In one of our way-out experiments, we performed CT scans of a 'brown' coconut and did a 3-D reconstruction.

Close examination of the axial of images, showed a superficial (fatty layer (Hounsfield units – 30 ) and the majority of the thickness of the coconut was made of "the meat" of the coconut. Not unexpectedly, there was coconut water in the centre of the image forming a fluid level with air above it (top left).

And then, we started wondering - "How could air have gotten into the coconut ?." It seemed inconceivable that air could have penetrated or permeated into the centre of the coconut through the various layers that cover the coconut both in its raw and ripe stage. We also believed that this quantity of air could not be present even if the air had entered during the stage of the budding and flowering of the coconut tree.

To understand the process that could lead to the presence of air inside the coconut, we performed CT scans of the green coconut (bottom left).

The images of the axial CT scan sections (bottom right) did not show any air – instead the whole coconut was filled with water. It was also obvious that the "meat" of the coconut was very thin compared to that of brown coconut.

There is extensive literature on the process of conversion of the coconut water in the liquid state in the green coconut to that of the meat of the coconut as it matures into the brown coconut.

However, to the best of our knowledge, there is no literature explaining the presence of air inside the brown coconut.

As we believed that there was no way air could have entered through the many layers of the coconut to the depth of its centre, we kept up with our discussions to try and explain this process. And then, it struck us, that this could be vacuum rather than air – the vacuum being left behind as more and water got converted to the meat of the coconut.

The coconut vendors were of no help - even given their native intelligence.

We then set out to prove this hypothesis. We obtained an intact coconut devoid of its hard brown shell (bottom left) and first performed CT scans on it.

As expected, the images bottom right) were no different from that of the coconut with the brown shell. A fluid level with black shadows above and grey shadows below – representing the coconut water – were seen.

We then devised an experiment to prove our hypothesis that it was vacuum and not air in the mature coconut.

We connected a hypodermic needle to a plastic tubing such as the one that is used for intravenous injections and dipped the far end of the tubing into a clear bottle full of colored water.

We hypothesised that if there is any air inside the coconut, when we punctured the full thickness of the shelled out coconut with the hypodermic needle, it would bubble out into the coloured water in the bottle. On the other hand, if it was a vacuum, the coloured water would get sucked into the coconut.

After everything was set up, we punctured the coconut with the hypodermic needle and to our surprise the coloured fluid flowed rapidly from the beaker into the coconut proving thereby that what was indeed seen as air – believed to be air inside the coconut – was indeed a vacuum.

The video of this experiment is available at this link.

And, finally, what is a 'coconut experiment' doing in a website devoted radiology?

A lot! Think this over..

Day after day we read scores of images...dictating reports, making diagnoses.. scarce wondering the...

"whys and hows" of what we see.. exceptions though there may be..

In his seminal article, "Armchair Research and the Practising Radiologist" Benjamin Felson, narrates how - high quality research just needs an inquisitive mind asking the "Hows and Whys'.

I hope the experiment that we have described above motivates more of us to stop and wonder at what we see on the images that we read; and. thus encourage the young radiologists around us to keep digging deeper.

After all, there is so much in medicine that we do not understand and there is always a time to make a beginning.

Conclusion: There is no air in the brown coconut - just water and vacuum!