What does E = mc² mean? E = mc² means that mass and energy are two ways of describing the same physical thing. In everyday life, mass feels like “stuff” and energy feels like “activity,” but Einstein showed that they are connected. If a system loses energy, it also loses mass. If it gains energy, […]
#1602 What does E = mc2 mean? Read More »
Which of the Seven Wonders of the Ancient World still exists? The Great Pyramid at Giza is the only one of the Seven Wonders of the Ancient World that still exists. The Great Pyramid of Giza is both the oldest of the Seven Wonders and the only one still standing. It was completed in roughly
#1601 Which of the Seven Wonders of the Ancient World still exists? Read More »
How do fish ladders work? Fish ladders have a series of stepped pools that allow fish to swim back up a river and climb over any human-built obstacles that might be in their way. The idea is to mimic the natural riverbed. Salmon are the most commonly known, but there are many different kinds of
#1600 How do fish ladders work? Read More »
Why is someone who crosses a picket line called a scab? The insult goes back to the 1500s, when “scab” had come to mean a low, mean, rascally person—a scoundrel. Strikes themselves are far older than most people assume. One of the earliest recorded strikes happened in Ancient Egypt in 1152 BC, when artisans of
#1599 Why is someone who crosses a picket line called a scab? Read More »
How did John Harrison’s clock allow longitude to be used? John Harrison’s clocks were the first clocks that worked accurately on ships. To calculate longitude, it is necessary to know the time difference between where the ship is and the place it left from. That is only possible with a clock that can keep accurate
#1598 How did John Harrison’s clock allow for longitude to be used? Read More »
What is a fly-by-wire system? A fly-by-wire system is a way of controlling a plane with electronics rather than with manual flight controls. It is called “fly-by-wire” because all of the pilot’s input is transmitted along electrical wires. The opposite of fly-by-wire controls is mechanical or hydraulic controls. These days, passenger planes and large planes
#1597 What is a fly-by-wire system? Read More »
How do supermarkets employ psychology? Supermarkets employ psychology by manipulating your senses, tracking your route through the store, understanding where you look, shaping how you feel, and knowing when you are most likely to buy something. Supermarkets appeared at the beginning of the 20th century. The very first supermarket was the Piggly Wiggly in Memphis,
#1596 How do supermarkets employ psychology? Read More »
How does a building sprinkler system work? A building sprinkler system is a network of pipes and sprinkler heads that are activated by heat, not smoke. A sprinkler system is fairly straightforward. A network of water pipes is laid through the building, usually above the ceiling. At predetermined distances, a sprinkler head sticks through a
#1595 How does a building sprinkler system work? Read More »
What is Occam’s razor? Occam’s razor is a principle that says if you have two competing ideas to explain something, you should always prefer the simpler of the two. It is named after William of Ockham, but he never called it “Ockham’s razor” himself. The basic idea behind Occam’s razor is that if you have
#1594 What is Occam’s razor? Read More »
How does a vacuum cleaner create suction? A vacuum cleaner creates suction by making a pressure difference between the air in the vacuum cleaner and the air outside the vacuum cleaner. However, the dirt is not technically being sucked up into the vacuum cleaner but pushed up. There are two kinds of vacuum cleaners currently
#1593 How does a vacuum cleaner create suction? Read More »
