Holography To them, I said, the truth would be literally nothing but the shadows of the images. That is certain. ~ Plato Holography has come a long way since its invention by David Gabor in the late 1940’s. Gabor’s aim was to improve the resolution of the electron microscope, and his research led to the development of electron holography. His premise was: in order to produce a complete holo-spatial image, total information should be used, that is, not just amplitude, but phase as well. The first optical holograms were created following the invention of the laser in 1960. Holography entered the commercial world, and it’s been an uphill climb ever since. You have the obvious applications in imaging, and the not so obvious applications in the medical field, such as design of prosthetic limbs and aiding non-invasive surgery. We see holography being implemented in security and navigation, archival of museum artefacts and design, and a large number of other areas. Holography’s potential for the future is enormous, and we witness applications like holographic memory, quantum computing with holograms, and even the notorious holographic meetings from Star Wars. A laser beam is split into two. One of the beams falls directly onto the photographic plate, and the other is scattered from the object onto the plate. The plate captures the interference pattern between the two. Traditional holography is essentially a way for us to look at a 2-dimensional object, the holographic emulsion and be able to extract spatial information of a 3-dimensional object, which is the object captured by the emulsion. Holography in Terms of Information The beauty of a 3-dimensional object being captured and represented by a 2-dimensional object has triggered an elegant idea in terms of information: the Holographic Principle. Gerard ‘t Hooft, who proposed this principle, said that all information in a region of space can be determined by the information of the surface that contains it. In other words, a higher dimensional entity can be completely described by the information encoded onto its lower dimensional boundary.. Leonard Susskind related this principle to string theory, giving rise to the concept of a holographic universe. It basically implies that we’re living in a higher-dimensional projection with all of the information describing it being painted on a lower-dimensional boundary. We perceive three dimensions, but according to string theory, there are more. Extremities like black holes give rise to inconsistencies between concepts in physics like relativity and quantum mechanics, and the Holographic Principle might be a bridge. Juan Maldacena came up with a rather beautiful idea of gravity that provides a ‘duality’ for physicists to bridge that gap. He said that gravity arises from strings that exist in nine dimensions of space and one dimension of time, a model which would be a hologram projected from a lower-dimensional cosmos without gravity. From the Ancients This outtake on the universe eerily resonates with Plato’s ‘Allegory of a Cave’. Plato was an ancient Greek philosopher who put together a thought experiment to describe how the enlightened philosopher sees the world as compared to the common man. The allegory is as follows: a group of prisoners is chained within a cave, facing the back wall. All they see are shadows fluttering across the wall, produced by the rest of the world moving in front of a fire behind them. To the chained prisoners, the shadows constitute all of reality; they’re all the prisoners know and understand. They name the shadows, and describe them. If one the prisoners were to escape into the world beyond the fire and cave, he’d find that reality is very different than what he earlier believed. The shadows are mere projections of reality. If he were to go back into the cave and describe the world to the chained prisoners, they’d think he was mad! The full text of the Allegory can be found here. Significance of Holography Ideas like Plato’s Allegory and the Holographic Principle actually reflect back to Gabor’s initial motivation: that all available information should be used to produce a complete holo-spatial image. There’s been some debate on whether the universe is holographic or not, but the fact that this debates exists in the first place shows that not only is holography a fun construct to play with in a garage lab on a rainy day, its reach extends far beyond the commercial world to a possible explanation of how our universe ticks. The author of this article is Radha Pyari Sandhir. Here is Radha Pyari Sandhirs bio: PhD Scholar. Slave of physics, soft and quantum computing. Loves fantasy, sci-fi, coffee, Doctor Who and colourful socks. Blogs: mirrorsmusingsandmagic.blogspot catomictheory.wordpress Function Space
Posted on: Tue, 06 Jan 2015 02:27:23 +0000
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