1959年在加州理工学院的物理年会上所作。 非常欣赏费曼这个人，这篇演讲中他对纳米技术的许多预言在今天都变成了现实。
There's Plenty of Room at the Bottom
An Invitation to Enter a New Field of Physics
by Richard P. Feynman
I imagine experimental physicists must often look with envy at men like Kamerlingh Onnes, who discovered a field like low temperature, which ems to be bottomless and in which one can go down and down. Such a man is then a leader and has some temporary monopoly in a scientific adventure. Percy Bridgman, in designing a way to obtain higher pressures, opened up another new field and was able to move into it and to lead us all along. The development of ever higher vacuum was a continuing development of the same kind. I would like to describe a field, in which little has been done, but in which an enormous amount can be done in principle. This field is not quite the same as the others in that it will not tell us much of fundamental physics (in the n of, ``What are the strange particles?'') but it is more like solid-state physics in the n that it might tell us much of great interest about the strange phenomena that occur in complex situations. Furthermore, a point th
at is most important is that it would have an enormous number of technical applications.
What I want to talk about is the problem of manipulating and controlling things on a small scale. 文具盒里的故事
As soon as I mention this, people tell me about miniaturization, and how far it has progresd today. They tell me about electric motors that are the size of the nail on your small finger. And there is a device on the market, they tell me, by which you can write the Lord's Prayer on the head of a pin. But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began riously to move in this direction.
Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin?
Let's e what would be involved. The head of a pin is a sixteenth of an inch across. If you magnify it by 25,000 diameters, the area of the head of the pin is then equal to the area of all the pages of the Encyclopaedia Brittanica. Therefore, all it is necessary to do is to reduce in size all
the writing in the Encyclopaedia by 25,000 times. Is that possible? The resolving power of the eye is about 1/120 of an inch---that is roughly the diameter of one of the little dots on the fine half-tone repr
oductions in the Encyclopaedia. This, when you demagnify it by 25,000 times, is still 80 angstroms in diameter---32 atoms across, in an ordinary metal. In other words, one of tho dots still would contain in its area 1,000 atoms. So, each dot can easily be adjusted in size as required by the photoengraving, and there is
no question that there is enough room on the head of a pin to put all of the Encyclopaedia Brittanica.
Furthermore, it can be read if it is so written. Let's imagine that it is written in raid letters of metal; that is, where the black is in the Encyclopedia, we have raid letters of metal that are actually 1/25,000 of their ordinary size. How would we read it?
If we had something written in such a way, we could read it using techniques in common u today. (They will undoubtedly find a better way when we do actually have it written, but to make my point conrvatively I shall just take techniques we know today.) We would press the metal into a plastic material and make a mold of it, then peel the plastic off very carefully, evaporate silica into the plastic to get a very thin film, then shadow it by evaporating gold at an angle against the silica so that all the little letters will appear clearly, dissolve the plastic away from the silica film, and then look through it with an electron microscope!
There is no question that if the thing were reduced by 25,000 times in the form of raid letters on the pin, it would be easy for us to read it today. Furthermore; there is no question that we would find it easy to make copies of the master; we would just need to press the same metal plate again into plastic and we would have another copy.
How do we write small?
The next question is: How do we write it? We have no standard technique to do this now. But let me argue that it is not as difficult as it first appears to be. We can rever the lens of the electron microscope in order to demagnify as well as magnify. A source of ions, nt through the microscope lens in rever, could be focud to a very small spot. We could write with that spot like we write in a TV cathode ray oscilloscope, by going across in lines, and having an adjustment which determines the amount of material which is going to be deposited as we scan in lines.
This method might be very slow becau of space charge limitations. There will be more rapid methods. We could first make, perhaps by some photo process, a screen which has holes in it in the form of the letters. Then we would strike an arc behind the holes and draw metallic ions through the holes; then we could again u our system of lens and make a small image in the form of ions, which would deposit the metal on the pin.
A simpler way might be this (though I am not sure it would work): We take light and, through an optical microscope running backwards, we focus it onto a very small photoelectric screen. Then electrons come away from the screen where the light is shining. The electrons are focud down in size by the electron microscope lens to impinge directly upon the surface of the metal. Will such a beam etch away the metal if it is run long enough? I don't know. If it doesn't work for a metal surface, it must be possible to find some surface with which to coat the original pin so that周末愉快短句
, where the electrons bombard, a change is made which we could recognize later.
There is no intensity problem in the devices---not what you are ud to in magnification, where you have to take a few electrons and spread them over a bigger and bigger screen; it is just the opposite. The light which we get from a page is concentrated onto a very small area so it is very
inten. The few electrons which come from the photoelectric screen are demagnified down to a very tiny area so that, again, they are very inten. I don't know why this hasn't been done yet! 四面八方什么意思
因循守旧的意思That's the Encyclopaedia Brittanica on the head of a pin, but let's consider all the books in the world. The Library of Congress has approximately 9 million volumes; the British Muum Library has 5 million volumes; there are also 5 million volumes in the National Library in France. Undoubtedly ther
恐怖故事集e are duplications, so let us say that there are some 24 million volumes of interest in the world.
What would happen if I print all this down at the scale we have been discussing? How much space would it take? It would take, of cour, the area of about a million pinheads becau, instead of there being just the 24 volumes of the Encyclopaedia, there are 24 million volumes. The million pinheads can be put in a square of a thousand pins on a side, or an area of about 3 square yards. That is to say, the silica replica with the paper-thin backing of plastic, with which we have made the copies, with all this information, is on an area of approximately the size of 35 pages of the Encyclopaedia. That is about half as many pages as there are in this magazine. All of the information which all of mankind has every recorded in books can be carried around in a pamphlet in your hand---and not written in code, but a simple reproduction of the original pictures, engravings, and everything el on a small scale without loss of resolution.
What would our librarian at Caltech say, as she runs all over from one building to another, if I tell her that, ten years from now, all of the information that she is struggling to keep track of--- 120,000 volumes, stacked from the floor to the ceiling, drawers full of cards, storage rooms full of the older books---can be kept on just one library card! When the University of Brazil, for example, finds that their library is burned, we can nd them a copy of every book in our library by striking off a copy fro
m the master plate in a few hours and mailing it in an envelope no bigger or heavier than any other ordinary air mail letter.
成语接龙500条Now, the name of this talk is ``There is Plenty of Room at the Bottom''---not just ``There is Room at the Bottom.'' What I have demonstrated is that there is room---that you can decrea the size of things in a practical way. I now want to show that there is plenty of room. I will not now discuss how we are going to do it, but only what is possible in principle---in other words, what is possible according to the laws of physics.
I am not inventing anti-gravity, which is possible someday only if the laws are not what we think. I am telling you what could be done if the laws are what we think; we are not doing it simply becau we haven't yet gotten around to it.
Information on a small scale
Suppo that, instead of trying to reproduce the pictures and all the information directly in its prent form, we write only the information content in a code of dots and dashes, or something like that, to reprent the various letters. Each letter reprents six or ven ``bits'' of information; that is, you need only about six or ven dots or dashes for each letter. Now, instead of writing everything, as I d
id before, on the surface of the head of a pin, I am going to u the interior of the material as well. Let us reprent a dot by a small spot of one metal, the next dash, by an adjacent spot of another metal, and so on. Suppo, to be conrvative, that a bit of information is going to require a little cube of atoms 5 times 5 times 5---that is 125 atoms. Perhaps we need a hundred and some odd atoms to make sure that the information is not lost through diffusion, or through some other process.
紫色胡萝卜I have estimated how many letters there are in the Encyclopaedia, and I have assumed that each of my 24 million books is as big as an Encyclopaedia volume, and have calculated, then, how many bits of information there are (10^15). For each bit I allow 100 atoms. And it turns out that all of the information that man has carefully accumulated in all the books in the world can be written in this form in a cube of material one two-hundredth of an inch wide--- which is the barest piece of dust that can be made out by the human eye. So there is plenty of room at the bottom! Don't tell me about microfilm!
This fact---that enormous amounts of information can be carried in an exceedingly small space---is, of cour, well known to the biologists, and resolves the mystery which existed before we understood all this clearly, of how it could be that, in the tiniest cell, all of the information for the organization of a complex creature such as ourlves can be stored. All this information---whether w
e have brown eyes, or whether we think at all, or that in the embryo the jawbone should first develop with a little hole in the side so that later a nerve can grow through it---all this information is contained in a very tiny fraction of the cell in the form of long-chain DNA molecules in which approximately 50 atoms are ud for one bit of information about the cell. 萝卜焖牛腩
Better electron microscopes
