Posted in Science & Nature

Brazil Nut Effect

Have you ever bought a bag of mixed nuts and noticed that Brazil nuts tend to be on the top of the pile? If you put nuts of various sizes in a bag and shake it, you will see that the larger nuts (such as Brazil nuts) will rise to the top slowly. This is strange as common sense dictates that heavier objects sink to the bottom. The strangest thing? No one knows exactly why this happens.

However, there are some persuasive theories. It has been suggested that the so-called Brazil nut effect is due to a phenomenon called granular convection. Convection is usually used to describe the movement of gases and liquids, where heated particles are more active and lighter, thus rising to the top. As the particles rise, they cool down and fall back to the bottom, creating a current. It seems to be that the same can be applied to solid particles, such as nuts. When the jar or bag of nuts is shaken, a vibrational force is applied. Nuts in the middle are pushed upwards by the vibration, with smaller particles filling the gap below. Once the nuts reach the top surface, the vibration pushes the nuts towards the side, where they are then pushed back to the bottom. However, larger nuts like Brazil nuts are too big to fit in this downward current so they stay on the top. 

The Brazil nut effect is not exclusive to Brazil nuts. A similar phenomenon can be seen with any large particles surrounded by smaller particles, like pebbles in sand or coffee beans in ground coffee. The theory of granular convection has still not been fully understood, with various factors such as nut density and air pressure seeming to play a role.

Posted in History & Literature

War Of The Currents

In the late 1880s, a war raged on in the United States – one that is not commonly known by the public. It was a war between two wizards: Nikola The Wizard of the WestTesla and Thomas The Wizard of Menlo ParkEdison.
This war involved no guns or explosives, but centred on something so commonplace that people take it for granted nowadays – electricity. The two scientists/wizards fought to determine whose form of electricity transmission was better.

There are two types of electric currents used for transmission.
Direct current (DC) was used by Thomas Edison, a pioneer of electricity distribution. Before him, electricity was more of a scientific curiosity and was not widely available to the public. DC is a unidirectional flow of electric charge.
Alternating current (AC) was later developed by Nikola Tesla, also a pioneer in the field of electricity. AC is the alternating movement of electric charge as it periodically reverses direction from + to -.

When electricity first became public, the industry standard was DC, as Edison started his company, General Electric. This was incredibly profitable for Edison, whose inventions relied on the usage of DC. For example, his incandescent light bulb was the principal electrical device during the time. Edison further advanced DC technology and heavily advocated it.
Tesla claimed that AC was a much more efficient mode of electricity transmission and tried to convince Edison while working for him. However, Edison ignored him and stated that it was an insane, useless idea. Edison was more an inventor than a mathematician, so he did not understand the theoretical benefits of AC over DC.

AC has the advantage of being able to use a transformer to gain much higher voltage than DC, while losing less power when transmitted. It also allowed easy conversion from low-voltage use, such as lamps, to high-voltage use, such as motors.
Despite this, Edison refused to accept the system and continued to lobby against it. The most famous case is his drastic attempt to defame AC by showing the public how “dangerous” it is.

In 1890, Edison and his company developed the electric chair, which used AC to demonstrate the safety hazards of Tesla’s invention. He did this by arranging the first capital punishment by electrocution. Unfortunately, due to calculation errors, the first shock was insufficient to kill the convict, William Kemmler. The procedure was repeated for 8 minutes, during which the convict was screaming in agony, seizing due to electrocution, and at one point, caught fire. This horrible image is portrayed quite accurately in the film The Green Mile.

Despite this unpleasant event, AC became the standard over time and DC is now only used in labs on certain special applications. Also, the electric chair was adopted as an official method of execution.