|
Introduction
|
|
|
What's New
|
|
About these pages
|
|
|
|
Counting by powers of ten
| "ten, hundred, thousand, ..." (101, 102, 103, ...)
|
|
Counting to ten billion... on your fingers
| Counting by powers of ten, on fingers.
|
|
"What order of magnitude is ...?" game
|
|
Lots of dots
|
|
A million dots on one page
|
|
A dot for every second in the day
| with clock.
|
|
A dot for each day
|
|
|
|
|
How to simplify a number
| rounding, compacting, memorables, etc.
|
|
Rounding off a number
| simplifies it by creating zeros.
|
|
Rounding to an order of magnitude
| extreme rounding.
|
|
What is "order of magnitude"?
|
|
|
Exponential Notation
| sliding the decimal point.
|
|
Scientific Notation
| is exponential notation plus conventions.
|
|
How to write and speak the exponential notation
|
|
|
A few examples of exponential notation
| Not of much use.
|
|
|
|
On Being Approximate
| The what, why, and how.
|
|
Why be approximate?
|
|
|
Bounding uncertainty
|
|
|
Honesty in approximation
|
|
|
Fermi Questions
| Rough quantitative estimates.
|
|
Landmarks
|
|
|
A Pinocchio estimation game
| detecting implausible approximations |
|
An experiment with mayonnaise
|
|
|
|
|
`Powers of Ten' scales
|
|
|
Scaling the universe to your desktop
|
|
|
Pm,
Tm,
Gm,
Mm,
km,
m,
Millimeters in your hands,
um,
nm
|
|
|
Constructing your own desktops
|
|
|
|
|
Deep understanding
|
|
|
If you can't explain it
to a nine year old...
| then you don't really understand it yourself.
|
|
For children
|
|
|
Developing "deep" understanding
|
|
|
Probing near space with a flashlight
|
|
|
Exploring with teleportation
| Using imagination to generate questions
|
|
China is down over there...
| looking down through the earth
|
|
Over maps, envisioning the atmosphere
|
|
|
Earth's surface as a 20 x 25 Megameter rectangle
|
|
|
Round Earth, Tilted People
|
|
|
Visualizing Earth's Internal Structure
| a road trip going down
|
|
Atomic bonding
|
|
|
Getting a feel for big numbers
|
|
|
A feel for big numbers, with grains of salt
|
|
|
Only a breath away
| aka "Caesar's last breath"
|
|
Your enormous surface area
|
|
Good descriptions
|
|
|
Knowledge you can work with...
|
|
|
Simple models
|
|
|
A ball's volume and area are 1/2 of its box's
|
|
|
When Length grows a little, Area grows a lot
|
|
|
The relative size of
Earth, Jupiter, Sun (1 : 10 : 100)
|
|
|
Trig w small angles
|
|
|
Sphere
|
|
|
|
|
Resources
|
|
Search for Simplicity - Weisskopf
| a column.
|
|
The Back of the Envelope - Purcell
| a column.
|
|
On the Back of an Envelope - Triplehorn
| a column.
|
|
|
|
Scale of some things
| (with experimental frames)
|
|
Population ,
landmarks ,
other
|
|
|
People seconds
|
|
|
Time ,
landmarks ,
other
|
|
|
Length ,
landmarks ,
other
|
|
|
Area ,
landmarks ,
other
|
|
|
Volume ,
landmarks ,
other
|
|
|
Mass ,
landmarks ,
other
|
|
|
Energy ,
landmarks ,
other
|
|
|
Mass volume-density
|
|
|
Surface volume-density
| Packing surface in a volume.
|
|
Speed
|
|
|
Volume rate
|
|
|
Power ,
landmarks ,
other
|
|
|
Light-speed delay
|
|
|
|
|
Body Ruler
|
|
|
Measuring Angle and Distance with your Thumb
|
|
|
|
top