Friday links

It's the anniversary of the 20th of July plot, the unsuccessful bomb attempt to kill Hitler in 1944.

A brief history of prosthetic limbs.

The Bayeux Tapestry with knobs on: what do the tapestry’s 93 penises tell us?

On July 20, 1969, Neil Armstrong walked on the moon. 

The Scientific Quest For the Perfect S'more.

Ye Oldest Public Library in the English Speaking World.

ICYMI, Monday's links are here, and include the physics of how lawn mower blades cut grass (at 50K frames per second), spiders flying by using electricity, and the anniversary of the beginning of the atomic age (the 1945 Trinity nuclear test).

Monday links

The Physics of How Lawn Mower Blades Cut Grass (at 50K frames per second).

Photos That Prove Japan Is Not Like Any Other Country.

Spiders Can Fly Hundreds of Miles Using Electricity.

On July 16, 1945 the atomic age began with the Trinity nuclear test. Related: 1954 film: How a Clean, Tidy Home Can Help You Survive the Atomic Bomb

Kazakhstan tax dollars at work: this 40 foot tall squirrel statue is part of an art project commissioned by city authorities.

Man Spends 23 Years Carving Sprawling Underground Temple Under His House.

ICYMI, Friday's links are here, and include why Friday the 13th is considered unlucky, the history of trial by combat, Bastille Day, Mozart's less family-friendly works, and how local authorities are surveilling U. S. citizens.

The Physics of How Lawn Mower Blades Cut Grass (at 50K frames per second)

Interesting Engineering on Smarter Every Day's super slow motion video (below) of a lawnmower:

...an ordinary lawnmower sucks air up into the mower body causing the grass to stand vertically, which allows the blade to slice evenly at the bottom of the grass.

To demonstrate this in another way, a vacuum hair clipper does the same thing. It sucks hair into it before it is cut so that a really precise cut can be made. The lifting of the grass is actually caused by the tab on the back of the mower blade which causes air lift and raises the grass up.

By filming a lawn mower in action with a super fast camera, that in turn gives wonderful slow motion, you can see the blades of grass being lifted up just before being cut.