Measuring and Calibration

The International System of Units (SI) is the modern metric system used globally for precise measurement. It defines seven base units (meter, kilogram, second, ampere, kelvin, mole, and candela) from which all other units are derived. These units are universal, coherent, and based on fundamental physical constants. By adopting SI units, a post-collapse society can restore scientific progress, fair trade, and efficient resource management, laying the groundwork for sustainable development.

Useful Things to Note

Scientific Notation

Numbers can get large really fast. To shorten this so that we don't have 30 zeros floating at the end of every number, we use some basic math to describe a notation. If the number has a E(some number here), e(number), or even x10^(number), this stands in the place of x10^(number).

This means that you can shorten the number 467,110,000,000 to 4.67110000000x10^11 or, roughly 4.67E11. A negative number means the same that any negative exponent means. (See basic rules of Math)

This means you can turn the number 0.000000846 to 8.46E-7.

Prefixes

Because the previous notation can be hard to read, prefixes are available to whatever unit you want. For instance, instead of 2.53x10^-5 meters, you could say 25.3 µm which means 25.3 1 thousandths of a meter. This is much easier to picture even though it is still really small.

A common set of these prefixes go as follows:

name	symbol	meaning		name	symbol	meaning
queta	Q	x1030		quecto	q	x10-30
ronna	R	x1027		ronto	r	x10-27
yotta	Y	x1024		yocto	y	x10-24
zeta	Z	x1021		zepto	z	x10-21
exa	E	x1018		atto	a	x10-18
peta	P	x1015		femto	f	x10-15
tera	T	x1012		pico	p	x10-12
giga	G	x109		nano	n	x10-9
mega	M	x106		micro	μ	x10-6
kilo	k	x103		mili	m	x10-3
hecto	h	x102		centi	c	x10-2
deka	da	x101		deci	d	x10-1

The Units

Distance: the meter

The meter is described to be roughly the length of a walking step, using the more precise definition of the distance light can travel in 1/(299,792,458) seconds. This comes out to be roughly 3.33564095E-9 seconds

To approximate the meter, several methods exist:

1. a second-pendulum: by suspending a mass from a length of one meter

Time: the second

The second is historically defined through the duration of the day. One day is divided into 24 hours, which are first divided into 60 minutes which are in turn divided into 60 second each.

• 1 day = 24 hours, 1 hour = 60 minutes, 1 minute = 60 seconds.

More recently the second has been redefined as a number of vibrations of the cesium element, but in everyday life this definition does not have practical use.

Theres also a "human" way to track time, But it can differ on all sorts of elements. Take this as a "basic" way to tell time.

Human way to track

Unit	How to measure	Equivalent to
Breath.	Inhale and exhale.	~5 seconds.
Heartbeat.	Place your second and third finger from your thumb, on your wrist or neck, every beat is a pulse.	~1 second.
Sunrise to sunset.	From the moment you can see the sun, to the moment it can't be seen anymore.	~11-16 hours, depending on season and place.
One sunrise to another sunrise.	From one sunrise to another.	~1 day, depending on where you are.
30 sunrise to sunrise cycles.	The time it takes to see 30 sunrises.	~1 month.
4 months.	about every 4 months, ~120 sunrise cycles.	~1 season.
4 seasons	about every 4 seasons, 12 months, ~360 sunrise cycles	~1 year

Quantity: the mole

The number of atoms in 1 gram of Carbon-12. A mole is a counting unit. The units of moles are abbreviated as mol. Just like you can have 1 dozen eggs which is 12 eggs, you can have 3 moles of atoms. The definition based off of Carbon is to make the mole a standard number of atoms. This number is roughly 6.022E23. This is a lot of atoms but as per the definition, 1 gram of carbon-12 has exactly 1 mole of Carbon atoms. This leads to the statement that Carbon-12 weighs exactly 12 grams for every mol. This unit gives chemists a nice way to convert between ratios of atoms and amount of the substance. For instance, H₂O is the chemical formula for water. This means in order to make one molecule of water, you need two atoms of Hydrogen for every one atom of Oxygen. Barring the fact that Oxygen does not naturally occur in one singular atom, you could say that since one atom of Hydrogen weighs 1.00794 grams per mol, and Oxygen weighs 15.999 grams per mol, you could say for every 1.00794 grams of Hydrogen you need 15.999 grams of Oxygen to create water with little to no excess.

Useful sub-units

Pressure: force over surface

Energy