Category Archives: Common

Why there is a boy and no girl on pedestrian traffic lights?

This is an interesting question combining the history of crosswalks, pictograms and traffic lights.

It’s known that pedestrian cross-walks existed in Roman empire more than 2000 years ago. These were raised stone paths across the roads that doubled as severs.

Kuvahaun tulos: first pedestrian traffic lights
Info on first traffic lights

History of traffic lights starts in railways. First traffic lights in city centre were actually pedestrian lights installed in London 1868. Unfortunately the gas lamp caused an explosion which killed a policeman and the idea of traffic lights was forgotten for 50 years, until in 1914 in USA modern traffic lights were installed to help problems caused by high number of motor cars.

Third part of the answer is about the history of the “male and female” pictograms. these were invented in a museum in Vienna back in 1924 to help people who could not read the written text in signs. The modern toilet signs were included in the pictograms and since then people have associated these 2 stick figures to men and women.

Kuvahaun tulos: pedestrian traffic light
Berlin traffic light man

It’s not well known when they started using a stick figures in pedestrian traffic lights. Basically the figure is just a “person” without a gender, but the association from toilet signs leads us to think he is a man. Actually in East-Berlin they used symbols where the person had a hat to clearly indicate he is male.

As a response to that many cities have since then used permanent or temporary setup of custom traffic light persons, male, female, kids, couples etc.

Blood moon

What is blood moon?

Blood moon is a name of the moon during a full lunar eclipse. In a perfect lunar eclipse the moon will be completely covered by earth’s shadow. The moon still does not disappear completely from sight, but appears to be dark red. Red color is the reason for designation of blood moon”.


What is a week?

Time is usually divided into smaller parts to make it easier on various occasions to express and perceive the passage of time. For example. It is easier to say that the child is five years, than 438 000 hours old.

Some of the time units are based on celestial movements.

The year is the time in which the Earth goes around the sun once.
Month is a time in which the moon goes round the earth.
Day is the time where the earth rotates around itself.

In addition to these other entities has been developed, such as week and hour to make measuring time easier. Month has been split into four seven-day weeks and the days are divided into 24 hours.

Week is an old invention, but it has not always everywhere been 7 day long. In theBible, God created the world in seven days, but the idea is older.

One explanation is that the number seven came from the seven observed pieces of heaven. Names of days in certain languages ​​still point to celestial bodies.

Sunday is the day of the Sun
Saturday is Saturn’s day
Monday is the day of the Moon

Digestive system

Why do people poop?

Little green boy with shit
Little green boy with poop

Poop is waste. It is the part of the food that remains after all useful as nutrients are utilized. Food is a kind of human fuel” in the same way as gasoline in cars. Car exhaust pipe will exhaust gas and the human butt will poo.

While your body can not utilize poop substances, plants instead can. That is why, for example, a cow or a chicken poop is a good fertilizer and helps plants to grow well. The plants are then eaten and become poo again. This is how the natural life cycle works.


Why women do exist?

Many species can be divided into gender males and females or boys and girls.
To make children, normally both male and female are needed, but not always. For example, earthworms are both at the same time- male and female.
Nevertheless for humans to make offspring, both are needed: man and woman, dad and mommy.
Steamy Window

Where does the steam in window come from?

The air usually always contains some water vapor.

Water has three phases: liquid water, solid ice and water vapor. Under the 32-degrees water is usually in form of ice and in temperatures over 212 it turns into steam. Usually a window has warmer air on the indoors -side than on the outside. The outside air is making the window slightly cooler than the air inside. Therefore the water vapor in air is cooled down when it makes contact with the glass. When it cools, it turns back to liquid water and that forms the droplets you can sometimes see on steamy window.

The same phenomenon you can see in metallic cold water pipes. Pipes, “sweat”, because they are so cold that water vapor in the air will condense into water.

Also, human exhaled air is warm and humid. Therefore on cold weather breath turns into steam. You can also try to breath towards window or a mirror – it should generate some steam on it.


Where do carrots come from?

The carrot is a root vegetable growing in ground. The part that is growing above earth is normally not used for food, but the underground root is delicious and healthy snack. Rich in  betacarotene, which gives it an orange color. The carrot is after the potato one of the most popular root vegetables; it is eaten up to nine pounds per person per year.

Carrots are usually orange, but also white, purple, yellow and red carrots exists. In fairy tales and cartoons carrots are usually rabbits favorite food. Wild carrots do not exist everywhere, so in those areas rabbits need to eat some other plants.


Where does yoghurt come from?

A Cow

Yoghurt is milk that is acidified using lactic acid bacteria. Yoghurt production is close to those of butter and sour cream. Also cheese is made by similar method.  Before the start of the 1900s yoghurt was consumed especially in South-East Europe, Central Asia, the Middle East and India. 

You can try the yogurt preparation at home for instance, together with the mother or father.

You will need a pot of milk and a half pots of seed of natural yoghurt. The milk is boiled in a saucepan and then allowed to cool to below 122 degrees. After cooling, the milk is mixed with yogurt – you can add milk powder, if you want a thicker yogurt. The mixture is then placed in the bowl or glass jars and placed in a warm place for 4-7 hours. A good trick is to heat the oven to 122 degrees, and then turn it off and put the jars there.

Ready yogurt can be flavored with sugar and banana for example. Self-made yogurt will remain in the refrigerator for about a week (on the surface may be formed whey)

shopping bag

Why do plastic grocery bags exist?

Little Green Boy with bag in his head
Little Green Boy with bag in his head

This probably refers to a commercially available plastic bags. Shopping bag is usually used to carry the  groceries from shop to car and from car to home.

Plastic bags are made of plastic, and are most commonly used as carrier bags for groceries and as garbage bags. Plastic bags have all colors and sizes, and with different prints. They are thin, light and flexible. Extensive use of plastic bags spread in the mid-1970s. In 2002, the world was prepared in various sizes and qualities of plastic bags to a total of 4-5 trillion pieces

It is a good question why plastic bags are used. Plastic bags do not decompose and burning them causes toxic fumes. Thrown to the wild and in water Plastic bags cause problems for animals. Also biodegradable plastic bags do exist, but they are not as durable.

The same plastic bag can be used several times before it ends up as garbage bag.  Others prefer to use paper or fabric bags for carrying groceries. In some places, the use of plastic bags has imposed a special tax, or they are banned altogether.

In developing countries, little boys produce empty plastic bags, for example, soccer balls themselves.


Why do fingers exist?

Little Green Boy's hand
Little Green Boy’s hand

Try to keep the hand closed, and then try to pick up toys from the floor, or eat yogurt with a spoon. Fingers distinguish humans and other primates from most other animals, because they allow objects sticking. You can also try to pick up objects with toes – it is possible, but not very easy. The fingers have made it possible to use different tools.

Tools are an important stage in human development. Weapons let people to be able to hunt for food for others than himself. Some people may have to stay at home, and some have gone hunting. Later, the tools have made it possible to cut down trees, to cultivate the land, build houses, etc.

The most important finger is the thumb. The thumb moves against other fingers allowing fine mechanical thumb-index finger grip. Compared with the technological superiority of man is to relate to the brain and this grip. It is very rare in the animal kingdom: possum, koala and some primates are able to slightly similar.

You can try out the necessity of the thumb, say put, a glove in your hand so that your thumb is not in its separate compartment. Try then pick up objects in your hand.