Well, it’s very hard for me to live up to the excitement of the last 2 talks, but I’ll do the best I can.
I’m a low temperature physicist.
I study the properties of matter near absolute zero.
Specifically my favourite material which is helium-3.
I decorate my slides with my own photo images.
This is the Golden Gate Bridge, of course.
So, the first question I want to ask is that those discoveries
that most changed the way we think about nature cannot be anticipated.
How then are such discoveries made?
And are there research strategies that can substantially increase the chances of one making such a discovery?
And I will illustrate this with a link chain of discoveries and inventions that occurred quite a long time ago,
starting with one of my great heroes Heike Kamerlingh Onnes who was of course the first person to liquefy helium.
But then he tried to...Basically Kamerlingh Onnes was in a competition with Dewar to see
who could first liquefy the lightest and most inert of the atmospheric gases.
And after liquefying helium Kamerlingh Onnes pumped on the vapour above the liquid
in order to see what temperature helium solidified.
This is exactly what Dewar had done with hydrogen.
Unfortunately, helium does not solidify under its own vapour pressure at any temperature, even absolute zero.
So in fact he eventually became frustrated about this and then looked around for some other interesting question of the day
that he could answer with this remarkable refrigeration device that he had made.
It was very complicated.
So he got...There was an argument about what would happen to the electrical conductivity of metals
if one could cool them to absolute zero.
One argument was that if you had very pure metal and you cooled it you would eliminate the lattice vibrations
which scattered the conduction electrons.
And so the electrical resistance would slowly drop towards zero.
But the other school of thought suggested that as you cool it down at some temperature the conduction electrons
which were free to roam around the interior of the metal would re-condense on the ions from which they’d come
and all electrical conductivity would cease.
So Kamerlingh Onnes got a very pure sample of mercury, of metal which is particularly easy to purify
and gave it to Gilles Holst, his associate.
And Gilles Holst basically measured the electrical resistance.
So here you can see that the measurements of the electrical resistance...
This is the resistance at 2,000’s of an ohm, this is 4.2 Kelvin, this is 4 Kelvin.
And you can see the electrical resistance is dropping slowly towards zero.
But then at a temperature slightly above 4.2 Kelvin there was a discontinuous drop in the electrical resistance to a value
which was less than 10^-5 ohms which is the resolution of their instrument.
Now I believe that Kamerlingh Onnes was incredulous, felt that surely an electrical lead had fallen off the sample at this point.
But of course that wasn’t the case.
This was the first observation of super conductivity.
So let’s look at the relevant research strategies that allowed this discovery to be made.
First use the best instrumentation available.
Now I must say that in fact this very complex set of refrigeration processes that Kamerlingh Onnes had developed was unique
and it really allowed you to reach lower temperatures than anyone else could see.
Don’t reinvent, borrow the technologies you can.
Now Dewar and Kamerlingh Onnes were in a rather, nearly bitter competition to see who could win this race.
Dewar had invented the Dewar flask in order to allow him to do that.
Kamerlingh Onnes was very happy to borrow that technology even though these 2 were rather bitter rivals.
Look into an unexplored region of the physical landscape.
In this case, we’re looking at the properties of matter at temperatures that had never been reached before.
And so after liquefying helium Kamerlingh Onnes did exactly what Dewar had done with hydrogen.
Dewar had pumped on the vapour above the hydrogen in order to cool it further and find out where hydrogen solidified.
Dewar tried that with liquid helium.
And for quite some time he tried that.
However, liquid helium does not solidify under its own vapour pressure.
So then he thought about what other big questions of the day he could answer with this refrigeration process that he’d developed.
And so I would say failure might be an invitation to try something new.
That’s exactly what Kamerlingh Onnes did.
And I should add:
Be aware of subtle unexplained behaviour.
Don’t dismiss it.
Now, Kamerlingh Onnes had written in his log book that it appeared
that the liquid helium stopped boiling at a temperature of about 2 Kelvin.
That of course was due to the onset of superfluidity in helium 4, which of course has been a subject of study for many years.
So this is one of my other great heroes, I suppose, Pyotr Kapitsa
who shared the Nobel Prize in 1978 for measuring the viscosity of superfluid helium in the winter of 1937 in Moscow.
I suppose that you can say that’s not fair because Kapitsa started at a lower temperature.
That is his lower temperature outside.
But in fact, so Kapitsa really was the person that first observed superfluidity in helium.
But he shared the Nobel Prize with 2 very unlikely colleagues whose work had absolutely nothing to do with his own
and these were Arno Penzias...
When I was at Bell Laboratories Arno was my boss’s boss’s boss.
And Robert Wilson.
So these 2 people, of course, their work had nothing to do with low temperature physics.
But rather the discovery of the cosmic microwave background radiation.
So Penzias had convinced AT&T to allow them, that is Penzias and Wilson,
to use this very elegant piece of high tech machinery to look at the radiation coming in from outer space.
This was a horn antenna which has the advantage that it doesn’t couple to radiation coming from the ground.
It was actually developed by AT&T in order to test the feasibility of satellite telecommunications.
And the key is not this horn antenna but inside this little shed here was one of the quietest receivers of its day.
It was based on the development of the maser by Charles Townes shown here.
This is actually Ammonia Maser 2.
But this in fact, technology would not have allowed Penzias and Wilson to do what they wanted to do.
In fact, it was up to Nicholas Blumbergen to actually modify the maser
so that in fact it basically was a doped ruby rode that could be cooled to a temperature of 4.2 Kelvin.
And in fact, that provided the most sensitive radio receiver of its day.
So here’s some of the early evidence back in those days.
And I dare say this was also true when I was a graduate student that data all came out on a strip chart recorder.
And I don’t know if I have to explain what a strip chart recorder is
but a piece of paper is pulled underneath a pen which moves back and forth.
So anyway, he’s looking here.
Actually the signal is going up this way, time is going this way.
And so he’s looking at the signal coming in from the antenna.
And then he as a microwave switch.
He switches to a cold load which is basically a black body cooled to 4.2 Kelvin and compares the noise figures.
And in the end they decided that there was extra noise at the level of about 3.3 Kelvin that they couldn’t understand.
So they went back and they actually climbed up inside the antenna.
And what they found was that the pigeons had been roosting inside the antenna.
So always check your equipment before you start doing an experiment, especially for pigeon nests.
So they knocked down the pigeon nests and I think a few of the copper plates inside this antenna were corroded
and had to be replaced.
But virtually nothing that they could do would eliminate this extra noise.
And of course we now know that this noise is intrinsic.
It is the cosmic microwave background radiation.
So let’s look at the relevant research strategies.
Use the best technology available.
In this case, Penzias and Wilson were lucky enough to be able to borrow probably the best receiver of its day.
Don’t reinvent the wheel, borrow if possible.
And they did that.
Look into a region of parameter space that is unexplored.
They were the first people to make absolute radio noise measurements...
of the radio noise coming from outer space.
And then finally and I think this is very important for any researcher.
Understand what your instrumentation is measuring.
It would be very easy for Penzias and Wilson to say “Well, there’s a little bit of extra noise here.”
and just dismiss that and redefine the base line of their instrument.
But they didn’t do that.
So this is of course...This was from the COBE satellite.
It shows the intensity of that radiation as a function of wavelength
and the temperature is 2.725 Kelvin with a resolution of 1,000th of a degree.
Pretty impressive measurement.
But if you look at the distribution of the intensity of that radiation as a function of position in the sky, what you find...
Well first of all, because of the velocity of the earth, you see a Doppler shift.
It’s hotter in one direction and colder in the other direction.
Hotter in the direction the earth is going.
And you can get rid of this easily.
And then you see the plain of the Milky Way Galaxy which is also possible to get rid of this.
This is really something that you don’t see except for long wavelengths because of dust scattering.
And so once you get rid of this you’re left still with these fluctuations.
And these fluctuations are relatively reproducible
which suggests in fact it’s not some air in the equipment or anything like that.
In any event it eventually became very clear that what they were looking at was the cosmic microwave background radiation.
And for their work John Mather and George Smoot shared the 2006 Nobel Prize for physics,
for their discovery of the black body form and anisotropy of the cosmic microwave background radiation.
So, I don’t know how these guys felt when they made their discovery but it is, for me it’s always been, very exciting.
Now I’m shifting gears again.
This is a bit of the Iguaçu Falls.
I’m an avid photographer.
I like to decorate my images as I said before.
So, the process of advancing science often leads to inventions and technologies that may benefit mankind.
However, it is often impossible to know from where a particular advance might come that could benefit mankind.
Consider for example nuclear magnetic resonance.
And we heard already today 2 beautiful talks on nuclear magnetic resonance
which is in fact one of my favourite probes for probing nature.
NMR was invented in 1946, one year after the end of world war 2, by these gentlemen here,
Felix Bloch at Stanford University and Ed Purcell at Harvard University.
And supposedly when they get the Nobel Prize just 7 years later, I know exactly what happens.
The press come up and they ask you to explain what it is that you’ve discovered.
And you say you’re processing nuclear spins in a magnetic field and things like that.
And after a while the press will get impatient and they will say:
“Just tell me what NMR might be good for”.
And so supposedly, I have not seen this written down but I’ve talked to plenty of people at Harvard and Stanford,
Felix Bloch, who was a bit of a curmudgeon, suggested in fact that NMR was good for damn little.
That is to say he had invented it for a specific purpose and didn’t envision other applications.
Ed Purcell was kind of, somewhat of a more patient and kinder, gentler man I suspect.
I knew Ed Purcell well.
I didn’t know Felix Bloch.
He’d died by the time I got to Stanford.
But in fact Ed Purcell had suggested that perhaps one could use nuclear magnetic resonance to calibrate magnetic fields.
Now, let’s see what in fact the visionaries that invented NMR hadn’t considered.
So it didn’t take that long for people to actually produce very homogenous magnetic fields.
And when they looked at the protons in organic solvent, they found, in fact,
that the protons didn’t all resonate at the same frequency.
There were the triplets and quadruplets.
And these things were typically shifted by several parts per million.
And it became clear very quickly, in fact, that these shifts were a result of the molecular bond lengths
and interactions between the nuclear magnetic moments.
So the next big step was really made by Richard Ernst.
Now, you’ve heard his talk and I’m very reluctant to talk about something that I wasn’t involved in.
But this was a spectacular development in NMR.
Richard Ernst, who is Swiss of course, was working at varying associates in Palo Alto
which is where Stanford University is located.
And he invented pulsed NMR which allowed you to apply a very strong, very short pulse of radio frequency field.
And in fact that would tip the nuclear spins by whatever angle you wanted.
And then they would process and you could then get the frequency of procession very accurately.
So, this is basically what's called 2 dimensional NMR.
And it really allows you to determine the nature of these bonds.
It can’t give you the structure very accurately but in fact, this was in fact, a remarkable advance.
And so, for his contributions to NMR, Richard Ernst shared the Nobel Prize in chemistry in 1991.
Now, the first Nobel Prize for the development of NMR in the first place was in physics.
Now, Richard Ernst was working in Switzerland with another colleague, Kurt Wüthrich who is here as well.
And Kurt Wüthrich did not share the Nobel Prize with Richard Ernst.
And I don’t know if I should say this or not but I think he was a bit unhappy, shall we say,
that he didn’t share the Nobel Prize because these 2 had worked very closely together.
But Kurt Wüthrich then continued on his own and eventually developed a very complex pulse sequences which allows anyone
that has the equipment to determine the confirmation, even of complicated molecules such as proteins as shown here.
So, here’s Kurt Wüthrich receiving his Nobel Prize.
Now, the prize given to Richard Ernst was in 1991 so this is 11 years later.
Kurt Wüthrich got his own Nobel Prize.
My wife doesn’t like it but if you look very carefully you’ll see that he’s smiling.
Everyone smiles at this moment in their lives.
But I should say that in fact NMR development continued.
And eventually people realised and I dare say I think I was one of the first people
that applied a magnetic field gradient to a sample that I wished to study with NMR.
And then each nuclear spin, the position of each nuclear spin
is tagged by the frequency shift from the applied magnetic field gradient.
So this is a very healthy human knee.
You can see the medial meniscus is in very good shape.
I’m afraid my knee now is made out of titanium and so you probably can’t do this measurement.
But for the development of MRI as it’s called,
Paul Lauterbur and Peter Mansfield shared the Nobel Prize not in physics or chemistry but in physiology or medicine in 2003.
Now it’s kind of amazing because this in fact was the fourth Nobel Prize given for developments in NMR.
And it was the third different discipline that the Nobel Prize was given.
And so you have physics, chemistry, physiology or medicine.
Quite a remarkable and extremely valuable tool.
Ok, now I’m going to really shift gears and talk about my discovery.
Because this is really not a talk about a specific kind of physics, but rather about the process of discovery.
So, to begin my life at the beginning of my life, I must report that I was born.
Of course, that’s not my family line...
My father was a medical doctor, my mother had been a nurse but gave up nursing to raise an unruly brood of 5 children.
I was son number 2 right here and I was very interested.
I think, in fact, there was a watershed moment in my life when for Christmas at age 5 I was given an electric train.
And by the end of Christmas day I had torn apart the locomotive to get the electric motor out.
If my parents had said you destructive devil go to bed without your dinner, I suspect I would not be giving this talk today.
So, if you ask me who it was that most influenced the way I think about science,
it was actually none of the professors at Caltech or at Cornell University,
it was this man here, William Hawk, who was my chemistry teacher.
One day he came into class and he had a milk carton, effectively 1 litre.
It was really 1 quart milk carton.
And inside there was something.
And he said: “Research is like trying to find out what's inside the milk carton.
You can do a series of experiments.
And every time you do an experiment you’re asking a question of nature.
Nature has to answer your questions but nature’s answers are a bit vague and difficult to understand.
So then you have to do more experiments, asking more questions
in order to constrain your interpretation of nature’s initial remarks, answers.”
And that’s the way I still think about it.
It’s basically a process where you try to trick nature into giving up her secrets.
And it’s really a fun thing, particularly very late at night that you play with nature.
So after going through high school I went to Caltech as an undergraduate
and that’s when Richard Feynman was teaching all of the undergraduates.
Now, I must say that for people like myself who are really deeply interested in physics this was phenomenal.
And it’s remarkable that such a great physicist was teaching all the undergraduates.
However my freshman class started out at 192 and only 120 returned for their sophomore year.
And I dare say that I think that Richard Feynman had something to do with that.
So bottom line was that only 60% of my freshman class returned for their sophomore year.
So I don’t know whether to thank Richard Feynman.
I should and I have.
In fact, at one point I hosted his visit to Bell Laboratories.
Anyway, after graduating from Caltech I went to Cornell University to do graduate work.
And this is a picture in the fall I guess at Cornell University.
That first semester there were 2 talks given in the physics department describing new refrigeration technologies
that gave the promise of allowing me in particular to look at nature in a new and different realm.
The first was the helium-3/helium-4 dilution refrigerator.
Basically what happens is if you cool helium-3, a mixture of helium-3 and helium-4 down
the helium-3 will phase separate into the top region and you have a mixture of helium-4 with about 6% helium-3 below that.
If you pump on this region, in fact, more helium-3 atoms will diffuse across this phase boundary.
And in the process each one occupies a larger volume.
Which means it has a larger entropy.
That entropy is gained by absorbing heat from the outside.
This is a picture of my helium-3/helium-4 dilution refrigeration that I built as a first year graduate student.
So, this shows the entropy of liquid helium-3.
That line there.
And this is solid helium-3.
In the solid the nuclear spins can point either up or down, that gives you R log 2.
Until a very low temperature where you see nuclear spin ordering.
So the latent heat of solidification then is negative.
Which is very strange.
And this had been proposed by a Russian theorist Isaak Pomeranchuk
and this basically is the technique that I used to reach the temperatures where liquid helium-3 becomes a superfluid.
This is a picture of my Pomeranchuk cell.
And these are the initial data.
So strip chart recorded that the pressure was rising.
Here I rebalanced the capacitance bridge.
The pressure rises.
And then there was this very sharp decrease in the rate of cooling.
Of course, I was very concerned about that and hoped it would go away.
But ultimately this was, in fact, I realised that this was the signature of a jump in the heat capacity in liquid helium-3.
It was the onset of superfluidity in helium-3.
So, here you can see that transition on cooling.
And on warming there was another transition, in fact, a transition between super fluid phases.
So, super fluid helium-3 had ended up being a very rich system for study.
In order to differentiate the liquid from the solid, however, I invented an early form of MRI.
This is back in 1971/’72.
And I know that Paul Lauterbur actually read my paper.
He was one of the architects, real architects of MRI.
So it was kind of fun to be involved in that.
This is a picture of some of the data.
These huge lines are solid.
And this little signal here is the liquid, this is the base line.
And at the temperature of what we call the B-transition, that little blip I showed you in fact,
the liquid NMR signal dropped by a factor of 2.
So I wrote in my lab book that night at 2.40 in the morning, ‘have discovered the BCS transition in liquid helium 3 tonight’.
And then I ran around the basement of the physics building to share this exciting news with people.
Unfortunately, I was the only one in the entire physics building.
So at 2 in the morning, at 2.40, probably about 3 AM actually I called up Dave Lee, my thesis advisor,
who called me back at 6 AM.
He wanted more details.
It was kind of interesting because the phone call I got from Stockholm was at almost exactly the same time.
It was 2.30 in the morning.
I don’t have that but in fact the phone call went:
“Hello, hello.
Is this Douglas Osheroff?” I said:
“Yes, it’s 2.30 in the morning.” I don’t know if that’s what normal people would reply to this.
Of course, I didn’t know what this was all about.
So, here in fact we’ve looked at, it turns out, the high temperature superfluid phase.
It actually shows very large frequency shift.
And here I’ve plotted the frequency in the liquid squared minus frequency in the solid squared and it all collapses on one line.
So in the end here we are getting the Nobel Prize in 1996.
This is yours truly, Dave Lee my thesis advisor and Bob Richardson who really is the person that trained me.
Tony Leggett was the one that explained the shifts in the NMR frequencies.
And so...
What is it?
This is ’96.
7 years later Tony Leggett got his own Nobel Prize which he shared with 2 Russian physicists, Abrikosov and Ginzburg.
So again I put up here this picture of my apparatus and I put in the names of people.
And I won’t name them all or their contributions.
But this was...
Without any one of these names I suspect, I wouldn’t have made this discovery.
So let me end by saying that advances in science are seldom made by individuals alone.
They result from the progress of the scientific community.
Asking questions, developing new technologies to answer those questions
and sharing their results and their understanding with others.
This is how advances in science are made.
Thank you very much.
Applause.