What is better for nature: to buy a living Christmas tree or artificial?
This is a very complex question, which we will try to answer as simply as possible, based on the “carbon footprint” that a living and artificial tree leaves, that is, the amount of greenhouse gases emitted during the product’s life cycle. According to estimates made by Carbon Trust experts, a two-meter-long live tree leaves the equivalent of 16 kg of carbon dioxide if thrown away after use, and only 3.5 kg if burned. Decay causes methane production, which creates a much stronger greenhouse effect than carbon dioxide itself. According to the same data, a two-meter artificial Christmas tree leaves a “carbon footprint” of 40 kg of CO 2
. So if you choose this option, try to use this tree longer. Why do people hiccup?
Not only people hiccup: these convulsive spasms of the diaphragm from time to time torment all mammals and many other animals using pulmonary respiration. Short and strong movements create sharp breaths that break off with a sudden blockage of the airways, creating a characteristic hiccup sound. This involuntary reaction is thought to help remove air from the stomach. But it can also be the result of accidental irritation of the vagus nerve, which passes through the same opening of the diaphragm as the esophagus. Therefore, hiccups can cause too hasty absorption of food. There is a hypothesis that hiccups are a relic left to us from dizzying times. In any case, amphibians breathe due to very similar spasms that allow them to wash their gills. Can I catch a cold from my dog?
It is unlikely that most cases of acute respiratory viral infections occur due to rhinoviruses, which, as a rule, specialize in infection of a certain type. Animals have their own colds, we have their own. On the other hand, the flu virus is more flexible, and cases of transmission of “swine” or “bird” flu to humans are rare, but widely known. But bacteria - pathogens are much more versatile, and strep-causing streptococci or tubercle bacilli can infect your dog and become infected from it. Is it possible to damage a person by pointing a thousand laser pointers at him?
The laser in the pointer can damage vision, but the skin is not felt. Typically, these are systems with a capacity of less than 5 mW, according to GOST, they should be marked with warning labels, but their sales are not limited. If you came up with the idea to destroy the enemy with laser pointers, then hundreds will not be enough. A physicist at the University of Texas, Rebecca Thompson, calculated: in order for a ray that gets into the eye to penetrate and damage the brain, it will require at least 1 kW of power, which means it will need at least 200, 000 pointers focused at one point. Theoretically, they can be placed on a large parabolic "plate", concentrating radiation on the victim. What cells of the body do not have DNA?
Initially, there is DNA in all our cells, but in the adult stages of life, some of them lose the nucleus and the chromosomes it contains. Thus, keratinized keratinocytes of the upper layers of the skin end their lives without a nucleus and basic organelles. There is no nucleus for platelets - pieces of cytoplasm that have separated from megakaryocyte cells. The most famous example is oxygen-carrying red blood cells, which, due to this, sharply decrease in size and can move through thin capillaries. Mature erythrocytes do not even have mitochondria that could contain extra nuclear DNA.
What mode do astronauts on the ISS live in? Sunrises and sunsets on the ISS occur every hour and a half. The sun can no longer set a comfortable rhythm of sleep and wakefulness. But astronauts observe the same familiar cyclical pattern. 24 hours are divided into 6.5 hours of working time, 2.5 hours of training on simulators, an hour for lunch, the rest is rest and sleep. Usually the rise is announced at 6:00, work starts at 8:00 and ends at 19:00, hang up at 21:30. Time is calculated in GMT, that is, four hours behind Moscow. Why is Pluto not a planet?
Almost half a century after the first observation of Pluto, its size remained exactly unknown. Only in 1978, when the Charon satellite was discovered, it was possible to determine the mass, and then the diameter of Pluto, which amounted to only 2, 370 km. For comparison, the diameter of the moon is 3475 km. In the Kuiper belt, where Pluto is located, there are many bodies of comparable size, and Eris is even heavier. The discovery of Eris in 2005 was the last straw: it was necessary either to rank among the planets and her, and dozens of bodies similar to Pluto, or to exclude Pluto itself from their number. The decision was made in 2006: the planet of the solar system is now considered to be a body that revolves around the sun, is not a satellite of one of the planets, massive enough to take a rounded shape and clear the vicinity of its orbit. Pluto, as well as Eris, Ceres, and many others do not satisfy the third condition and do not reach full-fledged planets.The article "Questions and Answers" was published in the journal "Popular Mechanics" (No. 12, December 2016).