. As the US Navy is shifting to a new fleet architecture that is more widely distributed, unmanned surface vehicles (USVs) development is rapidly propelled to higher priority. Key strategic Program of Record includes prototyping and construction of up to 9 MUSVs, for which a sole contract was awarded to L3Harris Technologies, who partnered with Swiftships to build the MUSVs.

In 2018, the US Defense Department initiated Overlord Program, and developed USV Prototypes 1 (NOMAD) and 2 (RANGER). Both of them took part in multiple fleet level exercises and demonstrations, traveled 28982 nmi in autonomous mode, and tested numerous payloads. Nomam, formerly known as Riley Claire, is a converted offshore patrol vessel, which was built by Swiftships. The objective of the Ghost Fleet Overlord program is to convert large, commercial vessels to autonomous systems.

Modern shipbuilding manufacturing techniques
Modern shipbuilding makes considerable use of prefabricated sections. Entire multi-deck segments of the hull or superstructure will be built elsewhere in the yard, transported to the building dock or slipway, then lifted into place. This is known as "block construction". The most modern shipyards pre-install equipment, pipes, electrical cables, and any other components within the blocks, to minimize the effort needed to assemble or install components deep within the hull once it is welded together.

Ship design work, also called naval architecture, may be conducted using a ship model basin. Previously, loftsmen at the mould lofts of shipyards were responsible for taking the dimensions, and details from drawings and plans and translating this information into templates, battens, ordinates, cutting sketches, profiles, margins and other data. However, since the early 1970s computer-aided design became normal for the shipbuilding design and lofting process.

Modern ships, since roughly 1940, have been produced almost exclusively of welded steel. Early welded steel ships used steels with inadequate fracture toughness, which resulted in some ships suffering catastrophic brittle fracture structural cracks (see problems of the Liberty ship). Since roughly 1950, specialized steels such as ABS Steels with good properties for ship construction have been used. Although it is commonly accepted that modern steel has eliminated brittle fracture in ships, some controversy still exists. Brittle fracture of modern vessels continues to occur from time to time because grade A and grade B steel of unknown toughness or fracture appearance transition temperature (FATT) in ships' side shells can be less than adequate for all ambient conditions.

As modern shipbuilding panels on a panel line become lighter and thinner, the laser hybrid welding technique is utilized. The laser hybrid blend focuses a higher energy beam on the material to be joined, allowing it to keyhole with a much higher depth to width ratio than comparative traditional welding techniques. Typically a MIG process trails the keyhole providing filler material for the weld joint. This allows for very high penetration without excessive heat input from decreased weld metal deposited leading to less distortion and welding at higher travel speeds.

Ship repair industry
All ships need repair work at some point in their working lives. A part of these jobs must be carried out under the supervision of the classification society.

A lot of maintenance is carried out while at sea or in port by ship's crew. However, a large number of repair and maintenance works can only be carried out while the ship is out of commercial operation, in a ship repair yard.

Prior to undergoing repairs, a tanker must dock at a deballasting station for completing the tank cleaning operations and pumping ashore its slops (dirty cleaning water and hydrocarbon residues).

title: Shipbuilding