- Know your apparatus. Don't blindly use a piece of equipment as a black box. Understand how it works. Just because some hand-me-down voltage supply is supposed to put out a square wave doesn't mean that it actually does. You can't blindly use a 10 MOhm input impedance voltage amplifier to measure the voltage dropped across a 1 GOhm load.
- When trying to understand something new, turn every experimental knob as much as you can. You'll be kicking yourself if you decide not to bother cooling the sample below 10 K, and then someone else finds an exciting effect at 9 K. Clearly one needs to strike a balance between time and likelihood of discovery, but in general, if you can tune a parameter, do so.
- Estimate the expected signal size, in real, useful units. Double-check your calculation. My thesis advisor used to tell a story about some students in an advanced undergrad lab who thought their experiment was working well, but it turns out that a wire was actually disconnected, and they'd screwed up the calculation of expected signal size so that the answer agreed with the output of the broken setup.
- Turn knobs finely enough. There are multiple tales out there in physics of discoveries being missed or almost missed because someone was tuning some parameter in coarse steps and skipped over a big feature in the data. That's how superconductivity in MgB2 was missed back in the 1960's, and how SLAC almost didn't co-discover the J/Psi particle.
- Yes, you really do need to reproduce that result. You can see anything once. If the wild, exciting effect you just observed is real, you should be able to see it again if you're careful and diligent.
- Be your own harshest critic. If you won't, the referees surely will.
Tuesday, February 10, 2009
Experimental physics rules to live by?
I thought that it might be fun to have a discussion about "rules to live by" in experimental physics. Here are a few that I think may qualify, and of course I'd appreciate your suggestions for others....
Posted by Douglas Natelson at 10:46 PM