The Gist of Technology
Technology requires heat engines, machine tools, chemistry, metalurgy,optics,electricity, vaccuum processes, and mathematics. If these things are avalable, nearly everything else can be derived or made. If any one of these is lacking, a large chunk of technology disappears.
Each of these things or subjects can be understood in a few days or hours, though the details in any one study could consume lifetimes. In each case, however, a small number of crucial and simple concepts provide most of the benefit.
This is a look at each of these and how we depend on them.
When a gas is heated with its expansion ability limited, pressure builds up. This pressure can be used to push a piston in a cylinder, the blade of a turbine wheel, or push a rocket. Most engines have a piston which is pushed up and down in a cylinder. The piston is attached to a crank to provide rotation.
The first engines were steam engines. Most engines today are internal combustion where fuel is burned inside the cylinder to create the heat and pressure.
In order to contain the gas, the pistion and cylinder must fit together with microscopically fine clearance. The bearing mounts for all the shafts and other parts must be straight and true and fit together more closely than the eye can determine.
Machine tools create precision parts. Anytime two parts must fit to microscopic accuracy, they are machined. The two main techniques are cutting and grinding.
Cutting types
The first machine tool was the lathe. It is used to make cylinders, pistons, bearings, and threaded parts. With appropriate attachments and enough time, a lathe can make almost anything. It is still the most general purpose machine made. A lathe rotates the part and cuts it with some sort of cutting tool mounted on a slide rest.
The lathe makes cylindrical objects easily and flat objects wirh with difficulty. The planer, shaper and mill make flat objects easily and round objects with difficulty. The Planer moves the work on a flat table and cuts it with a lathe like cutter. The shaper moves the lathe like cutter back and forth while moving the work slowly. The mill uses a rotating cutter while moving the work slowly.
The lathe and planer move the work quickly and the cutter slowly, while the shaper and mill move the work slowly and the cutter quickly.
Most modern practice uses the lathe and mill only.
Grinders
Grinders use a grind stone of some type to form the surface. They look a lot like the lathe, planer or mill, except that the cutting tool is a grinding wheel or lap.
Grinding was traditionaly the only way to get really precise surfaces or to gring glass. Most optical devices are ground.
The most important chemical concepta are oxydation, reduction, acid-base-salt, and the periodic table.
Oxydation is the combination of an element with oxygen or an element behaving like oxygen. Since the air is about one fifth oxygen, oxidation occurs around us all the time. Iron rusts, paint chalks, wood burns, etc. A fire is rapid oxidation at a high reaction temperature. Oxidation is adding oxygen to a compound.
Reduction is removing oxigen from a compound. Iron oxide can be reduced with carbon to yield pure iron and oxidized carbon, or carbon dioxide. Most metals are obtained from there ores by some method of reduction.
Acid-base-salt: The class of sour compounds are acids. The class of compounds called hydroxides are bases. An acid combines with a base to produce a salt and water. Hydrochloric acid and sodium hydroxide produce sodium chloride, or common salt.
The periodic table is the list of all the chemical elements arranged in columns such that all the elements in each column make the same kind of compounds. It sums up much of two hundred years of chemical research on one page.
Here is a Periodic Table I like
Organic chemistry is the study of carbon compounds, of which there seem to be an infinite number. Carbon can act either as an oxydizer or as a reducer and can combine readily with itself. Most of the concepts are beyond the scope of this short piece.
Metals are essential to most technology. The most important metal is iron, but aluminum, titanium, copper, tin,zinc, tungstun, and nickel, are also important.
Most metals are very soft and relatively easy to machine, but are very easy to machine with something harder.
Hard materials in general use are mostly carbides--coumpounds of a metal and carbon. The hardest is carbon carbide or diamond. Other important carbides are silicon carbide, iron carbide and tungsten carbide.
When iron is reduced from its ore with carbon, iron carbide is formed. The amount of carbide determines the main characteristics of the iron.
Wrought iron and mild steel has almost no carbon. It is soft, easily worked and never changes no matter how it is heated.
Tool steel has about one percent carbon. If heated red hot and cooled slowly it is soft, if cooled quickly it gets hard and brittle. Being able to change the steel by heat treatment makes it possible to machine it when soft and heat treat it to make it as hard as needed. This one capability makes machine tools possible.
Iron with higher carbon is usually always fairly brittle and is only used for less expensive things ( cast iron).
Optical devices are generally either telescopes, microscopes, cameras, spectroscopes, or interferometers.
They are made as combinations of lenses or mirrors which are created to extremely precise shapes ( often within millionths of an inch or centimeter).
Telescopes have a large light entry lens or mirror and a small exit. They make distant things appear closer.
Microscopes have a small light entry lens or mirror and make small things appear larger.
Camera lenses are flexible, making images with are larger or smaller depending on need. Camera lenses try to make the most accurate image possible.
Spectroscopes break light up into its component colors. The spectrum of a excited (heated) element is unique to that element and can be used to identify it.
Interferometers are a system of mirrors in which light is relected back on itself. Depending on the distances and other conditions, the light will cancel or aid itself. This can be used for all sorts of interesting things like measuring distances to millionths, measuring the diameter of stars, or making holograms.
Optics are usually ground from glass using special types of machine tools (called lens grinders).
Electricity is the flow of something called electrons in a conductor. Conductors are usually metal, vaccuum, semiconductors, or electrolytes--water solutions of acid, base, or salt.
Two different metals placed in an electrolyte will form a battery. A connection between the two different metals will cause current to flow. The amount of electric current with flows depends on the voltage of the battery and the resistance of the connection. The higher the voltage, the more current, the higher the resistance, the less current.
Whrn current flows, a magnetic field is formed. If a conductor is moved through a magnetic field, current flows. These principles are the basis of the generators, motors, radios, etc. of modern life.
Current flowing through a vaccuum has many interesting properties and forms the basis of much of physics and technology. Devices include the X-ray tube, the cathode ray tube (television picture tube), the amplifier tube, the microwave tube, and the superconducting super colider.
Carbon, silicon, gemanium, etc are semiconductors (column four A on the periodic table). They insulate in the pure state and conduct if impurities are added. The impurities come from the two columns on either side in the periodic table. From one side the material is called N type from the other side P type. Semiconductor devices made of N and P material in various configurations are used to make almost all modern electronic devices, such as radios, televisions, and computers.
Vaccuums are used for electronic devices, for lighting, for cleaning, and to deposit films on a surface.
The electronic devices usually heat a metal until electrons boil off which can then be directed with voltages and magnetic fields to different points inside the tube.
Discharge lights use an electric spark in a gas in a low level vaccuum to create a light. Mercury vapor, sodium vapor, and fluorescent lights all use this.
Vaccuums can clean a surface by causing impurities to boil off.
Boiling a metal in a vaccuum can be used to create a very precise film on a surface for mirrors and electronic devices.
The important mathematics is the mathematics of triangles, of circles, and linear functions.
Triangles have three sides and three angles. Any straightlined structure can be broken up into triangles for analysis. Triangles are the most rigid structure, since they cannot change shape without being broken. Many engineered structures are made of triangles. The most important triangle is the right triangle which has a right (90 degree) angle in it. The most important right triangles are the 45-45-90 (with sides of length 1,1, and the square root of 2), and the 30-60-90 ( with sides of 1, 2, and the square root of 3). The lengths of the sides are determined by the pythagorean theorem: the two short sides squared add up the the long side squared.
Precise circles ( actually cylinders) are made on a lathe. The cutting tool always stays the same distance from the center line of the lathe, so circles are always cut as the object turns. A compass draws a circle. Building triangles inside circles is a very powerful technique.
The most general mathematics for this is trigonometry. The sine, cosine and tangent are three different measures of a right triangle which I believe were first worked out by Egyptian slaves for Ptolemy around 125 AD and put into tables. They are now available on calculators and computers.
Linear functions are formulas which use only multiplication, division, addition and subtraction. In fact, usually only multiplication and division are needed. They have the form a = b times c which is usually written as a = bc. The a is the dependent variable, the b is the parameter, and the c is the independent variable.
Here are some examples:
If b is the gear ratio of two gears ( the diameter of the input gear divided by the diameter of the output gear) a is the speed of the output shaft when c is the speed of the input shaft.
If b is the resistance of an electrical resistor, a is the voltage across the resistor when c is the current flowing through the resistor.
If b is the Sine of an angle found from a calculator or table of sines, a is the lenght of the side opposite the angle when c is the length of the long side of the right triangle.
The trigonometry example needs more explanation
We measure an angle ( call it N) of a right triangle then look up the sine, cosine or tangent. The long side of the right triangle we will call H, the side opposite ( not touching) our angle O and the side adjacent to ( touching) our angle A.
Here are the linear formulas for the three cases:
O = sine(N) H
A = cosine(N) H
O = tangent(N) A