Big Think

Why does one’s leg tingle when sit down? The leg "sits up" when the peripheral vessels in it are constricted. The nerve receptors in the limbs are sensitive to the lack of oxygen and respond by shutting down (stopping working). This can be felt as numbness. When the blood supply is restored, the receptors initially generate signals on their own, without external influence. These signals are felt as tingling or goose bumps.

Why cannot you wake up to a bad smell? Recent research from Brown University has revealed the function of smell sensation is altered by the brain during sleep. Although certain substances can affect body activity, we can't wake up from the smell itself. For those who thought of ammonia. It is one of those substances affecting the brain — it stimulates the respiratory and vasomotor centers of the brain and causes increased breathing and increased blood pressure, resulting in waking up.

Why is the whistling sound stronger when it's raining? The reason is that when it rains, the air is damp, i.e. its density is greater than in dry weather. That's why sounds are better transmitted. In rainy weather, for instance, you can hear a train driving on the railroad, especially at night, although at other times you cannot hear it. The molecular weight of water (H20) is smaller than that of the main components of the atmosphere: oxygen (O2) and nitrogen (N2). The lighter the molecule, the higher the speed of sound.

Why do the batteries in a flashlight run out on their own? There are wires running from the battery terminals to the flashlight switch. Even if the circuit is open, the distance between the switch pins is about a millimeter. A weak current can flow through this gap and discharge the batteries. To avoid this, insulate the battery from one of the contacts with a couple of layers of polyethylene or take them out of the flashlight when not in use.

Why does snow shine in the sun? Cause of the crystalline facets. Snowflakes are ice crystals with numerous flat facets that act as microscopic mirrors. Those that reflect sunlight directly into the eye provide a bright dot. As soon as one moves a little bit, the rays of other snowflakes fall into the eye. Therefore, when moving, the shiny spots replace each other. Freshly fallen snow is shinier than lain down, as the flat edges of snowflakes scratch, break, and melt with time.

Why do some animals have vertical pupils while others have horizontal ones? A vertical pupil allows predators to see vertically oriented objects, such as their prey, sharper. Herbivores, on the other hand, only need to view a wide horizon to spot a predator in time, so their pupils are frequently adapted to see horizontal lines more sharply.

Why are raw potatoes unpalatable? Due to the starch in their cells. Though it cannot be seen, you can easily obtain it if you grate the potatoes, pour water on them, and then strain and let them stand. A white sediment is sure to precipitate in the water. That is the very starch which makes raw potatoes bland.

Why do people pay for movie minutes in Germany? Cinema tickets in Germany are expensive, they can cost around €10. That's why it's a good deal for film lovers to buy a monthly pass for €23. Yet you have to pay for extra minutes of film: a subscription includes films of 120 minutes, and time over this limit is paid separately. There is even a special term for this phenomenon: Überlängenzuschlag.

Why cannot gasoline be put out with water? Why are ignited objects put out with water? The point is that combustion is the process of combining a substance with oxygen, so the main purpose of extinguishing fires is to limit the flow of air oxygen to the burning material. Extinguishing with water is the cutting off of oxygen to the burning object, since water, by wetting it, envelopes it (besides, water lowers its temperature). Gasoline isn’t mixed with water, and at the same time, is lighter than water, so it just floats up, while keep burning. In addition, it will begin to spread with the water, increasing the fire area.

Why do sharks not sleep? It used to be thought that sharks don't sleep at all as they need to be in constant motion to pass water through their gills to breathe. Therefore, it seems that a shark cannot sleep since it needs to swim all the time. Still some evidence from physiologists suggests that these sharks may be able to swim and sleep simultaneously. The nerve center responsible for contracting the muscles that move the body is located in the spinal cord, so theoretically they can turn off the brain and doze off on the go.