냉동기를 만들었다.차가움을 얻기 위한 냉동과는 별개로, 과학자들은 ‘영원한 기체’(permanent gas)로 불리던 공기의 액화에 관심이 많았다. 이런 호기심은 ‘영원히 기체상태로 존재하는 기체가 과연 존재할까’하는 궁금증에서 시작됐다.물질은 일정한 압력에서 온도가 낮아질수록 기체에서 액체, ...
.The catch, even for turtles, is that water inside cells must remain mostly liquid, for large ice crystals will permanently damage cellular structure. Unlike mammals, turtles and other freezable animals have special biochemical reactions to protect against cellular damage of freezing. But only turtle hatchlings are protected; adults hibernate underwater where they won't freeze.While the ...
when conditions were radically different from what they are today.Hawking also showed that black holes are not permanent but slowly "evaporate." An ordinary black hole evaporates so slowly, however, that it would take a period of time that is trillions of trillions of years longer than the age of the universe so far to have it disappear.However, the evaporation rate would increase as the ...
stone had to be chipped or ground. Metals were harder and tougher than stone tools, less breakable, and held a more permanent edge.There was only one catch. Metals were far harder to find than rocks. The very word 'metal' is from the Greek word meaning 'to search for.'At first, only those metals could be used that could be found in free form -- gold, silver, copper and meteoric iron. When it ...
and economics permit the expense), we will be building a rather elaborate space station to serve as a base for a permanent settlemet on the Moon and for the building of a variety of structures in space, so that the true humanity-in-space age will begin.Closer to home, 1987 saw the excitement of comparatively high-temperature superconductivity. This remains a laboratory curiosity, because it is ...
fuel and would carry larger payloads.With space-station-as-base, it would be far easier to reach the moon and set up a permanent base there. The moon could then serve as a huge mine. Suitable chunks of the moon's surface can be fired into space by means of "mass-drivers" that use elec-tromagnetic forces for propulsion. This would be relatively easy on the moon, where the surface gravity is ...
of Earth. Eventually, it may well come to pass that space will be so full of debris that space flight through Earth's permanent ring of space garbage will become an increasingly hazardous undertaking.What are we going to do about this? We might try to cut down on number of satellites we launch, or take measures to prevent as many explosions and collisions as possbile― and certainly stop ...
and won't change in the foreseeable future. Nothing can substitute for the written word in some portable, more of less permanent form, that can be transferred from hand to hand. You may have heard it said that "A picture is worth a thousand words," but don't you believe it. It may be true on occasion - for someone who is illiterate, or when you are trying to describe the physical appearance ...
있는 것은 물론, 80년대에 들어오면서 자유근로시간제(flextime system) 영구적 파트타임제(permanent part-time system) 직무분담제(job sharing system) 집중적 근로제(compressed workweek system) 등 새로운 근로제도들이 확산되고 있다. 우리도 비능률적인 장시간 근무를 탈피, 상황에 맞는 제도를 찾아내야 할 때" 라고 ...
동아사이언스
디라이브러리
DS스토어
팝콘플래닛
