o c e a n b l o g
We’re saddened by the passing of our friend Maya Angelou. Thank you for all you’ve done, and for all the hugs.
Chain link armour was used throughout the Mediaeval World.
The chain helped prevent swords and similar objects from piercing the body. In Europe it was paired with thick, heavy plate armour for maximum protection. In this set up, chain was primarily used over the joints, places where more flexibility was required.
Though armour was a necessity during war, plate armour came with a series of issues. Plate armour is expensive, heavy, and susceptible to the weather- if it was hot, the metal would warm and you would heat up, if it was cold, the metal would cool, and you would freeze. While adaptations were made, such as wearing a tunic underneath, there was never a perfect solution. The daily temperature extremes in the Middle East allowed armour to evolve differently. Though plate armour was used, chain was much more predominately specifically over the arms and legs. Coupled with smaller horses, chain was ideal for the Middle East.
The chain above is from what is now modern day Iran.
Written by @kironcmukherjee. Last update: May 27th, 2014.
Mason jars aren’t just for jams and drinks guys. They’re all about salads now.
A bit of #math today #circlearea
▼ Reshared Post From Richard Green ▼
Circumference and area of a circle
The circumference of a circle of radius r is given by the formula 2πr, where π is the famous constant whose value is approximately 3.14159265. This graphic by Margaret Nelson illustrates a simple way in which the formula for the circumference can be used to obtain the formula for the area of a circle, πr^2.
The idea is to cut the circle into a large, even number of equal sectors, as if you were slicing up a pizza. These sectors can then be rearranged into an approximately rectangular area. The upper edge of this area is made out of pieces of exactly half of the circumference, and the same is true for the lower edge. Half the circumference is πr, and the width of the area is approximately equal to the radius of the circle, which is r. The area of the roughly rectangular area is the same as the area inside the original circle. This area can be approximated by a rectangle of dimensions πr by r, which would have an area of πr^2. In the limit as the number of sectors tends to infinity, this approximation will converge to the exact value of the area.
Nowadays, formulas like this for area and volume are proved using calculus, but this elegant argument is a much older idea and goes back as far as Archimedes. It is not so important that the circle be cut into an even number of sectors, because an odd number of sectors will still give a good approximation if there are enough sectors.
The picture comes from an article in the February 2014 edition of the Mathematical Association of America’s magazine Math Horizons. The article is an interview by Patrick Honner of the mathematician Steven Strogatz. Strogatz is a professor at Cornell University who likes to cite this proof as a good argument with which to convince people of the beauty of mathematics.
You can read 's article here (http://goo.gl/jZWUTB). His own post about this (https://plus.google.com/+PatrickHonner/posts/dVxDP4Nh8t7) includes a picture of the rearrangement of sectors of an actual pizza.
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