Children ‘s science questions Why do boys develop more slowly than girls?

Elsa Viljanen, 10

In the early days in childhood, boys and girls grow well at the same rate, but in adolescence, girls develop earlier.

The first signs of puberty are seen in girls at an average age of 10 years and in boys at 11.5 years, but individual variation is large.

The pituitary gland at the end of the eye produces hormones that regulate puberty. In girls, the ovaries eventually produce the hormone estrogen, which causes external signs of pubertal development, mainly breast growth.

Estrogen also accelerates height growth in the very early stages of adolescence.

In boys, the testicles produce testosterone, some of which is converted to estrogen in the body, which in boys is also responsible for accelerating growth during adolescence. Testosterone is not converted to estrogen until middle age. Therefore, the growth spurt of boys comes to girls later.

Spiritual development is a more complex matter. Maturation of brain function has been studied in relatively small groups of people. Maturation is affected by genetic inheritance, conditions during fetal development, childhood hormones and environmental expectations.

According to some studies, hormones, especially during adolescence, can mature some of the brain connections in girls faster. In both girls and boys, brain development continues until the age of 25.

The exact reason for the different rate of development of the body in girls and boys is not known.

Liisa Viikari

pediatrician

Turku University Central Hospital

What happens to paper planes on the Moon if you throw it out of your hand?

5th grade of Herrala school, Ilmajoki

Paper plane would fly well in Moon as well.

On the ground, the flight of an airplane is affected by gravity and the interaction between the air and the airplane. There is no atmosphere in the Moon, so the plane would be affected only by gravity, which is only about one-sixth of the Earth’s gravity.

If the effect on Earth were not taken into account, the plane would therefore fly six times farther and six times longer in the Moon. Even if the plane were done really well and developed an excellent lifting force on Earth under its wings, it would still fly shorter than on the Moon.

Because in the Moon the plane would fall more slowly, its final velocity when colliding with the surface would be lower than on Earth. In the moon, the plane would fly much more evenly because the air resistance on Earth varies according to the direction of the air flow. Because the Moon’s gravity is so small and there is no air there, a rock would fly there much like an airplane.

Pasi Nurmi

astronomer researcher, coordinator

University of Turku Science Center

How many atoms need to be together for the human eye to be able to distinguish it?

Kalle Solin, 10

If the object under consideration is the thickness of the hair, i.e. about 0.05 millimeters in diameter, it can usually be distinguished from a close distance.

From the point of view of vision, the number of atoms in an object is not decisive. The number of atoms visible together would depend on what material the object would consist of and how dense it would be.

Diamond and graphite are both made up of carbon, but diamond is denser, so it can hold more atoms.

However, a tiny diamond would be almost transparent and therefore harder to distinguish.

The number of atoms can be estimated. If a spherical particle of 0.05 millimeters were very dense in material and contained, for example, air, it would hold about one thousand trillion to ten thousand trillion atoms. After one would be 15 or 16 zeros.

If a particle of the same size were completely hollow and consisted of a shell only the thickness of one atomic layer, it would have only about one hundred billion atoms, or one, and 11 zeros.

However, such a particle would not remain in the pile. One hundred billion atoms could be too little.

Simo Huotari

professor of physics

university of Helsinki

Whose foot was an example when you started using the foot as a measure?

Milla Latvanen, 12

Feet was used as a measure in many cultures thousands of years ago, before the beginning of time.

The body parts were the natural starting point for the units of length, for they were all always present. The elbow was the distance between the elbow and the head of the middle finger. The lap was the distance between the spread arms. The inch was the length of the thumb and the foot was the length of the foot.

As the lengths of body parts vary in humans, there was a need to harmonize dimensions. For a long time, however, the government of each kingdom set its own standards.

At least in ancient Greece, about 500 years before the beginning of time, the length of an adult man’s footwear was taken as the starting point for foot measurements.

The same line was extended during the Roman Empire from 753 BC to 1475 AD. At that time, the foot size varied around 30 centimeters according to the reign periods.

There is no more detailed information on whose size or persons was used as a starting point. The 30 cm long foot is quite large. It matches about the size of 47 shoes.

The foot and other Roman dimensions were used elsewhere in Europe. Gradually, dimensions again began to vary between countries and continents. It made it difficult to negotiate and trade.

In 1959, the United States and the Commonwealth countries defined an international yard-pound agreement as 30.48 centimeters in foot length.

The foot is still used as a measure in the United States, Britain and Northern Ireland, for example.

Johan Sten

researcher in the history of mathematical sciences

university of Helsinki

Why does coconut have such a hard shell?

Helka Vehkasalo, 6

Coconut palms can be as high as 10-story houses. The coconut weighs about half a kilogram.

Its skin must be very strong so that the fruit inside does not break when it falls from the palm. A broken palm could never grow a new palm. A broken seed would lose its ability to germinate.

Coconut palms grow wild near the equator on the shores of tropical seas. The plant spreads as the water transports the fruit to new growth sites. Here, too, a hard and tight shell is helpful. Salty seawater would impair the ability to germinate when it enters the fruit.

The shell of the coconut consists of the same substances as the wood material in general, i.e. cellulose, hemicellulose and lignin.

The shell is 4 to 6 millimeters thick, which is about the thickness of a child’s finger. For example, the peel of a babassu palm fruit is a thinner but stronger substance.

The outer part of the shell of the coconuts entering the market has been removed to be 3 to 4 centimeters thick, which provides additional protection. The skin as a whole has developed strong over a very long period of time, while the seed inside has developed into a large one.

Esa Tyystjärvi

Associate Professor of Plant Physiology and Biophysics

University of Turku

Send the question, the full name and age of the questioner to [email protected]. The column will be edited by Touko Kauppinen and Juha Merimaa.