In a pickle about spectra?

After seeing a tweet by Jim Wild (who tweets here), I found out about the ‘electric pickle’ teaching method. Astronomers talk about spectra a lot – how everything emits light with a fingerprint of colours assigned to them – but it is sometimes hard for people to conceptualise how, for example, sodium in one state is going to react the same way to sodium in another.

The lecturer in the following clip has already taught his students the mathematics of why this is so, but he has tacked on a little practical demonstration. He begins with sodium lights, showing the familiar yellow glow of a neglected town, moves on to spray salt water into the flame of a blow torch, to show that too glows yellow from the thermal energy imparted, then pulls out his pickle.

Dill pickles are notoriously salty and if you pass a current through them, the energy imparted will again cause the sodium to glow the familiar yellow. This is demonstrated here:

This one is brighter, but a little less scientific:


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