Understanding Science

“Without physics you can’t see the world”

“You can’t really perceive the world without physics,” says Nobel Prize winner Theodor W. Hänsch.

Physicists face social challenges.

“Quantum physics isn’t that difficult”

I have nothing to do with physics,” many flirt. What do you reply in such cases?

Theodor Hänsch: I’m trying to correct this attitude. Because without physics you can’t really perceive our world. Those who boast that they have no idea about physics document that they don’t want to understand the modern world at all.

For example, what?

For example, the debate about renewable energies. If I have not understood what energy is and how it differs from the installed capacity, I can only have a limited say. Or take the term “power”: In physics, this is something quite different from the power of a poetic word.

In your private circle of acquaintances, you will certainly often be asked questions according to the motto “Theodor, can you explain physics to me? Do you shake the answers out of your sleeve like that?

That is sometimes very difficult. How do I explain the world to someone who doesn’t know anything about simple physical or mathematical terms? If someone doesn’t even know what is meant by integers – where do you start with the explanation? But if there is some basic knowledge, then I see explaining it as an attractive challenge.

Students and former students often give the subject of physics poor marks in surveys. Why?

Perhaps this is the result of a negative selection of teachers. Natural scientists have many career opportunities. Those who nevertheless become teachers may not really like their subject.

In the past decade, there have been plenty of initiatives to get young people interested in natural sciences – in the meantime, they have even started to do so in kindergarten. Will this lead to a turnaround?

I can’t judge that. The young physics graduates we get at our institutes are outstanding. I’m not worried about the next generation of scientists. However, I think it would be good if our MEPs in Parliament also understood a little more about physics.

How much physics does Germany need in order to remain globally successful?

The fact that our economy has recovered so quickly from the global financial crisis is causally linked to the quality of our engineers and scientists.

Does physics need more popularizers from its own ranks? Put simply, does physics need its pop stars?

Surely that would be good for physics. On the other hand, I see a problem: in the community of researchers who concentrate on their scientific problem, one is viewed with suspicion if one too obviously shows oneself to be a popularizer – this is sometimes even regarded as half-silky.


Quite. But at least something is moving. One very successful popularizer, for example, is the Director General of the Deutsches Museum, Wolfgang Heckl, who has held the newly created Oskar von Miller Chair for Science Communication at the TU Munich since 2009. Of course, he can no longer deal as intensively with new physics as he did in his time as a nanophysicist.

If a Germanist wants to deal with quantum physics, what would you advise him to do? Or is that simply impossible?

Quantum physics is not so difficult, it is just not vivid. Those who want to make quantum physics vivid through mechanical models fail. That doesn’t work. Nobody can – not even a physicist. But Anton Zeilinger, quantum physicist in Vienna, has shown that it is still possible to popularise quantum physics. His book “Einstein’s veil: The new world of quantum physics” is also something for Germanists. For teachers and students there is a beautiful booklet “Understanding Quantum Mechanics” by Herbert Pietschmann.


What do you think of populist physical catchwords like quantum teleportation or parallel universes?

Sometimes such buzzwords are embarrassing, but at least they bring physics into conversation. Quantum teleportation is an interesting observable phenomenon, but it has nothing to do with teleportation à la spaceship Enterprise. Other buzzwords, such as parallel universes, describe speculations. As an experimental physicist, I only take theories seriously that can be verified by experiments. Of course you can also speculate. But that’s no more than science fiction.

And your opinion about quantum computers?

I don’t think we’ll ever see quantum computers that are more powerful than conventional computers.

What do you see as the greatest physical advances of recent decades?

For me, the outstanding results in ultracold Bose-Einstein condensation are an absolute must. Then there are the experiments that my successor at the Ludwig Maximilian University in Munich and director at the Max Planck Institute of Quantum Optics in Garching, Immanuel Bloch, is pursuing. His team has succeeded in producing artificial crystals in which quantum mechanical effects can be observed that may also play a role in real solids – for example in high-temperature superconductors.

In natural solids, it has not yet been possible to investigate these effects in a controlled manner. I also pay tribute to those who have succeeded in designing and constructing ultra-short lasers in such a way that conditions are created at their focal point that might have been close to the Big Bang. We have arrived at a pulse length in the dimension of attoseconds. This means that the lasers are pulsed so precisely that they reliably image even a billionth of a billionth of a second.

And what can you do with them?

For example, we can use them to observe the dynamics of electrons in molecules or atoms. Using the frequency comb technique we have developed, we can use lasers to measure time with such extreme precision that the gravitational shift predicted by Einstein can be detected – even if two clocks differ only by ten centimeters in height. We also use the frequency comb technique at the European Southern Observatory to calibrate spectrographs. This improves the search for Earth-like planets in distant stars.

That sounds a lot like sophisticated high-tech equipment. Is this the main difference between modern laboratories and those of your doctoral students?

When I started, we still had to design many of our materials and equipment ourselves – from blowing a glass bulb to a vacuum pump. Today you can order a lot by catalogue. But the real progress is still taking place in people’s minds. Good laboratory equipment can help, but it can also distract. Today, for example, we often spend far too much time reading and understanding operating instructions.

Is there a different approach to basic physical research today than in the past?

Generally speaking, we have much more tools today. The constant electronic availability of literature alone is incredible: I can search world literature for a specific physical problem in no time at all. The tedious and time-consuming communication by letter is also a thing of the past. I write an e-mail and perhaps already in the next moment I have the desired answer. In this way, you can now work together in virtual teams – in other words, discuss and perhaps solve a problem with colleagues who are elsewhere on the globe. Large collaborations such as the European nuclear research centre CERN sometimes consist of worldwide teams of several thousand scientists.

Are you still at the forefront of research?

According to my Nobel Prize, the number of invitations to lectures, panels, prize committees and interviews has risen sharply. That costs time. On the other hand, my new visibility helps me to recruit very good employees. And: If I had not received the Nobel Prize, I would have retired long ago and would no longer be able to work scientifically in Germany.