Archive for the ‘Math’

Friday the 13th is most common 13th

January 13, 2012 By: erik Category: Fighting Stupidity, Geeky, Math, Musings

Friday the 13th Facts and TheoriesI’ve always been fascinated by superstition, and friggatriskaidekaphobia – or, to be more clear, paraskevidekatriaphobia – strikes me as a particularly interesting one. The origin can only be traced back into the 19th century. I am disappointed to discover that experts find little reason to associate it with the slaughter of the Knights Templar on October 13, 1307, exactly seven hundred years before my wedding day. Oh well, something else Dan Brown got wrong. As if to show just how arbitrary the choice of Friday is, the Spanish speaking world fears Tuesday the 13th, and they even have their own tongue-twisting phobia word: trezidavomartiofobia.

How big is the Earth’s shadow on the Moon?

December 16, 2011 By: erik Category: Geeky, Math, Musings, Photos, Science

Earth's UmbraWhen I saw yesterday’s Astronomy Picture of the Day, I was fascinated by just how big the Earth’s shadow is on the Moon. When I made a comment to this effect on Facebook, my friend, Josh Grady, said, “It’d depend on the distance between the two, no?” Of course the size of a shadow depends on the distance to the object its cast upon, but I hadn’t considered that the distance from the Earth to the Moon varies, due to its slightly elliptical orbit around the Earth-Moon barycenter, by 42,840 km, causing it to appear 12% smaller at its apogee than at its perigee. This raised the question: What are the minimum and maximum sizes of the Earth’s shadow on the Moon?

To the geometrymobile!

How fast do you need to drive in the rain to keep your rear window dry?

November 09, 2011 By: erik Category: Geeky, Math

Car Sketch - Rear Window AngleLast week, we had quite the deluge, which coincided, unfortunately, with me having to drive 120 km. I noticed that whenever I slowed down, the rear window would get wet and hard to see out of. Once I sped up again, one wiper pass dried it off and it stayed dry until I slowed down again. This is an obvious scenario for anyone who has ever driven, or anyone who thinks briefly about the physics involved: when you’re driving fast, the rain doesn’t hit your rear window. Out of the blue (or gray, in this case), my mouth spoke the words, “I wonder what’s the minimum speed I have to drive to keep the back window dry?” My wife immediately intuited that “it depends on the shape of the car”, by which she meant the angle of the rear window. This insight made the original question all the more interesting to me, because it gave me an equation to plot! Are you getting excited yet?

Country Roads

October 21, 2011 By: erik Category: Beach, Math

Flower at SunsetMy photography walk last Saturday that first went by the fishing harbor then turned inland. My camera and I admired autumn’s fanfare and the sunset’s long shadows. Some may search for the exotic with expensive holidays to Sharm el Sheikh, but with the right eye and attitude, a simple walk around the place where you live can be an exotic adventure.


Photographing Positive Integers

February 22, 2011 By: erik Category: Geeky, Math, Photography

Five Positive IntegersWhile they are still only fun to her as colored objects and not the mathematical concepts they represent, Nora very much enjoys playing with these foam numbers we bought for a few pennies at the local chinos. The other day I was goofing around with them as she was popping them out of their placemat-sized sheet and handing them to me, and I noticed that they could be interlocked in sequence. It was then that I thought they might make an interesting subject for photography, so I waited until Nora’s interest moved to another toy and went to get my camera.

Fun With Arithmetic

July 16, 2010 By: erik Category: Geeky, Math

Solutions to Friday Puzzle by Goal ValueI’m an avid reader of Richard Wiseman’s blog, and I find his Friday Puzzles to be particularly fun. Today’s puzzle is as follows:

How can you place the arithmetical signs ‘+\’ and ‘-\’ between the consecutive numbers 123456789 so that the end result is 100? So, for example, you could go…..

12+34+56-7-89 , but that would make 6, so that doesn\’t work.

Try to come up with the method that uses the least number of symbols.


Optimizing Picture To Border Ratio With Phi

January 07, 2010 By: erik Category: Art, Geeky, Math

Frame Geometry DiagramThe other day I was looking at a framed photo in my house and wondering how the area of the border around the picture (called a mat board in the framing industry) compared to the area of the picture itself. Immediately I remembered the master of all aesthetic ratios, the golden ratio, Phi! 1.61803398874989… I thought, “I bet if the ratio of the area of the picture to the border was Phi, it would look good!” So I set off on an algebraic quest to find the answer…

Can Sarah Palin really see Russia from her house?

September 25, 2008 By: erik Category: Geeky, Math, Politics, USA

Any intelligent person knows that Sarah Palin was joking when she said that she could see Russia from her house. It’s pure hyperbole. But everyone in the media keeps repeating it over and over, and I’m certain that some people probably actually believe it to be true. I bet that even the people that understand the hyperbole probably don’t realize just how much of an exaggeration it really is. So I decided to use my Distance To Horizon Calculator to see just how tall Governor Palin’s house would have to be in order to see the Russian coast.

My Favorite Flower

June 19, 2008 By: erik Category: Math, Photos, Religion

Passionfruit FlowerThe flowers of Passiflora edulis are gorgeous. I particularly like the Fibonacci numbers of stamens, three of one kind, and five of another. Fibonacci numbers are, of course, related to the Golden Ratio, which is pretty much the mathematical definition of beauty.

At this time of year, these passion flowers are blooming vigorously here. Later, they will turn into passion fruit. (more…)

Too much Phun

May 18, 2008 By: erik Category: Geeky, Math, Science

Choppy SeasIt might not be possible to have too much fun, but it’s definitely possible to have to much Phun. Phun is a “2D physics sandbox”. What that means is that it allows you to draw shapes (circles, squares, or arbitrary freehand shapes) and then lets you bang them together using simulated physics laws. Check out the video at the link above for a demonstration.

Phun is exactly the kind of computer “game” that my brain adores. I used to play hours and hours of The Incredible Machine, which is a very similar concept. For me, at least, Phun is seriously addictive. It’s like crack for Newtonian physics lovers.