Why They Don’t Fill Soda Bottles to the Top

Soda bottles are always filled in such a way that there’s some space between the liquid level and the cap. That’s because these drinks contain carbon dioxide. This gas can expand if the bottle gets heated. If there’s no air gap in the bottle, it’ll break because of the pressure building inside.

Also, when you open your drink, the gasses go out in the form of bubbles. And the drink is likely to overflow. The gap helps with this problem too. (Except if you shake it up first, then open it. No, I’ve never done that.)

There are sounds most people can’t stand, like the sound of a fingernail on a blackboard or someone scratching a window. Such noise irritates the amygdala. That’s a small part of your brain controlling your emotions — including fear and survival instincts.

Some cheeses have holes in them. They’re called “eyes.” These “eyes” are made by bacteria used in the process of production. When cheese is almost ready, these bacteria release carbon dioxide. And this gas forms bubbles that later become the cheese’s “eyes.” See?

Cats knock different things over because of their hunting instincts. Your cat is simply checking whether the thing is alive or not. Or it might want your attention. Cats are smart and know that humans come very fast when something is broken.

When the pizza dough is ready, it gets manually spun in the air. This process removes lumps and creates its circular shape. It’s more convenient to bake a round pizza — this way, it gets heated evenly. Plus, it’s easier to cut a round pizza into equal parts.

There have been reports of raining frogs, fish, and other unusual stuff dating back to ancient civilizations. Strong winds, such as those in a tornado or hurricane, sometimes get so powerful that they can lift up a school of fish or frogs and “rain” them somewhere miles away.

Lightning is never a triangle, straight line, or circle. It always has a zigzag shape. Lightning is an electric current, and it always takes the path of least resistance. Air is uneven and irregular, containing dust particles, gases, and other substances. Lightning just seeks the best way through.

Flowers have different colors because of the color pigments they contain. But there are other factors, for example, the amount of light they receive while growing. Or the temperature of the environment around them. Even the pH level of the soil can have an impact on flowers’ coloration.

By tilting their head, dogs try to understand all you’re saying correctly. It’s the way to adjust their ears to the sounds they hear. It may also be a way to show their empathy to the owner. Or they got something stuck in there.

Tickling is bound to cause a laughter reflex. But nothing will happen if you tickle yourself. That’s because there will be no element of surprise — your brain knows what you’re going to do.

Barcodes speed up the purchasing process. If a barcode consists of 12 digits, the one on the very left is a system identifier. For example, two means it’s a randomly weighed item. Three is used for products related to health. The next five digits identify the manufacturer. And the following five are the product’s numbers. The last one is “the check digit.” Scanners need it to make sure they’ve read the code correctly.

The song is bound to get stuck in your head if its music is simple, the text is repetitive and short, and the rhythm makes you move. Another reason you might have an earworm is that you hear some songs too often. And your brain can easily detect them.

Highlighters are filled with a special semi-transparent fluorescent ink that can glow in dim light. Yellow and light-green hues are the most popular because they don’t prevent you from seeing the text after black-and-white photocopying. Photocopiers perceive yellow and light-green marks as very pale and don’t print them.

With age, your hair loses its natural color. It happens because keratin receives less pigment. As people grow older, the pigment cells in their hair follicles gradually vanish. And hair becomes gray. Some time passes, and no pigment is produced at all. That’s when hair turns white.

Trees stop growing at a certain age. It might be because when a tree reaches a particular height, it gets difficult for it to pull water from the soil. Because after that, it needs to pump it all the way up to the top — and that’s when gravity comes into play. Some trees, like the baobab, start growing out instead of up once they reach their full height.

Your own body makes mosquito bites swell and itch! A mosquito breaks your skin. Your immune system perceives the insect’s saliva as a foreign substance. So it starts a special reaction to flush the intruder out of your body. A compound produced by the immune system, called histamine, makes the blood flow faster around the bitten area. And it causes swelling. The histamine also sends a signal to the nearest nerves, which makes the bite itch.

Geese usually fly in a V-shaped formation to conserve energy and make sure none of their team members gets lost.

You can’t hum while holding your nose. Trust me. During humming, you exhale air. But when both your mouth and your nose are closed, the air can’t escape. The longest you can hum like this is two seconds. Then you’ll have to open your mouth and catch your breath.

Road and construction workers are usually dressed in orange because the bright orange hue is visible even in bad weather. It’s the most effective color to attract attention and alert people. No wonder lots of safety jackets and traffic cones are orange as well.

Modern-day perfectly round coins used to be shaped randomly or had no shape whatsoever in the past. But dishonest people stole valuable metals the coins were made of by chipping their corners off. Of course, it was illegal. To prevent this kind of fraud, they invented round coins. After that, it instantly became obvious when coins had been fiddled with.

Most ambulances have this word printed on the front of the vehicle — which is the word “ambulance” backward! It’s written in reverse so that the driver in front of the ambulance can see the word properly in their rearview mirror. Then they can move out of the way and let the ambulance pass.

White is the most popular color for painting aircraft. It reflects sunlight most effectively, which doesn’t let the plane heat up too much. All kinds of cracks, dents, and other damage are much more visible on the white background. It means the fault can be spotted and repaired as fast as possible. And finally, it costs less to buy white-colored airplanes because it’s the color they have “at birth.”

Unlike what many people believe, adding salt to water won’t make it boil faster. It’s true that saltwater gets hotter more quickly than the regular one. But its boiling point is also higher since salt adds some extra mass to the water. So it won’t make things speed up.

The first basketballs were brown because they were made of brownish leather. But such balls were difficult to see both for players and for fans. To make the basketball more visible, they decided to make it orange. Ooh, like the traffic cones...

Flamingos are born gray. But they turn pink because of their diet: a lot of tiny shrimps and blue algae. Both of these products are packed with special pigments. When the flamingo’s liver processes these pigments, special molecules travel to the bird’s legs, bill, and feathers, painting them pink.

Donuts are shaped like rings because, otherwise, they might get overdone at the edges but uncooked and gooey inside. With a hole in the center, both the outsides and the insides get ready at the same time.

Bears don’t sleep for months during hibernation. Instead, all the processes in their bodies slow down. They don’t need to eat or drink. But they can still react to any unexpected things going on around them.

You see the Sun as yellow or orange because the atmosphere of our planet scatters such colors as blue, green, and violet. This is also why the Sun looks warmer at sunrise and sunset.

Emergency services use two colors of flashing lights, red and blue. The red one is associated with warning and danger. It’s also one of the most noticeable colors. But this color can get lost in heavy traffic because most cars have red tail lights. That’s when blue flashing lights come in handy.

Your tongue doesn’t have separate bitter, sweet, sour, or salty sections for tasting. Each of the 8,000 taste buds you have on the tongue, the roof of the mouth, and even in the throat can detect all the tastes.

Lots of private houses have triangular-shaped roofs because this allows rain, snow, and fallen leaves to slide off the slope. If all this stuff piled up on top of your house, one day, your roof would collapse.

Kangaroos have muscular legs, big feet, and tails that allow them to move forward really fast. But the animals can’t go in the opposite direction. That’s because of their body construction.

Leather often looks dull to the eye because it’s covered with itsy-bitsy scratches and scrapes. They scatter the light that hits the material. When you coat your shoes in a layer of wax, you fill these tiny crevices. The surface becomes smoother, and the rays of light bounce off it more evenly. That’s why the leather looks shiny.

Bread tag colors indicate the day when the bread was baked. For Monday, they use the blue tag. Tuesday is green, and Thursday is red. Bread bags have white tags on Friday, and on Saturday, they are yellow. This makes it easier for grocery store employees to remove stale bread from the shelves and replace it with freshly baked ones.

Wimbledon tennis balls are always stored at 68˚F. The temperature can influence their bounciness. When the ball is warm, gas molecules inside it expand. This makes the ball bouncier. After the ball cools down, the molecules shrink. This decreases the bounciness.

When a storm is coming, clouds seem to turn dark. But it’s just an illusion. Thin clouds on a sunny day let the light through easily. They also scatter all the colors of the light spectrum. This makes us perceive the clouds as white. But the thicker the clouds are and the more water droplets they contain, the less light they let through and the darker they look.

Modern light bulbs come in all shapes, styles, and sizes. But in the past, all light bulbs used to be spherical. This shape made the glass stronger and less prone to breaking. And the sphere worked best when it came to delivering light evenly.

If your blender stops chopping food and just spins it around in circles, you’ve probably skipped the “pulse” button. Most modes make the ingredients move around in the same direction at the same speed. But the pulse function creates turbulence. And instead of rolling around, fruit pieces fall into the center and turn into a smoothie. I like smoothies.

The markings on the bottom of a toothpaste tube are there for the factory robots. Colorful squares mark the line that helps the machines understand where to cut and fold the tube.

Green and black tea come from the same bush. The leaves get their different tastes and look after they get harvested. Green tea is withered and heated through steaming. And black tea is crushed or curled and then left to oxidize and darken.

The stop sign has an eight-sided shape to help drivers recognize it easily — even if they see it from the back. And when the signs weren’t reflective yet, the octagonal shape prevented drivers from confusing the stop sign with any other at night.

Water is great at cleaning stuff because it has triangular molecules. They’re made of one oxygen and two hydrogen atoms. Um, H2O? Such molecules have slightly different charges on their opposite sides — pretty much like magnets. That’s why water easily sticks to other molecules, including those that makeup dirt!

Glass breaks so easily because its atoms are arranged rather loosely and randomly. They can’t rearrange themselves fast enough to maintain the glass’ structure. As a result, glass doesn’t bend; it shatters.

Earth doesn’t get closer to the Sun in the summer. In reality, it’s closest to it in January and farthest in July. It’s warmer in the summer because Earth’s axis is tilted. It lets the planet’s northern part catch more sunlight for half of the year and the southern part — for the other half.

You can always squeeze in some dessert, no matter how much salad, soup, or meat you’ve eaten before. Your body gets bored of savory tastes. But when you see and smell something sweet, like ice cream, cakes, or chocolate, your brain gets excited. It overrides all fullness signals for pleasure. Plus, your stomach is a flexible organ, and sugar helps it relax and physically make room for dessert. I can use that information.

The first solar calculator hit the shelves in the late 1970s. That’s when scientists began experimenting with relatively cheap solar cells. Calculators were among the first products that needed little power to work. Later, this technology moved to larger stuff, such as lights and highway signs.

Light isn’t the fastest thing in the world. Of course, nothing can compare to its speed in a vacuum. But it slows down while going through water or glass.

Oranges (the fruit, not the traffic cone) aren’t always orange. The green-skinned variety is just as sweet and ripe. This unusual skin color protects oranges from the Sun. It’s also a sign there’s plenty of chlorophyll in the fruit. That’s why green oranges mostly grow in warmer climates.

A shadow is cast when you have an object in the path of light. Light travels in a straight line, which is why you always get a shadow when something’s in front of a light source. Birds and airplanes are no exception. They DO cast shadows, but you can’t see them. The closer the object is to a source of light, the denser its shadow is. And if the object is too far away, its shadow disperses.