Earlier this week, I saw the notice pictured above. It was stuck to an office fridge, a casual talking point for those grabbing milk for their tea and coffee.
Now, I reckon there are basically two responses to this. No, actually, there are three - some people will shrug and move on, or ignore it, quite unconcerned about the habits of bananas when exposed to UV. Let’s not worry about them.
The other two responses are basically:
“Wow, bananas glow blue under black lights!”
“Bananas… do they? Really?”
Now, I am firmly in the latter group. I was also, I realised immediately after wondering whether bananas really did glow blue, in the fortunate position of someone who possesses both a banana and a black light (not literally about my person, of course - I had to wait until I got home).
The initial experiment was not terribly promising. This looks very much to me like a peeled banana illuminated by a light with a bit of a purple tinge. There’s definitely nothing I’d describe as “glowing blue”.
I was all ready to give up and add a stroppy post-it to the fridge on Monday saying “no, they don’t” when I realised a couple of things. My UV torch, which is basically a toy for looking at invisible ink, probably isn’t that great. And I’d assumed we were talking about the flesh of the banana - maybe I should have checked the skin as well.
Unfortunately, by this stage, I had made the banana into a milkshake and drunk it. I imagine this sort of problem doesn’t arise in the best scientific establishments.
Fortunately, I had a second banana.
What I didn’t have, though, was much of a grasp of what a banana-yellow object would look like under UV light anyway. How much of the blue-ness of the above picture is down to shining a blue-ish light onto it?
Obviously, this experiment required some form of control object to allow me to tell whether there was something special about the banana.
After some hasty hunting, I lined up three banana-coloured objects. One of them is, of course, a banana. One is part of a vintage 1980s puzzle recently retrieved from a parental attic, the other is the container for a popular brand of milkshake powder (banana-flavoured, as it happens, though the chocolate one also comes in a yellow tub).
Holding the UV torch a little further away seemed to improve things.
However, I still wasn’t really seeing the “glows blue” effect. Everything looks blue, of course, but the banana isn’t noticeably more exciting than the puzzle.
Hang on, though… what’s that?
OK, it’s faint. But that definitely looks like fluorescence to me!
Around the darker, riper spots on the banana skin there are definite glowing rings.
I’m not writing this blog post to demonstrate that ripe bananas fluoresce (other people have already written scientific papers about that), or to flaunt my ownership of fruit and fancy torches.
Instead, I’m advocating for an approach to life. If you put yourself in the group that says “why?” and “really?” and “can I try that?” then you will never be bored. You’ll be better informed, and you’ll have more fun.
Be curious.
Be the person who thinks “well, I’ve got a banana….”.