The basic idea behind a dark star only requires knowledge of 18th century physics. If a star is dense enough, its escape velocity will be the speed of light, making it impossible for light emitted by the star to escape the stars gravity.
충분히 밀집되다면 탈출속도가 빛속도가 되어 빛조차도 빠져나오지 못하여 '검은 별'의 이론은 18세기 물리학 만으로도 설명될 수 있었다.
The idea of a dark star, as proposed by John Michell is not correct, but it is still important since it introduces some ideas that apply to black holes even in modern theories. The problem is, that the concept of a dark star uses Newton's older theory of gravity instead of Einstein's newer theory. It was good enough for us to plan a mission to the moon, for instance. When I mean by weak is this, calculate the escape velocity from a planet or star, and compare the value of its escape velocity to the speed of light. If the escape velocity is tiny compared to the speed of light, then we say that gravity is weak, and Newton's theory of gravity is a good enough approximation.
존 미첼의 검은별 이론이 정확하진 않지만 현대 물리학의 블랙홀에 적용할 이론을 제시했다는데 큰의미가 있다. 검은별 이론이 현대의 아인슈타인의 상대론이 아닌 뉴튼 역학에 기반했기 때문이다. 검은별 이론이 완전히 틀리지 않은 이유는 아인슈타인의 중력이론에서 낮은 질량과 빛보다 매우 느린 속도로 근사하면 뉴튼 역학이 유효하기 때문이다.
For example, the escape velocity from the Earth is 11.2 kilometers per second, but the speed of light is approximately 27,000 times larger. Since the escape velocity from Earth is so small compared to the speed of light, Newton's gravity is good enough for most calculations near the surface of the Earth. But if the escape velocity is larger, say 10 percent of the speed of light or larger, that means that Newton's theory of gravity is no longer sufficient to calculate the strength of gravity. Since Albert Einstein's equations correctly describe relativistic effects at high speeds, they improved on Newton's theory of gravity.
예를 들어 지구표면에서 탈출 속도는 11.2 초당 킬로미터로 빛의 속도에 비하면 2만 7천분의 1밖에 되지않다. 뉴튼 역학으로 기술해도 충분하다 [일상적으로 충분하다는 뜻이다. 지구 탈출속도보다 작은 속도의 GPS 정지궤도 위성만 해도 정밀한 시간계산을 위해 상대론적 보정이 필요하다.] 만일 탈출속도가 빛 속도의 10%만 되었더라도 뉴튼의 인력 법칙으로 유효한 중력 계산을 할 수 없다. 고속에서 상대론적 효과를 기술한 앨버트 아인슈타인 방정식은 뉴튼의 중력이론을 보완한 것이다. [탈출속도는 지구의 질량과 중심으로부터 거리에 의해 계산되었다.]
This means that we can predict what happens in situations with strong gravity. Einstein's theory of gravity is called The Theory of General Relativity. In general relativity, mass, energy, and angular momentum are all responsible for creating curvature in space time. The curvature of space time then causes planets, stars, and light to travel on curved paths.
아주 강력한 중력이 작용하는 상황을 생각해 볼 수 있다. 아인슈타인의 중력에 관한 이론을 "특수 상대론"이라 하는데 강력한 중력에 의해 질량,에너지,각운동량이 왜곡된(굽은) 시공간으로 평가 된다는 것이다. 그리하여 행성,별 심지어 빛 조차도 굽은 경로로 움직인다.
To create a dark star, we might start with a large star and compress it inwards to make it smaller and denser while keeping the amount of mass unchanged. As the star shrinks in size, the escape velocity from the surface becomes faster and faster until it becomes equal to the speed of light. At this point, Newton's theory of gravity just predicts that light won't be able to escape from the star, and it will appear dark.
검은별은 질량을 유지한 채 크기(반경)을 극단적으로 줄여 가서 표면에서 탈출속도가 빛의 속도와 같아지면 빛이 빠져나가지 못하게 된다는 이론이다. 이는 뉴튼의 중력 법칙에도 부합한다.
However, the predictions from Einstein's theory of gravity demonstrate a so called dark star, would exert a much stronger force due to gravity than predicted by Newton. This additional inwards gravitational force makes it impossible for a star to have a stable size. In order for stars to exist, there is a delicate balance between its gas molecules, which exert a net outwards pressure that is exactly balanced by the attraction of gravity, allowing stars to stay the same size over time. When a star gets so small, that its escape velocity is the speed of light, then the required outward gas pressure is infinite. There is no way to create infinite gas pressure, so the star is unstable and begins collapsing inwards.
하지만 아인슈타인의 중력 이론을 검은 별에 적용 시키면 뉴튼역학에서 예상한 것보다 더 많은 힘이 필요하다는 것이다. 중력에 더해 이 수축하는 힘이 가해지면 별은 안정된 모습을 갖지 못한다. 별이 존재하기 위해 수축하는 힘과 가스 분자 사이에 정교한 균형을 이뤄야별은 지속적으로 모습을 유지할 수 있다. 별이 점점작아져 탈출 속도가 빛의 속도에 다다르면 가스 압력은 무한 대에 가까워야한다. 하지만 무한의 가스압을 내기는 불가능하므로 별은 유지하지 못하고 수축한다.
A black hole is what remains after a star is unable to resist gravity and collapses inwards. A black hole does not have a surface but there is a special boundary that surrounds a black hole called an event horizon. In the case of the simplest black hole, the event horizon is a sphere with a radius called the Schwarzschild radius with the value, event horizon radius equals 2 times G, times the mass of the black hole, divided by the speed of light squared. The amazing thing about the formula for the event horizon radius is that it is exactly the same equation that Michell derive for the radius of a dark star.
블랙홀은 중력을 견디지 못하고 수축하므로서 생겨난다. (무한 축소된) 블랙홀은 표면을 갖지 못하는 대신 탈출 속도가 빛의 속도와 같은 특별한 구면을 형성하게 되는데 이를 사건의 지평선 (Event Horizon)이라고 한다. 사건의 지평선의 반경은 간단하게 구할수 있다. 이를 슈발츠쉴드 반경이라 한다. 블랙홀 사건의 지평선 반경은 놀랍게도 미첼이 유도한 검은별 반경과 일치한다.
The event horizon radius is a boundary for light rays. If an astronaut shines a flashlight outside of the event horizon, the light rays can escape and be seen by astronomers far away from the black hole. But if the flashlight is at or inside of the event horizon, all light emitted will be trapped inside of a black hole. And it's not just light, massive objects like cakes, or rockets, or astronauts, can escape as long as they are outside of the event horizon radius and their rocket is good enough. But if a cake eating astronaut crosses the boundary defined by black holes event horizon, no escape is possible.
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The name black hole didn't enter a common usage until 1967, where it was popularized by John Wheeler. Before then, astronomers used the name Totally Gravitationally Collapsed Objects to describe black holes. This is an accurate phrase, but difficult to say. So it's not surprising that the name black hole caught on so quickly with scientists and science fiction writers alike.
1967년에 존 윌러에 의해 블랙홀이라고 불리게 되기 전까지 잘 알려지지 않았다. 원래 이름은 "전적으로 중력에 의해 수축된 천체"이었다. 정확한 표현이지만 부르기에 너무 길었다. 블랙홀이 과학자들과 공상과학 작가들에 의해 쉽게 받아들여진 것도 무리는 아니다.
The distinguishing difference between Michell's dark stars and black holes, as they are described in general relativity, is whether or not the star within the dark boundary maintains a surface. Michell didn't consider what would happen to the surfaces of a star when its escape velocity reaches the speed of light. Scientists now believe that the creation of an event horizon causes all the material hidden behind it to continue collapsing inwards with no chance of a stable surface.
미첼의 검은별과 일반 상대론으로 설명되는 블랙홀을 단적으로 보여주는 차이는 표면의 유무다. 미첼은 탈출속도가 빛의 속도와 같은 표면이 존재하는 별을 생각했지만 현대 과학자들은 사건의 지평선 안 쪽으로 계속 (무한히) 축퇘 되어 안정된 표면이 없다고 생각한다. [질량을 갖지만 무한히 작은 특별한 점. 밀도가 무한대인 점]
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[암흑 성운/Dark Nebula]
There are other dark objects that astronomers make reference to, but they aren't black holes. For instance, there are dark nebula which consist of clouds of cool molecules and dust that block out passing light. These types of nebula can be observed if they lie between us and a bright source of light, since we will see that sunlight is blocked out by the nebula. One famous example is the horsehead nebula. The Horsehead is a dense, cool cloud that blocks out the red light that is emitted behind it, allowing us to see it. In addition, dust emits infrared light so we can detect dust clouds if we use an infrared telescope.
검다고 다 블랙홀은 아니다. 밀집된 우주 먼지에 의해 배경 빛이 가려지는 경우 '암흑성운(Dark Nebula)'라 한다. 말목성운(Horsehead Nebula)가 유명하다.
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[암흑 물질/Dark Matter]
Dark Matter is a hypothesized type of matter that was introduced to explain the motions of stars and gas and galaxies. Dark Matter is a type of matter that doesn't emit light, which means it can't be observed directly. However, dark matter does have mass, so there is a mutual gravitational attraction between dark matter, and the stars, and gas, in the galaxy. The gravitational attraction of the dark matter affects how the stars in the galaxy move, allowing scientists to infer the existence of dark matter by their observations with theoretical models. In the 1970s, Vera Rubin, observed spiral galaxies and measured the speeds of the stars. She showed that the fast speeds of these stars implies the existence of dark matter.
'암흑물질(Dark Matter)'은 아직 실체가 밝혀지진 않았다. 1970년 베라 류빈(Vera Rubin)에의해 은하의 회전 속도를 측정하다 그 존재가 알려졌다. 은하의 외곽에 위치한 별들의 은하공전 속도가 계산보다 빠른것으로 밝혀졌다. 어떤 알수없는 질량을 가진 물질이 존재하기 때문인 것으로 추정된다. 암흑물질은 매우 광범위 하게 분포되어 있다고 여겨진다.
A tiny amount of the dark matter could be black holes but most of the Dark Matter is a type of particle called a WIMP, which means weakly interacting massive particle. Physicists are trying to detect WIMPs using the Large Hadron Collider in Geneva, Switzerland, and SNOLAB in Sudbury, Canada, as well as other laboratories. So far, the dark matter WIMPs have not been detected.
소량의 암흑물질이 블랙홀이 될 수도 있으나 대부분 WIMP(약하게 상호작용하는 중량 입자: 큰 질량을 가짐에도 상호작용[인력]은 아주 작은 입자)로 존재한다. 물리학자들이 WIMP를 검출하기 위해 여러 실험을 했으나 성공하지 못했다. 스위스 제네바의 강입자 충돌기(LHC), 캐나다 써드베리의 SNOLAB 등.
The main thing that dark matter and black holes have in common is that they are both detected by observing their gravitational interactions with luminous objects.
암흑물질과 블랙홀이 광범위하게 분포한다는 주된 증거는 암흑물질이 밝은천체와 상호 중력작용을 하고 있다는 것이 관측되기 때문이다. [나선은하의 별들의 은하 공전속도가 별의 관측 무게보다 훨씬 빠르다]
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[암흑 에너지/Dark energy]
Dark energy is the name for another mysterious force which appears to act in opposition to the force of gravity. When astronomers measure galaxies far, far away, they measure that the most distant galaxies appear to move away from us more quickly than galaxies that are close. This is one of the pieces of evidence that our universe is expanding from a moment in history referred to as The Big Bang. Since all these galaxies have mass, they are gravitationally attracted to each other, and we might expect that the rate of the universe's expansion should slow down over time. Instead, there is evidence that the expansion is speeding up, as if there were a repulsive force like a very large scale kind of anti-gravity. This force called dark energy has nothing to do with black holes.
'암흑 에너지'는 미지의 힘에서 지어진 이름이다. 멀리 있는 은하 일수록 더빠르게 멀어지는 것으로 관측되고 있다. 즉, 우주는 빅뱅이후 가속 팽창 중이다. 어떤 힘이 거대한 우주를 이렇게 가속 팽창시키는 것일까? 이 알수 없는 에너지를 암흑 에너지라고 정의했다.
[암흑물질과 암흑 에너지는 검다고 지어진 이름이 아니다. 알수 없어서 암흑이라고 지어진 이름이다.]
However, there are some theorist who have considered types of stars that have some dark energy in them to help combat gravitational collapse. Black holes may give some people melanoheliophobia, but in most ways, they are no more dangerous than any other star in the sky. For example, entering into a black hole is dangerous, once you pass through the event horizon, you can't get out. But if you enter into a star, the hot gas would burn you up too. I would say they are both equally dangerous.
There are safe ways to visit a star or a black hole. Instead of traveling directly towards a black hole, you could instead, orbit the black hole just as you can orbit around a star. For example, the Earth orbits around the Sun in a safe stable orbit. Similarly, the Earth could orbit a black hole with the same mass as the sun and at the same distance, making the orbit just as safe and stable as it is now. Unfortunately, it would be very cold around a black hole since the sunlight that warms us would no longer be present. There is nothing about the black hole's gravity that would suck in the Earth.
암흑 에너지가 블랙홀의 중력 붕괴를 막고 있다고 생각하는 이론가들도 있다. 블랙홀에 빨려들어 갈까봐 공포증을 가진 사람도 잇다고한다. 멜라노 헬리오 포비아(melanoheliophobia). 물론 블랙홀로 빨려 들어갈 반경안으로 가면 위험 하지만 무조건 빨려 들어가는 것은 아니다. 공전 궤도에 있으면 무사하다.
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Black holes can become dangerous if they are surrounded by an orbiting disc of hot gas, that looks similar to the rings of Saturn. The disc of gas could emit high energy X-rays. So if you were to approach the black hole's disc, you could receive an unhealthy dose of radiation. For this reason, in the movie Interstellar, the script writers decided to make the disc of gas orbiting their black hole be relatively cool, so that it only emits visible light and no harmful X-rays.
블랙홀이 위험한 것은 빨려들어가는 것보다 동반성을 가지고 있거나 고 에너지 원반을 가지고 있기 때문이다. 블랙홀 근처에 가면 타죽거나 강한 방사선에 쪼여 죽는다.
The tidal force, which is a difference in the strength of gravity at different locations, can become very strong around a black hole. In fact, when it comes to the tidal force, the smaller a black hole is, the more dangerous it becomes. An astronaut venturing too close to a small black hole would be stretched by gravity into long thin spaghetti-like strands.
조석력 또한 무시 못할 위험이다. 작은 블랙홀(동반성이나 고에너지 원반이 없는)은 조석력의 위협이 더크다. 작은 블랙홀의 중력은 사람의 신장 차이 정도의 거리차에도 크게 작용한다. 발끝에서 머리까지 작용하는 중력차로 인해 접근하는 우주인은 쭉 늘어나는 수가 있다. [사지가 찢어진다... 무섭!]
Out of all the types of black holes, the most dangerous are thought to be the isolated black holes. In isolation, a black hole does not have a companion star or an orbiting disc of gas, making them extremely difficult to see. Due to their difficulty of detection, it's possible that you could accidentally stumble across one, and inadvertently cross into its event horizon while you are exploring the universe. Gravitational lensing by the black hole's mass will distort the images of background stars. So, the presence of an isolated black hole could still be deduced, if you are careful.
관측하기는 어려운(불가능한) 블랙홀은 중력 렌즈 현상으로 그 존재가 확인된다.
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