A View from the Back of the Envelope
Using `back of the envelope', easy approximate reasoning to understand the world. Fermi questions, powers of ten, orders of magnitude, etc.
[... (1997.Mar.27)]

Scale models of the solar system
Educational human-wander-around-in-it type orrerys. A collection of links.
[... (1997.Mar.04)]

An Exponential Notation Meta Page.
Resources on exponential & scientific notation.
[... (1997.Jul.11)]

The Monty Hall Problem - a state-space explanation
Yet another page explaining the answer to the Monty Hall Problem.

Software engineering - our maze of twisty passages, glowing bright
Software development can be pictured as a heatsink, a maze which takes vast societal resources and dissipates them.

Where is China? It is down over there...
If looking down, you could see through the earth, you would see the lands on the other side.

Measuring length with your body
Throughout history, people have been using themselves to measure length. You can too. Here is how to calibrate yourself.
[1997.May.05 (1996.Dec.17)]

Measuring angle & distance with your thumb
[1997.May.05 (1997.Mar.25)]

The atmosphere above maps
It can be fun and educational to picture the atmosphere above everyday roadmaps. A state roadmap has about a 1 inch atmosphere, with the space shuttle 1.5 feet up.
[1997.Jul.19 (1996.Nov.15)]

Pacing Earth's history using galactic orbits
Earth has circled the galaxy 18 times. The dinosaurs died out 2/5's of an orbit ago. Fish began almost 2 orbits ago. Multicellular life, about 4. This way of describing time is perhaps complimentary to the usual n million years ago.
[1996.Dec.29 (1996.Dec.20)]

Order-of-magnitude calculation - a "you are already doing it" introduction.

Moon's lighting tells in which direction the sun is.

Excerpts from Butler Lampson's paper "Hints for Computer System Design"
A taste until ACM gets it online. They have.
[(1997.Jan.02) 1999.Mar.03]

The opportunity for a flexible bibliographic format
It would be nice to smoothly and selectively trade cataloging effort for bibliographic quality. But existing bibliographic record formats dont support this. Most are targeted at particular needs, and are both inflexible and intolerant of detail. MARC can handle detail, but was intentionally designed to coerce a "professional" level of effort. I know of no good candidates.
[1996.Dec.18 (1995.Feb.17)]

Personal research notebooks can enrich one's thought. Here are some accumulated suggestions on their use.

Functional notation for derivatives...
is a nice alternative to .
[1996.Dec.05 (1996.Nov.23)]

Snowflakes swirling by like stars
Hmm... If snowflakes are 10's of centimeters apart, and stars light years, thats a 10^17 scale difference so the snowgalaxy is 1/2 mile across. And flakes are stellar envelopes with little cell-sized stars embeded within...
[1996.Dec.11 (1996.Dec.06)]

What is 30 years in the life of a nation?
A clueless television newsperson said `30 years is a long time in a person's life, but only a microsecond in the life of a nation.' But what is it really?

Comments encouraged. -
  Rethink layout.  Date create, date modified, "interest".
  Add misdesign?

  1998.Oct.15  Added `Monty Hall Problem'.
  1998.Jul.08  Added links to `Exponential Notation', `China is down over there'.
               Shuffled entries.  Minor format change.  Added Doables.
  1997.Jun.01  Added `What is 30 years in the life of a nation'.
  1997.May.05  Redirected `Back of the Envelope' its to new site.
  1997.Mar.25  Added BodyRuler angle/thumb/distance.
  1997.Mar.11  Added "Order of magnitude / you are already doing it".
  1997.Mar.04  Added "solar system scale models".
  1997.Jan.19  Added "moon points at sun".
  1997.Jan.02  Added Butler's Hints.
  1996.Dec.20  Added "earth history as orbits".
  1996.Dec.18  Added "flexible bibliographic format".
  1996.Dec.17  Added "bodyruler".
  1996.Dec.06  Added "snowflake stars".
  1996.Dec.05  Added links to "notebooks", "map atmospheres", and "functional derivatives".
  1996.Nov.17  Created.