# Scientific Units

Last Updated: 10/26/20 by Tim Paschkewitz

##### ARTICLE TAGS
• units,
• SI,
• aftermath units,
• aftermath plotting,
• scientific units

### 1The International System (SI) of Units

Many general-purpose spreadsheet and plotting tools are intended for business or financial applications and do not support the concept of scientific units.  AfterMath, however, is a tool designed specifically to meet the needs of scientists and engineers, and one of its distinguishing features is the ability to keep track of proper scientific measurement units.

Internally, AfterMath explicitly associates all numeric data with a scientific unit derived from the International System of Units (SI System) .  This system is based on seven fundamental units of measure, as shown in Table 1:

 Name Symbol Quantity meter $m$ length kilogram $kg$ mass second $s$ time Ampere $A$ electric current Kelvin $K$ temperature mole $mol$ amount of substance candela $cd$ luminous intensity
Table 1. Seven Fundamental SI Units of Measure

AfterMath recognizes these seven fundamental units of measure and also many other units of measure that are derived from these seven units.  These fundamental and derived SI units may be used in conjunction with the following standard metric prefixes:

 1000m 10n Prefix Symbol Short Scale Long Scale Decimal $1000^8$ $10^{24}$ yotta- Y Septillion Quadrillion 1 000 000 000 000 000 000 000 000 $1000^7$ $10^{21}$ zetta- Z Sextillion Trilliard 1 000 000 000 000 000 000 000 $1000^6$ $10^{18}$ exa- E Quintillion Trillion 1 000 000 000 000 000 000 $1000^5$ $10^{15}$ peta- P Quadrillion Billiard 1 000 000 000 000 000 $1000^4$ $10^{12}$ tera- T Trillion Billion 1 000 000 000 000 $1000^3$ $10^{9}$ giga- G Billion Milliard 1 000 000 000 $1000^2$ $10^{6}$ mega- M Million 1 000 000 $1000^1$ $10^{3}$ kilo- k Thousand 1 000 $1000^{2/3}$ $10^{2}$ hecto- h Hundred 100 $1000^{1/3}$ $10^{1}$ deca- da Ten 10 10000 100 (none) (none) One 1 $1000^{-1/3}$ $10^{-1}$ deci- d Tenth 0.1 $1000^{-2/3}$ $10^{-2}$ centi- c Hundredth 0.01 $1000^{-1}$ $10^{-3}$ milli- m Thousandth 0.001 $1000^{-2}$ $10^{-6}$ micro- µ Millionth 0.000 001 $1000^{-3}$ $10^{-9}$ nano- n Billionth Milliardth 0.000 000 001 $1000^{-4}$ $10^{-12}$ pico- p Trillionth Billionth 0.000 000 000 001 $1000^{-5}$ $10^{-15}$ femto- f Quadrillionth Billiardth 0.000 000 000 000 001 $1000^{-6}$ $10^{-18}$ atto- a Quintillionth Trillionth 0.000 000 000 000 000 001 $1000^{-7}$ $10^{-21}$ zepto- z Sextillionth Trilliardth 0.000 000 000 000 000 000 001 $1000^{-8}$ $10^{-24}$ yocto- y Septillionth Quadrillionth 0.000 000 000 000 000 000 000 001
Table 2. SI System Prefixes

### 2Non-SI Units

There are several units of measurement still in use by scientists and engineers that are not part of the SI system.  AfterMath recognizes some (but not all) of these non-SI units.  For example, the plot "Displacement vs. Time" shown in Figure 1 gives the distance in feet (an English unit) versus time in hours (rather than seconds).  Even in this case, however, it is important to note that AfterMath stores the data internally in the appropriate SI units (meters and seconds).  But for display purposes, the data is automatically scaled to match the non-SI units that were chosen for this plot (feet and hours).

Figure 1. AfterMath Plot with Non-SI Units

Finally, AfterMath also permits the use of unitless data when necessary.

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