John Dilsaver

June 16, 2012: The recent Transit of Venus
When weathermen predict things it's a coin toss, when politicians predict things you might as well bet the other way, but when astronomers predict things, they happen right on schedule. After a full day of plumbing on an outside hydrant here at the house I quickly threw the telescope together in the backyard to watch the transit of Venus. This was on June 6. First contact occurred at about 5:05 CDT.

The most recent transits I had viewed prior to this was the Nov 15, 1999 transit of Mercury, which I viewed at school with students, and June 2004 with the transit in progress as the sun rose, again viewed at school. This time, after viewing the Venus transit at home for awhile I packed the scope into the car and went to the Library Center, just south of Springfield, to join the Springfield Astronomical Society in their public viewing. Former student Dale Trantham, who had viewed the 1999 transit with me was at the library center and took the pic below at right.

After having seen Venus through the scope many times before, it was nice (and almost surprising) to see it as a disk. Venus, being closer to the sun than Earth, exhibits phases when viewed through the telescope, and ranges from a gibbous appearance not too dissimilar to a disk when far from us, to a very thin crescent when closer. In fact the closer and brighter Venus is, the thinner the crescent is.

I was projecting the image through the telescope onto paper (yes, that is a legal pad) and this is possibly less impressive that the view through the scope through a filter, but it is safe and has the advantage that a small group can all view at once. The viewing at the library center did attract a large crowd.

Galileo would have loved the transit. He'd written about the phases of Venus, after having discovered them. He discovered many of the basic facts about the solar system--- craters on the moon for example, and the "Galilean" satellites of Jupiter. Offhand, I don't know if Galileo ever viewed a transit, I doubt it. A number of nice sunspot groups were visible during the transit and he'd have enjoyed viewing those.

If one realizes the diameter of Venus (almost exactly the same as Earth) is about 8,000 miles, and the diameter of the sun is a little more than 800,000 miles, and that the lines on the legal pad give a convenient way to measure the relative sizes of the images of each object, one can do a little work and figure out the relative distances of the Sun and Venus during the transit.

June 12, 2012 here are some pics of recent work on the older bike..

April 30, 2012 Geometry teachers, physics enthusiasts and fans of flexagons should check out this.

April 23, 2012 SATO48 2012

I made the credits of a video in SATO48 2012. The inspiration package for 2012 included two Pez dispensers and the words Lover, Inventor, Founder, and Mentor. One of these words had special meaning for me. So, I was pleased when my younger nephew Shelt asked if some scenes could be shot here.

A couple of articles of mine make cameos, and I recognize a certain hat that appears about half way through. I got to jury rig a Jacob's Ladder.

[Please note that making a Jacob's Ladder (climbing arc) is dumb (and potentially lethal) if you are careless and don't know what you are doing.]

Video can be found here.
(Link updated 9.29.2912)

Feb 1, 2012 Pascal's pyramid.

I played around with the three-d version of pascal's triangle (Pascal's Pyramid) recently using toothpicks and marsh- mallows. Nothing remarkable, but it was great fun. Being able to pick the model up and manipulate it helps me understand. Has any one out there found an effective way to model (a+b+c+d)^n?

Ok, yes, it's just toothpicks and marshmallows.

Think about the models of 4-d hypercubes that you've seen. I've seen plenty of two dimensional pictures of the 3-d shadows of 4-d hypercubes. Maybe some approach along those lines . . . . If by any chance you've spent some time playing around with pascal's pyramid especially with model building you are invited to email me an

Dec 21, 2011
Well we all know the world is set to end on 12.21.2012. So with that in mind a small group is having a bonfire at our forest property this afternoon, provided we can get 300+ dead cedar trees to ignite. It's sort of a "T minus one year, and counting" event.

How high wll flames go from a (slightly damp) 15 foot tall pile of cedars? For those who like fire it should be an excellent experience. Here is a pre-fire satellite image.

Assuming all goes well I will report after Christmas. Friends in Springfield might want to glance south this afternoon to see the smoke pillar, - - - or advancing flame front.

The pic at the right is an occasional guest seen on the game cam pics wandering around the property. I'm not quite sure how big bobcats get in Missouri. I read that out west they approach 60 lbs.

Nov 16, 2011

I'm going to try to post a couple problems from math club.
I'm playing around with ways to post them online.

May 27, 2008

Today's ans:
1. -1
2. 1
3. 0

Feb 25, 2008

A great day for fenders.

I participated in a Ralph Ride today (Sunday).. This was in preparation for the spring brevet season. Brevet are distance rides often of 200 km (125 miles) or more. Last year Ralph and I completed a 400K as our longest ride of the year. At least it was my longest ride. Many brevets are sponsored by RUSA.. The brevet season goes in something of a four year cycle with the Paris-Brest-Paris ride every four years being the pivotal event of the cycle. Since 2007 was a PBP year, this particular ride won't occur again until 2011.

Anyway, I rode to Springfield and met Ralph and Tom downtown at noon. I promptly had a flat about two miles into the ride. Actually I had two flats, but I managed to only have to change the tube once. After I got the tube out I dug two nice sharp gravel pieces out of the tire casing, replaced the tube and rode on. Later when I patched the tube at home, I found the tube had two separate punctures. At least I didn't have to stop twice.

The temp was about 36 deg F at its highest so it was a cold ride. I hadn't been riding much so it also felt like a long ride. Snow and ice melting everywhere had the roads a little wet and yucky. It was a nice day for fenders. Tom was sporting a set of fenders on his bike, way to go Tom. On the way north to Springfield just as I was getting to the greenway trails, I passed a couple pedestrians (who gave me a strange look as I rode past at 12 to 15 mph) and then as I looked ahead after passing them as I rode onto the bridge, I noticed the bridge floor was still ice covered. Yikes. Those pedestrians had just walked across the ice covered bridge. I coasted across holding a very straight line as my heart rate increased as my speed slowly decreased. Very exciting. Above left is the way my driveway looked as the ride started. At the right is the Finley, between Ozark and Linden. Spring, where are you?

Feb 20, 2008
Just a couple quick thoughts. Tonight may be the night we (the US) tries to shoot down spy satellite USA 193. Also, there is a lunar eclipse tonight. For info on where in the sky to look to see these events, go to Heaven's Above a great website.

Jan 28, 2008
So, life is somewhat different when you're a mathematician (or even a high school math teacher). I walked into my favorite restaurant for breakfast this morning. Instead of pouring coffee and taking my order the waitress (hi Gjetta) posed the following problem: "which would you rather have, $100,000 or one cent plus two cents plus four cents, with the doubling pattern continuing for 30 days". Well, it's the old inventor-of-chess and grains of wheat problem more except it's 30 days instead of 64 squares.

Before morning coffee, my estimation went like this. I know 2^10 is 1024, that's about 1000, so 2^20 is about 1000x1000= 1,000,000 and 2^30 is about 1,000,000x1000 = 1,000,000,000. since we're using pennies not dollars, I divide by 100 to get 10,000,000, which is close enough for 6 am.

[For the mathematically astute: yes, the sum only goes to 2^29 since the first day is 2^0, and the real answer is 2^30-1]

At the right is a pic I've been meaning to post from last summer's ride in Colorado. This is on the peak-to-peak highway south of Estes Park.

6 Oct. 2007

All files should now download as .pdf's

30 Aug. 2007

Hi. Welcome to my website.

Last year my nephew Joshua (hi Josh) gave me this domain name as a Christmas present. I didn't have a clue what to do with it, but as this school year begins I guess I'll try to post some files, pictures, and who knows what else here online.

Way-back in the day of 6502 assembly language, cassette tape data storage, and actual floppy disks I used to enjoy programming. So, I thought I'd actually try to write the code rather than use a web-development utility. Since I am a complete beginner at html this will be a very simple webpage.

The photo above is from a bicycle trip to Massachusetts two summers ago. Bicycling is one of my hobbies. This summer I took the bike to Colorado and climbed the rockies. Both trips were lots of fun. I'll get some more pics and info about the bike on here before too long.

Right now the files are word files, they'll eventually be .pdf's. If you'd like to contact me my email address is

Some files of interest to my students

Policy Statement
Confirm reading PS
Assignments, (partial list, but getting better!)
Solutions, partial list
Alg/Geo review Week 1
Homework format.
Radian activity
Study Guide B1, Quiz 1
Key - Quiz 1
Study Guide A1, A3, A4 Quiz 1
S G A1, A3, A4 Quiz 2 (8.30)
Study Guide B1 Quiz 2 (8.31)
Key Quiz 2 (8.31.2012)
Key Quiz 2
Study guide QZ 3
Key Quiz 3
Geogebra Triangle Proj 1
Key Quiz 4
Study guide QZ 5
Quiz 5
QZ 6 Key
QZ 7 Key
QZ 8 Key --- Monster quiz
QZ 9 Key (Two versions)
QZ 10 Key
QZ 11 Key
Geogebra 10.2.2012
Angle as Rotation
Geogebra turn in
Quiz 12
Quiz 13
Study guide quiz 14
Study guide Final Exam

Feedback link
Closed classes 3.20.2013


Policy Statement
Day 1 problems (ok, it's 2013)
Counting "Day 2"
15.1 Notes
Assigned probs
QZ 1 Key
QZ B1 Probs, not key
Key 1.25.2013
Slides 15.3
Demo geogebra chain of reasoning
Quiz 2.1.2013
Video inst. old
Slides 15.4
Quiz probs 2.15.2013
Math Carnival
Quants,Ch 2
Key 3.1.2013
Key 3.8.2013
Series problems, 3.20.2013
Method of finite differences
Key 4.5.2013
Notes 4.8.2013
Key 4.12.2013
Key 4.19.2013
State Math Probs

Policy Statement
Confirm reading PS
Assignments, partial list
Keys to A1 - A8
A2.5 handout
Ch 1 scan (2.8 mb)
Key to QZ1
Key QZ 2
Key QZ 4
Key QZ 6
15 Sept 1997 Handout
Measurement Lab
Lab Report Instructions
Sample Lab Writeup
Ch 2.pdf
Ch 3.pdf
Video Instructions
Static Demo (vintage)
Physicst zipped
P 532
Takehome QZ 1.18.2013
Bridge files
Rules 2013

AP Physics
Policy Statement
Confirm reading PS
Mech Assign
Sept 11 Probs to present
QZ 1.23.2013
Ch 18
Ch 19
Ch 21
Ch 22
Ch 26
Fun probs for ch 20--ish 1.31.13
EM Assign
Wave Assign
Perlmutter Version 1
Perlmutter Version 2
specific heat of water

Some random articles
Solar Swan Dive (1 meg)
Erdos Number Project Stuff (>1 meg)

Math club
Triangular numbers

Upcoming Math Events
GPML Dates and Sites
Remainder Theorem

Geogebra files.
Mostly stuff I wrote
Stuff for Rick, 2.22.2012
More for Rick, 2.22.2012
parabola demo 10.30.09
Mark's proof
SWMDAMT 3.12.09 Outline
Parabola using sliders
Sine, sum formula
Law of Sines
Euler Line
Centripetal Force, details
Centripetal Force, final diagram
Parabola, vertex form
Parabola, factored form
Parabola, standard form
Geo Const of Parabola.ver2
Trig Sept 2012

Geogebra for 10.2.2012
A selection of hastily written files by me
Squaring the Rectangle ver 1
Squaring the Rectangle ver 2
Squaring the Rectangle ver 3
Squaring the Rectangle ver 4
Squaring the Rectangle ver 5
Construct a parabola
LaTex tutorial
LaTex symbols

Geogebra for 10.23.2012
A couple more sketchy files
Dropping ball thing
Flagpole solve a triangle
Running in a circle

Student drawings
Disclaimer - not every statement made by every student in every drawing is guaranteed to be correct!
1864 Identity 1
Non Triangle
sine sample v4.0
Nice pythagorean proof
Locus tutorial-(req speakers)
.pdf files
Some Q's written using Geogebra
Introduction to Geogebra
Dave's Parabola Activity
Links 9.23.09
Geogebra Icons, - word form
Geogebra Icons, - .pdf form

Linden Route ideas
boring math stuff one
boring math stuff two
boring math stuff three
boring math stuff six boring
boring 7 boring 7 boring 7
boring 8 boring 8

Flying pumpkins?
Trebuchet Video

You Tube
Physics video
Mr Nimmo
Mr E Parallelogram1
Erickson's decagon

Dull Boring Physics video 1
Dull dull dull Physics video 2
copyright schmopywrite dreadfully dull beyond belief 3
Mr D's Marbles

-- Links --
To a variety of interesting sites.

AMC Am Math Competition
ARML local group
Missouri State Problem Corner
The Art of Problem Solving
Ralph's Rides
RUSA (distance cycling)
Heaven's Above
For Lauren's Mom
More for Lauren's Mom
More&&More for Lauren's Mom
The Ray Godfrey construction
Cedar pile from space
Big Wind Generator

Low carb
Why you don't want the experts to tell you what to eat.
The low carb cycling company
Grandpa hoeing 1947
Mark's Daily Apple
stuff for january
NuSI - research on nutrition