The eyes shout what the lips fear to say,” said William Henry. This is for the eyes betray innermost emotions like fear, apprehension, joy or sorrow, without having to express it in words. Moreover being the language of the heart, they do not lie and hence play an important role during personal interviews and interpersonal relationship. Besides this eyes are the window through which we view the word around us. Other primary sense, like touch, taste- and smell, are directly or indirectly dependent on sight. This is for the eyes in association with the brain, decipher the colour thereby evaluating the temperature of an object, even before it is touched. Similarly, it evaluates edibles, based on their colour, shape and size, even before the taste buds come into play. Thus it augments the other senses, making life pleasant and enjoyable.
Besides enhancing the other senses, it enables us to enjoy the beauty of nature so abundantly available all around us. It does this by storing visual images of the object in the form of memory tags in the brain. This enables us to recognize objects and is therefore essential for learning, which makes us recognise and distinguish other creatures in the universe.
The eye works like a camera, each part playing an important role in providing clear vision. The cornea behaves like a lens cover and is the main focusing element of the eye. The cornea takes widely diverging rays of light and bends them through the pupil, the dark, round opening in the centre of the coloured iris. The iris and the pupil are like the aperture of a camera behind which is the lens. The lens behaves like the lens of a camera. It focuses light to the back of the eye. The back of the eye is lined with a layer called the retina, which acts very much like the photographic film of a camera. It has photoreceptor nerve cells that line the inside back wall of the eye. The photoreceptor nerve cells of the retina, change the light rays into electrical impulses and send them through the optic nerve to the brain, where an image is formed. The centre of the retina is called the macula. This is responsible for sharp vision for reading. The peripheral retina is responsible for peripheral of vision.
Indeed eyes are the best gift of God. We are not aware of its importance, as long as our vision is perfect. Out of the five senses like sight, hearing, touch, taste and smell, the loss of sight is the worst one can ever suffer. It is because of this Helen Keller said, “Of all the senses sight must be the most delightful.”
The Tipler cylinder is a cylinder of dense matter and infinite length. Historically, Dutch mathematician Willem Jacob van Stockum (1910–1944) found Tipler cylinder solutions to Einstein’s equations of general relativity in 1924. Hungarian mathematician/physicist Cornel Lanczos (1893–1974) found similar Tipler cylinder solutions in 1936. Unfortunately, neither Stockum nor Lanczos made any observations that their solutions implied closed timelike curves (i.e., time travel to the past).
In 1974, American mathematical physicist/cosmologist Frank Tipler’s analysis of the above solutions uncovered that a massive cylinder of infinite length spinning at high speed around its long axis could enable time travel. Essentially, if you walk around the cylinder in a spiral path in one direction, you can move back in time, and if you walk in the opposite direction, you can move forward in time. This solution to Einstein’s equations of general relativity is known as the Tipler cylinder. The Tipler cylinder is not a practical time machine, since it needs to be infinitely long. Tipler suggests that a finite cylinder may accomplish the same effect if its speed of rotation increases significantly. However, the practicality of building a Tipler cylinder was discredited by Stephen Hawking, who provided a mathematical proof that according to general relativity it is impossible to build a time machine in any finite region that contains no exotic matter with negative energy. The Tipler cylinder does not involve any negative energy. Tipler’s original solution involved a cylinder of infinite length, which is easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, Hawking’s proof appears to rule this out. According to Hawking, “it can’t be done with positive energy density everywhere! I can prove that to build a finite time machine, you need negative energy.”
One caveat, Hawking’s proof appears in his 1992 paper on the “chronology protection conjecture,” which has come under serious criticism by numerous physicists. Their main objection to the Hawking’s conjecture is that he did not employ quantum gravity to make his case. On the other hand, Hawking and others have not been able to develop a widely accepted theory of quantum gravity. Hawking did just about the only thing he could do under the circumstances. He used Einstein’s formulation of gravity as found in the general theory of relativity. Another fact, Hawking’s proof regarding the Tipler cylinder is somewhat divorced from the main aspects of his paper and could be viewed to stand on its own. However, in science we are always judged by the weakest link in our theory. Thus, with a broad brush, the chronology protection conjecture has been discredited, and even Hawking has acknowledged some of its short comings.
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hi mate ,
The eyes shout what the lips fear to say,” said William Henry. This is for the eyes betray innermost emotions like fear, apprehension, joy or sorrow, without having to express it in words. Moreover being the language of the heart, they do not lie and hence play an important role during personal interviews and interpersonal relationship. Besides this eyes are the window through which we view the word around us. Other primary sense, like touch, taste- and smell, are directly or indirectly dependent on sight. This is for the eyes in association with the brain, decipher the colour thereby evaluating the temperature of an object, even before it is touched. Similarly, it evaluates edibles, based on their colour, shape and size, even before the taste buds come into play. Thus it augments the other senses, making life pleasant and enjoyable.
Besides enhancing the other senses, it enables us to enjoy the beauty of nature so abundantly available all around us. It does this by storing visual images of the object in the form of memory tags in the brain. This enables us to recognize objects and is therefore essential for learning, which makes us recognise and distinguish other creatures in the universe.
The eye works like a camera, each part playing an important role in providing clear vision. The cornea behaves like a lens cover and is the main focusing element of the eye. The cornea takes widely diverging rays of light and bends them through the pupil, the dark, round opening in the centre of the coloured iris. The iris and the pupil are like the aperture of a camera behind which is the lens. The lens behaves like the lens of a camera. It focuses light to the back of the eye. The back of the eye is lined with a layer called the retina, which acts very much like the photographic film of a camera. It has photoreceptor nerve cells that line the inside back wall of the eye. The photoreceptor nerve cells of the retina, change the light rays into electrical impulses and send them through the optic nerve to the brain, where an image is formed. The centre of the retina is called the macula. This is responsible for sharp vision for reading. The peripheral retina is responsible for peripheral of vision.
Indeed eyes are the best gift of God. We are not aware of its importance, as long as our vision is perfect. Out of the five senses like sight, hearing, touch, taste and smell, the loss of sight is the worst one can ever suffer. It is because of this Helen Keller said, “Of all the senses sight must be the most delightful.”
Answer:
The Tipler cylinder is a cylinder of dense matter and infinite length. Historically, Dutch mathematician Willem Jacob van Stockum (1910–1944) found Tipler cylinder solutions to Einstein’s equations of general relativity in 1924. Hungarian mathematician/physicist Cornel Lanczos (1893–1974) found similar Tipler cylinder solutions in 1936. Unfortunately, neither Stockum nor Lanczos made any observations that their solutions implied closed timelike curves (i.e., time travel to the past).
In 1974, American mathematical physicist/cosmologist Frank Tipler’s analysis of the above solutions uncovered that a massive cylinder of infinite length spinning at high speed around its long axis could enable time travel. Essentially, if you walk around the cylinder in a spiral path in one direction, you can move back in time, and if you walk in the opposite direction, you can move forward in time. This solution to Einstein’s equations of general relativity is known as the Tipler cylinder. The Tipler cylinder is not a practical time machine, since it needs to be infinitely long. Tipler suggests that a finite cylinder may accomplish the same effect if its speed of rotation increases significantly. However, the practicality of building a Tipler cylinder was discredited by Stephen Hawking, who provided a mathematical proof that according to general relativity it is impossible to build a time machine in any finite region that contains no exotic matter with negative energy. The Tipler cylinder does not involve any negative energy. Tipler’s original solution involved a cylinder of infinite length, which is easier to analyze mathematically, and although Tipler suggested that a finite cylinder might produce closed timelike curves if the rotation rate were fast enough, Hawking’s proof appears to rule this out. According to Hawking, “it can’t be done with positive energy density everywhere! I can prove that to build a finite time machine, you need negative energy.”
One caveat, Hawking’s proof appears in his 1992 paper on the “chronology protection conjecture,” which has come under serious criticism by numerous physicists. Their main objection to the Hawking’s conjecture is that he did not employ quantum gravity to make his case. On the other hand, Hawking and others have not been able to develop a widely accepted theory of quantum gravity. Hawking did just about the only thing he could do under the circumstances. He used Einstein’s formulation of gravity as found in the general theory of relativity. Another fact, Hawking’s proof regarding the Tipler cylinder is somewhat divorced from the main aspects of his paper and could be viewed to stand on its own. However, in science we are always judged by the weakest link in our theory. Thus, with a broad brush, the chronology protection conjecture has been discredited, and even Hawking has acknowledged some of its short comings.