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--------------------- - 1626 - There is Plenty of Room at the Bottom.
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- The Stanford Linear Accelerator, SLAC was built in 1960 at Stanford University campus. I visited the facility several times during 1969 to 1971 when I worked at Hewlett-Packard just a short distance away. The building then was 3,000 meters long. Highway 280 is built over the top of it.
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- HP in Palo Alto was manufacturing test equipment using klystrons and backward wave oscillators. They were used in signal generators and sweep oscillators. The klystrons in this equipment fit in the palm of your hand. The klystrons in SLAC stood as tall as I was. They were spaced along the electron beam path over the mile from the cathode source to the targets.
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- At the end of their run the electron beam is directed into several different targets much like a cathode-ray tube directs an electron beam in an old-fashioned TV. After 50 years of service the linear accelerator has been replaced by the Large Hadron Collider in CERN, Switzerland.
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- The linear accelerator has been converted into an x-ray laser. "Undulators" were installed in place of the klystrons in the SLAC tunnel. The undulators consists of a series of magnets that generate alternating magnetic fields. When electrons move through the undulating fields they wiggle and emit x-rays. The system is called a Linac Coherent Light Source.
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- Synchrotrons are closed loops that follow a curved path as the electron beam is bent around the racetrack. SLAC accelerator is a straight line. The undulator is 130 meters long. Electrons and photons travel the same path at nearly the same speed; however, the photons are continually sideswiping the electrons. This subatomic demolition derby causes electrons to emit x-rays. If everything is lined up perfectly an extraordinarily bright x-ray beam exits the tube as a free- electron laser.
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- -The peak intensity of the x-ray beam is 10^18 watts per square centimeter. The laser can cut through steel. It's oscillating electromagnetic field is 1,000 times stronger than the fields that hold atoms together.
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- What do you do with this high power beam?
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- Say we focus it on a neon molecule:
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- The illuminated matter reaches a temperature over 1,000,000 Kelvin in less than 1 trillionth of a second. The neon atom loses all 10 of its electrons. The electrons surround the nucleus of an atom in onion-like orbital shells. The outer shells are nearly transparent to x-rays. The inner shells take the brunt of the radiation. The electrons shoot off and the atom becomes hollow for a few femtoseconds ( 10^-15 seconds). Electron's quickly get sucked up to fill the holes.
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- In solids this state is called a “ plasma”. The stuff of the Big Bang, supernovae, and neutron stars. Acting as a kind of strobe light. The laser has frozen the motion of atoms, capturing high speed images of proteins and viruses, and recording physical and chemical transformations that take less than a trillionth of a second.
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- Conventional lasers have wavelengths 1,000 times longer and cannot resolve individual atoms. Just as radar can see a rainstorm that cannot resolve the raindrops. Because the light is so short and bright it can capture the image faster than the molecule can blow itself up. Although the laser obliterates the molecule it captures a clear image first.
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- Recent work has mapped out the structure of proteins involved in sleeping sickness, a fatal disease caused by protozoan parasites.
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- Improvements in designs continue. With pulses as short as 0.1 femtoseconds physicists hope to observe not just atoms , but electrons within atoms. Atoms may even be manipulated to create new molecules. Videos may be created that show how chemical bonds break and new ones form.
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- This was all predicted by Richard Feynman in his famous lecture “There is plenty of room at the bottom“. Feynman was challenged with the notion that “you could write the Lord's prayer on the head of a pin“.
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- He replied that you can write 24 volumes of the Encyclopedia Britannica on the head of a pin.
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- The head of a pin is one 16th of an inch. If you can magnify it by 25,000 diameters all the pages of the 24 volumes would fit. Therefore all we need to do is to reduce the size of the writing by 25,000. The resolving power of the eye is 1/20 of an inch. So the little dots in a halftone photo need to be magnified to 8 nanometers, 32 atomwidths across. One dot would contain 1,000 atoms. 24 volumes would easily fit on the head of a pin.
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- The Library of Congress holds 9,000,000 volumes. The whole world holds 24,000,000 volumes of interest. You would need 1,000,000 pinheads to hold all the world's literature. That is the area of 3 square yards , the size of 35 pages. A typical library could be carried around on one library card.
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- “There is plenty of room at the bottom”.
- Each letter in the alphabet can be coded in seven bits. Now we can use dots and dashes, ones and zeros, to go in 3 dimensions, not just 2. We need a cube about 5x5x5 = 125 atoms. Even allowing 100 atoms per bit all the books in the world could be written in a cube that is 0.027 inches wide. That is the size of dust that the eye can barely see.
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- Physicist struggle with these dimensions. This small world seems so incomprehensible. Biologists are used to it however. Biologists work with DNA that contains all the information to construct a human being. Life evolves from a single cell. Somehow all the information needed is coded inside that first cell. A sperm and egg exchange DNA that splits from cell to cell and constructs a brain, eyeballs, the nervous system to the fingers and toes, the personality in a body that is perfectly proportioned and beautiful. A mystery that has been studied since beginning of time starts with the smallest information at the bottom.
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- A long chain of DNA molecules uses 50 atoms for each bit of information.
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- Feynman's challenge in his lectures was to develop an electron microscope that has 100 times more resolving power. Today's microscope can resolve to one nanometer. An electron’s wavelength is 1/200 of a nanometer. So, it should be possible to see individual atoms.
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- If we could arrange atoms one by one in the way we want. How small could we make computers? Could machines be made to put in the bloodstream and perform surgery from inside the body? Could physicists synthesize any chemical substance that chemists could dream up?
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Stanford University's x-ray laser is the reality coming out of Feynman's predictions. An announcement will be made shortly, stay tuned.
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