When did a week get 7 days? People first used a 7-day week over 4,000 years ago in the Akkadian Empire. When we think about it, there is no logical reason why a week should have seven days. You cannot divide the year up into 7s. For a while, the French tried a ten day […]
#1488 When did a week get 7 days? Read More »
How does a thermometer work? A traditional thermometer works by knowing how much mercury will expand at different temperatures. An oven thermometer works by knowing how much a piece of metal will expand when heated. And a modern thermometer uses a thermistor, which has a different electrical resistance at different temperatures. The idea behind the
#1487 How does a thermometer work? Read More »
What causes condensation? Condensation is caused by warm, moist air coming into contact with a cooler surface. Condensation happens in a house when the air in a room is warm and moist and then comes into contact with a cool surface. This often happens in winter when it is much colder outside and the heater
#1486 What causes condensation? Read More »
How do CDs and cassettes record information? CDs record information by using pits and bumps, or by using burned colored dye. Cassettes record information by using charged magnetic tape. There are three types of CDs. There are the CDs you buy prerecorded from the shop, CDs that you burn yourself in your computer, and CDs
#1485 How do CDs and cassettes record information? Read More »
What are blisters and calluses? A blister is a pocket of body fluid that has formed between the outer layers of skin in response to damage. A callus is an area of thickened skin that has been formed to protect the skin from damage. The word “blister” came into English from the old French “blestre”,
#1484 What are blisters and calluses? Read More »
How does a gravitational slingshot work? A gravitational slingshot works by using the gravity of a planet to get an increase in speed without expending extra energy, and to change direction without losing speed. A gravitational slingshot is technically called a gravity assist because the gravity of the large body is assisting the spaceship. As
#1483 How does a gravitational slingshot work? Read More »
Why are your fingers stiff when you are cold? Fingers are stiff when you are cold because the body moves the blood to more important organs, because muscles stiffen in the cold, because the joints become viscous, and because the cold can reduce nerve impulses. When our hands are exposed to the cold for a
#1482 Why are your fingers stiff when you are cold? Read More »
Why do onions have so many layers? Onions have so many layers because each layer is a modified leaf that has grown from the center out. When they are first planted, onions grow from a seed. These seeds are produced by flowers at the top of the onion’s stalk. If you think about an onion
#1481 Why do onions have so many layers? Read More »
How does a Polaroid camera work? A Polaroid camera technically works in the same way as a regular camera, except that all of the chemicals needed to develop the photograph are already inside the photographic film that is inside the camera. These days, we mostly use digital cameras or our phones. However, back in the
#1480 How does a Polaroid camera work? Read More »
Why do we blush? We blush in response to emotions such as embarrassment, stress, and shame. Why we blush is a much more difficult question than how we blush, so let’s look at that first. How we blush is fairly straightforward. The red color of a blush is brought about by the dilation of blood
#1479 Why do we blush? Read More »
