There's Plenty of Room at the Bottom
An Invitation to Enter a New Field of Physics
by Richard P. Feynman
This transcript of the classic talk that Richard Feynman gaveon December
29th 1959 at the annual meeting of the AmericanPhysical Society at the
CaliforniaInstitute of Technology (Caltech) was first published in the
February1960 issue of Caltech's Engineeringand Science, which owns the
copyright. It has been made availableon the web at
Information on theFeynman Prizes
bamboo是可数名词吗Links to pageson Feynman
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For an account of the talk and how people reacted to it, e chapter4 of
Nano! by Ed Regis, Little/Brown 1995. An excellent technicalintroduction
to nanotechnology is Nanosystems:molecular machinery, manufacturing,
and computation by K. EricDrexler, Wiley 1992.
I imagine experimental physicists must often look with envy at menlike Kamerlingh Onnes, who discovered a field like low temperature, whichems to be bottomless and in which one can go down and down. Such a manis then a leader and has some temporary monopoly in a scientific adventure.Percy Bridgman, in designing a way to obtain higher pressures, opened upanother 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 thesame kind.
I would like to describe a field, in which little has been done, butin which an enormous amount can b
e done in principle. This field is notquite the same as the others in that it will not tell us much of fundamentalphysics (in the n of, ``What are the strange particles?'') but it ismore like solid-state physics in the n that it might tell us much ofgreat interest about the strange phenomena that occur in complex
situations.Furthermore, a point that is most important is that it would have an enormousnumber of technical applications.
What I want to talk about is the problem of manipulating and controllingthings on a small scale.
As soon as I mention this, people tell me about miniaturization, andhow far it has progresd today. They tell me about electric motors thatare the size of the nail on your small finger. And there is a device onthe market, they tell me, by which you can write the Lord's Prayer on thehead of a pin. But that's nothing; that's the most primitive, halting stepin the direction I intend to discuss. It is a staggeringly small worldthat is below. In the year 2000, when they look back at this age, theywill wonder why it was not until the year 1960 that anybody began riouslyto move in this direction.
Why cannot we write the entire 24 volumes of the Encyclopedia Brittanicaon the head of a pin?
Let's e what would be involved. The head of a pin is a sixteenth ofan inch across. If you magnify it by 25,000 diameters, the area of thehead of the pin is then equal to the area of all the pages of the EncyclopaediaBrittanica. Therefore, all it is necessary to do is to reduce in size allthe writing in the Encyclopaedia by 25,000 times. Is that possible? Theresolving power of the eye is about 1/120 of an inch---that is roughlythe diameter of one of the little dots on the fine half-tone reproductionsin the Encyclopaedia. This, when you demagnify it by 25,000 times, is still80 angstroms in diameter---32 atoms across, in an ordinary metal. In otherwords, 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 pinto put all of the Encyclopaedia Brittanica.
Furthermore, it can be read if it is so written. Let's imagine thatit is written in raid letters of metal; that is, where the black is inthe Encyclopedia, we have raid letters of metal that are actually 1/25,000of their ordinary size. How would we read it?
If we had something written in such a way, we could read it using techniquesin common u today. (They will undoubtedly find a better way when we doactually have it written, but to make my point conrvatively I shall justtake techniques we know today.) We would press the metal into a plasticma
terial 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 shadowit by evaporating gold at an angle against the silica so that all the littleletters will appear clearly, dissolve the plastic away from the silicafilm, and then look through it with an electron microscope!
There is no question that if the thing were reduced by 25,000 timesin the form of raid letters on the pin, it would be easy for us to readit today. Furthermore; there is no question that we would find it easyto make copies of the master; we would just need to press the same metalplate 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 techniqueto do this now. But let me argue that it is not as difficult as it firstappears to be. We can rever the lens of the electron microscope inorder to demagnify as well as magnify. A source of
ions, nt through themicroscope lens in rever, could be focud to a very small spot. Wecould write with that spot like we write in a TV cathode ray oscilloscope,by going across in lines, and having an adjustment which determines theamount 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 somephoto 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 throughthe holes; then we could again u our system of lens and make a smallimage 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): Wetake light and, through an optical microscope running backwards, we focusit onto a very small photoelectric screen. Then electrons come away fromthe screen where the light is shining. The electrons are focud downin size by the electron microscope lens to impinge directly upon thesurface of the metal. Will such a beam etch away the metal if it is runlong enough? I don't know. If it doesn't work for a metal surface, it mustbe possible to find some surface with which to coat the original pin sothat, where the electrons bombard, a change is made which we could recognizelater.
There is no intensity problem in the devices---not what you are udto in magnification, where you have to take a few electrons and spreadthem over a bigger and bigger screen; it is just the opposite.
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The lightwhich we get from a page is concentrated onto a very small area so it isvery inten. The few electrons which come from the photoelectric screenare demagnified down to a very tiny area so that, again, they are veryinten. I don't know why this hasn't been done yet!
That's the Encyclopaedia Brittanica on the head of a pin, but let'sconsider all the books in the world. The Library of Congress has approximately9 million volumes; the British Muum Library has 5 million volumes; thereare also 5 million volumes in the National Library in France. Undoubtedlythere are duplications, so let us say that there are some 24 million volumesof interest in the world.
What would happen if I print all this down at the scale we have beendiscussing? How much space would it take? It would take, of cour, thearea of about a million pinheads becau, instead of there being just the24 volumes of the Encyclopaedia, there are 24 million volumes. The millionpinheads can be put in a square of a thousand pins on a side, or an areaof about 3 square yards. That is to say, the silica replica with the paper-thinbacking 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 ofthe information which all of mankind has every recorded in books can becarried around in a pamphlet in your hand---and not written in code, buta simple reproduction of the original pictures, engravings, and everythingel on a small sc
ale without loss of resolution.
班委会What would our librarian at Caltech say, as she runs all over from onebuilding to another, if I tell her that, ten years from now, all of theinformation that she is struggling to keep track of--- 120,000 volumes,stacked from the floor to the ceiling, drawers full of cards, storage roomsfull of the older books---can be kept on just one library card! When theUniversity 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 acopy from the master plate in a few hours and mailing it in an envelopeno bigger or heavier than any other ordinary air mail letter.
Now, the name of this talk is ``There is Plenty of Room at theBottom''---not just ``There is Room at the Bottom.'' What I have demonstratedis that there is room---that you can decrea the size of thingsin 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 possiblein principle---in other words, what is possible according to the laws ofphysics. I am not inventing anti-gravity, which is possible someday onlyif the laws are not what we think. I am telling you what could be doneif the laws are what we think; we are not doing it simply becauwe haven't yet gotten around to it.
Information on a small scale
Suppo that, instead of trying to reproduce the pictures and all the informationdirectly in its prent form, we write only the information content ina code of dots and dashes, or something like that, to reprent the variousletters. Each letter reprents six or ven
特此请假``bits'' of information; thatis, you need only about six or ven dots or dashes for each letter. Now,instead of writing everything, as I did before, on the surface ofthe 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 5times 5 times 5---that is 125 atoms. Perhaps we need a hundred and someodd atoms to make sure that the information is not lost through diffusion,or through some other process.
I have estimated how many letters there are in the Encyclopaedia, andI have assumed that each of my 24 million books is as big as an Encyclopaediavolume, 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 theinformation that man has carefully accumulated in all the books in theworld can be written in this form in a cube of material one two-hundredthof an inch wide--- which is the barest piece of dust that
草字头加以can be made outby the human eye. So there is plenty of room at the bottom! Don'ttell me about microfilm!
This fact---that enormous amounts of information can be carried in anexceedingly 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 forthe organization of a complex creature such as ourlves can be stored.All this information---whether we have brown eyes, or whether we thinkat all, or that in the
甘肃特色embryo the jawbone should first develop with a littlehole in the side so that later a nerve can grow through it---all this informationis contained in a very tiny fraction of the cell in the form of long-chainDNA molecules in which approximately 50 atoms are ud for one bit of informationabout the cell.
Better electron microscopes
If I have written in a code, with 5 times 5 times 5 atoms to a bit, thequestion is: How could I read it today? The electron microscope is notquite good enough, with the greatest care and effort, it can only resolveabout 10 angstroms. I would like to try and impress upon you while I amtalking about all
of the things on a small scale, the importance of improvingthe electron microscope by a hundred times. It is not impossible; it isnot against the laws of diffraction of the electron. The wave length ofthe electron in such a microscope is only 1/20 of an angstrom. So it shouldbe possible to e the individual atoms. What good would it be to e individualatoms distinctly?
We have friends in other fields---in biology, for instance. We physicistsoften look at them and say, ``You know the reason you fellows are makingso little progress?'' (Actually I don't know any field where they are makingmore rapid progress than they are in biology today.) ``You should u moremathematics, like we do.'' They could answer us---but they're polite, soI'll answer for them: ``What you should do in order for us to make more rapid progress is to make the electron microscope 100 timesbetter.''
What are the most central and fundamental problems of biology today?They are questions like: What is the quence of bas in the DNA? Whathappens when you have a mutation? How is the ba order in the DNA connectedto the order of amino acids in the protein? What is the structure of theRNA; is it single-chain or double-chain, and how is it related in its orderof bas to the DNA? What is the organization of the microsomes? How areproteins synthesized? Where does the RNA go? How does it sit? Where dothe proteins sit? Where do the amino acids go in? In photosynthesis,
whereis the chlorophyll; how is it arranged; where are the carotenoids involvedin this thing? What is the system of the conversion of light into chemicalenergy?
It is very easy to answer many of the fundamental biological questions;you just look at the thing! You will e the order of bas in thechain; you will e the structure of the microsome. Unfortunately, theprent microscope es at a scale which is just a bit too crude. Makethe microscope one hundred times more powerful, and many problems of biologywould be made very much easier. I exaggerate, of cour, but the biologistswould surely be very thankful to you---and they would prefer that to thecriticism that they should u more mathematics.guangbo
The theory of chemical process today is bad on theoretical physics.In this n, physics supplies the foundation of chemistry. But chemistryalso has analysis. If you have a strange substance and you want to knowwhat it is, you go through a long and complicated process of chemical analysis.You can analyze almost anything today, so I am a little late with my idea.But if the physicists wanted to, they could also dig under the
