Often the subject of science fiction novels, black holes are mysterious objects that, while very real, have a certain mythology that surrounds them. Some of these myths actually arise out of scientific truth, while others are the result of wild imagination. So what is fact and what is fiction? And where do black holes come from anyway?
What Is a Black Hole?
Simply put, a black hole is a region of space that is so incredibly dense that not even light can escape from the surface. However, it is this fact that often leads to miss-understanding. Black holes, strictly speaking, don't have any greater gravitational reach than any other star of the same mass. If our Sun suddenly became a black hole of the same mass the rest of the objects, including Earth, would be unaffected gravitationally. The Earth would remain in its current orbit, as would the rest of the planets. (Of course other things would be affected, such as the amount of light and heat that Earth received. So we would still be in trouble, but we wouldn't get sucked into the black hole.)
There is a region of space surrounding the black hole from where light can not escape, hence the name. The boundary of this region is known as the event horizon, and it is defined as the point where the escape velocity from the gravitational field is equal to the speed of light. The calculation of the radial distance to this boundary can become quite complicated when the black hole is rotating and/or is charged.
For the simplest case (a non-rotating, charge neutral black hole), the entire mass of the black hole would be contained within the event horizon (a necessary requirement for all black holes). The event horizon radius (Rs) would then be defined as Rs = 2GM/c2.
How Do Black Holes Form?
This is actually somewhat of a complex question, namely because there are different types of black holes. The most common type of black holes are known as stellar mass black holes as they are roughly up to a few times the mass of our Sun. These types of black holes are formed when large main sequence stars (10 - 15 times the mass of our Sun) run out of nuclear fuel in their cores. The result is a massive supernova explosion, leaving a black hole core behind where the star once existed.
The two other types of black holes are supermassive black holes -- black holes with masses millions or billions times the mass of the Sun -- and micro black holes -- black holes with extremely small masses, perhaps as small as 20 micrograms. In both cases the mechanisms for their creation is not entirely clear. Micro black holes exist in theory, but have not been directly detected. While supermassive black holes are found to exist in the cores of most galaxies.
While it is possible that supermassive black holes result from the merger of smaller, stellar mass black holes and other matter, it is possible that they form from the collapse of a single, extremely high mass star. However, no such star has ever been observed.
Meanwhile, micro black holes would be created during the collision of two very high energy particles. It is thought that this happens continuously in the upper atmosphere of Earth, and is likely to happen in particle physics experiments such as CERN. But no need to worry, we are not in danger.
How Do We Know Black Holes Exist If We Can't "See" Them?
Since light can not escape from the region around a black hole bound by the event horizon, it is not possible to directly "see" a black hole. However, it is possible to observe these objects by their effect on their surroundings.
Black holes that are near other objects will have a gravitational effect on them. Going back to the earlier example, suppose that our Sun became a black hole of one solar mass. An alien observer somewhere else in the galaxy studying our solar system would see the planets, comets and asteroids orbiting a central point. They would deduce that the planets and other objects were bound in their orbits by a one solar mass object. Since they would see no such star, the object would correctly be identified as a black hole.
Another way that we observe black holes is by utilizing another property of black holes, specifically that they, like all massive objects, will cause light to bend -- due to the intense gravity -- as it passes by. As stars behind the black hole move relative to it, the light emitted by them will appear distorted, or the stars will appear to move in an unusual way. From this information the position and mass of the black hole can be determined.
There is another type of black hole system, known as a microquasar. These dynamic objects consist of a stellar mass black hole in a binary system with another star, usually a large main sequence star. Due to the immense gravity of the black hole, matter from the companion star is funneled off onto a disk surrounding the black hole. This material then heats up as it begins to fall into the black hole through a process called accretion. The result is the creation of X-rays that we can detect using telescopes orbiting the Earth.
Hawking Radiation
The final way that we could possibly detect a black hole is through a mechanism known as Hawking radiation. Named for the famed theoretical physicist and cosmologist Stephen Hawking, Hawking radiation is a consequence of thermodynamics that requires that energy escape from a black hole.
The basic (perhaps oversimplified) idea is that, due to natural interactions and fluctuations in the vacuum (the very fabric of space time if you will), matter will be created in the form of an electron and anti-electron (called a positron). When this occurs near the event horizon, one particle will be ejected away from the black hole, while the other will fall into the gravitational well.
To an observer, all that is "seen" is a particle being emitted from the black hole. The particle would be seen as having positive energy. Meaning, by symmetry, that the particle that fell into the black hole would have negative energy. The result is that as a black hole ages it looses energy, and therefore loses mass (by Einstein's famous equation, E=Mc2).
Ultimately, it is found that black holes will eventually completely decay unless more mass is accreted. And it is this same phenomenon that is responsible for the short lifetimes expected by micro black holes.
Sunday, 11 July 2010
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What are black holes?
ReplyDeleteThere is no such thing as black holes! There is only misunderstanding about how stars and their systems move in space. When scientists finally understand how our own planet moves around the sun in a downward spiral orbit while our sun moves down through space in a shallow orbit; then they will begin to understand the relative motion of the other star systems, which are moving toward us and away from us and in all directions. When we learn how particles move through space, which includes the sun and its orbiting planets, we will then, understand much more about this machine we call the universe.
Particles in space are always moving in a spiral orbit moving from low pressure to high and then back again. However, this pressure exists not just from the outside pushing in but also from the inside pushing out. Understanding these pressures and how they work is the heart of “other dimensional science.” Understanding how these star systems move through space, will also accurately answer the questions of red giants and white dwarfs, as well as…the death and birth of stars, which do not exist.
It is true that stars get bigger and smaller as they orbit from one pressure zone to another and consequently, they do change color as a result, but stars do not nova and then disappear. I would love to view a star nova through a powerful telescope, a star nova is a spectacular thing to see but when it’s all over with, that star is still there, we just can’t see it any longer because it has moved from one pressure spectrum to another!
Currently, the earth is orbiting down from low pressure into high pressure. It takes 12,000 years to complete this quarter cycle before we enter, into the next cycle, which will take us once again… from relative low pressure to high, and we begin another 12,000 year cycle.
The earth and the machinery which surrounds it, work a lot like a washing machine or any machine, for that matter. When you have working parts, the parts of the machine get hot in certain places and so the machine changes gears. It all works like a clock in a way. Pressure builds up and finally moves the minute hand into the next position. This explains the motion of the poles which are shifting, the rising of water, which result in major floods and often permanent water displacement, volcanoes, earth quakes, hot and cold cycles, etc.…
There comes a point where we reach the end of a cycle when the earth is at the maximum internal pressure which exists at the quantum level of space, and it must let that pressure go. It reacts much like a spring that has been wound so tight that it finally let’s go. When this happens… particles, which are attached to one another in long chains, expand rapidly, which causes everything on the earth to expand just a bit; the greatest effect is in the waters of the earth.
Now, the sun is also under great pressure and when we reach the end of a cycle, the sun which has been compressed changing colors as it goes through the different pressure spectrums, expands rapidly. This effect, like the water of the earth, affects the sun in the same manner because of its molten nature. The visual effect is much more spectacular when the sun once again, regains homeostasis. However, we do not see it as it has passed into the next cycle hidden by a blanket of electrons. These huge electron conduits, separate one macro particle structure from another.
Scientists will learn and understand this in the next few years as they continue to put particles under extreme pressure in the laboratory but will understand much more when they discover how to get a frequency signal inside of an electron conduit. When they can overcome the pressure of what I call E. Space and get a frequency signal inside, they will then be able to map the structure of an atomic particle which works exactly the same way as our solar system. Eventually, they will also understand “other dimensional particles” and how they fit into the machine and why.
There is no such thing as black holes! There is only
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