# Photo of Enrico Fermi includes math/physics I do not understand

1. Jun 12, 2013

### JLBRECKENRIDGE

The attached jpeg shows Enrico Fermi at the blackboard.

There is a geometric drawing and some math I do not understand.

Can you point me in the right direction?

I have searched for a discussion of what he is presenting but cannot find one.

The photo may be familiar because it was used by the US Postal Service for a stamp honoring Enrico Fermi on the 100th anniversary of his birth.

Thank you!

#### Attached Files:

• ###### enrico fermi small.jpg
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2. Jun 12, 2013

### ZapperZ

Staff Emeritus
This is an infamous photo of Fermi that had been discussed by many people. There is an error in the equation that was written (presumably by him) on the board.

Zz.

3. Jun 12, 2013

### JLBRECKENRIDGE

Zapper,

Does the geometry relate to some aspect of physics? Perhaps something to do with nuclear physics?

4. Jun 12, 2013

### dipole

Well two problems with the first equation. One, as written it's meaningless - the two operators don't really have a meaning unless they're operating on some state, so the omission of $\Psi$ is somewhat strange to me... second, he's missing a factor of $-\hbar^2$ infront of the momentum operator.

The equation he's written is the time-dependent Schrödinger equation for a Coulomb potential, like that of a hydrogen atom. I don't really know what the diagram he's drawing has to do with it except perhaps depicting a coordinate system.

5. Jun 12, 2013

### JLBRECKENRIDGE

Thank you, dipole and zapper for your responses. Very helpful.

Joseph

6. Jun 12, 2013

### Mute

No, there is no missing factor of $-\hbar^2$. That factor comes from writing the momentum operator out as $p = -i\hbar \nabla$.

7. Jun 12, 2013

### JLBRECKENRIDGE

Mute, do you agree that the other math on the board has no apparent connection to the geometry drawing?

8. Jun 12, 2013

### dipole

Doh, that's true.

9. Jun 13, 2013

### Mute

Without more information it's hard to say for sure. It could be a coordinate system, as dipole suggests; I could imagine it might be a diagram to help illustrate a scattering problem.

He could also just be writing things for a photo op.

10. Jun 13, 2013

### lisab

Staff Emeritus
Go home, Enrico. You're drunk.

11. Jun 13, 2013

### Lavabug

Seriously.

It would be a great stretch to associate the drawing with something about quantum mechanical angular momentum. Maybe that was the idea, but it certainly doesn't look anything like the orthodox representations in most textbooks:

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/imgqua/vecL.gif
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/imgqua/vecL2.gif

12. Jun 13, 2013

### bp_psy

He was just trolling.

13. Jun 14, 2013

### Yanick

He was probably thinking, "This circle/triangle thing will definitely drive someone bonkers in 100 years."

14. Jun 14, 2013

### BobG

He doesn't draw very good circles. It took some strategic posing and some cropping of the frame to get a half decent picture.

15. Jun 14, 2013

### Salman2

This link shows another picture of Fermi, younger in age, with same circle drawing on blackboard, but in this version the circle drawing also is associated with energy equations.

http://photos.aip.org/history/Thumbnails/fermi_enrico_a16.jpg [Broken]

Last edited by a moderator: May 6, 2017
16. Jun 14, 2013

### PhysicsGente

Well, I see a Coulomb potential. So maybe the drawing is a water molecule?

17. Jun 14, 2013

### Staff: Mentor

He is definitely younger on one of these pictures, probably even by several minutes.

Last edited by a moderator: May 6, 2017