Science questions for children: What is the darkest thing in the world?

What is the darkest thing in the world? Is there anything darker than black?

Veikko Holopainen, 9

Darkness and blackness are slightly different things.

Darkness means the absence of light. You can get to a completely dark space in a very simple way.

For example, it is completely dark in a completely light-tight closed room or in a sufficiently insulated cave. If no light enters the space, our eyes can’t see anything at all.

Black, on the other hand, refers to the surface of an object or other object that absorbs, or as if absorbs, the light falling on it.

In this case, our eyes see the object as black. However, ordinary black objects do not completely absorb all light, but reflect a few percent of the light back.

This can be seen, for example, in the fact that a black object can shine or change its tone when viewed from different directions.

Recently, super black coatings have been developed, i.e. substances added on top of objects that reflect only hundredths of a percent of the light hitting them.

The most famous of them is probably the coating called Vantablack, which can be produced on an aluminum surface. In its manufacture, nanotechnology is used, with which it is possible to build new properties into very small structures.

The super black surface looks confusing. It seems as if it is an opening into a completely dark space, because there are no reflections or changes in tone.

The blackest of all, however, are the black holes in space. Their surface eats up all the light and matter that hits them. However, we have not been able to examine them closely enough to see the feature in question directly.

Kari Rummukainen

professor of theoretical particle physics

University of Helsinki

Why don’t birds have eyelashes?

Tauno Dodd, 6

With little birds such as, for example, titmice, sparrowhawks and ovenbirds have no eyelashes at all.

However, some of the world’s birds, such as the ostrich, emu, nandu, African secretary bird and hornbill, have very long and curly, downright Hollywood-type eyelashes.

The long and curly eyelashes are probably related to the evolutionary history and habitat of these birds. For example, ostriches are flightless species of dusty plains, the African secretary bird spends most of its time on the ground, and hornbills build their nest holes with clay, so they all benefit from large eyelashes that protect the eyes.

If you look closely at the close-up photos of, for example, harriers, you can see their soft eyelashes too. But when the eyes are really small, as in small birds, the covering of hair or feathers around the eyes already serves as protection for the eyes. That probably explains the lack of eyelashes.

However, many eyelashless birds have a ring of tiny tuft-like feathers on their lids or right around the eye, which probably prevent small debris such as dust rising from the feathers from entering the eye.

The function of the eyelashes is not only to act as a protection against debris, but also to trigger an automatic blinking reaction, or -reflex, when something touches them. Very thin, almost invisible eyelashes are enough to create that reflex.

Even if eyelashes are missing, most birds have socks, or stiff feathers, at the base of the beak right in front of the eyes, which sense a touch or touch coming from the front, for example when flying or eating, which triggers blinking.

That way of protecting the eyes, which has developed over time, may have contributed to the fact that most birds lack larger eyelashes.

Also, mammals only have strong eyelashes in large species, such as camels, cattle, horses and primates such as chimpanzees and gorillas.

That Hohtola

Emeritus Professor of Animal Physiology

University of Oulu

Can bacteria and viruses become diseases?

Jalo Rantanen, 12

With bacteria and viruses do not have the same diseases as humans or other animals. However, there are many threats in their lives that can make them feel bad.

For example, scarce food makes bacteria unwell, and without water most of them die. Bacteria can also damage each other when fighting for living space with toxins called bacteriocins.

Bacteria can also get infections caused by bacteriophage viruses, which kill the bacteria after they have first multiplied inside the bacteria.

We ourselves can also destroy our own good bacteria by eating unhealthily and our disease-causing bacteria by using antibiotic drugs.

Viruses are not well and cannot live at all unless they get inside the cell of a living organism. Antibodies produced by the body of a person or other organism, which help to heal from diseases, also lead to the death of the virus.

However, what could be most reminiscent of viral diseases are the gene mutations that happen to them from time to time, i.e. random changes in the genome. Gene mutations make them sick and take away the edge of causing disease until a new viable virus variant is born.

Washing with soap and using hand sanitizer is an effective way to make it difficult for viruses and bacteria to flourish. They take with them the surface structures that protect viruses, in which case they have no conditions to live. Hand sanitizer also destroys the surface structures of bacteria, and hand washing washes bacteria away.

Pentti Huovinen

professor emeritus of bacteriology

University of Turku

How far can a snail travel in its lifetime when it moves so slowly?

Jussi Ihatsu, 6

Snails moving is really very slow because they have no limbs. They move by wave-like contraction of the muscles of their probes, i.e. the part that is against the ground. The antura secretes mucus underneath, which makes it slippery, making it easier to walk.

Snails are on the move especially in summer and autumn at night or in the rain, because then they are not in danger of drying out. The distance traveled can be estimated the next day from the dried slime sticks they leave behind.

Large snails can move more than 10 meters during a humid summer night. Smaller individuals less.

If the snail has food and there are no other snails in the same place to crowd it, it has no need to go on adventures far. Nocturnal excursions can often extend only a few meters away.

In dry weather, snails do not move at all, and in winter they burrow into the surface of the ground under the shelter of leaf litter to hibernate. The snow cover is also a good thermal insulator for them.

The life of snails is usually not long, only two to three years. If you add up the distances traveled during their life, they usually add up to no more than a kilometer or two. Even for that distance, they usually turn and meander in an area the size of the plot of a single-family house.

Haimi’s finger

retired university lecturer

University of Jyväskylä

Send the question, the questioner’s full name and age to lasten.tiedeskö[email protected]. The column is provided by Touko Kauppinen.