[Skill] Physics

[Zhol]

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Article: Physics
Author(s): Zhol
Other development: None yet
Additional Info: None yet

Peer Review Thread: N/A
Founder Review Thread: N/A

Synopsis: Physics is a body of knowledge, based on observation, that describes the behaviour of the physical/natural world. While most things happen "because of magic", physics seeks to describe the rules and patterns that the physical world obeys. Mizahar's physicists may not understand what makes an object float or fall to the ground, by observing the manner in which those effects take place they hope to be able to define and predict that behaviour.

The article will cover the basic/measurable rules and laws of physics, as well as the units and methods used to measure them, and then will focus on how that basic framework of understanding can then be applied to other skills: parabolic arcs helping with archery, buoyancy helping with shipbuilding and identifying gem stones, how levers/gears/pullies work for gadgeteering, how light travelling in straight lines allows lenses and sundials to work, and so on. Nothing too fancy: just the important/basic concepts.

Clearly, Mizahar won't have any understanding of gravity or atoms or electricity, so I'll be doing a lot of research into old / outdated scientific theories to make sure the article avoids any allusions to those theories/understandings. I've also been doing research into the level of technology and understanding that Mizahar has: for example, I know that steam/boilers/etc are not allowed, that there is enough understanding of magnetism and light/optics for compasses and sighting lenses to be on the Price List, etc.

Outline:

1. Overview
   
   • Prerequisite Skills
2. Basic Principles
   
   • Mass
   • Volume and Density
   • Velocity, Momentum, and Inertia
3. Dynamics (science of forces/movement)
   
   • Dynamics of Solids
     
     • Types of Solid (earth/rock, metal, wood)
     • Interactions With Solids (friction)
   • Dynamics of Liquids
     
     • Types of Liquid (water, viscocity)
     • Interactions With Solids (buoyancy, erosion)
   • Dynamics of Air
     
     • Types of Air/Gases (?)
     • Interactions With Solids (falling through the air, sails, wind)
   • Dynamics of Heat
     
     • Interactions With Solids (conduction, melting, burning)
4. Mechanics (science of machines - the basis of gadgeteering)
   
   • Levers (including their application for scales/balances)
   • Gears and Pulleys
5. Optics (science of light)
   
   • Shadows
   • Lenses
6. Magnetism (applications for compasses)
7. Units of Measurement (quick reference; imperial units)
8. Applications / Related Skills

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[Sedge]

Proposal Accepted

I'm excited to have another of the more academic subjects being developed! I look forward to seeing where you go with this.

[Zhol]

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I. Overview

Physics is a discipline of knowledge that seeks to explain the properties and behaviour of the natural, physical world. It seeks to understand and define the natural laws that govern the way that physical substances move and behave under different conditions.

Though disciplines of magic such as alchemy and reimancy are able to manipulate the physical world, physics does not seek to understand the mechanics behind magic: it focuses on objects as they are, not how they came to be. Physicists study the world both actively through experimentation, and also passively, using Observation and Philosophy to perform "thought experiments" and form theories and hypotheses about the nature of nature.

Mathematics is an important part of defining physical laws in a quantifiable way, and Investigation is an important skill for approaching physics analytically. Disciplines such as Astronomy, Geology, Jewelcrafting, Philtering and Gadgeteering all build on basic theories and principles that are explained by physics.

II. Fundamentals

Elemental Forces

Through magic, reimancers are able to manipulate the four elements - Earth, Water, Air, and Fire - to create and manipulate physical substances. These elements are also the four fundamental forces understood by physics as having an influence on the physical world.

The Earth ("heaviness") force is responsible for providing physical substances with weight, and compels them to move downwards, as if they were being drawn towards Semele. The Air ("lightness") force acts in the opposite direction, providing objects with buoyancy, as if they were rising towards Zulrav. The influence of Air can have a profound effect: when combined with Water to make ice, the Air content allows ice to float, even though solids are usually heavier than their liquid counterparts. The interplay between the Earth and Air forces acting on an object is responsible for it's Density: the ratio between heavy Earth and light Air within a given volume.

The Fire ("heat") force is responsible for making objects hotter and easier to manipulate. Fire and heat always attempts to move upwards, seeming to have inherited Ivak's desire to escape from his underground prison. The Water ("cold") force is responsible for opposing fire and cooling hot objects, and acts in that manner in everything from perspiration to blacksmithing; water's connection with cold is the reason that condensation forms on cold surfaces. Water is naturally attracted to itself, and if permitted by the terrain to do so, it will attempt to reunite with the largest body of water it can - sometimes even eroding it's way through stone to do so - as if it were compelled to return to Laviku. The interplay between the Fire and Water forces is responsible for the Temperature of an object.

Physical Properties

Length is a description of how far an object extends in a particular direction. In physics, there are three fundamental directions in which length can be measured: height is the vertical length of an object, perpendicular to the ground; width is the length of an object across the observer's field of view, parallel to the ground and the horizon; and depth is the length of an object extending away from the observer, along their line of sight. By using two of these lengths to define a square, an observer can mathematically describe the Area of a flat surface. By using all three lengths to define a cube, an observer can describe the object's Volume.

Area = Height x Width

Volume = Height x Width x Depth

Weight is a description of the total impetus that the Earth force provides to an entire object. When a weight presses against a surface, that weight is divided across the area of contact; this is known as Pressure. The amount of weight that is contained within a specific volume of a substance is it's Density, which directly relates to the ratio between the Earth force and Air force acting on an object.

Pressure = Weight / Area

Density = Weight / Volume

Dynamic Properties

Distance describes the length that an object has travelled from it's starting point. The distance travelled over a particular period of time describes the object's Speed, and is usually expressed in units per second or per hour. Though difficult to directly measure, especially outside of a laboratory, the rate at which speed changes - that is, how much speed has changed over a particular period of time - is known as Acceleration.

Speed = Distance / Time

Acceleration = Speed / Time

Impetus is a compulsion provided by an external force that causes an object to accelerate. When applied to a stationary object, an impetus will cause it to accelerate into motion. When applied to a moving object, an impetus can have one of two effects: when applied along the direction of motion, it will cause the object to accelerate to a higher or lower speed; when applied in any other direction, it will cause the object to begin to change direction. The magnitude of an impetus is directly proportional to the weight of the object it is applied to, and the acceleration that it produces.

Impetus = Weight x Acceleration

Work is the amount of effort required to move an object a particular distance. It is proportional to the distance travelled and the impetus required. When work is expressed over a particular period of time, it is described as Power; a common use of this property is to define horsepower: the amount of work per second that can be performed by a single horse.

Work = Impetus x Distance
Work = Weight x Acceleration x Distance

Power = Work / Time
Power = Impetus x Distance / Time
Power = Impetus x Speed

III. Measurement

Units of Length

According to folklore, the units for measuring length and distance are based upon the body proportions of an unnamed Isur - variously believed to be a mathematician, an ancient king, or even a physical embodiment of Izurdin himself - due to the Isur's fairly consistent height. The basic unit, a Measure, was described as being five times the length of the subject's Foot; each foot meanwhile was three times the width of the subject's Hand. A unit for long distance was derived from these proportions as well: the Mile, based on an old word meaning thousand, was one thousand Measures in length (approximately five thousand feet).

These measures were good for estimation, and are still used in market places to quickly approximate lengths of things such as fabric, rope, and wood; but for precision engineering as well as for trade between races with vastly different body proportions, standardisation was needed. The hand was divided in half and half again; this standard unit of measurement became the Inch. Thus, a Hand was formally defined as being 4 inches; a Foot was 12 inches; and the standardized Mile was discovered to be 5,280 feet. Most lengths are measured in feet and inches, though hands are still used in certain instances, such as fabric lengths and the height of horses.

For situations where extreme precision is required, the inch was divided into Sixteenths, which usually provides enough accuracy for tasks like blacksmithing and woodworking. In casual usage, measurements are often rounded up to larger factions: four sixteenths would be called a Quarter of an Inch; eight sixteenths would be Half an Inch, and so on.

Units of Weight

The basic unit of weight is the Pound, which derives it's name from an old word meaning weight. Like inches being divided into sixteenths, the Pound was broken down into sixteen parts, each called an Ounce[/u]. For precise measures, such as with Cooking or Philtering ingredients, or with precious substances, fractions of an ounce are used. (half an ounce, eighth of an ounce, etc)

For larger amounts, particularly for measuring trade goods like grains, the [b]Hundredweight is used, which has a value of one hundred pounds. For extremely large weights, the Ton is used, which weights twenty Hundredweights, or two thousand Pounds.

Units of Capacity

With solid trade goods being measured in terms of weight, merchants wanted a method to sell fluid trade goods, such as wine and oil in a similar way. However, weighing fluids was not as easy as weighing solids: the sack holding twenty pounds of potatoes weighed almost nothing, but a vessel holding twenty pounds was much heavier; and fluids could not be as conveniently placed on scales in the market place. It was observed however that though some liquids were heavier than others, a particular weight of a fluid such as water would fill a particular container the same amount each time. This allowed a container to be crafted that had the capacity to hold a specific weight of water.

A system of measurement was used, based on a vessel with the capacity to hold one pound of water, dubbed a Pint. As with pounds, the Pint was divided into sixteen Fluid Ounces. This allowed merchants selling liquid produce - as well as those selling finely granulated products like salt, sugar, or sand - to have a better understanding of how many ounces of cheese were equivalent to how many fluid ounces of milk, and so on.

The fluid weight of a liquid (eg. it's capacity in fluid ounces) is often not the same as it's actual weight (eg. it's weight in ounces): the weight of a liquid can vary based on the density of the substance, and also because of factors like temperature.

Units of Time

Units of Rotation

Particularly when dealing with gear mechanisms in Gadgeteering, it was necessary for physicists to be able to describe by how much an object rotated. The obvious parallel was the passage of time: Astronomy had already described Syna's circular path above and below the horizon, and divided it into units for timekeeping. Thus, an Hour of Arc was the amount of arc travelled by Syna in one hour (on an equinox). Half a circle was twelve Hours of Arc (or Arc Hours), and a full circle was twenty-four. This equivalency allowed the units of rotation to be particularly useful in creating timekeeping devices.

For more precise measurements, Minutes of Arc or Arc Minutes were used, defined as one sixtieth of an Hour of Arc - and thus, one 1,440th of a circle. For small mechanisms, an Arc Minute is such an imperceptibly small rotation that it can not effectively be measured. Instead, Arc Minutes are usually used in multiples of ten. In the interests of precision, physics notation usually describes angles in terms of Arc Minutes rather than Arc Hours - for example, a quarter of a circle or "right angle" would be written as 360 Minutes, as opposed to 6 Hours.

Units of Heat

Compound & Obscure Units

A League is a unit of distance, that describes the distance travelled by a man walking at an average pace across favourable terrain and in favourable conditions, for a duration of one hour. It is usually approximated as three miles in regions such as Cyphrus and Sylira, but is not widely used in remote regions like Kalea where travel is much slower going.

In sailing, a few special units of measurement are used. A Yard is the amount of rope that can be coiled around a man's forearm (from hand to elbow) once; or alternatively, it is a man's reach while hauling on a rope; usually approximated as being about 3 feet. A Fathom is a unit of water depth, that would submerge an adult man if he were standing vertically; approximately 6 feet. A Knot is a unit for measuring speed: a knot is tied every arm-length (ie. half a yard) and a weight is attached to the end, which is dropped overboard and allowed to trail behind the ship. The number of knots that pass through the sailor's hand each second is the ship's speed in Knots.

Technically, the "capacity" refers to how much of a substance the container can hold. The amount of a substance can also be defined in terms of "volume" using units such as a Cubic Inch. Converting between the two is difficult and seldom exact; physicists will usually approximate that one Pint of a fluid has a volume of twenty-eight Cubic Inches.

IV. Dynamics

Dynamics of Solids (Earth)

Some materials have Elasticity, meaning that when they are shaped or deformed, they will naturally return to their original state - for example, the wood of a bow after the arrow is fired. If too much strain is placed on these elastic materials, they will reach a certain point - called their elastic limit - where they will cease to demonstrate elastic properties and instead will demonstrate Plasticity. A material that is plastic can be shaped or deformed, and will permanently retain it's new state - for example, hammering metal into a sword blade. There are two main kinds of plastic behaviour: Ductility, which is the extent to which a material can be stretched without breaking; and Malleability, the ease by which a material can be hammered. While some substances (for example gold) are both malleable and ductile, others (such as lead) have high ductility but low malleability. These properties are particularly important for blacksmithing.

The Hardness of a material describes how resistant it is to both elastic and plastic changes. Hard materials are difficult to cut and shape, and are resistant to abrasion and erosion. Certain blacksmithing processes are designed to increase the hardness of a metal: a useful property for weapons and tools. Hardness is also important in jewelcrafting: gemstones are often harder than the minerals they are found in, which can be exploited to help separate gems and rocks.

When an impetus is applied to a solid object that is in contact with a surface, the surface can provide a resistance that impedes any movement that the impetus is trying to cause. This resistance is called Friction, and is believed to be the result of the "roughness" of a surface. A surface like ice or glass is extremely smooth, and so tends to create little friction; wood and stone however have imperfections and variations on their surface which snag against each other. Some surfaces (human skin for example) appear smooth, but generate friction: these are believed to still have a "roughness", but one that is invisible to the naked eye.

Dynamics of Fluids (Water)

Dynamics of Air

Dynamics of Heat (Fire)

V. Mechanics

Levers / Moments / Pressure / Torque
Gears / Pulleys / Ratios

VI. Optics

Shadows
Lenses
Lightning?

VII. Magnetics

Including "how do compasses work?"

VIII. Applied Physics

Physics has no prerequisites, but physicists should begin to use their Investigation and Mathematics skills for experiments and hypotheses from Competent onwards.

Related Skills

• Astronomy studies the nature and movement of stars
• Geology studies the nature of Earth substances (ie. rocks) in more depth
• Gadgeteering uses mechanics to construct gadgets and mechanisms
• Jewelcrafting uses weight and buoyancy to identify precious stones
• Philtering uses evaporation and condensation to purify substances

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[Zhol]

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Updates
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18th March

Still working on this! There's a lot of reading and research involved at this stage - a lot of trying to work out what the basic concepts are going to be, working out what is understood and what isn't, what words I should use and not use, etc. The outline in the initial proposal is already going to need to change: explaining the basic units of measurement and the basic properties of stuff (weight, density, forces, etc) is going to need to be near the start, though there will be a quick reference chart/list for units near the end as well.

Concepts so far:

• Theory of the structure of matter will be based on the four reimancy elements. The ratio of Earth versus Air determines the weight/density/etc of a material; the ratio of Fire versus Water determines the temperature and physical state (solid/liquid/gas) of a material. In simple terms: Earth makes things heavier, Air makes things lighter; Fire makes things hotter; Water makes things colder. Note: objects are "influenced by" these elements (like fundamental forces), not "made of" these elements. This is important: ice is "made" of air and water, and there is no earth element in it, but it is still "influenced by" earth, giving it weight.
• Based on this, "gravity" is not a separate concept: it is merely the influence of the earth element on an object, trying to pull it back down towards the ground / Semele.
• The units for measuring length (feet, hands, etc) are based on the body proportions of an Isur, because they are all roughly the same size/height. This is consistent with the etymology of Mile (from milla, meaning thousand), as a mile is approximately one thousand times the height of an Isur (ie. approximately 5,000 feet). Include a few regional and/or occupation-specific units of measure - for example, knots for sailing. Avoid units that sound too industrial (eg. chain, cable, etc).

Vocabulary:

• Refer to weight, not mass. (Mizahar shouldn't know the difference)
• Refer to speed, not velocity. (for simplicity's sake)
• Refer to impetus, not force. (a more old-sounding term)

I am still pulling together concepts and reworking/tweaking things to try and make them more coherent and understandable so please bear with me! If you have any thoughts, questions, ideas, or input, then please, please, please let me know in the Discussion Thread. I'd love to hear them!


2nd June
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• Added the Overview/description and Applied Physics/related skills. Am I missing any obvious related skills?
• Added sections for Units of Weight and Units of Capacity. I have used US definitions for a hundredweight and a ton ("short ton"), because they provide simpler numbers to deal with (100 and 2000, instead of 112 and 2240). I am also using a US pint (16 fluid ounces) instead of a UK pint (20 fluid ounces), because I am trying to stick to using twelve and sixteen where possible, so that the units of measurement make a little bit more sense when viewed together. (Sixteenths of an inch, sixteen ounces in a pound, twelve inches in a foot, etc)
• HOWEVER, the idea that the fluid ounce is equivalent to one ounce of water is based on the UK/imperial system, which is about a millimetre smaller than a US fluid ounce. The conversion between pints and cubic inches takes this into account (accurately, one Mizahar Pint is 27.74 cubic inches).
• Added the Units of Rotation section. This is probably the most counter-intuitive, because it is "made up" rather than based on something in the real world. There is no agreed upon explanation for why a circle has 360 degrees (it's either very vague, or requires explaining trigonometry). However, degrees are usually divided into minutes and seconds, and since rotation has a part to play in the "clockwork" part of Gadgeteering, I decided to base things on the 24-hour clock that Mizahar uses (rather than a real world 12-hour clock). Granted, a "360 no scope" is now either ridiculously impressive or laughably simple (depending if it's hours or minutes), and if something is "on your six" it's now off to one side instead of behind you... but hopefully it's not too difficult to grasp.

Vocabulary:[list]
[*] Capacity for fluid volumes
[*] DO NOT use "degree" as a unit, use it as terminology instead. "To what degree has the gear rotated?"
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